Hi all,

with a limit of 1.0 bar and sticking with realistic RPM constraints (8500-9000)

whats the maximum hp the YB head will flow when very heavily ported?

cheers

JOSH

 

Well, the best possible solution would be of minimal back pressure, so prehaps a superchager would produce best results if only 1 bar of boost is the constraint.
Martins 500 made 400 bhp at 1.1 bar

 

your getting too far ahead of the game ha ha

thanks for the info on martoons car though... usefull

 

Of course fuel type plays a big part too

 

do you mean octane rating? or running methane?

 

Rod saw 500 @ 1 bar IIRC

I reckon you could do nearer to 600 though at 9Krpm with a turbo specifically designed for this obscure question and a 11:1 compression engine on 300 degree cams and race fuel.

 

lol, yer its quite odd i'll give you that. just thinking as obviously in an ideal world you would run as little boost as possibly for a given output.

500 at 1 bar though wonder where sheady gets his porting done???

 

why? why would you not just run enough boost for the desired power output? 12,15,20 psi, just whatever it takes. Ideally you want as big a power band as posible, and so may have to use a smaller turbo but run more boost (quicker spool, but more of a top end restriction)

 

I disagree that running a turbo at a point in its compressor map where it is LESS efficient is a good thing TBH

2 bar is where its at for GT series turbos IMHO

 

Its not all about max bhp, its about usable bhp. 400bhp with a big turbo at 1 bar is not as good as 400bhp with a decent sized turbo at 2 bar, they both peak at similar revs (as that is down to the engine VE) but the one with the smaller tubo will make more power from lower down and for longer.

 

obviously i didnt explain my view correctly,

my understanding was that most turbos are efficient at low rpm's and decrease as speed and pressure ratio's increase, as below

its peak efficiency island starts at 0.5 bar of boost, granted its less efficient below that as the turbo's low rpm make's it less able to hold a compressed charge efficiently.

as the case is the same in these...

T66


GT35


2 bar on the GT3582 above drops its efficiency by 2% under the efficiency at 1 bar, not a great deal i agree but its still decreasing.

I agree that choosing a larger turbo to reduce boost for a givern power is not always correct, what im suggesting is that the rest of the engine should be made as efficient as possible with porting to the head etc etc, so that the same turbo as before produces the same power just at a lower point in the graph to before..

correct me if im way of the mark?

 

of course, but then why not go for the other obvious solution? which is....

 

????

ive drawn a blank lol

 

Fuck the 2% efficiency shit, Boost = Torque (everything else being equal)

 

lol

peak cylinder pressure = torque

be that from boosting intake pressure or increasing volumetric efficiency