When do you NEED a tune?

I have an 05 GT, pretty much stock. It's got a drop in K&N panel filter (plan to do a cold air soon but haven't gotten so far yet), TGV delete, catless up, and I think that's it as far as engine performance mods (I have a short throw shifter and a couple small things like that but nothing that would affect the ECU).

I have plans to get an accessport soon and run an OTS tune before I cough up the dough for a protune, but I want to have everything done before I drop that money so I don't have to keep going back and getting it re-tuned every time I add something.

The car is still running the stock tune since I don't have the accessport yet, and I feel like I don't have to worry yet as there's not too much done to it currently. I'm going to buy a catback in the next week or two and I'm not sure if that will push it over the edge, or if I should wait to put it on till I get the tuner? I've never owned a car new enough to worry about engine tuning so I'm not sure how sensitive the issue is. Will I be okay with the listed mods AND the catback without even having the accessport yet? If I do need one, when I get it will I be okay running an OTS stage 2? Should I already be running a stage 1 now? If I don't need one now, will the cold air be too much? What about when I finally go for the catless DP, is that pro territory at that point?

Sorry, I know there's a ton of info on this site, but I don't know much about the topic at all so everything I've seen so far is all greek to me and was hoping someone could put it into plain english for me. Thanks in advance for the info guys, always greatly appreciated

These cars needed a retune from the factory. Accessport should be first on your list of mods when it comes to these vehicles.

As far as adding parts and doing a tune over and over, just do it all at once and do an e-tune.

Cobb OTS maps are intended to be generic for a typical set of hardware installed in "stages". Being generic, they try to keep things on the safe side. Within each stage, they offer several OTS map variations for normal, high and low wastegate settings. The idea is, you would start off with the normal wastegate version. If you find the car is overboosting, you would switch to the low wastegate version, conversely if you were not boosting enough, you would switch to the high wastegate version.

You are actually better off with the stock intake, BTW. You will not benefit and may make things worse with an aftermarket intake unless you are running a much bigger turbo. Catback exhaust is more for the sound than anything. You have a turbo, this totally overshadows any supposed power gains from an aftermarket intake or catback exhaust. They are not restrictive enough to matter.

Stage 1 map could be run on the stock car, or stock car with aftermarket uppipe. Catback exhaust would be OK, as well.

Stage 2 map would be necessary if you installed a higher flow downpipe. Once that is in place, your turbo will able to deliver more boost. Too much for the stock tune or stage 1 tune.

You could carry on using the OTS tune if you were happy with the performance at stage 2. A protune could be done to optimize your setup for your particular car even with the typical vanilla stage 2 components.

Where a protune is required is when you change to a different turbo, fuel injectors, different electronic boost controller, etc. These things affect a lot of settings in the ECU and to be safe and get best performance, the settings need to be changed to reflect the new configuration.

Thanks for the responses guys. Clears things up for me quite a bit.

Heh, this is my first real venture away from the days of manual boost controllers and when it was expected that you slap an intake and exhaust on anything as soon as you get the car to try to squeeze that little extra power out of it. Instead of shaving heads and changing injectors we now play with computers. Crazy stuff, I don't even have a smartphone lol.

Basically I just want to make as much power out of this thing as I can without having to upgrade the turbo/injectors, and without risking blowing my 13 year old engine. I have plans to make the thing a missile one day, but that will be after I get tired of DDing it and move on.

Miles could you explain the potential down sides of using an aftermarket intake (besides cheap ones sucking in hot air from the engine bay)? I was always under the impression that the first way to be able to make more power was to get that engine breathing better (both in and out), and the stock intake just looks so restrictive. I've already got the big plastic muffler taken off of it but thought something open element would be even better (plus turbo sounds )

I hadn't realized the catback won't do much for me. I was only thinking of doing it to try to open up some more flow, tbh I'm probably the one and only subaru owner that can't stand the "rumble" (in the distant future when I do headers I will run equal lengths for that reason alone). It would be nice to make a little more noise when I'm on it heavy, but not trying to rattle around town at idle. I have a shiny black car with stock wheels and a spoilerless trunklid, quiet exhaust, etc. Only thing that gives me away is the hood scoop and badges, and maybe if you're nosy enough to peek through those stock wheels at my brakes. First time I have ever blended in with traffic when I drive rather than being a cop magnet, I even have a front license plate for the first time in my life lol.

Given all that, sounds like you are on the right track. Save the money you would have spent on a fancy intake & catback exhaust. Use that money to get an AP. Run a Stage 1 OTS map for awhile.

