Calcs Involved: EFI Throttle Bore Sizing?

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How did Ford (or any other manufacturer, for that matter) arrive at the various throttle bore diameters used in a long-runner port-injection motor?
(for example, the late, great 4.9L)

I would imagine that RPM, torque range, bore and stroke, intake runner length, valve sizing, cam timing, CFM flow potential, etc. etc. are all related together together in a series of formulii, but...what are those calcs?

Sorta related: Why dual throttle bores, rather than single?

Eddie
 
Extensive airflow testing?


I know an engine can only flow so much CFM....theres only a certain limit for a particular engine....so thats a big factor...the throttle body should meet that maximum possible CFM of air that and engine can pump.

Then they test it for assurance that it meets the airflow demnds of the engine...

An educated guess...
 
Eddie,
Check the websites for peddlers of TBs and MAFs, there is a formula similar to calculating carb size with a conversion factor , "CFM to TB size in MM" same for MAFs.

Didn't you cut a 300 efi plenum open? Dual butterfly because plenum is actually divided in to two small plenums. More torque over a wider band. Don't know about truck V-8s, maybe retained 300 dual butterfly for commonality.or makes a lower intake package.
 
...but you're suggesting I do my own HOMEWORK! :shock:

I need to go back through the archives as well, I'm certain SR fielded that a time or two when we were batting around upgrading from the 4.9L's 42mm v. 302's 44mm.

Eddie
 
Got the formula some where used it to calculate for my home brew EFI 'm workimng on.
TB, using late mod Mustang 4.6 Cobra, 2 x 54mm. eBay $35. Has the same TPS as 300, must be generic.

OK, After your homework eat your veggies or 'll tell your mom.
 
:roll:

Actually, I'm more interested in sizing the plenum supply aperture for a homebrew long-ram/turbocharged application, mechanically injected.

My thinking is size the runners small enough to provide a ram effect off-idle and at low rpm while the turbo spools up.

I want to size the plenum enough to keep gas velocity up while imposing minimum restriction to airflow, but conversely not so large a volume that turbo lag is increased.

I never have found aluminum tubing bends at any kind of price I can afford, so it looks as though the manifold will be built out of steel exhaust header components, then ceramic-coated inside and out.

Eddie
 
Eddie,
The 302 uses a 50mm T/B, the 300 a 43 or 44, I forget which. The ratios of their areas is approx. 1.3 which is the approx. ratio fo their HP and torque peaks. There's some kind of an optimum velocity thing happening there, don'tcha think?

As to the whole business of forced induction, I think all that Prof. Smith/Sir Harry tuning stuff just goes away. You're shoving air into it, you don't need any negative pressure wave phenomenon to get it to breathe better. The whole idea of using the kinetic energy of the incoming mixture to improve VE is replaced by boost pressure. All you need to do is minimize restrictions and flow losses and crank up the boost. Short, smooth large diameter passages are all you need.

Brute force overcomes subtle engineering excellence every time.
 
Peeking voyeuristically at the engine bays of current M-B and other German/Austrian high-end rides, my attention was drawn (and for once, not by a 2x4 either, thank you very much :oops: ) to a combination of 8-12" runners, same manifold, blown AND N/A.

OK, same manifold, i.e., volume production, costs kept down, or--could it be?--low end compensation via wave propagation for boost lag? Or for promoting air flow organization?

It's probably a combination of all three suppositions to varying degrees.

Eddie
 
Pull out your Prof. Smith and do the math (My copy's 250 miles away at the moment or I'd do it myself.) 8" is a very short runner and 12" isn't exactly long. Those engines are already tuned for mega revs and as a result minimal flow losses. It's not so much production efficiency as having a system that's inherently turbo-friendly. On a 300 with it's very long manifold runs, flow losses would be an issue.

A few years ago Cliffy had the "soon to be released" EFI system on their catalogue cover. They took their 4V manifold, built up pads and machined them for injectors and added a T/B where the carb would normally go. you could do the same thing for the injectors, connect the J-pipe from the compressor outlet to the T/B and only have to worry about where to stick the air meter. Minimal fab work required on the intake side.

Plus you could usean Offy manifold just to piss Cliffy off. :lol:
 
I thot ol' Jack was a dead guy. Dead guys don't have emotions (unless they're on Buffy the Vampire Slayer :D )(crank up the sound system, turn down the meaningless dialog, crack a cold one, watch and learn :lol: )


I have Ol' Doc Smith with me on all occasions, especially business or other trips. WHAT'S YOUR EXCUSE :?

Eddie
 
I'm on TYD in Cincy, Dr. Smith is at home. I was counting on the Gideons to leave me a copy in my hotel room.

Buffy's Ok, but I want Faith to hurt me real good.
 
I found the Gideons hotel book worked just fine, and faith didn't hurt me at all. But I'm only human, and Faith looks like shes been well appionted from the factory. :lol:

Hey, the really intresting point is the actual flow rate isn't related to the area as much as the shape.OHV Cologne V6 Explores had a huge throttle body, but it flowed like a plumbers gate valve. Other smaller throttle bodies (pre 96, I think), flowed much better, even though they were smaller. An 85-88 EFI X-flow Falcon 250 (Aussie) was about 65 mm, and flowed well.

Intake runners are simliar issues. Depending on what you want , the long intake runners could be a negative too. I'd shortern them if at all possible.

A turbo makes up for restrictions, and the ultimate set up for something with the torque of a 300 I6 is likely to be more like the Hillborne injection runner with a big air box and one nice large throttle body hanging off the centre. Stubs stacks in a a long letter box. Thats how I'd do it.
 
...are more comparable that than it first appears: Both books require multiple short-duration reading sessions, immense thot between readings, date to antiquity, are rawther pleonastic, have been rewritten (with-and without agenda) a time or two, AND PUT ME TO SLEEP :wink:



The shorter runners make A LOT of sense--straightening out (organize) the airflow is probably the big benefit.



Oh--check out "Enterprise" :shock: I've become a Vulcan fan of late :D

Eddie
 
...that was "7 of 10" :shock: The other numbers are probably correct. 8)

This is amazing...ask a simple question about hole sizing, and wind up in a discussion reaturing reanimated dead guys, worthwhile (though kinda wordy) reading stuff, and TV sci-fi goddesses :P .

Eddie
 
StrangeRanger":10ow47sq said:
Do all the women in Oz look that good?
Click to expand...
Best authority on the comparo is my mate Dave in DC. He says Aussie women scrub up pretty well in the global stakes. Slightly behind Denmark, way ahead of the US and aggregates take them ahead of the UK.

Dave's hardly scratching; it's not like he's chasing a cheap piece of tail. I'll have to take some "streetscape" pics in Sydney and email them. :shock:

Adam.
 
Yup, a lot of them do!. There are Greek Goddesses everywhere! That's why I stay in New Zealand. I wanna stay married to my wife of 13 years!

Um, hang on dudes, shes not 13 shes 31, oh darn it StrangeRanger you got me all crossed up... it was that 38 D comment! :oops:

Jack is on to it. Maybee you Turbo guys like Eddie should adapt an EFI X-flow intake manifold.
 
The throttle bodies on the ford trucks are dual in order to increase intake velocity. two small holes create more velocity than one big one. Intake & exhaust velocity = torque. Plus the dual plane intake style also means more tire eating torque. :twisted:
 
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