quicker spool

So I'm asking about a quicker spool for my 20g/tdo06 8cm. I understand that it can only be improved to a certain extent as it's a top end turbo. However I hear of ways to adjust target boost and wgdc to keep the wastegate closed while in cruising/around town mode. My question is:

1. should i be targeting my max tuned boost earlier on and then set max wgdc to 90 in the lower ranges so that TD kicks in to try and achieve target? (though initial wgdc would have be upped as well since TD cumulative and active maxes out?)

2. will this require me to pull timing subsequently since there's earlier boost in lower rpms?

amr cx500 20g/td06 8cm hotside

process west tmic

tbe

gs ebcs

dw 850's

dw 65c

wot afr's 10.8/9 via aem uego

max target 20psi

Your wastegate is not going to open until around spring pressure. Your turbo supposedly has a 1 bar spring, so no matter what you do with your TD and WGDC mapping, the WG is not opening until it gets near 14.5 psi.

Subscribed for an expert's response to the rest of your question (14-20psi). Fun to see how various people address holding the WG closed until the last possible moment without getting too much of a spike. I don't know how much extra you can really yield with an IWG, but with a EWG there are some fun 3-port solenoid setups and associated tuning that can actually push the valve down to keep it closed longer.

From reading LittleBlueGT's tuning thread, he commented that he actually liked how the IWG boost would come on a little more smoothly than with the hit made possible by the EWG. I tend to agree. So it is possible you're not missing out on much or anything (I don't know what you tune is), and that your only limitation is in fact physics.

Lastly, I keep on saying a wet shot of nitrous can buy an extra 1000rpm of boost curve shift to the left, but since it hasn't caught on in popularity (in the Subaru community anyways) most people ignore it. It would require some complexity in the controller, namely a RPM window switch, boost switch (to turn it off when you hit XX), and something to activate it (push button, WOT switch, TPS voltage, etc). Of course n2o runs out, but so does gas.

Some RBXXDET_ guys and Supra guys have used it with great success, but what would they know about big turbos...

Lastly, I keep on saying a wet shot of nitrous can buy an extra 1000rpm of boost curve shift to the left, but since it hasn't caught on in popularity (in the Subaru community anyways) most people ignore it.

That's because its not legal for street use or emissions, and we Suby owners are generally conscientious about the environment, present company excluded.

Good read right here on how to set and hit realistic boost targets. Legend's method is pretty simple and provides good boost control.

http://legacygt.com/forums/showthread.php/having-issues-figuring-out-wgdc-171702.html

good question, too bad you're not answering it

Once Spooled, freight train.

good question, too bad you're not answering it

Since you put it that way, I'll let you figure it out yourself.

You've already done pretty much all you can do. TMIC, 3-port, and stock headers are advantageous to FMIC, stock bcs, and aftermarket headers. Your mods support quicker spool.

I tune boost very much with 1st and 2nd gear performance in mind but it is a little bit cumbersome and the gains are nice but probably not huge. I wouldn't waste my time on it with that turbo because like you said you've got a top-end turbo built for speeds greater than 50mph.

I'd like to see a WOT 2nd gear boost log 2krpms to redline to see what is happening though.

You could always retard timing during spool up to increase egt's and speed up the spool. The engine won't last long, but it will spool better.

I disagree. If you keep EGTs safe (EJ25 exhaust valves are pretty stout) then you can retard timing to what you feel is the safe limit of EGTs, and in turn the turbo will spool a little earlier. Some Evo guys are fans of this.

It's not worse for the engine to run higher EGTs. There is a fixed amount of energy to be released in any given combustion event. If you advance timing, a greater proportion of the energy will be released in the cylinder, and less will be released immediately outside the cylinder, which is why when you advance timing, EGTs go down. Unless the exhaust valves are the weakest link, EGTs are not the biggest consideration. Stock pistons are the weakest link. So lowering EGTs means more heat on the pistons. Retard timing (within reason) = happy engine.

I only say the engine won't last long because every day I read about more burnt up exhaust valves. I'm probably being overly cautious saying that.

That has me concerned as well. Part of it may be that almost no one runs an EGT gauge. I haven't followed AT vs MT, but AT ECU tune has a momentary compensation table that pulls timing as much as 25* during a shift. The EGT spike, however short, must be crazy high since timing at higher loads would swing negative. It can be tuned out with Cobb ATR. I do not know about RR, but last I checked the table was not defined.

Nitrous will help spool

I did not read the rest of this thread.

yes you are.

because rocketcar

Dave - one other note that may be relevant- dropping max wgdc and target after 6k to prepare for an auto shift, power levels around that environment, depending on your setup eases up on the tranny...(for us non-vb mod owners)

I have seen people cut the bottom row of the RT table, which closes the throttle body part way above XXXX rpm. I like your boost target approach a little better--in theory--because it keeps the requested torque value high. The TCU reads the RT value, so you want it to be as high as possible (on AT cars). You would time the drop for around 6475 rpm or so. Not a bad idea. Turbo will spool right back up when the RPMs drop, so that's not an issue. It might hit max boost again before the shift is even over.

Hmm. I do have my egt sensor still in my up pipe. I could just remove the resistor and start logging that. Or is it too far down the exhaust to be of any use?

 

A couple inches from the #2 or #4 head, max.

 

That timing retard worries me as well. It's another reason I try not to wot shift too much (paranoia). The table isn't defined yet afaik, but I haven't really looked at any experimental defs in a while.

It's standard issue with Cobb ATR. I have not directly compared the logged timing drops to logged EGT from aftermarket gauge, but it would be very nice to publish that data for the benefit of all 5EAT tuners/owners.

Sounds like someone needs to guinea pig some nitrous on a controller.....

Controller would be easy. I'm just not interested in doing it.

Yes, it has been done on turbo cars, and it has been discussed many places on the net. I have seen a before/after dyno of a R34 or so showing the curve shifting left by around 1000rpm. The Subi crowd hasn't jumped on that wagon, otherwise I bet it would be done by many. The wiring is easy, just use basic open or closed switching with a couple of the aforementioned sensor switches in series. The cost is around $750 to do it, but you can easily spend double if you want. Plus tank fills. If people truly cared about shifting the curve left significantly, they would do it. Thus it must not be too big of a driveability problem for most. It's amusing, people use spark cut antilag probably more than nitrous spool assist, probably because it went mainstream. Yet big boom in exhaust is known to be hell on those parts (namely the turbine). Just goes to show the importance of what is "in" when someone makes an upgrade decision.

I personally am 'downgrading' from TD06-20G to VF37-PE1825 twinscroll. Boost threshold should not be a problem anymore. I don't like my 20G on city streets.