I am building a 406 with ~11 to one, all the mods in my sig, an lt1 manifold, and a 244 244 cam. What injectors size should I go with? Also, the accel 30 pounders are 249.99. Any larger and there is a big price jump. Suggestions? Thanks

 

Sorry I cant help with the injectors, but can you tell me how bigga shot your runin? Your combo is almost the same as mine, except I gotta 355. Those are the numbers I"m lookin to get outta this project. Any help would be appreciated.
Thanks! Barrett

 

18.4 lb injectors can support up to 295hp
19.01 lb injectors can support up to 304hp
21.4 lb injectors can support up to 342hp
22 lb injectors can support up to 352hp
26 lb injectors can support up to 416hp
30 lb injectors can support up to 480hp

lbs / 0.5 x 8 = hp
This is a formula for a 90% duty cycle which is
pushing the injectors to the limit, and the ECM too.

305 TPI injectors are rated at 18.4 lbs @ 34 psi
350 TPI injectors are rated at 21.4 lbs @ 44 psi.
Yellow Ford injectors are rated a 19.01 lbs @ 36 psi.

With an AFPR every 1 lb of pressure increase raises
the effective injector size by about 0.25 lbs per cylinder.

 

I have been trying to develop a formula for projected flow
through an engine to give estimated horse power and the
required injector size but that is proving to be quite difficult.

 

Wataru,

If you have a fresh 355 you should have no trouble running what I do. The only thing I don't like is your 3.73 gears. I think they are too much. I had them and went back to my 3.23. I am running a 150 shot. I hit it at the 60 foot mark.

I am aware of many injector equations. Most of them are approximations b/c bsfc is not usually known. I just want to know what most are running in the engine range I am closing in on.

 

Check e-bay. I just got a set of FMS #19 injectors with 30,000 miles on them for $28.00. (see my website for pix) I've seen several performance injectors including a set of ACCEL 24#ers for recently for $150.00. Good Luck!!

 

Hey Swapmaster...your formula is a great rule of thumb, but it certainly leaves a lot to be desired.

1. What fuel pressure are you running? Doc is running his injectors at 56 psi for more fuel flow. Of course, he is also burning his own proms. Your equation doesn't take that into account.

2. Your formula ASSUMES a BSFC of .50 which is a bit high for a high VE naturally aspirated engine. I use .45 in my equations with good heads. That is the real key here. I would use .45 with AFR 190 heads.

3. The duty cycle is a big deal to certain people. However, for a street driven car, how much of the time are you going to be at redline when it matters? It we are talking a race only car, then I can understand worrying about max duty cycle. It isn't like running at max duty cycle here and there is going to immediately burn out an injector. Some people never want to exceed 80% duty cycle under any circumstances...but the price for larger injectors and getting them to tune well under 3500 rpm is an issue as well. Don't go TOO big.

4. The ECM will not burn out by having a large duty cycle, occasionally, for the injectors. If you are running a 100% duty cycle for 80% of the time, then your injectors will show it long before the ECM does.

I would recommend 30 lb/hr injectors for up to 540 HP, for sure at 500 HP, you should be fine.


HTH,

Adam

 

That's exactly what it is, a great rule of thumb. And it should have
alot to be desired, this isn't an exact science. It will get you close
though. Myself, I am running yellow top Ford injectors rated at
19.01 lbs @ 34psi. I have them set at 52lbs on my 350. They have
a far better spray pattern than the GM injectors and at 52psi they
are flowing in the range of a 27lb injector. I have not stepped up
to custom proms yet, but need to. I am using the stock prom.

My wife always says bigger is better.

My car only comes out when the sun is high in the sky mostly
for one reason. To torture it. I actually likes the red line.

The Quad Driver in the ECM does not like to be taxed. I like the
idea of using a bigger injector or going a tad overboard on
pressure to keep the injector driver cooler. I have had one die
on me before, don't know what caused it but was with the stock
injectors with the stock fuel pressure regulator. I know that the
injectors were working alot of overtime when the driver failed.

As far as 540hp with 30 lb injectors, sure, just bump the pressure
a little. 600hp is probably not out of reach for a 30lb injector.

 

Exactly. I see that with your purpose, err on the safe side. However, with my 406, I don't worry about engine life one 1/4 mile at a time :>

To summarize, I think we both agree that 30 lb/hr should be just
fine for this application.

 

Cool, I think I will go 30s. 88, what size injectors did you have again??

 

I went with Accel 30 lb/hr injectors. That should be fine for what I will be doing.

 

where did you get them? price?
thanks

 

Cheapest place I found was Summit for $249. If anyone knows where they are cheaper, let me know. A friend of mine is going to buy some in the next few weeks and it would help him. I like Summit for most of my parts because of their good prices.

 

Cool, should work fine, just dial in your pressure watching
the Block Learn on a scanner and should run like a raped
ape.

 

Hey swap master.
I know of a guy in the city thats running an L98 383, mini ram,
zz-9 cam.
He's running with his stock 22 pound injectors and is getting like 440 Hp.

He's going to be putting on a pro charger or all ready has.
I think with the super charger he'll have to get a motec.
But the stock injectors can sure support alot of ponies.

 

That would not be a problem at 60 lbs of fuel pressure.