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post #11 of 58 (permalink) Old 11-13-2006, 02:15 AM
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First, Cobra is correct. The circuit for the spark plugs uses the engine cylinder heads as part of the return path. The “ground” wire from the cylinder heads to the chassis is part of this circuit. If the return path is intact, then adding additional ground wires serves no purpose. This is easy to check. Using an ohmmeter, place one probe on the cylinder head and the other probe on the negative terminal of the battery. You should get a reading of less than 1 ohm (more likely 10ths of an ohm). If you get higher readings then there is indeed a problem.
Doesn't matter how low the stock resistance is, adding additional ground wires will lower it. In addition to the sparkplugs, the alternator is also grounded through the engine. The more resistance the ground path presents, the harder the alternator has to work and the more drag it places on the engine. As we all know, accessory drag can consume a few horsepower.

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post #12 of 58 (permalink) Old 11-13-2006, 02:37 AM
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doesn't everyone realize that you can take the same car and do 10 pulls on the dyno and get a different reading each time? just because you run one pull on a dyno and get one number...then slap on a "grounding kit" and do another pull on the dyno and get a different number....well, that doesn't exactly mean it was the "grounding kit" that changed the number.


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post #13 of 58 (permalink) Old 11-13-2006, 02:43 AM
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why not just get a hyper-voltage system instead? I noticed the most difference w/ that.


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post #14 of 58 (permalink) Old 11-13-2006, 02:53 AM
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doesn't everyone realize that you can take the same car and do 10 pulls on the dyno and get a different reading each time? just because you run one pull on a dyno and get one number...then slap on a "grounding kit" and do another pull on the dyno and get a different number....well, that doesn't exactly mean it was the "grounding kit" that changed the number.
I will acually agree with Dj on this one.

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post #15 of 58 (permalink) Old 11-13-2006, 03:05 AM
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Doesn't matter how low the stock resistance is, adding additional ground wires will lower it. In addition to the sparkplugs, the alternator is also grounded through the engine. The more resistance the ground path presents, the harder the alternator has to work and the more drag it places on the engine. As we all know, accessory drag can consume a few horsepower.
As I understand it, the power for the spark plugs runs from the battery, through a timing system (engine management controlled), to the spark plugs, and then back to the battery, with further grounds to the chassis, in case anything goes wrong. If this is the case, the only place you would see any real gain would be on the return line to the battery, not to the chassis, as the return line completes the circuit, thus lowering the resistance here increases the energy that can be released from the spark plug. So in this case, you want the lowest resistance possible only on the return line, as the others don't matter.

If I'm wrong, and the chassis completes the circuit back the the negative side of the battery, changing the ground wires may have some effect, as they'll make it easier for the charge to get to the chassis and back to the battery, but most of the resistance will be in the chassis, not the wires, so any gains will be minor.

If its a combination of both, the battery return is the best wire to replace, but again ground wires will have some (albeit very minor) effect.

As was suggested earlier, ground kits are easy to make. Go buy the lowest gauge, highest quality wire you can, that should have the lowest resistance. Buy some connectors and crimpers and make custom wiring that runs the shortest possible distance. Also be very cautious, at some point you're going to close a circuit, that may or may not have a significant amount of amperage (what kills you) running through it.

On the dyno issue, as David said, 5 hp is within the margin of error.

My personal (with some physics, but not alot of car knowledge) opinion, grounding kits are a piece of bling, while some kits (especially on poorly setup electrical systems) may yield a couple horses, they're mostly for a nice looking engine.

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post #16 of 58 (permalink) Old 11-13-2006, 01:28 PM
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As I understand it, the power for the spark plugs runs from the battery, through a timing system (engine management controlled), to the spark plugs, and then back to the battery, with further grounds to the chassis, in case anything goes wrong.
How do you think the electricity gets back to the battery? It goes from the plug, through the head, through the block, down the ground strap, through the chassis, up the battery to chassis ground wire. That's quite a bit of distance. Increasing the number of ground wire from the engine as well as changing the locations can help.

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On the dyno issue, as David said, 5 hp is within the margin of error.
On a car making 250whp, 5whp is NOT within the margin of error if your dyno operator knows what they're doing. 5whp is 2%. The margin of error on a Dynojet that is operating correctly is less than 1% or 2.5 whp on a 250 whp car. On my Tiburon, the margin of error would be 1.9 whp. I saw gains of 4 whp through the midrange and a peak increase of 3 whp. The after dyno never dropped below the before dyno. I ran 3 pulls before and 3 pulls after. The comparison was made between the best before dyno and the worst after dyno. If you averaged the runs, the gains were actually around 5 whp, not 4 whp. The runs were less than 30 minutes apart and the car was never unstrapped because how the car is strapped can effect readings.

Guys, I've been doing this for 18 years. I don't sell grounding kits. I gain nothing by lying to you.

