Calc'ng Injector size against airflow, How?

[MAXLLY]

So we install a new charger, get a little more air, increase the fuel a bit to jive ,perhaps a little different delivery point and we're good to go.

What if...(not hypothetical, i really need to know) We install a huge single or compounds and we flow say... 100lbs of air? A GT-47 for example... how do you calc the fuel requirments? This is not a WAG number somebody must know how to get close? Am I looking at the wrong point?

The goal in my simple mind is trying to keep rail and duration in the "window" for optimum performance. Anybody know?

Thanks guys, if there is another place you've seen this let me know

 

[MAXLLY]

So we install a new charger, get a little more air, increase the fuel a bit to jive ,perhaps a little different delivery point and we're good to go.

What if...(not hypothetical, i really need to know) We install a huge single or compounds and we flow say... 100lbs of air? A GT-47 for example... how do you calc the fuel requirments? This is not a WAG number somebody must know how to get close? Am I looking at the wrong point?

The goal in my simple mind is trying to keep rail and duration in the "window" for optimum performance. Anybody know?

Thanks guys, if there is another place you've seen this let me know

This must be a "double tough" one? Is this a tarded question, maybe i should be looking at something else? Perhaps the rule is double the air... then you use a 50% injector for double the fuel. I realize this is oversimplification, could it be this simple? If I'm off base let me know.

Otherwise just tell me to pound salt.

 

[sweetdiesel]

I dont think any question is retarded!

But the formula you are requsting? it should be more like this how much fuel is required to spool a gt47 and what is the best way to obtain this fuel?

now, if you asked that question

i would say duel cp3 is going to be needed before injectors for a gt 47
because thats gotta be a fuel munger

ill send you a email on injectors and figuring out how to formulate them properly
however it is for gas tuning but it kinda works to give you a idea


this is just my opinion,take it or leave it

 

[Killerbee]

You could use equivalence ratio, its a kind of fuel to air ratio. There is a custom pid formula floating around that will let you log it. I am sure the turbo has its own ER characteristic, that lets it spool best, some needing more fuel than others. The stocker works well at 1.1

 

[MAXLLY]

Thanks Killerbee and Simon. Grateful again...

I just needed a jumping off point, a reference, versus a WAG.

 

[LarryJewell]

I'll send you a file at lunch, not sure it will help you, but it couldn't hurt!!!

 

[SBCNX20]

Lots of fuel may, or may not be the way to spool a big charger, some people have good results with less. I for one have witnessed this myself on a gt42 equip truck. We thought MORE,MORE,MORE all that did was fog the lights! LOL There is a balance u just gotta find it (or) get some help from someone who knows! THANKS U KNOW WHO!

 

[MAXLLY]

I'll send you a file at lunch, not sure it will help you, but it couldn't hurt!!!

Thanks Larry, Mike has somethin' as well. Don't wanna sound redundant... What i am after is fuel injector increase over stock after all the standard mods are done.

IF my brains wrapped around it this is what i understand.

When we have reached the "edge" of a stock injector capability (duration is to long), what size do we need? 20% larger? 50% larger? 80% larger? 20mm3? 50mm3?


I guess i need to consider pilot... it could be used could it not?

 

[McRat]

I've run way past 700rwhp on stock stick on fuel with LLY injectors, and I do not know what the limit is.

Can you hit 1000hp on factory injectors? Maybe someday I will find out.

For now, I would not spend money on injectors until someone proves they actually add HP with all things being equal.

Once again my racing thingy is interfering with my testing thingy. I went to the dyno to test injectors again, and something stopped us.

 

[SBCNX20]

I think BUCK just listed almost all his mods on the Diesel Place and is running K.D 40% so you should (unless you are planing on running faster than 9's) be ok with those or anything close to them.

Specs on the build:


TTS rods, cam and valve springs
LBZ pistons clearanced and machined by Burkett Racing Engines
Heads - stock valves; fully machined by Burkett Racing Engines
Kennedy Diesel 40% injectors
ATS dual fueler system
Industrial injection cp3's (both modified units)
Fuel cell; Holley Black and Aeromotive 1000 marine pusher pumps with larger supply lines
ARP head studs
GT 42R, 4" downpipe and custom 5" air inlet
ATS intercooler tubes
BD exhaust manifold
Custom nitrous system - 3 stage
Front coil-over suspension
Rancho 9000 shocks on rear


Stock: intercooler, head gaskets, rings, air horn, passenger side exhaust manifold, up-pipes, water pump, and drive belt accessories, rear suspension (except clamps on the front over-load), front end, rear end (no lockers...), drive shafts, axles, etc.

