OK, my L98 has a ZZ4 cam, valve job, headers and exhaust. It's no beast, but it's much quicker than before.

I do NOT have a custom program yet, still running the factory program.

I have set timing to 12 degrees based on my untrained ear. The car runs GREAT, but I'm wondering if I'm not losing power by not advancing it more. I hear about some of you guys running insane amounts of timing. Should I leave it alone, or play with it some more. I don't want to sacrifice how well the car is running for the sake of a horse or two, ya know?

Can I set to around 16-18 degrees and see what happens, or am I gonna blow something up!?!? Cou

I know a lot of the black and white, but I'm still learning a LOT of the theory.

-Thanks

 

For the record, I'm content to just leave it, unelss you guys think it's too retarded.

hehe..."retarded"

 

You will be losing some top end due to the fact your ECM will be retarding the timing 15 degrees when it sees knock. The only way to know for sure how much is to scan/datalog your car while at WOT. Base is 6 degrees. Its kinda crappy just adjusting the base timing that way because if you go from 6 degrees to 12 degrees then ALL timing tables get 6 degrees advance. In retrospect you might do better with more timing down low to help build cylinder pressure quicker and need less timing at the higher load values. Then you have to start playing with fuel too and will need a WBO2 to get the most out of your tune.

I bet your car feels super aggresive from 1K to 3500. After that it might feel smooth but its probably very slow in ramping up and will like to hang on the shifts,ect. I would put the timing back to stock and maybe find someone that can help you with editing your timing tables in your bin while you are datalogging the car. Setting timing by ear is bad in this case. The ECM detects knock before we can hear knock. If you are hearing knock its bad. The ECM will pull timing when it sees knock, but it can only pull 15 degrees timing. If you were to advance your timing to 16-18 degrees the computer might not be able to pull enough timing to control detonation. The end results could be expensive

 

Razor pretty well said it.

The L98 (with stock heads) is EXTREMELY prone to detonation/knock retard and even on a bone stock engine, they tend to pull a lot of timing. One of the ways I get power when I tune L98s is to "cap" the knock retard when in WOT.

When I do this, it has been my experience that the L98 cannot handle a lot of timing (when the KS is capped) without encountering AUDIBLE detonation.

The only EFFECTIVE way to correct the detonation problem of the L98 is to pull the heads and either clean all the casting flash and sharp edges of the combustion chamber (this will help a lot). Or, install a good set of aftermarket heads.

Without fixing the detonation problem, I generally find the KS pulls MORE timing out than add - so it is kind of like 1 step forward and 2 back.

 

I hope this is just a figure of speach and you don't think you can "HEAR" 12 degrees of timing...

 

On my car with the stock reworked heads and the ZZ4 cam on 10.5:1 compression I run about 25 degrees total timing at WOT with an AFR of 13.3-13.6:1 and AC R42TS plugs. However down low I have over 38 degrees of timing at lower RPM and lower load values. My timing table looks really different from stock but works very well as far as streetability/performance. I can add more timing in at WOT but the car does not get any faster.

 

Yes, it always possible to run much higher spark advance with low/no load. The reason is the cylinder is only partially filled and thus not as volatile. Once you start to put a load on the engine (say climbing a hill, where we have lots in BC) you must quickly reduce the timing.

I have found that at LOW rpms in WOT, the engine can barely take any spark advance. This is the most critical phase of tuning the spark curve where you are trying to get it to full advance as quickly as possible without incurring detonation. If you bring it on too fast, it will start to detonate. And if you are using an active Knock Sensor, your spark curve will be ruined for developing power.

(PS: Razor, though your compression is quite high, your total spark advance is close to what I typically find a bone stock L98 can handle. A few can go a few degrees more, but not much. Elevation is also a factor in how much spark advance an engine can handle too. At sea level, you would probably find you would need to back it off a couple of degrees more.)

 

hehe...yeah, just a figure of speech. When I was doing the work, I found that six degrees stumbles just a little. Someone here recommended NOT advancing the timing much, and suggested just enough advance to smooth out the idle, which occured at 10-12 degrees.

That's what I did.

I plan on having it professionally dyno tuned in the not tooooo distant future, so I may back off the timing a little and see how it feels.

 

Okay, I was just wondering, I tune engines on a dyno and you would be suprised how many people set their timing by EAR.... in one case he was running 50 degrees of timing..

On my EFI Small block I run 20 degrees total at idle, at cruise mid MAP situations I run 37-39, backing off as I approach 5000. under full load WOT from 2000-5000 I creep my timing down from 38-36 and about 5200 I bring it down to 35. I run 40 degrees under decel vaccum conditions under 2500.