matt_ledbetter

I have done a little searching, but haven't had much luck. Does anyone know of a site that lists the flow rates (in cfm) of the various turbo upgrades?

-Matt
'93 Touring

Greg

I would also like to know the flow of a t04e with a .70 compressor side

crispeed

Most turbos are rated by Pr(pressure ratio) vs. lbs/min.

lbs/min divided by 0.069= CFM
eg. T-66 flows 72lbs/min. 72 divided by 0.069 = 1043.47 CFM

14.7 + boost pressure(psi), divided by 14.7 = Pr
eg. 15psi + 14.7 divided by 14.7 = 2.02 Pr

crispeed
87TII
9.20@150mph

Jedon

Thank you crispeed.
So if you calculate the flow and the Pr, you can use that to determine the power range of the turbo? I guess you would need to look at the actual map for that?

matt_ledbetter

Thanks Crispeed...

-Matt

RICE RACING

Once you know what flow rating the compressor will provide, then you can calculate out how much power you will make.

To do this is hard, you need to know the af ratio, the BSFC, the ambient temp, the compressor eff (point on map), the pressure ratio (of map "boost") along with this you need the BSFC curve in relation to the power it makes, for example certain engines will make the same BMEP with a wide af ratio and others will drop of either side of the ideal of ratio.

The BSFC is affected by many things such as, compression (static and dynamic) The influence of engine porting for example.

To answer Greg, the turbo on a 9.0:1 comp "street ported 13B" will flow 775CFM (near the end of it's map) wich equates from my testing to around 590 to 600BHP (engine power)......this would go slightly higher with n/a rotors due to the better BSFC achievable and would result in a power of around 630+ bhp for this particular turbo for the same "air flow rate"

HWO

now, if you had all read this thread thuroughly

https://www.rx7club.com/forum/showth...threadid=39014

you would know that CFM has nothing to do with HP, any turbo weather it be the size of a bucket, or the size of a pea will make X HP if both blowing Z psi...................... NOT, but the guys in this thread sure as hell think it does

waynespeed

So we can figure out CFM on the compressor side. How does one calculate CFM or flow rating of a given a/r or trim. Futhermore, at what point does the trim becomes more restrictive than the a/r and vice versa?

RICE RACING

This is what I do.

To find out ehat CFM or flow rate compressor I need, I first calculate out the CFM the engine will breath (this is VERY IMPORTANT)

To calc this out you need to know the following.

Engine capacity
Engine revs (max power)
Ambient temp
Boost Pressure ( for max HP)
Intercooler Eff
Volumetric Eff (of engine ***at max power)
Barometric Pressure
Compressor Eff

NOW all of this will give you the FLOW rate of the engine, i.e. What is needed from the COMPRESSOR MAP!

Now to know the affect of exhaust manifold length/rear housing a/r, turbine trim, Wastegate size, Exhaust restriction ALL have an effect on the Volumetric Eff & the RPM at which max power is made and hence either reduce the flow rate for a given boost or increase it. How do you know what effect it has, well you realy need to test it or ask experts with specific knowledge of that system applied to the EXACT type (porting etc) you are running, It is complex indeed.

Once you know all of this stuff then by simply knowing this

BSFC (at max power)
Air Fuel ratio

You can calculate the EXACT BHP via a formula to a extreme high degree of accuracy, every time.

This is the formula I made and I use for this purpose.

HP=1000/af ratio/(BSFC/3600)*Barometric/1.01325*1.204/sqrt((273+air temp)/294.1)*(capacity/1000*volumetric eff*(rpm/60/2)*(air temp+273)/(air temp+((((boost/14.5)+barometric)/barometric)^.238-1)*(air temp+273)/compressor eff*(1-intercooler eff)+273)*(((boost/14.5)+barometric)/barometric))

waynespeed

"well you realy need to test it or ask experts with specific knowledge of that system applied to the EXACT type (porting etc) you are running, It is complex indeed. "---Tell me about it, lucky for us we have guys like you, with vast experience with these motors, who can shed some light on the Rotary Internal Combustion Engine.

The turbine side of a turbo acts like a restrictor plate. I wish there was some formula to determine the trim and a/r configuration for a given HP output that would keep you in the power band and not just going with a oversized a/r that will make you look good because of peak HP, but a whole lot of lag.. Till then experience will be the best teacher, keep them coming.....