Just bought a scooby - any ideas what might be causing jerkiness when lifting off 'suddenly' at high reves - 5000/6000rpm

Normal acceleration (wow), general driving no problem, 30mpg motorway

Lifting off more gently eases the problem

I have;

1993 UK
power engineering phase 1 upgrade
dawes device fitted (and AFR)
Blitz SUS filter
bailey twin piston Evo atmo dump valve
3inch twin down pipe
decat
s/sport back box

Is this normal - any suggestions appreciated

Cheers

They all do that, sir.

Take your foot off the go-pedal and the turbo stops boosting.

Paul

Thanks Paul

What I should have said is that it is quite a violent jerk that lasts momentarily until you change down or get back omn the happy pedal

My last scoob didnt do it, but then again it wasnt quite as tricked up as this one ...

Still normal?

Maybe its my driving style that needs looking at!

Cheers

This is caused by the dump valve most definitly.... bet if you remove the DV and fit the old one back on you wont get a problem.. I had the bailey DV on my old car and although it is made for cars with AFM's it still gave drivability problems.


dan:D:D:

[Edited by dhorwich - 8/28/2002 6:02:03 PM]

SHAGGYDOG, I dont know if this is related or not???

I 'uprated' my scoob a wee bit and found that due to higher boost the (standard) dv could not handle the boost when letting off a small amount or letting off slowly :(

The car would shake and shudder violently and sometimes cause a 'lift-off oversteer' situation...quite scarey as I cant drive :)

I changed to a HKS ssq atmos dv, superb!

Changed the whole manner of the car, much nicer :D

Thanks Guys, interestingly I also since spoke to Power Engineering, when I told them I got a Baileys, first thing they said is put the old DV back on which I will be doing at some point then maybe change to another uprated DV that won't give me the shakes!!

Will keep you advised of results, I'll also be contacting Baileys!

Cheers again ...

I knew it...!!!

If i where you i would save up and get a nice one, in the past ive had a bailey DV, Greddy, blitz ss, and now a HKS SSQ which is good, but it has a strange sound quite high pitched.... If i were to buy again i would go for the blitz one it sounds amazing, it has a very loud deep dump...ooer:D

Dan

Update ... spoke to Bailey m/sport today - they confirmed that for scoobs running higher boost that their DV's need a stronger piston spring - they have offered to rebuild and put a stronger spring in it to resolve the problem

This seems to make sense as I've also talked to Forge who offer 2 spring types (a blue and a red one) depending on the boost your running.

Will let you know if it resolves the problem, hope so because I like the sound of Bailey valve and dont want to waste money on a new one just for the sake of a stiffer spring!!!

hmm let me know how you get on. I'm in a similar situation (but don't have the jerkiness). I haven't got my original dv cause it broke, hence why I have the baileys. Be interested in how quick they get it back to you.

Matt

I will be sending it to Baileys mid of next week as like you I dont have the original DV plus I dont think it will handle my boost!

The impression I got is that that it will be a very quick turn around, maybe same day ... lets wait and see!

Will keep you advised

So how did it go?

I seem to have developed this symptom after fitting a recirc Forge BOV, was ok, then I fitted H&S wide mouth downpipe .. now get jerkiness / judder on sudden lift off when high revs and loads of boost!

Running approx 16psi on a ScoobyECU for MY94 jap WRX wagon.

A 1993 uk car??
Is it red by per chance?? (and classed as a 1.8gl? ;))
UK cars didnt come into the uk until 1994/95 as MY95's (it could be a jdm wrx though).
The high speed jerkiness though is common in all cars if you come off throttle, you basically cut the power as your not putting in large ammounts of fuel. normal for all cars sir :D

Tony:D

mutter, didn't do it until I put on the new downpipe, just after the Forge BOV ...!

Maybe the combination of both...!

Neil

Its all about Physics my dear fellow ;)
The more you emphasise the more reaction you get, ie adding a downpipe will increase your boost, coming off boost quickly will be like hitting a wall (or putting your brakes on).
Its natural :D

Tony:D

Interested in the comments from PE as I have a similar set up and they suppllied fitted and sugested my Bailey DV if the now sugesting this is not a good valve I may have a word next time I am up there :(

remove the dv altogether Blank off the hoses fit a cone filter Try it its the muts nuts