increasing compression, running on regular gas?

[dremd]

Depends *most* heavily on combustion chamber design.
Also depends heavily on the way that the ECU responds to light knock situations (some richen it up and decrease timing to save the motor).

As a point of reference my N/A Supra runs 10.2/1 static compression with slightly advanced timing on 87 octane with 0 issues. Although I figured it would need 92.

[8307c4]

Originally Posted by Southcross

actually.. older cars with low compression engines don't have knock sensors so no, the ECU if it has one, won't do squat to the timing. I know I can retard the timing to help prevent ping, but that kind of counteracts the reason for increasing the compression.

I can actually get some pretty significant increases in compression... the head gasket I'm having made will increase the engine compression over .7 pts (from 8.2 to 8.9:1). I could theoretically go as high as 9.1:1, but I fear excessive mechanical interference if I were to do so.

Well if it doesn't have an ECU and it is carbureted then your car would benefit
from running premium anyhow, why go through all this trouble and expense
when a simple price increase at the pump would yield at least as much?

[Christ]

Originally Posted by 8307c4

Well if it doesn't have an ECU and it is carbureted then your car would benefit
from running premium anyhow, why go through all this trouble and expense
when a simple price increase at the pump would yield at least as much?

How exactly could you make such a broad statement?

[8307c4]

Originally Posted by Christ

How exactly could you make such a broad statement?

Those of us who run premium exclusively know why we do it, the rest will argue
with us to tears so one hates to get this way but if you don't understand
why anyone would run premium then go on and put regular fuel in it already.

Thank you!

[Christ]

Originally Posted by 8307c4

Those of us who run premium exclusively know why we do it, the rest will argue
with us to tears so one hates to get this way but if you don't understand
why anyone would run premium then go on and put regular fuel in it already.

Thank you!

The problem is, you can't possibly have enough experience to prove that every car with no ECU and a carb could benefit in excess of the cost differential by using Premium fuels, which basically nullifies any argument that you could make against the general consensus of scientifically derived, generally accepted facts that Premium fuel isn't necessarily better.

If you choose to believe that it is, that's fine, opinions are not a problem, but mis-applying your opinon as though it is fact brings about a whole new can of worms, especially when you refuse to provide actual evidence to prove what you're saying is indeed fact.

[guudasitgets]

"the car is Mechanical Fuel Injection "

Southcross; your car if it is a stock Rabbit, does not have mechanical fuel injection.

[guudasitgets]

Originally Posted by 8307c4

Those of us who run premium exclusively know why we do it, the rest will argue
with us to tears so one hates to get this way but if you don't understand
why anyone would run premium then go on and put regular fuel in it already.

Thank you!

The ONLY thing a higher octane fuel will allow you to do is run a higher compression at a given density alltitude. Given the same (say 8.2 to 1) compression at the same altitude, using the same intake system and same exhaust and the same timing, you will have a drop in horsepower, not an increase. Your flash points are different

[Deezler]

Originally Posted by guudasitgets

The ONLY thing a higher octane will allow you to do is run a higher compression at a given density.

EXACTLY. Or more boost, in the case of super/turbo-charging. Same principle.

I would be amazed if anyone could drive around and detect the difference in performance from premium fuel in a carburated, low compression, antique engine like the one under debate. Higher octane fuel only enables higher engine performance. It does NOT create it.

That being said, I completely understand running premium in a higher performance or luxury cars. The ECU can detect knock (if present) and dramatically cut the power by pulling the spark timing. My turbo eclipse used to shut me down all the time, major buzz kill. But then again it probably kept me from blasting holes in the pistons, too. (it was heavily budget modded for performance)

[dremd]

Originally Posted by guudasitgets

Southcross; your car if it is a stock Rabbit, does not have mechanical fuel injection.

I don't know about his, but both of the Gasoline Rabbits I have worked on had mechanical fuel injection. ( I *THINK* Bosch K-Jet-Tronic Just like the ones from similar year BMW's).

[JQmile]

If you retard your timing enough you can run almost anything on anything. My drag car runs 91 octane with 12:1 compression, but anything over about 20 deg total timing and it will start pinging.....and of course more timing is better for fuel economy. I'd say you're going to be fine with the thinner h/g. I think 10:1 or more is when you'll start needing devices that will pull back timing.