Pulley Drop Vs Higher Timing (Custom Tune)

To add to more of the timing discussions, based upon my own experiences:

-Timing in an N/A car, I like to increase as RPMs increase. N/A cars are less prone to knock the higher the rpms with breathing mods. With restrictive exhaust, its usually best to keep its timing fairly flat
-Timing in a forced induction car, I like to keep flat from 4000 rpm and up. Increasing as rpms increase will typically increase KR, if your car tends to boost stack. It can be worth combating high rpm KR with a little extra fuel rather than reducing timing as rpms climb. If your boost increases more than 2psi over the mid-range, you have a lot of boost stacking and you may need to reduce timing 1* over 5600rpm and you'll need to address the restriction between your LIM and your exhaust tip to get the best performance.
-Timing is worth good power in the midrange around peak torque, but that's also where peak cylinder pressure is. Too much timing in the midrange is asking for a piston chunk or a blown head gasket.
-The above mentioned correlation between added timing and factory KR attack rates. If you're running a consistent 3* of KR for example, and you're running 17-18* timing with that 3*KR because you're running 20-21* overall timing advance, that's a big difference

Overall, timing is *free* power until you break something and timing can do that if you get greedy. I don't take that much risk with the supercharged 3800s that I tune when it comes to timing advance.

I see about 7 psi until about 5000 rpm then boost goes up to 9 psi by 6000rpm, is that considered "boost stacking" I thought it was normal running a stock cam.

I start off pe with 11.2 and ~18 degrees grandually riching up to 10.8 with 16* by the end of the quarter. Does that sound about ideal?

1.5-2psi is fairly normal. Anything over 2psi difference between 5000 and 6000rpm could use some more breathing.

I like your AFR.

thanks, do you think I'll benefit going to a 3.4 over the 3.5 I have?

man i haven seen that kinda AFR for a while now...

if there is no KR then I wouldn see why not...

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Originally Posted by gtpsleeper

man i haven seen that kinda AFR for a while now...

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Why is that? E85?


I don't see knock, I have it tuned pretty damn good, right on the verge of knock. I might see .5-1* every now and then but that's it.

Yes and obviously you can get away with a lot more on E85 or 110 leaded. Those fuels will tremendously reduce the chance of knock, allowing you to get very aggressive in timing while leaning out the afr. Some guys brag about how much timing and the low pulley size they are running but are hesitant to tell you what fuel that was on. A lot of people fail to realize this and think they can run such and such pulley and timing because "he" did it. Or fail to realize the geographic differences and ability to adjust their tune year round.

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Originally Posted by jdmgtp

Why is that? E85?


I don't see knock, I have it tuned pretty damn good, right on the verge of knock. I might see .5-1* every now and then but that's it.

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ya e85... and ive been intercooled for a while too so it was usually around 11.8 for a while then up to 12.6 right now... holding it backfor the tranny TBH