Octane question

[Dave Gilles]

.004” squish on a piston port induction 27-31cc engine. Tight.

yeah it wasnt on purpose. A friend put the wrong gasket on an engine I ported.

 

[Mark Anderson]

What signs of detonation are you seeing? Any pics?

 

[Dave Gilles]

looks like sand blasting. just like a nitro engine.

 

[DON MAHER]

Well I

how sure are you? I get detonation starting at .006" squish with 87. It gets severe at .004" I really don't want to destroy this new promodded cylinder.

Hi Dave,

To answer your question, I have not had any sign of detonation using Coleman fuel with the squish as low as.004” !
I normally run.006”-.007”. The downside is the cost of “camp”fuel ,which is about 3 times more than 87 gasoline! The upside is not having to worry about diaframs going bad, and no gas stink!

 

[Dave Gilles]

Well I

Hi Dave,

To answer your question, I have not had any sign of detonation using Coleman fuel with the squish as low as.004” !
I normally run.006”-.007”. The downside is the cost of “camp”fuel ,which is about 3 times more than 87 gasoline! The upside is not having to worry about diaframs going bad, and no gas stink!

that's exactly what I wanted it for. Thanks Don.

 

[LohringMiller]

You can't lower the head volume enough in a Zenoah to get detonation. We ran a lot of tests on various gasolines and there was no power difference in Zenoahs. Also I've never seen signs of detonation in a Zenoah or their clones in years of experience. We ran 101 octane fuel in our Quickdraws with 1/2 the head volume as a Zenoah. They didn't detonate even when the squish was low enough to show piston strike marks.

Lohring Miller

 

[Dave Gilles]

You can't lower the head volume enough in a Zenoah to get detonation. We ran a lot of tests on various gasolines and there was no power difference in Zenoahs. Also I've never seen signs of detonation in a Zenoah or their clones in years of experience. We ran 101 octane fuel in our Quickdraws with 1/2 the head volume as a Zenoah. They didn't detonate even when the squish was low enough to show piston strike marks.

Lohring Miller

I dont have the head or piston for pictures. I can assure you it was clear detonation.

 

[DON MAHER]

I have seen detonation with just a few degrees of timing changes also!

 

[Dave Gilles]

As it turns out I just got this POS in the mail and it's got a bit of peppering around the squish band.


ebayer sold this as a "suicidal promod" lol...no I didn't pay much for it.

 

[DON MAHER]

Dave,
That “peppering” is not detonation but usually the result of a bearing failure!

 

[Dave Gilles]

Dave,
That “peppering” is not detonation but usually the result of a bearing failure!

I dont think it is. bearings are old as dirt in it so they werent replaced. there's no damage anywhere else but the squish band.