can you have a throttle body thats to big?

[kingmick]

90mm is a bit big!
staggered setups are the way to go for all out and for drivablilty, if you can find one to suit your needs!
i posted a couple of pic's of a staggered setup a few weeks ago in tech, not for a 4ag but for another make.

[Earlyrolla]

Yes, the less restriction to the intake air the more power the engine can potentially make. But to clarify what other people are describing, the potential increase in power versus the change in throttle body diameter past a certain size will be negilable.

How many people actually drive round at WOT all day long anyway? (street car...)

When I helped Nick set up his MR2 with the 4AGZE and the SC14 we used a V6 commodore throttle on the intake to the supercharger. And that has the progressive throttle as described by brett_celicacoupe. Personally even that throttle is probably a touch big, although Nick would be the best to answer that as its his car

If you want a staggered throttle then look at the early injected Camira's as they have quite a nice one. The only problem with using that sort of throttle body is it is much harder to plumb as the inlet to the throttle body is oval.

[Mr Revhead]

from what iv found a 3sgte one is a good one to use
also the bluetop one is about 10mm bigger iirc

[pilot]

Quite an interesting air speed that you've mentioned there.

Given that airspeed (approx 660 ft/sec) then the 4A GE will require a single T/B of around 27mm diameter (assuming 110% VE and 7000RPM). Now that's a small throttle plate.

Have I missed something?

I´ve been away, sorry for answering so late.

It´s been found (after much testing) that this number gives the best compromise between air speed and losses agains´t walls. Please remember that the Mach numbers is very dependant on fluid conditions (temperature and pressure, mainly).

[YelloRolla]

I understand that mach 0.6 relates to the intake valve, the amount of lift, and the bore and stroke.
Is this incorrect?

[pilot]

I really don´t understand what you mean by that.

In normal air conditions, Mach 0,6 means that it is travelling at 600 km/h. If the pressure or temperature changes (also other factors), it might be travelling at 600 km/h but not being at Mach 6.

[YelloRolla]

Mach 0.6 is 735 km/h.

What I mean is that 0.6 is the theoretical max speed of the air as it goes through the valve (the intake valve), when the valve is open to it's max lift, and the piston is around 70-120 degrees past TDC.

This is my understanding of the relevance of Mach 0.6 as it relates to the intake of an engine.

Are you quoting the air speed through the throttle? Because this is how it seems, I am just not understanding why you have quoted this number relative to throttle size.

I am guessing that I have missed something.

[pilot]

Mach 0.6 is 600 km/h for a speed of sound of 1000 km/h.

This number must be taken into account for head and intake runners (and as many parts of the whole intake system as you want/can). Speed at the intake valve will be significantly higher.

The throttle, as part of the intake system, can be studied in the same manner. To that objective, you might want to think of it as just a tube with internal diameter similar (or a bit smaller) than that of the throttle plate and make necesary calculations to achieve a Mach number close to 0,6 at desired engine conditions taking into account particular air factors (pressure and temperature, mainly).

[go_the_datt]

0.6 speed of sound = 735.026 4 kilometer/hour
1 speed of sound = 1 225.044 kilometer/hour

660 foot/second = 724.204 8 kilometer/hour

all taken from http://www.onlineconversion.com/

[twentyEight]

0.6 speed of sound = 735.026 4 kilometer/hour
1 speed of sound = 1 225.044 kilometer/hour

660 foot/second = 724.204 8 kilometer/hour

Correct! (@ QNH 1013)

I know it more as mach 1 = 661.5 knots, but that's because I work in Air Traffic Control...

Mach 0.6 is 600 km/h for a speed of sound of 1000 km/h.

1000 km/h is only mach 0.82!

[pilot]

Since when speed of sound is a constant value? it varies with pressure, temperature and other factors.

Mach number is a given speed divided by the speed of sound in the same conditions.


It really doesn´t matter here. My value in km/h was just to exemplify, don´t take it as a target. What I wanted to explain was that the value of Mach 0,6 (which doesn´t equal to a constant value times 0,6!!!!) is the best common compromise for a performance engine.

[twentyEight]

Since when speed of sound is a constant value? it varies with pressure, temperature and other factors.

From what I remember, the speed of sound is generally varied by temperature!

That's why the standard is set @ 15 degrees Celsius at the standard 1013Hpa (QNH 1013) which is means sea level pressure! (Avergage pressure @ sea level)

[pilot]

There are other factors that modify its value. Again, my objective wasn´t lecturing anyone about fluid dynamics.

[ed]

Since when speed of sound is a constant value?

lol! worst excuse evah for getting the speed of sound so grossly wrong!!

by your way of reckoning we should also take into consideration the theory of relativity, and alter our measurement of the dia of the throttle plate with increasing speed??

the mach 0.6 number refers to the peak and hold lift valve flow rate, not the throttle body flow rate.

jasons other numers also make far more sense too

[pilot]

So you say that Mach 0,6 would be exactly the same speed at atmospheric pressure and, for example, 1 kg/cm^2 of boost?

Speed of sound is a highly relative value, not a constant one. It is much more true for a system where pressure and temperature varies so greatly like and intake system from a forced induction engine.

You can make calculations without taking into account the lift of the valve and get ver accurate results.


If you know this subject so well, please explain why Mach 0,6 is the best value for this purpouse.