Strange behaviour - gear change and boost
17 February 2003, 01:56 PM
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I was out playing with the car (MY96 UK) at the weekend and discovered what may or may not be a problem...
I was in 3rd, with the revs at about 5k when I thought it would be a good idea to change up to 4th. Naturally enough, I lifted off the throttle - I thought slowly and smoothly - however, the result was like hitting a brick wall! I didn't see any spiky boost, but I did see the boost gauge almost hit the pin round on the vac side - normally it will stop about 20-25 inHg.
Up to just over 4.5k this behaviour doesn't happen.
I read in the SIDC FAQ about the "ECU bug" Is this it, and is there anything I can do about it? Or is it a dump valve issue? (OEM naff plastic one...)
Any help gratefully receieved, as I don't really have time to be dismantling the car to fault find this week!
I was in 3rd, with the revs at about 5k when I thought it would be a good idea to change up to 4th. Naturally enough, I lifted off the throttle - I thought slowly and smoothly - however, the result was like hitting a brick wall! I didn't see any spiky boost, but I did see the boost gauge almost hit the pin round on the vac side - normally it will stop about 20-25 inHg.
Up to just over 4.5k this behaviour doesn't happen.
I read in the SIDC FAQ about the "ECU bug" Is this it, and is there anything I can do about it? Or is it a dump valve issue? (OEM naff plastic one...)
Any help gratefully receieved, as I don't really have time to be dismantling the car to fault find this week!
17 February 2003, 02:14 PM
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David,
sounds very much like fuel cut by the way you say you hit the windscreen! could be something weird, like the pressure sensor playing funnies!? I know you cleaned out the pipes the other day, maybe you are spiking on change?
have you had a chance to log the boost from the ECU during this blipp ?? just the parameter to see what it's actually doing?
my vacume goes to over -800mmhg at times, which I think is too much (no idea what it should be!) but that's on overrun, so it's sucking hard than tickover (-600mmhg)
dump valve is more likely gona give low boost, leaking boost, than a sudden fuel cut type event.
ecu bug, isnt a BUG as such, its a bodge, to get round the emmisions law. if you hold the car, in second at about 3k for about 3-5 seconds (or longer) then boot it, you will only get 0.5bar boost. lift of and slam it down quickly and it will go back up to normal (or change gear & you feel like you've taken off!)
hope you can sort it out! I'd log it !
Steve
sounds very much like fuel cut by the way you say you hit the windscreen! could be something weird, like the pressure sensor playing funnies!? I know you cleaned out the pipes the other day, maybe you are spiking on change?
have you had a chance to log the boost from the ECU during this blipp ?? just the parameter to see what it's actually doing?
my vacume goes to over -800mmhg at times, which I think is too much (no idea what it should be!) but that's on overrun, so it's sucking hard than tickover (-600mmhg)
dump valve is more likely gona give low boost, leaking boost, than a sudden fuel cut type event.
ecu bug, isnt a BUG as such, its a bodge, to get round the emmisions law. if you hold the car, in second at about 3k for about 3-5 seconds (or longer) then boot it, you will only get 0.5bar boost. lift of and slam it down quickly and it will go back up to normal (or change gear & you feel like you've taken off!)
hope you can sort it out! I'd log it !
Steve
17 February 2003, 02:28 PM
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Thanks
Not had a chance to log the boost yet. I tried it again while watching the boost gauge, but didn't see anything... A log would help to diagnose the pressure sensor, as a funny from it won't show up on a boost gauge... When I get some more data I'll post it up.
My computer got sick, and I lost some of the select monitor stuff I was working on - the install file for the com port I was using, now, I can't remember the name of it
It could have been a lot worse...
Maybe I can get Nic. to do the recoding (and improvement) for me...
I'd like to have a drivable car for my advanced driving test!!
Time for some testing on Millitary Road then
BTW - how are the brakes now you've had a chance to get them run in?
Not had a chance to log the boost yet. I tried it again while watching the boost gauge, but didn't see anything... A log would help to diagnose the pressure sensor, as a funny from it won't show up on a boost gauge... When I get some more data I'll post it up.
My computer got sick, and I lost some of the select monitor stuff I was working on - the install file for the com port I was using, now, I can't remember the name of it
It could have been a lot worse...Maybe I can get Nic. to do the recoding (and improvement) for me...
I'd like to have a drivable car for my advanced driving test!!
Time for some testing on Millitary Road then
BTW - how are the brakes now you've had a chance to get them run in?
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