for the tuners on here.....

based from tuning experience, how much advanced timing were you guys able to go on 93octane without detonation??? 11.xx compression...

 

depends on what the engine wants. More timing doesnt necessarily mean more power and different tuning systems have different representations of timing. The table timing is not what is actually being sent to the ecu unless you are using a standalone management or something that is not based on honda code.

for instance, on my h22 (10.6:1) with Crower stage 2 cams, the engine liked 31* of table timing. Neptune can log actual timing and it came as high as 40* BTDC in the upper RPM ranges. This was on 93 octane. Obviously with higher compression, i would not want to run that kind of ignition timing because that is very close to meeting Peak cylinder pressure before the piston even reaches TDC.

 

where does this discrepency come from, between table timing and actual? on the honda ecus that is.

 

different compensations for IAT, ECT...etc based upon what the ecu feels suits the conditions best. You can manipulate these compensation values with most modern tuning programs. But the ecu is always going to be changing the value you see at the table unless you turn off ignition advancements completely or per a mbar/vac threshold.

 

ah right, i totally forgot aobut ignition trims, haha. its been a while.

 

There is a huge variation from one engine to the next. The more efficient the head, the less timing it will require. For instance, the D16Z6 uses 10-15 degrees more timing than the Y8 in different parts of the map.

Advance timing is not a good thing or a bad thing except that the less you NEED, the better. You want combustion to peak just after ATDC where you have the most mechanical advantage. If it peaks before, you're fighting the piston on the way up. This can either blow your engine up worst case scenario or hurt your power best case scenario. If the combustion peaks AFTER, then you're not reaching your full power potential.

What you do is put your car on a load-bearing dyno, choose a load/RPM cell and lock the dyno, hold the throttle very steady, start with a little bit of timing and slowly advance it. You should see torque increase, then level off. Back it off just slightly from the point where it levels off. If this is heavy load, back it off even more for safety. Or use knock feedback and let the ECU back it off. Interpolate the rest of the map between all the points. It helps to understand how timing works. Max torque is peak efficiency and requires the least timing, then you advance timing in each direction away from it. You also increase timing as RPM increase but within a certain amount of safety margin depending on your setup.

 

Here is a helpful hint: Look at the factory calibrations to get an idea :-)
Also, timing in your engine management system doesn't mean anything if it's not synced to your distributor.


Modified by mtber at 1:46 AM 4/10/2008