I have searched and read as much as I can on injectors on this board. But have a quick question

So This past summer I rebuilt my lt1 due to a spun con rod bearing.
I got a cc503 cam and a local shop ported my heads. At the time using advice from here and injector calculators I bought and installed 30# injectors.

Before I put the car away for the winter I had the car dyno'd. We determined that over 5k i was starting to run lean. The rest of the rpm range the tune was dead on. So its either the tune needs to be fattened up up top, or I need bigger injectors.
my best run was 377hp @ 5102 . We didnt go higher then that due to the lean condition.
So now I have a choice. send the ECU back in to retune and see if the 30#'s will hold up. Or do i get a bigger injector and retune for that when i send the ecu back?
I was looking at racetronix injectors, and since the 37# are the same price as the 34# I was going to get the 37#.
Any advice here? We did do a Wideband O2 sensor run, but i dont have any of that data. They will send it to the tuner when i send in the ecu.

Should I get the 37# injectors?

 

Was the 377HP at the rear wheels? If so, what does the drivetrain consist of? You have to use flywheel HP to size the injectors.

Have you verified that the fuel system is holding the required pressure?

 

The 377 was at the wheels, i did not have a fuel pressure gauge on the car at the time, so I can not say if it is holding pressure or not. With the car in storage until spring I wont be able to test for the fuel pressure.
I guess i was a bit light on info on the car as well
its a 97 SS, M6 car. It still has the stock gears in the diff as well.

 

Rough numbers say you shouldn't be over 90% duty cycle at that HP level. That's making pessimistic assumptions on the tune (BSFC = 0.48), and on drivtrain loss (15%).

Check to make sure the injectors are 30 #/HR, check the fuel pressure. Check to make sure the tune has the correct injector constant.

Wouldn't hurt to get a larger injector though.

 

To point out the obvious, you really need that wideband data. Coupled with the injector duty cycle calculated from the data scan during the run, you can see whether you are running out of injector. Was the injector rated at 3 bar, or 43.5 psi? The worse thing you could do is to purchase yet another set of injectors and find either it was not the issue or that they were still too small.
If it is not the injector itself, it could be the fuel supply, Is it a stock pump, or a 255lph upgrade? If so, did you get the hotwire kit? No problems with the FPR?

 

I still have the stock fuel pump in the car. As well as the stock FPR. I am thinking maybe now i will wait for the spring and test the fuel pressure and see if maybe that is dropping at higher rpm's. i am going to email the dyno shop and see if they can look at the data for me ( since I have no clue what I would be looking for) I believe the injectors were rated at the 43.5 pressure. But the engine shop that rebuilt the engine sold me them. I don't know much about them other then they are 30#. i know that's a crappy excuse. kind of another reason i was thinking of getting newer known injectors.

Whats the hotwire kit?

 

Do a search on ' Caspers Electronics 102150 ' The kit wires the pump directly to the +12 v distribution stud with a heavier gauge wire to eliminate voltage drop found in the OEM harness.

 

that search came up with an wiring harness for an LS1, are they the same for the LT1?

 

i have gotten a response back from the tuner for the ECU, they think I need to just send the ECU back in to get the pulse width fattened up at the higher rpm.
As long as the fuel pressure was not dropping at this time.
What are the chances of the pump not holding pressure just at the higher rpm's? The AFR was great up until that. It seems the pressure was being held fine then. Should I send the ecu in to get fattened up? or wait till spring, test my fuel pressure, then send it in?

 

If you have questions about the ability of the pump to hold pressure at high fuel demand conditions, measure the fuel pressure under those conditions. Don't just make assumptions. Hook up a fuel pressure test gauge, and measure the pressure.

I don't know how to explain this any more clearly.

 

The next time you decide to pull the injectors, jot down the Part Number from the edge of the elctromagnetic coil barrel and use this link to get the dope on them (pay particular attention to the instructions at the very top of the page and it will make searching for what you have much easier) :

http://users.erols.com/srweiss/tableifc.htm

Also... as nice as it might be to have a "fatter" set of injectors at the top end of the performance push for HP and Torque...under Daily Driver conditions... having too much unregulated fuel being dumped into those eight cylinders will lean out your oil to the point of reducing its ability to properly lubricate and protect your engine parts from wear. Perhaps its time for an adjustable FPR, a decent book on tuning and the laptop software and ALDL or ODB-II harness combo to allow you to tune your own ECM/PCM to a fair thee well? If you can get past the initial steep learning and confidence curve... being able to adjust your own BIN fuel tables to do different things at different RPM ranges might go a long way toward improving your overall engine performance and leave a whole lot more jingle in your pocket for not having to buy "fatter" injectors...