2007 c6 zo6 e38 fic 1200cc injector scaling questions

[jesusraybrown]

I'll venmo whoever answers these questions enough money for a case of beer.

I wanna start by saying thanks to anyone who's ever come back to update their thread once they found a solution. Y'all are the best, and the reason I never need to actually make a post. To the people who answer the questions, thank you even more. I've been lurking since 2015. I've tuned various H/C/I, turbo, and blown gen 3 cars, so I'm not entirely useless, but this is my first gen 4 car with a lot of money in it, and I'd really like to not blow it up.

2007 C6 ZO6 E38 - 2 bar OS
12615136 MAP sensor
441ci
Forged Mahle pistons
Frankenstein stock castings
Katech torquer 116 cam
Stock LS7 intake/TB
ARH 2" LT's w/ catless x-pipe
Ti trim w/ 3.4" pulley A&A kit (shooting for ~10lbs in Denver)
FIC 130lb injectors (IS303-1200H)
AEM 400 pump setup similar to an A&A setup. -8AN tee'd into stock line/to rails, -6AN from schrader port to AEM FPR (25-305BK), and back to tank.
FPR is not vacuum/boost referenced (set at 58ish psi with gauge on FPR) stock in tank regulator is functional.
E85

I had this car idling and cruising great last weekend with 42lb injectors as a H/C E85 MAF only car. The only change since then is the 130lb injectors, and there are a few things I honestly don't understand. When it was just H/C I tuned it, and it ran great. Then I did the 2 bar OS update, added the blower and fuel system (not injectors), and while I was waiting on the injectors I figured I'd just go ahead and tune it because essentially what works for 42lb injectors at cruise/idle should work for 130lb injectors if all the injector data is entered correctly. With the blower hooked up I was able to tune MAF/VE from idle up to 4k rpm with no issues, and got everything +/- 1ish%, which I was happy with because I figured there would be some adjustment once I installed the new injectors. I just installed the 130lb injectors, added all the injector data from FIC's spreadsheet, halfed IFR/IVT, and doubled stoich, and when I started it, it was idling around 10.5:1. So just to see if it would make a difference I scaled the injectors in the FIC spreadsheet by 40% in order to actually have valid IFR data up to 592kpa, and multiplied the stoich value by 2.1 (See below thought/explanation for reference), and there was no change from what I can tell. It's still idling around 10.5

I have a few questions:

1. MAP offset/linear in Denver
I get 1.86v at my MAP signal, and 4.99v at the hot. 1.86/4.99=0.37x200=74.55+8.33=83kpa KOEO.
Do I:
a. Set the linear value to 210 as to not have such a high offset value in order to reach 101kpa KOEO?
b. Set the linear value to 200, and have an offset value of 26.45 in order to reach 101kpa KOEO?
c. Does the offset value really even matter? Do you leave linear at 200 no matter what, and adjust offset to reach 101kpa in any condition? I think this is the correct answer, but there's so much conflicting information on here. I trust 200/8.33 are the correct values for this sensor, but I just moved to Denver, so I'm unsure about how to handle the elevation change.

2. Injector scaling
I understand if my FPR is not manifold referenced IFR will need to increase with fuel pressure, but with the 63.5lb/hr limit even with scaling 130lb injectors the higher pressure values require more than 63.5lbs.
a. Do I need to only be concerned with IFR up to the 400kpa value? If I scale these injectors 50% it gives me a flow rate of 66.7lbs at the 400kpa column. Do I just tune out that additional 5% difference at the 400kpa column and above, via MAF/VE?
b. If I scale the injectors 40%, all flow rates up to 592kpa are accurate, and I doubt I'll ever see 86lbs of fuel pressure. But are the higher pressure values there for calculations, and do they need to be linear?
c. If I do scale the injectors by 40% is there a correlation between what the required stoich value should be? i.e. if the recommended method is to half IFR/IVT, and double stoich, would a 60% reduction in IFR require a 110% increase in stoich value? I have room for it. This car was previously tuned for E85, so the stoich was around 9ish to begin with, so technically I could more than triple it if needed.
d. Or am I wrong about all of this, and the procedure is to no matter what simply half IFR/IVT, double stoich, and tune out the differences via MAF/VE?

