1985 Honda GL1200 Limited Edition Computerized Fuel Injection System Upgrade

[Rednaxs60]

Have mentioned specific tuning and new CFI configuration regarding the IAC system upgrade, and using LTFT for VE table calibration.

A small tuning aspect is to compensate for the different fuel injector latencies. I have checked Tuner Studio and could not find a fuel injector offset calibration; however, the MaxxECU has this function. The premise is that injector latency can have a cylinder operate in a lean or fuel rich condition. This is true and I have experienced it. This is the main reason that fuel injector data is very important.

I have OEM Bosch 360 cc/min fuel injectors that have the OEM latency information for each individual fuel injector provided. The ECU settings can be for a "gain" setting used for higher power up to full power, or for an "offset" setting for low powers and engine idle. I am more interested in the "offset" calibration.

The base injector latency is an average of the four injectors or can be a chosen value that would be appropriate. The four injector latencies are: injector 1 - 0.41ms; injector 2 - 0.355ms; injector 3 - 0.368ms; injector 4 - 0.41ms. You can choose either the upper value of 0.41ms, or the lower average value of 0.36ms for the base value.

Using a base injector latency setting of 0.41ms, in the injector calibration section under Offsets, set the injector offsets to: injector 1 - 0.0; injector 2 - (-0.6); injector 3 - (-0.42); injector 4 - 0.0. When the ECU calculates the injector pulse width using a base latency of 0.41ms, the injectors that have a lesser injector latency are being held open for longer than necessary and the affected cylinder(s) will operate in a fuel rich environment. If the injector latency is greater than the base injector latency, the affected cylinder(s) will operate in a lean fuel environment.

You can use the lower injector setting of 0.36ms. This would make injectors 2/3 have a "zero" calibration and injectors 1/4 have a calibration of 0.05ms.

Having mentioned this, injector offsets will be used but after the VE tables are better calibrated.

Just another aspect of engine tuning with an aftermarket ECU.

 

[Dusterdude]

I may have missed this, but are you using batch fire or sequential fire for the injectors?

 

[Rednaxs60]

It's in post #3. Sequential fuel and ignition. Best option for this old girl. A new aftermarket stand alone ECU makes this rather "easy" relatively specking. Keeping the OEM wasted spark and paired fuel injection keeps component cost down, but you're dealing with components that have no component data scubas latency, dwell times and a person will need to sped additional time experimenting with component settings to dial in the engine tune. Sometimes it's better and faster to use an "out with the old and in with the new' philosophy.

Time to update the new configuration:

MaxxECU Sport
Sequential fuel and ignition
Spark units have been replaced with a Bosch 211 four channel coil driver
Ford COP units
External Lowdoller Motorsport MAP sensor
External Lowdoller Motorsport Fuel Pressure sensor
Hall effect sensors for crank and cam shaft sensors - Cherry GS100701
OEM TPS
OEM Bosch 360 cc/min fuel injectors - sourced from Canadian Performance Injection (CPI) Alberta Canada
MAP vacuum block - integrates all 4 cylinder vacuum connections
Aftermarket FPR valve - maintains system pressure at approximately 40 PSI
Dual O2 sensors, one for each cylinder bank - provided by MaxxECU, integrate nicely with the MaxxECU

Recent Addition(s):

IAC Motor - Walker product 215-1061

The OEM CFI IAC system will be completely removed. Mentioned in a previous post that the IAC system reed valves would be "gutted" and reused; however, this will not be the case. Has to do with supplementary air supply hoses. It is recommended that these should be equal length to each cylinder. The original OEM CFI IAC hose routing goes to cylinder 2/4 first then to cylinders 1/3. This creates an imbalance where cylinders 2/4 get a better supplemental air supply than cylinders 1/3. Small issue but needs to be addressed.

The new configuration will be the new PWM IAC motor supplying supplemental combustion air to a vacuum/mixing block, supplemental air hoses to each cylinder, equal length. The recommended supplemental air hose ID is 5 mm. Have to admit that I'm using AI for a lot of the leg work and have to sift through the information to make an informed decision. Looked at some pictures I have of a stepper motor IAC installation and the 5 mm size should work.

The installation of the IAC and crank trigger wheel should be the final component change after which it's road trials, and enjoying the bike. Engine tuning will be ongoing, finding out nuances such as fuel injector offset/gain calibration will not impact on riding this old girl.

Cheers