Custom Injector Logic: Designing an injector around alcohol

[Begle1]

I have two goals with my truck (that are germane to this train of thought); I want to be able to drive around daily with no smoke, and I am going to fumigate as much alcohol into my engine as I possibly can.

In order to get the most out of alcohol, you need to run (relatively) retarded timing and have a good ignition source. To that end, I think I need an injector with a fine and wide spray pattern, but with a (relatively) small fuel flow rate.

From the very little I know about injector design, I think that translates into something with as many possible holes that can fit, but with all of those holes tiny. Large holes that give me more fuel than I will have time to burn are a liability; not only will they undermine my goal to be a smoke-free daily driver, but if I ever find myself with a lean mixture then the extra fuel would just smoke and afterburn in my manifold. And theoretically, smaller diameter holes let you add more holes in a given tip (in exchange for a smaller total hole area).

So I want an injector with lots of tiny holes and a wide spray pattern. Wouldn't a 9mm injector like I have be more suited to such a pattern than the 7mm injector? To compensate I'd have to get my head stitched to prevent cracks, but that's only supposed to cost $400... And I can just save up to do that along with the O-rings and porting that I'm going to need sometimes anyways.

At the moment, I need new injectors, which even if I were to go stock would cost $400. It would be one heck of a leap for me to spend the extra $800 or whatnot to get customs made, but if I can get some like I'm envisioning then I would be able to run them without too much modification to my existing set-up and not be over-fueled. And they'd be perfect for my long term goals.

But it also means that I'd be spending the $800 I have in the Emergency Injection Pump account...

So, could anybody talk me out of it or tear apart my reasoning for it? I'd be appreciated...

[KTA]

Combustion dynamics are very complex, and your theory about tip design may or may not be correct for your application. You may get the injector you want built and find it smokes more and makes less power than what you had. The all knowing Don ~ M when he first started argued with me that more holes in a tip were better and I said not necessarily. Anyways he was making 14hole tips at the time, and they made decent torque, but were low on power and smoked alot, he has since gone back to more conventional number tips and power has increased along with decreasing smoke. Basically what I am saying is if you plan to experiment don't be surprised if it doesn't work as you imagined.

[Begle1]

Do you know how much of a leap it'd be from what exists now? What's currently the smallest, many holed injector?

[KTA]

Industrial injection makes a 10 hole injector for the 24valves. For the 12Vlave applications I find most injectors are 4,5, or 6 hole, I am not aware of any successful tips for them using more holes. The 12V head has less swirl by design than the 24V head and seems to not like injectors with more holes, probably an 8 hole would be the max.

[DLittle]

Begle1

I've got a set of 8x11 tips in 1st gen bodies. I ran them for about 3k and took them out because they smoked like crazy and had high egt's. I didn't see any gain in power from my 5x12 tips in fact they felt like less power. I'm going to use them as cores when I get my next set of injectors.

[Begle1]

Yeah, well, that sounds about right DLittle...

They must spray fuel in places where fuel isn't supposed to burn.

Ever hear about those injectors running with propane or alcohol fumigation? I have a hunch that they'd clean up really well. A fumigated fuel should counteract a lack of swirl in the combustion chamber...

[KTA]

Why not just take the injectors and VE off, add a distributor and spark plugs and run it off alcohol? That should burn pretty clean and make good horsepower.

[Begle1]

Do you think that my "alcohol will clear up DLittle's injectors" logic holds any merit, Brian?

I have played with the idea of tapping some spark plugs in next to the injectors. I could light off the alcohol a little bit before the fuel was injected that way...

But spark plugs don't add 200-400 HP worth of fuel into the mix whenever they're fired.

[KTA]

You would have to be running on alky just to clear the smoke up while cruising to meet your goals and personaly I don't feel that is practical. Oh and I know of a strictly alky powered 5.9 that is in the 2000hp range, so it is very doable with spark plugs. LOL It uses alot of fuel though so it would probably be tough on the budget.

[Begle1]

Where are those engines at? Alcohol powered sled pullers?

Do spark plugs ignite the alcohol faster than injectors do? Why only use spark plugs?


You could run propane instead of alcohol for daily use... It'd be easier to find and cheaper. I wouldn't really want to do that, but I'd be willing to bet that those injectors would respond very well if you used either.
And I think low-compression pistons would compound the beneficial effects.

If I can get some kind of alcohol or propane system together quickly, I'd almost consider buying those nasty injectors off of DLittle just to see if I'm right...

[KTA]

Yes they are alcohol sled pullers, but cummins builds a natural gas version of the 5.9 that already has spark plugs and low compression pistons, they run like 9:1 as opposed to our 16.5-17:1. They use spark plugs so you can ignite the fuel at the proper time. Running alcohol or propane as you propose is a recipe for disaster as you have no way to control when ignition occurs. This is why the powerstroke guys that liked to play with large quantities of propane used to bend rods and blow head gaskets as its an uncontrolled combustion event.

[Begle1]

The way I've understood it, is that the idea with propane or alcohol is that the autoignition temperatures are so high, the fuel won't light off until the Diesel is injected and burns.

When the combustion chamber temperatures are getting to the autoignition point of the fumigated fuel before the Diesel is injected, things are too hot. You get preignition and ping.

Lower compression pistons help prevent getting to that temperature, as does water injection, nitrous, efficient turbocharging and smooth airflow. You have to keep cylinder temperatures between 500 degrees and 850 degrees to guarantee not breaking things.

If the fumigated fuel is lighting off due to compression, it doesn't matter if you're using injectors or spark plugs to ignite it; it's pinging all by itself before the point your timing is set to. That'd be just as dangerous in a natural gas engine as a Diesel engine, just rarer due to the super-low compression pistons.

But I know I'm missing something, as propane ping gets more likely as you inject more of it. Or does it just get much more noticeable?