john banks

Newly fitted PPP on unmodded MY00. Don't have boost gauge, but this morning quite cool, seemed to hit "brick wall" at 3500 and then pick up again (slower) beyond 4000. Is it overboosting? Any thoughts? - back to dealer this pm to go on select monitor - is it more likely when cold morning?

LEE P

Hi john, hope its not to serious, have been interesred in this PPP business so let me know< , have heard that you get more boost when its cold hence these water sprays i think. had a similar experience when test driving A4 Tdi 130, bombing along fine then that brick wall feeling, pulled up then set off and it as like the the turbo wasnt working, dealer said it overboosted once plugged into diagnostic machine, they left it for a while and it was o.k again. obviously a problem. cheers Lee

jack

You're probably hitting the boost limit. Boost tends to be higher when it's colder. Even those so called closed-loop boost control systems take a while before they can adjust boost characteristics to suit climate and altitude changes.

john banks

I'm happy to let it adjust for a while - now has 100 miles since fitting - but I don't want the ECU to learn tame boost settings and reduce my performance - or will it adapt to optimal given time?

jack

Eh....I don't think the ECU can vary the solenoid (factory or otherwise) duty to keep boost in check? I was referring more to electronic boost controllers.

john banks

Just been out for a blast and all is well after all. The "my bottom and kidneys" boost gauge suggests that there is now a seamless delivery of power starting from different revs and different degrees of throttle opening in gears 2 3 and 4. No brick walls, but it is a bit warmer this pm - but very damp indeed lots of standing water everywhere! However in 3rd and 4th gear there is a surge of boost from about 2200rpm but it builds (smoothly) quite significantly from 3700rpm. I think this morning my brain was set to expect (pre-ppp) second gear acceleration when I was in third gear because it felt so lively. Maybe I am just getting used to the power delivery of the PPP - I can't decide which is most improved - the spool up or the midrange from 3700rpm up. It almost feels like a 16V hot hatch, but about three times as quick! There is now a real sensation of power in the upper mid and top end. I suppose the mad exhaust bark magnifies this impression. Certainly now, a 35-75 on the speedo (approx 30-70?) through the gears is under 5 seconds, so I don't think the performance can be that bad. 30-50 in second feels under 2 seconds.

Andy Mid.

John - were you low on fuel when you hit this "brick wall" ?

I've had this problem a couple of times and it's always been just moments after cornering hard with less than a 1/4 of a tank left i.e. some sort of fuel starvation problem.

just a thought ?

john banks

Yes Andy - well under 1/4 of a tank and some enthusiastic back road driving. I drove a further 30 miles this afternoon and then filled up - I managed to get 54 litres in so only had 6 left.

I'll see if it happens again tomorrow - looks like it will be another cold day

john banks

This morning was indeed cool again. The only thing I noticed was in 4th gear accelerating from 2000rpm up. Initial boost was reasonable, then it seemed to add more at 3000rpm and then more at 4000rpm. I'm not sure if it was surging forward and backing off each time or if it was just adding a bit more torque each time. The overall performance was fine, and the above was after a 5 mile warm-up. 2nd and 3rd were fine, but really pin you back in your seat and you're at 5000rpm+ before you know it.

Any ideas? I'm not bothered about the odd "glitch" in power delivery - come to expect it from a turbo engine, but I don't want to have it overboosting all the time as presumably the ECU will retard big time and knock the performance? I also don't want a different restrictor put in by the dealer unless strictly necessary - don't know if they would do this? Dealer is some distance away when working full time 30+ miles away!

If it is overboosting would I really know about it? Or can it be quite subtle. This is probably of the subtle variety. Also I am aware of the half boost thing if you floor it after constant throttle, and that lifting off can help, but find this difficult to prove when driving. Don't like to lift off on exit of a bend. If the car was overboosting would the ECU show a fault when plugging the appropriate green/black connectors together? Is it worth an ECU reset or will this make it all worse?

In which gears is overboost most likely?

Thanks for all your help. Maybe I'm just paranoid and should get on with enjoying the car more!

[This message has been edited by john banks (edited 10 August 2001).]

Richiehash

sounds more like a hint of fuel starvation as the overboost cut is quite violent feels like a quick hard jab on the brakes.
as an aside do they do these for the legacy?
ha'ppp'y boosting
richie

dowser

A boost guage would help you clarify what's happening. Maybe a knocklink to be safe too.

Richard

john banks

The whole point of buying a PPP was that it wouldn't need faffing around with gauges, but it might come to that. If it still feels weird it'll just have to go back to the dealer when I can find the time!

If it is fuel starvation, why most noticeable in fourth gear?

john banks

Driving it again, it just doesn't seem right, now definitely hesitating even when warm, with two or three marked points of pick up in torque. I'm taking it back Thursday afternoon to see what is going on. Will post outcome here. Thanks all so far.

Si James

Check your plugs, NGK have a high nuber of duff plugs, (1 in 20) this is what SUK use,
Bosch are much better apparently.

Just a Thought.


Si

john banks

Thanks - see my reply in later post - PPP overboost fixed - a 1.3mm restrictor instead of 1.2mm stopped the confirmed overboost with no apparent loss of performance.

StanS

iTrader: (3)

Sorry to butt in but could anyone tell me the overboost cut-out psi that a 98PPP occurs ?
Stan

john banks

19.3 PSI = 1000mmHg at least according to select monitor.