42lb injectors/issues

[02Z0h6]

It's me again. I just threw in some Bosch 42's and the only table I changed was the flow rate vs. kpa table (48.48824, 48.79827, 49.10830, 49.41832, 49.66635, 49.97637, 50.28640, 50.59643, 50.84445, 51.15448, 51.46450, 51.71253, 52.02255, 52.27057, 52.58060, 52.82862, 53.13865) I'm pretty sure this is the only one I need to mess with, correct? When I initially started the car it ran kind of rough and my ltft's were +25, stft's were escalating towards +10to 17 also. I figured I'd reset my trims and see what happens. The car ran worse. I just took it for a spin today and it is running terrible, seems like it's missing (got a 300 code and a flashing check engine light) and is struggling to find idle. I'm not sure if it's going to take time for the car to relearn or what? What are your ltft and stft at idle with a cammed LS1?
Thanks guys.

[Russ K]

This is what your IFR table should be. This setting will reduce your LTFT by ~16%

Russ Kemp

[[email protected]]

You will also need to adjust the batt. compensation table when changing injectors

[Russ K]

You will also need to adjust the batt. compensation table when changing injectors

I leave that table stock when changing injector sizes. What changes would you make on this table for 42 lb injectors?

Russ Kemp

[muncie21]

I leave that table stock when changing injector sizes. What changes would you make on this table for 42 lb injectors?

Russ Kemp

The reaction time for different injectors (either size or type) is different.

For example SVO 42#'ers are slower to react the Lucas/Delphi 42# injectors.

[02Z0h6]

This is what your IFR table should be. This setting will reduce your LTFT by ~16%

Russ Kemp

Thanks Russ. I was under the impression that because of our fuel pressure these injectors would flow a little higher. I guess RedHard's spreadsheet doesn't always work then? Russ have you run into this issue before?
Thanks again guys.

[Russ K]

Thanks Russ. I was under the impression that because of our fuel pressure these injectors would flow a little higher. I guess RedHard's spreadsheet doesn't always work then? Russ have you run into this issue before?
Thanks again guys.

Using 43.5 psi as the rating for the replacement injectors has always caused positive fuel trims and a leaner afr. I really believe that the stock injectors are also rated at 3 bar (43.5 psi) This seems to be a standard test presssure.

The 1985 TPI cars fuel pressure is 34-39 psi, then in 86-90, the fuel pressue was increased to 40.5-47 psi, the 1990 ZR1 is 48-55 psi. The LT1 cars were 41-47 psi. Now the LS1/LS6 cars are 55-60 psi. These specs are key on engine off, or at 0 kpa vacuum in the IFR table for our cars.

Russ Kemp

[02Z0h6]

Using 43.5 psi as the rating for the replacement injectors has always caused positive fuel trims and a leaner afr. I really believe that the stock injectors are also rated at 3 bar (43.5 psi) This seems to be a standard test presssure.

The 1985 TPI cars fuel pressure is 34-39 psi, then in 86-90, the fuel pressue was increased to 40.5-47 psi, the 1990 ZR1 is 48-55 psi. The LT1 cars were 41-47 psi. Now the LS1/LS6 cars are 55-60 psi. These specs are key on engine off, or at 0 kpa vacuum in the IFR table for our cars.

Russ Kemp

Thanks Russ. I'll give it a shot and post back.

[5_Liter_Eater]

OK, I have seen Russ' recent posts regarding IFR for 42# injectors including on my thread. I can't say I agree, I say use the spreadsheet, but I never thought about what pressure the stock injectors are rated at so I did some digging.

The early ('99-'00) LS1 injectors (P/N 0280155890) I have always heard were26.4 or 26.6 #/hr and assumed this was at 58 PSI (4 bar) because that is where my stock IFR started (26.4 PSI at atmospheric) but the below site has them listed as 22.3-22.4 #/hr at 3 bar and 29#/hr at 4 bar. At 3.5 bar they are 26.4#/hr which jives with what they are commonly referred to but who the heck measures flow rates at 3.5 bar?
http://www.z-r-c.com/Content/pid=2.html
There is an error there because they list 40 PSI = 3 bar when it should be 43.5 = 3 bar.

Even FiveOMotorsports lists them as 22#.

The '01-'04 injectors commonly referred to as 28.8# injectors are only 25.5# @ 3 bar. http://www.fiveomotorsport.com/Injec...sTPI.asp#lssix

So my '99's stock flash has an IFR that starts at 26.4#. This makes no sense since that is what the injectors are supposed to flow @ 3.5 bar (50 psi) and we all know that the LSx's run at 58 PSI (4 bar). So should we be using 3.5 bar (50.8 PSI) for our IFR tables?

They don't have the specs on the Bosch 558 green tops on the Z-R-C site but I believe they are measured at 3 bar (43.5 PSI).

