what is the reason big cid motor make less HP on
methanol them gas I thinking it may have something to do with low rod ratio piston does not dwell as long at TDC
anybody 2 cents

Can’t get enough fuel thru it..

Something about BTU's in gasoline. I am right there with ya. My gas is .06 quicker than my alky. It's pretty equal down low but the gas runs 4 mph more.

Whomp
Carb's have come a long way and I would say they can supply enough fuel, even if two are needed but they still don't seam to deliver the quality of fuel needed due to the amount the motor requires to develop the high HP numbers. But I will say that a properly set up injection system will make as much if not more power and provide faster et's than a gas carb combo due to the quality of fuel provided.

quote:

Originally posted by 27Keith:
Something about BTU's in gasoline. I am right there with ya. My gas is .06 quicker than my alky. It's pretty equal down low but the gas runs 4 mph more.

Not really sure what your saying here, ya gas has more BTU;s than alky but you are putting almost twice as much on the motor. If you have two motors that make the same power, one on gas and one on alky, the alky combo will be faster.

have tried alky 3 times over the last 20 years ....(on engines 588CID up to 638 CID) (big Chief heads) ....all over 15-1 compression ...... 1 carbureted (George Rupert setup ) and twice with injection ( toilets once and Terminators once ) .... NONE would run as fast as my gas carbed setups on the same engines .... I had people who know , sell, and tune these exact systems trying to help and it was still slower ...maybe its the spread port heads ? , maybe if I had stayed with it longer it would have come around , who knows but I gave up after 3 tries and stayed with gas ...

This message has been edited. Last edited by: Paul S/Q,

I have run a Rons Terminator and a gas 1050 carb on my present car and engine. A 565

It ran slightly quicker and faster with the Terminator...maybe .02 and 1-2 mph faster at most.
Short times all faster with Terminator

I ran a gas carb and an alcohol carb on another engine with no other changes.....only a 509 and the alcohol carb was at least a tenth quicker..

It was the same carb and was converted to alcohol by APD and it was a Stinnett 1050

I have another APD alcohol carb but never ran it. An 1150

For the original question I am not exactly sure why some larger, more radical motors run better on gas. We do know that the cam has something to do with it, overlap, duration etc. It could be as simple as it needs more spark to fire it off. I know that most of the Alcohol dragsters and Nitro cars use huge magnetos to fire it off and most of us use basic MSD ignitions. Could be a combination of those and other things. I would like to know and if we knew why we could probably tune the alcohol to run better. I do know for a fact alcohol picks up most motors quite well and will even work great on low compression motors. I have ran it as low as 9.4 with great success. For those who say you MUST have 14 to 1 compression to run alcohol is simply not true. That is one of the alcohol myths that someone started and has not gone away. Note I am not saying lower compression is better for a race car it is not, what I am saying is alcohol will pick up a low compression motor big time.

As for some of the other things mentioned Yes, gas does have more BTU's but you use more alcohol so that is not the problem.

As for carbs vs Injection from my experience the injection will always be faster but carbs are easy to tune, start better and use less fuel.

In my opinion the reason for that is a carb has to have the boosters in the way to draw fuel from the float bowls so there is always some vacuum. No air moving past boosters, no vacuum no fuel. Simple.

Injection does not have anything restricting airflow when wide open so the motor takes in all the air it can use and we try to add the fuel to get it to right ratio.

For Paul S/G I have to say go with what works for you. My experience alcohol has always been significantly faster and going from alcohol carb to injection has picked up another .10 to .15 on top of that.

quote:

Originally posted by Curly1:
For those who say you MUST have 14 to 1 compression to run alcohol is simply not true. That is one of the alcohol myths that someone started and has not gone away.

I have to say that I have NEVER seen or heard anyone make a statement like that. It seems to be pretty common knowledge that a lower-end engine will tend to benefit more than a highly-optimized combo by switching to alky.

555 ci motor here in vette. 13.5: compression

Ran gas at best of 1.2460ft and 9.03@152.

Switched nothing except fuel system to magnafuel and alcohol carb, one pro system sent back and apd still using it. The day after swapping to alcohol the car was out of control with wheel stands and still went 9.0s ET/ same MPH.

