throttle knife edging

[bozothenutter]

been reading up on NA tuning and came across this.
It entails as I understand it the angling of the trailing edge of the leading side and the leading edge of the trailing side
the area to be removed are red.
I can see this giving more throttle openening at small opening angles.
It this done used a lotwhat are the up and down sides?

 

[bozothenutter]

last sentence should read:

is this done a lot, and what are the up and downsides?

 

[elandman]

not quite sure on the exact outcome of a mod like this.

But logic tells me that the opening gap will be slightly larger at lower throttle. So by just touching the accelerator you'll feed more air into the engine than if it were square edged at the same throttle level. Allowing more acceleration at lower throttle. It wouldn't change any power output though. The ECU should accommodate the change too.
Also the small benefit of allowing smoother airflow rather than a square edged face creating turbulence. But I reckon its negligible to nothing.

I would imagine it could just be for more response out of just touching the throttle. Perhaps to help out with right foot throttle blipping while down changing gears......
Just map the car properly and make sure there is no intake restriction and that will do the same

 

[Chip-mk1]

The standard throttle body on a clio is easily capable of flowing in excess of 200bhp without modification, so on a standard car I would expect the effects of knife edging the throttle to be nothing at all power wise.
As you mention at small throttle angles you may notice an increase in flow, which means that basically you've just made your car harder to drive accurately as who wants the car to go shooting off when you just slightly touch the throttle, its not meant to be an on/off switch? Although the plate isnt as thick as that diagram makes it looks so even this effect will be smaller than it might first appear.

People do similar with removing the wedge present on the throttle plate on some standard engines, it just makes the small angle transients horrible to map and turns the throttle into a hair trigger.

In short, dont bother IMHO.

 

[Chip-mk1]

Also the small benefit of allowing smoother airflow rather than a square edged face creating turbulence. But I reckon its negligible to nothing.

You reckon that removing turbulance (the thing that attempts to mix the quick squirt of fuel with a long drawn out flow of air) at part throttle is a GOOD thing?
Lol. Not sure you have through that one through mate!

 

[elandman]

You reckon that removing turbulance (the thing that attempts to mix the quick squirt of fuel with a long drawn out flow of air) at part throttle is a GOOD thing?
Lol. Not sure you have through that one through mate!

Turbulence at the TB is far distance wise from the turbulence needed in the chamber between the end of the injector nozzle and the valve.
Just before the injector area you want the path as smooth as possible back past the throttle body. After the injector then you create swirl patterns and roughness in the manifold and valve area to create a better mix.

have you throught it through

 

[bozothenutter]

thanks for the good info, confirmed what I thought would happen (ie more oomph at small openings)
wasn't planning on doing it, just read it in some (admittedly '70's era) books.

on a side note, would going to a smaller throttlebody speedup airflow and help with torque? or is that just with ports

 

[elandman]

Might improve lowdown torque, but sacrificing high end power since it cant breath properly when engine needs its highest throughput of air.

Either way the difference wouldn't be worth the effort involved.

 

[Chip-mk1]

Turbulence at the TB is far distance wise from the turbulence needed in the chamber between the end of the injector nozzle and the valve.
Just before the injector area you want the path as smooth as possible back past the throttle body. After the injector then you create swirl patterns and roughness in the manifold and valve area to create a better mix.

have you throught it through

You have misunderstood, im not saying wether he would effect turbulance at the valve throat or not by altering the body in such a tiny way, it was just the implication you were making that less turbulance at small throttle angles is somehow better that I was disagreeing with. But fair enough if you just mean local to the throttle body then not a problem.
Thing is though, even there why would you want to reduce turbulance, all you are going to do is make accurate throttle control harder to achieve at small throttle angles, the last thing i want from any car I drive is a tiny little touch of the throttle to make the car rocket off down the road, if I want that I will ask for it by pressing the throttle further.

 

[Chip-mk1]

thanks for the good info, confirmed what I thought would happen (ie more oomph at small openings)
wasn't planning on doing it, just read it in some (admittedly '70's era) books.

on a side note, would going to a smaller throttlebody speedup airflow and help with torque? or is that just with ports

No, especially as there would then be a step where the smaller throttle was.

Smaller diameter inlet runners all the way would help with low rpm torque, but would hinder top end flow.

The standard manifold appears to be optimised for best torque at around 5000-5500rpm

 

[elandman]

You have misunderstood, im not saying wether he would effect turbulance at the valve throat or not by altering the body in such a tiny way, it was just the implication you were making that less turbulance at small throttle angles is somehow better that I was disagreeing with. But fair enough if you just mean local to the throttle body then not a problem.
Thing is though, even there why would you want to reduce turbulance, all you are going to do is make accurate throttle control harder to achieve at small throttle angles, the last thing i want from any car I drive is a tiny little touch of the throttle to make the car rocket off down the road, if I want that I will ask for it by pressing the throttle further.

ah ok, get what you saying now. no harm no foul