Timing Question - How much can you advance?

[Bfisher31286]

Im tuning a 3800sc with a 3.25 pulley and supporting mods. How much timing have you guys been able to advance your engines before you start seeing knock? I am curious because Ive already added 6 degrees to the high end of the spark table and Im seeing values of 15-19.5 at WOT. The temperature here is only in the low 60s so I am afraid once it warms up I will have added too much timing.

[gtpsleeper]

Do you mean just at WOT or in general...?

[Bfisher31286]

Im talking about WOT timing. Now that the weather has warmed up im down to about 12 degrees at WOT. One thing I noticed is that if I do numerous 1500-6000rpm pulls under nearly identical ECT and intake temp sometimes I get as much as 5-6 degrees of KR while most of the pulls I get zero KR. How can you identify what is false knock and what is real? My AFR is down around 11.3 dropping to 11.1 near redline. Do the knock sensors ever go bad or get inaccurate for any reason?

[charlieRobinson]

Here is what I am running with a 3.6" and mods listed. <=0.5KR
Capture.JPG

[G_P_K]

Im talking about WOT timing. Now that the weather has warmed up im down to about 12 degrees at WOT. One thing I noticed is that if I do numerous 1500-6000rpm pulls under nearly identical ECT and intake temp sometimes I get as much as 5-6 degrees of KR while most of the pulls I get zero KR. How can you identify what is false knock and what is real? My AFR is down around 11.3 dropping to 11.1 near redline. Do the knock sensors ever go bad or get inaccurate for any reason?

IAT is pre blower so even if your IAT doesnt change the blower is still getting heat soaked and raising the charge air temperature. thats why you get knock after several runs. i would not expect that it is false knock. personally if i was you i would pulley back to a 3.4 and try and run more timing. getting up in the 16-17 degree range would be beneficial and help keep your egt down which also adds heat to the engine bay and can contribute to knock as well. the only time i would drop pulley size is if you can run 20 degrees of timing WOT. there is no reason to push the blower that far outside of its efficiency if the engine cant take advantage of the extra boost.

[Bfisher31286]

I shredded all the teeth off of 3rd gear of my trans so tuning will be on hold for a bit. It turned out the timing drop and KR that was showing up was due to transmission torque controls. Once disabled I got very little KR and was seeing around 16-14 degrees of timing at WOT. I am thinking either modified rockers or a pulley size increase will be my next step once I get my trans fixed.

And yes, disabling the trans toque limiters most likely did push more power through my trans and is likely what caused the failure. I will be upgrading to a stronger trans so hopefully it can take the torque.

The engine is in a 86 Pontiac Fiero and the original 4 speed manual trans. Torque controls were disabled due to the fact that they were meant for an auto.

[charlieRobinson]

Dang, man. sorry for your loss.

Let us know when you are back on the road.