I am trying to bone up on this computer controled fuel system. I am used to carborators. I have been reading in the tech archives about Honda fuel systems and I need to know a few things - any help will be appreciated.

I am understanding that the stock ECU is a saturated system. This means the injectors are running at 100% - Right???? If so, are pulse width and rate fixed w/o reprogramming the ECU? OR will the O2 sensor tell the ECU to compensate for a lean mixture?


See - I am trying to dial back the fuel to this engine. And I am confused - if the ECU controls the fuel curve and the pressure regulator is vacuum operated - if I use smaller injetors or an adjustable fuel pressure regualtor - does the ECU compensate with more fuel?

Normally - I would just change jets. But becasue I do not understand the functions of the system - I am having a hard time figuring out what to do. I do not want to buy a variable air/fuel controller !! I would like to be able to downsize the injectors or back off the rail pressure.

Thanks for any help!!

92 Si Hatch


[Modified by tbisme, 2:15 PM 1/3/2003]


[Modified by tbisme, 2:16 PM 1/3/2003]

 

Get an adjustable FPR, that way you can drop the pressure down to 20 PSI if you dare.

 

. Race, do you think 20psi will make it run to lean? Thats not fair to ask you that considering you dont know my exact situation. Anyway i was more concerned with how the ecu would react to the reduction of fuel to the cylinder.

thanks for the input


[Modified by tbisme, 3:20 PM 1/3/2003]

 

Fuel pressure is greatly dependant on mods, and if it's N/A or boosted, etc. For stock or slightly modded, 20 is way too low. What I meant is that you CAN go down to 20 with an adjustable FPR. Depending on the ECU and which sensors the car has there are a number of things that effect fuel, o2 sensor, knock sensor, etc. Also the amount of vacuum the engine is making directly affects fuel pressure, depending on if it's hot, cold, or if there are vacuum leaks, etc. Unless you really understand injectors, and the relationship with the ECU, I wouldn't mess with changing them. However you may want to see if RC engineering can "tune them down" if that is what you desire.

 

Are you talking about reprogramming the ECU? I heard that was a no-no because you cannot get back to your baseline. What do you think? Would only an FPR dial it back just the wee bit that I need? It runs like a champ - it just has the whole back of my car black. And I am worried about washing down the cylinders with too much fuel. Thanks - this is all great info!!

 

Something that might be simpler is checking the timing. If it is retarded it will run a little rich. Advance it a little. I usually advance mine to 2 degrees more advanced than spec and don't have any knock on pump gas. If you don't have a timing light I think Autozone will loan you one for a deposit. That is something that is a lot cheaper than getting a new FPR. I'm also assuming you have done a tune up and compression test recently and that everything is running good.

 

I set the timimg barely ahead of the stock location based on my factory service manual specs. Isn't the timimg controlled by the ECU or not? Becasue it did not make much difference even way advanced. ???????
By the timimg light - the mark did not move much - maybe 2 or 4 degrees even while moving the distributor lock to lock.

 

You have to jumper the service connector whhen adjusting the timing, and make sure the idle is set right.