Plugs died on a pass
Plugs died on a pass I got to hear some thoughts on what happen to me today.
We was going to run the car and desided to lower the fuel jet so i could pick the stand alone fuel pressure a few psi. I needed a new set of plugs and all i had was some #11's was saving for the 500 shot and i couldnt get any more plugs on a sunday so i went with the 11's
Ok i start off with what i thought would be a good starting point but the first pull it was pig rich (we was running 1/8 mile) and this is with a 34n direct port
2nd pull i took some fuel out and it got better but the plugs looked cold and rich so i threw 2* more timming in and pull some more fuel and the car made a turn around and ran the best 1/8 pass todate so i threw 1 more degree of timming at it and pulled alittle more fuel, The pass looked good untill 7400 rpm and witch at that time it back fired and shut off.
We pulled the car back to the pits because it wouldnt start and afetr going over everything that i thought could be rong with it and not finding anything (the car would try to start it just spun like there wasnt any spark) i pulled the plugs and was blown away with what i saw, ALL 8 plugs where **** black and dead (they wouldnt fire at all) They where not burn or blown up just dead
How does all 8 plugs go dead all at the same time on a 7000+ rpm pass
For the record someone at the track had a new set of #8 plugs and witch i installed and the car runs perfect.
We was going to run the car and desided to lower the fuel jet so i could pick the stand alone fuel pressure a few psi. I needed a new set of plugs and all i had was some #11's was saving for the 500 shot and i couldnt get any more plugs on a sunday so i went with the 11's
Ok i start off with what i thought would be a good starting point but the first pull it was pig rich (we was running 1/8 mile) and this is with a 34n direct port
2nd pull i took some fuel out and it got better but the plugs looked cold and rich so i threw 2* more timming in and pull some more fuel and the car made a turn around and ran the best 1/8 pass todate so i threw 1 more degree of timming at it and pulled alittle more fuel, The pass looked good untill 7400 rpm and witch at that time it back fired and shut off.
We pulled the car back to the pits because it wouldnt start and afetr going over everything that i thought could be rong with it and not finding anything (the car would try to start it just spun like there wasnt any spark) i pulled the plugs and was blown away with what i saw, ALL 8 plugs where **** black and dead (they wouldnt fire at all) They where not burn or blown up just dead
How does all 8 plugs go dead all at the same time on a 7000+ rpm pass
For the record someone at the track had a new set of #8 plugs and witch i installed and the car runs perfect.
Colder plugs tend to wet-down and foul much quicker than a warmer plug.
I've seen this happen before and 9 times out of 10 it's a problem with the part-throttle and idle tuning not being agressive enough. Running race gas all the time makes this a lot worse.
For a cool running engine you need to run VERY lean and with as much spark advance as you can get away with during idle and part-throttle so as to keep the plugs clean.
By lean I mean as lean as you can get away with before lean misfire. Every setup is different but I usually run between 15.5:1 and 16.5:1 AFR - depending on engine loading of course.
For part throttle as you start loading the engine during driving the AFR will need to drop back down a step or two - but 90% of your driving is unloaded or extremely light load that will tolerate leaner AFR's.
This takes a little while to get right in the VE table but is worth it.
For LSX engines a situation like running race gas and using a large nitrous shot pretty much necessitates using an Open Loop tune which makes controlling the AFR like I describe possible.
I hope this is on track and is helpful.
I've seen this happen before and 9 times out of 10 it's a problem with the part-throttle and idle tuning not being agressive enough. Running race gas all the time makes this a lot worse.
For a cool running engine you need to run VERY lean and with as much spark advance as you can get away with during idle and part-throttle so as to keep the plugs clean.
By lean I mean as lean as you can get away with before lean misfire. Every setup is different but I usually run between 15.5:1 and 16.5:1 AFR - depending on engine loading of course.
For part throttle as you start loading the engine during driving the AFR will need to drop back down a step or two - but 90% of your driving is unloaded or extremely light load that will tolerate leaner AFR's.
This takes a little while to get right in the VE table but is worth it.
For LSX engines a situation like running race gas and using a large nitrous shot pretty much necessitates using an Open Loop tune which makes controlling the AFR like I describe possible.
I hope this is on track and is helpful.
