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If I cut and resplice the fuel injector wires will it chonge the resistance of the electricity that flows to Ohm specific injectors? I want to find out before I do it with this engine swap I'm doing this weekend('02 spi into '91 pony). I'm only concerned because I read somewhere that if you "crimp" a wire TOO tight it can create resistance. Thanks for any help.
 

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Physics man to the rescue!

YES, IT WILL AFFECT THE RESISTANCE.

And once again, here's the math to prove it:



And here are the resistivity (rho) tables:

http://hyperphysics.phy-astr.gsu.edu/hb ... iv.html#c1

Note that the rho tables are for solid coper. To find the new resistivity, it's the sum of the numbers of individual wires that make up the gauge. The math gets a little tedious.

Also, note that is is of relatively pure copper. Solder has its own resistivity that has to be taken into account. Here is an article on how solder affects resistivity:

http://www.microjoining.com/microTip_Solder&Flux.pdf

Make sure you solder your connections. Soldered connections are significantly lower resistance and less prone to corrosion than crimped conenctions. Crimped connections make me cringe.

For all intents an purposes, a well-soldered connection will be just about as good as stock wiring. Make sure to use shrink wrap and flux.
 

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Yeah the resistance will change a little but it's not enough to throw things out of whack.
 

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Yeah, siragan is right. It's all about cross-sectional area of the conductor, assuming you're not splicing in 1970's aluminum wiring or something retarded. Crimping can affect resistance, because by crimping, you can actually sever right through some of the strands. I solder everything I see (people who use marettes are just plain lazy) and use heat-shrink tubing over-top.
 

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rho is a dumb Greek letter that only engineering geeks like siragan even claim to have heard of. It can represent things like density or resistivity, as above.

alpha, beta, gamma, omega, rho, theta. I think the Greeks only had six letters or something. Anybody who comes on here and recites the whole Greek alphabet gets shot.
 

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Sorry this is gonna be long and I know how you feel about that lately :lol:
I can't disagree with Sirigan, and I do solder everything in the car that I think matters, but...
I am an electrician and I was never in all my schooling taught the word resistivity.
We routinely crimp lugs onto wires of all sizes right up to 1000MCM, with a big hydraulic hand pump crimper. This then gets bolted to a bus bar. What other way do you propose it is done?
All big connections get infra red inspected and there aren't any hot spots.
Joints on wires up to say #8 are done with Marrettes.
Of course that's different, soldering is never done in the trade, but it illustrates crimping is OK.
If a crimped butt connector on two #16 or 18 wires squeezes the wire, and theoretically the diameter is now smaller, if it's enough to reduce the voltage at the end, then the crimped area must be consuming power and it would be warm or hot. I don't know exactly what the power consumption on your application is, but in normal circuits in a car, there's still the full voltage at the other end and the crimp is cool as a clam. The reason is the butt connector is made of metal and that metal is like part of the wire as far as the electrons are concerned, so the diameter isn't reduced at all. That's why the big 1000MCM crimp is still cool. I bet if you do a test with an ohm meter you'd find the resistance of the wire butt connector crimped together would still have a resistance of zero ohms. Even if you can't count the metal of the connector and you had to consider the wire smaller, It would only be an issue if the voltage were high and/or the current draw were higher than that smaller diameter can handle, but you would get a melted wire rather than a voltage drop. I don't think they'd make those things if every single one of the hundreds of millions used made a hot spot. Besides, what do yo do when you need a spade terminal put under a screw, as in an amplifier? how do you avoid crimping?
Marrettes don't belong in cars, but they never cause any voltage drop, plain and simple. I don't see it as lazy either. You twist say 3 #12s together and twist on the connector. A thing of beauty. BTW I hate Marrettes. I use Marrette XTP or Ideal wire nuts. they are nylon and have a square cross section spring to really grip the wires.
Remember that any other metal the electrons touch they consider part of the conductor. You could just hold two wires touching and they wouldn't even know it's not one continuous wire.
 

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Yikes Brad, that's a lot of reading for a lazy guy like me.

Resistivity is a property of the conductor, like density is a property of water. It differs from metal to metal (as density differs from liquid to liquid) and is a function of temperature. Resistivity has units of Ohm*m or Ohm*cm.

Yeah, marettes don't belong in cars, but sometimes when I see them in certain applications, I just think "lazy".

You're right...crimping with large cables is done (I see it at work in 13.8 kV, 4.16 kV, 600 V, 120 V and even DC applications) and sometimes there's aren't reasonable alternatives. In the car, I see no reason why soldering can't be done on almost every wire where a joint is needed.

Crimping that damages wires wouldn't result in a voltage drop (unless you sever all the wires), but may cause too much resistance to current flow if the connectivity of some of the strands is lost by them being broken.

This feels too much like school or something. I'm not gonna post on this thread again.
 

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highanddry said:
Resistivity is a property of the conductor, like density is a property of water. It differs from metal to metal (as density differs from liquid to liquid) and is a function of temperature. Resistivity has units of Ohm*m or Ohm*cm..
You mean it's the inverse of conductivity. Sure I'm familiar with resistance per unit length, just not the word for it, since it is only classroom electricity. Line loss is measured in volts, and we use the next size up wire for longer runs.
highanddry said:
Crimping that damages wires wouldn't result in a voltage drop (unless you sever all the wires), but may cause too much resistance to current flow if the connectivity of some of the strands is lost by them being broken.
That's what I'm talking about. And it's not really the strands, it's just the resulting reduction in diameter, cuz I'm thinking of solid wires(also not in a car) A properly done crimp won't do that. Maybe it's just guys who don't know what they're doing that get a rotten crimp. Maybe they don't use the right tool. Like I said, there should be no resistance. That would be really bad and CSA wouldn't let them make those connectors. The car anyway is full of crimps. Every wire in a connector or socket or back of fuse panel is crimped to a pin in that connector, then they rely on the pins touching to get a completed circuit. There must be hundreds of crimps in a car.
Don't worry I always solder, like a wiring adapter to the new HU's harness, etc.
 

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as soon as you make a barier in any wire it makes resitance. just make sure you dont cut the CKP wire and try and splice it.. it wont work.

aaron, get MS!!!
 

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drivinonthinice said:
Yeah the resistance will change a little but it's not enough to throw things out of whack.
do uremember when my car was down for 3 months and i eventually had to get the complete new wiring harness???

DIAGNOSIS: SPLICED WIRES
 

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a good way for all you genious men to figure this out is take some wire cut it crimp it then take a DVOM and see if there is any resistance :)

i could be wrong im only 18 but seems logical to me.
 

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FordBoy4ever said:
a good way for all you genious men to figure this out is take some wire cut it crimp it then take a DVOM and see if there is any resistance :)

i could be wrong im only 18 but seems logical to me.
I already said that.
 

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first of all... why did you cut the injector plugs? theonly thing on the 1.9 harness you need to splice is a few extra inches on the tps plug, since you have to use the spi plug.
 
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