Get the car healthy & up-to-date on all the maintenance. Make sure you have taken care of the notorious banjo bolt filters. If you want to save money, shop the classifieds for some take off parts in good shape. Improve your suspension and brakes. Get a better quality high-flow catted downpipe. Avoid Ebay junk and made-in-China el cheapo parts.

Install the catted downpipe & update the AP to stage 2 map. You may need a new clutch soon. You may be perfectly content at this point with your 13-year old sleeper. Just keep on top of the maintenance & replace anything that seems questionable.

When you are ready, you can get a protune.

Miles could you explain the potential down sides of using an aftermarket intake (besides cheap ones sucking in hot air from the engine bay)? I was always under the impression that the first way to be able to make more power was to get that engine breathing better (both in and out), and the stock intake just looks so restrictive. I've already got the big plastic muffler taken off of it but thought something open element would be even better (plus turbo sounds )

About the intake. The stock intake is fine, nothing wrong with it, it's a well-designed part. Subaru spent more development dollars and engineering effort than an aftermarket company could. Looks more restrictive? It's really not. Plus, it does not suck in water when you drive through a big puddle.

The intake is very important for a turbo car because this is where the airflow into the engine is measured. That affects most everything in your ECU. Some aftermarket intakes do not handle resonance on the air column in the intake very well, this can skew the airflow measurements made by the ECU. Some aftermarket intakes actually show a decrease in performance in particular RPM bands. Taking off the intake resonator is not a good idea. You get more noise, whoop-de-doo.

Get the car healthy & up-to-date on all the maintenance. Make sure you have taken care of the notorious banjo bolt filters. If you want to save money, shop the classifieds for some take off parts in good shape. Improve your suspension and brakes. Get a better quality high-flow catted downpipe. Avoid Ebay junk and made-in-China el cheapo parts.

 

Install the catted downpipe & update the AP to stage 2 map. You may need a new clutch soon. You may be perfectly content at this point with your 13-year old sleeper. Just keep on top of the maintenance & replace anything that seems questionable.

I plan to check for the banjo filters next time I have a free moment to open the car up (working 3rd shift sucks). The car is in great shape mechanically (and cosmetically), I'm the second owner as of a little less than a year ago and the previous owner was meticulous, the car came with a stack of receipts so I know the timing belt and all that was already taken care of. The shop he used to bring it to for every little thing is a fairly well known Subaru performance shop in my area and they're the ones who talked him into the TGV delete rather than replacing the old, so I wouldn't be surprised if the filters are already gone.

I've already slightly upgraded the brakes, I have the stoptec street package front and rear, and I plan to do a firewall brace when I can afford one, or make my own one day on the Bridgeport if I ever have the time.

The clutch is newer, I know the PO replaced it already but not sure when, the car has 150k on it so it could have been recent-ish, maybe not. It still feels really good no slipping though I can hear the springs rattle, so it could either be f**ked up or just a cheap exedy clutch. I'll deal with that when the day comes, I have other vehicles to drive if that clutch does take a shit.

Oh and trust me I learned my lesson with ebay china junk years ago. Only decent quality parts for me. Not necessarily gonna get the best of the best, but if everyone else is selling something for $400 and I find the "same" part for $60 I know to stay away

I'm actually pretty happy with the car as it is, I just always want more, it's my nature.

About the intake. The stock intake is fine, nothing wrong with it, it's a well-designed part. Subaru spent more development dollars and engineering effort than an aftermarket company could. Looks more restrictive? It's really not. Plus, it does not suck in water when you drive through a big puddle.

 

The intake is very important for a turbo car because this is where the airflow into the engine is measured. That affects most everything in your ECU. Some aftermarket intakes do not handle resonance on the air column in the intake very well, this can skew the airflow measurements made by the ECU. Some aftermarket intakes actually show a decrease in performance in particular RPM bands. Taking off the intake resonator is not a good idea. You get more noise, whoop-de-doo.

Well I was planning on getting a shielded one so I don't suck up any water, but yeah I hear you. As far as the resonator, I don't even like the added sound it makes without it, it's not a spool sound or anything. I just figured having another big hole in the box would help increase airflow. I may end up putting it back on one day if it really makes no difference

As far as the resonator, I don't even like the added sound it makes without it, it's not a spool sound or anything. I just figured having another big hole in the box would help increase airflow. I may end up putting it back on one day if it really makes no difference

I would also recommend against the K&N filter in favor of the AEM Dryflow. K&N uses oil to trap dust particles, and if you over oil it, it can bung up your MAF sensor. The Dryflow just needs cleaning every now and then with warm soap and water, making sure its relatively dry before you reinstall it. No messing with solvent cleaner and oil.

