hesitation on WOT in 4th and 5th???
19 May 2002, 03:28 PM
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Hi lads, ive got an completely standard MY00 which intermittenly is suffering from a hesitation on WOT in 4th and 5th, has anyone any ideas please??? its kinda like its stumbling, but not overboost (brick wall)
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Cheers
19 May 2002, 04:06 PM
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It could be that your boost solenoid or wastegate pipes need cleaning, i had this problem on my car but its sorted out now (MY00 with PPP) 
It costs about 26quid if you get the dealer to clean em like i did cos i am not too mechanically minded
Tony
It costs about 26quid if you get the dealer to clean em like i did cos i am not too mechanically minded
Tony
19 May 2002, 05:36 PM
#3
The brick wall effect is Fuel Cut, overboost does feel more like hesitation. Cleaning the boost solenoid should fix your problem, but if you have the chance a visit to a rolling road would identify any potential problems.
19 May 2002, 08:01 PM
#7
I went to PE a few weeks back and they showed my car as having overboost at about 4k rpm, it feels like the car is holding back then going again. I have experienced the brick wall effect, I thought this was fuel cut.
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19 May 2002, 08:14 PM
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cheers lads, i wasnt expecting any info till monday 
i'll give the solenoid a clean and see what happens, thx agin...
scoobynet is invaluable...
Cheers
i'll give the solenoid a clean and see what happens, thx agin...scoobynet is invaluable...
Cheers
20 May 2002, 08:26 AM
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It depends how much and how long the overboost lasts on wether or not you hit the fuel cut.
For example, the fuel cut on an UK MY00 is 1.21 Bar and you could be having overboost problems (spiking) of say 1.5 Bar. Now as long as it spikes to 1.5 but comes back below 1.21 within 2 seconds, the fuel won't be cut but you have got an overboost problem.
You can get away with a little overboost but if it lasts too long, you will hit the fuel cut. What also often happens is that if you are overboosting, the ECU pulls back the boost to compensate and often overshoots. This can feel like the car is retarding and then it increases boost again to try and hit target. You can sometimes see this on a dyno trace when the turbo is spooling up there is a peak, a little trough and then it peaks again.
If you've got more serious problems, the cycle between overboosting and the ECU pulling back the boost can keep on going (overboost, boost pull back, boost again, overboost....) and can feel like a "pogoing"/surging effect.
Matt
For example, the fuel cut on an UK MY00 is 1.21 Bar and you could be having overboost problems (spiking) of say 1.5 Bar. Now as long as it spikes to 1.5 but comes back below 1.21 within 2 seconds, the fuel won't be cut but you have got an overboost problem.
You can get away with a little overboost but if it lasts too long, you will hit the fuel cut. What also often happens is that if you are overboosting, the ECU pulls back the boost to compensate and often overshoots. This can feel like the car is retarding and then it increases boost again to try and hit target. You can sometimes see this on a dyno trace when the turbo is spooling up there is a peak, a little trough and then it peaks again.
If you've got more serious problems, the cycle between overboosting and the ECU pulling back the boost can keep on going (overboost, boost pull back, boost again, overboost....) and can feel like a "pogoing"/surging effect.
Matt
20 May 2002, 10:00 AM
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Matt when u say serious problem what do u mean? its not so much a pogoing effect but defo a surging type...? is it just a clean of the solenoid?
Cheers
Cheers
20 May 2002, 10:45 AM
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Cheers lads i'll give it a go, ive since heard that overboost on the MY00 can give this surging... and is 'softer' than the brickwall effect...
Cheers
Cheers
20 May 2002, 01:13 PM
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Can you fit a boost gauge? Will tell you instantly if it is a boost problem - a £30 would do and they don't look too bad. Expensive ones don't seem much more accurate.
22 May 2002, 10:54 AM
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Chris - falkland performance www.falkland.co.uk there will be VAT as well so it might be a bit more, but not much.
Trout - I suspect we are talking terminology here, but overboost and fuel cut are arguably different. The wastegate solenoid duty cycle is varied according to a 4x4 table of boost error compensation values within max/min duty cycle limits at that load point and engine speed well before it resorts to fuel cut and even at quite extreme boost values it will pull back the duty cycle - for example the MY99 ECU can pull back from 22 PSI peaks without actually cutting fuel. So frequently they "overboost" and do not actually fuel cut - it feels rather more subtle, although driving along the road oscillating from 12-22 PSI is not at all subtle.
Trout - I suspect we are talking terminology here, but overboost and fuel cut are arguably different. The wastegate solenoid duty cycle is varied according to a 4x4 table of boost error compensation values within max/min duty cycle limits at that load point and engine speed well before it resorts to fuel cut and even at quite extreme boost values it will pull back the duty cycle - for example the MY99 ECU can pull back from 22 PSI peaks without actually cutting fuel. So frequently they "overboost" and do not actually fuel cut - it feels rather more subtle, although driving along the road oscillating from 12-22 PSI is not at all subtle.
22 May 2002, 09:26 PM
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John,
to simplify it - with my ECU they are one and the same thing - at soon as you hit the preset boost limit - the fuel cuts - so I was not thinking through my response. The second answer was tongue in cheek - on the ECU I went for turning off the boost limit and mapping up to 2bar to ensure all eventualities were covered
Trout
to simplify it - with my ECU they are one and the same thing - at soon as you hit the preset boost limit - the fuel cuts - so I was not thinking through my response. The second answer was tongue in cheek - on the ECU I went for turning off the boost limit and mapping up to 2bar to ensure all eventualities were covered
Trout
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