Timing advance tuning on a 2.4

[Turbocharged]

I am fine tuning the timing advance on my 2.4L. Right now I have added 1-2 degrees of timing from 4,500 - 7,000 rpms. Im peaking out at 18 degrees. What are you 2.4 guys running for timing advance? Im afraid to get carried away with advancing the timing but know that this motor should get more timing than a 2.0L (greater distance from the spark to the piston surface and lower r/s ratio).

[andymoraitis]

8.8:1 2.3 (close enough) at 12 degrees timing advance.

Higher compression motors, especially strokers don't need as much timing advance. Technically, since the VE is so much higher, lower timing is preferred to control flame front speed and optimize the combustion cycle. If I had your motor, I'd set the A/F to 11:1 on pump, dial in the boost I wanted to run and then adjust timing up or down to find the onset of 2-3 counts of knock. Once I found knock threshold, I'd back timing or boost down and run zero knock.

The key is to get your A/F in reasonable range, set the boost and then adjust the timing to what the motor will tolerate safely.

Let me know if that makes sense,

Andy

[Turbocharged]

Thanks for the reply Andy. So you peak at 12 degrees of timing advance? This must mean that you are retarding timing 4 degrees (Im assuming you are on the max airflow map; > 2.7 g/rev).

I understand the compression effects but it seems to me that it would take longer for the flame front to reach the piston due to the piston design in a stroker. I have also read technically reliable information about the r/s ratio effects on the optimum timing advance. Everything points to more timing for a smaller r/s ratio (due to the increased piston speed). I have read the converse to this on dsm forums but we all know these forums are flooded with misinformation.

Im afraid to advance timing too much because Im just under 400hp on my street setup. With pump gas there is little room for error. Im just a little paranoid.

I am also running water injection which slows the flame front a great deal.

[Turbocharged]

Ideally I would like to tune on a dyno some more, but it is simply too expensive to fine tune the timing. I already have the fuel settings tuned for my setup. I added a little timing and noticed a nice increase in power. Thats what brought me to start this thread.

[andymoraitis]

The 12 degrees I run is through a custom map. My turbo isn't pump gas friendly so to get as much boost as I can without knocking I have my chip burner pull the timing back down. Spool is actually faster with less timing, but of course everything's a trade off.

In your case, of course timing will make more power. It does for everyone. The fact of the matter is that you can run more boost with less timing on pump or more timing and less boost on pump. More power is always made with boost over timing, with the exception being race gas where you can run high boost AND high timing. I'd find the sweet spot where you want the boost and work the timing around that. It'll give you the most streetable combo.

As an aside, Dan Kasun (project_tsi) and I run carbon copy strokers. He has a 50 trim and a front mount to my Big 16G with a sidemount and runs the same timing that I do on pump gas (12 degrees).

If you're running methanol injection, that makes all the difference in the world. Crank on the timing until you see some knock and then back it down a degree as I mentioned above. I could NEVER get away with 18 degrees of timing on this motor running decent boost on pump, but you can. If you're not knocking at 18 and it's making good power, you're right in the ballpark. Methanol will give you that extra edge.

Cheers,

Andy

[Turbocharged]

Thanks, I guess I'll just keep playing around with it and eventually take it to the dyno again.

[andymoraitis]

You don't have to have a dyno tune. You're on the right course right now. If you're at 18 degrees of advance and not knocking, try upping the boost. The point is that if the A/F is right and the timing is good, you still need to find the knock threshold so that you can safely maximize the tune. Once you find 2-3 counts, back down either boost or timing until it goes away.

I'm not sure how else to put it.

[GVR4592]

A load holding dyno would take all of the guess work out of the equation and give you the best results.