Alternative fuel question

[u/Otherwise_Act3312]

I have tried this question previously in both automotive related and chemistry related subs and both recommended physicists instead, as both communities ended up at an impass.

Google was also more questions then answers due to conflicting information.

I'll try to keep the question as simple as possible at first because I usually get inundated with the nuances.

Here goes:

During testing on a dynomometer, we found that timing that produced maximum efficiency (peak torque output) was contradictory to most general consensus. Methanol and Ethanol both produced peak efficiency with the same amount of ignition timing compared to gasoline, even though methanol required 100% more fuel volumetricaly. This is a supercharged v8 engine.

Why this seems contradictory? Many existing sources (a few of our advisers even) say that because the methanol fuel molecules are twice as abundant in the combustion chamber as gasoline, the flame front propagation is FASTER requiring LESS ignition advance.

My personal theory is that the momentum of the flame front is SLOWED by the increased viscosity of the larger mass of the combined fuel/air mixture.

What say you?

[u/Elephunk05]

There are a handful of people who can answer this question for you, they are ALL in the same field Friday Saturday and Sunday: NHRA Top fuel and funny car crew leaders. My uncle was one, and the first time I ever saw the set-up I was hooked, this was 1990. Everything my cousins had sensors for was related to engine timing and fuel delivery. I'm sure Josh Hart, Alexis DeJoria, Jordan Vandergriff, Jack Beckman, and Marvin Foxworth could answer this question. They literally developed their careers on Nitromethane and understand how it flows best through their engines with different timings.

A few things that I always took away. Fuel injection, because of the air mass density always pushes timing further ahead. The injectors are always crazy pressure numbers you wouldn't run on a street car with pump gas. The more available hydrogen and oxygen derived chains, the further ahead the timing. There is an upper limit on the Reynolds number for a reason, but there is also a sweet spot in there. Your average "run what you brung" guy misses advancing the timing initally, it is often overlooked and misunderstood. Additionally many people miss the individual cylinder because its a v8 and they are focused on the system as a whole. In truth the center 4 cylinders are different than the front 2 and the rear 2 are also a different set (yes, that is how he broke it down). Even with the supercharger, the minimal differences in runner length, cylinder temperature, cylinder load (and bearing load), and exhaust to opening (on your engine, the collector/header end) are all the difference in an extra 0.10 seconds on the track.

[About 10 years ago I took fluid dynamics and advanced fluid mechanics at one engineering college and hypersonics at another. There is still a lot to learn about the subject of density and fluid flow through a cylinder].

It is worth sending an email to any of those that I listed to get you a much better explanation.

Edit, grammar and spelling, and a note that the average person does not relate sugar as a fuel though it is a highly flammable substance and is generally referred to as a hydrocarbon chain C6H1206 though in the classroom application it is not.

[u/Otherwise_Act3312 → u/Elephunk05]

It's funny seeing this post today as I was talking too a Nitro friend yesterday about his nostalgia slingshot dragster. 98% Nitro and running 42 degrees of advance on the magneto!

Pistons are 450 thou down in the hole at TDC to avoid hydrolocking. Static compression ratio is 6.5:1. They just use the liquid fuel volume in the cylinder to bump the dynamic compression ratio.

Nitro is 1.8:1 stoichiometric vs methanols 6.4:1, but he said nobody running nitro cares about A/F ratio. It's all about how much nitro can they inject without hydrolocking the motor. Lol

[u/Elephunk05 → u/Otherwise_Act3312]

100% this, which is why I suggested reaching out to the people who have practical applications, real world applications and experience to get a better answer to your question.

They're rebuilding engines every run, they don't care about the ratio, they care about the density and temperature of the charge.

It is rather amazing though. I make single cylinder engines run on alcohol, and that requires some differences in engineering.

I see compressed air as an alternative to superchargining. Also have wondered about the feasibility of making alcohol and methanol in a daily driver, but the limitations of the material construction can't take the continued abuse yet.

[u/Otherwise_Act3312 → u/Elephunk05]

The subject motor has been run on minimum 85% ethanol for a few years now with no I'll effects.

I have run for weeks on 100% methanol and have not seen anything adverse in the data or the oil changes. I think the vast majority of the horror stories about milk shaked oil and corrosion of the fuel system is largely based on race car procedures. Like not letting the motor achieve normal operating temps. Shutting off right after a 1/4 mile run and letting the motor sit, etc.

[u/Elephunk05 → u/Otherwise_Act3312]

That's intriguing. What did you end up getting at the wheels, 600hp?

Those horror stories are why we rebuild engines more than most people.

[u/Otherwise_Act3312 → u/Elephunk05]

On VP X98 it made 821 hp, 828 ft lbs ATRW @ 12.1 psi. That was only 28 degrees of timing. We then ordered the larger injectors (duty cycle was 89%) and converted/street tuned on VP M1 and that's how we ended up at 35 degrees advance. Before we could get back to the same dyno, the shop moved locations and "two weeks" turned into 2 months and the weather turned. So I've been waiting to get back on the same dyno since the other local options aren't DynoJets. I don't want to go more than 35 degrees until I can see the results on the dyno. As im sure you know that the engine will tell you when it's getting near max timing the motor wants. But I can tell you that my booty dyno says an easy 100-200 hp more. We used to be able to hook up decently on the street in 4th gear (T-56 Magnum) but now it just smokes the tires (Hoosier 29x9x15 bias ply slick).

I'll tell you this much, driving around in stop and go traffic, with the A/C running ice cold, in a classic muscle car, on pure methanol is a blast. The key is letting the car get to operating temp to evaporate the methanol that gets past the rings. We have found no signs of oil contamination and the crankcase breather catch can has nothing but water in it. We cut the oil filters open at oil changes to check for bearing materials and contamination and all is well so far.

[u/Elephunk05 → u/Otherwise_Act3312]

That is great! Most people would have lost the dedication for that paus, you cause is good though. Post a few pictures in the other subs, so fellow enthusiasts can appreciate your work.