Fuel Injector Upgrades
 

I thought it would be helpful to post some data on fuel injector mods, since my last two purchases did not go well. I'll get started with an outline and edit in more details/updates when time allows.

1) OEM # 25313185
Blazer, Envoy, Bravada / 28 lb/hr
2) Stock 1999 Alero V6 / 19 lb/hr
3) RC Engineering SL2-370 / 35 lb/hr
4) Lucas 42.5 / lb/hr




Notes (results may not be typical / running at high altitude / stock fuel pump) :

1) Envoy Injectors (4-hole nozzle)
I have had great results with these -- excellent drivability. When I first got them they worked well enough without reprogramming the computer -- initially threw a "rich" code, but adjusted itself out. I am the 3rd owner of them. Even though often run up to 108% duty cycle, seem to perform better than their flow rating.

2) Stock 1999 (6-hole nozzle)

3) RC Engineering SL2-370
These came with a flow rating for each injector, as if they had been individually tested before shipment. According to the data sent with them, they were matched within + or minus 1 cc (!) Three flowed at 370, two at 369, and one at 371 cc, said the chart. They didn't indicate which was which, but if they were that close, it wouldn't matter. The first time I ran them in the car, I thought "Wow, they're great ! " Midrange up to WOT was smooth, powerful, had a precision feel. But soon, as the car warmed up and the computer settled in, an off-idle stumble developed. Not just from a standing start, but also a hesitation when stabbing the throttle from a low rpm cruise. This was accompanied by a little black smoke out of the tailpipe each time, and random misfires but no codes thrown. Eventually the computer's compensating made matters even worse. I tried every possible tuning combination to get a usable result, but none worked.
I'm guessing the single-hole spray nozzle was just not atomizing well enough at the low Injector Pulse Width required.

4) Lucas 42.5's
I got these from ZZP over a year ago, not flow matched. I ran them through the Winter and into the Spring. In colder weather during startups, I got misfire codes thrown, but no SES light. After warmup, no codes appeared. In spite of that, the car idled OK and did not hesitate or stumble. Performance seemed to be generally good. But then, one day at the track, the # 5 Injector stuck open. Performance at the track that day had been subpar, but until it failed completely it was not obvious exactly why. The car had to be towed home.
When I called ZZP and asked to get one replacement, the guy said they can only be purchased in a full set.

You mentioned with the Envoy injectors that you didn't have to reprogram for them to work decent. Were the RC's and Lucas' just swap and go or did you reprogram for them and these are the results?

Yes, for the RC's and Lucas I did reprogram the computer. I would have kept the Lucas ones in if not for the failure noted. Apparently some people have run the Lucas with no problems.

I am in the process of doing a fuel pump/system upgrade, and it is possible that raising the fuel rail pressure a bit could improve the RC's atomization at idle.

I also have obtained some 36 lb injectors off a SC'd 96 Buick and will hopefully try them out soon.

I got a Walbro 255 LPH fuel pump installed a couple of days ago, gave it a day for the computer to settle things in, and did a scan. It seemed to make the Envoy injectors work even better, and I should have left them in to see if the pump change would gain anything at the track.

However, I was anxious to try out some other injectors I found in a salvage yard, so I changed them out the next day.

5) OEM # 0280155737
1996 Buick Riv SC, M90, GTP, etc. / 36 lb/hr
6) OEM # 0280150934
1992 Buick SC, M62, etc. / 28 lb/hr





5) 1996 Buick Riv M90 (4-hole nozzle)
I have only had these in a day and a half, and it's been raining most of that time, so the testing is far from done. No problems with drivability have shown up yet, but it's too soon to judge the WOT performance. There are way more random misfires showing up on the scans than with the Envoy injectors, not that you actually feel it when driving. No codes thrown. (note: I reset IFR in the PCM)
With the Walbro and these in now, we are running much richer at WOT....time to check the plugs :)
6) 1992 Buick M62 (4-hole nozzle)
I'm just including these as a curiosity, I picked them up not knowing what their flow rate was. The only info I found was in some forums stating they were 28 lb/hr. They would fit, though, if you wanted to use them, and there are some aftermarket units in the same configuration.

i just bought a set of 1) OEM # 25313185 off ebay for $100. should have them installed by the end of next week hopefully with good results. :)

With any kind of luck they will be better results than you got with those dirty junkyard injectors you got before. ;)

Pontiac
 

I have 6 injectors from a '96 Bonneville that had a 3.8 in it. Do you think these would work in my 3.4 Alero? Would I have to reprogram? I don't have any mods that would require them - yet, but in the event I get something that would warrant an injector upgrade, it would be nice to be able to use something I already have. I'm thinking about getting a cam sometime next year. I've also still got my injectors from my 3.1 Malibu, in case anyone wants them. I can get the OEM numbers when I get home. I think they are the same as what's on my Alero?

I have been under the impression that the stock injectors were 22.5s?

i believe for year 2000+ they are, but for 1999 models they are 19.

how is your mpg after installing thiese injectors. Im not against burning more fuel to make more power but I am curious about the cost before I play around too much.

unless you are heavily modified you dont need to upgrade.

Update
 

The jury is still out on the 35 and 36 lb injectors, the hesitation issue now seems to have been from another source, related to the supercharger. I have not had a chance to retest them, and now the 28 lb units are back in. Also, the 1999 runs about 10 psi less fuel pressure than the later models, and the stock pump is rated lower as well. I went to a later model FPR.

My first Walbro pump failed, as did an Autozone OEM unit. I tested an inline Walbro as a booster pump in a setup with the Autozone OEM, but no success on that yet either. Right now I have a second Walbro in-the-tank unit installed with wiring directly to the pump. I just made a 1200 mile road trip to sea level, never letting the tank go below 3/4 full. This should be interesting, to say the least.:)

I just got about 30 mpg on 1200 mostly highway miles, no passengers, maybe 250 lb. of cargo. Of course, it was running slightly downhill. :)

had my 28lb injectors installed yesterday. picked up the car today and scanned, LTFT's showed up as -21 at idle. i corrected the IFR table and LTFT went to 7 at idle. i opened the throttle a bit and the trim went to -2 or so. more fine tuning to come, but so far so good.

For those, my IFR is set at 26 lb/hr with HP Tuners. The LTFTs run from -10 to -3 on average, but can vary a lot depending on daily temperatures, altitude, etc.

I do change it from time to time to tweak the LTFTs, or if I change the base fuel pressure.

i thought stock was 30/per hour :-/

you thought wrong.

wow ftL!! :( lol

stock flow rate
 

I just had my stock injectors tested and cleaned on a flow bench. The flow rates went from 21-22.1 lb/hr before cleaning to 21.6-22.5 lb/hr after cleaning. How come that's higher than the 19 lb/hr you mentioned?

99's had 19 lbs and after that they came with 22's so my guess is either they were changed once before during some sort of maintenance, or your car was released late 99 and had 2000+ style stuffies, take a look right next to your fuel pressure regulator and there are 2 digits on your lower intake manifold, does it say 00? 99?