What's the best way to go about it.
I have 440cc injectors.
Stock fuel pump.
Cartech 2025 FMU is on its way.
Is it better to
a. Keep my current injector constant and lower fuel pressure with the larger injectors to get the correct afr at idle then tune my pe from there using my fmu for boost.
b. Keep my stock fuel pressure and change my injector constant using the FMU in boost and adjusting pe from there.
c. Lower my fuel pressure AND adjust my injector constant to compensate while using the FMU to help with boost and tuning pe from there.
I don't want to go too far above stock fuel pressure (even in boost) because I'd like to avoid another pump if I can.
What are some thoughts/experience about this?
I have no experience with tuning with FMU's, but i would say stay away from option a. Your injector constant is the basis for all your fueling, and the closer it is to "correct" the easier it will make your life after the install of the injectors.
What ratio is that particular FMU with reference to boost PSI and how many pounds of boost will you be running? Even with a 4:1 FMU, its easy to get fuel pressures beyond the capability of the stock pump. And remember that flow vs pressure is a geometric relationship, so to get double the flow, you need to multiply the pressure by four. to get three times the flow, you need to multiply the pressure by 8.
I "thought" the idea of running an FMU+HPT set up was to overcome the fact that we only have a 0-100 range of VE to work with (plus or minus the available offset), so its easy to run off the VE map with high HP applications. The FMU adds more fuel in boost so that you can keep the VE offset fairly low and not have your low RPM characteristics go to hell.
Good luck and i'm listening
And remember injectors do not like to go above 83.?? psi of pressure. They will fail to open above that pressure.
What would you guys say the limit of the stock pump is?
I was thinking a 1:1 or a 2:1 ratio. I'm only seeing 12-13 lbs of boost.
Wrench Monkey wrote:And remember injectors do not like to go above 83.?? psi of pressure. They will fail to open above that pressure.
This is untrue of ALL injectors bud. We've got the proof with my car. I don't know if they are working properly above that pressure, but they are giving me enough fuel for over 20psi out of a 60 trim. I'm not sure what my fuel pressure is but it's over 100psi. I've got a 2:1 disc that I'm waiting to put in my fmu, the only reason it's not in yet, I'm going over 30psi this year and don't wanna cut myself short on fuel. I do not have the Cartech unti though.
I was running a stock pump to god knows what for the duration of boost. Up until the white car came to be I was running stock pump, it was hurtin at about 15psi outta my turbo with 60 lb/hr injectors. Just a lil food for thought there. I would say stock pump is reliable to 300whp beyond that you're rolling the dice.
A 1:1 you might as well only have a fuel pressure regulator. A 2:1 will be optimal for most applications set to stock fuel pressure. I'm running out of posts for the month. I've been busy harrasing a punk in the racing forum and keeping my updates thread up to date. I will do my best to keep you informed, feel free to bing the information I pm you to this thread to verify what I'm saying.
This will probably be my last post here until the first. I'm saving my last few posts for my thread over in P&M, I will keep tryin to help though.
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
Im willing to bet you were overheating the injectors (clipping them)
Skunk wrote:Wrench Monkey wrote:And remember injectors do not like to go above 83.?? psi of pressure. They will fail to open above that pressure.
This is untrue of ALL injectors bud. We've got the proof with my car. I don't know if they are working properly above that pressure, but they are giving me enough fuel for over 20psi out of a 60 trim. I'm not sure what my fuel pressure is but it's over 100psi. I've got a 2:1 disc that I'm waiting to put in my fmu, the only reason it's not in yet, I'm going over 30psi this year and don't wanna cut myself short on fuel. I do not have the Cartech unti though.
I was running a stock pump to god knows what for the duration of boost. Up until the white car came to be I was running stock pump, it was hurtin at about 15psi outta my turbo with 60 lb/hr injectors. Just a lil food for thought there. I would say stock pump is reliable to 300whp beyond that you're rolling the dice.
A 1:1 you might as well only have a fuel pressure regulator. A 2:1 will be optimal for most applications set to stock fuel pressure. I'm running out of posts for the month. I've been busy harrasing a punk in the racing forum and keeping my updates thread up to date. I will do my best to keep you informed, feel free to bing the information I pm you to this thread to verify what I'm saying.