3. Lastly, this car will not enter closed loop until I drive it. Am I missing something regarding VSS, or RPM to enable closed loop? I swear I've searched, and looked everywhere in the VCM editor, and I can't find anything that seems like it would maintain open loop under 2.5k rpm, or 25mph. This car can warm up to 198* sitting still, and will not enable closed loop until it gets up to ~25mph. I honestly don't know if it's RPM, or speed related. Also, injector tip temp is set to zero, but I still have issues with running rich after flashing.

Sorry for the long post, but like I said, I'm willing to throw whoever's willing to help me out some beer money.
I can post files tomorrow. It's too late to do anything in HOA land.
Thanks.

[rabbs88]

1. Leave the correct data for the MAP alone. If your reading 83kpa KOEO then that's accurate. Whats to gain by lying to it to read 101kpa when that's incorrect?

2. I'm no pro with scaling so hopefully someone else chimes in here

3. Post your tune and a log so we can check it. Also, properly calibrate your offset vs injector tip temp table and read this thread about rich after flash. Written by one of the best on this forum

https://forum.hptuners.com/showthrea...ip-Temperature

[blindsquirrel]

You're doing yourself no favors by not having the regulator referenced to manifold/boost, first, in the general sense because boost above atmospheric has the same effect as reducing rail pressure and therefore injector flow, and second, in the very specific sense that you have one of the dumb early ECMs with a 63lb IFR limit and to fit the injectors it needs all the help you can give it, and third, because you have picked supermegalargehuge injectors that are straddling that thin line between being able to fit inside the given limits and not.

With injector scaling, the Stoich table has a hard upper limit of 32.00. So that limit of 32 divided by actual Stoich of 14.68 gives a scaling factor of 2.17 (and some change, but round it down to 2.17), which is 46%.

screenshot.14-05-2024 06.58.42.png

With these scaled at 46%, and 'returnless'/non-referenced and 58psi, you get this IFR table:

screenshot.14-05-2024 06.59.44.png

As you can see, ALL of your non-boost cells are maxed out at 63.5, and in vacuum for normal-type driving where pulsewidths are super small and fine control and accuracy is needed is where bad data will cause you the most headaches. The bigger the injector, the smaller the PW for the same amount of fuel, and just because an engine is capable of +1000hp doesn't change the fact that it needs the same amount of fuel to push the vehicle at 30 MPH at steady cruise, or at idle, as one that's completely stock.

If you hook up that one little vacuum reference hose, then life gets much easier for everybody. Same 46%/2.17 scaling but with the reference hose, IFR looks like this:

screenshot.14-05-2024 07.00.46.png

Much better, agreed?

(p.s. Thanks for not posting your own tune file, I did notice but decided to offer help anyway)

[jesusraybrown]

You're doing yourself no favors by not having the regulator referenced to manifold/boost, first, in the general sense because boost above atmospheric has the same effect as reducing rail pressure and therefore injector flow, and second, in the very specific sense that you have one of the dumb early ECMs with a 63lb IFR limit and to fit the injectors it needs all the help you can give it, and third, because you have picked supermegalargehuge injectors that are straddling that thin line between being able to fit inside the given limits and not.

With injector scaling, the Stoich table has a hard upper limit of 32.00. So that limit of 32 divided by actual Stoich of 14.68 gives a scaling factor of 2.17 (and some change, but round it down to 2.17), which is 46%.

screenshot.14-05-2024 06.58.42.png

With these scaled at 46%, and 'returnless'/non-referenced and 58psi, you get this IFR table:

screenshot.14-05-2024 06.59.44.png

As you can see, ALL of your non-boost cells are maxed out at 63.5, and in vacuum for normal-type driving where pulsewidths are super small and fine control and accuracy is needed is where bad data will cause you the most headaches. The bigger the injector, the smaller the PW for the same amount of fuel, and just because an engine is capable of +1000hp doesn't change the fact that it needs the same amount of fuel to push the vehicle at 30 MPH at steady cruise, or at idle, as one that's completely stock.

If you hook up that one little vacuum reference hose, then life gets much easier for everybody. Same 46%/2.17 scaling but with the reference hose, IFR looks like this:

screenshot.14-05-2024 07.00.46.png

Much better, agreed?

(p.s. Thanks for not posting your own tune file, I did notice but decided to offer help anyway)

Everything I've read about Corvettes says to leave the FPR un-referenced, and keep the stock/in tank regulator intact/functional. Is that not correct? Can I run the stock C6 regulator AND reference the AEM FPR to manifold without issue?

