7 replies to this topic

[desmo]

I had never seen a good (or bad really) pic of how the variable length trumpets in F1 are actuated but I found this on an Italian F1 site:



I don't know what sort of engine this is supposed to be- note the butterfly throttles- not an F1, I presume. Looks hydraulically actuated to me. The length is cycled through three times in the rev range as can be seen in this chart.



According to SAE paper 983035 the stroke of the movement is 50mm and each cycle covers a rev range of 2500rpm.

[Marco94]

To add a little info to this subject. I recently attended a presentation by Willem Toet (BAR) and he told us that the airbox with proper aerodynamics and acoustic tuning would result in a maximum volumetric efficiency (airflow through the engine/displacement volume)*100% was around 120%. Main contribution was by the acoustic tuning.

Don't discount butterfly's. In 1993 Senna asked for these specifically, because it's pick up was better. Due to it's shape, a butterfly will prevent the build up of a thick fuel filmlayer.

[Halfwitt]

I can't remember where I read it, but I seem to think the Arrows / Hart V10 F1 engine from a couple of years ago had butterfly throttles. Not sure though

[jpf]

Ok I'm going to give myself away here: what other kinds of throttle are there?

[desmo]

F1 engines use what are called 'barrel throttles' now. Previously slide and butterfly-type throttles have been employed. Barrel throttles consisit of a long cylinder- one per bank- with tunnels in it perpindicular to the cylinder's axis that when rotated progressively opens until at WOT(wide open throttle) the flow passes through unimpeded. Butterfly throttles as seen in the illustration above significantly impede airflow at WOT as the shaft that they turn on remains in the airflow even when the throttles are nominally open. Slides such as are typically seen in motorcycles are better in that the airflow is unimpeded at WOT.

John Judd on the advantages of barrel v slide throttles:

"On the test bed, you can see that the engine is happier in part throttle conditions with barrel throttles. The slide actually generates a lot of nasty vortices underneath it at part throttle and you can't get rid of that. That becomes apparent when you look at the mixture readings from the Lambda (exhaust mounted oxygen) sensors. You have a big turbulent area under the slide that holds mixture within it. The barrel doesn't do that, it gives you a more streamlined flow."

[imaginesix]

Wouldn't that force the air through a 90 degree bend?

[MN]

Old Ferrari engine (1993 ~ ) ???

It looks very similar to the '92 RA122E/B VIS(Variable Induction System).
RA122E/B did 2.5 cycles, 30mm movement, 8000rpm ~ 15000rpm.
They were hydraulicaly actuated (quicker response than electric motor).
It -did- have butterfly throttles.
Your chart is showing sharp torque gain at around 9000~10000rpm then again at 12000~13000rpm.
My RA122E/B chart is showing similer curve but at 8000~9000rpm then again at 10000~11000rpm.

Interesting.....

[Ben]

Looks very similar to a Piola sketch I have from the early 90s of a Ferrari system, so I would concur with MN.

Ben