quote:

38 on gas 38 on alky

Same here , tryed taking timing out with the alky carb. and the E.T. and MPH fell off.

421 sbc with 23* heads.

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Originally posted by Ron C.:

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Originally posted by Mike Beck:

Then you wouldn't approve of me using a restrictor plate to slow my car down from 9.4's to 10.0's....

........LOL...."Your killing me Small".......just pull a spark plug wire off and save the work installing anything .

Nope, that would waste fuel, I can pull a connector off an injector and not squirt any fuel in a cylinder........ Econo mode!

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Originally posted by NFC:

quote:

38 on gas 38 on alky

Same here , tryed taking timing out with the alky carb. and the E.T. and MPH fell off.

421 sbc with 23* heads.

Bandimere 5800 ft above? or Florida at or just above?

Lead is mixture.

Well with my huge dome Hemi pistons my numbers are of little value. That said.I will say that I found that degrees from best power is more consistent(not current car). Also lost almost nothing. If memory serves and getting where it doesn't at times. We lost about .01 while pulling back 4 degrees from best run setting. Alky is more forgiving with timing just as it is with jetting.

12 to 1800 ft. most of the time .
Farmington
Wilkesboro
Bristol area.

Trying to come up with a generic rule of thumb for this subject is impossible. Too many variables. As already mentioned AFR plays a significant role. If AFR after changing fuels is rich in comparison to what the engine likes as perfect then it will usually like more timing. And vica versa for the opposite scenario. So if a person goes from a really happy gas combo to a overly rich alky combo it is possible it will like more timing. So if it were me and I noticed that it liked more timing than a perfect gas setup then I'd be changing to a leaner alky tune-up and trying the original timing or less timing. If in the end it still liked more timing then that falls into the too many variables and so be it and just give it what it wants. If making the change from one fuel to the other I say start with the same timing as before and then give it what it likes based upon track or dyno testing. It's just a number like comparing tire pressure gauges.

Scott

I race at altitude. Not as high as Bandimere but still high enough to not have enough oxygen in the air. I run 37* and use a start retard to get the engine started.

My 615 with 20 degree heads liked 34 on gasoline C-16 and 27 on methanol injection. The cylinders are packed with more air/fuel mix on methanol so you get more bang for the buck. This is due to the evaporation of the fuel occuring in the intake and cooling the air coming in the cylinder down. This cooling effect is the reason the methanol motors tend to make more torque. Its like your motor breathing in cold air vs. hot air. The net result is more air and thus more fuel matched with it in the combustion chamber. That results in it needing less timing. Just my $0.02.

As I've said MANY times before, the combination of too much timing, and too much fuel will result in plugs that look good. It will also result in a car that's humidity sensitive and hard on rod bearings. (detonation) Methanol burns "longer" than gas. The time from spark until pressure is quicker than gas, in most cases. Lowering the timing with this combination (too much timing, too much fuel) will slow the car down. Lowering timing, and getting the fuel mixture CORRECT will result in quicker times, a more consistent car, and a happier engine. 999 times (or more) out of 1000 if a car doesn't need less timing on alky than it does on gas it's too rich, or the timing on gas wasn't right.


And yes, I can see the future. A BUNCH of people(1000) are going to say they run 60 degrees of timing, their cars always run exactly the same ET regardless of humidity, and their engines/rod bearings last forever. For 999 out of 1000 of them they "could" have a faster, more consistent car, with a happier engine, by simply lowering their timing and leaning their mixture.

Was is your recommend methodology for tuning Alky?

My experience seems to fall in line with what you are saying. When I first put my car on alky a few years, it made its best power on my 1050 dominator with 188 jets, 34 degrees of time.

Over the years, I have made several improvements to the carb and improved the signal. Better heads and intake work. Most of these things during the off season, so I didn't make the connection. Need to keep better records. When I would make jet changes the car didn't really seem to respond. I also seemed to have lost a bit of et(maybe a 10th). I chased my tail for a while on this, thinking something else was up with the car. But while it was slower it wanted more timing. o2 did show it was rich, but I though something was up because it didn't change, nor did my egts changes. I set the timing back to 34.

Someone recommended to me to keep going down until the car slowed down. I had 196s in there, Was going down 8 jet setting at a time, with no change in the way the car was running. With the last change down to 168, the car picked up, and the o2 finally showed a change. For the next race, I am going to knock another 4 sizes out. I do expect it to pick up some more. I would have never guess the improvements I made, required a 30 size drop in jets.

But it definitely wanted more timing when it was rich, and the et did seem to move more than it normally would with humidity changes. Plugs also looked good.

I can tell you how i do it on the dyno, you could do it at the track but it would take a whole bunch of passes.
After the engine is broke in, I move the timing to a low setting like 25 degrees. I make a pull and read the O2 and the BSFc numbers. Usually i pull some jet out and another pull. Again making sure the BSFC number keep getting better, indicating the engine is getting more efficient. I keep taking fuel away until i lose torque or the BSFC number start to go the other way.
After i have the AF at maximum efficiency, I add timing, again watching the BSFC and torque numbers. I keep adding timing until the engine maxs out.

Like i said a bunch of passes. Or you could load your engine up and head 184 miles east and get it done in a day.

Joe

This message has been edited. Last edited by: sr4440,

I appreciate the offer. I would love to play on the dyno, but between racing and vacation coming up I don't have any time to pull the motor.

The timing should be close at 34 degree based on my last dyno session. I am just going to keep jetting down until the car slows. I will sneak up on it. I usually like to make a change and run a race so I can really evaluate what the difference the change made and how it effects consistency.

Bill,
you said you are going to jet down until the car slows down. I would suggest, when it does slow down, take 2 degrees of timing out and see if it slows even further.

Joe

That is what I plan to do. Jet down till it slows, back up one step and try more and less timing and where that takes me.