Board Logo

What compression does your worked N/A engine have
Camo - April 26th, 2012 at 07:33 PM

Hi all,

firstly, I am not after your compression ratio at all.

I am just curious as to what compression your modified N/A engine may have, non turbo engine of course.

Mine has an average of 175psi.

Thanks, Kevin

dangerous - April 27th, 2012 at 06:06 PM

Mine has 200.
You can advance and retard the cam and
note significant changes in the cranking compression.

Naturally a smaller duration cam, or more static compression will increase the number.

I always remember Mick Atholwood (RIP) used to say a good rule of thumb
for a drag engine was to adjust the cam duration and position to aim for 200 psi.

Just for comparison, and peoples interest, my old supercharged 1715cc engine with low 7:1 comp,
and large duration cam only had 100 to 110psi.

Camo - April 27th, 2012 at 09:21 PM

Thanks Dave for your input.

Gives me something to compare to and for others :tu:

Any idea what your compression ratio was with the 200psi?

Cheers, Kev

Craig Torrens - April 27th, 2012 at 10:47 PM

Kev, your compression is fine :tu:

What was the lowest and highest ?

waveman1500 - April 28th, 2012 at 12:51 PM

My old 1500 single-port had 100psi in #1,2 and 4 and 70psi in #3. That thing had definitely been worked, very hard for about 40 years! :lol: Just for comparison. It still ran on all four just fine and I got it up to an indicated 86mph on a straight bit of road. Admittedly, it was slightly downhill! That was in a 1970 Beetle.

Sandy - April 28th, 2012 at 05:43 PM

My 1835 has about 140 psi