If you haven't done it already, buy a can of CRC MAF cleaner and clean your MAF, then reset your ECU.

I would also recommend against the K&N filter in favor of the AEM Dryflow. K&N uses oil to trap dust particles, and if you over oil it, it can bung up your MAF sensor. The Dryflow just needs cleaning every now and then with warm soap and water, making sure its relatively dry before you reinstall it. No messing with solvent cleaner and oil.

 

If you haven't done it already, buy a can of CRC MAF cleaner and clean your MAF, then reset your ECU.

+1 for the AEM filter. I'm not a fan of oiled filters either.

I would argue against resetting the ECU after cleaning the MAF. No reason to, it'll "learn" and will settle on its values in a couple days after cleaning the MAF if it was actually dirty in the first place.

I'm not the biggest fan of oiled filters myself and usually don't run them, but I've had good luck with K&Ns in the past the few times I have used them. I go really light on the oil and clean them often, that's the key right there. Most people over oil them which gets all over the sensor, and then they cake up really bad which hurts air flow big time. That and I clean my MAF regularly anyway.

But yeah I don't see the need to reset after cleaning either, they do "re-learn" after driving around a bit

Sorry if I am belaboring the point, but the resonator is not just a silencer. It helps dampen air pulses and so improves the performance of the intake. Don't worry about how things look, the designers knew what they were doing. An extra hole to increase airflow is no real benefit, your turbo can suck in all the air it needs without any extra holes.

That may be the case. I'm still mentally stuck on 80s cars when they didn't engineer shit, just slapped it together and said "that'll work". It's taking a lot of mental training to realize cars aren't the way they used to be lol. I was all for turning over the old metal air cleaner lids or drilling holes in plastic airbox covers just to get more air in. I have seen some extremely poorly designed factory intakes over the years, so I naturally don't assume the manufacturer put all this thought into engineering an air cleaner.

Not trying to say I doubt you as you seem to be quite knowledgeable, but does anyone have a link or whatever, some sort of proof that backs this up?

I doubt Subaru purposely built an inefficient airbox, but these aren't supercars I just can't picture them spending a huge amount of man hours designing an air filter housing, it really doesn't look that special to me.

I feel like an open element air cleaner that is protected from hot air and water would have to perform better than an enclosed box with one little opening above the grille, assuming the the sensor is positioned correctly and excessive turbulence isn't created. Sure it's good enough to get the job done, and the gain in power from switching might be single digit figures, but I highly doubt the stock box is the best option out there. Even if it is only 5hp we're talking about here, that's still an increase. And IME often times throttle response improves even if no additional power is noticed.

Unless the computers in our cars really do take away the ability to increase performance with these types of basic mods, then I really am in the dark all over again like I was when I first started tinkering with shit as a teenager.

That may be the case. I'm still mentally stuck on 80s cars when they didn't engineer shit, just slapped it together and said "that'll work". It's taking a lot of mental training to realize cars aren't the way they used to be lol. I was all for turning over the old metal air cleaner lids or drilling holes in plastic airbox covers just to get more air in. I have seen some extremely poorly designed factory intakes over the years, so I naturally don't assume the manufacturer put all this thought into engineering an air cleaner.

 

Not trying to say I doubt you as you seem to be quite knowledgeable, but does anyone have a link or whatever, some sort of proof that backs this up?

 

I doubt Subaru purposely built an inefficient airbox, but these aren't supercars I just can't picture them spending a huge amount of man hours designing an air filter housing, it really doesn't look that special to me.

 

I feel like an open element air cleaner that is protected from hot air and water would have to perform better than an enclosed box with one little opening above the grille, assuming the the sensor is positioned correctly and excessive turbulence isn't created. Sure it's good enough to get the job done, and the gain in power from switching might be single digit figures, but I highly doubt the stock box is the best option out there. Even if it is only 5hp we're talking about here, that's still an increase. And IME often times throttle response improves even if no additional power is gained.

 

Unless the computers in our cars really do take away the ability to increase performance with these types of basic mods, then I really am in the dark all over again like I was when I first started tinkering with shit as a teenager.

But the problem is that an open box will create turbulence, and the ECU won't be operating correctly because the extra turbulence will throw off the calibrations. It is not as simple as your older cars and without sitting down and learning how the ECU controls fueling/ignition/etc, you're just taking wild guesses.

