Dunc

What is the minimum CR that a gasoline engine has to have? Isn't it like 7:1 or 7.5:1? I did search too haha.

voiceinurhead05

I'm not sure of the CR, but for a honda engine the absolute minimum is anywhere from 45-65psi (depending on the engine)

Padawan

Gasoline internal-combustion engines have existed with compression ratios of 2:1.

voiceinurhead05

Maybe, but it wasn't a Honda.

Padawan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by voiceinurhead05 &raquo;</TD></TR><TR><TD CLASS="quote">Maybe, but it wasn't a Honda.</TD></TR></TABLE>

No, it wasn't, but the original poster stated "gasoline engine", not "Honda engine".

Dunc

Now, that I did not know...let me rephrase then:

My main concern is how low of a CR before a honda/acura engine does not turn? Also, is that 2:1 engine still being used today or could any engine today use something that low?

TunerN00b

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dunc &raquo;</TD></TR><TR><TD CLASS="quote">Now, that I did not know...let me rephrase then:

My main concern is how low of a CR before a honda/acura engine does not turn? Also, is that 2:1 engine still being used today or could any engine today use something that low?</TD></TR></TABLE>

My Triumph came from the factory with 7:1 compression, and it ran fine. I don't see why a Honda engine wouldn't run at that low, or a lower ratio, but you'll certainly be making less tham optimal power that way, and might not be able to make use of the entire power band. Cam profiles and rpm range are chosen with an engine's compression ratio in mind.

But seriously, there's no reason to use less than 9:1 these days. Why was this question asked?

Dunc

Mainly because I was trying to prove and have some people realize that anything under 9:1 is overkill and not that useful......ESPECIALLY for only 400whp. 400whp is childs play now days.