Do you think these injectors are too big for a 441 with 10lbs of boost on E85? My goal is to be around 850-950rwhp, and with the BSFC I read about IIRC they were right in the 950rwhp range on E85.

My apologies for not posting the tune file last night. I was having issues with my internet cutting out, and I kept needing to restart my computer to connect to wifi. I wrote the above book, and lost it while the page was trying to refresh. I had to type it in word, save it, and post it when I got a chance. Anyway, it was late, and I didn't have time to attach the tune file without risking losing the post. It's attached now. Thanks for your reply.

[jesusraybrown]

1. Leave the correct data for the MAP alone. If your reading 83kpa KOEO then that's accurate. Whats to gain by lying to it to read 101kpa when that's incorrect?

2. I'm no pro with scaling so hopefully someone else chimes in here

3. Post your tune and a log so we can check it. Also, properly calibrate your offset vs injector tip temp table and read this thread about rich after flash. Written by one of the best on this forum

https://forum.hptuners.com/showthrea...ip-Temperature

1. It makes sense that I would enter the recommended settings for a gm calibrated sensor, and leave it alone, but again, there's a ton of conflicting information on this. I'm not from Denver, and every car I've ever tuned was in Missouri, where this wasn't an issue, so I just wanted to confirm.

3. Thank you. Tune file is posted. I'll read that. All I know of the issue is what I've watched from Goat Rope Garage's video on the topic. He said zero the table out, so I figured I'd give it a shot.

Thanks for the reply.

[Alvin]

You could.. and I would zero out injector tip temperature on this. There are plenty of OEM GM calibrations with it zeroed out with no issues.

Map sensor scalar/offset are defined.. should not be changed from what they are supposed to be.

A vacuum referenced regulator will give you more head room on the injectors since pressure difference across the injector stays the same. If you have 58 psi of fuel pressure and 20 psi of boost you have effectively 38 psi of fuel pressure. The only issue with these type regulators and I don't see many people talking about it is that the regulator rate often isn't what its supposed to be across the operating range. So there is a little more variance in fueling. Anyone else reading this.. if you have a FPCM equipped car and switch to a vacuum/boost reference regulator.. leave the fuel pressure sensor in the mix. The computer will then compensate when the fuel pressure isn't exactly what it's supposed to be.

In situations like this when the injector table / stoich stuff is maxed out you can do a mix of scaling stoich and scaling airflow. If you do a search you should be able to find post about how to airflow scale a tune. This was a popular method a long time ago before scaling with the stoich tables became more popular. This can mess up torque calculations but being a manual you'd likely won't even know.

[blindsquirrel]

They make plugs that go in place of the little pod regulator thing in the pump module, got to have that done if the system is ever going to be able to make more than 58 PSI. Lingenfelter has them.

If you want it to work right you need either smaller injectors, or a reference to the regulator and the stock pop-off regulator deleted.

Even if it was possible to fit the injectors in under the hard limits, 10 PSI boost with a 'returnless' system gives the same injector flow rate as if you dropped the rail pressure by 10 PSI. If it's referenced it carries the same flow rate whether it's in vacuum or 10 PSI or 100 PSI... rail pressure is always 58 PSI/400 kPa higher than whatever's in the manifold.

So you have 133lb/hr, 950 wheel with 10 PSI and returnless (effective 43 PSI rail pressure) on E85 only needs 108lb/hr. You need to do the referenced regulator (with these injectors, and this early ECM) to make everything happy in the small-PW non-boost normal driving around areas, not specifically because you need more flow when in boost. But you get that as a bonus.

[blindsquirrel]

Yeah, airflow scaling is... yuk. Makes everything so complicated for anybody who comes along later trying to help and wasn't there from the very beginning.

[blindsquirrel]

Or... if the base pressure is lowered from 58 to 43, then the referenced regulator can add up to another 15 PSI rail pressure before the in-tank reg pops off. And adjusting the injector data for different base pressures is pretty easy when all the data is available for such a wide range of Pressure Delta, you just pick the column(s) that match the new base pressure and paste them across the whole tables (IFR & Offset). There should be enough headroom with these injectors for that power even at the lower pressure, especially if referenced.

[biholliday]

wow... if im ever boosted i know who to talk to. lol