Injectors for LSX454

[Lancer59]

Hi everyone
I'm setting up a GM Performance 620hp LSX454 with a Fast LSXR 102, LS7 style intake. I am unsure if factory LS3/LS7 injectors are up to the task but they would probably be my first choice if they were within their capability. I am no expert but capable of setting up ford injectors with the help of my Calibrated Success DVD Data. I have been going through various injectors listed on the spread sheet, the 39lb and the 47lb both listed as the same part number: M-9593-G302, at 58psi both injectors look good to me but my question here is, are either of these injectors compatible with my application regarding the LS7 style intake and LS7 style fuel rail.

[Lancer59]

Ok
I will be using the stock LS3/ LS7 Injectors for now to see how they go. If there are any issues I am intending to use Deatschwerks 42 lb @ 3 bar injectors as they would be good for about 48lb/h flow @ 58psi, which I recon would be enough; while data is readily available for these injectors.
I have concerns using 50lb @ 3 bar injectors with the LS1 ECU as I understand this would cause issues that would need to be addressed once the injectors exceed 63lb/h flow; somewhere about 30KPA of vacuume. Though I see other people are running much higher flow injectors with the stock LS1 ECU.
Can anyone explain for me what the issue actually is, assuming there is an issue with running over 63 lb flow with the LS1 ECU and how to work around it.

[Eaglegoat]

There are a couple OEM GM injectors that flow 50/lbs at 4 bar. There are also the LS9/LSA injectors that flow 52lbs at 4 bar. Lots of people don't like to use the LS9/LSA injectors, but if you do everything right they are just fine.

[AutoWiz]

Correct injector sizing math is as follows:
(max hp x Brake-Specific Fuel Consumption) / (numbers of injectors x duty cycle)

For example lets say we have an old ford 302 motor that makes 215hp. Our math would look like this:

(215 x 0.55[n/a]) / (8 x 0.80) = 18.5lb/hr.

If we are sizing anything in our engines by pulling random numbers out of our heads then we get what we deserve. If we build it right then we will always be amazed and impressed with the end result.

If we just go with the biggest injectors we can find then down low we loose resolution where we need it the most. At idle and cruising. Remember bigger means zooming out on resolution. And engines don't make power off of fuel. They just need enough to burn all the air in your cylinders.

[Lancer59]

Thank you for your reply AutoWiz and Eaglegoat and for the formula AutoWiz.

I do have LSA/LS9 injectors stashed away and actually had them in the intake manifold but I was concerned the conical spay from the LSA injectors would probably foul in the injector spacers required for fitment with the LSXR intake. It seems the LSXR 102 / LS7 style intake actually takes LS2 length injectors.

I agree with what you say AutoWiz; bigger is not always better but rather getting the combination right. I lacked the math's, so yes! I was trying to make comparisons with what I consider similar engines. I calculated from your equation adopting 627hp based on the crate motor hp rating.

AutoWiz could you please check my math taken from the equation (627 x 0.55) / (8 x 0.80) = 53.88lb/hr. or say 54lb@58psi, would be as big as I should go.
I more or less broke the equation down as {627 x 0.55 = 344.85}{ 8 x 0.8 = 6.4} 344.85 / 6.4 = 53.88 without chasing too many decimals.
If I have the math right the LS7 injectors need to come back out as they are only rated at 42lb @ 58psi. I calculated 43lb to be at 100% duty cycle @ 627hp.

[AutoWiz]

The LS7 did only build 505hp

[Eaglegoat]

The .55 brake specific fuel consumption number is based on old technology. Most modified and properly tuned LS engines fall between .45 and .50. The ls7 injector is rated at 41.735 lb/hr @ 4 bar. Properly set up that will supply 534-593 hp @ 80% duty cycle. The LS9 will support 665-739 hp @ 80% duty cycle. Your math checks out FYI. But like I said, .55 is based on old stuff. I would use a GM# 12609749 or GM# 12613412.

You should not run a bottom spacer for the injectors. Bottom spacers lead to problems (leaks) and inconsistent fueling in my experience. If you need to run a spacer run a top spacer between the rail and the injector. The ls3/7/A/9, or the ones I posted above, will need a larger thicker O-ring to fit properly in in a fast 102. These O-rings should come with the manifold.

[Lancer59]

On calculating to .5 for brake specific fuel consumption comes up to 49lb. I found LS1 data in the forum for the for the GM# 12613412 injectors but not for the GM# 12609749 anywhere.

Thanks for the heads up with the spacers, I had a look for some top injector spacers and ordered some on eBay from the US, so I should have them in a couple of weeks. The bottom spacers come with the kit, I actually read the instructions twice as I figured they would have been better spaced from above but no they are bottom spacers.

