Intake Flow numbers

[Walt Fricke]

I am building a short stroke 2.8. I have flowed the heads and punched those numbers into the Dyno2000 engine program. The program also asks for what the intake system (be it carbs or ITBs) flows at 1.5 or 3mm of mercury pressure drop.

Holley 4 barrels are advertised with some such figure. What I would like to know is what it might be for 46mm TWM ITBs. Even better, for such ITBs attached to a tall PMO manifold which necks down to 40mm at the port. For completeness, one would like to know the effect of a clean, oiled, ITG.

Anyone have a likely figure for any of this?

I love the program - I can plug in very optimistic numbers for this and that and show buckets of horsepower and dream of blowing away the competition. But I'd rather my first run on a dyno was compared with a more realistic assessment.

[356RS]

No answers Walt but I'm also interested. subscribed.

[Tippy]

One of those great Porsche mysteries that drive me nuts too. You take anything American, and you have any piece you data you need within a week of release! Ok, I am exagerrating, but you get my point.

[304065]

Originally Posted by Walt Fricke

I am building a short stroke 2.8. I have flowed the heads and punched those numbers into the Dyno2000 engine program. The program also asks for what the intake system (be it carbs or ITBs) flows at 1.5 or 3mm of mercury pressure drop.

Holley 4 barrels are advertised with some such figure. What I would like to know is what it might be for 46mm TWM ITBs. Even better, for such ITBs attached to a tall PMO manifold which necks down to 40mm at the port. For completeness, one would like to know the effect of a clean, oiled, ITG.

Anyone have a likely figure for any of this?

I love the program - I can plug in very optimistic numbers for this and that and show buckets of horsepower and dream of blowing away the competition. But I'd rather my first run on a dyno was compared with a more realistic assessment.

Can TWM not supply these data?

[Walt Fricke]

TWM was purchased by Borla. My e-mails using their tech and their sales contact e-mails were bounced back by the server.

I'm off to the track, maybe Monday I'll try a phone number.

[LJ851]

Something to consider between carbs and ITBs is that dry flow #'s are not an equal comparison. An ITB typically introduces fuel below the butterfly (the primary restriction) while a carb introduces fuel above the venturi and throttle plate and that fuel takes up valuable airspace in those restricted areas.

[PFM]

Walt,

I understand what you are looking for to plug into you engine program but not sure how to get there. I can tell you a bone stock 46mm ITB with a nice stack on it can flow 360 ish CFM at 25" of H2O. I also know if you put that on your cylinder heads you will lose little if any flow as I do not think the heads will flow 360 CFM at 25" H2O. A 40 mm venturi can move over 380 CFM at 25" H2O.

Hope this helps,

PFM

[HawgRyder]

When we were working with Coventry Climax engines...the definitive number was port flow velocity.
The factory was working about 300 FPM (feet per minute) at the time and those little beauties put out about 450 HP from 2.7 litres.
Best I can offer .
Bob