Drop in Boost on 3k RPM Runs in 3rd
Thread Starter
Junior Member
Joined: Oct 2006
Posts: 1,180
Likes: 0
Drop in Boost on 3k RPM Runs in 3rd
My friend (ALMS 225 Coupe with APR91, VTDA, 2.5" Catback, 18" RS4 Rims) and I (225 Roadster with GIAC91, VTDA, Custom 3" Catback, heavy 19"s) made several WOT runs last night. I have a boost gauge and Modshack boost machine, and he has neither. Neither of us have a 3" downpipe, FMIC or silicone hoses.
We would start at 3k RPM in 3rd gear, honk the horn 3 times, and compare how we would pull on each other to redline. For the most part, we were completely nose-to-nose, however I noticed on my boost gauge that I would spike to 21-22psi @ 3k, hold at 20psi from 3k to 4.5k, then from 4.5k to redline it would steadily drop to 10psi. Is this normal? I'm asking this because my friend's TT would continue to slightly pull after we've reached 4.5-5k RPM, while I would start to taper off.
Secondly, what sorts of mods would help me retain boost longer? FMIC? 3" downpipe? Silicone hoses? Larger intake manifold? Adjust my Modshack Boost Machine? What's recommended..
I've realized his car is possibly 300lbs to 400lbs lighter than my car, especially with my heavier rims. While this has a lot to do with acceleration, I doubt it plays a part in the ability to hold boost to the higher RPMs.
Thanks!
We would start at 3k RPM in 3rd gear, honk the horn 3 times, and compare how we would pull on each other to redline. For the most part, we were completely nose-to-nose, however I noticed on my boost gauge that I would spike to 21-22psi @ 3k, hold at 20psi from 3k to 4.5k, then from 4.5k to redline it would steadily drop to 10psi. Is this normal? I'm asking this because my friend's TT would continue to slightly pull after we've reached 4.5-5k RPM, while I would start to taper off.
Secondly, what sorts of mods would help me retain boost longer? FMIC? 3" downpipe? Silicone hoses? Larger intake manifold? Adjust my Modshack Boost Machine? What's recommended..
I've realized his car is possibly 300lbs to 400lbs lighter than my car, especially with my heavier rims. While this has a lot to do with acceleration, I doubt it plays a part in the ability to hold boost to the higher RPMs.
Thanks!
AudiWorld Uber User
Joined: Dec 2000
Posts: 53,281
Likes: 2
He's got APR, You have GIAC....>
Hate to say it, but lots of GIAC cars have that same problem....
Generally at 4500 + heat soak sets in....ECU dials down boost as a protective measure. Best thing you can do for WOT High boost performance is an FMIC..
Generally at 4500 + heat soak sets in....ECU dials down boost as a protective measure. Best thing you can do for WOT High boost performance is an FMIC..
AudiWorld Super User
Joined: Mar 2000
Posts: 8,091
Likes: 1
A FMIC will allow you to hold boost as it scrubs heat...>>
better than the SMICs do. You won't gain any HP but it keeps you from loosing it.
The Samco turbo intake hose was made because the Audi hose would collapse around 5K. The IC hoses are the same ID throughout the hose whereas the Audi tapers.
The DP will help with the upper RPMS by being less restrictive and 1/2 inch ID larger.
As far as the intake goes, Maybe getting it extrune honed will help with flow. But Audi has done a good job on this peice.
Just my $0.02
The Samco turbo intake hose was made because the Audi hose would collapse around 5K. The IC hoses are the same ID throughout the hose whereas the Audi tapers.
The DP will help with the upper RPMS by being less restrictive and 1/2 inch ID larger.
As far as the intake goes, Maybe getting it extrune honed will help with flow. But Audi has done a good job on this peice.
Just my $0.02
Thread Starter
Junior Member
Joined: Oct 2006
Posts: 1,180
Likes: 0
It was a relatively cool night too.
I remember some estimates of the 225's Dual SMIC being 83% effective while a Forge FMIC being 90% effective. Is the difference in the ability to hold boost really noticeable in real world application?
Trending Topics
AudiWorld Stories
Bringing Audi to Life for Audi Fans
10 Strangest Audi Designs That Actually Made Production
Joe Kucinski
2027 Audi Q7 and SQ7: Audi Upgraded EVERYTHING!
Michael S. Palmer
Audi Unveils Absurdly Cool New Supercar: 10 Things You Need to Know!
Verdad Gallardo
The Highs & Lows of Every Audi C-Class Generation
Joe Kucinski
Top 10 Most Expensive Audis Ever Sold on Bring-A-Trailer
Brett Foote
10 Audi Features & Options We Miss the Most!
Joe Kucinski
Audi Recreates Crazy-Looking Speed Record Breaker From 1935
Verdad Gallardo
Coachbuilder Recreates the 1995 Audi TTS Concept
Verdad Gallardo
Every Audi V10 Car Ranked!
Joe Kucinski
AudiWorld Super User
Joined: Apr 2004
Posts: 4,773
Likes: 302
Hey----- Where is that "they are all the same, just use the nearest tuner" talk ?
This makes sense though. I have yet to see the need for a FMIC. Mine holds boost better in hot weather than in cold. (yes I know the ECU dials boost back due to density of cold air)
Oh --Schwing. I finally installed the boost machine. Cool. Had to MAKE myself dial it back to about 21-22 peak. Was seeing 24 !
Makes a small but noticable difference. I mounted it by clamping to the strut brace. just enough room to clear the hood. (For other readers I used the stock air box. Call me old and conservative.
Oh --Schwing. I finally installed the boost machine. Cool. Had to MAKE myself dial it back to about 21-22 peak. Was seeing 24 !
Makes a small but noticable difference. I mounted it by clamping to the strut brace. just enough room to clear the hood. (For other readers I used the stock air box. Call me old and conservative.