Bottom line is that is the IFR table doesn't appear to be "correct" from the factory, at least for my '99 vette. This may explain why 02Z's fuel trims were way out of whack when he put in the numbers he got from the spreadsheet because the stock table was not "correct" to begin with.

So what to do? You could try putting in the #'s for the green tops at 3.5 bar and see what happens. You could also use the 3 bar numbers for the green tops like Russ. You could use the "correct" numbers assuming the green tops are rated at 3 bar and you know you will be running them at 4 bar and adjust your VE and MAF to compensate. You could get the injectors flow tested and use those numbers which you know to be corerct and adjust the VE and MAF for any discrepancies.

Really, and keep an open mind here, it doesn't matter. We are making changes to the system and there are really two variables you can change, the amount of fuel the PCM thinks it is injecting or the amount of air the PCM thinks it is injesting. Some argue that the injectors are a known; you can calculate the flow knowing the flow rate, the pressure the flow rate was generated at and the pressure you will be running them at. So use that and alter the airflow numbers. This is my vote. Some argue that if your fuel trims are in line stock and you do nothing but change injectors and your fuel trims skew then your IFR must be wrong, which is a good argument. In the end whatever you do to get correct fueling across the board is a good thing.

And this doesn't even talk about offsets...

[EC_Tune]

Bill,

I think I found another site that has flow tested the green tops *at* 3 bar. It's an injector service place: http://www.witchhunter.com/
They have the 0280150558 injector flowing 424 cc = 40.38 lbs/hr

And... Here's a Bosch PDF I found somewhere (I think it was LS1 Tech) that has them listed as 326.8 @ 2.7 bar working pressure. Wierd!

[redhardsupra]

how about this:
http://redhardsupra.blogspot.com/200...vo-42s-is.html

[02Z0h6]

how about this:
http://redhardsupra.blogspot.com/200...vo-42s-is.html

These are deatshwerk Bosch 42's redhard. I'm going to try Russ' flowrate table and then run some water around the intake to see if I have developed a vaccuum leak.

[Russ K]

The real question then is if you install the 42 lb/hr injectors and use 43.5 psi as the injector rated fuel pressure, and 58 psi as your fuel rail pressure, why do the fuel trims go positive?

I've had the same issue tuning a 2002 Camaro that had 30 lb/hr Motorsport injectors. The car had a mild cam & AFR heads. Using 43.5 psi as the injector rated fuel pressure, the AFR was very lean at idle, and with a 13.0 commanded PE, the wot was as lean as 14.8 afr!

Once I changed the IFR table using 58 psi as the injector rated fuel pressure, the wot afr just needed to be tweaked using the maf afr error % histogram. The idle afr then was very close as well.

Russ Kemp

[red99]

Bill,

I think I found another site that has flow tested the green tops *at* 3 bar. It's an injector service place: http://www.witchhunter.com/
They have the 0280150558 injector flowing 424 cc = 40.38 lbs/hr

And... Here's a Bosch PDF I found somewhere (I think it was LS1 Tech) that has them listed as 326.8 @ 2.7 bar working pressure. Wierd!

I had my 42# injectors (0280150558) cleaned and flow tested by witchhunter, and they used a static flow of 43.5 psi. They flowed between 436-442 cc/min. Which equals to 41.905 to 42.095 lbs./hr at 43.5 psi.
At 58 psi, these calculate to flow 48.28 - 49.92 lbs./hr.

[redhardsupra]

trims will be off if your VE tune was crap to begin with. set your IFR to values calculated from flowsheet/fuel pressure and adjust VE if it wasn't perfect before you installed the injectors.

[02Z0h6]

trims will be off if your VE tune was crap to begin with. set your IFR to values calculated from flowsheet/fuel pressure and adjust VE if it wasn't perfect before you installed the injectors.

Why would they be farther off though? Shouldn't they just remain the same if all you have to change if the flowrate vs. kpa table per your spreadsheet?

[Russ K]

Why would they be farther off though? Shouldn't they just remain the same if all you have to change if the flowrate vs. kpa table per your spreadsheet?

Just set your IFR table like I suggested and let me know if your fuel trims came down. Then everyone will know for sure. If just the injector change caused your fuel trims to go way positive, then your IFR table was wrong. Lowering the IFR table will bring the fuel trims lower.

Russ Kemp

[02Z0h6]

Just set your IFR table like I suggested and let me know if your fuel trims came down. Then everyone will know for sure. If just the injector change caused your fuel trims to go way positive, then your IFR table was wrong. Lowering the IFR table will bring the fuel trims lower.

Russ Kemp

I'll post back tomorrow Russ. I haven't had time to play with it. Thanks for everyone's input.

[5_Liter_Eater]

It's kind of a moving target. Based on my stock IFR table and the data I've just collected on the stock injectors I'm not convinced that the numbers in the IFR represent the "correct" flow from the get go.

[MeentSS02]

This thread should make my red top install interesting...