midnightbluS10
Banned
Someone at s-series.org wanted to know this. I thought you guys would be more knowledgeable about the subject than us n/a people. :wink:
Does that even make sense?
Does that even make sense?
Anyone know about FMU's?
- Thread starter midnightbluS10
- Start date
TurboManiacal
Donating Member
You're trying to start a war aren't you?
ericguy320
Stupid Member
Financial Marketplace Update
Fujian Medical University
maby Fuel Management Units
http://www.nipponpower.com/fuel/vortech_fmu.html
Fujian Medical University
maby Fuel Management Units
http://www.nipponpower.com/fuel/vortech_fmu.html
ericguy320
Stupid Member
same here, i just typed it in seach and found it.Jimmy said:
look at this. its funny cause its true http://maddox.xmission.com/civic.html
Tydriver
TurboLS6 Powa'
FMU's are the poor mans Fuel Calibration. Intended to dump in extra fuel and compensate for lack of a good tuning. Our ECM's are able to compensate for additional fueling as needed as boost goes up. Hence we dont have them on our trucks. FMU's are used on bolt on kits for an engine that was sent from the factory without a form of Forced Induction.
At best an FMU is nothing more than a band-aide. Personally I'd find a better way of getting the fuel to the cylinders than adding more hardware, possibly an ECM change and GOOD tuning. FMU's make the mixture soo rich its not even funny, and they are basically cheap insurance to make sure the motor isnt leaned out under boost. They have the similar effect as the ATR 7th injector has on our trucks, and we all know how well that works.
At best an FMU is nothing more than a band-aide. Personally I'd find a better way of getting the fuel to the cylinders than adding more hardware, possibly an ECM change and GOOD tuning. FMU's make the mixture soo rich its not even funny, and they are basically cheap insurance to make sure the motor isnt leaned out under boost. They have the similar effect as the ATR 7th injector has on our trucks, and we all know how well that works.
Technically they are adjustable rate of gain fuel pressure regulators.
So instead of a typical 1 psi of fuel pressure rise per 1 psi of manifold pressure, you might adjust springs and such in the FMU to provide 2 or 3 (or whatever) psi of fuel pressure increase per 1 psi of manifold pressure.
The idea being that your injectors are too small, and the calibration designed around an NA motor. Your NA calibration might provide 50psi under WOT, but under WOT with say 5psi of boost (mild aftermarket kit for an NA motor) the FMU might provide 60psi of fuel pressure. This gets more fuel into the cylinder, but stresses the fuel pump more (they provide LESS fuel as pressures increase) as well as the calibration is typically rough in these conditions - it's kept safe possibly, but maybe not optimal.
You CAN calculate the possible HP supported in such a situation, given the injector size, the fuel pressure at WOT, and if the pump will support that volume of fuel at the given fuel pressure.
So instead of a typical 1 psi of fuel pressure rise per 1 psi of manifold pressure, you might adjust springs and such in the FMU to provide 2 or 3 (or whatever) psi of fuel pressure increase per 1 psi of manifold pressure.
The idea being that your injectors are too small, and the calibration designed around an NA motor. Your NA calibration might provide 50psi under WOT, but under WOT with say 5psi of boost (mild aftermarket kit for an NA motor) the FMU might provide 60psi of fuel pressure. This gets more fuel into the cylinder, but stresses the fuel pump more (they provide LESS fuel as pressures increase) as well as the calibration is typically rough in these conditions - it's kept safe possibly, but maybe not optimal.
You CAN calculate the possible HP supported in such a situation, given the injector size, the fuel pressure at WOT, and if the pump will support that volume of fuel at the given fuel pressure.
TurboManiacal
Donating Member
^ I knew brian would have the answer. That explains why the later gen Supercharger & now turbocharger guys don't use the Walbro as an upgrade pump. Supposedly Mach has cracked the FMU mystery...only to keep it a mystery from the GP. It appears though that there are people out there that are hungry enough to attempt this on their own.
It *can* work.
If you are going to do it, I'd see about using a quality FMU, one that replaces your stock FPR.
Once the FMU is in place, and you have it set, your injectors will deliver varying amount of fuel - meaning their effective flow rating changes.
On a Syty, we have 32lb/hr injectors. Our FPR's give us 1psi of fuel pressure per pound of boost. Contrary to what people think, this is NOT to give additional fueling for boosted conditions, but it is to maintain a constant fuel delivery rate for the injectors, under a variety of manifold conditions. Consider the environment the injector sprays into - if it is atmospheric pressure, and you have a fuel pressure of 43.5psi, and the injector flows 32lb/hr. If you use that same setup, and inject into a vacuum environment (like into the intake manifold at idle) the injectors will deliver MORE than the rated 32lb/hr, as there is some suction as opposed to the atmospheric conditions. On the flipside, when you inject into a environment with GREATER than atmospheric pressure, the injector will deliver LESS - imagine the air pressure pushing fuel back up into the injector nozzle. So with a boost sensitive FPR, it will decrease the fuel pressure at vacuum conditions, while increaseing the fuel pressure in boosted conditions. Therefore it maintains your 32lb/hr fuel injector delivery rating under all conditions.
In an FMU setup, the injector may have it's normal delivery value (let's say 32lb/hr again) at 0psi, or at idle, but at 5psi, the fuel pressure will increase in a manner that is greater than the 1 psi fuel pressure/1psi boost, actually increasing the injector rating to maybe 34 or 36lb/hr, depending on what the fuel pressure actually is. See the link HERE for actual calculations. So this can compensate for the lack of larger injectors, but you would have to see how far this system can take the engine (how much HP it can support), and determine if your pump can deliver the volume required at that elevated pressure.
If you are going to do it, I'd see about using a quality FMU, one that replaces your stock FPR.
Once the FMU is in place, and you have it set, your injectors will deliver varying amount of fuel - meaning their effective flow rating changes.
On a Syty, we have 32lb/hr injectors. Our FPR's give us 1psi of fuel pressure per pound of boost. Contrary to what people think, this is NOT to give additional fueling for boosted conditions, but it is to maintain a constant fuel delivery rate for the injectors, under a variety of manifold conditions. Consider the environment the injector sprays into - if it is atmospheric pressure, and you have a fuel pressure of 43.5psi, and the injector flows 32lb/hr. If you use that same setup, and inject into a vacuum environment (like into the intake manifold at idle) the injectors will deliver MORE than the rated 32lb/hr, as there is some suction as opposed to the atmospheric conditions. On the flipside, when you inject into a environment with GREATER than atmospheric pressure, the injector will deliver LESS - imagine the air pressure pushing fuel back up into the injector nozzle. So with a boost sensitive FPR, it will decrease the fuel pressure at vacuum conditions, while increaseing the fuel pressure in boosted conditions. Therefore it maintains your 32lb/hr fuel injector delivery rating under all conditions.
In an FMU setup, the injector may have it's normal delivery value (let's say 32lb/hr again) at 0psi, or at idle, but at 5psi, the fuel pressure will increase in a manner that is greater than the 1 psi fuel pressure/1psi boost, actually increasing the injector rating to maybe 34 or 36lb/hr, depending on what the fuel pressure actually is. See the link HERE for actual calculations. So this can compensate for the lack of larger injectors, but you would have to see how far this system can take the engine (how much HP it can support), and determine if your pump can deliver the volume required at that elevated pressure.
midnightbluS10
Banned
Thanks, Brian. That's way more thaqn I expected as a reply.