Marshall

Hey guys,
I've been looking at the different compressor maps from the T04B to the T-76. It appears they are useless without knowing the airflow through the engine. Is the following a satisfactory was to compute engine air flow?

Say we're flowing 3600 cc/min of fuel (thats 550s and 1200s maxed out) at an AFR of 11.

3600 cc/min = ~57.6 gal/hr =~345 lbs/hr of fuel.

Since the AFR is 11, we get 3800 lbs/hr of air which is 63 lbs/min.

If this is true, it would appear that a lot of the compressors are a bit undersized for 1 bar until you hit the T-66+ territory. Any comments or "dumbass, you can't do that" ?

93 R1

Good question. I'd like to know the answer too

sbertolone

you cant tell what what the injectors are flowing becase at different fuel pressures they will flow more than they are rated. if i port my engine i will get it put on a flow bench to see what its doing. compressor maps also vary in an engine bay because of flow restrictions inside the egine bay, and pressure drop through the intercooler and piping, the can really be used in estimations of a good turbo matchup.

Manolis_D

iTrader: (2)

A good general rule of thumb is ~9HP / lb of air, so 400HP takes about 45lbs/min of airflow
-Manolis

Marshall

Sweet, I'm guessing we're talking flywheel here so for 400 rw it would take about 53 lbs/min ?

Since, maxing 550s and 1200s would support about 440 rw (518 fw), we take 518/9 and get 57.5 -not too far off the 63 I came up with.

This being said, even conservatively, a 60-1 wheel (T04S) looks a little weak for 400 rw. http://www.turboneticsinc.com/comp_maps/fig9.html

Comments?

infinitebass

Would the efficiency of a turbo be a more telling stat about how it performs at a certain pressure?

Blake

Marshall

Yes, but those "rings" on the compressor map are efficiency levels. The 60-1 (T04S) looks to be falling off at the 400-430 rwhp level (2.00 pressure ratio and 50-60 lb/min of flow.)

BDC

They're sort of useless unless you know the amount of airflow a standard 13B can move through it. Figure 10lbs/min of airflow for 100bhp.

You're on the right track as far as learning how to read them and then taking that information and being "practical" with it (practical meaning 'how does this work in the real world when I buy one of these things?')

B