Question about the 2/3 mod "rule"
03-23-04, 02:01 PM
#1
R1derful
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Question about the 2/3 mod "rule"
Hi All:
There seems to be some controversy over this "rule". The solution to "more fuel" always seems to be either an aftermarket ECU (PF, Pettit, M2, etc) or a standalone like the PFC or Haltech.
Why not just raise the base fuel pressure 5-10 psi? Can the stock fuel pump not keep up?
This will raise the pressure at *all* times (not just during boost). There will be more fuel pressure at cruise, but the ECU "should" be able to compensate for this. On the Honda ECU, this is known as "short term fuel trim" and "long term fuel trim". I'm assuming the FD3S ECU does something similar based on the way it also samples the O2 voltage.
Sonny
There seems to be some controversy over this "rule". The solution to "more fuel" always seems to be either an aftermarket ECU (PF, Pettit, M2, etc) or a standalone like the PFC or Haltech.
Why not just raise the base fuel pressure 5-10 psi? Can the stock fuel pump not keep up?
This will raise the pressure at *all* times (not just during boost). There will be more fuel pressure at cruise, but the ECU "should" be able to compensate for this. On the Honda ECU, this is known as "short term fuel trim" and "long term fuel trim". I'm assuming the FD3S ECU does something similar based on the way it also samples the O2 voltage.
Sonny
03-23-04, 02:04 PM
#2
Yes, you can use an aftermarket Rising Rate Fuel Pressure Regulator to add more fuel instead of upgrading injectors.. However, you still need something to "trim" the amount of fuel like a simple/cheap fuel computer. However, this is known as the "dirty" way of upgrading the fuel system now that technology has bigger and better things.
03-23-04, 02:19 PM
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It simply amazes me that people try to find a ghetto way around paying:
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
03-23-04, 04:37 PM
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Originally posted by rynberg
It simply amazes me that people try to find a ghetto way around paying:
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
It simply amazes me that people try to find a ghetto way around paying:
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
03-23-04, 04:55 PM
#7
Rynberg comes thru once again and I agree wholeheartedly. 
If you want to play the "more power" game without a safety net($$$) you have no room to bitch about the 13b-REW when it grenades on you.
If you want to play the "more power" game without a safety net($$$) you have no room to bitch about the 13b-REW when it grenades on you.
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03-23-04, 05:03 PM
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Originally posted by rynberg
It simply amazes me that people try to find a ghetto way around paying:
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
It simply amazes me that people try to find a ghetto way around paying:
*$400 for a used ecu
*$300 for a new electronic boost controller (or less for a used one)
*less than $50 for a manual boost controller
There is no controversy about the 3-mod rule. There's either people who have the knowledge and know what they are talking about, and then there's the people that don't. If you can keep your boost at 10 psi with no spikes or creep, you can run all of the bolt-ons, period.
03-23-04, 05:13 PM
#9
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Also I don't think it is soo much as ghetto, but more looking for alternatives, as fmu's do work well in certain applications. It would be better than running stock, and certainly a cheaper route to go. But also agree that buying a performance ecu yields much more benefits. You don't here to much about people putting fmu's, instead of a performance ecu on Rx7's so it must not be the route to go. I posted a similiar thread a while back, and some apparently have done what your asking, but not many.
03-23-04, 05:22 PM
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I wasn't talking about using a rising rate regulator (FMU)...just a simple upping of the base fuel pressure. I've done the FMU route before (not on an RX-7) and it sucks. I would never put an FMU on a car that came turbo from the factory!
I've also done the full standalone route. It was wonderful...complete control, but it took a while to learn that system and since it was on a piston-based engine, I'd be essentially starting over with a rotary-based engine and a Power FC or Haltech. It was a lot of time/work and before I go that route again, I'd like to drive the car for awhile but understand what the limitations of the stock ECU are.
On a car that I tuned before (a turbo Honda), we maxed out the 440cc injectors at 240 whp with a base fuel pressure of 35 psi. Injectors were seeing about 88% duty cycle.
We were able to drop the duty cycle into a safer area (about 78% or so) by upping the base pressure a bit and leaning out the part-throttle maps.
That was a completely safe and very viable alternative to dropping in a new set of $400 injectors.
I wasn't trying to ghetto or cheat anything...just seeing how you guys do things "over here".
Cheers,
Sonny
I've also done the full standalone route. It was wonderful...complete control, but it took a while to learn that system and since it was on a piston-based engine, I'd be essentially starting over with a rotary-based engine and a Power FC or Haltech. It was a lot of time/work and before I go that route again, I'd like to drive the car for awhile but understand what the limitations of the stock ECU are.
On a car that I tuned before (a turbo Honda), we maxed out the 440cc injectors at 240 whp with a base fuel pressure of 35 psi. Injectors were seeing about 88% duty cycle.
We were able to drop the duty cycle into a safer area (about 78% or so) by upping the base pressure a bit and leaning out the part-throttle maps.
That was a completely safe and very viable alternative to dropping in a new set of $400 injectors.
I wasn't trying to ghetto or cheat anything...just seeing how you guys do things "over here"
.Cheers,
Sonny
03-23-04, 05:44 PM
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You already know the stock fuel regulators can flow more, but how do you plan on increasing fuel delivery without adding or replacing something.
read this thread they unearthed it should help you out.
https://www.rx7club.com/showthread.p...threadid=27094
read this thread they unearthed it should help you out.
https://www.rx7club.com/showthread.p...threadid=27094
03-23-04, 07:44 PM
#12
Originally posted by Sonny
I wasn't talking about using a rising rate regulator (FMU)...just a simple upping of the base fuel pressure. I've done the FMU route before (not on an RX-7) and it sucks. I would never put an FMU on a car that came turbo from the factory!
I wasn't talking about using a rising rate regulator (FMU)...just a simple upping of the base fuel pressure. I've done the FMU route before (not on an RX-7) and it sucks. I would never put an FMU on a car that came turbo from the factory!
