can someone tell me a good way of grounding my MSEDIS
should all my ground be grounded to the car at the same spot?
can some one tell me the right way to ground my system.
also what are your thoughts about those grounding kits sold on ebay?
thanks
correct way to ground my ms
Moderators: jsmcortina, muythaibxr
When you install your Megasquirt you need to run all the grounds to the same point on the chassis. One thing you need to verify is that the engine is properly grounded to the Chassis, and that the Battery is properly grounded to the engine.
The last Cobra I built had a #2 cable from the negative of the battery to the Engine block from there I ran a large braided strap to the frame (chassis). I also ran a 4 gauge ground wire from the engine ground wire to the alternator bracket and installed another strap to the transmission case. I never had starting problems on that car, and the starter turned over the 10.5-1 compression 351 engine at over 250 rpm, it always started with just a flick of the switch.
On Vehicles that have a subframe or full frame, you want to run a ground strap from the steel body to the (sub)frame as well.
When you connect grounds to structure such as the frame, or sheetmetal chassis, you need have metal to metal contact, after removing the paint, wire brush then clean the metal with a fast drying solvent such as Lacquer thinner or Alcohol, and immediately wipe with a clean dry rag to wipe off any residue. Keep cleaning in this manner until no residue shows on the clean dry rag. Don't forget to clean the cable connectors too. You want the ground lug directly on the sheet metal, no washers under the lug. After torqueing down the ground wires, it's a good idea to hand brush some primer around the bare metal to prevent corrosion.
My thoughts about the Grounding kit's on e-bay? I'm sure you get a better ground by adding one of those kits, but I wouldn't use it, for one thing, they come with an aluminum battery connection (no good) and they don't tell what the wire guage is, most of the brackets shown look like plated stamped sheet steel (also no good). On a system like that the battery connector should be made of lead copper or brass, the leads need to be at least #4 guage copper wire, the common ground plate needs to be at least 1/8" or #10 guage copper plate. You can do the same thing with just a few straps from one part to another, and you'll get a better connection that way with shorter wires.
The last Cobra I built had a #2 cable from the negative of the battery to the Engine block from there I ran a large braided strap to the frame (chassis). I also ran a 4 gauge ground wire from the engine ground wire to the alternator bracket and installed another strap to the transmission case. I never had starting problems on that car, and the starter turned over the 10.5-1 compression 351 engine at over 250 rpm, it always started with just a flick of the switch.
On Vehicles that have a subframe or full frame, you want to run a ground strap from the steel body to the (sub)frame as well.
When you connect grounds to structure such as the frame, or sheetmetal chassis, you need have metal to metal contact, after removing the paint, wire brush then clean the metal with a fast drying solvent such as Lacquer thinner or Alcohol, and immediately wipe with a clean dry rag to wipe off any residue. Keep cleaning in this manner until no residue shows on the clean dry rag. Don't forget to clean the cable connectors too. You want the ground lug directly on the sheet metal, no washers under the lug. After torqueing down the ground wires, it's a good idea to hand brush some primer around the bare metal to prevent corrosion.
My thoughts about the Grounding kit's on e-bay? I'm sure you get a better ground by adding one of those kits, but I wouldn't use it, for one thing, they come with an aluminum battery connection (no good) and they don't tell what the wire guage is, most of the brackets shown look like plated stamped sheet steel (also no good). On a system like that the battery connector should be made of lead copper or brass, the leads need to be at least #4 guage copper wire, the common ground plate needs to be at least 1/8" or #10 guage copper plate. You can do the same thing with just a few straps from one part to another, and you'll get a better connection that way with shorter wires.
As Scott explained, make sure the chassis, frame etc are connected with heavy braid or the like.
edit;
OK sorry, I thought you asked about MS grounding. But the concept is still valid.
The reason that grounding is important, is that there are low current signals (signals like the temperature sensor) and high currents like the injector going from MS to ground. Regardless of how thick the wires are the high currents will put a voltage on the wire going from MS to ground. Thicker wires will put a lower voltage on the ground wire. This 'ground current' and voltage from the high current devices will be superimposed on the voltage signals from the sensors (temp, TPS etc) resulting in an error.
In addition to what Scott suggested above you can avoid much of this problem by separating grounds for the signal (temp sensor, TBS) and high current devices (injector, coil drive, etc).
1. Run a #16 wire from pin 8,9,10,11 to one point on the chassis. #16 is good, anything larger will be difficult to use on the connector.
2. Run all the grounds from the sensors (TPS, Temperature, O2 output - not the heater) together at some convenient 'common' point in building the wiring. Run this common point to pin 19 of MS but not to the car chassis) It will be connected to the car chassis internally by MS.
3. Connect power device grounds like O2 heater, relay, fuel pump, etc to the nearest chassis ground point.
edit;
OK sorry, I thought you asked about MS grounding. But the concept is still valid.
The reason that grounding is important, is that there are low current signals (signals like the temperature sensor) and high currents like the injector going from MS to ground. Regardless of how thick the wires are the high currents will put a voltage on the wire going from MS to ground. Thicker wires will put a lower voltage on the ground wire. This 'ground current' and voltage from the high current devices will be superimposed on the voltage signals from the sensors (temp, TPS etc) resulting in an error.
In addition to what Scott suggested above you can avoid much of this problem by separating grounds for the signal (temp sensor, TBS) and high current devices (injector, coil drive, etc).
1. Run a #16 wire from pin 8,9,10,11 to one point on the chassis. #16 is good, anything larger will be difficult to use on the connector.
2. Run all the grounds from the sensors (TPS, Temperature, O2 output - not the heater) together at some convenient 'common' point in building the wiring. Run this common point to pin 19 of MS but not to the car chassis) It will be connected to the car chassis internally by MS.
3. Connect power device grounds like O2 heater, relay, fuel pump, etc to the nearest chassis ground point.