42 pound injectors too much?

[ShortThrow50]

I just sold my supercharger becuase i decided i want to order a 347 stroker. It will be N/a of course with 10:4:1 compression with my heads. Reason i ask is becuase i would hate to have to sell these things already and lose money. they only have about 50 miles on them and are 3 months old. Can i just turn down the fpr?

 

[Lightning&Mach1]

For your N/A setup I think they will be too much. I think a set 30# injectors would be better.

 

[buddha93]

I think you'll be fine with those 42's. Any sort of tuner on the car?

 

[ShortThrow50]

I think you'll be fine with those 42's. Any sort of tuner on the car?

well, im gonna pull my custom chip cause it was for the blowe setup and i dont plan on getting another custom tune for a n/a setup. N/a tunes are a big waste of money from my experience. Iguess ill have to find someone with like new injectors to trade for

 

[5liter]

A 42 will be way to much. Depending on your motor you may want some 24s. They are good to 400+ (personal experience).:beer:

 

[buddha93]

I'm also using the assumption your going to be making around 450 hp also. With a BSFC of .50 and max duty cyle at 80%, that puts you at a 35lb injector. I say keep em'.

 

[ShortThrow50]

I'm also using the assumption your going to be making around 450 hp also. With a BFSC of .50 and max duty cyle at 80%, that puts you at a 35lb injector. I say keep em'.

and just turn the fuel pressure down?

 

[buddha93]

Think of it this way. I run a set of 50lb injectors in my setup (actually a tad small). At idle and normal cruising it's not under boost and you wouldn't know it from stock aside from the blower whistling along. It's not rich and it passes a Missouri sniffer test all day long with the stock fuel pressure. If everything is correctly working, the ECC, MAF, and O2's will take care of the fuel delivery.

 

[red95gts]

Think of it this way. I run a set of 50lb injectors in my setup (actually a tad small). At idle and normal cruising it's not under boost and you wouldn't know it from stock aside from the blower whistling along. It's not rich and it passes a Missouri sniffer test all day long with the stock fuel pressure. If everything is correctly working, the ECC, MAF, and O2's will take care of the fuel delivery.

+1 42s will be fine. A tune for a stroker with aftermarket H/C/I would be a great use of money, not a waste.

If you build a 347 and it only needs 24s or 30s, you've built a turd.

 

[buddha93]

If you build a 347 and it only needs 24s or 30s, you've built a turd.

Now that's some funny stuff!

:lol:

 

[ShortThrow50]

I was thinking the same as you guys, its just that on some other sites people wouldnt agree. I just needed some more confidence from others.
also, what would be a great starting point as far as fuel psi.

 

[buddha93]

Stock fuel pressure is the best starting point. Remember too that the ECC has an adaptive learning curve and can tune some of what you do to the fuel pressure.

As far as what others think, it's just that. Everyone's combination is different, and NA you can fudge a little more on injector sizing. Myself, I just use the injector calculators that have been around forever and a day and a little knowledge and go with that.

 

[TFStang]

Injectors are cheap enough. Buy a set of 30's and keep the 42's just in case. I'm sure you could also trade with someone if you didn't want to spend the extra $125 for some 30's.

I say 42's are way too big for your set up. I would go 24's or 30's.

 

[5liter]

+1 42s will be fine. A tune for a stroker with aftermarket H/C/I would be a great use of money, not a waste.

If you build a 347 and it only needs 24s or 30s, you've built a turd.

My little turd 306 HCI with a 100 shot put down 431 at the wheels with 24 pound injectors. It ran consistant 11.70s on the motor and 11.20s on the jug in a full weight 89 GT.

My 90 GT made 498 RWHP (T-trim Vortech) with 38 pound injectors.

A well built 347 will do anywhere between 350-370 RWHP. A 24 pound injector will be fine.

 

[ShortThrow50]

My little turd 306 HCI with a 100 shot put down 431 at the wheels with 24 pound injectors. It ran consistant 11.70s on the motor and 11.20s on the jug in a full weight 89 GT.

My 90 GT made 498 RWHP (T-trim Vortech) with 38 pound injectors.

A well built 347 will do anywhere between 350-370 RWHP. A 24 pound injector will be fine.

