84 1200......What does 4th gear ground signal do?

[dan filipi]

84 1200......What does 4th gear ground signal from the shift sensor tell the Ignition Control Module to do?

(Bottom left of the picture)

 

[backyardtrouble]

The ECM monitors the ground and changes to the response and allows the ignition to change to advancement

 

[dan filipi]

Do you know the advance mapping for all the gears, and what it goes to in 4th?

 

[Steve83]

Interesting...4th and overdrive...lower RPM, less advance...curious if Honda would even publish the advance curves. It would be nice to know!

 

[backyardtrouble]

As 1st, 2nd, and 3rd gears have no ground and running under 2500 RPM's, they run on about 25 degrees BTDC, when you reach Rpm's around 3000 and change to 4th, the ground is recognized in the ECM and changes the Advancement to around 38 degrees BTDC for high speed. I Read this somewhere when i was working on the 1200 i was restoring a couple of years ago...I wrote it down in my manual.

 

[roncar]

 

[dan filipi]

Ok cool.
I'm thinking of using this 4th and 5th position signal to activate a couple different advance curves for the C5 ignition.
Don't know if I'd gain anything, just exploring options.

 

[dan filipi]

So just for the sake of discussion,
What could Honda's intent have been for doing this.

Theories are welcome.

 

[AApple]

No clue on Goldwings, but in automotive design, it is an emissions related function. In lower gears, the timing is not advanced(depending on operating temp). In higher gears, the ECM will advance/retard the timing as needed in an attempt to help control exhaust emissions.
Mid- '70s cars started using this idea, using a temp sensor, gear position switch, and then vacuum controlling the advance on the ignition, and the EGR valve in some cases. For instance, on my '74 Corvette, with it sitting still, idling, I can put the shifter in 4th gear, and the idle speed will increase after a few seconds(there is also a timer in the system), indicating the timing has been advanced.
It's basically an EPA issue...it really has nothing to do with the performance aspect, other than killing some of the low speed power that you would have without the interference of the silly system. :yes:

 

[dan filipi]

Emissions make sense.
I had a car that would do that too, I think it was high gear.

 

[charles franz]

Dan, Break the wire to a NC switch, Jump on her and ride, then open the switch and see what happens, just a thought, Charlie in NC

 

[dan filipi]

charles franz » Fri Mar 28, 2014 7:09 am[/url]":3r6sxypf]
Dan, Break the wire to a NC switch, Jump on her and ride, then open the switch and see what happens, just a thought, Charlie in NC

This 84 1200 is going in my 1100 frame which doesn't use the control module.
Would be interesting to know what the engine does.
Maybe someone with an 84 would unplug it and see?

 

[slabghost]

I might try that when I can ride here. :beg: soon I hope.

 

[ekvh]

Half new school, half old school. Interesting.

 

[backyardtrouble]

I think it was also done for the fuel mileage at higher rpm's , less vacuum, better fuel delivery, spark timing..ect...just some thoughts of mine, :headscratch:

 

[joedrum]

early days of computer stuff and last days of carbs was not great tech at all in my book

 

[slabghost]

I agree. The transition period produced a lot of problem machines.