B5 S4 question - boost leak??? Please help - (should i try a different forum?)
09-18-2002, 05:20 AM
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B5 S4 question - boost leak??? Please help - (should i try a different forum?)
<center><img src="http://pictureposter.audiworld.com/36692/boost_leak.jpg"></center><p>this is a pretty consistent picture of all my vag runs...
the car seems to pull fine but when the rpms top 4,000 - 4,500 spec'd boost peaks higher then actual.
At full boost under 4,500 rpm actual will peak higher.
Is this indicating a slight leak or is it normal?
If it is not a torn TBB what else should i check 2001.5? My service is due in 1,000 miles - should the dealer notice/check this?
thanks,
Tim
the car seems to pull fine but when the rpms top 4,000 - 4,500 spec'd boost peaks higher then actual.
At full boost under 4,500 rpm actual will peak higher.
Is this indicating a slight leak or is it normal?
If it is not a torn TBB what else should i check 2001.5? My service is due in 1,000 miles - should the dealer notice/check this?
thanks,
Tim
09-18-2002, 06:07 AM
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it doesn't look like there's a boost leak...
according to your chart you start off at 750rpms (idle); you give it gas to 4k and there's no boost build up, you have to take into account what the car is requesting as well- it didn't specify any boost therefore it didn't create boost. why your car didn't specify boost- who knows, my car does this too sometimes. next gear- 1750rpms which is w/in boost range, give it some gas specified boost rises and actual boost follows shortly; same w/ the last run. bpv's look fine as well due to the sharp drop off after gas/boost is applied.
09-18-2002, 06:25 AM
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3rd gear from about 20mph - - here is engine load too (x100 to get on the rpm scale)
<center><img src="http://pictureposter.audiworld.com/36692/with_engine_load.jpg"></center><p>
09-18-2002, 06:29 AM
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the first run to 4,000 was pulling out gently in 1st gear >>>
then I shifted to 3rd at 20mph and let it run up at WOT. I guess my specific question is that actual peaks under requested on first run and under requested on second run (which was probably a pull in fourth or fifth)...
Thanks.
Tim
Thanks.
Tim
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09-18-2002, 06:55 AM
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looks normal- actual boost and requested boost will be similar but never exact at the peak.
a leaky hose or tear would show around half actual boost of a requested boost depending upon the size of the leak. eg: requested boost of 14psi and actual would show only 8psi.
09-18-2002, 06:57 AM
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Alright
When your boost started coming on for the first time..looks like it went right up to where it was supposed to be UNTIL engine load decreased and of course it couldn't make any more boost (did you ease up on the throttle ? , something happen there) In the second part of the graph where you get into boost again theres actually a spike over requested. I notice sometimes this happens, as long as that's not a regular occurence then I'd shrug that off.
09-18-2002, 06:57 AM
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Thank you very much. I have a theory >
that it happens b/c the software begins to pull boost a little as you get close to redline.
I am new to forced induction so i am likely full of **** here, but having fun learning.
I am new to forced induction so i am likely full of **** here, but having fun learning.