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Jefferson.C

Lean Spike Between Gears

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I am getting a quick lean spike between high rpm shifts and would like to see if I can target this area. The engine is an RB25 with adapted RB26 ITB throttle setup. It has not caused any drive ability issues but I tend to get an exhaust fireball I would like to try and eliminate. 
What area in the Accel Enrichment should I address? 

 

leanspot.png

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Im not sure if it is accel enrichment in this case as at 100% TP and 5500RPM you wouldnt normally need much.  However, I would set the accel hold to 6 events for a start, with it set to 2 only the first 2 cylinders will get the full enrichment.

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8 minutes ago, Jefferson.C said:

The main modelled fuel table is TPS based. 4D Map is something I will look into.
Adam, why does the GTR base map use 4 INJ events as a hold? 

It may have in some old version but at least the latest one it is set to 6 events. 

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Tried 4 and 6 INJ events with little change to that lean spike. It did seem to lengthen the accel enrichment time while street driving and and part throttle by just observation on my wideband but overall didn't make much of a difference.
Time to try adjusting the Accel Sense value?
Or I could just be chasing my tail due to the intake manifold already being charged with boost pressure the sudden 0-100% TPS change between shifts are going to yield a little lean spike. 

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Hi- Could it be as you are off throttle pulling high vacuum you are accessing points in your fuel map that are lean ? Then as you go to full throttle again you get a resultant lean spike ? Just a thought .  

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28 minutes ago, Ken Dunkley said:

Hi- Could it be as you are off throttle pulling high vacuum you are accessing points in your fuel map that are lean ? Then as you go to full throttle again you get a resultant lean spike ? Just a thought .  

I had the same thought, especially when you take into consideration the typical time offset of the wideband reading compared to the other logged values

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It looks like before going lean you are going much richer than your target (while letting off throttle and immediately when pressing again). If you have closed loop lambda this might lead to very big negative correction which will show up as lean in the following moments. Please excuse me if this advice is stupid, but I am still a Link ECU beginner, however I guess checking your CLL parameters on the log would not hurt.

By the way, if you say you want to get rid of the fireball, shouldn't you be concerned with the rich area instead of the lean one?

 

Regards,

Florin

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Closed loop cuts off at 4k. Fuel table is well done by friend who is experienced. We will drop the values in the 0 TPS, 5k+ RPM range to help clean up the sudden rich area when the throttles shut. It's a little tricky being an ITB setup but we will get it sorted. 
Thanks for the help.

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