Fuel injector data issues

[mjc79]

Vehicle im working on is my 02 Tahoe 5.3 Flex. The vehicle is return style regulator and runs 33lb factory injectors at 50psi. The injector data I was given from Fuel Injector Connection ( and I told them what i had before ordering ) shows 58 psi. Im not quite sure what to do at this point as its confusing me. If anyone can help me figure this out its greatly appreciated. I'll post the injector data file they sent me and also my stock tune file as i plan to start from scratch again


8.1 truck41244@4barBernoulli_IFR_ALL_RANGES36.xlsx02 Tahoe 5.3 Stock Ecm.hpt

[kevin87turbot]

A quick way to calculate the injector flow rate at a different pressure other that what it's rated is to take the square root of the difference of the pressures and multiply that by the rated flow. For instance, if you have a 33 lb/hr injector at 50 psi, and you increase the pressure to 58 psi, it's simply 33 * sq root (58/50) = 35.54 lb/hr.

[mjc79]

Whoops I forgot to add the injectors I'm running now lol brain fart. The new injectors are GM 12613412 flow matched set. The card I was given with them say 44lbs at 58psi. Injector data above is for these injectors

[mjc79]

A quick way to calculate the injector flow rate at a different pressure other that what it's rated is to take the square root of the difference of the pressures and multiply that by the rated flow. For instance, if you have a 33 lb/hr injector at 50 psi, and you increase the pressure to 58 psi, it's simply 33 * sq root (58/50) = 35.54 lb/hr.

Thanks for the help! I came up with 40.85 lb/hr @ 50psi, so since the old tune had 33 lb/hr from 0-80, I would do 40.85 lb/hr the same way correct?

[kevin87turbot]

Thanks for the help! I came up with 40.85 lb/hr @ 50psi, so since the old tune had 33 lb/hr from 0-80, I would do 40.85 lb/hr the same way correct?

That's correct.

[mjc79]

That's correct.

Awesome thanks!! What confused me was the data sheet for the new injectors it showed the flow rate rising with pressure while my stock tune was just solid straight across.

[mjc79]

Had another question regarding these injectors. The injector data i was given didn't have anything but just the injector flow rate, so do i just use the stock settings for the volt offsets, injector pulse, short pulse adder etc from my stock tune or does that need to change also? Tune file for my tahoe is attached. The 50 psi and 58 psi tune differences between the stock flex fueled 02 vehicles and the non flex is confusing me. Pretty much don't know what to enter in for injector specs now the more i keep reading other threads

[mjc79]

Come to find out I was given wrong injector data for the GM 12613412 injectors from the beginning so i'll attach the spreadsheet they just sent me. The guy I talked to said this spreadsheet is set up for 58psi non flex vehicles, but since my tahoe is the oddball return style factory flex enabled system it runs at 50psi and i'm lost at this point on what to do. I have no clue how to use this stuff so can someone dumb it down for me so i can use it please? Thanks

[Matt Vardaman]

Whoops I forgot to add the injectors I'm running now lol brain fart. The new injectors are GM 12613412 flow matched set. The card I was given with them say 44lbs at 58psi. Injector data above is for these injectors

The GM 12613412 are 50.4 at 58psi. So shouldn't they be 46.8 at 50psi?

[Matt Vardaman]

Also I have the same exact part number injectors in my truck. It's at 58psi, but you can copy the min inj pulse and short pulse adder and offset tables. They would still be the same. It is Vacuum referenced return style.


3-15-22 2002 Tahoe Tune idle rpm raised.hpt

[mjc79]

The GM 12613412 are 50.4 at 58psi. So shouldn't they be 46.8 at 50psi?

All of the info I was given with these injectors was wrong from the beginning. In my last post the spreadsheet they sent me today is the correct one for the injectors "supposedly" but the data is in the wrong format and is meant for 58 psi at the rails and not 50 like my setup has. So I'm at a stop right now cause I don't know what to do lol. Had I known it was gonna be this much trouble swapping injectors I would've bought another set of stock ones and been done

[mjc79]

Also I have the same exact part number injectors in my truck. It's at 58psi, but you can copy the min inj pulse and short pulse adder and offset tables. They would still be the same. It is Vacuum referenced return style.


