backfire on DFCO exit
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TECH Senior Member
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From: Long Island, NY
backfire on DFCO exit Lately ive been getting some backfire on DFCO exit. I read that this could be because timing goes down too far and unburnt fuel collects in the exhaust until you tap back into the throttle and the fuel lights up.
Should I correct this by increasing timing from 0* to 10* while in DFCO? or should i try and lower the top row in the VE table so the stock 0* is enough?
Should I correct this by increasing timing from 0* to 10* while in DFCO? or should i try and lower the top row in the VE table so the stock 0* is enough?
I have found it to be a bit touchy... I have upped the timing but stopped short of 10deg as it seems to really want to knock if fiddled with much when it leaves DFCO... and the other item you already noted, working the top of the VE table down. My car was the only one I ever really had the light backfiring from, but I spent some time trying to make DFCO run more and more to see what it could do with fuel mileage. What I found, to be honest, if you are tuning on your own car and have the time, DFCO saved more fuel than the pseudo OL "lean cruise", and not to mention the other PITAs that occasionally pop up running OL as opposed to CL. Please post what works for you though, I would like to hear.
Try increasing the ramp out rate?
In DFCO you have alot of O2 shooting down the exhaust. Low timing after DFCO means unburt fuel and air mixing into a more oxygenated enviroment and combusting again. More timing might mean a smaller chance of this happening.
In DFCO you have alot of O2 shooting down the exhaust. Low timing after DFCO means unburt fuel and air mixing into a more oxygenated enviroment and combusting again. More timing might mean a smaller chance of this happening.
Thread Starter
TECH Senior Member
iTrader: (4)
Joined: Apr 2003
Posts: 6,249
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From: Long Island, NY
I already had the ramp out jacked...
This morning I increased DFCO timing to 10-16* I also trimmed down the VE table by about 8% in the top two rows. I noticed that while taking my foot off the gas quickly, the car was going up to about 17:1 AFR, so I might go back a litle richer and try and handle this with all timing.
Overall the car behaved much better, only backfiring one time, and I was really testing it in spots I know were backfiring with the old DFCO timing tables.
This morning I increased DFCO timing to 10-16* I also trimmed down the VE table by about 8% in the top two rows. I noticed that while taking my foot off the gas quickly, the car was going up to about 17:1 AFR, so I might go back a litle richer and try and handle this with all timing.
Overall the car behaved much better, only backfiring one time, and I was really testing it in spots I know were backfiring with the old DFCO timing tables.
