Trionic (T5) Harnesses for C900

[dmgb5]

A couple of points I think are important.

- The stock c900 relays although I'm sure work, do not protect the ECM against reverse voltages that occur naturally from switching the relays on/off. Just for piece of mind, I use ones stock or equivalent Trionic relays which DO have that protection, which also requires some rewiring.

What do you mean by reverse voltages? Are you referring to voltage spikes? Can you explain how the trionic relays are different and/or superior to the stock c900 relays? And also what rewiring was done? Do you add a diode?

- On sensitive sensors that read resistance through the sensor and also use a reference signal for accurate reading, I think soldering is the way to go. Butt connectors are fine for branching power wires , but they can affect readings.

Which trionic sensors use ohms for a signal? Last time I checked they are all voltage based signals. If that is a solder vs crimp comment...there is no measurable difference in resistance through a wire between a solder join or crimp join using a high quality self ranging multimeter.

- I'm not a fan of the standard split loom just because it can retain water and is naturally more bulky and requires itself to be affixed to stay in place. Also HATE wrapping large amounts of electrical tape around stuff, just because I've had to UNwrap a lot of it and it turns into a sticky gooey mess!

I'm just being picky though.

The split loom was a personal/aesthetic and practical choice for me. To the untrained eye, if done right the split loom can be made to look completely OEM...minus the red DIC of course. My goal was to make things look as unobtrusive and original as possible. While it is slightly bulkier than other loom options I find it much easier to open up and perform surgery on if need be and patch up again than sealed loom material. As for moisture getting inside the loom I have yet to experience that even on the 23 year old LH harness I pulled out of the car. Sticky tape is a definite downside to using the split loom though.

[Jordan]

A couple of points I think are important.

- The stock c900 relays although I'm sure work, do not protect the ECM against reverse voltages that occur naturally from switching the relays on/off. Just for piece of mind, I use ones stock or equivalent Trionic relays which DO have that protection, which also requires some rewiring.

What do you mean by reverse voltages? Are you referring to voltage spikes? Can you explain how the trionic relays are different and/or superior to the stock c900 relays? And also what rewiring was done? Do you add a diode?

You can read about transient voltage spikes and "quenching diodes" here . I wouldn't want to take a chance of frying someone else's computer.

Wiring is different because the stock t5 and replacement relays are not double-pole type so the output terminals have to be merged.

- On sensitive sensors that read resistance through the sensor and also use a reference signal for accurate reading, I think soldering is the way to go. Butt connectors are fine for branching power wires , but they can affect readings.

Which trionic sensors use ohms for a signal? Last time I checked they are all voltage based signals. If that is a solder vs crimp comment...there is no measurable difference in resistance through a wire between a solder join or crimp join using a high quality self ranging multimeter.

The temp sensors use resistance and there are reference grounds that are used to calibrate the actual voltages for other sensors. Here is a snippet from my LC wideband install manual "wires should all be grounded to the same ground source. Optimally, these will be soldered to the same lug, and connected to a single point. When this isn’t possible, connect each one to a separate lug, and attach in close proximity. Multiple lugs on the same bolt is not optimal, and can result in unwanted signal “noise.” When possible, soldering is always better than crimping."

- I'm not a fan of the standard split loom just because it can retain water and is naturally more bulky and requires itself to be affixed to stay in place. Also HATE wrapping large amounts of electrical tape around stuff, just because I've had to UNwrap a lot of it and it turns into a sticky gooey mess!

I'm just being picky though.

The split loom was a personal/aesthetic and practical choice for me. To the untrained eye, if done right the split loom can be made to look completely OEM...minus the red DIC of course. My goal was to make things look as unobtrusive and original as possible. While it is slightly bulkier than other loom options I find it much easier to open up and perform surgery on if need be and patch up again than sealed loom material. As for moisture getting inside the loom I have yet to experience that even on the 23 year old LH harness I pulled out of the car. Sticky tape is a definite downside to using the split loom though.

Split loom is OEM, and its not necessarily bad, I just don't like it personally. I'm making these for not just road cars, which can see more extreme environments of heat/weather/vibration etc. Since this was my build/project thread I was just documenting what I did and why.

[paulh]

Harness looks excellent Jordan! This is one of the reasons I've been holding off on doing this on my 900, I want it to be as nice as the harness you have made there, and just don't have the time to do it the right way at present. What are you doing for a crank sensor? I cant remember if I posted up the CAD file of the later c900 flywheel with the proper pattern machined in it, but that would really go nicely with what you've done there.

