How to read compressor maps

[AWDxBOOST]

i figured a thread like this may be helpful to some when choosing a bigger turbo

here is an example of a compressor map
http://www.rbracing-rsr.com/turbo/TurboMaps/t3-60.gif

the idea behind a compressor map is to give you an estimate of how much pressure you would have to run at a certain amount of airflow to meet a horsepower goal (horsepower being measured at the crank)

some basics to start about the maps

Pressure Ratio- given as (Atmospheric pressure+ Manifold Pressure)/(Atmospheric Pressure)

basically if you want to run 20 psi at sea level, you pressure ratio will be

(14.7+20)/14.7= 2.36:1

keep in mind that atmospheric pressure varies by altitude

Air Flow- given in either LB/min or cfm.

10hp=1 lb/min
150cfm= 100hp

Surge Line/Limit- The line farthest to the left, denotes when compressor surge or stalling will occur. basically no air will flow, you want to be to the right of it

Choke Line- The line farthest to the right, after this point there is no further flow rate increase possible. Basically it is the limit of efficiency of the turbo/supercharger

Efficiency Islands- They are denoted on the map itself in percentages and is read like a topographic map of a mountain. For example, on the map above, within the center island the compressor is working at 74% efficiency. In the island around that, it is working at 70% efficiency, and around that, 64% efficiency.

The greater the percentage, the more effiecient the turbo is working. Ideally, you want to be in the highest percentage island, but often compressors are pushed beyond that to make more power.
A 70% efficient compressor means that 70% of the power put INTO the compressor is used to build air pressure. The remaining 30% is used to heat up the air. No compressor is 100% efficient


Now, i think the best way to explain how to use these graphs is by example.

How about i want to make about 250bhp on my legacy with this turbo.

250hp is the goal, so id need to flow 25 lb/min basically.

remember, HPgoal/10= mass flow (lbs/min)

now you also need to know how much boost pressure you are going to have to run at this much power to meet your goal (this varies car by car of course)

lets say we want to run 15psi to achieve this. that equates to a 2.02 pressure ratio

It is now possible to find the spot on the map that the compressor will operate at the instant your engine is at the given (power & boost) operating parameters.

well if you plot the point with x=25lbs/min and y=2.02 then we land in a decent effieciency spot. Basically this turbo would be good for what we are trying to do


The idea is to stay to the right side of the surge line and stay within the highest (average) efficiency islands in the operating range of the engine...

so thats how you decide what turbo is right for your application with a compressor map:icon_mrgr

some other maps for reference so you can see why bigger turbo=bigger power with better efficiency

http://www.rbracing-rsr.com/turbo/TurboMaps/GT35compress.jpg

http://www.rbracing-rsr.com/turbo/TurboMaps/GT60compress.jpg

http://www.rbracing-rsr.com/turbo/TurboMaps/GT12compress.jpg

Warning, the next section is very nerdy and probably not that useful to most

As i said before, a 70% efficient compressor release 30% as heat. How can you figure out the value of this heat? Well I'll tell you

Temperature out = Temperature in + {[Temperature in*(-1+ pressure ratio^0.263)]/efficiency}

Temperature in is the ambient air temperature in Rankine(R) (R= farenheit+460)

Pressure Ratio is the same as i said above:
(Atmospheric pressure+ Manifold Pressure)/(Atmospheric Pressure)

Efficiency is what island of efficiency you are running the compressor at

plug all of this into the formula and voila! you get your temperature out in degree rankine. subtract 460 to get the temperature in farenheit :)

hope this helps someone out there, if anyone has anything to add, feel free and i can add/edit as needed. im no expert after all.

[bosco]

nice job. bosco

[mickeyd2005]

There's also some good info on some DSM sites.

http://www.stealth316.com/2-3s-compflowmaps.htm

It's useful to overlay the engine demand on to the compressor map to see where the boost and rpm should be.

Unfortunately, IHI doesn't seem to like to publish compressor efficiency maps. Only the surge line and choke lines are available. I'm going to assume that the choke line for the IHI turbos are also at 60% efficiency.

[2005garnetGT]

I think you should measure pre-compressor absolute pressure before just assuming its 14.7 psi.

wouldn't want to pick the wrong turbo because you guessed on your inlet pressure, eh?

[AWDxBOOST]

^ right-o, i will make that more clear :)

[edmundu]

Excellent information!

I would like to add that you also have a pressure drop thru the IC which effectively raises the PR seen at the turbo. Generally the better IC's will yield around 1-2psi, whereas a stocker pushed to its limits will be more like 4-6psi.

[rc0032]

HERE (http://members.tripod.com/%7Echerrypicker/id7.html)is some more good info and the map for a 20g

[AWDxBOOST]

added explanation on the efficiency islands

[AWDxBOOST]

added some geeky info on how to estimate the heat put out by the turbo at a certain efficieny range and pressure :lol:

[AWDxBOOST]

HERE (http://members.tripod.com/%7Echerrypicker/id7.html)is some more good info and the map for a 20g

mmm...at 17psi you can run 450bhp and be in the best efficiency island. drivetrain loss at 25%, thats 340whp!!

[rc0032]

mmm...at 17psi you can run 450bhp and be in the best efficiency island. drivetrain loss at 25%, thats 340whp!!
That dosnet add up to what I have seen on a dyno graphs but I will take it :lol:

I typically see 320whp with tq a little higher. Eather way its fun :icon_bigg

[edmundu]

Just because the turbo can flow the required airflow at set psi, doesn't mean the engine can. Hence why you generally need more boost than what a comp map shows.

[Underdog]

Now if we wanted to increase the output of the stock motor from 250chp to maybe 375chp for easy math (and close to 300 whp) we can determine the necessary boost required.

target chp/current chp = 375/250 = 1.5

If we multiply this ratio by the stock boost (13.5 psi) then we determine we will need approximately 21 psi of boost in order to reach our goal.

We can now use the new pressure ratio of (14.7+21)/(14.7) = 2.43 to determine how much flow we must spec. the turbo at.

CFM = ((Displacement(cid) * rpm * .5 * Ve (assume 90% or .9))/1,728) * Pressure ratio = ((150*6500*.5*.90)/1,728) * 2.43 = 617 CFM

So... in order to produce peak boost at redline we need a turbocharger capable of flowing 617 CFM (or ~50 lb/min) at a pressure ratio of 2.43.

Obviously a very simplistic example as it makes no note of losses and is based on only a single parameter (target hp at redline) but hopefully it helps someone.

