Lean light throttle tip in
Thread Starter
TECH Apprentice
Joined: Jul 2012
Posts: 341
Likes: 12
From: UK
Lean light throttle tip in Hi,
Hope someone could give me some pointers where to look please.
LS1 gt45 turbo manual EFIlive
noticing that if I am cruising and come off throttle, the AFR goes little rich first then if I roll into the throttle lightly it first goes very lean over 20 AFR and engine braking severe and car jolts It is worse at lower speeds.
Any ideas to try please?
regards
gav
Hope someone could give me some pointers where to look please.
LS1 gt45 turbo manual EFIlive
noticing that if I am cruising and come off throttle, the AFR goes little rich first then if I roll into the throttle lightly it first goes very lean over 20 AFR and engine braking severe and car jolts It is worse at lower speeds.
Any ideas to try please?
regards
gav
Thread Starter
TECH Apprentice
Joined: Jul 2012
Posts: 341
Likes: 12
From: UK
Using COS3 with narrow band 02 feedback where selected in commanded map.
I have tried redoing the 'VE table in those areas (altered commanded to 14.60 instead of 14.63)
will see how that goes. Interestingly when drove it it never went lean like when it was controlling on the 02d....
will do another log and then turn 02s back on th the commanded map and see what happens.
gav
I have tried redoing the 'VE table in those areas (altered commanded to 14.60 instead of 14.63)
will see how that goes. Interestingly when drove it it never went lean like when it was controlling on the 02d....
will do another log and then turn 02s back on th the commanded map and see what happens.
gav
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Joined: Aug 2010
Posts: 7,323
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From: Ann Arbor, MI
Like HPTuners, I'm sure that EFIlive has a "Fueling Transient" section with many parameters; partly to simulate the "Accelerator pump" on a carburetor. Changing these from a base tune is typically needed when running a non-stock intake manifold, especially a metal one.
When you come off the throttle, the vacuum increases which pulls fuel off the walls of the intake manifold, giving you the rich AFR. When you add throttle, the opposite happens, vacuum lowers, fuel sticks to the walls and you go lean. With these "Transient" parameters, the ECM can compensate for this to a large extent.
While changing the VE table can help, the VE table is designed for steady state throttle, not these transients. Granted the changing throttle will go into parts of the VE table that a steady throttle won't, but there will be unwanted side-effects trying to fix it with just the VE table.
When you come off the throttle, the vacuum increases which pulls fuel off the walls of the intake manifold, giving you the rich AFR. When you add throttle, the opposite happens, vacuum lowers, fuel sticks to the walls and you go lean. With these "Transient" parameters, the ECM can compensate for this to a large extent.
While changing the VE table can help, the VE table is designed for steady state throttle, not these transients. Granted the changing throttle will go into parts of the VE table that a steady throttle won't, but there will be unwanted side-effects trying to fix it with just the VE table.
TECH Addict
Joined: Dec 2004
Posts: 2,177
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From: Florida
What cam and motor?
I have found that most of the time the stock transient tables don’t need much modification if your ve and maf calibration is right. Almost every time I’ve had tip in problems and tried to fix it with transient tables, it was better resolved with the ve table.
if you have a really big cam then that may not be the case though
I have found that most of the time the stock transient tables don’t need much modification if your ve and maf calibration is right. Almost every time I’ve had tip in problems and tried to fix it with transient tables, it was better resolved with the ve table.
if you have a really big cam then that may not be the case though
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Thread Starter
TECH Apprentice
Joined: Jul 2012
Posts: 341
Likes: 12
From: UK
Fic Bosch 60lb
Stock bottom end, Pac valvesprings and better pushrods.
Can't go over 550 to 600 hp as clutch would need doing and t56....
How heavy are those turbo compared to my gt45?
regards
gav
Stock bottom end, Pac valvesprings and better pushrods.
Can't go over 550 to 600 hp as clutch would need doing and t56....
How heavy are those turbo compared to my gt45?
regards
gav
7875 will spool quicker and weighs less and smaller externally than the ebay gt45 as well
Thread Starter
TECH Apprentice
Joined: Jul 2012
Posts: 341
Likes: 12
From: UK
Hi, you mean these?
https://www.ebay.co.uk/itm/225147243...BoCrlsQAvD_BwE
It is a little laggy and heavy. If I were to change it would be for something that maxes around 700hp but light as possible and spool a lot quicker.
regards
gav
https://www.ebay.co.uk/itm/225147243...BoCrlsQAvD_BwE
It is a little laggy and heavy. If I were to change it would be for something that maxes around 700hp but light as possible and spool a lot quicker.
regards
gav