Fuel Injector Upgrades

[AleroB888]

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
http://i493.photobucket.com/albums/rr299/Gflash01/IMG_0390.jpg?t=1227851798

http://i493.photobucket.com/albums/rr299/Gflash01/IMG_0396.jpg?t=1227851931

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.

[Spilner521]

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?

[AleroB888]

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.

[AleroB888]

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

http://i493.photobucket.com/albums/rr299/Gflash01/IMG_0421.jpg?t=1227852027

http://i493.photobucket.com/albums/rr299/Gflash01/IMG_0424.jpg?t=1227852192

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.

[jackal2000]

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. :)

[Cliff8928]

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

[Beholder88]

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?

[jabartram]

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

[jackal2000]

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.

[undecided02]

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.

[jackal2000]

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.

[AleroB888]

................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...........

...........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..............

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.:)

[AleroB888]

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.

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. :)

[jackal2000]

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.

[AleroB888]

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.

[oldskid33]

i thought stock was 30/per hour :-/

[jackal2000]

i thought stock was 30/per hour :-/

you thought wrong.

[oldskid33]

wow ftL!! :( lol

[MacsAre1]

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?

[-Alero-]

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?

[AleroB888]

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?

My '99 fuel pressure regulator runs about 10 psi lower than in my '03, which would lower the flow rate, but I don't know at which pressure each was rated for. You might find out at what pressure yours were tested.

[AleroB888]

........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 had this problem with the 36 and 35 lb. injectors, but not the 28's. After a test drive earlier today, it appears the problem is solved.

I demodded the car except for CAI, exhaust system, and ignition. I installed the 36 lb injectors again, reset the injector flow rate (IFR) close enough for a run and scan, let it warm up, and drove about 8 miles. This time the idle was normal, no misfires, no hesitation, good throttle response. Unfortunately, since the tranny is shot, I could only test WOT in first gear. :)

Looks like the problem was that the (stock-type) throttle body that I modified is not exactly like the stock one in the idle air control (IAC) opening, and needs a section cut out of the mounting flange to work correctly. :blush: :banghead:

If no other problems crop up, I'll retry the RC Engineering 35's.

[AleroB888]

The GM 36 lb injectors had been in the car for about 2 months now with fair to good drivability, so I installed the 35 lb RC injectors:

http://i493.photobucket.com/albums/rr299/Gflash01/Album%20-%202/005.jpg?t=1309837630

I must mention here that there has been a problem with misfires on cylinder #1 since the last time I raced back in November, pretty severe when the engine is cold, and confined to low rpm. So far, it disappears at WOT. But there is definitely a mechanical problem with cylinder 1.

Base fuel pressure used is about 44, with a 2001 year model PCM program file. I had the IFR set to 33 for the GMs, and installed the RCs without resetting it. Between that and uneven flow at start up, the first run at idle was pretty shaky, fuel trims went way too far negative. After resetting the IFR twice, I wound up leaving it at 35 lb/hr, the manufacturer's rating. With ambient temps in the low 80s today, Long Term Fuel Trims (LTFT) scanned between (+5) and (-5), close to zero average.

So this means that the RC 35's have a higher flow than the GM 36's for the same psi. The Injector Duty Cycle is 8-10 percent less than the GMs at WOT.

There appears to be more random misfires with the RC 35 compared to GM 36 lb, until the engine warms up. The 28 lb Envoy/ 'Blazer injectors did much better in that respect. After only one day of use, my impression is these RC injectors will be usable as far as drivablity, but time will tell. I would really like to have them in for the next trip to the track, as they are closely flow matched, and it would be interesting to see how the single-hole design does under boost. :)

[MMGT1]

I've had great results using the 36lb ones. My idle is within 1% and can hit commanded AFR at WOT dead on all the way to 6600 RPM on a bone-stock pump. If youre still boostin' though, I would go to 40lbs to keep the duty cycle down. Just a thought man

[AleroB888]

I've had great results using the 36lb ones. My idle is within 1% and can hit commanded AFR at WOT dead on all the way to 6600 RPM on a bone-stock pump. If youre still boostin' though, I would go to 40lbs to keep the duty cycle down. Just a thought man

I think the RC 35s will do good enough as far as duty cycle, I'm only up to 80 % @ WOT with 85 degree ambient temp. That compares to about 90 % with the GM 36s. I expect those percentages to go up to 85 and 95 % respectively when the weather cools back down, bypass the air filter, etc.... I think the GMs would do just fine, but I won't have too many chances at the track, so I'll try the RCs first. As it is, I'll wait for cooler days, and try to take one last shot at running a 12 second pass.

