RFI and RMI?

[Chuck Leeper]

RFI ?

Electronic gurus.. Am installing a MSD DIS-4HO. Have a new set of MSD wires and new coil and module to go with. [Trying to eliminate an ign failure at max cyl pressure.]
Questions are:
1. What is the best insulator to put on the wire bundles to minimize problems?
I have the plastic "split wrap" matl, but don't think it will do much.
2. Will running the power wires directly to the batt via a route next to the headlite wiring on the core support, allow the wires to be "infected" w/ interference due to their close proximity to other bundles??
3. would adding a grnd from the box frame to the engine help?

4th and last, for those using this setup:
The directions only show hooking the 2 step to grnd thru a button.
Since the trans brake button actually breaks the power to the TB solenoid, how would a person take the 2 step to grnd, using the TB button?? [I'm thinking a relay, using TB power to close the relay and the switched side of the relay to take the 2 step to grnd.] YES/NO??

What effect may a relay have on the release time for the TB and 2 step?? My reaction times are BAD enuf as it is!!!!


THANKS for the help!

 

[ijames]

I don't think that running the msd wires next to the headlite wires will be a problem. Typical relays have settling times of 1-5 milliseconds (0.001-0.005 seconds), and worse, the contacts are bouncing for part of that. They won't bounce all the way back to the first connection but will bounce off of the second connection and back up into midair a few times. If you are using this to ground the msd two-step input it could make the msd think you flipped the switch back and forth a few times during that first 0.005 seconds. I've never done this (on an msd; I've tested relays on other applications) so I don't know if any of this will hurt you or not.

 

[steve hughes]

Chuck , i use a relay as you describe on my car with TB and MSD. Works fine. If you are worried about interference i would think shielding the wires with something like braided stainless and grounding it should take care of it.

 

[Craig Smith]

Chuck, use a solid state relay for the brake. They are much faster than mechanical relays, there is no switch bounce, and they are quite reliable. Oh yeah, they cost a lot too so they must be good.

Thought I'd throw that in there...

 

[ijames]

Yeah, Craig, I think a solid state relay is the way to go here, but if you are triggering it off of the trans brake solenoid you need to make sure you have a snubber diode to absorb the voltage spike when that solenoid is turned off or that spike will kill the control input on the ssr.

 

[ChrisCairns]

Dunno what kinda brake you have in which the button has to "break the power to the TB solenoid".

Are you saying that without power to the solenoid that it's applied all the time?? And do you just have the single wire solenoid??

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I have a 2 wire 'noid. I originally had the black wire going to ground and the red wire going to the button, then to a constant hot connection. Push the button, power goes to the 'noid, brake applied until button released.

When I put my MSD box in and needed a ground for the 2 step, I simply ran a constant hot wire directly to the red wire on the 'noid. Then I ran the black wire back to the button and then onto a ground. I also connected the MSD wire that needs a ground between the button and the solenoid.

Press the button, this completes the circuit to the 'noid and it also provides the grounding of the MSD 2 step wire.

 

[Craig Smith]

Many solenoids have only one wire. Mine is this way. This means that a relay needs to be used in this application.

The other option is to wire the switch to provide +12 right to the solenoid and to power a relay that switches a ground feed to the input on the MSD.