Guest Martin F Posted November 21, 2002 Share Posted November 21, 2002 Power mode never came across to the MKIV AFAIK. It basically changed the lock up points on the box to give a more sporty driving mode. Quote Link to comment Share on other sites More sharing options...
adi Posted November 21, 2002 Share Posted November 21, 2002 I think they combined the 'pwr' and 'manu' mode into one button on the mkivs rather than having two seperate buttons as in the late mk3's. Quote Link to comment Share on other sites More sharing options...
Ian C Posted November 21, 2002 Share Posted November 21, 2002 Originally posted by Alex Holdroyd Matt, I've always had this on my car....asked the question before aswell. Mines a 6spd as you know and always used to do it at about the same RPM - I'd accelerate to a ton then ease off and the 'zust note drops suddenly. I apply the clutch let the revs drop - rev it up and hey presto the car sounds normal again.... It might be caused by the sequential system. IanC understands the flow etc quite well might be worth asking him to think about it. Right, at first I didn't think I could help, but this sounds a bit familiar. When not caning or grannying it, I tend to blat up the gears on the first turbo only, changing up just above 3,000ish rpm. Now, I always make sure that I change up before 3,500 because otherwise the whole twin turbo transition starts kicking in, with various VSVs switching, valves beginning to open under light boost pressure, that sort of thing. I have found that on light/middle throttle openings, changing gear at 3500-4000 rpm causes a real lack of response when you try to accelerate again, and I personally think this is because all the transition gubbins is halfway through doing what it does and now has to go back to single turbo mode. It all seems very flat and takes a while to get going again. Sound familiar? Interestingly, 100mph is about 3500 - 3600rpm in a 6spd manual. It's just opening the EGBV and probably switching in the wastegate as well (especially as Alex runs about 0.9bar on turbo #1 which is higher than stock TT boost), so lifting off at this point will affect the operation of these things. Just a theory folks. I think the TT system can get confused sometimes anyway, especially around 3rd gear where the revs still rise rapidly and the boost builds quickly, even more so with a modified engine. -Ian Quote Link to comment Share on other sites More sharing options...
as5606 Posted November 21, 2002 Share Posted November 21, 2002 Not that I know much but from my experience, I'll agree with IanC. It sounds like your gear changes are taking place just when the first turbo is pre-spooling the second and there is always a noticable power drop whilst this happens. Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted November 21, 2002 Author Share Posted November 21, 2002 Your theory sounds good Ian. Thanks for that. I did manage to get it to do it in manu mode this morning so that rules that out. And the problem only seems to happen at around 3500rpm I think that pretty much clears it up. My car is normal after all Thanks for all the input guys Quote Link to comment Share on other sites More sharing options...
Branners Posted November 21, 2002 Share Posted November 21, 2002 I remember reading a while back that on the Scoobs they have a specific map built in to the ECU where if you hold the car at 3000rpm for a specific period of time it suddenly backs off the power for you. It was put in there to beat some Japanese emissions rule where they hold the car at 3000rpm to measure emmissions. Not sure if it applies here..just thought it was interesting. JB Quote Link to comment Share on other sites More sharing options...
Alex Posted November 21, 2002 Share Posted November 21, 2002 \its not just changing gear by the way...which may give Branners's suggestion more clout, if I accelerate in 6th upto about 4,000rpm then gently let the revs die down (over about 2 miles!) that's when it does it.... I think both suggestions have merit...but I still feel its turbo stall/valve issues. Is it more prevalent with cars that have EBC's? (ps I forgot my little test....work wound me up to much to wanna think about...anything Quote Link to comment Share on other sites More sharing options...
eyefi Posted November 21, 2002 Share Posted November 21, 2002 no change there then Quote Link to comment Share on other sites More sharing options...
Ian C Posted November 22, 2002 Share Posted November 22, 2002 Originally posted by Alex Holdroyd \its not just changing gear by the way...which may give Branners's suggestion more clout, if I accelerate in 6th upto about 4,000rpm then gently let the revs die down (over about 2 miles!) that's when it does it.... I think both suggestions have merit...but I still feel its turbo stall/valve issues. Is it more prevalent with cars that have EBC's? (ps I forgot my little test....work wound me up to much to wanna think about...anything Well, lifting off the throttle between 3500 and 4000rpm is pretty much the same as changing gear as far as the engine/ecu is concerned. Your prespool/transition stuff is still going to be gearing up and then suddenly not. I'm rather sure it's not turbo stall, that's a really nasty bad thing to happen and it won't happen too many times! Valve issues? If you mean the VSVs getting tied up, then that's pretty much what I mean anyway. -Ian Quote Link to comment Share on other sites More sharing options...
Need4Speed Posted November 22, 2002 Share Posted November 22, 2002 Mines always done this. As far as I understand it, the ECU does this to make the transmission smoother. I think the feel of this is exagerated by running higher than standard boost. Technical experts - feel free to correct me. Quote Link to comment Share on other sites More sharing options...
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