4 Cam Carrera: Injectors pointing into stream instead of with?

[euro911sc]

This pic was posted in a different thread:


It looks like the fuel injectors are pointing into the oncoming stream of air?? Why? Better atomization? space constraints? Other? I have always seen them pointing down stream...

[JFairman]

Hi Mike, thats high butterfly injection and sometimes they did aim the injectors up high in the injection stacks against airflow.

When I asked if that was for better atomization first time I saw that on a mechanical injection 935 motor when I worked at Gunnar 25 years ago, I got a nod meaning that is correct.

edit: that kinda looks like a 962C motor with air cooled cylinders and water cooled dual overhead cam heads. they used a small vertical fan instead of the large flat fan on that motor.

[Jon B]

Jaguar did this in the late 50's, on the Lucas-injected D-Types, and BRM was famous for this, begining in 1962, on their Formula One engines (below). Tests showed it made engines less sensitive to variations in air/fuel ratios.

[jcge]

Originally Posted by JFairman

edit: that kinda looks like a 962C motor with air cooled cylinders and water cooled dual overhead cams. they used a small vertical fan instead of the large flat fan on that motor.

And that's a Kugelfischer injection pump at top RHS....956 I think

[Schwarzeritter]

How cool. I like these old pictures and so on.

[Flieger]

Yes, that is a 956 engine.

[sc_rufctr]

Great info but... Wouldn't the be dangerous at idle??? I'm think engine bay fires or worse.

EDIT" More about the Jag set-up than Porsche.

[Flieger]

Yeah, Lucas electrics + fuel spray =

The 956 would not be running much at idle, of course.

With MFI type fuel injection pressure there should be a pretty good cone of fuel spray when the momentum of the air is not pushing it down the intake runner. That is why it sprays below the throttle butterfly. At idle, the butterfly or slide is closed and blocks the fuel from coming out the top.

[euro911sc]

Thanks for the engine correction I still have years of learning ahead !

So if it was better for race cars did it ever make it into a production car? Why don't we see it in today's race applications?

-Michael

[Flieger]

DFI trumps all of that. It has better fuel atomization thanks to the tremendous injection pressure. That cools the charge, allowing higher compression, reduces wall wetting and the associated loss of lubrication. It can be timed for optimum emissions or power, even using multiple injection events per combustion cycle.


As to cars before DFI,

Street cars idle a lot, so would have worse fuel atomization due to fuel hitting the butterfly and condensing. Engine downsizing is done so that the throttle is open more and more often for better pumping efficiency. BMW has even used variable valve timing and lift (Valvetronic) to completely eliminate the throttle butterfly during normal engine operation.

[Henry Schmidt]

I found this MFI, hi butterfly injection on a turbo charged 2.5 liter 906.
MFI injectors pointing up. Some old school German fabricator spent countless hours on this

[Flieger]

Wow, turbo 906 motor. Was it used in a 906 or some home-built, sports-racer special?

[euro911sc]

It never ceases to amaze me what you guys pull out of your hats!

[Henry Schmidt]

Originally Posted by Flieger

Wow, turbo 906 motor. Was it used in a 906 or some home-built, sports-racer special?

It was in a wide bodied 906 basket case that was being restored to stock configuration.

Here an engine we just finished for a 904/6.

[stevepaa]

I remember walking into a shop over by San Jose airport next to the Maestro's shop and saw 4 or 5 of the four cam motors being rebuilt.
What a thing of beauty!

[Jon B]

Originally Posted by stevepaa

I remember walking into a shop over by San Jose airport next to the Maestro's shop and saw 4 or 5 of the four cam motors being rebuilt.

Jim Wellington's old shop, Rennsport Werke, 320 Martin Ave Santa Clara, once the center of all things 4-cam Carrera & Spyder.

[PFM]

Not a big fan of Henry's but he sure does nice work.