Wiring diagram and harness for IC

[Jonny Rochester]

While parts of UTAS 2015 car are top secret, the only secret in our wires will be simplicity and basic function.

Currently I am electrical team leader, which includes a Motec M400, and by default that includes engine tuning, and a good look at fuel system, and eventual overall supervision of the engine. I've done this before with non-fsae cars, but I'm after a double and triple check on my bare basic diagram. Dash displays and fancy lights will come later.

630

The right side of the diagram is a copy of the middle section, but shows layout in my relay box. (Retaining the Honda relay box but changing the wiring).

If this gets a tick, we will run the engine on a stand, and then the focus will be on good connectors, crimping terminals, weather proofing the harness etc...

[Jonny Rochester]

120 views and 0 replys. Congratulations to myself for a perfect wiring diagram that would be functional and meets all rules!

I was only 95% sure about the kill switches, and only 85% sure if power to fuel pump and ignition was a good choice. Note that I also have a diode inline with the dash switch to protect the whole system from reverse current to some extent.

We have now wired up the engine on a stand in the workshop. I won't be needing Knock or Lambda to start with. MAP sensor is faulty, but luckily won't need that either.

[sparkmonkey]

It might be worth drafting your loom in TinyCAD or something like that, makes it easier to both review and present. Also taking the ECU off the brake kill circuit allows it to log past the point of the driver hitting the kill switch.

[Menisk]

I'm assuming you're planning on shielding REF/SYNC and just haven't drawn it onto the diagram for simplicities sake?

[Jonny Rochester]

Good suggestions. I have another student drawing up the diagrams with a online program.

Interestingly the Honda cam and crank sensor wires were not shielded. Only the Knock sensor wires had a shield for part of the harness. I could probably get away with this also if I understood how to route the wires away from interference.

We had the MoTeC ADL dash last year. I'm not using this yet in designs, as it saves weight, and cost in cost report. I will plug it in for testing.

[apalrd]

That's a fairly simple harness, good job.

A few comments:
-While not required by rules, it's good practice to high-side drive the kill switch circuit, since it's fairly safety critical. That way, if you have a cut wire, 99% of the time a cut wire will short to the chassis if it shorts to anything, that scenario would cause the circuit to be stuck on.

-Depending on how much current you use for the coils, you could combine them with the injectors and get rid of a relay for simplicity. We use a single relay for the injectors (2x), ignition coil (1x and quite large) and the fuel pump, designed with enough capacity for 2x turbo control solenoids (recirculation and wastegate). The fuel pump is on a 7.5a fuse by itself, everything else on a 10a fuse.

-Depending on how big your fuel pump is, you can drive it directly from the ECU without a relay. I'm not sure what MoTec you have, but the M84 can drive 5a rated/7a peak from the first 2 aux channels. Most fuel pumps for engines of FSAE size are under this.

-We connect our radiator fan ahead of the main kill switch, since it doesn't need to be killed. When we had high-current fans (a 10a fan one year), we wired it directly to a toggle switch on the dash, but we can drive 7a from our ECU and that is enough for our current fan, saving a relay.

Edit: We have used unshielded twisted pair for our VR wires with no issues. We use shielded twisted pair now because we bought a spool of 2, 3, and 4 conductor shielded twisted pair for all sensor wires.

[Menisk]

Good suggestions. I have another student drawing up the diagrams with a online program.

Interestingly the Honda cam and crank sensor wires were not shielded. Only the Knock sensor wires had a shield for part of the harness. I could probably get away with this also if I understood how to route the wires away from interference.

We had the MoTeC ADL dash last year. I'm not using this yet in designs, as it saves weight, and cost in cost report. I will plug it in for testing.

In the cost report you aren't required to cost a standalone data acquisition system. As long as you design your harness in a way that the dash isn't critical to the operation of the car and you could unplug it for comp you're allowed to neglect it but still run it at comp. I would say for the tiny addition of weight having your datalogger at comp is a far better idea. The data you capture at competition is the most relevant data you will capture all year. None of your drivers are good enough to notice a few hundred grams.

Also while you might be able to get away without shielding REF and SYNC I figure that the two sensors most critical to the operation of your engine should probably be shielded just in case. Not much effort to do it but noise on your triggers is something you don't want to chase.

[TiJei]

Hi Jonny,

I don't know which events you are planning to participate. However in Germany your connection between battery and generator would be considered ilegal.
They have a guideline document on the website which shows what is required there.

Timo

[Jonny Rochester]

Thanks Timo. We enter FSAE-Australiasia (Melbourne)

Can you direct me to which document that is?

[TiJei]

Hi Jonny,


I put a link below. You need to create an account on the FSG website. Once you are logged in you can see the documents in the "rules and important documents" section.

http://www.formulastudent.de/fsc/2015/rules/

As you are no intending to come over it is probably not that important.

[Jonny Rochester]

I have our engine running on a stand now, and still using the same diagram as above with the following exceptions:

I have added an ignition igniter as neither the Motec or standard Denso coils have enough built in amplification. (It seams the Honda ECU has the igniters inside it). I used the typical Bosch 4 channel igniter 0227100211. The sparks are now about 10mm outside the engine, which is what is needed to get a good spark inside the engine with high pressure. A spark of 1mm is not enough.

This seams silly, but Motec fire the ignitions in order 1 - 2 - 3 - 4 as they are wired, you have to sort the wiring out yourself to make it fire 1 - 2- 4 -3 at the cylinders. Not all ECUs do this, took me a while to work it out.

You can google this, but I can confirm the following setup works:
Stock crank and cam sensors (12t crank, 3t odd spaced on cam), no teeth removed or modified.
Mode 22
CRIP 431 degrees
Crank 12
Ref and Sync, falling edge
Ref and Sync trigger voltage, 0

I will look into traction control and other functions.