Thread: Ask a tuner...
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Old 03-31-2010, 07:16 PM   #43
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2014 P3 Import Auto
AWD Dyno, Mods, etc


Originally Posted by View Post

Glad to have found this thread. =P Thanks for volunteering to help others.

I have a 2007 STI with the following engine upgrades:
- Cobb downpipe and catted TBE
- Custom tuning on a Mustang Dyno using Cobb AP2
- Rallispec short block with stock-sized forged Wiseco pistons (approx. 2k miles)
- intake snorkel delete

Minimal modifications, really, besides the new shortblock. I had a cracked ringland at 46k miles and replaced the SB rather than rebuilding the old block. It has been great since.

I never considered getting a CAI because I knew it was not that much bang for the buck. I was also advised that the stock STI intake is very similar to a CAI in design, especially with the silencer ("snorkel") delete. It draws air from the front grill, takes it through the fender, and feeds it through the MAF.

This past weekend, I had a chance to ride in my friend's '10 STI with an AEM CAI - very nice looking with the wrinkled red coating. Anyway, I don't know if the CAI made it run THAT much faster than stock, but... as stupid as it sounds... it sure sounded great. I'm just not sure if the performance increase is really great enough to put down some more funds.

My questions:
(1) What kinds of gains have you seen with just a CAI added to a DP+TBE setup?
(2) Do YOU think it's worth the money to do just the CAI with a follow-up tune (total price of $480)?
(3) If not, what other relatively low-cost mods do you recommend to do at the same time as the CAI in order to maximize the cost of a follow-up tuning session?
(4) If not going to a CAI at all, what other mods do you think are better at this point based on the mods I've listed above?

Thanks in advance!
Answers are really car and application specific and will vary...

1. None if the existing intake is flowing properly which it would be with the stock turbo. The stock intake is a CAI and I actually find gains by using it instead of the short rams. The idea is to not pull air from under the hood where its hot. The stock STI air box with a K&N panel filter is good for over 300WHP.

2. No. No tune would be required unless you change the MAF tube size or your new intake creates some sort of turbulence or flat spots.

3. Water injection with a safety. Best bang for you buck at under $500 you can run race tunes all day long with just -40 washer fluid. Also steam cleans valves, plugs, pistons. This prevents carbon build up. Lowers EGT's. Very low maint on these systems, fill the washer tank and forget about it the way I set them up. I can wire it so if fluid runs out or system fails it will cut boost control and drop you to safe levels.

4. Larger injectors. Even a stage 2 cobb OTS tune maxes out stock injectors, fuel pump upgrade. You have forged pistons why are you wasting them, lol. Time for a 20g or a DOM3XT. You could easilly have a 400WHP+ daily driver that would be as reliable as stock at those levels.

Setup an appointment with me to bring you car down to the shop one day and we can sit down and write out your options. For the $500 your talking about on a CAI you could upgrade the turbo for a little more and really open the flow up. You want to get rid of the sleepy turbo over 5400rpm don't you? lol. I couldn't stand the stock STI turbo personally once it was running above stock pressure.
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