MicroSquirt.com read only forum (Jan.15,2018)

Okay, I've figured a little more out.
Since I want to avoid modifying the stock harness, I've done some research on the factory ECU and found it uses a 35 pin Motronic type plug. This brings me to a little condundrum: cannibalize an ECU or locate a source for said plug, preferably one like what would be used in making and "extension" harness- mates to the existing plug and is ready to accept wires, so I could just terminate the 'squirt's wires in that plug rather than solder and epoxy to a plug with no locking capability to the harness. Junking an otherwise working ECU is not going to happen, particularly a working ECU for this bike.

I suppose if I could find an ECU with a compatible plug at a wrecking yard, I could strip it and build a board to interface the wiring. But then I'm stuck with getting the ignition wiring through the box since the 500T's injection ECU doesn't interface with the ignition system.

Oh, and if anyone's interested, the 500T's ECU has a 16K eprom on the board. Can't say for sure but it likely contains the program and maps. Wish I had an eprom reader.

This thread http://www.microsquirt.com/viewtopic.php?f=89&t=23475 has me a little concerned.
The person says: "turbocharged Honda CX500. We installed a CX650 case that has two crank VR sensors, 80 degrees apart". That baffles me 'cause the 500T has two VR crank sensors, just like every other CX or GL engined bike has. Some models have ignition advance pulsers, aka VR sensors, mounted on either the crank or the cam. As far as I can tell, the 650T and 500T both share VR sensors on the crank and cam, the difference between the two is that the 650T has additional sensors on the crank for ignition advance whereas the 500T did not and instead relied on boost referencing for retarding the timing. This person went round-and-round with it and from what I read, really didn't come up with consistant replies to queries.

Were I here when the posts started, I'd likely have called shennanigans based on the opening statement I quoted from. There's no reason to change the case, unless one is trying to create a frankenzilla thing.


Am I setting myself up for the same?

abecedarian wrote:...
Since I want to avoid modifying the stock harness, I've done some research on the factory ECU and found it uses a 35 pin Motronic type plug....

I think you will find this is an AMP Tyco connector, and these are available, so you could make an adaptor loom quite easily. I made one for my Yamaha GTS1000 ECU using Toyota or AMP Tyco Japan parts.

Bosch has a part: 928 400 889 which appears to be what I am looking for, can't find a vendor though.

*edit- nevermind this avenue. found a pic and it's significantly smaller than what I have.

This is the ecu connection: I'm looking for the same gender, but for wire attachment such as what might be used to put the plug on a firewall or similar, to which the engine harness would attach.

Another consideration I have is with regards to the air temp sensor location.
The factory air temp sensor is between the filter and the turbo.
Would it be better to put the sensor after the turbo?

And yet another potential issue.

The wiring diagram from the factory manual shows the sensors for the crank share a common connection as do the sensors off the cam.
There are two possibilities, which the right diagram suggests is correct (NE = engine speed sensor as defined by the injection ECU; R=right, L=Left) If there are issues, would it be beneficial to insert diodes between the sensors and 'squirt as shown below?
Just trying to anticipate issues, and have some sort of solution ready.

It seems I have the above sensor issues resolved: I'm going to go with using the bike's NE sensors for triggering the unit at least for now since I'm starting out fuel-only.

Now, the next item I'm going to take on is MAP sensing.

As I mentioned previously, I'm trying to avoid modifying any of the bike's harness and am trying to reuse what sensors it provides.
The bike has 4 MAP sensors, three for injection and one for ignition. As I'm starting fuel only, the 3 relevant ones are P1, P2 and Pb.
Their resistance / pressure has been mapped by others:


P1 is plumbed to the intake just after the air filter, P2 is plumbed to the bike's "surge tank"- between the turbo and throttle, and Pb is plumbed between the throttle and cylinders.
P1 would be ideal for barometric sensing, correct?
Pb doesn't have the range to read boost above a few PSI which would be a problem, correct?
P2 can read well into boost but seems to fall short under vacuum.

Anyone think there would be a problem using P2 if I swap its plumbing with Pb's?
I know I could use an aftermarket sensor and be done with it, except I would be modifying things and I'm trying to avoid that.

Thoughts about fuel "mode"? Alpha-N at low rpms blended to speed-density at high rpms?
As I'm going to be running a wideband O2 as well, I should be ok as long as I'm targeting AFR's?

Turbos aren't my thing, but if your engine is turbocharged, that event area will be more critical than any other AFAIK, so it's more important to have a MAP signal for this part.

P2 in place of Pb is what I'd use too, and FWIW in my tuning work (VE Tables) to date, at small throttle openings the TPS value is more important, as the MAP value changes too quickly, which is why Alpha-N is so useful.

Thanks for the feedback.

Don't know if I should continue with tuning this here or start a new post in tuning.
Over there would probably be a better spot since I've nailed down the sensors I'm going to be using.