I think I have a 80-90% solution on my tune - feedback and thoughts

[motrhedx81]

I've been working on my L29 7.4/454 Black Box tune and I think I have a 80-90% solution. I got the SD/VE and MAF tuned close. Then verified that WOT/PE is in the ~12.2 AFR ballpark. Then got the spark timing good (thanks 04silverado6.0). The timing made a crazy difference that I could really feel on the truck seat butt dyno. I logged my last run and wanted to get some feedback on it. Along with any thoughts on the odd things below. Tune and log files attached below.

I can tell that I'm starting to run out of injector if I hold WOT too long. The injector duty cycle gets into 90%+ and creeps up from there.

I really appreciate all the help I've gotten from you all.

There are a couple of odd things I've noticed.

1. The LTFT seem to show lean in the low RPM, low load area. The attached log is after running 5 or 6 ~30 minute runs without resetting the LTFT. When I was doing the SD/VE it seemed like every log kept showing rich (pulling fuel). It never really seemed to settle down.
2. The WB AFR reading is constantly fluctuating and never seems to settle on the commanded ratio. It seems to constantly bounce between ~14.0-15.4. It does seem a little more settled at idle but never completely.

2000_GMC_2500_7.4_4L80E__mod_v1.3.hpt

2025-01-12__4__mod_1.3.hpl

[gametech]

While you are in closed loop, the computer intentionally swings the AF from rich to lean continuously within a narrow range. This will keep your wideband from ever "settling". In open loop (such as at WOT) it should read a bit more steadily.

[motrhedx81]

Got ya. I have noticed that at WOT it's steadier like your saying. Thanks

[abc]

Looks to me like your either out of injector or out of fuel supply. INJ. duty cycle does go above 100 percent more than once in the log and AFR goes way too lean to be safe. I would find and solve that issue before doing any more WOT pulls.

I would also keep transferring the LTFT data to the VE tables, they do show it's rich during the lite load area.
Not that I need to but, I will concur with gametech on your question about WB not being rock solid for you, don't ever expect it to be. Use it more as a ballpark tool and mostly for OL PE scenarios, then watch it for trends, periodically.

[motrhedx81]

Holy crap, you're right. I didn't notice that it went over 100% like that. That's one of the first times I've gone that high in the RPM and hit the rev limiter like that. I'll make sure to stay out of deep WOT for now (I don't really need it right now, other than for S&Gs). My understanding from reading, and what people have told me, is that it's the injectors. They're called 19 lb/hr (I currently have the Bosch upgraded injectors in), but they're actually ~22 lb/hr at 58 psi in these engines. I'm going to start looking into larger injectors for when I do the 0411 swap.

These FAST injectors have caught my eye at the moment.
https://www.fuelairspark.com/8-preci...injectors.html


On the LTFT... is it ok to make adjustments to the VE table without going in a failing the MAF to get back into Speed Density tuning mode?

[gtstorey]

Holy crap, you're right. I didn't notice that it went over 100% like that. That's one of the first times I've gone that high in the RPM and hit the rev limiter like that. I'll make sure to stay out of deep WOT for now (I don't really need it right now, other than for S&Gs). My understanding from reading, and what people have told me, is that it's the injectors. They're called 19 lb/hr (I currently have the Bosch upgraded injectors in), but they're actually ~22 lb/hr at 58 psi in these engines. I'm going to start looking into larger injectors for when I do the 0411 swap.

These FAST injectors have caught my eye at the moment.
https://www.fuelairspark.com/8-preci...injectors.html


On the LTFT... is it ok to make adjustments to the VE table without going in a failing the MAF to get back into Speed Density tuning mode?

ONly use injectors that have full GM data easily available from the seller or a stock GM injector that you can pull the data from a stock GM tune. This counts out most FAST injectors, if not all.

[abc]

On the LTFT... is it ok to make adjustments to the VE table without going in a failing the MAF to get back into Speed Density tuning mode?

Sure it's OK. It's not the prefered method when your that far out in the weeds.
If it were mine, I would get some factory injectors with known good data. Fail the MAF, and start over with the VE table. Then if I wanted to keep the MAFs, go back and tune it next.

[motrhedx81]

I figured I might need to go back and do some more fine tuning. I get impatient and kind of got tired of screwing with it because I've been doing it for so long and the LTFTs didn't seem to want to settle in to a good place. I wanted so see some results, and I wanted to play around with my work a little bit.

These are the injectors I have. According to the site, there's no retuning required, so this shouldn't be an issue, unless someone has experience otherwise.
https://www.fiveomotorsport.com/bosc...-black-knight/

On the larger injectors, I got this spreadsheet from FAST. Is this what I would need?
Fast 303608 Injector Data.xls

[blindsquirrel]

An injector cannot be a 'performance upgrade' and also not require changing the tune. If no changes are needed then it's just a straight up stock replacement part.

[blindsquirrel]

On the larger injectors, I got this spreadsheet from FAST. Is this what I would need?

