2nd Generation Specific 1986-1992 Discussion

Fuel Injection on Decelaration

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Old 10-09-2007, 02:34 PM
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i want bigger flames



wonder if i can trick the stock ecu.
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Old 10-10-2007, 03:10 PM
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i wonder, why it is supposed to cool the engine down.. it should only cool down the engine if injection on decel. is active AND the ignition is turned off, am i right? But you cant just pull out the ignition.. so on deceleration, it fires the mixture.. and i dont know how it is supposed to cool, if there is a full burning process.. does injection on decel. make any sense if the ignition keeps on firing?



or is the benefit of injection, the very short and small "bridge" between going OFF and ON the throttle during WOT to redline or HIghspeed driving? You know, if you have the Fuel Cut and running lets say 140mph, you go OFF the accelerator, and between the full operating of the injectors, and the 0.0% operation (Fuel Cut) there will be some superlean AFR until it gets fully atmospheric air the lambda is reading. and THIS can hurt the engine at highspeed and high dragforces? If you keep injecting when going off the accelerator, you dont have such lean-bridges because it just keeps injecting. i also realised the car makes no "bogs" or something like that, because there is no transition to Fuel/Cut.



the gas mileage gets worse, but the engine runs smoother.. and i HOPE safer! what do you think? does it make any sense if the ignition is still active? or does it the oposit.. not cooling down the engine with injection, but heat it up because of ignite the mixture even during deceleration? does it harm my turbo? and how lean should it be on deceleration? any danger? dont want to blow my engine.



i think its an interesting thing, and i would be very happy if somebody could answer my questions
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Old 10-10-2007, 05:16 PM
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unless i am missing something ignition doesnt fire on deceleration, thats whay your decelerating... that and your trottle body is almost closed. ignition doesnt come backon until you reach idle or the accelerator is pushed again...i dunno just my 2 cents. i would run methenal injection vs fuel as far as cooling goes...
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Old 10-11-2007, 06:20 AM
  #14  
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are you sure there is no ignition on decelaration? In the MAPs of the Power FC, there are also degree numbers in the vac. section, for example -600mmHG and 7000rpm there are 50° BTDC
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Old 10-11-2007, 07:09 AM
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So far as I know (which isn't far) the ignition fires regardless. On decel, the throttle is closed and you've got either a little or no fuel, so the engine decelerates.



A rich mixture burns cooler than a lean mixture, so any cooling effect will derive from that difference.
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Old 10-11-2007, 08:45 AM
  #16  
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well, on deceleration there 0,0% fuel injected (Fuel Cut) So there is NOTHING what could be burned.. In Fact it doesnt matter there is ignition or not, because air cant be burned without fuel anyway.

Ok, but if i eliminate Fuel Cut, and keep injecting fuel, there is a mixture which could be burned.
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Old 10-11-2007, 10:28 AM
  #17  
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Originally Posted by zRotary' post='885093' date='Oct 10 2007, 01:10 PM
i wonder, why it is supposed to cool the engine down.. it should only cool down the engine if injection on decel. is active AND the ignition is turned off, am i right? But you cant just pull out the ignition.. so on deceleration, it fires the mixture.. and i dont know how it is supposed to cool, if there is a full burning process.. does injection on decel. make any sense if the ignition keeps on firing?


rich on decel cools things down, because its a lot of fuel, but no load, you're generating 0hp
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Old 10-11-2007, 11:11 AM
  #18  
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yea thats right.. but i want to know, how lean i can go at deceleration... because if i stay at the level i have now, or even go richer! i am going to shoot 5-6ft flames on each decelerating towards a corner.. LOL thats was TOO much.



What AFR should i MAX. get on decelerating?
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Old 10-11-2007, 11:31 PM
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Originally Posted by zRotary' post='885176' date='Oct 11 2007, 09:11 AM
yea thats right.. but i want to know, how lean i can go at deceleration... because if i stay at the level i have now, or even go richer! i am going to shoot 5-6ft flames on each decelerating towards a corner.. LOL thats was TOO much.



What AFR should i MAX. get on decelerating?


doesnt matter, the widebands not really reading right there anyways.. it shouldnt need much fuel at all though
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