Fuel Injector Selection

[stevieturbo]

Maybe I missed it...but have you actually stated how much fuel flow you actually need ?

[timlothian]

No I havnt.

According to the Motec rule of thumb for injector sizing I would need: Engine power/number or cylinders x 5.5cc/hp = 80x5.5/2 = 220cc

As I have said before, being a motorbike engine of only small capacity and power, I wont need very large injectors. Seeing as though the most commonly available injectors are for cars, the flow rate was not my primary design consideration as almost all injectors for cars are going to flow more than this.

In my injector selection I have looked at the flow rates only to ensure they are not stupidly big (eg: 1000cc is unnecessary). I dont expect to be running very high duty cycles.

cheers

[stevieturbo]

Keeping things simple...wouldnt the easiest place to source injectors then...be from a motorcycle that already uses fuel injection ?

I know ive seen quite a few throttle body setups for sale on ebay etc complet with fuel rails and injectors. It's bound to be a decent starting point ?

[timlothian]

I did consider this much, however these fuel injectors aren't always your standard bosch, rochester....etc type fuel injector and as such, finding information about them is quite difficult.

While I'm sure I could find the flow rate of these injectors somewhere on the net, I am also interested in detailed information regarding spray pattern and spray angle. Afterall this project is part of my undergraduate thesis and it is important that I do some proper design behind things.

I know it is possible to determine spray angle and all the details through measurement of the injectors on a test bench, however I don't plan on purchasing 10 different injectors to test in the hope that one will be what I want.

As I've said before, the engine has relatively deep ports and in order to spray onto the back of the valves, and not allover the walls of the ports, I need an injector with a tight spray angle. The only injectors I have found at the moment with enough detailed information are the bosch injectors and as such I will be choosing one of these.

cheers

Tim

[MarkMc]

Just to clarify the rule of thumb injector sizing.

(Horse power required per injector x 5)/desired Lambda = cc/min

E.g. N/A, 500hp, 8 cylinder engine. 500/8 = 62.5hp/injector

62.5 hp x 5 = 312.5 cc/min

Because it is a naturally aspirated the Lambda will be about 0.88 at high load/rpm; 312.5/0.88 = 355.11cc/min

And just to finish off you would obviously choose an injector that was bigger rather than smaller. You could even add in a duty cycle adjustment, lets say 65%

355.11/0.65 = 546.32cc/min. Again choose the closest injector "erring" on the larger side.

[driftshop]

"lag" values for injectors, including USDM, JDM aftermarket and some factory injectors used for other applications

http://injector-rehab.com/kbse/lag.htm

[Holmz]

I did consider this much, however these fuel injectors aren't always your standard bosch, rochester....etc type fuel injector and as such, finding information about them is quite difficult.
...
As I've said before, the engine has relatively deep ports and in order to spray onto the back of the valves, and not all over the walls of the ports, I need an injector with a tight spray angle. The only injectors I have found at the moment with enough detailed information are the bosch injectors and as such I will be choosing one of these.

Tim - You were not joking about the difficulty in searching!
If you find any with narrow spray angles I would appreciate any info.
Sent you an emil as well to your edu.

[timlothian]

Randal, bringing up an old post!

With regards to the post, get a hold of Mark McCoy of any of the Mote guys. I have now graduated uni and so will not be organinsing one for our sae team.

With regards to the fuel injector. I did find one, cant remember whether I specifiec it above. The injector was a bosch one, as they are the only people who make available decent information. The injector had a 20 degree spray angle. If you look at the bosch-motorsport website you will find some good stuff!!

cheers

[timlothian]

by the way - email has changed: t.lothian@unswalumni.com

[Holmz]

Randal, bringing up an old post!

With regards to the post, get a hold of Mark McCoy or any of the Motec guys. I have now graduated uni and so will not be organinsing one for our sae team.

With regards to the fuel injector. I did find one, cant remember whether I specifiec it above. The injector was a bosch one, as they are the only people who make available decent information. The injector had a 20 degree spray angle. If you look at the bosch-motorsport website you will find some good stuff!!

cheers

Thanks Mate!
I'll search on the bosch site.
What are doing now that you have graduated?
Randal