[TurboQueef]

HI..

I am trying to tune for 110 octane... I had good luck when the temps were cold (30's) but I have developed a miss-fire in the warm weather.

The miss-fire happens at 5600 RPM and when it happens I get out of the throttle rite away. The data log looks fine up to when I get out of it (AFR = 12 to 1, timing at full dynamic advance etc)

I am running Citco 110 leaded fuel, stock spark plugs, K&N Typhoon, Megan 3" catt-less exhaust. Last week I ran 12.57 @ 108 with the miss fire (not so pronounced at the track, very noticeable in a 4th gear pull).

I have tried tuning the AFR and timing to get rid of the miss-fire but no go.

I just checked compression on warm engine I get 140 even on all 4 cylinders.

Any ideas?

Thanks,

Jeff
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[crystal_Imprezav]

Hey Jeff, it may be that funky timing you have in the low load upper rpm's, maybe... Other than that, I would need to see the map or log to see if I could spot anything odd. Common causes of misfires between shift would be vent to atmosphere bov's and/or (so i've heard) venting to atmosphere catch can's. Check for leaks that are preventing unmetered air from being metered.

[TurboQueef]

Originally Posted by crystal_Imprezav

Hey Jeff, it may be that funky timing you have in the low load upper rpm's, maybe... Other than that, I would need to see the map or log to see if I could spot anything odd. Common causes of misfires between shift would be vent to atmosphere bov's and/or (so i've heard) venting to atmosphere catch can's. Check for leaks that are preventing unmetered air from being metered.

Hum... maybe... what plugs are you running? I wonder if it may be due to them.

Here is a log of one of the data pulls that experienced the problem:

http://n8rws.com/Miss.zip

[crystal_Imprezav]

Im running 1-step colder plugs but I am going to switch to 2-step colder plugs soon.

[TurboQueef]

Originally Posted by crystal_Imprezav

Im running 1-step colder plugs but I am going to switch to 2-step colder plugs soon.

I wonder if the leaded fuel is messing with the stock plugs. I am going to install some copper NKG's tomorrow, hopefully this will cure the problem.

You ever do a compression test? If so, what number did you get?

jb

[crystal_Imprezav]

Check your plugs, I read your post wrong the first time. I thought you said it only happened when you lifted off the throttle. Looking at the log, DA is full but it dropped .5* of timing.

[crystal_Imprezav]

Also when was the last time you cleaned your MAF?

[TurboQueef]

Originally Posted by crystal_Imprezav

Also when was the last time you cleaned your MAF?

Ha.. never cleaned the MAF... never heard of doing it.. what is the process?

The plugs look OK... tough to say due to the lead deposits due to race fuel. I still wonder if the stock plugs (Iridum's) can take lead

[crystal_Imprezav]

You sure it isn't just your clutch slipping? Throttle says 100% however your rpm's are jumping around. This is usually what a clutch slip looks like in a log.

[TurboQueef]

Originally Posted by crystal_Imprezav

You sure it isn't just your clutch slipping? Throttle says 100% however your rpm's are jumping around. This is usually what a clutch slip looks like in a log............

Hum.... did not notice that before, I don't think the clutch is slipping though... I think this is where it is miss-firing

[jaxscuby]

also your afr are a bit lean..
at 4584 rpm 11.82 afr
at 6576 rpm 12.32 afr

try to flatten your afr..
4k to redline ~11.5

your boost tapers properly.

yes i know it is a 110 octane map, but if you're getting a misfire
it is not going to hurt..compared to melting a piston..

[crystal_Imprezav]

Misfires are typically from running rich... He is exactly where he should be for 110 leaded

[TurboQueef]

Originally Posted by jaxscuby

also your afr are a bit lean..
at 4584 rpm 11.82 afr
at 6576 rpm 12.32 afr

try to flatten your afr..
4k to redline ~11.5

your boost tapers properly.

yes i know it is a 110 octane map, but if you're getting a misfire
it is not going to hurt..compared to melting a piston..

JAX... thanks for the info... actually, I am happy with the current AFR... I think the problem was my plugs. I installed the copper version NGK and gapped at .028. Miss-fire is gone.

[TurboQueef]

Originally Posted by crystal_Imprezav

Misfires are typically from running rich... He is exactly where he should be for 110 leaded

Hey Jeff... I expect delivery of 10 gallons of VP Motorsport 109 tomorrow... did you ever hear about it?

"Produces more power than any other unleaded fuel. Recommended for higher boost applications with CRs up to 11:1 or naturally aspirated engines up to 13:1.
• Color: Clear
• Motor Octane: 101
• R+M/2: 105
• Research Octane: 109
• Oxygenated: Yes
• Specific Gravity: .722 at 60° F"


Source: http://www.vpracingfuels.com/vp_01_fuels.html#specialty

[crystal_Imprezav]

J, I personally have never gotten the results I have experienced with leaded fuel vs. unleaded fuel. The numbers and tune I got out of 110 leaded far exceeded those of 110 unleaded. My guess is that, after doing a few runs and tunes on the unleaded gas, you will be heading back to the station for the oh so good lead