I will be testing a new race, 103 octane program in Bradenton this weekend. Wondering for those of you who have both - what is your timing gain ( as in how much more timing is in the race program when compared to the street program? ).

Is there some magic formula that calculates hp based on how much timing you are running or are there just too many factors involved for a simple formula?

Thanks!

D-Day

 

rob 02 in 5... 4... 3...

 

LOL

Too many variables but I think I remember seeing around 10 hp per degree of advance

 

I think I remember Rob saying he was set up with 18 degrees. I am at a pathetic 14 degrees only 2 above stock on my street program. What's the word Rob...............?

Thanks guys.

D-Day

 

My race program was set at 20 or 21 degrees, and my tuner said I needed a minimum of 100 Octane. I don't have a lot of HP so this much timing might not be recommended on a more powerful truck.

I ran this truck with this tune on it a few weekends ago. On Saturday I ran 12- 1/4 mile passes and on Sunday I ran 10- 1/8 mile passes, and I never once noticed the truck pinging. I had a mixture of about 50/50 of 110 and 93 octane.

-Mike

 

actually i have one question. What exactly is a degree a measure of? I was thinking maybe 0 degree is TDC for the piston and each degree is the acutual degree out of 360 where the spark goes off. But 20 degrees seems like it would put the piston still going up for quite a bit and hitting the flame front while rising. Obviously octane, duh, but that still seems kinda extreme. Is that what it is?

 

I think your right. I think when we are talking timing it is BTDC (Before Top Dead Center) so 20 dgrees would be 20 degrees of rotation before TDC.

 

see, i know it works, but it just seems strange. If thats really true, then it would seem that the flame is going slow enough that it mostly remains in the head while the piston is on the rise. But then it would also seem that the flame would too burn too slow to push the piston down, unless i guess it's probably exponetial, either way that just seems nuts. I would think the objective would be to have the flame from contact the top of the piston exactly at TDC so timing wouldn't really be a matter of more is better, simply finding the proper timing for the fuel you are using. And with that in mind, i thought higher octane fuel contained less energy that lower octane fuel (typically).

Guess i have some more reading up to do.

 

after reading a few of the responses all I can say is I need to take a timing 101 course.............talk about needed reading

D-Day

 

street 12 race 15

 

There is a point in spark timing where more is NOT better (Rob02's ears are burning right now

Though I'm certainly no expert, I've lurked around enough to know the basics of spark timing. Ideally, you want the mix to be fully ignited when the piston reaches TDC. This typically requires that the mix be ignited in advance of TDC, somewhere around 20 degrees BTDC for our trucks (at WOT).

The higher octane you run, the more resistant gas is to pre-ignite and therefore the closer to optimum timing you can get. I don't think higher octane rating has anything to do with a lower energy burn, though.

 

Ok, Ok
You got the timing mark idea right. 0 is top dead center and you want to fire it before it gets there.

The higher the octane number the slower the burn.
That is how you prevent detonation.

If you get it to early it is smacking the top of the piston on the way up. (Thats what breaks things)

Precise timing and correct fuel ratio is what make max horsepower and torque.

By George I think your getting it.

read this
http://www.motorcycle.com/mo/mcrob/rt-fuel2.html
No relation to our Rob

 

You got it, but a couple more tidbits to consider: The more timing an engine requires for optimum power, the less efficient the heads are. EG old style Chevy small block heads likes about 34 degrees timing. New LS-1 heads don't need as much, 31 degrees is usually more than enough. That doesn't mean our heads are that much better because we can use only 18 or so, supercharged engines can't take as much timing because the mixture is hotter than naturally asperated and more prone to detonation. The higher the rpm, the more timing is required because the amount of time before TDC is less the faster you spin it, but the flame still requires the same time to spread.

 

LMAO

 

You guys are lucky I took my Valium early last night and conked out

Dan, you know I can't always be technical with an impressive answer,
so I'll do this in a way we'll all understand it


This is low timing



This is hi timing


WHICH ONE WOULD YOU PUT OUT MORE POWER FOR