Is it OK to run 30 gauge wire...
 

...for IAT, CLT, Baro, MAP, and O2 from the sensor to MS? The sensor ground and Vcc will still be 22 gauge. The CLT and IAT should have a max current of 2mA (5V and 2.5k bias resistor). The Baro and MAP signals are GM 1 and 2 bar sensors respectively. Worst case should only be 5mA because of the 1K resistor in MS. I did a Google search and read that 30 gauge wire should be able to handle 100mA. Is this right? It looks about as thick as a strand of hair.

Are wires that thin more sensitive to noise? Some lines run near the coils. Also, these wires will be bundled up with the boost control line. Will a PWM signal that close cause noise problems?

Thanks

Internally, I use 30ga wire for a lot of stuff. And while I think you're on base electrically, I wouldn't run it externally for a couple of reasons. First, it's fragile and easily damaged. And second, it's so thin it'll be hard to get a good crimp onto it.

Is there a specific reason you can't use a more conventional 18 or 20ga?

I'm just trying to minimize the amount of stuff going through the grommet in the firewall. That's why I was moving the MAP to the engine bay so I could remove the manifold pressure hose. Now that I think about it, though, I still need that for the boost gauge. Originally I was going to use CAT5 (which I think is 30 gauge) but boost control would have melted it. An RJ45 connector isn't exactly water tight but it does have a positive lock and it's at available locally.

I don't think the wires in a CAT5 cable are going to hold up. They are extremely thin, easy to snap off, and hard to terminate. There are plenty of places to get wires through the firewall, plus you can always drill another if you had to.

be creative with your wiring and use stock wires.

I'm running parallel. The stock wires for these sensors are already in use.

Speaking of drilling a hole; my manager is redoing his truck and is using all mil-spec circular connectors. A circular bulkhead connector would be ideal for me but they are a little pricey and they're the kind of 'scope creep' that keeps dragging this project down.

http://www.hirose.co.jp/cataloge_hp/e12506002.pdf

Heh. Yeah, I've always wanted to use the round, bayonet-locking connectors for something, but they are pricey.

CAT5 cable is 24 gauge. 30ga wire is like hair. In the "real world", 30ga is only ever used for doing trace repairs and reworks on circuit boards and such, never externally.

Abe did a lot of the wiring under his hood with CAT5 cable. I give him shit about it every time I see his car. :D