cam tuning help
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Teching In
Joined: Apr 2011
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cam tuning help just installed my comp cams 280xfi, and WOW did it make a difference... however in the low rpms the tune is off, i acheived a great idle with 30 degrees advance... the car just slightly hesitates in throttle response below 2k, and wont cruise in 6th under 1500 (55mph) w/o slight surge unless the car kicks out of closed loop which it does? and car runs great (rich at 13.8-14.2)
any ideas/suggestions?
96lt1 m6
any ideas/suggestions?
96lt1 m6
That's a little rich for cruising, but not rich enough to create any problems. You want 14.7-15.0 for optimum fuel mileage. Need to adjust MAF tables to take out a little fuel. Are you getting your AFR from a wideband?
Why would it "kick out" of closed loop? It should stay in closed loop until you kill the motor.
Why would it "kick out" of closed loop? It should stay in closed loop until you kill the motor.
Thread Starter
Teching In
Joined: Apr 2011
Posts: 45
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thats my point, it runs better with the richer a/f.. yes using wideband. when its in closed loop it surges and for some reason it kicks out of closed loop after ten minutes or so and runs great
the surging is just barely noticeable through the gear shift as it lightly stumbles
the surging is just barely noticeable through the gear shift as it lightly stumbles
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Teching In
Joined: Apr 2011
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.. i think you guys are missing the point... it idles great, it drives great when in open loop and rich... when in closed loop and swinging around 14.7 it doesnt drive AS well... with light throttle it commands 40 degrees, is that too much?
I've tuned about 4 different LARGE cams now and have yet to see ANY improvement in the idle quality (vacuum) running more than about 32º timing. The last was on my car with the HSR and a 262/265 109.75lsa cam. The longer runners want more timing and generally don't idle as well with big cams... Well it runs the best at 32º of ACTUAL timing verified by timing light, not just some arbitrary number you plug in the computer at the mercy of the cam grinder's accuracy and timing chain slop. It makes about 4.5" of vacuum there, and did about 4" with only 28º.
Now, if you want to eliminate surge you need to LEAN the car out, I've run 1.05 lambda with good success at cruise and had ZERO surge problems with a 240/252 107lsa cam and a 6 speed with only a 4.11 gear and 28" tires. I never see a benefit running more than about 38º of timing at cruise, the motor just doesn't need it with the compression I run and fancy AFR chambers.
Now, if you want to eliminate surge you need to LEAN the car out, I've run 1.05 lambda with good success at cruise and had ZERO surge problems with a 240/252 107lsa cam and a 6 speed with only a 4.11 gear and 28" tires. I never see a benefit running more than about 38º of timing at cruise, the motor just doesn't need it with the compression I run and fancy AFR chambers.
I am at 37 degrees and I adjusted the closed tps and open tables to match so there's no transition problems. I added until I stopped seeing the map value drop.
I also found adding timing and smoothing out the tables at cruise smoothed it out the most. I leaned it out a bit and it's almost completely gone.
I also found adding timing and smoothing out the tables at cruise smoothed it out the most. I leaned it out a bit and it's almost completely gone.
I've tuned about 4 different LARGE cams now and have yet to see ANY improvement in the idle quality (vacuum) running more than about 32º timing. The last was on my car with the HSR and a 262/265 109.75lsa cam. The longer runners want more timing and generally don't idle as well with big cams... Well it runs the best at 32º of ACTUAL timing verified by timing light, not just some arbitrary number you plug in the computer at the mercy of the cam grinder's accuracy and timing chain slop. It makes about 4.5" of vacuum there, and did about 4" with only 28º.
Now, if you want to eliminate surge you need to LEAN the car out, I've run 1.05 lambda with good success at cruise and had ZERO surge problems with a 240/252 107lsa cam and a 6 speed with only a 4.11 gear and 28" tires. I never see a benefit running more than about 38º of timing at cruise, the motor just doesn't need it with the compression I run and fancy AFR chambers.
Now, if you want to eliminate surge you need to LEAN the car out, I've run 1.05 lambda with good success at cruise and had ZERO surge problems with a 240/252 107lsa cam and a 6 speed with only a 4.11 gear and 28" tires. I never see a benefit running more than about 38º of timing at cruise, the motor just doesn't need it with the compression I run and fancy AFR chambers.