This will probably be my last post here until the first. I'm saving my last few posts for my thread over in P&M, I will keep tryin to help though.
Sounds like Version 4 may be come soon.....
P&P Tuning
420.5whp / 359.8wtq
Wrench Monkey wrote:Im willing to bet you were overheating the injectors (clipping them)
That's what I was thinking as well, but I still question how GM was able to supply enough fuel with their small injectors.
I also wonder why my air/fuel ratio was okay. It was 11.3 under wide open throttle. Maybe the valves were closing before enough fuel was sprayed into the combustion chamber then, when the valves opened, the fuel in the head combusted, then it was all sucked out of the exhaust where my WB02 could read it? Maybe.
Actually in Higher horsepower applications this is the only way i can see HPT working on a 1 bar map sensor, a small ratio like a 4:1 should work nicely ran into a similar problem on QBE's car, ran out of VE to work with
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Rodimus Prime wrote:Actually in Higher horsepower applications this is the only way i can see HPT working on a 1 bar map sensor, a small ratio like a 4:1 should work nicely ran into a similar problem on QBE's car, ran out of VE to work with
That's fine, but he's insisting on using the stock pump, and at 4:1 boost reference, he will quickly kill the stock pump. at 10 lbs thats already 40 over static. What is that like 90PSI actual fuel pressure? To do it right, you need an upgraded pump...
oldskool wrote:Rodimus Prime wrote:Actually in Higher horsepower applications this is the only way i can see HPT working on a 1 bar map sensor, a small ratio like a 4:1 should work nicely ran into a similar problem on QBE's car, ran out of VE to work with
That's fine, but he's insisting on using the stock pump, and at 4:1 boost reference, he will quickly kill the stock pump. at 10 lbs thats already 40 over static. What is that like 90PSI actual fuel pressure? To do it right, you need an upgraded pump...
Correct if stock pump could reliably handle 90-100psi Hahn wouldn't have included one in their kit.
You need to get the most fuel out of HPT/Current Injectors as you can, then use the FMU if you still need it. I'm looking at putting a restricter on my signal line for the BEGI since I don't need 90psi, that takes my 440c injectors to something like 600cc range. I have been playing around with this lately because up until now I have been running relatively low boost and not needed to worry about it.
It seems increasing the injector constant above what it SHOULD be helps add fuel because the computer thinks the injectors are smaller, but that can only go so far as you top out what its calculating duty cycle (Which might not necessarily be a bad thing). I'm going to see if the IPW Multiplier will possibly help add some fuel up top so I can limit usage of the FMU. I haven't been able to get any other information on that table, or seen anyone make use of it.
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Hahn Stage II - Mitsu TD06-20g |3" Turbo-back Exhaust | 61mm Bored TB |
HP Tuners | Innovate WB02 | Spec Stage 3 | Team Green LSD | TurboTech Upper | Full Addco Sways | Sportlines & Yellows |
My IPW Multiplier is like 1.55 now. I'm getting the fuel, just not the IDC that's good for the injectors. I plan on a small ratio. Probably 2:1.
I can see how changing the Injector Constant would help in boost, but it would make the rest of driving richer. I would hate to rely on my fuel trims to unscrew it.
If I need to, I'll put in an MSD inline pump, but I hope it's not necessary.
Admiral Jedi wrote:My IPW Multiplier is like 1.55 now. I'm getting the fuel, just not the IDC that's good for the injectors. I plan on a small ratio. Probably 2:1.
I can see how changing the Injector Constant would help in boost, but it would make the rest of driving richer. I would hate to rely on my fuel trims to unscrew it.
If I need to, I'll put in an MSD inline pump, but I hope it's not necessary.
That's why you subtract fuel from the rest of the VE tables by tuning using the histograms.
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Hahn Stage II - Mitsu TD06-20g |3" Turbo-back Exhaust | 61mm Bored TB |
HP Tuners | Innovate WB02 | Spec Stage 3 | Team Green LSD | TurboTech Upper | Full Addco Sways | Sportlines & Yellows |
^ Wouldn't that only affect PE?
I'm talking about regular driving? Outside of boost and PE.
Upgrading the pump is a minor problem
VE tables are used for both
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
