g/s to cfm

[Dave Zug]

>>....
> >My question is, what g/s equates to what cfm at what temperature (I 
> >can't find any conversions in my books). the 
> >ultimate question is, what HP level is supported by 255 g/s.
> 
> Depends on the VE of the engine.
> At standard temp/pressure I thinks it's 1.09 grams/ cubic ft air.
> So like a 231 buick turbo uses about 115 ci in per rev.   So at 4000
> rpm uses 462,000 cu in divide that by 1728, 

What is the signifigance of the 1728 .. (144 * 12  ?)  144 for cu-in 
to cu-ft  but whats the 12 ?

> and it's using 267 CFM.  MAF is 
> a 255 which flows 277.  So figurun 120% VE you have max air at 3,200 (er 
> accurately calibrated air/fuel).  
> 
> True is that's at 100%VE, and a Hot Turbo motor can do 140% VE.
> Then a good street NA engine might only do 80%.

I can reverse-calculate my VE by knowing what RPM I get a 255 MAF 
reading at!

for example.. a 231 V6 consuming 277 cfm must be rotating at 
4159 rpm at 100% ve. . If a turbo 3.8 hits 255 MAF (ie 277 CFM) at 
say 4000 rpm, thats about 4% gain in VE.. am I thinking correctly?

I ran this calculation on my SC 5.7 litre from memory and come up 
with 125% ve.  I'll have to look at the data to get exact. neet-o.

I've sent a small calculator type application for calculating VE 
using max-MAF-rpm and CID to bruce... if my calc's 
arent silly to him, I'll post the app.




> While the MAP might not be a flow restriction till 750 CFM your out of 
> calibation area  
> 
> Might just use the default tps/rpm fueling for anything over 4,000 rpm or boost.

I have tweaked that and will experiment with EGT hopefully... still 
car not on road. 2 mo days.

> 
> If ya like the 165 use it for low TPS, and then a 749 for when your making 
> HP, or do the chip flip and swich ecm from MAF to MAP at WOT.
> Justin posted in the archives years ago about using a 256 prom innna 808, 
> maybe do that and run bot set ups.
> Bruce

whooosh   whats that sound  8-)


 
~~~
Dave Z. www.delanet.com/~tgp