Enthusiast

Any truth to this? I have heard that if you have a larger injector that is running say 60% duty cycle that it does not mix the fuel as good or make as much power as say one at 85% duty cycle. Anyone have any input or experience with this.

bigdsz

iTrader: (1)

Me and a friend of mine were getting ready to go with Racetronics 42#. I'm 430 rwhp and out of injector. My friend is 450rwhp soon to be like 470 rwhp. Paul at Thunder convinced us 30# SVO's are all we need if we don't go FI. He claims they are running the 30's with 402, 408, and 427's.I don't think anyone can question Thunders successes.

V8_DSM_V8again

Atomization depends on alot of things.

1. Below the limits IDC is'nt as important for atomization as fuel pressure.
At high fuel pressures the atomization tapers off.

2. A ball injector will be better than a std pintle...

3. A smaller injector may idle better but a larger injector even when both are flowing the same amount of fuel can target the most opportunistic times in the intake cycle as RPMS increase and the window narrows... Injection end time. Injection angle.. There are a few terms for it but its the timing of the injection event...

You could have to run so much IDC on the little ones that it puddles a bit since it starts to inject too far before the intake pulse is going anywhere. With the big injectors it can feed out what the engine needs at the perfect time to do it with out having to start fueling early.

Also it is'nt just the size alone but the app.

160lb (1680cc) on race gas idle like crap... Ethanol... Fine

On gasoline

I once had 660's that were easy to get to idle but hard to tune for peak power. I went to 800cc's and on pump gas it would idle fine but with Vp116 it was harder to get the idle perfect.. It made more power on the 800ccs despite my calculations showing that I was flowing the same amount of fuel. Just way more optimum injection timing. You need to run 93 octane richer than the 116 due to the o2 in the fuel which explains why it could atomize better at idle the richer pump gas mixture...

It is a balancing act...

bigdsz

iTrader: (1)

Everything you state may be true all I know is that I was going to go with bigger injectors and Paul at Thunder convinced me it was not in my best interest. If I continue to go lean at 6,000 + with the bigger injectors and new Racetronics fuel pump then Thunder will have some explaining to do.

V8_DSM_V8again

Yes if you stay NA.

With FI the reg increases fuel pressure with boost so that the presure differential across pintle to the intake is the same.. Basically they would act like 23.5psi fuel pressure at 20psi boost if it did'nt.... A NA car can run a higher base pressure and do more with smaller injectors.

Enthusiast

So for a h/c car I would think it would be best to run 42# to make sure you don't run out. I have heard of SVO injectors failing b/c they are a little longer, anyone know anything of this?

Full Throttle

If the car is properly tuned then you just need to use the injector that supplies enough fuel for the amount tof HP you are making, if the 30 lb injectors are big enough then switching to a 42 or 60 lb unit will not help a bit, if you already had enough fuel you didn't need more. But they will not hurt a bit either provided that the bigger units are properly tuned the only problem I could see is that if the bigger units were not tuned properly they may provide too much fuel and there would be some loss of power. But if two different size units both deliver the same amount of fuel to the motor at the same time the result should be the same
Mike

Enthusiast

Bingo, and I only wanna buy injectors once, hence the reason I think I may go with the 42# even though they may be overkill. Hell I like killing cats with elephant guns. j/k

BriancWS6

iTrader: (18)

I had 37lb racetronics in my last car. It was only putting down 358 through the verter when I had it tuned for them and the dry shot. No problems at all. Ran high 11's on motor and super low 11's on the juice.