Thread:

CFM airflow coming out of the turbo

I read an interesting thing on a turbo forum that got me thinking.
This would likely apply to any compressor.

A member posted that the CFM airflow coming out of the turbo is always less that what goes in, and that at one bar (14.5 # boost pressure) there is half the CFM coming out than what went in because it has been compressed.
Makes sense to me,
I've been thinking about this backwards all this time.

To me that throws a new slant on any trying to optimise with large diameter tubing, throttle bodies, porting, big cams, etc.
I've been downsizing on my cam specs for the last three consecutive years and am down to a .630 lift and 255 duration at .050
I haven't noticed any performance decrease or loss of WOT rpm at all and that explains it.

You would be amazed at how much a 3" pipe can feed.........big cams.....no point.

i agree, i don't do cams over 660 lift at all, i just don't see the merit in the extra valvetrain abuse. i'll give alil hp up for reliable service everytime.

Same theory would apply to an intercooler.

The air get more dense as it is cooled..It equals more "pounds of air per foot".

GT

that's something i don't understand about some set-ups i see that are marine built. why go so small on the ic even if its water to air. i ordered big water to air ics with a super low pressure drop. did i add alil turbo lag due to the increase of volume on the cold side? maybe, but i didn't give a shit , i was looking for low iat's up top and over 1/2mile passes get that shit cold so it'll like pump gas too!

Originally Posted by IMPATIENT 1

that's something i don't understand about some set-ups i see that are marine built. why go so small on the ic even if its water to air. !

For me its a matter of space.
It takes a lot of 3" tube to go to and from a large remote mounted intercooler besides the size of the core itself.

With the core size I'm using (11" x 9" x 3 3/4") the IAT is 125 - 130 at 8 sec WOT and by then I'm going faster than I should be anyway. I'm sure the E85 provides some additional cooling past the injectors also.

1/2 mile at WOT !!!

Originally Posted by Unchained

For me its a matter of space.
It takes a lot of 3" tube to go to and from a large remote mounted intercooler besides the size of the core itself.

With the core size I'm using (11" x 9" x 3 3/4") the IAT is 125 - 130 at 8 sec WOT and by then I'm going faster than I should be anyway. I'm sure the E85 provides some additional cooling past the injectors also.

1/2 mile at WOT !!!

we've got some nice spots on the lake that demand it i told ya we will know what the motor and boat can top out at before june rolls around

Originally Posted by turbo wog

and over 1/2mile passes hell yeh!

let r rip tater chip we talked about this last nite and he said "well hell yeah, if the turbos don't stop pulling in 1/4mile, gotta see when they do" got alot of parts in yesterday and the ics came in this mornin, sending them straight over to teh radiator shop to be checked on both sides with 100psi of water pressure

So if we're talking about 1 bar of boost pressure you're saying that the heat generated during compression will have caused the air to expand beyond the volume it was before it was compressed ?

Well then if the intercooler brings the IAT down to ambient, the volume and cfm would then be less than what went into the compressor by the amount is was compressed down to.
So the hot air/volume factor is only going to apply between the compressor and the intercooler.
That would mean that having the throttle body(s) past the intercooler would be more desirable.
Mine are before the intercooler. No wonder it was always such a slug.

Remember several years ago when you had to straighten me out on
intercoolers ? LOL
Lots of water under the bridge since then.
Thanks for that info on the heated air volume.