flip1199

Ok i was looking through my old "Super Street" from aug. 2000, and trying to read how to select the right turbo, but it just did not make any sense. Can someone make sense of this for me.

1. Calculate the airflow for the engine in naturally aspirated form. Use this formula for standard atmospheric pressure: (CID x RPM x 0.5 x EV)/1728. Note: 0.5 is used for four-stroke engines. EV= volumetric efficiency (0.80-0.90), Airflow rated will be in CFM

2. Knowing the desired boost level, calculate airflow rate under boost by multiplying the pressure ratio by airflow rate (na-cfm). Use (14.7) +boost)/14.7 to calculate pressure ratio.

3. To convert CFM to lbs/min, use (CFM x 0.076 = lbs/min).

4. Use compressor maps to find the best suited to the airflow rate and pressure ratios you have attained.

You can roughly calculate estimated horsepower by using th following formuls:

Lower value: 0.052 x CID x (psi boost + 14.7)= bhp
Higher value: 0.077 x CID x (psi boost + 14.7)= bhp

Can some one make sense of all that for me

The_Head

Download this program from this thread, it will help you determine the best compressor for your needs.

https://honda-tech.com/zerothread?id=233598

flip1199

ok now i downloaded it. So what the hell do the numbers mean.
These are the numbers i got

pressure ratio: 1.7142857
air flow: 491.6414 lbs/min

The_Head

Uh, it sounds like you messed up with the inputs for the calculator.

What you do is you plug in your numbers at various RPM's with a fixed amount of boost to obtain airflow numbers. Then plot them on a compressor map you think would be good for your setup. If most of your points fall within the high efficiency part of the compressor map, it will probably do the job.

Here's an example.



This calculator only helps you to choose the compressor side of your turbo. The exhaust side... I dunno. Other people can chime in on that.

MikeMAN

saweet! anyone remember the link on how to read compressor maps?

fire7882

https://honda-tech.com/zerothread?id=96443