This is to focus on one aspect of an earlier thread. I would like those with knowledge of this phenomenon to share their opinions here..

A ground loop is apprently noise created by the difference in resistance between two different paths to ground. So if you have one device sent to ground through two different paths, you get a resonance set up between the two different paths. Am I right about this? So does this mean that it is best to ground a sensor in only one place?

If there is a wire to ground in the harness, and I want to make sure that the ground is really solid, and don;t trust the harness wire completely, is it best to simply cut the harness wire out, and run a seperate wire for this ground, or is it OK to run a second, parallel wire to ground? Would this potential ground loop noise effect the readings on the MAP, TPS, IAT or ECT? Are these dvices noise sensative? Is this problem of noise here more of a concern than losing the ground al together?

This falls into the catagory of underlying principals that I have been mentioning in the past. It seems as if good basic electronics practices are a key to successful EFI. What are your thoughts? I feel like I am moving a snail's pace here, but I think some of my earlier problems stemmed from moving too fast, and perhaps not understanding entirely how small things effect the final result. Thanks in advance for any information or opinions.

Sam

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All those sensors are measuring resistances or voltages at very low frequency, and all your noise should be at high frequencies (like radio), so noise in unlikely to screw up those measurements.

The main thing I could see a ground loop affecting is the spark measurement by the ECU. You can see if that is happening by look at RPM the ECU is measuring and comparing to your tach. If they match up, you're fine.

Lou

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Home of Slant6-powered fun machines since 1988

So an insurance ground on these would not be a potential source or error or instability? Thanks for you input here. One of these evenings when it is not too cold in the garage I will get out there and fix a couple of little things that have been holding me back for awhile.

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If you are worried, I would run all grounds back to the ECU, or if they are 1-wire sensors, they ground to the spot they are screwed into. I haven't paid much attention to this so far. There is no need for two grounds, esp if you ground back to the ECU.

My opinion is that tuning is the major hurdle now, although I haven't seen your setup yet! Is the datalogging going well?

Lou

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Home of Slant6-powered fun machines since 1988

I have data logged, but have just scratched the surfaces of this. I can data log 6 variables, and the first couple of sessions I realized afterwards that I could have chosen better feed backs to monitor. Consequently I got some info but not as useful as it could be. Two weeks ago the TPS stopped reading reliably, and the weather turned bad. The car has just been sitting since. I am trying to get worked out in my head how to approach some of the possible deficiencies created by rushed, or uneducated installation on my part. It is running pretty well now, but I think I can not get the cold start problems worked out until I get the TPS working right, and the Accel software that permits me to change some of the default settings. The main one I think I need to fiddle with is the after start enrichment decay.

I think my biggest mistake was wrapping up the harness before getting the car running. I had such confidence that it was all going to work, and then when it did not, the wrapped up harness made it very, very difficult to trouble shoot. So, all you guys thinking about this, don't be so over condfident of your soldering and wiring skills that you make the same mistake. It may not look so cool, but leave the wires spread out for test purposes until you get it running. I may post this in a seperate thread just as I did about the MAP sensor.

I am happy to take my time here. I kind of OD'd on this car the previous 9 months, and it is fine to be just thinking about it, and planning. Thanks for your inquiries, and your advice.
Sam

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I guess if I had to pick just 6 things to datalog on your car, they would be:

MAP
EGO (O2 sensor)
TPS
RPM
Ignition advance
MAT

You should also be able to datalog things like pulse width, accel enrichment, duty cycle, and coolant T.

Lou

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Home of Slant6-powered fun machines since 1988