3-15-22 2002 Tahoe Tune idle rpm raised.hpt

I guess I'm just confusing myself for not understanding something. Wouldn't your specs be different though at a different fuel pressure as in the offset tables and pulse tables than mine or does that not matter? I know the flow rate needs changed thats not an issue. I just don't understand why my Tahoe runs at 50psi and not the normal 58 like the rest of the trucks and SUVs lol

[blindsquirrel]

Are you checking fuel pressure at idle with the vacuum hose disconnected and plugged?

Or even initial key-on. Any vacuum applied to the regulator will reduce the fuel pressure from the base.

[kevin87turbot]

I guess I'm just confusing myself for not understanding something. Wouldn't your specs be different though at a different fuel pressure as in the offset tables and pulse tables than mine or does that not matter? I know the flow rate needs changed thats not an issue. I just don't understand why my Tahoe runs at 50psi and not the normal 58 like the rest of the trucks and SUVs lol

As Matt indicated, you'll use 46.8 psi across the board for your IFR.
The SPA and Offset table will be the same as Matt's tune.

[mjc79]

Are you checking fuel pressure at idle with the vacuum hose disconnected and plugged?

Or even initial key-on. Any vacuum applied to the regulator will reduce the fuel pressure from the base.

Lately I have not with this setup. Stock fpr specs for the L59 return style flex engine is 48-54 psi. Specs for the LM7 retutn style are 58-62. Both motors have different intakes, injectors and fuel pressure regulators. This is why I was confused about all this injector data. Since mine is rated at 50 at the rail, and his at 58, the data would be different for everything correct? Or could I just swap the flex fpr for a non flex version and then use all of Matt's data including the flow rate table and be done with it?

[blindsquirrel]

I wouldn't care even a little bit what the spec was in some book somewhere, I would go by what it shows on a real-world known-good pressure gauge. Anything else is guessing.

[truckshop]

Why not just put a non flex fpr and run 58 psi? Is that not an option?

[blindsquirrel]

You would still need to check the pressure with an actual gauge, to make sure the tune file was set up correctly. So why not skip the replacing-the-regulator part and just verify the pressure and then set the injector tables accordingly?

[Matt Vardaman]

Lately I have not with this setup. Stock fpr specs for the L59 return style flex engine is 48-54 psi. Specs for the LM7 retutn style are 58-62. Both motors have different intakes, injectors and fuel pressure regulators. This is why I was confused about all this injector data. Since mine is rated at 50 at the rail, and his at 58, the data would be different for everything correct? Or could I just swap the flex fpr for a non flex version and then use all of Matt's data including the flow rate table and be done with it?

The Injector is Data is determined by the injector itself, not the pressure it's running at. You are over thinking this. Injector Flow Rate will be the only difference in our two files. Read this: http://injectordynamics.com/articles...racterization/ It will help. Run the injector data I gave you for those 50lb/hr GM injectors and be done with it. You can measure the actual fuel pressure only to determine the FLOW rate. So I run 50.4 @58 and you would run 46.8 @50 psi (or measure)

Just so you know, I have a rail mounted pressure gauge. It shows 58 key on engine off, and at Idle when the vacuum opens the regulator it's at 50-51 psi. We are trying to help you. If you understand it or not, you should still use the proper data from Post 9 & 10

[mjc79]

As Matt indicated, you'll use 46.8 psi across the board for your IFR.
The SPA and Offset table will be the same as Matt's tune.

Thank you for the help i appreciate it! I went with Matt's settings and set my IFR to 46.8 and its working fine so far.

The Injector is Data is determined by the injector itself, not the pressure it's running at. You are over thinking this. Injector Flow Rate will be the only difference in our two files. Read this: http://injectordynamics.com/articles...racterization/ It will help. Run the injector data I gave you for those 50lb/hr GM injectors and be done with it. You can measure the actual fuel pressure only to determine the FLOW rate. So I run 50.4 @58 and you would run 46.8 @50 psi (or measure)

Just so you know, I have a rail mounted pressure gauge. It shows 58 key on engine off, and at Idle when the vacuum opens the regulator it's at 50-51 psi. We are trying to help you. If you understand it or not, you should still use the proper data from Post 9 & 10

Yea I was misreading what ya'll were saying and i apologize. Just trying to get this thing going and dealing with other things all at once takes a toll on patience lol. I started out in SD mode to get the fuel dialed in from the stock VE table and it was pig rich. Tried pulling 20 and 10% in the idle areas and for some reason I was over or under shooting it. I put your Ve table from that tune you posted above and only had to pull a percent in the idle areas and it works good so far. Tried loading the current small drive log i did but its not working right. I'll get one back up here soon