[MMGT1]

Off topic a bit here B, but have you ever replaced your crank sensor and lead that goes from the IGM down to it?

[AleroB888]

Off topic a bit here B, but have you ever replaced your crank sensor and lead that goes from the IGM down to it?

No, it's the original sensor and lead. If about the misfires on #1, I did swap out the coils, plugs and plug wires.

[MMGT1]

They are notoriously foul bud. I was having some issues that would not show up in any scan and finally said f-it and replaced them. When I pulled the crank sensor I could physically see that the sensor was slightly "swollen" inside the block. At the dealership we replace a lot of them on the 3400's as the exposure to heat in there really messes them up bad. Even if your not throwing codes, with the stress I know your car has endured, for a 25 dollar part I would replace that one when you can man. Other than the dam MAF it is the sensor that will cause all kinds of crap before they get bad enough to throw a code.

[AleroB888]

They are notoriously foul bud. I was having some issues that would not show up in any scan and finally said f-it and replaced them. When I pulled the crank sensor I could physically see that the sensor was slightly "swollen" inside the block. At the dealership we replace a lot of them on the 3400's as the exposure to heat in there really messes them up bad. Even if your not throwing codes, with the stress I know your car has endured, for a 25 dollar part I would replace that one when you can man. Other than the dam MAF it is the sensor that will cause all kinds of crap before they get bad enough to throw a code.

Thanks, I'll do that. Any other advice on how to replace it is appreciated, which brand, etc.

[MMGT1]

Kinda tricky to get out but not too bad. Use brake clean and spray the crap out of the area where it mounts to the block. then spray it with lube before you pry it out. Do your best to lift it straight out as this one can break! Get one from GM bud. Like I said it's about 25-30 bucks for one State side I believe. Use electric grease on the seal of the new one before you install it.
The connector between the module and the sensor is a little costly up here, around 100 bucks, but I would replace that at the same time. It runs really close to the coolant lines back there and causes a lot of damage to the sheeting around the wires. They will actually fuse together from the heat. Pretty straight forward to do. Because of the headers I had to go through the wheel well to get access to it. Made a huge difference to my idle trims and how the car ran after being on the highway for any length of time.

[AleroB888]

The GM 36 lb injectors had been in the car for about 2 months now with fair to good drivability, so I installed the 35 lb RC injectors:

................I must mention here that there has been a problem with misfires on cylinder #1 since the last time I raced back in November, pretty severe when the engine is cold, and confined to low rpm. So far, it disappears at WOT. But there is definitely a mechanical problem with cylinder 1.

Base fuel pressure used is about 44, with a 2001 year model PCM program file. I had the IFR set to 33 for the GMs, and installed the RCs without resetting it. Between that and uneven flow at start up, the first run at idle was pretty shaky, fuel trims went way too far negative. After resetting the IFR twice, I wound up leaving it at 35 lb/hr, the manufacturer's rating. With ambient temps in the low 80s today, Long Term Fuel Trims (LTFT) scanned between (+5) and (-5), close to zero average.

So this means that the RC 35's have a higher flow than the GM 36's for the same psi. The Injector Duty Cycle is 8-10 percent less than the GMs at WOT.

There appears to be more random misfires with the RC 35 compared to GM 36 lb, until the engine warms up. The 28 lb Envoy/ 'Blazer injectors did much better in that respect. After only one day of use, my impression is these RC injectors will be usable as far as drivablity, but time will tell. I would really like to have them in for the next trip to the track, as they are closely flow matched, and it would be interesting to see how the single-hole design does under boost. :)

After a few days of testing, I found the drivability of the RC Engineering injectors not acceptable, so the GM 36s were reinstalled. Nothing other than Injector Flow Rate (IFR) was recalibrated for these tests, and it's still possible that the RCs can be made to work. But since the GMs are less problematic, I'll keep them in for now.

I settled on an IFR of 31 and did some scans yesterday, with (much lower than normal) ambient temperature in the 60s. Just a few days before, the temps hit 100 degrees. Setup was in street trim, 1/4 tank of gas. On the first scan, the Injector Duty Cycle (IDC) hit a maximum of 94%, with decent Long Term Fuel Trims, (+2,-7 %) and no Knock Retard (KR). That was much better than I'd seen in the last few months, and don't expect it to be typical, but seems to be moving in the right direction. :)

http://i493.photobucket.com/albums/rr299/Gflash01/Scan9-7-11.jpg?t=1315376455

IAT (intake manifold) at start of run = 75 degrees, end of run = 93 degrees. Boost peaked at 11 psi