Spark Plug Gap Tuning
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
Spark Plug Gap Tuning
Hey, for those of you who have dramatically reduced your spark plug gap, how much timing (if at all) did you pull from your tune, and in which quadrant did you pull the most?
I've got a nasty misfire that has developed since the plug gap switch from .050 to .035
o2's are reading super lean, but I suspect that I am actually seeing a super rich condition since they switch between 15+ a/f to 9.8 a/f in less than a second.
Thanks!
I've got a nasty misfire that has developed since the plug gap switch from .050 to .035
o2's are reading super lean, but I suspect that I am actually seeing a super rich condition since they switch between 15+ a/f to 9.8 a/f in less than a second.
Thanks!
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
one second may night seem like alot of time to you or me, but your computer will make thousands of adjustments in that one second time. Are you using a wideband? I would trust it, if its putting in a major swing check your tables.
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
Running FAST wideband
I would agree with the thousands of adjustments, but the o2 sensors keep pulling fuel even though the target a/f is 12.8. not sure, I really need to get the fp gauge on to see if I have delivery issues, because this is truly bizarre.
I would agree with the thousands of adjustments, but the o2 sensors keep pulling fuel even though the target a/f is 12.8. not sure, I really need to get the fp gauge on to see if I have delivery issues, because this is truly bizarre.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
drochau,
I would say your pumps aren't handling the demand... if it is giing you a high speed miss with .035 gap you're definatly leaning out...
I'm not sure about the FAST system, but with the traditional ECM at WOT you are in open loop and the O2's are along for the ride so to speak... I would say it's a delivery problem, what size injecotrs are you running? FMU ?
I pulled about 3-4 degrees from my 95-100 KPA above 4000 rpms... I'm running programed about 25 degrees ... Also unless you are running water injection or intercooling of some sort, I would think 12.8 to be a touch on the lean side....
Mo
I would say your pumps aren't handling the demand... if it is giing you a high speed miss with .035 gap you're definatly leaning out...
I'm not sure about the FAST system, but with the traditional ECM at WOT you are in open loop and the O2's are along for the ride so to speak... I would say it's a delivery problem, what size injecotrs are you running? FMU ?
I pulled about 3-4 degrees from my 95-100 KPA above 4000 rpms... I'm running programed about 25 degrees ... Also unless you are running water injection or intercooling of some sort, I would think 12.8 to be a touch on the lean side....
Mo
Last edited by Mo_Bandy; Sep 20, 2005 at 12:01 AM.
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
Mo,
I'm running the Racetronix set-up with a 255 lph. The injectors are freshly reconditioned (witchhunter) Bosch #42. I don't think I'm running out of injectors, they're not even coming close to 60 percent of duty cycle. I'll mess with the timing map, it was set for extreme performance and the gap change may have pushed it too far. Let me know if you have anymore thoughts.
FMU is disabled, FAST should be controlling the #42 injectors enough to not need it. In fact I plan on pulling the FMU out as soon as I reconnect my fuel pressure gauge.
I'm running the Racetronix set-up with a 255 lph. The injectors are freshly reconditioned (witchhunter) Bosch #42. I don't think I'm running out of injectors, they're not even coming close to 60 percent of duty cycle. I'll mess with the timing map, it was set for extreme performance and the gap change may have pushed it too far. Let me know if you have anymore thoughts.
FMU is disabled, FAST should be controlling the #42 injectors enough to not need it. In fact I plan on pulling the FMU out as soon as I reconnect my fuel pressure gauge.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
Hi drochau,
Yeah you have plenty of injector. Uhm I would say definately get your fuel gauge hooked up that should tell you whether your hitting the numbers or not...
Are you getting any spark knock?
Mo
Yeah you have plenty of injector. Uhm I would say definately get your fuel gauge hooked up that should tell you whether your hitting the numbers or not...
Are you getting any spark knock?
Mo
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
The module isn't reading any knock. I'm off to hook up the fp gauge. I had ALOT of timing in the last tune, probably a function of the plugs I was running. I'm backing the timing off right now to see what happens. Let me know if you think of anything else.
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Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
Im' wondering if my knock module is disabled. Will put on the to do list, because I've never seen it knock. I only have an MSD coil, otherwise stock ignition.
I chose the NGK TR7s and gapped them to .035. I did notice a hit in performance when they first went in. Maybe the wrong plug was installed? The part number was BP7EFS which I understood from http://www.ls1tech.com/forums/showth...92#post2089592 as being the TR7s.
Car ran decent before the plug change, though they were old and were the AC delcos with the puck in the middle
.
I chose the NGK TR7s and gapped them to .035. I did notice a hit in performance when they first went in. Maybe the wrong plug was installed? The part number was BP7EFS which I understood from http://www.ls1tech.com/forums/showth...92#post2089592 as being the TR7s.
Car ran decent before the plug change, though they were old and were the AC delcos with the puck in the middle
.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
i started with the TR7's now I'm running 7401 champions... @ .035
you should be seeing "some knock" especially between shifts... maybe a couple degrees...
Are you running water injection? Oh wait you said you were intercooled right?
mo
you should be seeing "some knock" especially between shifts... maybe a couple degrees...
Are you running water injection? Oh wait you said you were intercooled right?
mo
Supporting Vendor
Joined: Oct 2004
Posts: 761
Likes: 68
DROCHAU, It is my opinion that you need a 'CDI' system like the Crane or MSD with a good set of "heli-coil" wires. If you are misfiring at higher RPM ranges this will affect your A/F ratio readings. Either plug, NGK-TR7 or Champion 7401, is OK: TR7 & 7401 are equivalent heat range wise. Above 4,000 RPM with a blower the ignition coil (stock or aftermarket) cannot charge fast enough, given the 12VDC coil supply, to fire the plug. A good 'CDI' system raises the coil supply voltage to 400+ VDC, thus enabling even the stock coil to easily fire the plug.
Once the mis-fire is fixed you can go back to tuning the A/F ratio without the 'weirdness'.
Regards Greg
Once the mis-fire is fixed you can go back to tuning the A/F ratio without the 'weirdness'.
Regards Greg
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
Thanks greg. Your advice as always is taken with a great deal of respect. I intend to install MSD this winter during my pulley up project. For now though, it seems very odd to me that everything was hunky dory before the plug change and now I seem to be seeing a loss in performance. I didn't have any misfires before the plug change...
Last edited by drochau; Sep 21, 2005 at 05:53 PM.
Thread Starter
Racer
Joined: Dec 2004
Posts: 427
Likes: 0
From: Albuquerque New Mexico
For those who were following this thread.
Big D'OH on my behalf. Apparently I bent up the fuel level arm when reinstalling my fuel pump assembly. Three bars of fuel actually meant "on fumes" since I filled her up last night and she took 18.5 gallons . Fuel pressure gauge went on and everything looked kosher and she ran fine.
I'm still fine tuning, but for the sake of the topic I thought I would share that the fuel was simply out and it wasn't a misfire at all, but fuel starvation.
Big D'OH on my behalf. Apparently I bent up the fuel level arm when reinstalling my fuel pump assembly. Three bars of fuel actually meant "on fumes" since I filled her up last night and she took 18.5 gallons
. Fuel pressure gauge went on and everything looked kosher and she ran fine.I'm still fine tuning, but for the sake of the topic I thought I would share that the fuel was simply out and it wasn't a misfire at all, but fuel starvation.
