OK ...

At 5300 ft above SL (aprx 12.0 PSIA give or take)

With an FP Red

(max engine rpm at 8K)

(FP says the Red can flow 60 lbs per minute, Buschur mentions 56 lbs per min(?))

But, in any event:

I'm considering getting my stock Intake Mani ported and the 65mm TB.

How close to "running out of air for the turbo" am I currently ?

Will I likely be playing a game of diminishing returns by porting the IM and getting the 65mm TB?

I'm planning on running 30 to 32 psi at the track, and likely closer to 28 or 29 on the street.

I can't figure out what formula to use to calculate things, especially because I don't know how many pounds per minute I'm actually flowing right now.

I know at lower altitudes, it's not an issue, but up here with the thin air, there are more factors to consider. The turbo works harder up here to produce the same psi at Sea Level, etc...

I'm logging out for the day, so I'll check back for replies tomorrow.

Thanks for any help or ideas

 

Well lets see, at 12 psia, to run 32 psi you're looking at a 3.67 pressure ratio, about .5 a point higher than what you would be seeing at sea level, so you need to make sure you're not getting out of the reds efficiency range.

To find how many lbs of air you're flowing you use the good 'ol Ideal Gas Law. PV=nRT
so
n=PV/RT

n= the mass of the gas

To get n in Lbs/min the equation goes like

P(psia)*V(cu ft/min)*29/10.73*T(deg R)

So, I'm seeing that you would be flowing about 57.9 lbs/min at your altitude, and 61.5 at sea level. This is assuming that an FP Red is efficiently making 32 psi at 8000 rpm and 5000 ft. Which is obviously not gonna be the case.

 

Yeeaaaah baby, that's the stuff I'm looking for

(and I do understand what you're saying, thanks to my EFI101 class a few years back)

BUT:

"Will I likely be playing a game of diminishing returns by porting the stock IM and adding the 65mm (MilSpec) TB?"

... Since the flow potential would be increased by the larger TB opening and ported runners ... or can that even be practically or theoretically assessed?

OR ... Am I just off track in the logic of my question/reasoning ?

Thanks again for your response!

 

You're always playing a game of deminishing returns. At 30lbs you're not gonna hurt anything by opening up the intake, and while you may not see the same gains you would at sea level, it will still help. Unfortunatly I don't have any math for that. Someone does I'm sure. If it were me I'd just put the biggest turbo I can afford on there and keep turning the knob.

If you want I've been working on a spread sheet for compound turbos, but you can plug your values in and find some useful info. Give me your email if you wanna take a look at it.

 

Here's a handy little tool that might help you out a little. It has a steep learning curve, but play with it and you'll figure it out.

http://www.not2fast.com/turbo/glossa..._calc.shtml#sz

 

Thanks, Very nice and very "Heady"

If I'm not careful, I'm liable to learn something through all of this