Switched from Rossler t350 to Rossler glide that Carl said would kill wheel stands.... still way too wild. Put grid in it and still runs low 9.0s and 149.X can dial it to track conditions. And manageable wheel stands.

I would say the alcohol gained definite bottom end on my setup. I'm sure the whole combo matters. My heads are pro1cnc 335cc which is prob on the small side for the combo in this car at 3350 plus me at 200lbs. But runs right where i want to be.... some days i dial it back even more... dead consistent and predictable.

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

I've heard that once you get up into really high compression ratios that gas is better than alcohol. Anyone else ever heard that?

Nope, I don’t believe it’s high compression. Buddy is running 14-1 with 12 lbs of boost, doesn’t have any problem making HP. My theory (not a fact, just an opinion), is on a large CI NA engine, putting 1150 Lbs of fuel per hr. (74.5 gals per hr.) displaces enough air to lower HP. Yes, I realize that methanol has an oxygen molecule in it ( CH3OH). I willing to bet that if you stuck an air turbine on a 632 that the volumetric efficiency fall off quicker on methanol then on gas.

Like I said, just a theory.
Joe

Food for thought. Alky motor has lot of fuel flow,intake and ports are only going to flow so much air and fuel add in carb. As cpl have stated not problem with injection and most injection setup are way big for engine requirements. Problem could lie in induction system allowing enough air to allow burning required fuel to make power.Gas setup other hand needs lot about half the air to burn fuel.
Also cam requirements could be come more critical when trying to get more air to fill bigger cylinder. I know on my Hemi stuff it likes less exhaust duration than a BBC would.My theory is exhaust ports are closer to intake flow wise in Hemi than in BBC and too much duration removes more heat from chamber,just theory with little SWAG thrown in.

quote:

Originally posted by sr4440:
My theory (not a fact, just an opinion), is on a large CI NA engine, putting 1150 Lbs of fuel per hr. (74.5 gals per hr.) displaces enough air to lower HP.

I subscribe to your theory, Sir.

quote:

Originally posted by Lenny5160:

quote:

Originally posted by sr4440:
My theory (not a fact, just an opinion), is on a large CI NA engine, putting 1150 Lbs of fuel per hr. (74.5 gals per hr.) displaces enough air to lower HP.

I subscribe to your theory, Sir.

If this were true blown alky motors would be making even less!

With higher HP/CID numbers, usually over 1.8, alky needs some attention in order t make the kind of power it is capable of making.

quote:

Originally posted by TOP38:
If this were true blown alky motors would be making even less!

With higher HP/CID numbers, usually over 1.8, alky needs some attention in order t make the kind of power it is capable of making.

Attention such as a blower?

quote:

Originally posted by Lenny5160:

quote:

Originally posted by sr4440:
My theory (not a fact, just an opinion), is on a large CI NA engine, putting 1150 Lbs of fuel per hr. (74.5 gals per hr.) displaces enough air to lower HP.

I subscribe to your theory, Sir.

I do too. Blown alky engines are forced induction. They are literally compressing the air into the engine.

Okay something else to think about Indy cars were ran on alcohol, I think they are on E85 now but same question. Those guys are getting outrageous Hp/ Cu. in.

Why don't they get more horsepower from gasoline?

I think it is because they have got the cams, ignition and air flow dialed in for the alcohol.


If it picks up lower end motors so much I think it should pick up high end larger motors. Look at Top Alcohol cars and what is main difference? Ignition, they run huge magnetos to fire them off and they run. Would a Top Alcohol Dragster run faster on Gas?

Why Methanol and big motor lose Hp is a good question and to would like to know the answer. Right now we may have theories but no real firm answer.

injectioin will usually pick a big motor up 8%,the right alky carb will do the same.most carb builders do not have the correct formula and are not willing to spend the time verses production to get the results.mine picked up 50 on the dyno at lubbock when my alky carb went on.back to back pulls

quote:

Originally posted by Curly1:
Okay something else to think about Indy cars were ran on alcohol, I think they are on E85 now but same question. Those guys are getting outrageous Hp/ Cu. in.

Why don't they get more horsepower from gasoline?

Indy cars are turbocharged. Methanol and boost is a match made in heaven because it cools the compressed intake charge down, allowing the engine to cram even more air into the cylinders. Naturally aspirated is a different ballgame.