I agree the 24's would be fine buddy. I'm just tryin to figure a way to keep these injectors without running pig rich. I know of a dude on stangnet that runs 30 pounders with just a 302 and H/C/I and its running pretty good and not rich. I was figuring that i might be able to get away somehow with these 42's. This 347 stroker should be putting down a little over 400 at the crank. The problem here is that i just spend 350 for the injectors and 40 for the sample tube. Im on a liited budget to be buyin new injectors and i dont feel comfortable buyin someones used. AHHH christ, at least i have a couple months before i have to make up my mind. Ill be ordering the block from fordstrokers.com and the owner told me that it wont be ready to ship for about 9 weeks. Hes a busy guy.

 

[red95gts]

My little turd 306 HCI with a 100 shot put down 431 at the wheels with 24 pound injectors. It ran consistant 11.70s on the motor and 11.20s on the jug in a full weight 89 GT.

Wet kit? If so, then the rwhp figure of 431 doesn't mean anything as the nitrous is supplying it's own fuel. What was the base fuel pressure? How about Air/Fuel Ratio?

I'll wager it's a wet kit and the car made around 320 rwhp on motor. I'll wager the fuel pressure was consdierably higher than it should be and that you were very, very close to 100% duty cycle with 24# injectors.

My 90 GT made 498 RWHP (T-trim Vortech) with 38 pound injectors.

Assuming 15% drivetrain loss, that's 585 fwhp. I'll be generous and assume 0.55 as a BSFC (I'd feel much safer with 0.65). Here's how it lays out:

@ 80% duty cycle / 43.5 psi : 50.56 lbs/hr
@ 80% duty cycle / 55.0 psi : 44.71 lbs/hr
@ 80% duty cycle / 75.0 psi : 38.29 lbs/hr

There's plenty of reasons not to run an injector at 75psi rail pressure, fire safety being #1. Aside from that, the injector is designed for a 43.5psi rail pressure and the flow/spray characteristics are designed with that as a constant.

A well built 347 will do anywhere between 350-370 RWHP. A 24 pound injector will be fine.

Again...350 rwhp is 411 fwhp. It would take around 75# rail pressure to keep duty cycle below 80%.

The bottom line here is: Yes, you can run a really small injector and make power with it if you are willing to roll the dice on safety and reliability. But, just because you did it, don't spew that advice without a disclaimer and maybe a little tech to go along with it.

BTW...350-370 rwhp is a well-built 347?? Try 400-425 rwhp - that's a well-built pump gas 347.

 

[ShortThrow50]

Ok so it looks like im back to using my 42 pounders again lol

 

[red95gts]

Explain this to me: How and under what circumstances would a 42# injector be "too" big? What would the symptom be?

 

[ShortThrow50]

Explain this to me: How and under what circumstances would a 42# injector be "too" big? What would the symptom be?

I cant really. I just did some brief reading that some people were telling others that it takes a blower to justify 42 pound injectors. I know my way around engines, just not the electronics and fuel injection. I really on advice. I also figured you could just fiddle with the regulator and give whatever fuel you wanted. Bottom line, I would like to keep the injectors and it seems as though the census says theywill be fine if not great

 

[red95gts]

An injector that is too small for an engine only becomes apparant at one point: As you reach the maximum required fuel delivery. For the most part, that is max rpm/max load. 6000rpm at the big end of the track....

An injector that is too large for an engine only becomes apparent and one point: As you reach the minimum required fuel delivery. This is at/near idle.

The injector is considered too big when the minimum pulse width from the EEC is till too much fuel for the motor. The injector simply flows too much fuel for the EEC to control. There's a bunch of math that could be posted, but like buddha93 mentioned above, his car runs fine with 50#ers.

My turbo car is a 302ci, TFS TW heads, stock camshaft motor. It obviously makes no boost at idle or light loads. For all practical purposes, it may as well be a naturally aspirated motor as long as I keep my foot out of it. I run 43psi fuel pressure and a 50# injector. It idles around 14.3:1 no problem. If I play with the pulse width, I can make it idle as lean at 18:1, but I don't for plenty of reasons.

Bottom line - you have brand new 42#ers - run 'em! Good Luck!