Backfiring on the dyno ... too much smoke ...
01-30-2005, 05:30 PM
#1
Backfiring on the dyno ... too much smoke ... OK numbers, but .... smoke-n-fire !!!!????
Car was dyno'd about a week ago. On deceleration, at about 6500 rpm, my car backfires real bad ... and it smokes like crazy (white smoke) ... had fire shooting out the back of my Borla tips from raz (fuel light-off). Could this be from running TR-6 plugs instead of TR-55's? Would running the colder plug cure this?
My thoughts are that the PCM sees more spark and dumps more fuel. I'm also thinking that the A/F change would not show on the dyno sheet, because, the fuel is getting burned at high rpm's ... until deceleration. Then the spark dissipates and the PCM seems to still be pushing too much fuel ... causing the fuel light-off in my exhaust.
Only a theory ... anyone had this happen? I just hope my engine internals are OK. The dyno shows good numbers for my setup, however, could a change to a colder plug bring my numbers up a little and stop all the smoke and back-firing??
Car was dyno'd about a week ago. On deceleration, at about 6500 rpm, my car backfires real bad ... and it smokes like crazy (white smoke) ... had fire shooting out the back of my Borla tips from raz (fuel light-off). Could this be from running TR-6 plugs instead of TR-55's? Would running the colder plug cure this?
My thoughts are that the PCM sees more spark and dumps more fuel. I'm also thinking that the A/F change would not show on the dyno sheet, because, the fuel is getting burned at high rpm's ... until deceleration. Then the spark dissipates and the PCM seems to still be pushing too much fuel ... causing the fuel light-off in my exhaust.
Only a theory ... anyone had this happen? I just hope my engine internals are OK. The dyno shows good numbers for my setup, however, could a change to a colder plug bring my numbers up a little and stop all the smoke and back-firing??
01-30-2005, 09:10 PM
#3
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This didn't happen to me on the dyno but I was racing last night from rolls against a buddy of mine and he said everytime I let off that there was a flame that would shoot out all they way out the rear bumper and thats cause I'm running dual dumped before the axle. I'm hoping this is a tuning issue because my car does a lot of surging at idle and smells like its running rich.
01-31-2005, 05:26 AM
#4
Well, mine was surging at idle really bad and it was running super rich. I had it tuned out for the most part. It still has a slight surge, occassionally. I read it might be caused by the TR6 plugs and the .035 gap. I'm installing TR-55's again, I think. I'll post here if it fixes the problem.
BTW, I got on the interstate yesterday and it happened while floorinmg it and running it up to about 5700 rpm's. When I let off the gas, it did it again ... pop-pop-pop!!!!
Anyone know what's causing the fuel light-off in my exhaust when I decelerate? It doesn't show a rich A/F on my dyno sheets ... right on the line accross the chart @ 13.0.
BTW, I got on the interstate yesterday and it happened while floorinmg it and running it up to about 5700 rpm's. When I let off the gas, it did it again ... pop-pop-pop!!!!
Anyone know what's causing the fuel light-off in my exhaust when I decelerate? It doesn't show a rich A/F on my dyno sheets ... right on the line accross the chart @ 13.0.