The rest has pretty much been covered. TTS tuning (I need to point out, Steve has not had the opportunity to dyno tune, track tune or otherwise fine tune this combo). An awesome 47RE Dura-Flite conversion from SunCoast. Approximately 5,800 pounds (truck has not been scaled since the tranny swap - but it the lightest it ever weighed before was 5895 pounds). Runs were made with conservative nitrous tuning (< .110 cummulative jetting).

 

[MAXLLY]

First off, thanks for a response guys! I know you're busy.

I don't think i will ever be in the 9's... My life insurance prolly wouldn't cover that, I certainly wouldn't wanna limp away from that one so disability isn't an issue!

My common sense bone tells me i want/should try and keep duration closer to a "norm", say 3000-3300. If i am trying to increase delivery would i not need to continue to increase duration?, in an effort to give the injector time to deliver the requested amount of fuel? And as volumn goes up would this not require even more time? This isn't about going faster really, it's about design of the system and tuning, I have seen pictures of melted pistons (don't wanna start another piston thingy) that appeared to be brought on by EGT and duration. The injector patter was outside the bowl at the edges.

The piston we/I have is designed to have the fuel delivered in the bowl, how can i do that if my duration is so long the piston is out of position. Simply increasing pressure? Is it that simple?

I may have opened myself to ridicule and exposed my ignorance, but I really wanna know.

 

[Turbotug]

The spray is outside the bowl in a stock tune as well.

IIRC, Pat had a set and pics around here somewhere.

 

[dieselson]

THis would be some good info, any equations to use to get the size of the injectors, for say 45 psi. I sort of doubt that injectors help very much if not sized right. At the SoCal Dyno 2007, Doug Lindsey, with a turbonetics turbo comparable to ours, dual cp3s, and injectors dyno'd 474 RWHP, and us, with stock injectors dyno'd 489.

 

[MAXLLY]

THis would be some good info, any equations to use to get the size of the injectors, for say 45 psi. I sort of doubt that injectors help very much if not sized right. At the SoCal Dyno 2007, Doug Lindsey, with a turbonetics turbo comparable to ours, dual cp3s, and injectors dyno'd 474 RWHP, and us, with stock injectors dyno'd 489.

Interesting! Under the assumption his injectors are larger i would assume then that his duration was less. more flow, less duration required to get the shot in. Is this what you understand?

 

[dieselson]

I understand, yes, I definetly, but it doesn't seem to work well, because his charger was slightly larger than ours, and he had aftermarket injectors. I think for injectors to work, you need the right tuning.

 

[02freighttrain]

This is a little OT and I don't know crap about much. That said, Larger injectors?

Hmmm. Ok, one thing is for sure. Most engines, gas or diesel's make more power with timing (in the form of BTDC).

Can we make big power with stock injectors? Yes. Pat has proved that. Do we see Piston failures with lot's of timing? Yes. Bent rod's too.

Now, from another approach. What if we bring fuel in a little later, in larger quantities? Could this minimize the possibility of pre-ignition and reduce Cyl pressure on the front side of TDC?

Why are we bringing fuel in so early in the cycle? Is this because that the motor likes timing or is it because we need Timing and PW to allow smaller injectors to supply enough fuel for the air provided by a big charger?

I'm running way under 30 degrees timing. I Don't think I could make the power I'm making with stock injectors without more timing. Does the reduced timing help with longivity? Who knows.

20 questions is over. Hope I can learn more about this and I know there are a lot of brains here to pick.

 

[Mike]

I think pressure is key to any injector. To little pressure with any injector and your gonna have unburnt fuel in the end. larger injectors do offer better performance but only if the stock injectors are maxed at any point in the power range. Having to open a stock injector early and keeping it open too long is where I feel the problem comes in. Total time the injector is on has shown to cause performance to fall.

As far as a calculation or formula, you'd need to tune and log, tune and log. More pressure means more volume, but remember commanded pressure doesn't mean you get that pressure. Match the pw with actual pressure and you'll gain more volume as actual pressure increases.

I feel larger injectors have an advantage. Keeping the pressure high enough to match a/f ratio is key. Larger injectors with the same charge means less pw for the same volume of fuel with regards to the same pressure.

Mike

 

[NastyNate]

Just sent my Injectors in. Went with 55% over, but they are still in UPS's hands if I need to make a change. The injectors will be mated with the HTT Twin setup from Nathan. Is there any updated info or intelligent advice out there, I still have a couple of days. Hopefully I went in the right direction.

 

[MAXLLY]

All i have at this point is the big kit takes 100 over injectors and the stock turbo w/ a big brother takes a 40 over.

 

[bullfrogjohnson]

Bumpity Bump

This was definatley good reading as I now have a headache