Acetone and/or water as a fuel additive to methanol.

[patprimmer]

richdubbya

I am particularly interested in your comments if you care to read this, but I also welcome comments from anyone with real data rather than speculation.

I am involved in the tuning of a drag race car.

It has a SBC motor with a Roots blower and mechanical fuel injection, as is very typical in drag racing.

We have 10.5:1 static compression, and we ran about 28 lbs boost with a 6:71 at 30% overdrive on a 355 CI Chev.

By my calculations this gives about 30:1 theoretical static CR.

This ran fine by staying a bit rich to avoid detonation

I think that at much over 20:1 you need extra fuel to avoid detonation, and we run about 15% over stoichiometric fuel.

We just put on a bigger blower and it might give over 40# boost, so we are going richer again.

I also have anecdotal evidence from the guys with the long arms and short legs that seem to be in abundance at drag racing meets, that they rum 11:1 and 45# boost, with comments like "don't worry mate, just make sure it's real fat".

I had anecdotal evidence on acetone as a detonation suppressor, and as a high octane high energy fuel. Acetone also tends to mix well with other fuels.

I have some experience and knowledge of water injection, and anecdotal evidence that water in the methanol improves power. This anecdotal evidence was from Neanderthal types who grunted a lot and back up statements with comments like "no kidding mate, it just makes heaps of grunt".

This is not the type of comment that inspires my confidence, but I knew enough to know that it probably does actually work, at least in reducing knock, and thereby allowing a leaner mixture.

I also think water dissociates and plays a part as a catalyst in the combustion CO to CO2 at elevated temperatures and pressures, as well as extra expansion as the water turns to the gas state at any pressure at temps of over 800 deg C (I think it is 800 deg C).

The last few comments in the doubtful thread on small amounts of acetone vs fuel economy, inspired me to the extent that I might be able to get some "RELIABLE" data at last.

I used to run at 5.5:1 A:F ratio, but with the increased boost, I am aiming at 5:1.

I am wondering if I can run 5.5:1 methanol plus 0.5:1 water by mixing at 10% water in the methanol and jetting the mix at 5:1. Will this give more power and durability than 99.9% pure (as delivered) methanol. What would 10% acetone instead of the water do? What would 10% acetone as well as the water do?

I typically do theoretical calculations of air consumed vs fuel supplied to get a starting point based on A:F ratio, then I start a bit rich then reduce fuel until I get what I think is the optimum signs of heat in the spark plugs. I judge this by discolouration of the threads and the earth strap. At the slightest signs of beads forming on the earth strap, I take out timing or add fuel, depending also on how the threads look.

Remember this is drag racing, so the porcelain does not get time to colour, or by the time it does, it's all over.



Regards

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[richdubbya]

First thing is, I don't have experience with blown motors. I judge a/f ratio by the discoloration of plug threads also. I have run methanol in 2 stroke high output engines (single cylinder 500cc 128 hp) and like I said previously 10% acetone allowed leaning the engine further without damage and made more power. I also have experience with 4 cylinder 4 valve midget engines. Acetone is not allowed by the rules. The 4 valve engines naturally aspirated are 24 to 1 compression. My experience shows that pure methanol makes more power and runs cooler than methanol that has been open to the atmosphere and has collected water. Maybe with 30 or 40 to 1 this isnt true. I do know that race fuel mfgs (such as VP, Sunoco, etc.) recommend and sell methanol that is between 99.6 and 99.95% pure with no water in sealed metal containers. I do know that methanol with excess water will not pass tech. Local track methanol in the US sometimes contains 10% or more water and makes less power in midgets, sprint cars etc. I know I haven't helped much, but I don't speculate or post anything I don't know is absolutely true. Good luck Pat!

 

[patprimmer]

I was looking for more info.

My source of the above info is unreliable, but I have it from quite a few unreliable sources.

I know that in petrol engines, water injection suppresses detonation and allows higher compression and the higher compression yields more power, but not as much as higher octane fuel with no water injection.

I intend to start rich and play safe, but I do wonder if the benefits seen from water injection in a petrol motor can be transfered into a methanol motor, as I do not know any way to increase the octane rating of methanol. Our effective CR is way above what methanol will support without detonation at stoic.

I have never run acetone, but if a reliable source says it suppresses detonation, I would be prepared to try it.

We have never seen a fuel check done at our track.

Why does NHRA ban water added to methanol?

I was not planning to add water in place of methanol, as I know that looses power, but to put in an accurately measured amount then jet accordingly.

In other threads I advocate, keep your methanol dry. I still advocate that because water absorbed affects your jetting. It is hard to know just how much water it absorbed if you don't store it properly, then if you don't get a chance to test it and correct the jets at the track, you end up in trouble. Also water/methanol is more corrosive, and if acquired by accident and not taken into account, then damage will occur. Also, if you are not careful to keep it dry, you end up with various lots with different water content, then you end up using the wrong one.

What I am proposing is an accurately measured brew, accurately calculated jetting corrections, and correct flushing and corrosion control measures after use.

I really don't think it is worth the risk, buy I want the opinion of others whose opinion I trust before discarding it completely.

In principal, I don't like running pig rich just to cool the charge to suppress detonation, so I guess I am making a desperate attempt at a doubtful solution.

I know water can suppress detonation in petrol engines under some circumstances. From what I read here, acetone can in methanol engines under some circumstances.

My real question is, with due care, can I get that detonation suppression to work for me in this engine.

The other problem I know of with water methanol blends is the formation of a goo that blocks jets lines etc. Does anyone know for sure what needs to happen for this goo to form, as it does not always happen as is obvious when methanol is used as antifreeze.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[richdubbya]

The first basic fuel check at the track is for specific gravity. Water adds to specific gravity just as nitromethane does. Without an extensive lab test it is hard to tell what is affecting specific gravity. NHRA has a certain range (SG) that the fuel has to be in. A call to your NHRA tech director should tell you what range they expect the SG of methanol to be in. When I raced in NHRA comp eliminator the car was weighed every run and the fuel (gasoline) was checked about every other run with a hydrometer. A high specific gravity reading automaticaly put you out, no matter what the reason for it was.

See the chart on page 66 of this document:

http://www.nhrasportcompact.com/2003/rules/GenReg.pdf

 

[patprimmer]

I have SG charts for nitro/alcohol, and I think also for water alcohol.

We race in Australia, and NHRA does not apply. If we get places in bigger events ANDRA might pull out the rule book though.

In the meantime, if there is a real advantage, I would like to try it. I guess I will have to experiment at my own risk.

Regards

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[Warpspeed]

If you are serious Pat, an engine dyno and some proper instrumentation is the way to find out. The neanderthals at the drag strip probably know far more about beer as a racing fluid than methanol. The really fast and serious guys that do know, are not likely to tell you.

 

[patprimmer]

Warpspeed.

You nailed it.

Problem is, a good dyno session uses up a serious proportion of the engine life at 1200 HP from a SBC, but I guess it is the only way to really know. I had hoped someone who's work or opinion I trust had already done it.

I don't think the risk is worth the potential for gain, at least not on the budget we run.

Regards

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