[AWDxBOOST]

That dosnet add up to what I have seen on a dyno graphs but I will take it :lol:

I typically see 320whp with tq a little higher. Eather way its fun :icon_bigg

haha, i was close

like i said edmundu, its an estimate:lol:

the whole compressor map thing is based on 100% volumetric efficiency, which is not really possible

[mickeyd2005]

The compressor map is just a description of how well the compressor works. It doesn't represent anything that happens at the engine.

It's only when you overlay the engine demand curves onto this curve that the losses at the IC need to be accounted for.

And the engine demand curve really needs to be overlaid to see if boost crosses the surge line or how close to the choke limit the engine can approach. It can also tell you if the turbo is too large.

You can put a HUGE turbo on a little engine and it won't do you any good.

Take a look at this.
http://members.tripod.com/%7Echerrypicker/sitebuildercontent/sitebuilderpictures/td06h-20g-flow.gif

The above is the equivalent of a 1.5 liter (it's actually 1/2 a 3.0 liter) engine load overlaid on a TD06-20G turbo. Even though the turbo is capable of 640 cfm at PR=2, this particular engine will need to spin very fast to get there.

[AWDxBOOST]

^ good info

like i said, the maps are only useful when you have a hp goal and pressure goal in mind for sizing a turbo :)

[rc0032]

I would say they are also good for tunning so you know what boost to target or when you are asking her for too much.

[2005garnetGT]

Now if we wanted to increase the output of the stock motor from 250chp to maybe 375chp for easy math (and close to 300 whp) we can determine the necessary boost required.

target chp/current chp = 375/250 = 1.5

If we multiply this ratio by the stock boost (13.5 psi) then we determine we will need approximately 21 psi of boost in order to reach our goal.

We can now use the new pressure ratio of (14.7+21)/(14.7) = 2.43 to determine how much flow we must spec. the turbo at.

CFM = ((Displacement(cid) * rpm * .5 * Ve (assume 90% or .9))/1,728) * Pressure ratio = ((150*6500*.5*.90)/1,728) * 2.43 = 617 CFM

So... in order to produce peak boost at redline we need a turbocharger capable of flowing 617 CFM (or ~50 lb/min) at a pressure ratio of 2.43.

Obviously a very simplistic example as it makes no note of losses and is based on only a single parameter (target hp at redline) but hopefully it helps someone.

this is way too pessimistic...
the FP green is a 49lb/hr compressor, and greens make a lot more then 300whp.

[Underdog]

It's pessimistic because its for target boost at redline. In practice, we would expect full boost by what? 4000 rpm? So if we substitute 4000 rpm in place of the 6500, you can see we would only need 30.7 lb/min.

Edit: you say lb/hr... I believe it's lb/min.

[biz77]

Now if we wanted to increase the output of the stock motor from 250chp to maybe 375chp for easy math (and close to 300 whp) we can determine the necessary boost required.

target chp/current chp = 375/250 = 1.5

If we multiply this ratio by the stock boost (13.5 psi) then we determine we will need approximately 21 psi of boost in order to reach our goal.

We can now use the new pressure ratio of (14.7+21)/(14.7) = 2.43 to determine how much flow we must spec. the turbo at.

CFM = ((Displacement(cid) * rpm * .5 * Ve (assume 90% or .9))/1,728) * Pressure ratio = ((150*6500*.5*.90)/1,728) * 2.43 = 617 CFM

So... in order to produce peak boost at redline we need a turbocharger capable of flowing 617 CFM (or ~50 lb/min) at a pressure ratio of 2.43.

Obviously a very simplistic example as it makes no note of losses and is based on only a single parameter (target hp at redline) but hopefully it helps someone.

Lots of good info here guys. I really like the formula by Underdog above. Utilize this method for multiple pressure ratios and rpm points and plot on the compressor map to get something that looks similar to the graph posted by Mikeyd. You want to size the turbo so that compressor efficiency is highest in the range you will mostly be driving in.

Also for Pin (inlet pressure) I typically use -.5psig (14.2psia) instead of atmospheric.

[biz77]

CFM to Lbs/Min:

CFM*.069=Lbs/Min

617CFM = 42.5 lbs/min.

This is more along the lines of an 18G turbo and 375CHP sounds reasonable.

[VTGT]

coool

[Underdog]

CFM to Lbs/Min:

CFM*.069=Lbs/Min

617CFM = 42.5 lbs/min.

This is more along the lines of an 18G turbo and 375CHP sounds reasonable.


Thanks for the support.

I was using the conversion of .08 lb/ft^3 for air around 30 degF. In the summer, the specific weight of air would be more likely around the low .07's. .069 would fall somewhere around 110 degF.

Also, it wouldn't be unreasonable to assume 1-2 psi lost due to the intake if you want to be on the conservative side.

I've been meaning to do a thorough write-up but haven't been able to test things like P and V at turbo inlet/outlet, IC inlet/outlet and throttle-body.

[NSFW]

This thread kicks ass. Thanks guys.

[Underdog]

Here is an example I threw together. The attached thumbnail is of an excel spreadsheet I made that allows me to specify what my boost curve will look like. For my purposes (a daily-driver) this may be excessive but I think it offers a good combination of economy and performance. I desire a higher boost output in favor of a low boost-threshold or what many people consider "lag."

That is something that should be cleared up right away.

Lag is the time it take for the turbo to spool up given that there is the necessary airflow to power the turbocharger. A larger turbo has more lag because the compressor wheel is larger (more massive) and generally the A/R ratio is chosen for high-end power. Lag also changes based on RPM, with a large turbo, lag is much greater at say, 2000 rpm, versus 5000 rpm. Things like ball-bearings and tuning your A/R for the desired response will reduce lag but it can never be eliminated!

Boost threshold is the minimum rpm that the turbo is capable of creating boost. Basically, a turbo requires exhaust airflow to spin. At low rpms, there isn't a significant amount of exhaust flow. A turbo with a low boost threshold is designed to operate with small amounts of exhaust gas to power it, whereas a large turbo will not begin to spool until higher RPM's when there is more exhaust gas energy to be had. The small turbo may produce boost quickly but will feel choked at higher rpm since it has already reached maximum operating speed.

Now, with that out of the way.

I desire higher boost-output over boost threshold because a) more boost=more ponies and, b) by having boost build from 2500+ rpm, I have a window of non-boosted engine speed that I can stay in if I'm feeling conservative (thus improving gas mileage :icon_bigg ).

