throttle to valve distance

[jezza323]

cool, thanks for the bill, just wanted to make sure i understood what you were saying

[ed]

another agument can be made for putting the throttle plate at a node or anti node of wot wave harmonics - i havent convinced myself entirely of how this works yet, but its something...

otherwise, as bill says, stabilise the airstream

[jeffro ra28]

Bill, why would we want to stabilize the airstream at part throttle in a race car? Or is the purpose more of a street car? Surely the focus wouldnt be entirely for this purpose.
Dont get me wrong, i have never driven a race car, so i dont really know, only race bikes, but i sure as hell didnt 'race' around on part throttle.

[Billzilla]

Bill, why would we want to stabilize the airstream at part throttle in a race car? Or is the purpose more of a street car? Surely the focus wouldnt be entirely for this purpose.
Dont get me wrong, i have never driven a race car, only race bikes, but i sure as hell didnt 'race' around on part throttle.

You use part-throttle more than you realise.
Even in my little racer, I still have to work the throttle. In more powerful cars it'd be more important.
For road cars, I think you'd get a slight improvement in power & economy, but very slight.

[jeffro ra28]

So are we trying to optimise part throttle response and or power? Obviously if we are on part throttle, we are not needing the power of WOT. So may i ask why it would be important?

[Billzilla]

So are we trying to optimise part throttle response and or power? Obviously if we are on part throttle, we are not needing the power of WOT. So may i ask why it would be important?

Well it's no harder to get it right than it is hafl-right, so why not do it that way?

[jeffro ra28]

I dont understand mate. Sorry. I just think there is far more logic to it then that.
I know some 'cranky' engines tend to 'stagger' at part throttle, maybe its to minimise this?

[The Real Roadrunner]

If your after throttle response, just make the runners as short as possible. If you want more torque... use longer runners with a plenum (see the foul can variable runner length system)

Of course with a 20V's high RPM power band, long runners are going to make 3/5ths of fukall difference to your torque down low, and will just hamper high RPM throttle response. So in conclusion, for your system, make the runners as short as practically possible.

not meaning to be a PITA but this doesnt ring true to all engines and certainly not a 20v.

having the intake as short as possible doesn't always increase throttle response.

nor does a long runner setup hamper topend, this i can backup by the fact that we went from having a length from tip of bell - back of valve being 8" and made 160hpatw NA we then increased it to 12" and power came up to 185hp on the same car within 45min of the first run.

so i can definately say its alot more complicated than just 1= better throttle response and 2= more lowend torque.

by going longer we had more power everywhere above 3400rpm, and the engine is a blacktop 20v.

cheers
linden

[Sam_Q]

I guess if it is ideal to have the throttles at the end the only real compramise in the manifold design is that the trumpet length which becomes rather limited in its adjustment. For a race car this is obviously irrelevant because everything is tested on a dyno in every setup, however for someone such as myself who only wants to make one manifold but am prepared to make a few intakes its trickier.

[jezza323]

you can always start with a manifold + trumpet at the minimum expected length you will run....then run a few different length trumpets....it may not be ideal, but it will still get the throttles out at the end of the runner (instead of very close to the head)

then once you are happy, you can make a longer manifold if you think it will give you a gain of any kind

[Kyosho]

So are we trying to optimise part throttle response and or power? Obviously if we are on part throttle, we are not needing the power of WOT. So may i ask why it would be important?

How often are you at full throttle in a corner?

[jezza323]

i think the point he is making is....if you are at part throttle, you are not wanting max power...so even if the motor was making more power at a particular throttle opening, you would probably need to use slightly less throttle anyway

[thechuckster]

How often are you at full throttle in a corner?

depends whether you want the arse of the car to exit the corner at the same time as the front?

[oldeskewltoy]

Yep, have the butterflys right out near the end, like this ->

Hmmmmm I wonder if this is part of the reason many people felt the throttle response of the early TVIS engines were better than their higher hp later counterparts......


Bill... would the same hold true for single T/B as well as ITB???

[MWP]

Bill... would the same hold true for single T/B as well as ITB???

My name isnt Bill, but i would say no.
There is a point at which moving the TB further away will start to greatly effect throttle response and provide no smoother airflow.

With a single TB, the mass of air in the plenum and runners already steadies the airflow quite a lot. Moving the TB further away would make next to no difference in the actual intake airflow and just decrease throttle response.