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post #17 of 58 (permalink) Old 11-13-2006, 02:30 PM
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How do you think the electricity gets back to the battery? It goes from the plug, through the head, through the block, down the ground strap, through the chassis, up the battery to chassis ground wire. That's quite a bit of distance. Increasing the number of ground wire from the engine as well as changing the locations can help.
On a car making 250whp, 5whp is NOT within the margin of error if your dyno operator knows what they're doing. 5whp is 2%. The margin of error on a Dynojet that is operating correctly is less than 1% or 2.5 whp on a 250 whp car. On my Tiburon, the margin of error would be 1.9 whp. I saw gains of 4 whp through the midrange and a peak increase of 3 whp. The after dyno never dropped below the before dyno. I ran 3 pulls before and 3 pulls after. The comparison was made between the best before dyno and the worst after dyno. If you averaged the runs, the gains were actually around 5 whp, not 4 whp. The runs were less than 30 minutes apart and the car was never unstrapped because how the car is strapped can effect readings.

Guys, I've been doing this for 18 years. I don't sell grounding kits. I gain nothing by lying to you.
Ok, so I'm back for some actual physics know. This discussion is about resistance. The entire ingnition system can be explained relatively easily. Charge will build up on the tip of the spark plug until the charge creates a breakdown in the surrounding air, making it conductive, and resulting in a spark jumping across between the electrodes. This is a pretty significant amount of energy, with HowStuffworks.com putting it at anywhere between 40,000 and 100,000 volts of electricity. Now, the entire purpose of resistors is to create a voltage drop in a circuit, or taking a voltage at one level and making it a lower voltage. Now, the other aspect of resistance is the current being pulled through the circuit. Since a transformer is used to go from 12 v to 40,000v, we need to account for the change. This results in a current that is .0003 * the current coming from a 12 volt battery, a quick web search shows that Cold Cranking a car typically takes as much as 600 amps (although its doing more than just spark), so the voltage in the ignition system is roughly .24 amps. Now, lets assume that the chassis of the car was good for 1000 ohms (probably way high, as brass and steel are pretty good conductors), we see a drop of 240 volts across the chassis. This is .6% of the total voltage drawn through the system. Some of these numbers are off, as the calculation for current only included the 40,000 volt drop, but it is approximate, and made for a considerably easier problem (as I don't have a volt meter to measure a cars resistance w/ etc.) While they may have some effect, I truly doubt it would be noticable.

In response to the assumption that a dyno is accurate to 1%, I highly doubt that. I've had physics labs where we estimated the error in volt meters to be as high as 1%. A voltmeter is a simple device that relies of few variables. A dynamometer is far more complex. Furthermore, you can never really test your car twice the exact same way. Experimental controls would mean having two cars with identical engines (try gettin that at the showroom), in climate controlled booths, with only one thing different, and running the test. When doing dyno pulls, the first run may have heated the engine or the tires enough to see 5 hp gains the next time around, warm engine making it run better, warm tires making it stick better.

I hope that this information is helpful and accurate. If there are any mistakes, please send me a pm and I'll fix the mistake or address it in the thread.

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post #18 of 58 (permalink) Old 11-13-2006, 02:39 PM
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why not just get a hyper-voltage system instead? I noticed the most difference w/ that.

isn't that just a fancy name for a grounding kit???

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post #19 of 58 (permalink) Old 11-13-2006, 02:45 PM
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In response to the assumption that a dyno is accurate to 1%, I highly doubt that. I've had physics labs where we estimated the error in volt meters to be as high as 1%. A voltmeter is a simple device that relies of few variables. A dynamometer is far more complex. Furthermore, you can never really test your car twice the exact same way. Experimental controls would mean having two cars with identical engines (try gettin that at the showroom), in climate controlled booths, with only one thing different, and running the test. When doing dyno pulls, the first run may have heated the engine or the tires enough to see 5 hp gains the next time around, warm engine making it run better, warm tires making it stick better.
Dynojets are supposed to be calibrated on a regular basis. Most shops do adhere to the recommended schedule. If there are errors, they are recalibrated to within 1% of actual. As far as not testing the same two times, this is why you do at least 3 before and 3 after pulls. As I stated, I took the best before and worst after. I eliminated most of the variables by testing 30 minutes apart (no climatic changes) and by not unstrapping the car. Also, by making 3 pulls, the engine temp was normalized.

I really don't care if you believe me or not. I use grounding kits because I've seen that they work on several different cars. You don't want to use one, that's fine with me. Like I said, I don't sell 'em.

Aaron B.
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post #20 of 58 (permalink) Old 11-13-2006, 02:58 PM
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But Dynos can do nothing for the air environment. If you made the room cooler by 10 degrees you would see an improvement in dyno numbers with nothing else changing on the car. This would have NOTHING to do with the dyno being calibrated.

5 whp on a single run is not enough of a change unless you can see it across the board avg. of several runs.
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