boost timing help

[4.8t]

what kind of timing do you guys run while in boost? i got the mpt70 on the built 8.8:1 4.3l. runing about 23* with 6psi right now. its a 2000 motor so it has the vortec heads and we installed the marine intake on it. i'm using the 0411 computer and 3bar tuning via hptuners. just at 6psi the thing is crazy but i want to make sure my timing is in the ballpark before we crank it up.

 

[JSM]

Re: boost timing help

22 is fairly healthy timing, at 6psi and if its not knocking should be fine. If you up the boost generally you will need to reduce timing also.

 

[4.8t]

Re: boost timing help

well i run 17-19 in my tahoe with 10psi with meth. does the 4.3l not need much timing under boost?

 

[smeagol]

Re: boost timing help

It's hard to compare the LSX motors to the stock Syty motors. The LB4 heads are by no means a high performance cylinder head and tend to detonate/preignite easily, so timing is usually very mild. The newer Vortec heads are much better in this regards, and seem to like a bit more timing.

Gotta remember, so many calculations go into timing advance that just saying 'I run 15 degrees of timing at 15psi' might not be accurate.

The stock Syty timing table has 16 degrees of timing at 3600RPM and 15psi of boost, and it rises to 21 degrees of timing at 4800RPM and 15psi of boost (just past redline). Stock chip doesn't modify that much, but custom calibrations will tweak the actual timing advance based on coolant temp, incoming air temp, etc. I put some of that in the chips I did a while back, sort of as a safety precaution. Your IC might be really heat soaked, and you might be near overheating; you wouldn't want very aggressive timing advance if you boost it in that situation.

 

[4.8t]

Re: boost timing help

It's hard to compare the LSX motors to the stock Syty motors. The LB4 heads are by no means a high performance cylinder head and tend to detonate/preignite easily, so timing is usually very mild. The newer Vortec heads are much better in this regards, and seem to like a bit more timing.

Gotta remember, so many calculations go into timing advance that just saying 'I run 15 degrees of timing at 15psi' might not be accurate.

The stock Syty timing table has 16 degrees of timing at 3600RPM and 15psi of boost, and it rises to 21 degrees of timing at 4800RPM and 15psi of boost (just past redline). Stock chip doesn't modify that much, but custom calibrations will tweak the actual timing advance based on coolant temp, incoming air temp, etc. I put some of that in the chips I did a while back, sort of as a safety precaution. Your IC might be really heat soaked, and you might be near overheating; you wouldn't want very aggressive timing advance if you boost it in that situation.

i understand iat retard and all that goodness but you have a table with base timing. thats what i'm asking about. i'm not going to set the timing at what you guys say i just need a good idea. we are using vortec heads.

why does the timing rise on the stock syty as rpm increases? is it do to poor flowing heads, cam, and intake?