Discrepancy over fuel injector size

[cboney2003]

I contacted a fuel injector cleaning/flow matching company and they list 19# injectors as stock for my 97 3.8L Firebird, I was under the impression that 22#'s was stock... Maybe thats why I have a lean condition since Im using 19's. Really need to know if somebody could help! The Tech Database says 22's, everyone I talk to at injector places say 19's, but they list 22's for the 96-02 Grand Prix 3.8's??

[ October 26, 2005, 01:59 PM: Message edited by: cboney2003 ]

[FirebirdGT]

19# is stock.

[98Camaro3.8]

I've always heard they were 22.

http://www.camarov6.com/ubb/ultimate...=003251#000013


My PCM says they are 22 lbs per hour. 356.41 milliseconds per gram, actually, which equated to 22.26806 lbs per hour. That's the stock table from my car.

[FirebirdGT]

Originally posted by 98Camaro3.8:
I've always heard they were 22.

http://www.camarov6.com/ubb/ultimate...=003251#000013


My PCM says they are 22 lbs per hour. 356.41 milliseconds per gram, actually, which equated to 22.26806 lbs per hour. That's the stock table from my car.

Yes, but you have a DHP tune.

Stock is 19#

http://go.mrgasket.com/pdf/dfi.pdf

[98Camaro3.8]

Originally posted by FirebirdGT:
Yes, but you have a DHP tune.

No, I don't have a DHP tune. I have a DHP tuner, but like I said that was from the stock tune. Just like other people who saw their stock tables in HP Tuners.

I'm afraid that without any hard proof otherwise, I'm going to have to believe what GM programmed in my PCM versus what Accel thinks.

[cboney2003]

Well, here's the deal. My car was running lean and had many misfire codes with the 19# injectors. I have headers, offroad 3" catback, 3" intake and a bored out engine with slightly higher compression. I just installed 22# injectors and voila, throttle response is awesome, more power, no lean codes, no misfires. So, all I know is, I like the 22's better regardless of whatever is stock. I chose the 22's b/c of the lean condition and I used a formula MSD puts out for sizing injectors based on engine horsepower and number of cylinders, it can be found at:

http://www.msdignition.com/fuel_1.htm

BSFC= 0.5 for naturally aspirated
0.6 for forced induction

ENGINE HP x BSFC
-------------------------
NUMBER OF INJECTORS x 0.8

so

200 x 0.5
--------- =
6 x 0.8

100
--- =
4.8

20.8333# injectors

That's for the STOCK 200 horsepower rating, so 22 seems more likely to be correct than 19. And I know now that the 22's work well.

[ October 29, 2005, 11:10 AM: Message edited by: cboney2003 ]

[Matt G]

How much did you pay to replace the injectors?

[cboney2003]

Actually nothing, I bought the set of matched and flow tested 19 pounders from Linder Technical Services. I called them after I discovered it was running so lean and that I needed the 22's, and after lots of arguing he finally sent me a set of flow matched 22's for free as a warranty claim. It would have cost $150 I believe for the whole set otherwise.

[4thgenowner]

50# :D

[FirebirdGT]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by FirebirdGT:
Yes, but you have a DHP tune.

No, I don't have a DHP tune. I have a DHP tuner, but like I said that was from the stock tune. Just like other people who saw their stock tables in HP Tuners.

I'm afraid that without any hard proof otherwise, I'm going to have to believe what GM programmed in my PCM versus what Accel thinks. </font>[/QUOTE]OK, let's try this. The "rating" is based on a standard fuel pressure of 43.5psi. With a BSFC of .45 and Duty Cycle of .80 gives 18.86 lb/hr.

Read this:

http://www.rceng.com/technical.htm

[cboney2003]

You're using a lower BSFC, 0.5 is standard, if you plug in 0.5 for the BSFC it comes out to 20.95 # instead of 18. Either way I'm just telling you all how well it has worked for me putting in the 22's, completely fixed my lean condition and I have only a few bolt ons so take that as you will.

[98Camaro3.8]

Originally posted by FirebirdGT:
OK, let's try this. The "rating" is based on a standard fuel pressure of 43.5psi. With a BSFC of .45 and Duty Cycle of .80 gives 18.86 lb/hr.

That tells me that 19 lb/hr injectors would max out at 200 hp, with no room for extra power. It's much more likely that you'll really max them out somewhere around 220-230 hp, which would give you 22 lb/hr injectors.


Understand that I'm not just trying to argue with you here. Just trying to really find out what the truth is.

[AZ3.8Camaro]

It is also more likely that the stock injectors are designed to work at a lower duty cycle than you would consider for aftermarket stuff. Just for reliability, and a safety factor.

Running only .45 BSFC, with a 70% duty cycle, you need almost 22lbs.
With the .45 and the 70% D.C. you DO get 19lbs.
Running a .50 bsfc, with an 80% duty cycle, you also need almost 22lbs.

What duty cycle are you guys seeing stock with the scanners?

[shenanigans]

hey guys jsut something to browse...
http://www.camarov6.com/ubb/ultimate...;f=35;t=000167


I am maxing mine out, with pretty stock tune with bumped timing...

I later, loaded 100% factory tune except for speedo recal, I am still seing like 96% duty cycle.

only "engine" mods are shaved lid, paper filter, pvc smooth bellow, and a cutout on factory catback.


I went back and checked T-punks car (2001 a4 fbird convert) He has a v8 takeoff catback, smooth bellow and a I think still factory lid. He was seeing 86-89% duty cycle on his injectors?

[98Camaro3.8]

What is the actual IPW and RPM where you're most maxing them out?

I find it strange that GM would allow a stock car to run at a 96% duty cycle. Something must be weird, unless you're just running ridiculously rich.