Types of throttle body

[Rubinho]

Most regular cars use a throttle body with a pivoting butterfly to regulate the flow. Some high spec versions (and F1) use a rolling barrel style throttle control.

Looking at the insides of camera today I was wondering if there would be any benefit of using aperture control type flaps in a throttle. This way there would only ever be a (nearly) perfect circular hole to admit the intake air with zero restriction on WOT. Would this be an improvement on current matters or would the turbulence after the plate (like with an orifice flow meter) on part throttle negate the benefits?

I can see there being an issue with the fact that the area of a circle goes up with the radius squared, to get a linear throttle opening motion this would have to be regulated mechanically (or electrically if so actuated). Would this be a real world problem?

Does anybody know if this has been tried before?

[GolddustMini]

would be a pain in the arse to completely seal it between each of the flaps

[Richy_Rich]

Agreed. And it would also be difficult to make it strong enough to withstand the induction pressure (and any accidental backfires).

Actually, it would be hell of a difficult to make at all, wouldn't it?

[GolddustMini]

and surely there would be no advantage over a barrel throttle (i.e no restriction in the throat of the throttle -usually filled by the spindle and butterfly in a conventional throttle)


it may create less turbulence around the moving parts thats about it, seems like it would fundimentally by a complete b*tch to manufacture just to give the same results as a sliding plate throttle which is a damnsite easier to manufacture (think a sluce gate)

[StephenRae]

A racing engine is either on or off, so it doesn't really matter. Years ago I made a restricter plate for a water cooled supervee. I made the holes eccentric to the inlets, it worked well but I worried about the excess fuel pooling in the trumpets, upstream of the restricter plate. I remade the plate, offsetting the holes so that their was a smooth path at the bottom of the inlet tract. Driver complained so I put the old one back!
I must have blundered on a way of richening the mixture just when it was needed, when the throttle was snapped open.

[GolddustMini]

Originally posted by StephenRae
A racing engine is either on or off, so it doesn't really matter.

im not sure on at being factually correct really.....

[avsfan733]

well factually yes but what hes saying is that it is either full throttle or no throttle....I disagree with that statment. Throttle control and the smooth curve of a throttle opening is important and is harder to achieve with a barrel throttle often causing from what i have found an off idle stumble because of the condition of increasing flow that Rubhino mentioned. I still think it is the best option, and have always looked at the other alternatives such as the iris style but theyt have to many drawbacks. I can see huge problems with jammin if the engine is coming off of idle (high vacuum application) possibly flexing the leaves downward. plus the way f1 cars use them they have ten.....ten irises would be big and pretty heavy to take the force and thats mounted all the way up on top of the engine

[StephenRae]

avsfan...surely a mechanical means of smoothing the transition between closed and open throttle would only serve to mask the inability of the carb/injector to cope?

[shiny side up!]

Originally posted by StephenRae
avsfan...surely a mechanical means of smoothing the transition between closed and open throttle would only serve to mask the inability of the carb/injector to cope?

How you handle the mechanical end of things has a big impact on how effective your injector control strategy (map) will be. There are certainly better mechanical setups for throttling that transition from closed/part throttle to WOT than others.

For a easy example of good/bad flow, think of pouring oil out of one of those funny shaped quart bottles. If you were to just turn one completely upside-down, the oil comes out in big 'gulps', not smoothly at all. If you turn the bottle smoothly and in the right orientation, oil flows out smoothly and quickly. Now if you imagine that oil as air going into an engine (I know, funky example...), obviously getting air uniformly as in case 2 would be much better and easier to create a fuel map for than case #1...

Did that make any sense at all???

[shiny side up!]

OOPS, Double Post

[avsfan733]

why is that? if you could smooth the airlflow thats a plus no matter what the carb and injectors should be designed tnot to cope but to provide the best mixture control possible the injectors and carb aren't there to compensate thats why you have the throttle to control the level of "go-ness" (lack of a better word) and the injectors are just feeding the beast

[Rubinho]

I was initially thinking of road-car style engines with one throttle body followed by a diffuser and a plenum. In this particular case, smoothing the airflow through the TB would minimize the losses associated with turbulence pre-plenum thus maximizing the flow into the plenum. The plenum will have good effect at smoothing the flow as it goes past the injectors and into the cylinders (that's what it's there for).

In an engine with one TB for each cylinder, I can imagine the quality of the flow past the injectors would be important. Question is what's best? A smooth flow that maximises the flow into the cylinder or a slightly turbulent one which will help with air/fuel mixing?

[cannardd]

The new BMW Valvetronic engines are a very nice solution.
They don't have a throttle at all, just a fully open intake.
The throttle function is done by altering the valve lift.

see:
http://www.bmwworld.com/technology/valvetronic.htm

[avsfan733]

actually while that is true, they also have an adjustable intake track length which helps the ability to do that

[cannardd]

Many cars have variable intake tract length now, including Alfa 16V TS & JTS engines.

And BMW's issue of loss of efficiency over 6000RPM due to heavy valve springs wouldn't be an issue on a full race engine if you used pneumatic valve springs.

[StephenRae]

Most of the developement of the I.C. of recent years have been electronic, all of which are over my head. It is refreshing for me to actually understand the principal of valvetronics, although it's hard to get my head round the fact that an electric motor in such an aggressive envireonment would be reliable.