The reason I went back to the LS7 injectors was they are borrowed from a tough 428 crate that made similar Horses. Obviously it was under injected as well (no surprise looking back) it had fueling issues, though unsoughted it ran mid 11s @120mph in a car weighing just under 2 ton. I was under the impression they were 60lb injectors till I read the part no.

[Eaglegoat]

PM sent.

[AutoWiz]

About that bsfc. Your claim assumes a certain level of efficiency that only exists in stock trim. Closer lobe seperation and heavier valve springs and higher output oil pumps have a big effect on bsfc. 0.55 is not old. It is safe math that will ensure you do not undersize your injectors

[Eaglegoat]

About that bsfc. Your claim assumes a certain level of efficiency that only exists in stock trim. Closer lobe seperation and heavier valve springs and higher output oil pumps have a big effect on bsfc. 0.55 is not old. It is safe math that will ensure you do not undersize your injectors

How many times do you want to be shown that you're wrong before you stop?

[Lancer59]

Thank you very much for your help everyone and for the link. Very much appreciated.

[Lancer59]

I have the data and I got two sets of the GM OEM # 12613412 injectors for each, the LSX454 engine and the 428LS3 and put LS3/LS7 injectors away where they belong. So! as it turns out we probably solved two problems in one remedy.

[Eaglegoat]

I have the data and I got two sets of the GM OEM # 12613412 injectors for each, the LSX454 engine and the 428LS3 and put LS3/LS7 injectors away where they belong. So! as it turns out we probably solved two problems in one remedy.

Let us know how it works out.

[Lancer59]

I promise I'll get back to you!
Though I could be a while getting back as the 98 Camaro the engine is destined for, is going through a lot of mods including the 02 ECU as I believe the 98 ECU would be an issue, Dana 60, 4L85E ect.. Once I have all the parts in one spot I will get it all apart and back together but things like the headers for instance will have to be custom made as no one makes extractors for right hand drive 98-02 Camaro's.

[Cody225]

i know this is an old post but if you have to use spacers like I found out the hard way. you should use them on the rail side. my .02 cents.

[Lancer59]

I Promised Eagle goat some time back that I would get back to him and tell him how I went in regards to the injector data and information that he shared with me and my progress with the project.

I used the Injectors that Eaglegoat recommended along with his data. thank you very much for your help Eaglegoat they worked well without a hitch but I had to notched it up a little as I was putting out a little more power than original planned. I finished up running slightly larger Deatschwerks injectors of the same style on the now modified Fast fuel rails with aftermarket twin fuel pumps rated at 1300hp which I borrowed from another project. The engine has a bit more work than originally planned and is making around 650rwhp now. I also changed out the Fast intake for a MSD Airforce 103 Square port LS7 style intake and MSD 103mm throttle body hence the mods to the fuel rail and machining done on the fuel rail adaptors to suit the different intake. The fast intake had a cracked base for unknown reasons that never become clear and was put aside but will hopefully see repairs down the line and probably finish up on my Monaro. I'm currently dataloging the car to get the tune right then into the paint shop. I hope to put the Camaro on the track this year once Willowbank reopens

Its been a long time coming a couple of years too many now, The Camaro has been in and out of storage, COVID and also me working away on the other side of the country for a few years. Furthermore there were those unexpected teething problems etc. Even worse when the work on my part was done under the car without a hoist due to lack of space and I'm not young anymore. The Camaro is right hand drive being an Australian registered car, there are probably less than a hundred of these over here "LS powered 1998-2002 Camaros" all low volume imports as they were never sold in Australia as we had our locally produced Holdens and HSV's over here, so there is little luck finding help or bouncing ideas off someone with expertise in Gen IV Camaros, so there was no looking at another similar car to get any ideas as they are very different from their Australian cousins. I had the headers and twin 3 inch exhaust system hand fabricated to route around the right hand steering and starter motor etc., the big transmission the BMR torque arm, tailshaft, tailshaft loop, between the penhard bars and over the Dana diff and around the fuel tank "very tight under that car, no room to spare." The exhaust system was a work of art that was produced by a friend who sadly is no longer with us. With help from friends we managed to overcome the overheating problems associated to having the 4L85E in such a tight space with zero airflow, then we had to pull it all apart yet again to fit a new transmission due to the overheating, this issue we only discovered only when it was too late, no temp gauge on the tranny. The new transmission is fitted with a transbrake and runs off the controller box rather than running off the ECU like the last one did for a while. The previous 4L85E was pre LS so I had issues running it off the ECU hence the controller box. I am running a B&M megashifter with transbrake button this time around in the manual console with manual shifter boot.