I've been continuing to polish my tune and need a reality check. engine details in my sig. Should have just under 10.5:1 compression. My engine seems really sensitive to detonation under load. I've got plenty of AE and PE in it. When you go WOT, the AFR goes to 12 right away and gently leans to 12.5 by 5500rpm redline. I know I'm getting enough fuel to stave off detonation before it starts, hence the extra AE. I've finally got the engine to where it doesnt detonate but now my timing table seems really lame. I'm only running 27* at WOT. The heads are 60cc CNC ported LPE #119 vette castings, maybe the chambers are that good, or maybe I'm a moron. I know that my map is for me only and no one else's map will be optimal, but I'm just looking for a reality check here.

Interestingly, as I began pulling timing I started picking up power noticeably, enough that the engine leaned out. I was at 12.3 WOT AFR when I started and as I pulled the timing out and the engine was running hard it had leaned out to 13.5 AFR at WOT. then richened it back up, still had a hint of ping, so I pulled another degree and i've been fine so far.

 

If the engine makes good power, who care if the table looks weird.

I can only run 30* of timing advance with my Vortec head 305, which incedentally is 10.5:1 compression as well. The engine put down 357 RWHP and 360 RWTQ.

 

When I was running those heads (not LPE ported though), they ran best at 26 total advance.

 

Thanks a TON guys, thats exactly what I was looking for, just a little confidence. I'll keep going. No wonder it pinged like a $#%@& with the 37* that was in it to begin with.

Fast355, I'm absolutely amazed that you got that much power at the wheels out of 310 cid. Is this with OBDII electronics?

 

No that was with the 7730 ECM. OBDII electronics are nice, but they really only give you better driveability and slightly better performance due to SFI.

Getting that much power comes from getting all the details knocked out. Controlling windage, minimizing leakdown and blowby, obtaining good valve sealing, proper camshaft positioning, having the right cam for the heads, intake, exhaust, etc. Proper headers to scavenge the cylinders properly. A properly designed exhaust system to get the spent stuff out. It all has to tie togather. Without ever even having touched a dyno, it put 330 RWHP down. I found the additional 27 RHWP through experimentation. The engine did not like any more timing, but it did like me taking the PE AFR from the high 12 to the low 12. I went from 12.9 to 12.3 and gained 12 RWHP. I reaped 10 RWHP more from locking the TCC clutch @ WOT above 3,500 rpm. Finally I gained 5 RWHP consistently by lowering the coolant temperature from 220* down to 190ish, it had a 195* thermostat in it, but the fans weren't coming on until around 220* due to the factory tuning. They come on at 200*F now and run down to 195*F, with the 195* stat the engine sits at 195-200*F no matter what.

 

1MeanZ - Do you have your PE mode spark advance zeroed out?

 

Yes I do. I'm a tuning noob, so I wanted to keep things simple and not have a bunch of other timing tables jumping in and raining on my parade. So yes, on my table, what you see is what you get. To be frank, I'm not sure why I need to use the PE timing advance table. I know that is how the factory set things up, but I can't come up with any drawbacks to doing things all in the main timing table. Anyone explain the drawbacks of doing things the way I've done them?

 

The richness from PE can allow a little more spark advance before MBT and Knock. Those heads are probably knock limited, which means more timing is better until knock.
The same point on the spark MAP can be achieved at less than PE threshold as above PE threshold, so the table value should be set for stoich + no knock. The PE table should be set next to get max power + no knock AFTER the base table is done right.

 

OK, I'll have to do some messing around. I'm not sure quite how I'll get the engine way up in those tables without PE, I guess I'll just stay in lower gears and let it rev way out with no load. If I did that I might have too much advance, so I see what you're saying. The base spark map is for base fueling at whatever the commanded AFR is. Once PE kicks in, PE spark should go with it. I'll have to do more playing around.