Safe Clutch Switch bypass

[D'Ecosse]

As first (I believe) identified by SteveTLS,( http://wotid.com/tls/content/view/18/56/ ) the clutch switch provides more information than just an interlock for the starter.
It also provides an input to the ECM which selects different map (this was further validated by the guys hacking the ECM)

Actually Suzuki uses this feature on all its FI systems.
So it is important that you do not simply jumper out the wires to the clutch switch in order to bypass the clutch switch (so that lever does not have to be pulled in)
Shorting the switch permanently has negative consequences for 'normal' running - some are obvious and others may be more subtle.

For example on the SV650, it has a pronounced effect on gas mileage and you can see the effect of the switch on the injector pulse signal

(Image from TeeRiver published on SVRider)



On a GSXR it makes a significant different to the power output!

(Image from EDR Performance published on WERA forums)



Convinced?

Bottom Line - not a good idea to just jumper out the switch!
Personally, I am not at all inconvenienced by it, but a lot of people seem to not want to have to pull in the lever. So here is safe work-around.

You have a couple of options:

1: You can jumper out the switch but cut the input at the ECM so that it does not see the 'permanent' clutch shorted condition
The downside is that the enhanced starting map will never be selected either.

2. Connect a relay across the switch.
This has the bonus of still temporarily selecting the appropriate enhanced starting map, while removing the requirement to actually pull in the lever.

Here is option 2:



As indicated, you can either connect this at the front/headlight harness, or directly at the starter relay itself. The wire colours are same at either location on both the TLS and TLR.

The signal starter button itself is what energizes the bypass relay.

Very simple mod to incorporate if you feel you really must have that bypass.

.

[zippytlsr]

[thumpthump]

What a great write up

Thanks for sharing again regarding this issue

[Sekon]

Yep it's not a good thing to do. I learned why in Suzuki!

That little switch dose more than tell the ecu the clutch is in/out.

[TLS Walt]

Nice bit of research there D Just goes to show that if you don't know what your doing just leave it alone, you might just be doing more harm than good.

[D'Ecosse]

Originally Posted by TLS Walt

... Nice bit of research there D ...

My part is minimal really!
As indicated in initial post, research credit goes to Steve - he's the one from whom I first learned about this.
The data is just additional reinforcer for those still in any doubt.

The Relay is just a simple work-around I provided for the SV guys, so thought that how-to & a reminder again over here might be worthwhile;
the relay solution is just a little different offering from what has gone before (at least to my knowledge).
A solid state switch (transistor) was consideration but most people can handle wiring a relay.

[Steve TLS]

Excellent work (as usual).

Does the ECU need the clutch switch input for starting as when you're in neutral it seems to make no difference anyway?

The ECU still gets the start signal from the starter button (the Y/G wire, ECU input STA) when you press it so it knows you're trying to start it. (Also how it know whether to throw a crank and or cam sensor fault code I gather - i.e gets the start signal, but sees no pulses from the sensors).

Now we need a scope and see what happens when the STA is taken high with a running engine

[D'Ecosse]

Originally Posted by Steve TLS

... Does the ECU need the clutch switch input for starting as when you're in neutral it seems to make no difference anyway? ....

I was thinking same thing earlier today - there could be an (effective) 'OR' gate on the clutch or start to enable the same map?
Obviously that would allow the start map to be engaged if the bike was in gear (stalled for example) and clutch pulled to allow it to start.
If it really doesn't matter, the simpler solution is just to clip the wire at the ECM.
But do we know that the start switch actually sets the map or just the function you mentioned?
It is conceivable - and seems intuitive that it might also trigger the start map - but is somewhat speculative until someone can validate - maybe its all on the clutch.
I really don't know. Maybe our hackers can decipher?
So who knows how all the logic is tied in - there may be other subtleties.
So I figured regardless, the relay covers the bases and replicates the original scenarios all round.

[Steve TLS]

Originally Posted by D'Ecosse

So I figured regardless, the relay covers the bases and replicates the original scenarios all round.

And that it does.

[TLDV8]

That mirco switch has a limited life span before the internal contacts get pitted.
It is worth replacing even as soon as 40000 kms as preventative maintenance. ..(fwiw)