There are several threads on this forum that talk about intakes (look up GrimmSpeed's thread on their cold-air intake design), as well as how different intakes (including even panel filters) require tuning to accept them safely. And until you're pulling way more air than the stock turbo can pull, any intake modifications are negligible at best with power gains, almost always lose the smoothness and stability of the stock one (with regards to fuel trims), and will pull in warmer air than the stock one at low speeds. I'll find some links for you if I get a chance when I'm back at a computer, but suffice to say there's plenty of reading on these forums that beat the topic to death. Also look up some of covertrussian's threads in the Tuning section, he has some excellent write-ups.

I actually read covertrussian's thread about the hack job intake made from a cone and stack of couplers. I wasn't speaking of just slapping a cone filter on there, I was thinking of buying something like the GrimmSpeed or Cobb intake.

I'm sorry if my original point was misunderstood, I'm not the best with text based-communication, I come across completely differently in person than on a forum with no body language or tone of voice or chance to explain what I meant before everyone makes their own assumptions. So yes even after reading that and reading GrimmSpeed's website it definitely does appear that there are in fact intakes that are less restrictive and better than stock. So even though everyone said the stock intake is the best way to go, you just proved that what I was thinking was right, I was just in danger of going about it in the wrong order.

The thing I really learned here is that yes I should wait till I'm ready to tune before I just start slapping mods on, which was the original point of this thread. Intakes obviously DO still have an advantage or they wouldn't cost such a premium, I just need to make sure that I at the very least have an AP before changing stuff. Thank you for pointing me in the right direction, heh even if it was in a roundabout kind of way.

And seriously I hope I hope I'm not coming across like a dick, I'm really not trying to. I'm just terrible at communicating with things that aren't people, the exact reason I do not use facebook or a smartphone, it just ends up getting everyone angry.

I actually read covertrussian's thread about the hack job intake made from a cone and stack of couplers. I wasn't speaking of just slapping a cone filter on there, I was thinking of buying something like the GrimmSpeed or Cobb intake.

 

I'm sorry if my original point was misunderstood, I'm not the best with text based-communication, I come across completely differently in person than on a forum with no body language or tone of voice or chance to explain what I meant before everyone makes their own assumptions. So yes even after reading that and reading GrimmSpeed's website it definitely does appear that there are in fact intakes that are less restrictive and better than stock. So even though everyone said the stock intake is the best way to go, you just proved that what I was thinking was right, I was just in danger of going about it in the wrong order.

 

The thing I really learned here is that yes I should wait till I'm ready to tune before I just start slapping mods on, which was the original point of this thread. Intakes obviously DO still have an advantage or they wouldn't cost such a premium, I just need to make sure that I at the very least have an AP before changing stuff. Thank you for pointing me in the right direction, heh even if it was in a roundabout kind of way.

Wouldn't necessarily agree with that, because if I could make a part that pulls in money and people pay it, what do I care if it's actually better performing?

That said, yes, there are gains to be had from a properly designed higher-flowing intake, but it certainly will require a tune, and the benefits aren't particularly great, especially for the cost. I'm not sure about the GS intake, but from personal experience, the Cobb one (at least, without the air-box, though I can't imagine that really helps) is considerably more difficult to tune than the stock intake at low airflow ranges (i.e. idle/low throttle). This leads to inconsistent fuel trims that bounce all over the place, which can lead to annoying transient issues like random knocking on tip-in due to incorrect fueling, etc. From the work that GS did, it looks like theirs would fare better, but again, no personal experience so I can't comment. The other thing is that at low speeds, almost every aftermarket intake will lead to higher IATs and heatsoak. Most would argue that... who cares, you're not running the car hard during city traffic, but something to consider.

And seriously I hope I hope I'm not coming across like a dick, I'm really not trying to. I'm just terrible at communicating with things that aren't people, the exact reason I do not use facebook or a smartphone, it just ends up getting everyone angry.

Not at all! I haven't noticed or perceived any hostility from you

Intakes obviously DO still have an advantage or they wouldn't cost such a premium, I just need to make sure that I at the very least have an AP before changing stuff.

Um, have you ever hear of marketing?

On a turbocharged car, an intake will only slightly change the PR of the turbo due to a slight reduction in intake depression. Unless you're over at the edges of the compressor map or end of intercooler effiency, this isn't going to do much. You could have just commanded the turbo to spin a bit harder to get the same mass flow rate, and your boost control will reign in any gains there anyway . Most people only change the intake because of maxing out the MAF.