If FAST is now supplying legit data thet they generated themselves using real legit test equipment or hired someone reputable to generate that data, that's great. But after more than 20 years of them shipping mystery injectors meant specifically only for use with aftermarket EFI (extra specifically, meant for THEIR aftermarket EFI), there's gonna have to be evidence from an independent third party that the data is real and isn't simply something they found from one of their customers who said "yah i used these numbers and they seemed to work pretty good".

[Alvin]

Quite a lot of FAST injectors are stock ones.. so you can get stock data from stock tunes. Not all.

They are selling the LS2 car injector, LS3, GTP white injectors, and shelby 57's rebranded basically as something else. The flow rate they advertise doesn't match up exactly either.. but it is what it is.

[abc]

If you think you need to be in the range of 40 to 60 lb/hr injectors, ask these guys to point you in the right direction for oem injectors and the data. Assuming you don't want to spend the money for something like Injector Dynamics, your best bet is to go with an OEM part number and get the data from the proper OEM PCM file if possible. I'm sure one of these guys will help you out.

It goes something like this: Hey guys, I'm planning on producing about 400 HP to the crank on my 7.4L engine, can you help me out with finding the proper injector and the data for those injectors?
It will also be necessary to describe your fuel system platform.

Remember this: A general rule of thumb, 1 lb/hr of fuel will support 2 HP. IE: 400 HP will consume 200 lb/hr of pump gasoline. Account for an addition 20 percent for overhead and any additional overhead you plan in the near future. In this case 200 lb/hr plus an additional 30 percent overhead, means you need 260 lb/hr of fuel at 100 percent duty cycle. 520hp/2 is 260. 260/8 is 32.5, let's round it up to 36 lb/hr injectors. Usually going a little larger on injector size is much better than spec. too small.

[blindsquirrel]

https://www.ebay.com/itm/274424906026
50.4lb @ 58psi, data from stock L96 tune files. No I don't know why that specific part number injector is so cheap, they were at one point as low as $18/ea from reputable retail stores and $22/ea over the counter at the dealership, they have gone up since then.

[motrhedx81]

Thanks for all the feedback on the injectors. I've read that one if the main fixes/upgrades for these engines is swapping to LS1 injectors; ~28 lb/hr. I wasn't set on the FAST injectors, just something I saw that was a decent-ish price and figured I'd ask.

I like the injector R.O.T. math. The example math you did closely lines up with where I think I am. I just did a re-ring and bearings on the engine, and 454HO cam. According to the GM crate engine page, the cam is supposed to be in the ~440hp, 500lbft range, and with my ported heads, exhaust, and tuning I figure I should be in that ballpark or better (unless I'm missing something). Maybe even 500 hp, 550lbft; a feller can dream, haha. But that's ~200hp over stock so that might be a stretch. Other than that the fuel system is stock.

Do you think I should go a little bigger on injectors based on the info above?

I'll see if I can dig up some specifics on the Bosch injector I currently have.

Just for context, I'm a total newby to the tuning game other than some previous reading. I really appreciate all the help.
Hopefully none of my questions and comments come off as rude. I'm an engineer so what sounds fine in my head doesn't always turn out that way on the other end, haha. My wife reminds me of this all the time.

[abc]

I would go with the advice from blindsquirrel on the injectors. I didn't notice if you mentioned a fuel pump or not but the same rules apply for the pump. Typically oem pumps are sized accordingly for a stock eng. HP support.

[SiriusC1024]

ONly use injectors that have full GM data easily available from the seller or a stock GM injector that you can pull the data from a stock GM tune. This counts out most FAST injectors, if not all.

They're GTP injectors. Data is on the injector data repository thread.

[motrhedx81]

I hadn't really thought about it too much, but it sounds like I may need to look into a fuel pump upgrade with the injectors. Would I confirm this by monitoring fuel pressure while making a WOT hit and watching for pressure to fall off?

[SiriusC1024]

That or calculate.

Stock pump is 255l/hr@4bar.

To find max injector size that's 255*sg(gasoline)/hr = 186.15kg/hr = 410.39lb/hr. 410.39lb/hr / 8 injectors = 51.42lb/hr max injector.

Judging by the log, it's likely your build will utilize far less that 100% duty cycle for 50lb injectors.

[motrhedx81]

There goes that math stuff again. Funny how a little bit of good data goes a long way. Thanks for that.

Yeah, I don't currently plan on doing much in the WOT world other than highway passing, on ramps, and occasional fun. But I do want to try to future proof a little bit. May be some towing in the future. Also, down the road I'd like to make it a 496-ish stroker, but that'll definitely be a few years (and hopefully nothing forces that timeline).

[SiriusC1024]

Those 50lb injectors recommended by blindsquirrel work very well due to their response. Personally, I'd buy new off rockauto. You'd need adapters and pigtails.

Tall EV1's you won't need any of that, and the 36lb/hr (42lb/hr@4bar) will do what you need. Guy running them in a 496 stroker here with injector data in the tune file.
https://forum.hptuners.com/showthrea...l=1#post816432

If you want to go with any particular injector I can convert the Gen III data to black box format if you need it.