Twin butterfly throttle bodies
Turbo Mini Forums

Hi all,

Just a quick question... whats the point of twin butterfly throttle bodies?

I.e on the R1 engines, one set is controlled by the accelerator cable and the other an electric motor?

Why?

depends where there mounted. Uses i have seen:

to induce swirl (blocks one runner to one valve of a pair of inlet valves in a 16v engine / blocks a larger more direct inlet runner)

to increase low down torque(same setup as above really)

Traction controll

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

On bikes I think they can be used as a form of traction control, as Denis says. Basically not allowing you full throttle when it would most likely kill you.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I have a set of the R1 twin butterfly TBs here.

They were done to improve low & mid range torque. Top end power was the same.

Same concept as the exxup system then ?

=> too much flow = not good for low end torque

Rusty by nature

Twin bodies are really pleasant to drive, this is what I have on my Mini (that comes from a Polo GT 1.3L), this is what we have on Maserati biturbo. This has nothing to do with the air speed, much with a fine torque control by your foot, you feel when you start asking for more torque. Even if boost comes violently the small body prevents power from climbing quickly (even more dangerous on R1).

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Like preventing torque bump ?

Up to a point, the torque bump is what we are all looking for, isn't it ?

I totally understand that on such applications as a Maserati biturbo or a sport bike they are good to have as speed is control but was it really needed on your mini ?

Rusty by nature

It's not to prevent something, it's to control better. The gas pedal controls the torque you demand from the engine.
A throttle is a restriction, the volume flow is physically limited to a value defined by its cross section. This is true for 1,2 or any number of TB, this is the only way we have to control our SI engines.
If you have 2 TB the first (small) one is used to control light loads, the second one is for high loads. The first half of the pedal displacement will allow say 25% of power, the second half will do the other 75%, so you can precisely control light loads. When the second TB starts opening the pedal becomes harder, your foot feels it and this helps controlling the torque. You can link this threshold to the boost management, for example limiting the boost to a minimal value while on the first TB.
It does not matter whether you have a 300hp or 50hp engine, as long as the TB are properly sized.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Ok thanks for the replys... looks pretty useless for what im doing so I will just rip the second set out and just use one set like normal

Cheers for the comments

Chris