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MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 1:29 pm
by path0s
So, had this problem for a little while now.
I'll keep it simple --- I peak boost, 25psi, fluctuates between 22-25psi and then settles at 20psi for the pull. Also getting cuts where I can't boost over 12-15psi, but this problem dissapears after turning the car off.
All started happening after the 3" B&B TBE. I'll get some videos up if anyone wants to see.
Re: MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 2:14 pm
by Mikewire
You are probably over boosting, then going into limp mode. Or your IAT temps are too high and the ECU is throttling down the boost, which is basically limp mode until IAT's come down. Have you scanned it for any codes?
I'm wondering how you are getting 25psi out of your tune with a K03...even with my tune at stg2 and most of my vac lines removed I am still peaking about 21psi with no leaks (verified). Are you running the stock SMIC? Tweaked wastegate?
Anyhow, you should maybe look at getting a boost controller on there, or look at getting a FMIC to drop temps and give it some room to breathe. That's my $0.02

Re: MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 2:24 pm
by Dubber
I can almost promise you Mike is correct, I had the same problem. The car really doesn't like boosting 22-25 PSI ..its quite a bit, so unless you've told it to expect it(I am not sure what mods you have on the car) it will shut down the boost in an attempt to protect the engine.
Likewise I am extremely surprised that you are able to get PSI up to that level with the K03, I wrapped it out as much as i could and i got up to 19, and that was just for a while till it blew. Just a cursory warning, running it that high is likely to blow a seal...
Good luck, scan it, let us know.
Re: MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 2:25 pm
by path0s
Well, i'll be cleaning the MAF today. Been hearing a lot of people getting this fluctuation, and then after cleaning it was solved.
But, i found it odd as well that I peak 25 psi & hold 20 psi, unless i'm 5k+RPMs i'll drop to 15. As for the FMIC, the future is looking very bright for one, in which i'll be coming to missoula/billings to have that installed. So you may see a red MKV around.

Re: MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 2:27 pm
by path0s
@Dub, I've actually been running this PSI almost since I got the car, surprisingly. And it's the summer revo tune, due to me normally being in Florida.
I know i'm just delaying the inevitable with the K03 going over, but... that's due to a GT30, Rods, Fuel Pump, etc. around the corner.
Also, when I first started getting CEL's being thrown at me, got it scanned... in florida, and come to find out the new guy at 1552 forgot to throw the key back out of "on" and it threw off my MAF as well as a bunch of others.
VW wiped it, and about a day later the CEL came back.
Edit: sorry about posting this in mods, didn't know if you wanted it in MKV sections.
Re: MKV Boost Fluctuation
Posted: Oct Mon 18, 2010 9:46 pm
by Dubber
Nice! The question then is, "how" are you running such high boost?
Re: MKV Boost Fluctuation
Posted: Oct Tue 19, 2010 6:26 am
by vegas2017
i've been having the same problem in the S. went to aeron to get it played with a bit and i kept blowing of the TBB. so i had him turn it down and now it spikes at 15 holds at 12 or so. mind oyu this is on ko4's. i am still getting fluctuations. sometimes it runs like a bat outta hell and other times it falls flat on its face. i called 034 about it and told that i had got the tune from REVO and about everything that had been happening, they said----Check the vacuum lines, then check with the tuning provider(REVO) to see if they have had any other customers experience misfires under load, we hear of it often due to long coil dwell times specified in the programming, causes the coils to overheat. Sad Sad thing.----might be something to look into. also was wondering if it could be the wasgate(s) not functioning right.
Re: MKV Boost Fluctuation
Posted: Oct Tue 19, 2010 6:46 am
by path0s
Everyone says it's something different. Some say vacuum, wastegate, MAF sensor, some say it's normal and that it always happens. I've only heard it from REVO & GIAC though...
Today i'll be cleaning the MAF, and probably wait a couple days to see if it changes.
Re: MKV Boost Fluctuation
Posted: Oct Tue 19, 2010 6:49 am
by path0s
as to how i'm running such high boost, I don't know... it's always been like this. And after I got my TBE I peaked even higher.
I'm only running Stg 1, Forge DV, Neuspeed P flo, & my 3" B&B TBE.
It stumps me as well, considering it's also the summer program from REVO.
Re: MKV Boost Fluctuation
Posted: Oct Tue 19, 2010 9:16 pm
by Rennwagen1
What is this "summer" tune that you speak of? I've never heard of it. Must be different settings or something...