So, I decided that I will break up my rpm-band into three sections (denoted by shading in the table. The boost will begin to build at ~2300rpm and will increase linearly at roughly 2.1psi/250rpm until we reach target boost for the upper third of the engine speed range.

Using the formula I provided:

[(Displacement (in^3) * Engine Speed (rpm) * .5 * .9)/1,728] * [(14.7 + Boost (psi))/14.7] = CFM

We can now determine what the flow demand will be for this particular engine/boost map. Plotting pressure ratio in relation to CFM will give us data points we can plot over a compressor map to see which compressor will handle the demand most efficiently. As you can see, a turbo that could fulfill these requirements would be capable of pushing near 430cHp at redline which would work out to rough 340wHp.

[AWDxBOOST]

^ good stuff right there!

glad to see people chiming in with nice info :)

[2005garnetGT]

yeah, I was thinking of injectors.

but still, look at a green's dyno chart, they make ~400whp at 6500rpms.

heres an example on an 04 sti.

http://i138.photobucket.com/albums/q241/CarQz17/dynograph.jpg (http://i138.photobucket.com/albums/q241/CarQz17/dynograph.jpg)

It's pessimistic because its for target boost at redline. In practice, we would expect full boost by what? 4000 rpm? So if we substitute 4000 rpm in place of the 6500, you can see we would only need 30.7 lb/min.

Edit: you say lb/hr... I believe it's lb/min.

[Underdog]

Thank you AWDxBOOST for putting this thread together!

Below are the AVO380 and 450 compressor maps (420 excluded since its the same compressor as the 380 with a different housing & A/R). As you can see both turbos are capable of producing the desired boost/flow at >70% efficiency (good job AVO folks!). Now, deciding between the 380 & 420 is easy. The 380 has a lower A/R which means it is designed for a lower boost threshold and low/mid rpm grunt. The 420 has a larger A/R ratio which is better suited towards higher-rpm performance.

When it comes down to choosing between the 450 and the 420 is where more ambiguities pop up. To keep some constraints on this project I will specify my goals. A) I want to stay TMIC because it is a part of the Legacy's character. There is nothing that annoys me more than a non-functional hood scoop, and I don't want to swap. B) I'd rather run a larger turbo conservatively then a small one at the fringes of it's performance in order to reduce heat and vibrational stresses on the turbo, but only as long as efficiency isn't sacrificed.

You can see that the plot on the AVO450 is operating within 72% efficiency all the way to max load whereas the 420 efficiency falls off up at the limits. However, since I'm running a TMIC, anything over 40lb/min will probably be pushing the limits of IC efficiency. Therefore I would chose the 450 because the overall efficiency will be better. Actually, if we delayed the boost rise a bit more, we could have the compressor running at optimum efficiency throughout the bulk of the rev range but the difference would be academic.

2005garnetGT: I'm not all to familiar with green turbochargers so if you could point me to some compressor maps, I'd appreciate it. If it can flow 50lb/min and we have all the bolt-ons/supporting mods and an appropriate tune, I don't see why 400whp is out of the question according to my info. Also, I would need to know what the boost map looks like to see the complete picture. Remember, nothing here is gospel, it's merely a tool to be used.

[LittleBlueGT]

Thank you AWDxBOOST for putting this thread together!

Below are the AVO380 and 450 compressor maps (420 excluded since its the same compressor as the 380 with a different housing & A/R). As you can see both turbos are capable of producing the desired boost/flow at >70% efficiency (good job AVO folks!). Now, deciding between the 380 & 420 is easy. The 380 has a lower A/R which means it is designed for a lower boost threshold and low/mid rpm grunt. The 420 has a larger A/R ratio which is better suited towards higher-rpm performance.

When it comes down to choosing between the 450 and the 420 is where more ambiguities pop up. To keep some constraints on this project I will specify my goals. A) I want to stay TMIC because it is a part of the Legacy's character. There is nothing that annoys me more than a non-functional hood scoop, and I don't want to swap. B) I'd rather run a larger turbo conservatively then a small one at the fringes of it's performance in order to reduce heat and vibrational stresses on the turbo, but only as long as efficiency isn't sacrificed.

You can see that the plot on the AVO450 is operating within 72% efficiency all the way to max load whereas the 420 efficiency falls off up at the limits. However, since I'm running a TMIC, anything over 40lb/min will probably be pushing the limits of IC efficiency. Therefore I would chose the 450 because the overall efficiency will be better. Actually, if we delayed the boost rise a bit more, we could have the compressor running at optimum efficiency throughout the bulk of the rev range but the difference would be academic.

2005garnetGT: I'm not all to familiar with green turbochargers so if you could point me to some compressor maps, I'd appreciate it. If it can flow 50lb/min and we have all the bolt-ons/supporting mods and an appropriate tune, I don't see why 400whp is out of the question according to my info. Also, I would need to know what the boost map looks like to see the complete picture. Remember, nothing here is gospel, it's merely a tool to be used.

Bigger turbo will always be more efficient, doesn't mean you should pick it!

AVO420 or bigger IMO should only be used if you have a FMIC or are planning one in the future.

[Underdog]

Bigger turbo will always be more efficient, doesn't mean you should pick it!

AVO420 or bigger IMO should only be used if you have a FMIC or are planning one in the future.


Bigger turbo always more efficient? Hmm, I'm not sure what you're saying here. I don't think many turbos get above 80% efficiency. I don't think I indicated that you should always go with a larger turbo just that the 450 would be my choice over the 420 in the situation I had laid out. Below is an example where the turbocharger is WAY too big for our engine. This turbo will never build boost on our car. Next to it is a turbo that is still way too big but will still build boost, however it is so big that we won't see anything north of 70% efficiency until redline.

Right, anything more than 40lb/min will be choked by the TMIC, which is why the 450 is a better choice. Assuming the same IC efficiency (lets say 70%) the 450 will be (.72x.7= .504) and the 420 will be (.65x.7 = .455) So the 450 would be about 5% more efficient at redline (the point of concern).

[mickeyd2005]

Bigger turbo will always be more efficient, doesn't mean you should pick it!


I disagree with the word always. The peak efficiency on most compressors is around 77% regardless of size. The right size turbo has to be matched to the rpm that the car is driven at.

Underdog's charts are really good at showing that.

[AWDxBOOST]

. Below is an example where the turbocharger is WAY too big for our engine. This turbo will never build boost on our car. Next to it is a turbo that is still way too big but will still build boost, however it is so big that we won't see anything north of 70% efficiency until redline.



