Is 9-11* timing ok to race

[louvered97gtp]

I've got 9-13* timing on my 9.5:1 compression GTP with 11.75AFR and runing 12psi boost. Is there a problem running this low timing?

[johnh]

I think you'd be giving up alot of power....

[JerryH]

As a general rule, if you cannot run STOCK levels of timing on a well modded car, your tune can improve. If I can run 18 degrees of timing on a stock GTP and 18-20 degrees with 12-13 PSI boost on a nicely modded NON-intercooled GTP, there is lots of room for improvement. Factory stock is 16 to 16.5 degrees on 97-03 cars and 18 to 18.5 on 04+ cars.

It is unproven as far as I am concerned, but 3 different dyno tuners now have told me the same thing... about 2-3 HP per degree of WOT timing is "about the norm" for L67 cars. You can give yourself a free 10HP or more with a good timing tune.

But not just that... there are places in the curve you can give yourself up to 20HP for free under WOT. That's free HP sitting there unused, wasted!

I've never run less than stock timing in any case EVER on any car I have ever touched.

[louvered97gtp]

Good to know I won't blow anything up at least. But I will retune for better timing. I've been told that on higher compression engines you don't need as much timing as you would stock compression. There is less advance required since TDC is reached sooner due the taller piston. Anyone else have comments/opinions on this?

[JerryH]

If all you did is raise compression, ok... but you added cam, heads, rockers, yadda-yadda-yadda. There is NO reason you cannot run stock or higher timing... unless your tune is weak somewhere.

What else needs to be said? KR is your guide. Just don't desensitize the knock sensors.

[louvered97gtp]

Alright. I'll keep tuning with goal of 18* or better. Don't have stock timing tables since i started tuning with a mail order pcm that already had changed values.
I just wondered since I didn't see much of a difference at the track when I ran a 3.4 with 22* of timing, versus the 3.0 with 15* of timing.
I'll keep plugging away. thanks guys.

[2000Falcon]

Good info guys. I know this has all been discussed and I understand that it varies from setup to setup, however I was looking for benchmark to start with.

As noted in my sig, i'm running a 3.4", 9.5:1 pistons, Stage 2 cam, headers w/full exhaust, intake and mild head work on 91 octane fuel. I was told initially that I wouldn't have any problems running a 3.4", however i'm starting to think differently.

Give me a ballpark number that I SHOULD be able to run at WOT for advance on a NON-intercooled car. 15ish? I've got it all backed down now until I dial in the fuel, however i'll definitely consider tossing the 3.4" if I have to.

Thanks guys.

P.S. Sorry for the hijack.

[louvered97gtp]

Well it sounds like we should be shooting to use at least stock timing values at the very least. It makes sense that we don't need as much timing with higher compression pistons. Too much advance and we'd be firing closer to the piston upstroke cycle, which happens sooner on the taller/higher compression and not gaining full power potential as we would firing as we begin the downstroke.
So the way I see it. we can either:

1. Dial in a desired AFR, set desired timing (stock values min.), and select the pulley that keeps us out of KR.
-OR-
2. Select desired pulley we want to use, set desired timing (stock values min.), and adjust AFR to whatever ratio we can run prior to getting any KR.

Personally... I think I'm going to shoot for 18-20* timing on my 91 octane with my 9.5:1, and see how that works.
But this still leaves me wondering what makes more power. Higher timing or leaner AFR??

[BlackGS]

I ran 11* with the 2.8 pulley last year at the track. No problem running with that, but try to get it up to 18*, even if that means going to a larger pulley. Since I put on rockers, ported s/c and Northstar TB, I can now run 18* with the 2.8 on 93 octane. I'll try to push that to 20* with race gas.

Personally, I think higher timing makes more power than leaner AFR, but I'd like to get some dyno time to prove that out. Just don't run super rich (under 11.0). That kills power for sure.

[JerryH]

Personally, I think higher timing makes more power than leaner AFR, but I'd like to get some dyno time to prove that out. Just don't run super rich (under 11.0). That kills power for sure.

I cannot definitively tell you if leaner AFR or higher timing would give you better HP numbers, but it would not be a great difference. You do not want to go too lean becuase you could damage the pistons, same for the timing. I thing that the best answer here on a daily driver is a bit of a compromise in both directions. To do this, though, a WB is a must. A dyno would be the definitive answer giver to see your results with.

I will tell you that a smaller pulley will give you more HP over timing, though. I have dropped 1 pulley size, dropped 2 tenths in the 1/4 mile, even with an increase in WOT KR (3 degrees of KR at the time).

[louvered97gtp]

This is extreemly informative. So even though there was 3 degrees KR, the power made was still enough to overshadow the decrease in some timing due to KR? This coincides with the scans I've been getting lately, where I suspected more HP on smaller pulley with small amounts of KR vs. bigger pulley with no KR. leads me to believe I'm going down a good path.
thanks.

[JerryH]

This is extreemly informative. So even though there was 3 degrees KR, the power made was still enough to overshadow the decrease in some timing due to KR?

Most definately, yes. A drop from (let's say) a 3.4 to a 3.2 would be somewhere between 15-20 HP. A 3 degree increase in timing would be in the 3-7 HP range, so it makes sense. Where it get's interesting is when one does something like a pulley drop and lightly leans out the fueling to around 11.7-11.5 range and increases timing a couple of degrees. Instead of the 15-20 Hp increase, its closer to a 20-28 HP increase. All this assumes no KR of course.

This coincides with the scans I've been getting lately, where I suspected more HP on smaller pulley with small amounts of KR vs. bigger pulley with no KR. leads me to believe I'm going down a good path.
thanks.

Ideally you do not want KR. Small amounts of KR (3 degrees or less), are not destructive, however you will know if your choice of mods and your tuning methods are good when you get the best of both worlds.

I advocate starting off with the stock timing tables and move up from there. With the exception of tranny tuning, timing tuning is the last thing to do on the list and is done when your fueling is tuned and completed.