Hey everyone.

I just wanted to know what the main advantage of having a higher compression on your engine. I've got an A12 with a higher compresison head on it. The kidney shaped ones.


Cheers
Steve

surely someone wants to answer this?

I've read that one of the advantages are the ability to run higher octane fuels... does this equate to more power?

Is this the only advantage? are there other benefits?

higher compression= more torque
it dose not give you the ability to run higher octain fuel.
it is more the case that if you run high compression you HAVE to run higher octain fuels to prevent detination
you can run high octaine
fuel in most engines low or high compression

higher comp gives you better and lower in the rev range torque.

You only need to use higher octane fuel to prevent pinging on a high comp engine.
This does not mean that you will have to go buy racing fuel or jet fuel.
Normal pump fuel that are a little higher in octane will be fine.

I use the highest octane pump fuel I can find, it burns cleaner.

The fact of the matter is the lowest octane fuel your engine can use is the best for power not the highest.

Because it burns faster.

Just exactly what head does your engine have on it. Round port, or oval.

Generally speaking, Datsun controlled the compression ratio by varying the size of the bowl in the piston, not the size of the combustion chamber, although this chamber volume does vary a little none the less.

If you have a non GX oval port head, then there's a chance that you have lower compression on an A12 engine. If it's a round port head from an A12 engine, then the compression for all hovered around 9 to 1. Geting better than 9.5 to 1 with a stock head & piston combination would be a treat.

I've got a round ported, heart/kidney shaped head.

So, would I be wasting my time running a 98octane fuel? As I'd still be able to make the same amount of power with a 92 or 96 octane?

I think I'll experiment with a 92 and a 98 octane fuel to see if I get a mileage difference.

So with a higher compression I can make more torque but I'll have to run a higher octane fuel to prevent pinging/detonation?

Thanks very much guys.

Try 96.

It will give you more power than 98.

if you were to say use 98 and advance the timing would this give more power than using 96?

I wouldn't say so all that will do is move the powerband up in the rev range it won't change how fast the fuel burns.