LOL at the 1.05 AR turbo

must be for a damn big rig:lol:

[Underdog]

Haha, it is a garrett gt60 turbo capable of supporting 1450-2000 HP on engine from 6.0-12.0 Liters, per the Garrett site.

:lol:

[LittleBlueGT]

I meant a bigger turbo (relatively speaking) is more efficient.

If you are going with a TMIC I think almost everyone will agree that an AVO420 or 380 is by far the best choice.

You will end up with about the same overall hp but less spool. So you are trading spool for essentially nothing (or very little).

[mickeyd2005]

The efficiency shown on the compressor chart is how close the compressor gets to theoretical adiabatic compression. Every compressor wheel has a sweet spot regardless of size. I think you're thinking about something different when you are talking about efficiency.

Also, the compressor maps won't really tell the whole story about spool. For example, if the turbo had a super lightweight titanium or ceramic turbine blades with twin scroll and ball bearings, you'll get better spool but the compressor map really won't change that much. The surge line and choke line should remain the same.

[Underdog]

LBGT, this isn't a thread about me actually choosing a turbo... I have only laid out the graphs and used the AVO information because it was readily available. This is not a judgement on any of their products either, rather a way to interpret compressor maps.

As far as losing spool, we would need to look at the turbine maps in order to see how a turbo will spool in application. The line I plotted on the 380 and 450 graphs is the desired boost profile, but as you can see, these turbos are capable of producing a wide array of flow/pr profiles. The actual boost we see will be determined by the turbine and the boost-control management.

As far as my personal goals... I am no longer afraid to sacrifice a higher boost-threshold (or what you call "spool") for higher boost. The fact is, there are no viable twin-turbo or VNT options out there for the Legacy. Therefore, if you want more horsepower (more boost in the higher rpms) then you MUST sacrifice boost threshold.

The 450 has a larger "sweet spot" that would be where most of my daily driving actually takes place, so right off the bat we are dealing with less heat imparted to the air charge. The reason "everyone here" thinks that the 450 should only be used with FMIC is because the thought is that if you're getting a 450, you must want big numbers. If I was shooting for 24psi or much over 400cHp then I would certainly go the FMIC route.

Lastly, you shouldn't downplay the efficiency of the turbo. The 5% gain in efficiency will be akin to the slightly increased boost threshold, they are both small trade-offs. I could say that by going with the 380 (not even a consideration for me) you are trading efficiency for essentially nothing (or very little) because to me, if I want to drive fast/aggressive, I'll keep it in the powerband... not roll on from 1,500rpm. The rest of the time, I'll be happy with the non-boosted 2.5 for getting me to Dunkin' Donuts and back.

Aside: Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

[LittleBlueGT]

LBGT, this isn't a thread about me actually choosing a turbo... I have only laid out the graphs and used the AVO information because it was readily available. This is not a judgement on any of their products either, rather a way to interpret compressor maps.

As far as losing spool, we would need to look at the turbine maps in order to see how a turbo will spool in application. The line I plotted on the 380 and 450 graphs is the desired boost profile, but as you can see, these turbos are capable of producing a wide array of flow/pr profiles. The actual boost we see will be determined by the turbine and the boost-control management.

As far as my personal goals... I am no longer afraid to sacrifice a higher boost-threshold (or what you call "spool") for higher boost. The fact is, there are no viable twin-turbo or VNT options out there for the Legacy. Therefore, if you want more horsepower (more boost in the higher rpms) then you MUST sacrifice boost threshold.

The 450 has a larger "sweet spot" that would be where most of my daily driving actually takes place, so right off the bat we are dealing with less heat imparted to the air charge. The reason "everyone here" thinks that the 450 should only be used with FMIC is because the thought is that if you're getting a 450, you must want big numbers. If I was shooting for 24psi or much over 400cHp then I would certainly go the FMIC route.

Lastly, you shouldn't downplay the efficiency of the turbo. The 5% gain in efficiency will be akin to the slightly increased boost threshold, they are both small trade-offs. I could say that by going with the 380 (not even a consideration for me) you are trading efficiency for essentially nothing (or very little) because to me, if I want to drive fast/aggressive, I'll keep it in the powerband... not roll on from 1,500rpm. The rest of the time, I'll be happy with the non-boosted 2.5 for getting me to Dunkin' Donuts and back.

Aside: Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

I understand exactly what you are saying.

It just seems extremely odd to me that you would consider using a turbo like a 450 w/ a TMIC when the 380 is actually considered a farily efficient turbo when talking about hp in the 380-400 crankhp range.

It just seems like the trade-offs are not very even. In other words it does not seem like a matched system.

[Underdog]

I'm not considering using any other turbo besides the vf40 for the next ~5 years or 60k miles.. :)

I wasn't saying that the 450 is the right turbo because we haven't looked at the turbine side at all. The AVO450 is a product, the compressor is merely a component. While the component may be what we are looking for (in that situation it would be) the product may not be right for our uses.

One last time: I'm not advocating one turbo or another for specific application. Just trying to inform people how to read the maps and to understand what the information means.

[edmundu]

....Am I the only one here who loves the feeling of a turbo spooling up? I don't understand why some people shy away from higher boost thresholds. Granted, you can take it too far where the car won't ever hit boost unless you are on the fringes of legality. But most of the time, feeling the torque as the boost builds just gives me such a rush... I wish the vf40 didn't fall on its face at the top-end!

:whore:..I agree!!! I love the spoolup of the Avo450, it is not the punchy feeling of a vfxx, but a build up/swell of power that doesn't letup til redline. Very, very sweet. Although not for everyone, it suits me just fine:)

[Underdog]

^ Thanks for chiming in! :)

Besides the lack of top end, the other thing I don't like about the vf40 is that "punchiness." It upsets the car's low-speed/cruising balance and makes throttle application "jerky."

In the words of Corky Bell: "If you have no lag, you have no turbo. You also have no huge torque increase to look forward to."

[rc0032]

I understand exactly what you are saying.

It just seems extremely odd to me that you would consider using a turbo like a 450 w/ a TMIC when the 380 is actually considered a farily efficient turbo when talking about hp in the 380-400 crankhp range.

It just seems like the trade-offs are not very even. In other words it does not seem like a matched system.
http://www.northamericanmotoring.com/forums/images/smilies/sly.gif

[Underdog]

^ Yeah, I'm confused too... I'm sure LBGT will be happy with the AVO380 w/ meth. I had absolutely no intent on undermining that. He simply has different goals for his car than I do. I mean, if I was bashing an AVO product for design, why would I "consider" another AVO product?

