Sudden Throttle Lift Off = jerkiness
#1
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
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
#3
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
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
#4
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:
[Edited by dhorwich - 8/28/2002 6:02:03 PM]
dan:
[Edited by dhorwich - 8/28/2002 6:02:03 PM]
#5
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
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
#6
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 ...
Will keep you advised of results, I'll also be contacting Baileys!
Cheers again ...
#7
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
Dan
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
Dan
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#8
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!!!
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!!!
#9
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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
Matt
#10
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
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
#11
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.
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.
#12
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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
Tony
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
Tony
#14
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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
Tony
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
Tony
#15
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
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