EFI shielding

[SuperBuickGuy]

How much shielding is needed? In the Corvette, I'm concerned that the fiberglass body really isn't going to be my friend with EFI - so should I put the computer behind the seats in the battery box (battery is moved to the passenger side). Do I need more shielding? right now is the time to do this because I can run all the wiring on the underside of the transmission tunnel..... maybe even in a metal conduit? or is that too much?

[Barry Donovan]

if in doubt, find an old compuer case, build a box.
just make sure it is real computer SECC metal...
there is the past ten years of idiot with "custom" pc cases,but once upon a time, they made metal just for your thoughts.
I still use it in random places.
I only learne dit as SECC, .8 or .5mm
it is easy to identify anyway.

[hauen]

From my own (admittedly limited) experience I'd be less concerned with box mounting than planning your wire runs. The box is most likely already shielded so wherever you put it is going to be good enough, it's running the injector and ignition wires next to the tps or other sensor wires that can (but not necessarily will) give you fits. I'd run ignition and injectors separately in their own runs and then everything else together. It goes without saying you want your battery to block ground to be clean and tight since in all likelihood that's where to box is grounding to.

[SuperBuickGuy]

C3s are notorious for their problems with electrical interference, sounds like the best idea would be metal shielding wire that's well grounded.

[Bob Holmes]

From my own (admittedly limited) experience I'd be less concerned with box mounting than planning your wire runs. The box is most likely already shielded so wherever you put it is going to be good enough, it's running the injector and ignition wires next to the tps or other sensor wires that can (but not necessarily will) give you fits. I'd run ignition and injectors separately in their own runs and then everything else together. It goes without saying you want your battery to block ground to be clean and tight since in all likelihood that's where to box is grounding to.

^^^^^ What he said.

Do youself a favor and get a copy of the Bosch Automotive Handbook.

[dieselgeek]

The biggest misconception about "noise" in EFI systems is that it comes from magnetic or radiated sources.

I've never, ever once run into a problem where shielded wire solved it.

The Bosch Automotive Handbook has 4 or 5 pages that are GOLD. They explain that the real problems with EFI system noise comes from "coupling" which means, it comes in on power or ground inputs and is caused by other devices sharing the same power and grounds. They point out how modern, OEM EFI installations are set up - the only shielded wire you'll see is on a Variable Reluctance (magnetic!) pickup sensor either on the crank, cam, or wheel speed (ABS). The OEMs run a completely separate power and ground run to the battery terminals, separate from the high-current stuff that causes noise (fuel pump, electric water pump, ignition coil, fuel injectors, electric fan especially).


Instead what you should focus on, at least based on my experience, is keeping those power and ground runs separated from each other. Don't share the same 10' run of 10-gauge wire between the ECU and a fuel pump. Most of what I do is sorting these kinds of problems out and that's where I find most of my fixes for "noise" issues.

[SuperBuickGuy]

cool, I love it when a question results in less work for me.

Any thoughts about putting the computer an associated bits in the middle of the car (in the compartment next to where the battery is located)?

I am planning on simply running my runs directly to the battery (via a fuse, of course)

[dieselgeek]

Yes, ECU close to battery should be good - shorter power runs.

[MR P-BODY]

I think the alt is about the worse case culprit for noise...
I have some sensitive equipment on my boat and I had
to put a GOOD filter on the alt