Injector position

[jonbarrett]

Just took a look at an F1 engine. The injectors sit above the butterflys. If it's good enough for F1, it's good enough for my AJP 4.5.

[JensenA]

jonbarrett said:

Just took a look at an F1 engine. The injectors sit above the butterflys. If it's good enough for F1, it's good enough for my AJP 4.5.

AJP is based on an F1 engine design - F1 Honda engine apparently.

[ridds]

It's all right for an F1 engine as it spends most of it's time at bonkers revs and therefore you need the injectors relatively central to allow good mixing. Up on the side of the port the fuel ends up plastered along the port due to very high gas speed.

Do it on a road car and you get terrible part load mixing so I'd leave them were the are. Also unless you know how to retain the rail correctly and ensure the injectors won't come out or detach in the event of a crash and set fire to your car I'd leave them alone.

What engine was it?

[jonbarrett]

It was a Renault. I wasn't suggesting moving them. I was comparing them to the 4.2 which I believe has the injectors under the butterflys. Or am I wrong?

[350Matt]

The main reason the injectors are above the trumpets in F1 is the required tuning length for the intake / trumpet is shorter than the best postion for the injector to allow enough time for the fuel / air to mix.

As the revs come down the injector position can be closer to the valve without detriment, however the flip side of this is that you then lose a potential power advantage in having the injector along way away as it cools the intake charge air by evaporation and increases the density of the charge for a stronger tuning effect.

The last consideration is having the injectors a long way aaway and in front of the butterlfy means that you provide lots of places for fuel to puddle up and cause running problems at low throttle angles

Matt

[GreenV8S]

350Matt said:

The last consideration is having the injectors a long way aaway and in front of the butterlfy means that you provide lots of places for fuel to puddle up and cause running problems at low throttle angles

:cough:

[HB]

what is the standard injectors? How many cubic mm cm ?? is it

[rev-erend]

What you need is 2 lots of injectors..

With the second set only switching in above say 5500 rpm ..

[350Matt]

Exactly

16 injectors all the way, 8 tiddlers below the throttle with fine atomisation for low throttle angles / revs then open up the big taps above the port when required.

Matt

[jonbarrett]

Anyone done anything like this?

[trackcar]

I'm trying to find someone interested in doing this, the emerald ECU will accomodate two banks of injectors , the MBE wont as std fit on cerbs as far as I know.

[ridds]

350Matt said:

Exactly

16 injectors all the way, 8 tiddlers below the throttle with fine atomisation for low throttle angles / revs then open up the big taps above the port when required.

Matt

And then you have to map the transitions from upper to lower which is not easy, had a play with a World Super Bike with this set up and retaining driveability during the transition was fun. If you can call it driveability on a WSB.

[mikesr]

trackcar said:

I'm trying to find someone interested in doing this, the emerald ECU will accomodate two banks of injectors , the MBE wont as std fit on cerbs as far as I know.

Joo
Looking at the MBE pin outs for other 941 configurations there are only 2 injector drivers (pins 40 and 53). The doco has examples of an upper/lower 4 cylinder and a bank a/bank b V8 but no V8 with upper/lower injectors. The Cerbera 941 also uses different pins to the standard 941s. It uses pin 40 as one of the injector drivers which is an ignition drive on the std 941.

So definitely no support for upper/lower injectors in the Cerbera MBE ECU.

BTW there are definitely some feature additions to the 'late adaptives' chip (like the histograms) so I will investigate some of the stuff we decided wasn't there in my ECU (like soft/hard cut ignition).

[jonbarrett]

I'd have a go but I'm a long way from Track car. I assume there is plenty of metal in the manifolds to machine additional injector ports. Would a 2nd solid fuel rail be required or could the new injectors be fed by hoses?