Hi,
I am looking at extending a TPI harness and am wondering what the maximum length of the wires should be. I don't think it will have to be extended more than a foot or two, but I wasn't sure how far was too far. My plan is to run basically all new wires, so no splicing hopefully.

Thanks,
Douglas

 

I just did a mix of new and spliced wires in my ls1 ecm conversion using a tpi harness and ls1 harness. I just used 18 gauge everywhere. Some extensions are mostly all 18 gauge, some are half and half 18 and oem which looks 22 or smaller in some wires. I made my harness almost 8 inches too long by accident but everything works well

 

How much did you end up extending the harness?

 

I've seen ECMs installed in the trunk of hotrods...

 

Thanks Six, that makes me feel better!

 

At 10 feet, voltage drop on your 5v stuff (TPS, MAP, etc) will be just under 5% with 18 gauge wire. With 16 gauge the voltage drop is only 1.6%.

I don't know what the factory length is, but lets say it's 6 feet and you go to 8 feet. You will lose a 1/4 volt assuming around an amp.

-- Joe

 

Hi Joe,
1/4 volt seems like a lot for the TPS for how picky it is. Sounds like I'll need to upgrade most of the sensor wiring to 16 gauge.

Thanks, Douglas

 

My harness is about foot longer than stock tpi. Some wires go from ecm to throttlebody at 18 gauge thickness. My tps and iac are fine at this length in 18 ga. 16 is big and your harness will be fat and heavy. Mine is already thick enough at 18 gauge.

Also it seems alot of the gm wiring is smaller than 18 gauge and runs pretty far spans.

Look for my 24x efi sbc conversion thread for pics of wiring