Adverse effects by using the wrong fuel?

[KrazyKraut]

I know German planes were marked with B4 or C3 triangles so crews wouldn't use the false octane fuel on the specific planes. But then I also read of US trials of Japanese fighters using US fuel (which greatly enhanced performance).

So what are the effects of using fuel of higher or lower octane for engines not designed for that number?

 

[kool kitty89]

As long as the engines are strong enough to handel the increased power obtained at higher boost settings (which high octane fuels allow) they should work fine once tuned to run on those fuels. (of course, boost settings would need to be increased to have a significant impact on performance)

The Merlin III is a good example of this, while not designed to run on 100 octane fuel, it was found to be capable of this, allowing emergency boost to be increased to +12 psi (from +6.25 psi). Increasing power from 1,030 hp (6.25) to 1,160 hp (+9 psi) to ~1,300 hp (at +12 psi)

 

[mad_max]

If the engine (for example the BMW 801 which required C3) was run at a normal power level for C3 and B4 was in the tanks by chance; there would be detonation involved.

SuperchargersOnline.com :: Detonation, Knock, and Pre-Ignition 101

A number of things could happen. In very little time, the top of the pistons would burn through most likely.

Now if it was detuned to be able to run on B4 which would reduced power , then there would be no problems. Expect the power would be reduced significantly though.

Running a higher rated fuel than an engine can use or set up to use would be no problem. It wouldn't make more power just from the fuel though. The engine could produce more power, but would have to be set-up to properly to make it. Higher boost pressures, advance in the timing, proper fuel mixture and a change to cooler plugs probably. Of course the said engine must be strong enough to handle the higher power.

As for the Japanese aircraft and producing more power on US 100/150...well it's possible if this fuel was of higher octane than the Japanese variety. If someone could find the fuel tests of the Japanese fuel(s), then we may take a stab at the answer.

 

[Soren]

Another factor consider here is wether the engine is configured for natural or synthetic fuel, cause there's a difference. German engines didn't run very well on Allied fuel and lost power, as evident in the Allied testing of German a/c.

Note: German C3 fuel equates to Allied 150 grade fuel, despite the 96 octane number.

 

[kool kitty89]

What about the C2 fuel?

 

[mad_max]

Soren,

At times yes C3 was almost the same rating as 100/150, at other times was equal to 100/130. And those engines run just fine on non-synthetic fuels. It's a myth that they won't.

I've talked to an engine rebuilder that has overhauled quite a few DB's and he sets them up to factory specs. He runs them at 100% power on 100LL wit no problems at all. Of course with 100LL they won't run them at WEP settings just as the Merlin's he rebuilds.

My questions:

Hi Mike,

I've always been intrigued with the synthetic B4 and C3 fuels the Germans
produced from Coal.

Since you've posted your website and you have rebuilt DB 601/605's and
now in the process of rebuilding a BMW 801; I'm curious as to the fuel
you are using to run the engines in.

I have chemical breakdowns of them and the percentages of the
hydrocarbons and additives are much different than fuels derived from light
crudes.

The question/s I have are. Do you have a fuel specially blended to
match the Synthetic B4/C3 formulation? If not how demanding is setting up
the the injection pumps to run on crude based fuels and is there a difference
in the boost pressure maximum that can be used?

Thanks so much for your time and answer.

His answer when I asked the question on fuels and how they run them without having a synthetic fuel with the qualities of German fuels of WW2. Mike Nixon of Vintage V-12's sent me this answer to my question.

The simple answer to your question is that I am using pump 100LL aviation fuel. I have tested the fuel with a 10% lean condition but flight settings are the original flows. we can run higher boost, but the cost of the testing and the value of the engines make that a non-issue. Why the fuels used by the Germans were of a lower octane, the high power settings usually included Nitrous, water/alchol or some other additive injection for the combat power setting.
We have used much higher power setting with race engines with good sucess and the quality of the internals of the engines are very close.
The construction of the fuel is different but the burn rates are same to a point. I have used 100LL pump av gas at original and as lean as 10%. I set the injectors at the book setting and the engines run normal. The internals of the engines are very good and the potential powers would be higher with 115/145 fuel.

mike nixon
I guess there is a lot of information you guys don't have. when I have time I will start posting some of my data. Mike Nixon of Vintage V-12's check out our web page at vintagev12s.com

From someone who knows from practical experience with no bullshit involved.