25 replies to this topic

[mcerqueira]

Warning! this is a basic question!

Can somebody please explain what are all those holes on this BMW F1 engine where nice Weber carburetors used to be? And also the wonderful plumbing above each one... intake system?

[Jhope]

Fuel injector rails, and intake trumpets.

[Powersteer]

Huge fuel rails. Cam gear looks very very narrow. The angles of valve must be very narrow judging from that picture, cams are closer to each other than never before. Seems that evrything else that cannot be other than metal as written on the f1 rule book is made out of carbon-fiber.

[Engineguy]

Marcos,

You're seeing the telescopic trumpets of the variable length intake port system. They are raised and lowered by bellcranks under ECU control. And of course the injectors poised directly above the trumpets.

[mcerqueira]

Thanks for the great replies. Nice pic Engineguy! Although i'm broadly familiar with the principles of the 4 stroke engine I'm not a technical guru so...

I would thought that the fuel injectors would be sealed with the trumpets and not spraying fuel openly above the trumpet. Is there some part missing in the pic or am I missing something?

[david_martin]

Originally posted by mcerqueira
I would thought that the fuel injectors would be sealed with the trumpets and not spraying fuel openly above the trumpet. Is there some part missing in the pic or am I missing something?

The latter. Remember the induction charge is a mixture of air and fuel -- the air has to get in somehow.

[mcerqueira]

Ok, understood. I guess the airbox goes on top is missing from this pic which guarantees a controled air flow(?)

[ZoRG]

No there is no need for that ... in that pic the injectors have quite a wide spray angle, I think in reality a F1 injector has a narrow angle, almost like a straight stream.

[david_martin]

Originally posted by mcerqueira
Ok, understood. I guess the airbox goes on top is missing from this pic which guarantees a controled air flow(?)

Yes, you are essentially looking at the bottom half of the airbox sitting atop the engine in your image. The top half of the airbox is shaped to provide a suitable positive pressure and air velocity to assist charging at the sort of intake airspeeds the car usually runs at. As for the injector spray pattern, from all the videos I have seen of modern engines on the dyno, they provide a surprisingly wide "shower head" style spray cone, which is probably to assist mixing. After all, the charge times in an engine running at 18k RPM are very short and the induction velocities are very high. Getting good fuel air mixing is going to be a tough job.

[mcerqueira]

Thanks David, do you have any links for a video where I can watch the fuel injectors doing their thing?

[ZoRG]

David have you a video of a modern F1 engine on the dyno?

[indigoid]

the fuel rails don't look THAT big really. looks like a lovely setup though. this is from a nice datsun p510 racecar (2L 4cyl naturally aspirated engine):

[ZoRG]

They aren't that big... I dont think they are bigger than 550cc, F1 engines make max say 1000hp (I know its less, but for easy calculating), however this is via 10 cylinders, 100hp per cylinder. 550cc injectors will be more than enought to accomplish this at a 80% duty cycle.

[ZoRG]

Look closely at the nozzle on the bmw engine.

[david_martin]

Engine videos are not hard to find. This video is quite a nice one of the 2004 72 degree Renault engine running on the dyno with the airbox off. You can see the injector nozzles really are spraying a wide, "misty" cone that basically covers the entire area of the intake trumpet.

[ZoRG]

Thanks ... this is quite contrary to what I've read about F1 injectors before ....
you sure this isn't why renault don't have much power lol

Thanks again for the vid.

[mcerqueira]

Very nice indeed!

[mcerqueira]

One more question, the air enters the intake trumpet "freely", that is, by suction from engine (intake valve) or uses any forced system?

[ScottL]

Extremely cool! I didn't know about this injector setup. I would've thought they used port fuel injection - but then, it is, isn't it? Instead of the injectors being way down near the intersection of intake runner and port, they are further up the tube. Like throttle body injection and port injection combined...

I suppose, then, that the variation in trumpet height has something to do with throttle control and mixture?

[Powersteer]

I guess those fuel rails would look kind of small next to a top fuel drag car or a even next to a diesel engines/generators that could give electrical supply to a small town . But i think they are large compared to most F1 V10 engines i have seen. Execelent cut away buy Engineguy proves he is a spy for Mercedes-Benz.

[Pioneer]

Originally posted by mcerqueira
One more question, the air enters the intake trumpet "freely", that is, by suction from engine (intake valve) or uses any forced system?

The definition of supercharging according to the regs...

1.12 Supercharging :
Increasing the weight of the charge of the fuel/air mixture in the combustion chamber (over the weight induced by normal atmospheric pressure, ram effect and dynamic effects in the intake and/or exhaust system) by any means whatsoever. The injection of fuel under pressure is not considered to be supercharging.

And its illegality.

5.1.3 Supercharging is forbidden.

[ZoRG]

Originally posted by ScottL
Extremely cool! I didn't know about this injector setup. I would've thought they used port fuel injection - but then, it is, isn't it? Instead of the injectors being way down near the intersection of intake runner and port, they are further up the tube. Like throttle body injection and port injection combined...

I suppose, then, that the variation in trumpet height has something to do with throttle control and mixture?

Not really, the only reason you want the injector close to the valves in the head like your average car is for good fuel economy and emissions at low rpm operation, since the F1 motor does not require power/economy/emissions at low rpm's they move the injectors farther away, you get better atomization and more power and better economy on a high rpm motor with the injectors so far away...

[ScottL]

Originally posted by ZoRG


Not really, the only reason you want the injector close to the valves in the head like your average car is for good fuel economy and emissions at low rpm operation, since the F1 motor does not require power/economy/emissions at low rpm's they move the injectors farther away, you get better atomization and more power and better economy on a high rpm motor with the injectors so far away...

Makes sense. Why the need to vary the height of the trumpet, then? I'm guessing that lower revs mean less vacuum, requiring the spray to be closer to the inlet?

[ZoRG]

The reason the trumpets vary is to take advantage of inlet length tuning to get a flatter torque curve. It has nothing to do with the fuel injector spray pattern, its about getting higher VE's.

I thought about explaining it, but here is a great article that goes into detail about it.

http://auto.howstuff...question517.htm

[ScottL]

Good old HowStuffWorks.com. Excellent explanation. Thanks!!

[ZoRG]

No problem.

For interrest sake, on a honda vtec motor 1.8L running up to 9000-9500rpm by moving the injectors around 200mm away from the original location and having them inject into the trumpets of a ITB setup they gain you around 15hp, this is on a 200hp engine, so its a good 7.5% increase in power by doing this.