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Location:
Terrigal
Registered:
May 2002
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autronic experts - ign cut high boost
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Tue, 15 October 2002 23:09
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Hello, not sure if anyone can help out here but since winding up the boost on my Celica i've encounted a problem...
If you try and take of quickly in first and into second as soon as the boost reaches around 20psi there is a what feels like a huge ignition cut. The engine pretty much dies until the boost drops back down to 15psi or there abouts, starts to increase up to 20 again and ign cut again. I'm guessing its ignition cut as a large puff of smoke comes out the exhaust at this time. It doesn't seem to be the rev limiter though as its happening around the 5000 - 6000rpm mark and the limiter is set up around 7500. In 3rd it doesn't seem to happen. So my guess is its when the boost spikes past 20 maybe? I have looked everywhere though the Autronic thinking there must be some boost limiter. I found a few settings/references to boost and set them all as high as they will go but has not helped the problem.
It was on a dyno recently and because the power run/tuning was mainly done in 3rd and 4th the problem wasn't apparent.
Any ideas? Main problem with Autronics is there is no where to go for support...
Cheers
Joel
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Location:
Adelaide
Registered:
June 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 00:05
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I'm not too sure what's going on without seeing the car, but the easiest way to sort it will be to hook up a laptop and datalog while you run it through the suspect region. I'm assuming the smoke you describe is black? Also, did the car run through the same region of the rpm/press map when dynoed in third? What I'm getting at is that in third the car will build boost more rapidly than in 1st or 2nd due to the increased load. This can mean the engine may miss the tuned area of the map when in a lower gear. Do you have the autronic soft ware that allows for 3D viewing of the fuel and ignition maps?
What I'm guessing at this point (may be totally wrong mind you) is that the engine is running very rich in second where you describe because it is in an untuned area of the map. When tuning the 1FZ-FE in my crown a few weeks ago it was missing and blowing fuel smoke at WOT and about 5000. Initially I thought it was the rev limiter, but it was cured by leaning out the mixture. The feeling of ign cut was due to the spark breaking down in the overly rich compressed charge.
Also, grab a nissan 3 wire oxy sensor or similar and hook it up to the autronic and put it in the turbo dump-that wil also help diagnose probs-it's not a substitute for a wideband sensor but is still hepful.
Tell us how you go
Sean
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Location:
Terrigal
Registered:
May 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 00:21
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Thanks for that advice. On the dyno it was tuned for 20psi, but I suppose if it spikes at 22 or so then those areas would not be tuned.
I had a look in the fuel delivery section. After 20psi (240kpa i think?) It does richen up about 10points all over the map. Not sure if this is enough to cause it to cause the problems it has now.
Definately a posibility though that I need to check out more.
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 01:14
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Sean is right, if the car was only tuned in 3rd or 4th gears then 1st and ssecond gears could induce a different part of the map at the given rpm.
efi computers are tuned in 3d, ie. there is not only one fuel value for every rpm site, the differnt boost characteristics caused by different loads can significantly change the area of the map being accessed.
more than likely, the car will not make as much boost at teh same rpm in 1st and 2nd as it does in 3rd, this could easily cause a power robbing spark breaking over richness + missfire.
Matt
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Location:
Terrigal
Registered:
May 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 01:28
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Ok cool gives me something to work with now. So would the best way to start a datalog, and get it to missfire, then check the logs to see what RPM vs KPA it was at and try adjusting this figure in the map?
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 01:52
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I dont like messing with maps once i've paid an 'expert' to do it for me.
If it were me and it was convenient I would take it back to the tuner and politely ( it doesnt pay to piss these guys off) but firmly request that he fix the problem.
ESPECIALLY as your problem is occurring at the most dangerous part of your mapping, around the point of peak torque.
Matt
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Location:
Sydney
Registered:
October 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 08:53
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i agree with what these guys say about not tuning in 1st and 2nd gear,as it will need seperate maps just for those loads.
BUT,
maybe you could try adjusting your spark plug gaps?
as you increase boost,i dont think your coils can keep up with high voltage,so making the gap smaller(say:0.7-0.8mm) may help.
But it sounds like it wasnt tuned properly.
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Location:
Terrigal
Registered:
May 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 11:51
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Hi all, thanks very much for your ideas. I actually solved the problem tonight, but not without your suggestions!
I went for a run with the datalogged on. Recorded it through first, second and third and was able to capture the problem happening.
You could see clearly the RPM dropping 500 - 1000 or so everytime there was a miss. One of the other things I logged was engine rev limit set point. Right where the misses were happening, the rev limit was set down around 4500rpm. Autronic sets the rev limit based on engine temperature.
Checked the engine temperature at this point and it was showing as 45 degrees even though the engine was up around 85. Moved through the log and its all over the joint, ranging from 40 - 90 degrees which is causing havoc with the rev limiter.
To test it i set the rev limited to 7500 for every temperature and went for a drive, problem fixed. Checked the temp sensor plug and as you wiggle it the reading changes.. Must be a bad connection or wire.
Explains a lot of the small problems I've been having lately with misses coming and going. WIth the coolant temperature changing like that it would also be causing problems with the mixtures. Wondering now if I should get another fine tune done on it.
Anyhows.. Thanks for your help.
Cheers
Joel
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Location:
Eskilstuna, Sweden
Registered:
May 2002
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Re: autronic experts - ign cut high boost
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Wed, 16 October 2002 13:53
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This was a very interesting thread, thanks guys.
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