re-positioning injectors, worth it?

[joecoolmk2]

i've been toying with the idea of moving the injectors further up the runners, in an effort to get a better(more complete) fuel mixture and possibly a power/torque increase.

anyone with suggestions? this is on my 1uz, i was gonna move them to a position above the openings of the runners, like a lot of the ferrari and porsche race cars.

i've seen an article in a magazine about a guy that did the same thing with an old falcon six, with big long trumpets, he'd trialled it with a few different injector locations, and he actually got a decent amount of power.


any info appreciated

[Robbos_Toyotas]

depending on your desired outcome, it could be worth it. Having them a bit further up...like adding runners to some degree should give you more low down torque. I'm not certain, but you may sacrifice a bit of top end power though?? depends what you are after...

[YelloRolla]

I recall reading the one about the bloke with the falcon six who did the test for his thesis.

I do recall that the car made higher peak power with the injectors at the top of the trumpet, but is this really more power? A better way to quantify the result would have been to time the rate of acceleration.

[mrshin]

Guess it depends what you intend doing with the car. For racing purposes, I'd say do it, but I probably wouldn't recommend it for a daily driver, for various practical reasons. I highly doubt the legal aspects of it on the street, too!

[joecoolmk2]

Guess it depends what you intend doing with the car. For racing purposes, I'd say do it, but I probably wouldn't recommend it for a daily driver, for various practical reasons. I highly doubt the legal aspects of it on the street, too!

it's gonna be a closed plenum, not open trumpets. there shouldn't be any legal problems with that...

i was goin for more torque in the midrange, and topend. but what else do i need to get more revs?(lift the limiter)

[mrshin]

Well, inside the plenum should help to contain backfire risk;-) I guess the other thing is it might be a touch grumpy when cold, if that matters.

I'd certainly be interested to hear how it goes if you do give it a go though.

[Norbie]

Methinks this would be one of those situations where you'd need to try many different injector positions and spend hours and hours on a dyno to determine which works best - otherwise you're just as likely to lose power than gain anything.

[kingmick]

yes it can be worth it, if its not optimal because of production design. with race engines they have the benefit of hours of engine dyno time to get the injectors at the right height and spay pattern so you get optimum atomization. there is HP in it but it isnt huge 10-20HP in a race engine such as a chev out of a V8 supercar. to them its worth while because they need all the HP they can get out of the revs. they are at the peak now so for the last few years they have gone as light as possible with the rotating assembley. they use I-beam Oliver rods etc to spin the engine up quicker.
if you have the money to play with placement go for it.

[tricky]

For a road car, I wouldn't bother.

At cold start, it'll make it grumpy as hell, because the fuel will condense on the runner walls more than a closely placed injector (because it has longer to travel). This means you'll have to dump in more fuel to compensate. On an otherwise standard 1UZ, the benefits will be marginal. It might give you 5hp, but it won't do much for the midrange.

If you really want to do it and maintain driveability, do staged injectors (EDIT: probably entirely impractical... 1UZ = 16 injectors ). Keep the stock onesfor the first part of the powerband, then deactivate these at, say 5000rpm and run the injectors at the end of the runners.

It means a shitload of dyno time to do it right, basically.

[joecoolmk2]

yeah i see the points you guys are saying. basically a lot of effort for possibly no gain or in fact a loss. i think i'll be putting that idea in the bin now.

i might see if i can find that mag and read it again though...

[Cameron_Datto]

Have a look at this web page as it will help with the myths of injectors positions , Also the type of injectors and spray pattern are other things to consider ,,, Cheers Cam :>)

http://www.injec.com/techdata/tag-In...cteristics.pdf

[kingmick]

i cant be bothered looking so give me the gist of what it says cameron please!