Paul

[Jordan]

Thanks Paul,

For the race car , Kip had purchased one of Dennis's kits already. I'd really prefer the flywheel machining , but we had it already and it works. Luke is going to get a batch of them done at some point in the near future I think. I actually have to still make a harness for myself for my daily driver, but I happen to part out a '93 9000 last month and stole the bits to run a 5.2 setup... so I'm going to try that.

[paulh]

Thanks Paul,

For the race car , Kip had purchased on of Dennis's kits already. I'd really prefer the flywheel machining , but we had it already and it works. Luke is going to get a batch of them done at some point in the near future I think. I actually have to still make a harness for myself for my daily driver, but I happen to part out a '93 9000 last month and stole the bits to run a 5.2 setup... so I'm going to try that.

Ahh yeah I have thought about the T5.2 setup too, thats my 2nd favorite option to the flywheel, I have one machined up here already, probably going to pop it into my 93 900 once the auto trans blows .

Paul

[Jon1]

I cant remember if I posted up the CAD file of the later c900 flywheel with the proper pattern machined in it, but that would really go nicely with what you've done there.

Paul

Paul, where might you have posted the CAD file? I would like a copy of that.
thanks,

[paulh]

I cant remember if I posted up the CAD file of the later c900 flywheel with the proper pattern machined in it, but that would really go nicely with what you've done there.

Paul

Paul, where might you have posted the CAD file? I would like a copy of that.
thanks,

I posted it somewhere I think, but might as well post it here too. This is courtesy of KeithG, who was a big help with getting megasquirt going on the c900's back in the day, he drew this up for a friend of his that wanted to T5 his car, don't think he'll mind it being posted here. This is for the late c900 flywheel with the big clutch.

Paul

[Jon1]

Thanks Paul!

[Neil_G]

Hi Jordan

A question - who makes these wire sleeves and where can I get some from as they look great !!
(well there would be an image if I could get it to work...sixth one down in your original post BTW)

Finally they are sleeved and set into place.

Attachment:


[IMG_0954.JPG%20[%20265.24%20KiB%20|%20Viewed%20155%20times%20]

thanks
Neil

[Jordan]

Hey Neil,
You can buy the sleeving from Waytek Wire.

[Cark]

Wow, this is really awesome!

I just picked up an exceptionally clean 85 turbo for $500. Needed a head gasket. Been tooling around in it a bit now and chasing vacuum leaks all over the place, and still not making any boost. The wiring is SHOT. I'd say at least half of the factory wiring is exposed under the hood as the insulation has just crumbled off. As much as I'd love to try and keep things original, there are some things that just aren't worth it.

This looks like an amazing solution at a great price! I'll have to keep following this and once I get a few other things sorted may have to see about ordering one from you. I'll hopefully make it down to Wethersfield to visit my friend and have the headliner and sill panels redone. Maybe I could pay you a visit at the same time.

Keep up the great work!

[Geoff]

I saw a picture of that '85 you got. NICE! What town did you find that in?
I've had a few '85s and you're chasing your tail trying to repair the rotting wires in it. The best thing to do is put a nice T5 setup in it. Then you'll eliminate a whole bunch of soy-based wire insulation in the car and you'll only have to chase a few pesky things once in a while.

I stopped by Jordan's shop on Friday. The wiring looks even better in person!

[Cark]

Thanks Geoff! My new 85 was in Nashua. It obviously never traveled far with only 101k miles on it, and never saw winter driving, so no snow or salt. It was purchased new there and both owners lived there. First own was an older female school teacher, 2nd owner was an HVAC guy who I'm assuming mostly drove company vehicles. The car's in great shape overall, and so far I'm only into it for $1200 or so which includes buying it, the head gasket repair, registration, and insurance. So there are definitely funds available for the very little bit of body work it needs to be perfect and a T5 conversion :-)

I'm definitely getting excited about the prospect of T5-ing this bitch! I've got to chat with my Indy and see what he's got for parts cars kicking around and hopefully he can set me up with most of what I need for cheap.

Out of curiosity, is anyone making CPS kits or does anyone have one available? I'll also post in the FS/wanted section.

[Geoff]

I'm pretty sure I used to work on that car when the first owner had it. This was back in '98 when I worked for a SAAB indy on Nashua Road in Pepperell, MA. I'd always see it parked in Hollis and had to wipe the drool off my chin.

http://www.saablink.net/forum/general-classic-900-posts-information/60096.htm
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