Bulls**t Or Not

[RPR33]

Hey guys is this for real???

I work with a guy who has a rb30 N/A and has told me it runs 14:1 compression and methanol with around 4-500 hp is this possible

Cheers Russ

[Sydneykid]

Hey guys is this for real???

I work with a guy who has a rb30 N/A and has told me it runs 14:1 compression and methanol with around 4-500 hp is this possible

Cheers Russ

14 to 1 compression ratio and methanol is entirely possible.

The bhp is questionable, particularly if it is still SOHC.

My guess would be 350 bhp, or thereabouts

cheers

[666DAN]

maybe depending on revs?

[Sydneykid]

maybe depending on revs?

The problem is the SOHC head doesn’t flow enough air (without boost) to make anywhere near 500 bhp. So using ever increasing RPM (to get more BHP) is not really an option.

cheers

[RPR33]

this is on stock head maybe ported?

[Sydneykid]

this is on stock head maybe ported?

Nope, that was allowing for MAXIMUM porting. I know what they flow on the flow bench and it is nowhere near 500 bhp worth of airlfow. That's with the biggest (oversized) valves you can fit in the head as well.

cheers

[Fitzpatrick Speed Works]

a rb26 head with some mods will only just be able to flow 500hp in na form

[VB-]

rather than starting another thread, i'll just hi-jack this one

on the topic of porting heads on NA engines, i got to thinking, i was reading the other day about volumetric efficiency and it was basically that a 100% effecient engine could only draw in its own capacity worth of air. e.g. an RB30 could only suck in 3 liters of air. this article also said that most engine these days are very effiecent, like well into the 90% region.

now heres my question, if they are so effiecent, how does porting heads help? if it already fills the cylender to 90 something percent, and you port it, will that increase of a couple of percent in efficiency make a big diference to power output?

[NA_R33]

14 to 1 isnt quite optimal for methanol either. On an NA engine 16 to 1 would be better for running methanol and what SydneyKid said i would guess ~300

[sh@un]

rather than starting another thread, i'll just hi-jack this one

on the topic of porting heads on NA engines, i got to thinking, i was reading the other day about volumetric efficiency and it was basically that a 100% effecient engine could only draw in its own capacity worth of air. e.g. an RB30 could only suck in 3 liters of air. this article also said that most engine these days are very effiecent, like well into the 90% region.

now heres my question, if they are so effiecent, how does porting heads help? if it already fills the cylender to 90 something percent, and you port it, will that increase of a couple of percent in efficiency make a big diference to power output?

Ref italics: Not true- Due to the nature of high-speed airflow (air is actually a gaseous liquid), the chamber of an engine designed/modified for high rev efficency (increased cam duration/overlap, head porting, inlet manifolding etc) will acheive greater than 100% VE as the intake air continues to ram into the cylinder due to inertia, after the the piston has passed BDC.

Even old OHV 2-valve engines can easlily achieve 110-115% VE when suitably modified for racing. I don't have the figures, but I suspect an F1 engine would be a bit higher again.