Injector location effects on performance - ecotec

[Gareth]

Hi all, had an idea yesterday and was looking for input to see weather or not it would be feasable to begin development...
So i' ve been working on a drag bike that is heading for a world record, we have been looking for ways to improve performance in every way, i have only been involved in wiring to date but have been used as a consultant on the mechanics. The owner on advise from others has just sucessfully set up a shower type injector set up (eg: the injectors now sit in the middle of the inlet airflow before the throttle plates).

In theroey....

1, fuel would be slightly cooler

2, fuel has more time to blend before entering the chamber

3, better airflow due to optimised port shape

4, simple access to injectors and lines for service - you can see a poor pattern

And probably heaps more

I recommended to use caution with this set up due to the fire risks ( which proved right on first start up, it backfired with a huge fire ball result )

Sooo.... My idea for our race car was to add a similar idea to the inside of a ecotec plenum, or even holes drilled in the lid aimed at the runners. Backfire shouldn't be an issue inside a plenum. Out of all the automotive engineering books i own, i cant find the reason behind mounting the injectors so close to the valves, like on most gm and ford engines, there has to be a reason, id love to know what it is.

Any thoughts?, pros & cons?

Cheers

[vlad01]

I gather its because the fuel just sits there after it hits the valve, then it partially vaporized from the hot valve and then drawn in when it opens.

Also because of the extremely high velocity just around the valve seat, super sonic? the fuel is atomized on its way in if it isn't already. So I think for day to day cars it more practical to manufacture injectors down on the intake it may even be better as I seen manufactures strive to get closer to the valve as possible, now even direct injection. I would also say it would have better cooling effect when its vaporizing in the combustion camber rather than before it absorbing intake heat instead of combustion charge heat.

[Gareth]

Please correct me if im wrong, aren't ecotec sequential in their injector operation, versus 808 banked left to right firing? In other words doesn't get much time to sit on the back of the valve?

Would reversion become a problem at low speed in a plenum?

[Gareth]

Looks like this

http://www.buellxb.com/Buell-XB-Forum/E ... -bodywork.

This isn't the bike we have been working on, just a google random

Seems to be a popular mod on bikes

[The1]

on ecotecs the pcm has delay times, you can play with the timing of the whole injection event, typically when tuning you find the delay point when it richest, meaning you are getting the most amount of fuel into the chamber, which is the whole idea of injectors to try and mix the fuel and get it into the chamber and create a better bigger burn, having the injector pre throttlebody makes getting the fuel mixed and in the cylinder much much harder.

[delcowizzid]

flowing fuel through the stock allready to small runner will limit flow even more and will result in a lot of fuel pooling out on the runners.in operation the whole runner fills with fuel droplets in vapour.we had a buick with custom top and 90mm TB you could open the throttle and see inside and there was a half tennis ball sized vapour dome at the end of the runner was pretty cool.if you were planning on sustained high rpm running 7000-9000 rpm then it could be worth injectors up high like some of the racers used in the buick nascar engines some ran stock location some run in the plenum top with a massive plenum

[Circlotron]

having the injector pre throttlebody makes getting the fuel mixed and in the cylinder much much harder.

At part throttle for sure, because the fuel spray is going to smack into the atmosphere side of the butterfly then dribble to the edge and get picked up again by the air stream. Very much like an SU carburettor. On a drag bike though, once you are under way the butterfly is edge-on and pretty much out of the picture.

[Gareth]

So... what im getting is that this set up is more suited to engines that run on sustained high RPM???

[vlad01]

So... what im getting is that this set up is more suited to engines that run on sustained high RPM???

yes like FI engines. Though they have pretty short runners and very high rpm


[youtube]https://www.youtube.com/watch?v=y2iBbwocYZw[/youtube]

[charlay86]

cbr600rr has 2 sets of injectors, one set in the usual place near the ports and another set in the plenum pointing down the guts of each inlet runner. the second set are activated at higher engine speeds.