ptuomov

I am not Mike, but the throttle body diameter should be sized based on how much air the engine is going to pump. Holding the valve timing and rpm constant, a larger displacement engine is going to need larger valves, ports, and throttle bodies. My guess is that these throttle bodies in the pictures would be an improvement over the stock manifold in any set up, but only optimal for a 5.0L engine that is spun much above the limits of the stock short block. For most 5.0L engines, you might want to ask Mike if he's making smaller diameter sets as well. Forgive me for interjecting.

tv

Tremendous workmanship as always, a pleasure to see. I would like to know if a nice ALL CF Plenum can be made that would have the MAF at the back and would cover the 8 CF throttle bodies and seal with them at the trumpet lip. If so it could be finished off with stainless steel letters saying 928 4.7 a la AM 177. That would really be the finishing touch. (I know MA had an all CF intake once)

Mike Simard

It's great to have you chime in Tuomo!

The common problem with ITB setups is sizing the throttles without considering intake tract taper and how far away the throttle blade is.

Along with that error go formulas based on flow per given diameter as though the tract is the same size along the length of the runner.
The intake tract should have taper. If you place a throttle blade far away from the head port, the ideal size would be very big. By moving the blade closer to the head it gets smaller, both examples would have the same full throttle characteristcs with an advantage for the close in blade for response.

My ITBs like Sean has, and are on my car, are designed starting from the valve seat area back.
Starting with that given size, I work back with a certain amount of taper while changing from an oval to round cross section, the cross section rate of change stays constant.
I mount the throttle blade as close as possible based on linkage clearance considerations and only then is the blade diameter apparent.
In my case it's 54mm, if it were further out it would be larger.

I feel that the intake tract could be larger still on a 7.0L engine and that it will not be too much on a 5.0L, I guess we're about to find out ;-). They are sized for a port that's been opened up a bit, not stock size.

It's normal for ITB setups to seem too large to those new to the idea. It may help to consider sport bikes and the blade sizes relative to cylinder volume.

Mike Simard

I've been using MAP and TPS instead of a MAF but you could do that and use the new sharktuning from Speake.

Since the throttles are at the head, the airbox doesn't see vacuum and needn't be as strong and sealed.

You could even make a "shaker" hood with a clear lexan cover I suppose.

John Speake

Sharktuner Alpha is perfect for these ITBs... :-)
http://www.jdsporsche.com/sharktuner%20alpha.html

Those are a work of art, Mike !

Anyone know who is the end customer ?

ptuomov

I don't think I am saying here anything that is both true and not obvious. I can do either one but not both! ;-)

Between the bell mouth and intake valves, where's the global minimum cross-sectional area / fastest flow point in your system? Is there one local minimum or multiple? I am guessing that the plate itself has to be at a local minimum because otherwise it will not open, but do you have other local minimums? From what I understand, you have a local minimum "throat" somewhere close to the port and then another local minimum further up where the throttle plate is.

(Or does the cross-sectional area decline all the way up to a unique minimum at the plate? That would make it one big port with 54mm minimum diameter.)

Mike Simard

It's "minimizing" all the way down, I don't understand why you would expect "local minimums".
The point inside the port at which the true minimum cross section resides just before the valves is up to the head porter and is very important. That's one of the details that distinguishes the pros.

The 928 32v head/intake interface is at an angle so it's tricky to measure. In my case the effective cross section there is about 50mm and stock is about 48mm IIRC.

MBMB

For her pleasure.

17prospective buyer

LOL!

911tracker85

excuse my ignorance, but how is the injector fuel levels metered without an AFM on ITBs?

the comment about using Suzuki ITBs for a 16V has me intrigued. no expert on this but always willing to try something.

John Speake

Load and hence the injector open times required are either determined with a throttle pot (Alpha-N) or by a MAP sensor (Speed-Density)

123quattro

Both control systems also require engine speed and intake air temperature. (I know John knows this...)

911tracker85

OK, so where can I research where I would get the throttle pot or MAP sensor 'controller' to trying to fabricate a set of ITB for a 16V from the suzuki ITBs?

I may quickly find this is way beyond my experience level.

Lizard928

Your 84 would require a change over to full standalone like MegaSquirt or VEMS to run ITBs.

Dino V

beautiful!