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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old November 18th, 2019, 12:53   #1
TDI_Nate_
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Default RC4 ALH Overboost when cold

Hi all, so I have a Rocketchip stage 4 tune from Jeff on my 01 ALH with all the supporting mods. The car runs amazing, loads of power and torque, always boosts to the full set 24/25psi per the tune. But this is the second winter I'll of had this tune and the second winter this issue has occurred. When it gets cold out it overboosts like crazy. I'm talking if I let it it would go to 30psi. And that's no bueno cause I only have a vnt-17 and no head studs. I don't just let it eat cause I like my car and I don't want to ruin it, but it's a bit frustrating. Spring through fall when it's warm it's flawless, only during winter when it's cold it overboosts almost every WOT in any gear. It gets better the hotter the car gets and EGT's (no I don't flog it when the engine is cold). The only difference between the seasons is that I drive the car much nicer in winter seeming as I only drive about 20 minutes to work daily and it takes all of 15 of those minutes to get up to temp and I don't beat it when cold. So is it possible the vanes just get clogged up form me driving it nicely in winter or is this normal because it's "boost season"? Any insight would be great. I had already talked to Jeff about this last year and took the car to him. He did computer magic and it was better after that, but what he did IDK or remember. I'm hoping for help or direction here first before I try bothering Jeff again, plus he's hard to get a hold of.
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Old November 18th, 2019, 17:31   #2
WildChild80
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Jeff is the first place you should have went period. If it's not right go back.

Try some data logging and see if something doesn't like the cold.

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Old November 18th, 2019, 20:17   #3
IndigoBlueWagon
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I think it's likely the vanes are carboning up in the short trips and cold weather. VNT-17s are prone to that. What happens in the cold if you do some hard runs to high EGTs in 4th gear? Does it overboost after that? I bet that would help. Could be all you need to do is clean it out once in a while in winter. I used to have to do that with my 17/22 and RC6.
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Old November 20th, 2019, 07:44   #4
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I know I should go to him first but I already tried last year, and although he fixed it, it took me almost 3 months to get a hold of him, do his trouble shooting, and finally get down to him. It's a 2 and a half hour drive from my house to him and when I work everyday and am renovating a house on the side I have no time to do that again. Hence why I'm trying to figure it out here first, but I totally agree I should probably just call Jeff. And unless a Snap-on Solus can log what needs to be logged I can't do that. I do not have VAG-COM. (Although I am in the market for a CR TDI MK6 so maybe I ought to invest)

Anyway, I know the vnt-17's are prone to clogging up and I had read a thread about it being the case in winter because of not driving as hard. If I can run the car hard enough without overboosting(watching my gauge) to get the EGT's up, the next time on the same drive I go to WOT it behaves itself. It's only the first or second time I try WOT that it overboosts. If I'm cruising in 5th, like 2-2200 rpm and floor it, it goes right to the requested and stays there as it should, this is after I tried a 2-5 WOT run before hand though. It seems to get better if I get some good EGT's in to it and snap the vanes open and closed in 4th or 5th by flooring it for a while and lifting off. So I guess I will try to get some good heat in it more often and see how it works. Otherwise what else could I be looking at?
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Old November 20th, 2019, 08:00   #5
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Quote:
Originally Posted by TDI_Nate_ View Post
If I can run the car hard enough without overboosting(watching my gauge) to get the EGT's up, the next time on the same drive I go to WOT it behaves itself.
There's your answer. So give it a blast once in a while an you'll be fine. You could also raise your IQ for the winter so the turbo's getting a little less fuel. Don't go too high or it'll affect cold starts.
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Old November 20th, 2019, 11:43   #6
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Quote:
Originally Posted by TDI_Nate_ View Post
Anyway, I know the vnt-17's are prone to clogging up and I had read a thread about it being the case in winter because of not driving as hard. If I can run the car hard enough without overboosting(watching my gauge) to get the EGT's up, the next time on the same drive I go to WOT it behaves itself.
Try a run on the highway in 4th gear with the engine around 3000 RPM's.
I did this for a 15 or so miles ride, turned around and one more back home.
It did help.
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Old November 20th, 2019, 14:13   #7
gforce1108
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My 17/22 does the same in the winter - partially because I can't get traction on snow tires to "get on it". Easiest way to get enough heat into it is hooking up my trailer (about 1000lbs total) and blast up a nice long hill. Burns it right out!
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Old November 20th, 2019, 14:44   #8
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Get a catch can, that'll help.
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Old November 25th, 2019, 06:29   #9
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Ok I thought so! And I figured I wasn't the only one. I'll just give it a good blast now and then in winter to clear things out! As far as adjusting my IQ I can't do that seeming as I don't have VAG-COM and otherwise don't want to mess with it. But yeah, thanks everybody for the input and help, if things change I'll update everyone here!
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