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Discussion Starter · #1 ·
From my current knowledge and the research i've done on the 15+ WRX... the stock intercooler seems to be one of the weakest parts of the engine. not efficient enough with cooling during hot days and its the biggest source of turbolag.
When looking at the standard stage 1,2,3 power packages that are coupled with the Cobb AP, the intercooler upgrade only comes in the stage 3. Obviously you could do an e-tune or pro-tune if I only bought the intercooler.

So my questions are: if my first engine/performance mod is a top-mount intercooler, would I have to do a tune? if so.. are there any OTS tunes i can pickup with the cobb ap? lastly, is it even worth it to upgrade the IC first?
 

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Yes you would have to tune.

not efficient enough with cooling during hot days and its the biggest source of turbolag.
There is a lot of misinformation about the OEM TMIC. I think you are misunderstanding turbo lag.
 

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Wouldn't the aftermarket charge pipe and other piping help reduce turbo lag?
It will help improve transient response to a certain degree, but only slightly. I suggest that we define terminology here:

https://drivetribe.com/p/what-is-turbo-lag-TqP2ymFJRreteZAXwd45UQ?iid=R1veCF88S4qht-8YkSvQ6g

The largest contributions to boost threshold and transient response are the size and location of the turbo as well as exhaust gas velocity in the manifold (this is closely tied to cylinder scavenging, head design, and energy loss).

The significant downside of an OEM tube-and-fin intercooler is the pressure loss -- usually between 2.5 and 3.5 PSI -- when compared to the 0.5 PSI pressure loss of an aftermarket bar-and-plate unit.
 

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As I understand it, without a tune you wont seem much improvement. The larger intercooler works to keep temps lower which allows you to take advantage of more aggressive timing. If you aren't adding timing by tuning, you aren't going to see much benefit. the only benefit you may see is if your car is heat soaking and pulling timing with the current tune. You MAY get some of that back but no guarantees.
 

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As I understand it, without a tune you wont seem much improvement. The larger intercooler works to keep temps lower which allows you to take advantage of more aggressive timing. If you aren't adding timing by tuning, you aren't going to see much benefit. the only benefit you may see is if your car is heat soaking and pulling timing with the current tune. You MAY get some of that back but no guarantees.
Without a tune, it might even be a detriment. This depends on IF Subaru added an IAT sensor after the intercooler (I don't have the answer to this). An ECU is calibrated to the relationship of thermodynamic equilibrium with the OEM TMIC. This relates directly to the amount oxygen being forced into the cylinders. Upsetting this relationship by cooling the intake charge MORE than expected can slightly perturb open loop fueling. This is also the concern with heat-soaking the OEM intercooler to the point where it loses cooling efficiency -- though when this occurs the mixture will run rich and not lean.
 

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Discussion Starter · #7 ·
Thank you both for the information...

So, maybe I should hold off until it is actually needed.... I bet a FMIC would lower the amount of distance in the loop, which would help with reducing the transient response delay..

I wonder if an aftermarket Recirc BOV would help with retaining boost pressure? https://www.youtube.com/watch?v=QFyw-ktSQEQ
 

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So, maybe I should hold off until it is actually needed.... I bet a FMIC would lower the amount of distance in the loop, which would help with reducing the transient response delay..
This is a different question entirely. The EJ platform had the opposite issue -- a FMIC solution would undoubtedly INCREASE the intercooler piping in a stock-location turbo setup. You may be correct about the piping with the FA20F.

I'd be mostly concerned with the removal of safety equipment in fitting a FMIC.
 

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True. the aftermarket crash bar that comes with the FMIC is a bit sketchy. the turbo for the fa20 is located at the bottom-front-right of the engine
I was under the impression the turbo was mounted nearly symmetrically in the center beneath the engine.

 

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Upgraded IC should be last of your concern at stock power. Look into getting an Accessport, as a Stage 1 flash will rectify the rev hang and dead power spot issues. Then think about TGV/EGR deletes, a jpipe and cbe or whatever your goal is. Everything requires a tune on these cars to play it safe. Spend that 900-1500 elsewhere for now

Turbo lag issue seems fixed somewhat with the Stage 1 flash, or even stage 2 with jpipe and the ball restrictor removed. Obv with a stage 2 I'd shoot for a good pro or etuner who can fix the issue further for you

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