This isn't like a generic NA car that that intake depression is directly perportional to your charge load. It's also not like a lot of cars where what the intake is really changing the effective timing and AFR by screwing with the MAF scaling. We have tools to do that in the actual ECU, and confusing it is not a great idea on our glass pistoned knock limited motors.

Unless you've upgraded your turbo beyond a VF52, an intake is just a noise maker. I have an intake sitting on my desk to eventually put in, not because it'll increase performance but for a noise maker.

It would be really interesting to see data logs from the same car with and without an aftermarket intake. I doubt it would make any difference, but I have to admit that I'm curious.

Note that the aftermarket intakes that pull air from the fender well end up sucking in air that's been heated by the exhaust manifold. It's better than sucking air from the engine compartment of course but I don't think it's better than the stock intake sucking air from the front of the hood. I'd still run the stock intake on my LGT if there was room for it, but my intercooler piping runs diagonally through the same space.

If you pull the resonator off of the bottom of the stock intake, you should plug the hole. My Outback came with the resonator deleted, and the air filter was pretty nasty from road grime getting sucked up. I made a stopper for the hole. I doubt that the resonator or stopper or open hole makes any difference in performance but I agree that it would be interesting to see data logs.

It would be really interesting to see data logs from the same car with and without an aftermarket intake. I doubt it would make any difference, but I have to admit that I'm curious.

 

Note that the aftermarket intakes that pull air from the fender well end up sucking in air that's been heated by the exhaust manifold. It's better than sucking air from the engine compartment of course but I don't think it's better than the stock intake sucking air from the front of the hood. I'd still run the stock intake on my LGT if there was room for it, but my intercooler piping runs diagonally through the same space.

 

If you pull the resonator off of the bottom of the stock intake, you should plug the hole. My Outback came with the resonator deleted, and the air filter was pretty nasty from road grime getting sucked up. I made a stopper for the hole. I doubt that the resonator or stopper or open hole makes any difference in performance but I agree that it would be interesting to see data logs.

I decided to go with the GrimmSpeed intake as I've heard less than flattering things about the Cobb, but the GS actually seemed pretty good from everything I read. I will be installing it in a couple weeks when I am able to get the car tuned. Now I am curious myself, I think I will compare before and after data. Worst case scenario I get a cool looking noise maker until I do inevitably upgrade the turbo in the future. At 160k miles I don't want to do any serious work until I'm no longer dailying the car can pull the engine apart, but that day will come so I'll need one sooner or later anyway. With the resonator removed I've never noticed the filter getting extra dirty, then again I keep my filter really clean anyway so either way it doesn't bother me. I've had aftermarket intakes on just about every car I've owned so it's normal maintenance for me to keep up on it, at least this one isn't a puddle sucker like I ran on my Mitsubishis.

I decided to go with the GrimmSpeed intake as I've heard less than flattering things about the Cobb, but the GS actually seemed pretty good from everything I read. I will be installing it in a couple weeks when I am able to get the car tuned. Now I am curious myself, I think I will compare before and after data. Worst case scenario I get a cool looking noise maker until I do inevitably upgrade the turbo in the future. At 160k miles I don't want to do any serious work until I'm no longer dailying the car can pull the engine apart, but that day will come so I'll need one sooner or later anyway. With the resonator removed I've never noticed the filter getting extra dirty, then again I keep my filter really clean anyway so either way it doesn't bother me. I've had aftermarket intakes on just about every car I've owned so it's normal maintenance for me to keep up on it, at least this one isn't a puddle sucker like I ran on my Mitsubishis.

It's a good question. The ECU measures incoming airflow with a MAF sensor that sits inside the intake and send back a 0-5 volt signal that varies with airflow. The ECU has a lookup table that maps that voltage to airflow in grams-per-second. If you change the intake, you'll almost certainly need to revise that table. (Consequences of not doing so: http://www.airboytuning.com/archives/199 )

You do that with a wideband O2 sensor, adjusting the curve in the table so that you have the same AFR with the new intake that you had with the old intake. Without that, the ECU's grams-per-second information won't be accurate, so you won't be able to make an apples-to-apples comparison of airflow before and after the intake swap.

It's pretty easy if you're familiar with Excel, and if you're not, then it's also a pretty easy way to get familiar with Excel. And for that matter, it's also a good way to get familiar with tuning in general.

If you do a web search for "Subaru MAF Scaling" you'll get a bunch of results. Not all of them are very clearly written, so IMO they make it sound a little harder than it really is.

And how do you plan to address the incorrect MAF sensor housing on that intake?

