Shaftless throttles for RB26DETT

[andy@amt]

30% more flow you dont get that when you take the throttle body off all together.
thanks
andy@amt

[Stachi]

It may be 30% more calculated surface. But you have to keep in mind that a round shaft doesn't have the same resistance for the air than a round one.

Apologies, my english isn't good enough to tell what I'm thinking

Nevertheless, I think those shaftless throttles are a nice piece of kit and I can see them selling quite good!

Marc

[goddard]

Originally Posted by andy@amt

30% more flow...

30% more area. There hasn't been any flow tests at all yet.

[goddard]

Originally Posted by Stachi

...that a round shaft doesn't have the same resistance for the air than a round one.

Not quite sure what you're trying to say there, but generally the shaft causes massive turbulance in the air just behind it. The "blade" system has much much less turbulance behind it. This is critical as just after the throttle the port changes shape and starts to diverger to the two inlet valves. The lower the disturbance the better.

[Stachi]

Yeah, of course What I was trying to say.. You calculated the area of the shaft like it's square, but a round shaft has a different resistance then a square one. You can't hide from the wind behind something round!

Difficult for me to explain.. Now go and mill those throttles :P

Marc

[goddard]

The cross sectional area is what it is. The area if you were to take a slice down the middle in 2D.

The short answer is yes you can hide from the wind behind something round as the air doesn't "stick" perfectly to the surface, and the fact it doesn't stick means it causes turbulence which is bad for flow. Otherwise all F1 cars would be very round.

This is a vague comparison of what the flow is like over a spindle vs a "blade". (obviously there is no butterfly on the spindle, which would help a little but I can't find an image of that)




The main reason why it is important to look at cross sectional area is that the air needs to be "compressed" through the smallest gap, no matter how short. Once the flow is choked through that gap it is a restriction.

OK, enough of the engineering lecture. I'm sure people get the idea of how this works. Get your names on the list!

[GT-R Glenn]

I calculated there is a massive 30% gain in cross sectional area from the AT throttles

This is correct, I checked his figures and they are spot on.
But, yes who knows what it will equate to in flow increase.

[goddard]

Originally Posted by GT-R Glenn

This is correct, I checked his figures and they are spot on.
But, yes who knows what it will equate to in flow increase.

Cheers bud Suprised me when I worked it out too.

[GTR--J]

These are the throttle seals. I just bought a set from XS Engineering in the U.S. Talk to Eric or Troy if you need them, I think they still have a couple sets in stock. My #4 throttle seal was leaking when I hooked it up to a smoke machine to find a vacuum leak.

[goddard]

Those are the ones that go on the injector hole yes? They wouldn't be touched as the manifold would remain as is.

[Madden]

I think they are the ones that actually go over the spindles on the throttle bodies.

[Stachi]

They're called Wellendichtring in German.. lol. But Madden's right iirc

Marc

[Madden]

Originally Posted by Stachi

They're called Wellendichtring in German.. lol. But Madden's right iirc

Marc

Theres always one

[goddard]

Originally Posted by Madden

I think they are the ones that actually go over the spindles on the throttle bodies.

Replaced on AT Throttles with a low leakage bearing, and an o-ring as well behind those little plates you can see on the cad images.

[kingsley]

I'm interested in these but won't be able to get a set from your first batch because my wife is more interested in getting the house finished and having a nice holiday. If you continue to make them as and when I'll probably be looking at a set though.

Power: 420bhp @ hubs
Usage: street

Just a quick question - does the turbulence you get from stock throttle bodies help in any way to mix the fuel with the air stream prior to entering the cylinders and combustion? I'm just asking as I don't know the answer but would like to know it.

Anyone doing an experiment with this might be wise to measure plenum pressure against port pressure and compare that with stock manifolds. If you're running turbos at their limit (which I am) then I'd expect these throttle bodies to give the turbos an easier time. The turbos will be able to produce more flow with less effort.