Hi
I need to change out the injectors on my 94 Deville (4.9L SPI). Can anyone tell me the correct flow rate. I keep seeing that people have swapped in 19 lb/hr injectors. My calculations give for a 15 lb/hr injector. Also, does anyone have any idea where I can get these at rock bottom prices. I need all eight (according to my mechanic) and I do not want to pay anywhere near the $800.00 price tag I get at my local autozone. All help and advice will be appreciated

Ouch, $800? Take a look at these: Accel Performance Fuel Injectors (http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4114&prmenbr=361) 8 for $230.

Ouch, $800? Take a look at these: Accel Performance Fuel Injectors (http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4114&prmenbr=361) 8 for $230.
Thanks Dave

So I take it that the 19lb/hr injector is correct for this application. No need to do anything with the chip, this is just bolt-on and go?

Yup, the 15 lb-hr injectors are listed for the 305, and your engine is a 300. The computer will compensate for whichever injector you put on there, by reducing how long the injector stays open.

I've got those accels on my 92, and they're great!
D.

The computer will compensate for whichever injector you put on there, by reducing how long the injector stays open.

This is not really true. The fuel injection pulse width calculation in the PCM uses an "injector constant" that is basically the flow rate of the injector to determine how long to hold it open. The PCM has no way of knowing of an alternate injector was installed with a different flow rate....so...how would it "know" to compensate...???

The closed loop fuel control can compensate to a degree , but, there is not sufficient authority to change the fueling that much to account for a dramatic injector flow rate change...and...the closed loop system does not function at full throttle so the fueling would be off there if the wrong flow rate injector is installed.

The PCM is calibrated for a specific flow rate injector. That is what should be used for that application. Without reprogramming the PCM calibration it cannot, on it's own, compensate for an different flow rate injector.

Yup, the 15 lb-hr injectors are listed for the 305, and your engine is a 300. The computer will compensate for whichever injector you put on there, by reducing how long the injector stays open.
Did you mean the 19lb/hr, or were you correcting me so that I should buy the (find) 15 lb/hr.
Thanks again

Yup, the 15 lb-hr injectors are listed for the 305, and your engine is a 300. The computer will compensate for whichever injector you put on there, by reducing how long the injector stays open.

I see now that the 5.0l uses the 19 lb. Thanks for all your help. Anything special I should know before completing the job. Any special precautions. Will I have to remove the power steering pump to complete the job? Sorry for all the sophomoric questions, but this is my first time doing injectors.

Yes, the power steering pump and egr valve both need to come off. The PS pump doesn't need to move to far, so don't disconnect the lines, just the pump itself. The egr valve is a bitch without crowsfeet wrenches. Other than that there are about 6 bolts holding the rails and pressure regulator down, and both rails and the middle "rail" with the pressure regulator come out as one unit. If you run into any problems, let me know. Oh yeah, all the throttle and cruise cables need to be disconnected to.
D.

This is not really true. The fuel injection pulse width calculation in the PCM uses an "injector constant" that is basically the flow rate of the injector to determine how long to hold it open. The PCM has no way of knowing of an alternate injector was installed with a different flow rate....so...how would it "know" to compensate...???

The closed loop fuel control can compensate to a degree , but, there is not sufficient authority to change the fueling that much to account for a dramatic injector flow rate change...and...the closed loop system does not function at full throttle so the fueling would be off there if the wrong flow rate injector is installed.

The PCM is calibrated for a specific flow rate injector. That is what should be used for that application. Without reprogramming the PCM calibration it cannot, on it's own, compensate for an different flow rate injector.

Bbobynsi,

I'm not at all interested in going down this path, but I'm curious what the potential downside to doing this (going to higher flow-rate injectors) is, aside from perhaps wasting money and gas? I assume the engine would run rich, which I guess is better than running lean. Would a rich-running engine adversely affect the converter? Are there other issues? Would it be a worthwhile exercise if you were using nitrous to avoid the possibility of a lean situation?

Just curious.

Bbobynsi,

I'm not at all interested in going down this path, but I'm curious what the potential downside to doing this (going to higher flow-rate injectors) is, aside from perhaps wasting money and gas? I assume the engine would run rich, which I guess is better than running lean. Would a rich-running engine adversely affect the converter? Are there other issues? Would it be a worthwhile exercise if you were using nitrous to avoid the possibility of a lean situation?

Just curious.I wondering to. If the mixture were rich, wouldn't the PCM adjust the fuel mixture based upon o2 sensor output?

I wondering to. If the mixture were rich, wouldn't the PCM adjust the fuel mixture based upon o2 sensor output?

I believe (and this is speculation) that the PCM will only adjust the mixture so much in response to the 02 sensor and that this modification would affect the mixture enough that the PCM couldn't compensate within its parameters.

If the mixture were to richen radically on a stock engine, then presumably you would not want the PCM to compensate, but rather set a code so whatever was causing the richness could be fixed.

I've been running the 19's for about a month now, and I've had NO problems. Car felt much more responsive afterwords, and my gas mileage is more or less the same. The way I see it, the computer adjusts for them during normal driving, and you only get the extra fuel when you need it--- at WOT when the cpu doesn't take readings. I'm happier than a pig in s==t, and I think you just can't beat those accel's.
D.

The computer closed loop fuel control system has a limited "adjustment" range that would likely be exceeded by the change from 15 to 19 lb injectors. That would make the engine run rich across the entire operating range. It would probably drive OK that way...but the emission system will not function as the cat conv cannot operate correctly with the rich mixture. If passing a sniffer or emission chekc is not applicable then this might be a moot point to many people.


The speed density sytem cannot adjust for the change in injectors other than thru the closed loop system. In some cases where the vehicle had a 4.5 engine and the owner swapped in 4.9 parts the swap to 19 lb. injectors was used to offset the inherent leaness imparted by the increase in displacement.

Bottom line, the engine will run "OK" with larger injectors and if engine mods have been made requiring more fuel (less backpressure on the exhaust, open intake, ported heads, etc...) then the effect of the larger injectors will be partially mitigated by the increased airflow..neither of which the PCM can correct for without a recalibration. Just like a carbed engine can run very well even though it is very rich so can a fuel injection system engine. Just that the emission system will not function with the rich mixture. Eventually, the cat can be damaged or destroyed due to the excess fuel.

Higher flow injectors can be used to offset NOS flow, yes...just that the injector will cause the engine to be rich all the time the NOS is not shot.

Wait, were talking about a 4.9 here. didn't they COME with 18 lb-hr injectors?

Yeah that's what I thought too, 1lb/hr increase is definatly not THAT much. People make a bigger deal about the computer than they need to. But that's just my opinion :canttalk:
D.