4 replies to this topic

[ciaoduc]

I noticed on a picture of the top of a BMW F1 engine with the airbox removed that the fuel injectors were mounted above the inlet trumpets and spray ahead of the throttle plates. On street engines the injectors are usually pointed at the intake valve after the throttle plates. The exception being early TBI setups which sparyed above the throttle plates but only used 1 or 2 injectors for the whole engine. The question is what are the pro's/con's of placing the injectors ahead of or after the throttle plates?

[dosco]

Originally posted by ciaoduc
I noticed on a picture of the top of a BMW F1 engine with the airbox removed that the fuel injectors were mounted above the inlet trumpets and spray ahead of the throttle plates. On street engines the injectors are usually pointed at the intake valve after the throttle plates. The exception being early TBI setups which sparyed above the throttle plates but only used 1 or 2 injectors for the whole engine. The question is what are the pro's/con's of placing the injectors ahead of or after the throttle plates?

The moto guys that I work with claim that the injectors that are way upstream are for high-speed fuel/air mixing, and the injectors closer to the valves is for low speed.

Seems logical.....especially with a high-revving engine.

[scarbs]

[Scoots]

Is it possible there are no throttle plates at all?

[desmo]

http://forums.atlasf...&threadid=31151

This thread touches on both the issues of injector placements and the possibility of using VVL/VVT in lieu of throttling. Worth a look perhaps.