My plan-

Step 1) I bought the intake.

Step 2) I'm gonna put it on the car and get it tuned by people who know their shit.

Step 3) Happily drive my car and not think about it again.

I'm not a computer guy. I know nothing about it, nor will I ever probably. I've already talked with two well known tuning shops (one was Tuning Alliance, highly recommended by everyone on this site, and the other a full time Subaru only performance shop, the same one the car has been going to it's entire life with the previous owner) and neither one said anything bad about my plans to get the GS intake besides the fact that the Cobb OTS maps won't really work with it because it's very different than their intake those maps were designed to run with. Given I have a TGV delete and catless up but still a stock catted down, the OTS maps wouldn't be a good choice for me regardles. So whatever witchcraft those guys perform to compensate for the MAF on my evil aftermarket intake, I'm sure it will work itself out just fine. Never seen a group of car guys so adamant about sticking with a stock air filter housing in my life. I'm not telling anyone to get rid of theirs, but I will be happy to change mine.

I refused to tune cars with intakes on them for friends, it takes hours to get a proper tune, and gains are just too negligible. Every time I've tried to run an intake on my car, I would be back to stock airbox in no time.

The way Subaru wrote the engine code to deal with airflow calculations is what makes this so hard. On other cars intakes just make the car leaner (because they flow more air), but it doesn't effect MAF voltages in a negative way like it does on Subaru's.

It would be really interesting to see data logs from the same car with and without an aftermarket intake. I doubt it would make any difference, but I have to admit that I'm curious.

I got a bunch of them, looking for anything in particular? The main difference between the stock intake and any aftermarket intake (including drop in high flow filters) is MAF voltage is always lower on aftermarket setups. Because MAF voltage is lower, ECU calculates less g/rev, which leads to less fuel and more timing.

The second difference is extra boost, aftermarket intakes tend to run ~1psi more WGC based boost control systems.

Note that the aftermarket intakes that pull air from the fender well end up sucking in air that's been heated by the exhaust manifold. It's better than sucking air from the engine compartment of course but I don't think it's better than the stock intake sucking air from the front of the hood. I'd still run the stock intake on my LGT if there was room for it, but my intercooler piping runs diagonally through the same space.

 

If you pull the resonator off of the bottom of the stock intake, you should plug the hole. My Outback came with the resonator deleted, and the air filter was pretty nasty from road grime getting sucked up. I made a stopper for the hole. I doubt that the resonator or stopper or open hole makes any difference in performance but I agree that it would be interesting to see data logs.

This is actually why I stopped running a CAI (plus water was getting on the filter). Our belly pans have a couple inch opening that lets hot exhaust gasses to get through to it. When running my CAI my IAT's would jump way up while standing still. But moving they would fall pretty quickly.

This is why I like intakes that still maintain the stock snorkel, but then you start running into limited airflow issues.

And how do you plan to address the incorrect MAF sensor housing on that intake?

This is actually a common misconception, this is why I built my "ghetto" intake, to test if MAF housing was the actual culprit. Even though I used the stock MAF housing, my tune was still way off. Now to be fair, the flowstack did have something to do with it too, I just didn't have 3" pod filters on hand, but usually flowstack would increase airflow which would increase maf voltage, not decrease it like it does on Subaru's.

You guys are missing the point of my question......the 2015 WRX MAF sensor is different than the one used on the 5th Gen GT, therefore, your MAF will not even fit into the MAF housing on that intake.

EDIT: NVM I thought you had a 5th Gen. Sorry.

I got a bunch of them, looking for anything in particular? The main difference between the stock intake and any aftermarket intake (including drop in high flow filters) is MAF voltage is always lower on aftermarket setups. Because MAF voltage is lower, ECU calculates less g/rev, which leads to less fuel and more timing.

 

I was wondering if the grams-per-second would increase, after adjusting the MAF scaling to keep the g/s numbers accurate and comparable.

I was wondering if the grams-per-second would increase, after adjusting the MAF scaling to keep the g/s numbers accurate and comparable.

Just checked and gram/sec stay the same (where boost is same), post MAF scale modifications to account for the intake.

That's expected though, since grams/sec is calculated based on MAF voltage to gram/sec lookup table, which have no choice but to modify when we do intakes.

The real issue is, it seems like more airflow from free flowing filter (even with same maf housing), gets registered as less maf voltage. It's like Subaru's stock airbox and maf scales are designed with a certain turbulence in mind and not airflow for say. Someone have a CAD diagram of the stock intake's flow?