Comp ratio vs cam duration

[Caveman]

Re: Comp ratio vs cam duration

Cavelady - to you have any engine dyno software?

I wonder how good they'd be at showing the resultant changes of these theories you're posing....

interesting stuff fo sho....

Thanks for all the input fellas!

Hey Milgirl! Thanks for the tank, honey! I hope the beer found your liver in good spirits! Ha!

Yeah, I've got DynoSim... I love messin' around with it. If it weren't for food & water (& work! Yuk!) I'd spend days straight pluggin in different cams.

Problem is, I spend most of my life at F'ing WORK these days. It's debilitating for the rest of my life... (read 'cars & girlfriend')

As far as the 'statements with a question mark'... I'm just trying to state things in a manner that I think I understand them, in a coherent way so that others can clearly tell me I'm full of crap/wrong/or have rectal/cranial inversion.

For the 9:1 motor reference before... I just pulled 9:1 out of my a$$ for an example. I agree, a low-compression motor would probably behave just like you say.... but how would that example (a motor with 180+ cranking psi) work with a motor of say... 10:1 or 11:1?

[joe_rocket45]

Re: Comp ratio vs cam duration

now you're getting to close b/c there are so many variables... I have seen a motor with cast iron heads making 210 psi run on 93 octane (my buddy, and for what it was it'd make ur butt pucker) .. me, I play it safe and go for RPM keeping around 150-160 cranking psi..... esp when nitrous is being used in large quantities..

if you know the head flow and CI you can calculate RPM.

http://users.erols.com/srweiss/tablehdp.htm

If you know the RPM you can now calculate the pressure to reach XXX Hp...

http://www.google.com/search?q=HORSEPOWER+FROM+BMEP <search
https://www.epi-eng.com/piston.../bm..._yardstick.htm << read

www.speedwaybids.com/calcs/bmephorsepower.html << calculate


now here's where it get's tricky b/c there are so many variables.... how much pressure can you take ;D

http://www.wallaceracing.com/dynamic-cr.php

(wallace calc seem to be off sometimes..fyi)

[JeffMcKC]

Re: Comp ratio vs cam duration

And let me pose some more confusing questions;

If you build a 'low compression motor', with a cam that gives it an early Intake Valve Close, and therefore high cranking pressure (180+ psi)......

Are you then going to run into detonation problems.... even though it is a motor with only say, 9:1-ish compression?

(ALL things being equal: an example of identical motors, good aluminum heads, identical cooling systems, in identical vehicles of the same weight, etc..)

And would a 'high-compression motor' with LOW cranking pressure (by comparison to the other example) then have LESS tendency to detonate?

Kinda throws a curve at what we think of as a 'street motor', huh?

No not at all, by the way, they close that intake early and make it detonate, so it will fool the dyno into thinking its making more power than it is , by measuring the Detonation not the power its making.