blackcloud 98.5

would i get any better performance with bigger inj. nozzles with what i have for little performance mods with soon to have a mitusa gusher pump and a programmer on the way? mostly pull a snow mobile trailer, a 24' race car trailer, and a horse trailer once in awhile but mostly highway drivin and town drivin...

13ALPHA

Sure, you have some room with all stock equipment, plus the changes you have. I am not sure how big until you are just going to smoke and run really hot though. My guess is maybe 75HP sticks. Too much above that and you will need a turbo upgrade.

HOHN

I'd suggest you consider if you really NEED a mitusa setup. *FYI-- I have plenty of FP with the stock lift pump and a big line kit, to supply injectors rated 150hp. *Never drops below 8psi.


Larger injectors have a lot to be desired, provided you can still atomize efficiently. *There comes a point injectors become more optimized for higher boost and less optimal for lower boost pressures. *Larger injectors don't JUST flow more! *It's possible to have atomization that's actually TOO good-- at high boost.
For example, if you built an injector that had like 15 holes that were tiny, it would atomize very well and you'd have amazing fuel economy and very low smoke.

But you'd only see this at very low boost and low fuel demand. *ONce boost comes up and you roll into it, you'll have lots of smoke and very low power. *WHY? *Because the velocity of the fuel flowing out of the injector is too low. *What happens is that the first bit of fuel out of the injector burns close to the nozzle, and consumes all the fresh air available to support combustion right there. *So all the fuel following it flows into an area where there's no oxygen to support combustion. *So it' just gets hot but doesn't burn-- and that, my friends IS SOOT!

So a larger nozzle can give far superior penetration and velocity, helping to make sure that more of the fuel actually gets exposed to fresh air.

That's why you'll see the interesting thing where really large injectors sometimes have FEWER holes. *That doesn't make sense for atomization-- you'd think you want more holes with a larger flowing injector, right? *Well, you do-- if atomization is all that matters..

But if you are shooting for major HP and high boost (and thus, higher RPM), it's better to get the fuel in early and quickly, and get more penetration.


Where this leads us is that an injector can only be optimized for one set of conditions. *An injector that delivers enough fuel for 500hp at 2700 rpm won't really atomize that well at low boost conditions. *But when boost comes up, the poorer atomization doesn't really matter and the injector will actually be pretty clean.


You could theoretically dial in an injector for max MPG based on exact loading conditions. *Let's say you wanted your injector to be "ideal" for 20psi of boost at 2K rpm for towing. *You could do this. *It would be something roughly around the size of a Mach Mach 2 from F1. *But this is too large to be "ideal" at lower load conditions, so it won't idle as cleanly as a tiny stock injector.

Conversely, a larger injector can "dirtier" at higher boost if the injectors take too much time to deliver the fuel.

This is what occurs with an electronic box like an Edge Comp because it stretches out the injection event. *For the same amount of fueling (in terms of milligrams), it's more efficient and powerful to deliver that fuel over fewer degrees of crank rotation. *Hence, a larger injector tends to have lower EGT and better efficiency at elevated HP level than a smaller injector being held open longer.

If you use your truck mostly to *run empty, you'll get max MPG with a small injector like a Mach 1. *If you tow a small trailer (<8K), then something like a Mach 1.6 can actually deliver better towing MPG because of the higher average boost and higher average RPM.

If you tow really heavy, a slightly larger injector like a Mach 2 will actually be more efficient when towing and give better towing MPG, but maybe slightly worse mpg when running empty.

This trend continues until atomization falls off dramatically once you get too big.

My Mach 4s would perform very well at elevated boost when towing-- the problem is that under these conditions they are delivering enough heat to where EGT may become a major problem. *Perhaps towing illegal weights with twins would put them in their "Sweet spot" and it's possible that the M4s would deliver excellent towing mpg relative to the high load compared to a stock injector with the same air setup.

Justin