1985 1200 GW FI Model PnP new ECU

Knew I had to take some time off from the other EFI thread, but I do continue to monitor, comment and search the other forums for information.

My latest brain child is why can't we have a PnP Speeduino ECU for the '85/'86 1200 GW FI models? Bit of a pie in the sky issue right now, but not insurmountable. This thread is hypothetical at best.

Already know the next question. When are you going to get on with it? Not going to happen for a while, if ever, but something to brainstorm about for the next while.

This Speeduino forum thread demonstrates that this is a possibility. Speeduino forum thread: https://speeduino.com/forum/viewtopic.php?p=58322&hilit=Arduino+Mega+pro+mini#p58322

This thread is a fellow doing a custom PnP Honda OBD2B Arduino Mega Pro Based ECU (fits in stock case) for his wife’s ’01 Honda CRV 5-speed.

The design can be done in Eagle, KiCad, or some other program that allows for PCB design, not just schematics.

He is using the Arduino Mega Pro, the same controller I just bought for playing with. The design can be based on the Speeduino interface board v0.4.4 to simplify connecting to the engine tuning software Tuner Studio.

The interface board can be made to fit the OEM enclosure. The 35 pin ECU enclosure connector would accept the OEM wiring harness connector.

The base features/functions would be for a wasted spark, paired fuel injectors. Most of an EFI features/functions can be used because the basic EFI components are fitted. The trigger system can be dual wheel utilizing the existing crankshaft and camshaft trigger wheels. The crankshaft VR senor can be used with the signal being conditioned from a sine wave to a digital square wave. Using the camshaft VR sensors may work, but if not, need to use Hall Effect sensor(s).

Challenges include:

• Duplicating the input signal to the travel computer for a dash tach signal and correct operation the fuel management system;
• Duplicating the OEM ECU diagnostics;
• Using the two PB sensors for MAP signal;
• Duplicating the “get home” aspect of the OEM engine tuning;
• The most challenging, using two camshaft sensors used for fuel injector timing.

Most other components can be connected directly to the Speeduino ECU. Need to install a wide band oxygen (WBO2) sensor.

A Speeduino PnP ECU would benefit the owners of the ‘85/’86 1200 GW FI Models. You would be able to adjust the engine tune when issues arise that are not the result of a failing or failed CFI component.

The new ECU would have a barometric sensor installed similar to the OEM ECU.

The Speeduino Project is open source, and because of this, you can take a design and modify it to suit. You can take the programming/code and modify to suit. What this implies is that a design could be done and bench tested. Once this is proven, next step would be to have the interface board produced and components identified, and beta testing done in real time.

Cheers

Slept well last night, always good to get information you are thinking about on paper so you don’t lose it and you don’t mull it around keeping you awake.

I am no expert in the field of EFI, programming and such, but I do like to dream. Dreams never die just the dreamer. We’d still be travelling in Red River carts if someone didn’t step up to the plate.

The size of the interface board can be tailored to the original CFI ECU enclosure. There is additional space in the CFI ECU enclosure to expand the interface board to include a section for on-board diagnostics that would be similar to what is presently fitted.

The Arduino Mega Pro processor could be incorporated into the interface board. This would free up space in the enclosure. There are a couple of interface boards out there that have done this, the Ocelot from WMTronics, and one called the Warthog by a fellow on the Speeduino forum.

The MAP and barometer sensors would be installed on the new interface board. Using a new MAP sensor instead of the OEM pressure balance (PB) sensors would be recommended, not necessarily required, because these older PB sensors do degrade after some 40 years. I have read on a forum where the OEM PB (MAP) sensors were bench tested and within specifications. The same sensors when installed tested poorly. This is an important issue in that the fuelling profile for the ‘85/’86 1200 GW FI models is dependent on an accurate signal from the PB (MAP) sensors for engine load. A degraded signal from the PB sensors can alter the engine load being used for engine start, fuel enrichment on start and warmup, and during normal operation at temperature. This generally results in a fuel smell on engine start, low initial idle. Something to consider.

To compensate for the choice between the OEM PB sensors and an on-board sensor, a “jumper” would be used to switch between the two.

The two cam sensors, GR and GL, require quite a bit more thought. These are used for engine phasing, determination of a cylinder at TDC. The CFI ECU uses the signals from the crankshaft trigger wheel and the camshaft sensors to accurately control the engine ignition timing and fuel injection.

The manual(s) detail the ignition firing sequence.

The 2 camshaft sensors indicate to the CFI ECU when a cylinder is at TDC. The GR sensor indicates when cylinder #3 is at TDC, the GL sensor indicates when cylinder #4 is at TDC. The crankshaft trigger wheel sends 8 pulses (8 tooth trigger wheel) to the ECU. On the fourth pulse from the crankshaft trigger wheel after a TDC signal is received from a camshaft sensor, the CFI ECU triggers the respective fuel injectors.

The OEM schematic indicates that the GR sensor controls fuel injectors 1/3, and the GL sensor controls fuel injectors 2/4.

The new ECU interface board would need to be configure to use an OEM CFI camshaft configuration, or switch to 4- channel fuel injection scenario. Wasted spark ignition would not be affected. More complex board configuration and programming/coding, but not a show stopper.

Consideration should be given to changing the camshaft VR sensors to Hall Effect sensors. The OEM VR sensors do not provide a stable signal for a new EFI ECU such as a Micro/Mega Squirt or Speeduino. There may be a way to make these work, but this would have to be investigated.

More to consider as we delve into this issue.

Cheers