The only reason AVO was mentioned is because they are particularly helpful and informative when it comes to their product. (.pdf's)

[rc0032]

He would be happier if he gotten injectors :hide:

To each their own, I think he is just justifying heis purchase. A few months back he was insistent that the 420 needed a FMIC and WI was the devil.

Now get this thread back on topic…

[Underdog]

Here is my understanding of the AVO 380, 420 and 450 strictly from the .pdfs in front of me.

AVO380 and the AVO420 appear to share the same compressor wheel based on the compressor maps. However, the AVO420 is refered to as having "The high-flow AVO420LGT compressor housing..." which would indicate that the compressor A/R is tuned to improve high-speed flow at the expense of some low-speed response.

The AVO380 uses the 3-4 exhaust housing which likely has an exducer bore diameter and A/R ratio appropriate for low-speed response. The AVO420 uses the 4-5 exhaust housing which it shares with the AVO450. This exhaust housing must have a larger exducer bore diameter to accomodate the extra exhaust flow from the additional power. The A/R is also probably tuned for higher-rpm operation since that is where the highest exhaust flow energy exsists.

[The exducer bore is the bottleneck through which all non-wastegated exhaust gasses must flow. A bore too large will allow the gasses to escape without acting on the turbine. Conversely a bore that is too small will choke the exhaust flow. A/R ratio determines the speed and distance from centerline of the turbine that the exhaust gasses will act upon it. An A/R <1.15 will tend towards low-speed response, A/R >1.15 will be better suited for flow and power.]

The AVO450 uses a compressor that is more ideally suited to push the flow beyond 35 lb/min and pressure ratios greater than 2.5. If you look at the plots I had done you can see that both plots fall within a very efficient range when running the maximum boost and flow (the boost curve is determined by my excel chart and indicated on the maps by the red line). The AVO450 however has a larger peak efficiency "island" below and to the right or our maximum demand. This means that any time I'm running less than full boost, I will have a greater chance of being within the peak efficiency range of the AVO450. Also, the AVO450 does not drop below 70% efficiency when pushing it to the limits. (There is nothing less desirable than a ton of heat at maximum operating speed.... BOOOM!)

LBGT: If you want to, plot your expected boost curve in excel using the spreadsheet format. The formulas are simple! Then input the flow and pressure ratio points on the 380/420 compressor map and 450 compressor map. You will see why the 380 and 420 are much better than the 450 when it comes to low-speed and (relatively) low boost.

Edit: Please don't quote my entire posts. It's long enough having to view once.

[bosco]

enough of this my head hurts to much info to fast. btw will my soon to be AVO 380 w/v.2tmic,inj.,pump,up/dp/cbe and protune hit 300whp or not? :lol: bosco

[edmundu]

^^Yeah, it will:)

[Underdog]

Well Bosco since you asked so nicely...

Attached is my quick plot of what AVO tuned out of their AVO380. I merely took a snapshot of the boost map in the .pdf and dragged horizontal lines across to get the approximate boost value. Based on the conservative calculations, you should be hitting 380 chp and with an *edit: 20%* drivetrain loss that would be just north of 300 whp.

The green line on the compressor map indicates the efficiency of the turbo for that particular boost profile.

Edit: Made it a lot more accurate and simple by putting the compressor map in the background of the excel chart, the axes matched up and everything!

[bosco]

Well Bosco since you asked so nicely...

Attached is my quick plot of what AVO tuned out of their AVO380. I merely took a snapshot of the boost map in the .pdf and dragged horizontal lines across to get the approximate boost value. Based on the conservative calculations, you should be hitting 380 chp and with an 80% drivetrain loss that would be just north of 300 whp.

The green line on the compressor map indicates the efficiency of the turbo for that particular boost profile.

thanks thats all the power i want or really need. :icon_bigg speed is based on cubic dollars not cubic inches and my $ are about gone. :lol: bosco

[LittleBlueGT]

I got this thread off topic, sorry.

What I meant before was: I understand the want for optimizing the turbo's compressor characteristics for the intended application. It just seems odd to me to base a turbo choice based almost solely on that info.

ie: an AVO450 with a TMIC seems like an absolute waste to me, and from Rallitek's testing you can see that. Why lose so much low end response just to optimize the turbo for the efficiency range you want when you are limited by the flow capacity of a TMIC? It is nice to have the whole package optimized to one another. Max out an IC so the turbo is running real efficient? I would rather run the turbo a little hotter (nothing crazy, nothing that will affect longevity) and have a system that as a whole is more balanced. All said and done it is about our power curve. Losing low end power to gain very little up top makes no sense to me.

Though I (like many people) tend to justify their purchases, that has noting to do with my replies. This time.:icon_wink

As far as plotting it out in excel, I really have no idea how to do that, never plotted anything in excel. I will have to try when I have more time on Monday.

I will not sidetrack this threa anymore as this is very good info.:)

[turbo2nr]

I got this thread off topic, sorry.

What I meant before was: I understand the want for optimizing the turbo's compressor characteristics for the intended application. It just seems odd to me to base a turbo choice based almost solely on that info.

ie: an AVO450 with a TMIC seems like an absolute waste to me, and from Rallitek's testing you can see that. Why lose so much low end response just to optimize the turbo for the efficiency range you want when you are limited by the flow capacity of a TMIC? It is nice to have the whole package optimized to one another. Max out an IC so the turbo is running real efficient? I would rather run the turbo a little hotter (nothing crazy, nothing that will affect longevity) and have a system that as a whole is more balanced. All said and done it is about our power curve. Losing low end power to gain very little up top makes no sense to me.

Though I (like many people) tend to justify their purchases, that has noting to do with my replies. This time.:icon_wink

As far as plotting it out in excel, I really have no idea how to do that, never plotted anything in excel. I will have to try when I have more time on Monday.

I will not sidetrack this threa anymore as this is very good info.:)

I have an AVO500 on my WRX with a TMIC.....ran 11.1 @126 with a little 50shot to get going:icon_wink As far as a TMIC not flowing past 400HP....ahhh.


The bigger the turbo....the less heat in the charge......the less need for a FMIC.....also way less volume to pressurize when using a FMIC, thus spool-up is about the same or even better than a small turbo/BIG FMIC.

I posted a link to info on intercoolers, showing the dramatic lag you get when stepping up to a FMIC too soon. I'll find it....

Intercooler Info...

http://www.are.com.au/techtalk/intecoolersMR.htm#Bar%20and%20Plate%20or%20Tube%20 and%20Fin

Turbo Talk...

