Cheapest ECU bypass...

[mr.niceguy]

There are many ways to mod the ECU. But if you cant, you can install a AFPR(adjustable Fuel pressure Regulator) Stock setting is usually 43psi. If you cant get the ECU to reduce fuel input. Cut the fuel supply manually by reducing the incoming fuel pressure. IE lower to 35psi. YOu can get 1 on EBay for $20.

Hows it work? An FPR acts as a constrictor on the return line to your fuel tank. aka like a thumb on the end of a garden hose. higher FP= more fuel better performance, (12.5 AFR) is peak performance. Lower FP = better mpg. DONT go 2 lean though.

This should only be done w/ an AFR(air to fuel ration gauge) and a EGT(Exhaust gas temp) gauge is also a good idea Anything above 1600F and you will be in trouble... eventually sooner or later. 15-15.5 AFR reading is slightly lean but ok anything higher and youll risk damage like melting your cat if you have 1 or warping valves ect.

Now if you wanted to just use an AFPR to enhance your mpg you can. But just remember since the HHO gives more O reading to the O2 sensor I would add 0.4-0.6 to AFR gauge to get an accurate reading.( If you have a higher LPM based on your engine size you could add more, but the rule of thumb is .5L HHO/ 1Lengine) The ECU shoots for 14.7 AFR (stoich) but really this same gas ratio should be about 15.2 w/ HHO. So simply reduce your Fuel pressure until you reach this reading. This setup will cause a check engine light(CEL), but the good thing about it is that the ECU wont be able to add anymore fuel once put in closed loop, just lower the FP till the readings are as state above, about 15.2 and you should be fine.
Check the spark plugs after a week or 2 and make sure they are not white. White indicates a lean cond. Tan is the proper color.

NOTE: only adjust the FP when the car has fully warmed up. It will run richer when the car is warming up. This is not a bad thing.
If youre worried about passing an inspection. Just raise FP back up erase CEL, pass, then turn back down.

edit 11/27: well so far from my results the ECU has just bumped up the injector duty cycle a little bit with the lower fuel pressure resulting in NO MPG gain. Coulda swore that would have worked, just ignore this thread, the ECU is smarter than my idea

[myoldyourgold]

Mr. Nice guy have you done this and had results? Can you give us the particulars? Are you saying that the system will stay in open loop with the check engine light on all the time? What would happen if something else goes wrong and the check engine light is already on so you would not know it? Interesting cheap idea.......

[mr.niceguy]

Yes I have done this but with a completely different setup for a turbo application w/ bigger injectors and an FMU. Ill spare the details.

Basically when you drop the FP the ECU will realize its not getting enough fuel and go into edit: open loop NOT closed loop. This will cause the ECU to go to preset maps based on other sensors. Closed loop is "safety" mode and injects extra fuel. Simply just turn down the fuel pressure till it gets back to optimum AFR's and your good.

Youre right about the down side. The CEL would be on all the time, but that really doesnt bother me. I have a scanner and check my codes 1x/ month along w/ all my other fluids. You can check it more if youd like, but really the CEL is worthless. I believe its just for the OBDII sensors. I have all the info I need on my dash oil pressure battery voltage ect.

[Quebecker]

Yes I have done this but with a completely different setup for a turbo application w/ bigger injectors and an FMU. Ill spare the details.

Basically when you drop the FP the ECU will realize its not getting enough fuel and go into closed loop. This will cause the ECU to go to preset maps based on other sensors. Closed loop is "safety" mode and injects extra fuel. Simply just turn down the fuel pressure till it gets back to optimum AFR's and your good.

Youre right about the down side. The CEL would be on all the time, but that really doesnt bother me. I have a scanner and check my codes 1x/ month along w/ all my other fluids. You can check it more if youd like, but really the CEL is worthless. I believe its just for the OBDII sensors. I have all the info I need on my dash oil pressure battery voltage ect.

I think you make a small mistake. You need to talk to OPEN LOOP MODE
Basically when you drop the FP the ECU will realize its not getting enough fuel and go into open loop.

Regards

[Weapon_R]

I think you make a small mistake. You need to talk to OPEN LOOP MODE
Basically when you drop the FP the ECU will realize its not getting enough fuel and go into open loop.

Regards

You are correct Quebecker. This must also be done in open loop. So again the O2 sensors should be unplugged.

[mr.niceguy]

I think you make a small mistake. You need to talk to OPEN LOOP MODE
Basically when you drop the FP the ECU will realize its not getting enough fuel and go into open loop.

Regards

Woops you are right, I always get the 2 confused because to me open loop would seem like the ECU would be open to sensor readings, but its just the opposite. I edited the previous post.

You are correct Quebecker. This must also be done in open loop. So again the O2 sensors should be unplugged.

I would leave the O2 sensor plugged so I can get a proper AFR reading to my aftermarket gauge, unless you have one that provides its own o2 sensor like a Innovative LC-1. The ECU stays in Open Loop until the CEL is cleared. The ECU uses maps based off the TPS and coolant sensor and dis-regards the O2 reading.(at least in my car 97 probe GT) So its not going to add anymore fuel weather its plugged in or not.

Also would use a digital AFR gauge. Wideband is better, but narrow band will work fine for this purpose.

[Weapon_R]

Woops you are right, I always get the 2 confused because to me open loop would seem like the ECU would be open to sensor readings, but its just the opposite. I edited the previous post.



I would leave the O2 sensor plugged so I can get a proper AFR reading to my aftermarket gauge, unless you have one that provides its own o2 sensor like a Innovative LC-1. The ECU stays in Open Loop until the CEL is cleared. The ECU uses maps based off the TPS and coolant sensor and dis-regards the O2 reading.(at least in my car 97 probe GT) So its not going to add anymore fuel weather its plugged in or not.

Also would use a digital AFR gauge. Wideband is better, but narrow band will work fine for this purpose.

Good point mr.niceguy. Wideband o2 sensor is essential for tuning and a egt sensor. Hard to say weather the o2 sensors should stay plugged in a different cars behave differently.

[Quebecker]

ANd take a look on this document : http://www.autoshop101.com/forms/h43.pdf

[mr.niceguy]

good read. The bottom of pg 6 is a more accurate and defined answer as to what controls the ECU in open loop.

I personally dont see what the big deal is having your engines CEL on then if you can still control the variables that its using in open loop. How do people get worse mileage in open loop if they still are controlling the O2 reading and the IAT/ MAF?
Ill tell ya what Id do. Limit the ECUs ability to read.
If you control the MAF and AIT has anyone unpluged your pre/post cat sensors I would think you would be forcing the ECU to read what you want it to. Your modded sensors

[myoldyourgold]

Well, one reason is because it is against the law in some States. Crazy isn't you actually are making cleaner exhaust and you could get fined for doing it while all the smoking junkers out there get away with polluting most of the time.

I'd rather do it in a way where I could get it certified and accepted by the powers to be.