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Re: GoodParts Compression ratio

To: mkutka@mcw.edu
Subject: Re: GoodParts Compression ratio
From: "Robert M. Lang" <lang@isis.mit.edu>
Date: Tue, 9 Aug 2005 14:30:36 -0400 (EDT)
On Tue, 9 Aug 2005 mkutka@mcw.edu wrote:

> I have one question, do you think that you can run on pump gas (91+) with
> 10.8:1? Seems on the higher side from what I have heard from true
> "drivers."

Assuming that by 91+ you mean 91+ RON + MON / 2 (what pumps are supposed
to display in the US), then I would have to say that you need 93 octane
fuel and you'd have to retard the ignition. 94 octane Sunoco (or other
brand) might work...

I would not run an iron motor over 10:1 without knowing the exact fuel
octane and whether the motor will knock under load.

Call me cheap, but I don't like holes in the pistons and broken rings...
and that's what happens if your motor experiences detonation.

A lot of folks with high compression motors run av-gas or racing fuel to
insure that there is no detonation.

>From asking around other TR6 owners with "pumped up motors", I'd have to
say that going much above 9.5:1 is iffy if you drive because it's not
unusual to pull up to a gas pump in Backwater, USA only to discover that
your only choice is regular 87 fuel. Been there, done that. With 9.5:1,
you have a prayer (that the merchant has some octane booster on the
shelf). With a higher C/R, you're asking for trouble.

On my 9.5:1 car, I've tried a tank of 89 octane pump fuel and experienced
"run-on" when the motor is hot. When I use the 93 octane pump fuel, I
don't get any run-on. I wouldn't think of putting 87 octane in there.

> Michael K CD255L, etc....

regards,
rml
CF14111U and CR1871UO
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