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

[Underdog]

Turbo2nr, any more details on the WRX? I couldn't find any compressor charts for the AVO500 and what kind of TMIC were you running?

LBGT: I see your point regarding maxing out the TMIC but I haven't seen anything concrete on IC efficiency and what sort of flow loses it would incur at varying boost pressures. If we could see that information then we would know exactly what trade-offs were being made. I believe that with a properly coated/wrapped turbo and high-flow exhaust we could push 1.5+bar on a mid-high rpm setup with a TMIC. We can't say what is properly matched or improperly matched unless we have the specs of the IC in question.

[LittleBlueGT]

Turbo2nr, any more details on the WRX? I couldn't find any compressor charts for the AVO500 and what kind of TMIC were you running?

LBGT: I see your point regarding maxing out the TMIC but I haven't seen anything concrete on IC efficiency and what sort of flow loses it would incur at varying boost pressures. If we could see that information then we would know exactly what trade-offs were being made. I believe that with a properly coated/wrapped turbo and high-flow exhaust we could push 1.5+bar on a mid-high rpm setup with a TMIC. We can't say what is properly matched or improperly matched unless we have the specs of the IC in question.

You definitely have my attention now (not for my set-up, but just for general info)!

In my talks with Sean I was under the impression that the AVO420 made within about 10 hp of the AVO450 when used with a TMIC.

I know the AVO V1 TMIC is too small for the AVO420 and limits the AVO380 a bit. The V2 TMIC does not flow limit as much but has less ability to extract heat.


Now it may be different on different cars, but for our cars I think anything that produces over about 400 chp is limited by the FLOW capability of our TMIC.

[turbo2nr]

I ran 30PSI thru a TMIC, it was a 2002 TXS style IC. The turbo was all done. I had the wastegate pretty much fully closed, running Red-Max #5 (116-117.5octane)

My turbine housing cracked, because to stuff such a large turbine wheel, the walls became too thin after machining......AVO re-released the AVO 500.....that was five years ago, or so......new turbine castings from the foundery in AU. :)


I got one for free. AVO is a decent company!

I don't see why 450-500HP is out of the question with a TMIC on a Legacy. Want me to prove it this summer? I am a little busy building a $20,000 engine package for my Buick for the 2007 season of drag racing, and still have to finish my WRX fuel system and safty crap to run over 135MPH, but I may find time to mess around with my wifes car a little more.

I also just bought and sold a house....YEAH!!! TWO CAR GARAGE!~! BIG Ceiling, going to get a lift!! SO HAPPY! I got wood, just thinking about it.

[Underdog]

Wow man, I'm pumped for you! I can't wait to have a garage space. It is a requirement for my next domicile.

I'm thinking the same thing in regards to the TMIC. It might not be a perrin or avo product if it comes to that but that's something that will be figured out. I'll have plenty of time to look into it over the next few years while the engine "seasons."

I've always had a special place in my heart for turbo Buicks so make a thread with some pics!

[turbo2nr]

My car will be near you getting the new engine installed @ www.cottonsperformance.com (http://www.cottonsperformance.com)
Springfield MA

I have a stand alone ECU of course, Built turbo 400 pro-tranny with solonoid T-brake, manual valve body (have to shift it yourself) Spool, Moser 33spline axles, Racing aluminum heads and solid roller cam, etc....around 820-850HP and maybe 9.2-9.0 ? in the quarter I'm hoping.

My GN has the original paint and just over 20,000 miles. IT's a thing of beauty!

Here is a link to my old engine buildup....it ran an easy low 10 on a crapped out 200r4 tranny that wouldn't shift.

http://www.turbobuick.com/forums/turbo-videos-picture-library/200559-board-member-turbo2nr-feature-car-month-november.html


http://www.elisetalk.com/forums/showthread.php?t=20207&highlight=spectrum

[turbo2nr]

Ever pop a wheelie in a big car shaped like a brick?

It's FUN!:icon_wink

Who needs AWD at that level??

My other Subaru is also ready for RWD.....more later, shhhhh.


** In 1993, Subaru decided to only offer AWD on all it's models. True.

[LittleBlueGT]

I have yet to hear or see anybody run much higher then 340-350 whp on an available LGT fitment TMIC.

FLOW restricted.

If you can prove otherwise, go nuts, I would love to see it!

[2005garnetGT]

someone needs to make a topmount AWIC that doesn't leak/suck.


I have yet to hear or see anybody run much higher then 340-350 whp on an available LGT fitment TMIC.

FLOW restricted.

If you can prove otherwise, go nuts, I would love to see it!

[VTGT]

I don't see why 450-500HP is out of the question with a TMIC on a Legacy. Want me to prove it this summer?

Can't wait to see 500 whp in a 5eat legacy with a TMIC and stock tranny, you will be my hero :). Unless your plan involves using a race tranny in the legacy?

[turbo2nr]

Hmmmm. I may have toi do something to help firm up the shifts

[Vimy101]

^ It all comes down to application, fellas. The right tool for the job.

Great thread.

BTW, I finally found this thread through a member wanting to do a quantitative reasoning paper. Isn't science grand?

[spacejunkiehsv]

Where can you get an engine demand curve for the engine in my 05 LGT? I'll take spreadsheet data if anyone has that. :)

[turbo2nr]

Here is my understanding of the AVO 380, 420 and 450 strictly from the .pdfs in front of me.

AVO380 and the AVO420 appear to share the same compressor wheel based on the compressor maps. However, the AVO420 is refered to as having "The high-flow AVO420LGT compressor housing..." which would indicate that the compressor A/R is tuned to improve high-speed flow at the expense of some low-speed response.

The AVO380 uses the 3-4 exhaust housing which likely has an exducer bore diameter and A/R ratio appropriate for low-speed response. The AVO420 uses the 4-5 exhaust housing which it shares with the AVO450. This exhaust housing must have a larger exducer bore diameter to accomodate the extra exhaust flow from the additional power. The A/R is also probably tuned for higher-rpm operation since that is where the highest exhaust flow energy exsists.

[The exducer bore is the bottleneck through which all non-wastegated exhaust gasses must flow. A bore too large will allow the gasses to escape without acting on the turbine. Conversely a bore that is too small will choke the exhaust flow. A/R ratio determines the speed and distance from centerline of the turbine that the exhaust gasses will act upon it. An A/R <1.15 will tend towards low-speed response, A/R >1.15 will be better suited for flow and power.]

