ptuomov

I'm not getting your point.

Strosek Ultra

That is completely wrong. I looked into making my own ITBs but found out it was too much work so I ordered a set from ATPower in the UK. I have a throttle blade for a Dellorto DHLA48 carb in front of me. Measuring the blade along the shaft it is 48mm, measuring blade 90 degrees to the shaft it is 49mm. You need a CNC machine to be able to manufacture such an elliptical blade.
Åke

Strosek Ultra

Actually it looks to be a good idea but with the much larger physical size of the 928 engine block, the much larger bore spacing of 122mm, I find it easier to make the intake manifold from scratch.

From attached pictures of a BMW engine, I used the same kind of idea, cut of a part of the stock intake and welded runners for the carbs to it.

If you are running hot cams with much overlap and one only throttle valve, you probably will be faced with the problem of engine jerking, pulling unevenly at lower rpms from the exhaust pressure pulses passing through the intake. The solution is ITBs where you have a throttle valve at each intake port.

Åke

V2Rocket

...or a stamping machine with a good die

Ducman82

"IF" you can get the aston intake to fit, for the sake of argument lets say you can. The first thing to pops in to my head is incorrect runner length for our engines.

GregBBRD

Completely wrong, but worked perfectly....and accomplished exactly what I was trying to figure out....if there was a flow restriction at the butterfly.

That was the goal....not nit picking details.

Note that because there is a throttle stop, the blades never touch bore....so round or eliptical is a moot point. I've still got a couple of these "completely incorrect" throttle bodies running around, today.

I think you people forget that somehow, throttles were made for decades, without a CNC machine....

Can we move on to what matters, now? The larger butterfly made no change in the stock manifold.

ptuomov

Old school throttle body butterfly valve plates were cut to a geometrical ellipse shape on a lathe. They were/are mounted at an angle and cut at a constant distance relative to the lathe centerline. The minor dimension of the resulting ellipse is matched to the round throttle body element bore which is round.

GregBBRD

Completely wrong, but worked perfectly....and accomplished exactly what I was trying to figure out....if there was a flow restriction at the butterfly.

That was the goal....not nit picking details.

Note that because there is a throttle stop, the blades never touch bore....so round or eliptical is a moot point. I've still got a couple of these "completely incorrect" throttle bodies running around, today....never jambing, working perfectly.

I think you people forget that somehow, throttles were made for decades, without a CNC machine. They were round, made on a lathe, for many, many years. They kissed the edges at the pivot point with a simple file...exactly like I did...so that the didn't bind.

Can we move on to what matters in this discussion?

The larger butterfly made no change in the stock manifold....that was the answer to the question that was raised.

mark kibort

and thanks for that answer. as i heard rumored before, it made no diff.. BUT, i had no idea of how much larger you made it. i think that is proof that you are going the right direction , tackling the intake itself.

yes, i know thats a HUGE "if", i dont think the runner length will be an issue, in fact, that intake is doing amazing things with the aston and the mustang intake is prettty similar. "IF" it could work, i think the hp gains would be huge. 5 or 6.4 liter a like.

ptuomov

I would favor cutting the throttle plate to be elliptical, because if a round plate is throttle stopped to an angle, all sorts of weird things can happen. For one, the throttle doesn't actually close, which is a simple matter of geometry, and idle will be weird. The angle of the plate side is wrong relative to the bore. The vacuum ports will also likely not work correctly in the s4 throttle body element.

On the other hand, if one adjust the throttle stop such that the plate is normal to the bore, the existing vacuum ports are in wrong places. Not to mention the fact that a round plate of usual thickness that is sized not to leak air will seize if it's allowed to go all the way normal to the bore. Which is worse than stopping the round plate at and angle and letting the earlier mentioned negative things to happen.

Imo000

If the vacuum ports are after the plate, why wouldn't they work? The idle air controller let's air in the same way as a slightly open plate does, doesn't it?

Strosek Ultra

I am not sure it can be made with sufficient precision.
Åke

Strosek Ultra

Butterfly throttle blades never round/circular but elliptical have been made in millions. The picture is showing a simple device to fabricate an elliptical throttle blade.
Åke

Strosek Ultra

An elliptical throttle blade will close in a certain angle. A circular throttle blade will close perpendicular to the air flow. In other words the round blade must be turned further back in order to close properly. I have not checked but I can imagine the round blade turned further back also will close vacuum bores.
Åke

ptuomov

Take a look at the ports drilled to the s4 throttle body. There are many of them, and each is designed to pull vacuum signal in a different throttle operating mode. You don't want to move the throttle plate angle at which it closes in that throttle body.