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Author Topic:   gas versus alcohol
jrf3
Dirt Full Roller

Total posts: 28
posted October 20, 2004 01:51 PM  
Wondering if anyone knows what on an avererage the differences are between gas and alcohol is. Also advantages for one or the other

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted October 20, 2004 02:24 PM  
More torque with alky, which equals more HP in most cases over gas. Alky runs cooler than gas. But you burn almost twice as much alky as gas which can change your car more during a race, and some say gas is smoother and easier to drive. Alky is corrosive and is hard on parts if not taken care of.

dogwalker
Dirt Full Roller

Total posts: 65
posted October 20, 2004 02:27 PM  
The benefits of running alcohol are that the engine runs cooler, likes a lot of compression (often resulting in more horsepower). The bad side is you burn a heck of a lot more alcohol than you do gas and as a result, your rear % decreases much faster than running gas. Also use larger fuel lines for alcohol than gas ect. I'm sure there's a ton more things others can mention.

dirtywrench13
Dirt Freak

Total posts: 324
posted October 20, 2004 03:21 PM  
alky burns at 7 to 1 and gas burns at 14.7 to 1, so you use twice as much akly.
fuel lines are bigger,but it has a considerabley higher flashpoint and is actually safer to store than gas.but it draws moisture, and causes corrosion.

Kromulous
Dirt Forum Champ
Total posts: 796
posted October 20, 2004 04:49 PM  
Overall whats the best in your opinion?

I'm leaning towards gas, we run a small bore block there better with the heat, and gas seems easier to set up and maintain with more of a cushion for error. As well the fuel load deal, plus it only makes about 40 ft-lbs more torque and its already easy to over power a track with a mod.

Maybe my thinking is skewed not sure, alky seems abit touchy to me at times.

ss#2
Dirt Forum Racer

Total posts: 80
posted October 20, 2004 05:45 PM  
gas is better ..rear % is more important

KEEP THE BITE ON THE TIRES

x13jc
Dirt Freak

Total posts: 390
posted October 20, 2004 06:40 PM  
My opinion?

I ran alky and never noticed much if any increase in power. I was told it was more effective on a true "claimer" engine, less power your engine makes the more difference the alky makes. Thats just what I was told. There is less room for error with alky. The fuel system has to be near perfect for proper results. As for it running cooler?? I never seen it. Mine wouldn't even run good until it got to at least 200 degrees. Yes you burn twice as much alky as gas.

So I went back to gas and run 180 degrees most of the time. I like the fact that my rear % doesn't decrease so much throughout the race. The gas is easier to find around here. I don't have to worry about draining my fuel bowls and lines after every race weekend so they don't corrode over. Its just one less headache in my opinion. I also can't stand to be around burning alky!!! Harder to adjust the timing and carb. when your crying. LOL!!!

smayo964
Dirt Maniac

Total posts: 194
posted October 21, 2004 05:17 AM  
From what I've studied and read from back in the karting days is that alcohol is better for the lower to mid-range power bands. It has a tremendous advantage over gas in the lower ranges due to the lightness of the fuel and the ability to initiate fuel flow quicker. Down side is since it's lighter and more compressible, you burn twice as much (give or take) over gas and need higher compression ratios to take advantage of engine cooling. But, when the engine enters the higher RPM range, gas creates the same horsepower and torgue curves as alcohol. Advantages are less burn off and more stable weight distribution. Main disadvantages are slower initial fuel flow, lower RPM power values, and heat.

Kromulous
Dirt Forum Champ
Total posts: 796
posted October 21, 2004 07:09 AM  
Engine builder says there is a large diference in alky cams and gas cams. He told me exhaust duration on @.050 on the Alky cams needs to be under 260 to take advantage of the alky fuel. No idea personnally but thats what i have leaned, and says he can show it to me and prove it on a dyno.

I'm leaning towards gas myself, alky seems like to much trouble. Back in our Karting days it was easy to deal with, just dump it in change the jet to the day and roll. Dump some Nitro in if you could get away with it and that was it.

dgb
Dirt Full Roller

Total posts: 70
posted October 21, 2004 07:46 AM  
I've read the same thing about the cam profile differences. Last year steve hendren mentioned cam profile as being pretty particular for getting the most from alcohol. I wish he, or someone, would elaborate on that- So does the alcohol generally require more or less exhaust duration as compared to comparible gas engines? (I'm assuming less kromulous?) What other general trends are there when camming an alky engine compared to gas? Other than more compression, what other things need to be accounted for to get the most from alcohol? Am I correct in assuming more runner volume is needed since the increased volume of fuel is going to take up some space in the mixture? Any dyno guys care to elaborate? thanks

Kromulous
Dirt Forum Champ
Total posts: 796
posted October 21, 2004 07:59 AM  
I've read exactley what you said (Dgb), less exhaust duration and more port runner volume, particularly with 23* degree heads when running alky.

Other than that i dont know. Would like to hear some other engine builders opinions myself, although i do trust our guy enough to believe what he tells me without proof positive.

jws
Dirt Maniac

Total posts: 115
posted October 21, 2004 10:31 AM  
I've gone back and forth several times and I am currently sticking with gas. In my mind the only reason to run Alky is if you need the extra power. It will make 4 to 7% more power across the board. If you are running a large hooked up track or are trying to get by on a really weak engine then maybe you need the Alky. Gas will react smoother and slightly slower making the car much easier to drive on a dry-slick track. You will probably need a 24 or 26 inch radiator with a good shroud and solid fan to keep it cool.

jrf3
Dirt Full Roller

Total posts: 28
posted October 21, 2004 01:33 PM  
Wanting to know some more details from the guys that are running gas. What kind of fuel are you running, how big is your fan and how many blade, also what brand of carb is being used and about how big of a jet for like a 406 motor. How much timimg to run and also if I can use my kse pump and just clean everything out and switch over from alcohol.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted October 21, 2004 02:27 PM  
We switched to gas this past year. We are currently running Sunoco Supreme. 1:1 pulley setup with GM 4 blade fan #405442 fan cut down to about 17" and the biggest radiator we could fit in front of it with an oil cooler. We keep it clean and I blow it out before the feature and rarely see more than 200-205 on the track. Timing just like most small blocks around 36 degrees, aftermarket holley HP based carb with roughly 76 jets. KSE will work fine, jsut readjust your pressure because you dont need as much on gas.
The biggest change is the carb. I know guys that will change back and forth depednign on the track and condditions. Just change the carb, and fuel and reset pressure and your done.


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