The AVO450 uses a compressor that is more ideally suited to push the flow beyond 35 lb/min and pressure ratios greater than 2.5. If you look at the plots I had done you can see that both plots fall within a very efficient range when running the maximum boost and flow (the boost curve is determined by my excel chart and indicated on the maps by the red line). The AVO450 however has a larger peak efficiency "island" below and to the right or our maximum demand. This means that any time I'm running less than full boost, I will have a greater chance of being within the peak efficiency range of the AVO450. Also, the AVO450 does not drop below 70% efficiency when pushing it to the limits. (There is nothing less desirable than a ton of heat at maximum operating speed.... BOOOM!)

LBGT: If you want to, plot your expected boost curve in excel using the spreadsheet format. The formulas are simple! Then input the flow and pressure ratio points on the 380/420 compressor map and 450 compressor map. You will see why the 380 and 420 are much better than the 450 when it comes to low-speed and (relatively) low boost.




Please read and re-read what the housing A/R number means. It has nothing to do with the exducer size at all. 3/4 is a .75 A/R housing.....4/5 is a .80 A/R or close to that. It has to do with the VOLUME inside the housing and the nozzle area. Different "trim" turbine wheels can fit in the exact same housing with the same A/R, but still have different exducers and the housing is machined to match.

If two turbos have the same turbine wheel (same trim).....then the exducer HAS to be the same and the bore in the housing will aslo be the same, regardless of the A/R of housing. ......and then you could stick that wheel into many different housings with different A/R

Some turbo companys use a decimal point and some use a fraction to describe the A/R.

I did not quote your whole post.....I deleted the last sentence.

All housings are machined to have about the exact same spaceing between the exducer and the housing. (trim of wheel matches machining of housing)

Velocity is lost in the larger housing...it has nothing to do with the bore of the housing for turbine. Just trying to get you to think of air speed going on.....not air slipping by the wheel because of a larger hole. That is wrong.


The larger turbos are absolutly more efficient, for whoever stated otherwise. You need to look at exhaust backpressure, heat added into the charge by tiny wheels spinning too fast, etc....to come up with an idea of what affects the turbos efficiency. You can't just say all centrifugal wheels are about the same. I think what you may be trying to say is, all centrifugal style wheels have the same compressor map SHAPE, almost.

[turbo2nr]

Ever hear of the term "crossover point" in regards to turbos?

It is possible to make more boost than exhaust backpressure....resulting in an engine with well over 100% Volumetric Efficiency. Even up to and over 150% efficiency.....Supras and GNs with BBBIIIIIIGGGGG turbos can reach this point. Who said 77%?? Hog wash! (I know I'm talking about the engine and not the turbo now, different subject, but they go hand and hand)

http://www.gdsdieselparts.com/ball_buster_product__details.htm

http://www.airpowersystems.com.au/350z/turbo_flow.htm

[Underdog]

The exducer bore is the bottleneck through which all non-wastegated exhaust gasses must flow. A bore too large will allow the gasses to escape without acting on the turbine. Conversely a bore that is too small will choke the exhaust flow. A/R ratio determines the speed and distance from centerline of the turbine that the exhaust gasses will act upon it. An A/R <1.15 will tend towards low-speed response, A/R >1.15 will be better suited for flow and power.

This a quick explanation of exducer bore size AND A/R ratio. I'm not saying that a larger A/R directly results in a larger exducer bore.

[turbo2nr]

Good stuff! Carry on.....

[BlackHole]

FWIW, for my modeling I've found that the following Garrett compressor maps work reasonably well vs. real-world data for calculating airflow and hp for the IHI VF series since IHI doesn't like sharing their compressor maps:

VF40 = T3-50
VF39 = T3-60
VF30/34 = T3-super 60 or GT2530

YMMV,
Kyle "BlackHole"

[hyteck9]

Now if we wanted to increase the output of the stock motor from 250chp to maybe 375chp for easy math (and close to 300 whp) we can determine the necessary boost required.

target chp/current chp = 375/250 = 1.5

If we multiply this ratio by the stock boost (13.5 psi) then we determine we will need approximately 21 psi of boost in order to reach our goal.

We can now use the new pressure ratio of (14.7+21)/(14.7) = 2.43 to determine how much flow we must spec. the turbo at.

CFM = ((Displacement(cid) * rpm * .5 * Ve (assume 90% or .9))/1,728) * Pressure ratio = ((150*6500*.5*.90)/1,728) * 2.43 = 617 CFM

So... in order to produce peak boost at redline we need a turbocharger capable of flowing 617 CFM (or ~50 lb/min) at a pressure ratio of 2.43.

Obviously a very simplistic example as it makes no note of losses and is based on only a single parameter (target hp at redline) but hopefully it helps someone.
1st, this thread is awesome!!! I'm learning a great deal.

That said, I have a few questions since I have absolutely no experience turbo matching:

In the formula above isn't the CID more like 153?
where did the divide by 1728 come from?
Ve of 90% is typical for NA engines, does it still apply with the GT's lower compression ratio?

Just trying to understand... I might try to put to gether a little java app. with some of the values hard coded specifically for LGT's.. fun stuff!

[Underdog]

I'm at work so I gotta answer quickly...

Displacement: 2,457cc -> 149.94 in^3 ~> 150CID

1,728 is the conversion factor from in^3 to ft^3 (12x12x12=1,728).

90% Ve was an educated guess based on the fact that we have a modern engine with variable cam lift/timing and 4 valves per cylinder. I would love it if someone could step up and give us a more solid value.

[BlackHole]

90% Ve was an educated guess based on the fact that we have a modern engine with variable cam lift/timing and 4 valves per cylinder. I would love it if someone could step up and give us a more solid value.

I wish I had real world data on VE but from my modeling it's not very pretty. But these values do seems to mimic real dyno results quite well, especially the bottom-heavy torque curve Subies are known for.


rpm VE
2000 85%
3000 92%
3500 90%
4000 91%
5000 94%
6000 82%
6500 77%

just my $.02,
Kyle "BlackHole"

[Underdog]

Kyle,

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

-Rick

[2005garnetGT]

I wish I had real world data on VE but from my modeling it's not very pretty. But these values do seems to mimic real dyno results quite well, especially the bottom-heavy torque curve Subies are known for.


rpm VE
2000 85%
3000 92%
3500 90%
4000 91%
5000 94%
6000 82%
6500 77%

just my $.02,
Kyle "BlackHole"

subaru heads aren't that great really.

[BlackHole]

Rick,

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

What I basically did is worked backwards from the AVO380 vs. stock dyno chart posted in the archives. That chart had actual data on boost level, AFR, whp and wtq. I assumed drivetrain efficiency at 76% (stock 250hp claimed, 190whp avg on dyno). Assuming that the Garrett T3-50 compressor map was close to the stock VF40 (similar dimensions) I worked backwards to adjust the VE to meet the known values from the AVO dyno.

While a bit crude, the projected whp and torque results were reasonably close to real dyno results for both stock and tuned VF40s and when recalculated with a VF39 (using a T3-60 compressor map) the data matched up well with published STi dyno results.

They are certainly not perfect numbers, but so far for my work they have mimicked real-world data well enough, even when TMICs and CAIs are factored in. And the loss of VE at higher rpm echoes what many tuners have said. When looking a bigger turbos, the projections are not quite as robust.

Two comments:
1. I suspect that when the stock exhaust + turbo + intake (including IC) parts are upgraded, the VE jumps a bit. That itty bitty stock turbine wheel and the three cats seem to be major restrictions.
2. Drivetrain loss is not a linear percentage, but I don't have any better data.

just my $.02,
Kyle "BlackHole"

[BlackHole]

Rick,

I would love to know how you are modeling Ve. I still think 90% is a good guestimate from the info you provided.

What I basically did is worked backwards from the AVO380 vs. stock dyno chart posted in the archives. That chart had actual data on boost level, AFR, whp and wtq. I assumed drivetrain efficiency at 76% (stock 250hp claimed, 190whp avg on dyno). Assuming that the Garrett T3-50 compressor map was close to the stock VF40 (similar dimensions) I worked backwards to adjust the VE to meet the known values from the AVO dyno.

While a bit crude, the projected whp and torque results were reasonably close to real dyno results for both stock and tuned VF40s and when recalculated with a VF39 (using a T3-60 compressor map) the data matched up well with published STi dyno results.

They are certainly not perfect numbers, but so far for my work they have mimicked real-world data well enough, even when TMICs and CAIs are factored in. And the loss of VE at higher rpm echoes what many tuners have said. When looking a bigger turbos, the projections are not quite as robust.

Two comments:
1. I suspect that when the stock exhaust + turbo + intake (including IC) parts are upgraded, the VE jumps a bit. That itty bitty stock turbine wheel and the three cats seem to be major restrictions.
2. Drivetrain loss is not a linear percentage, but I don't have any better data.

just my $.02,
Kyle "BlackHole"

[BlackHole]

Interesting tidbit about LGT efficiency from imprezarsx on osecuroms:

I compared these (LGT) logs to some STi logs. WOW, I couldnt believe my eyes. This car has a TON of flow restrictions. Not sure where they all are, but my guess is the exhaust and intercooler. For the same RPM, same boost, and same Cam Timing, this car is passing 203 g/sec vice (vs.) the STi's 260. That's almost 30% less airflow. The injector duty cycle is less than 85% where the sti hit 98% (woops).

Kyle "BlackHole"

[mickeyd2005]

The flow restriction is the hot side of the VF40 turbo.

[2005garnetGT]

The flow restriction is the hot side of the VF40 turbo.
I thought we figured out the VF40 is a P18 just like the VF39?

[mickeyd2005]

Is the VF39 a P18? All I know is that there is a 18 stamped on the hotside.

The VF40 has a tiny hotside.

I have another spare VF40 on my workbench. I'll take pictures of it and try to find the stampings.

[2005garnetGT]

yeah, only the VF22 and 23 are p20 iirc

[mickeyd2005]

I think the P18 refers to the hotside casting and not necessarily the wheel size.

The VF40 turbine is definitely tiny. It's probably the smallest IHI turbine wheel out there.

[BlackHole]

I think the P18 refers to the hotside casting and not necessarily the wheel size.I agree. I have a VF30 and 40 and both dimensionally appear to be the same casting (couldn't find the casting #) but the turbine outlets are very different. The VF40 turbine exducer is ~38mm, while the VF30/34/39 is ~48mm, some 60% more area.

Kyle "BlackHole"

[2005garnetGT]

I think the P18 refers to the hotside casting and not necessarily the wheel size.

The VF40 turbine is definitely tiny. It's probably the smallest IHI turbine wheel out there.
doh!

of course it does.

[mickeyd2005]

There is a good thread over on nasioc. He has the VF22 and VF23 compressor maps. The only thing that I disagree with is that he uses a constant VE (volumetric efficiency) of 85%. I think most engines breathe optimally (85 to 95%) in the mid rpm band and the efficiency is lower at idle and near redline. blackhole's VE in post #70 here seem to make more sense.

http://forums.nasioc.com/forums/showthread.php?t=1265801

[BlackHole]

How about this idea for calculating VE on our motors? It's simple and might give good ballpark results. The only change for LGTs would be to adjust the theoretical mass flow for boost - just measure boost in PR and multiply with the results in Eq#3.

http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm

Kyle "BlackHole"

[mickeyd2005]

I made an excel spreadsheet to overlay engine demand curves onto some of the compressor maps available (including IHI VF22, VF23, and VF24).

The spreadsheet is located here:

http://www.enginuity.org/viewtopic.php?p=18949#18949

I used BlackHole's volumetric efficiency for now. Eventually, I hope to be able to calculate it from datalogs using ride5000's method.

[BlackHole]

How about this idea for calculating VE
http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm


Using the aforementioned method (corrected for boost and metric units) on my dead stock 05 LGT 5MT the efficiency numbers test out as follows (a bit lower than my estimates in post #70):

rpm eff
2000 79%
2500 83%
3000 87%
3500 86%
4000 86%
4500 89%
5000 88%
5500 87%
6000 84%
6500 80%
avg 85%

These numbers are the average of 5 test runs WOT from 2-6.5k rpm in 2nd gear. The numbers were very consistent even though the loads did change a bit (some uphill, some downhill tests). Max airflow was 202 g/sec and max boost was 0.82 bar (11.9psi), which sounds about right for an LGT.

Kyle "BlackHole"

[mickeyd2005]

Thanks for the update.

People with headers or modified AVCS tables can use the same method to come up with their own VE values.

[urfsin]

subscribe!!!

[BlackHole]

People with headers or modified AVCS tables can use the same method to come up with their own VE values.

Anybody have this data? Post away! I'll be happy to post the modified formula and variables to log if anyone is interested. I'll be rechecking this as I mod, but that won't happen for a few weeks at least.

Kyle "BlackHole"

[ama0787]

awdxboost great thread.. Did you get a lot of your examples from innovative turbos web site?

[AWDxBOOST]

i just pulled them from wherever google took me ;)