I asked in LT1 tech but no one was sure.

1. How do i check the amount of spark at the end of the plug wire? What should it be?

2. Does the length of a spark plug wire matter and if i used 10mm wires would i loos or gain any spark performance?

 

The only thing the wires provide to the circuit is a small resistance. Quality spiral wound wires are going to be under 200ohms/ft. I think MSD claims 40-50ohms/ft. And resistance will obviously vary with length. That's about the only thing you can measure at the wires, and at the voltage you need to jump the gap in the plug, the wire resistance isn't a major factor when its that low. The voltage developed is primarily dependant on the plug gap.


The resistance is so low, that the length, within reason, isn't a major factor. And 10mm wire is no larger that 6mm wire... just the insulation is thicker. A 10.6mm Taylor 409 is simply an 8mm wire with an extra insulation jacket on it.

[EDIT]
OK... checked you other post... you indicated you put the wire in a tester and the wire started to "arch" at 2.5KV. That would indicate the insulation is breaking down. You might be needing 30-40KV to fire the plugs, so you need insulation that won't allow arcing at 2.5KV. I would expect the typical healthy insulation is good for 60-100KV.

 

So if i where to pull a plug wire put a new plug on it an leave it out of the car but hooked up to the opti as long as i dont see any missfires the wire is "ok"



Thanks for the response man i have been racking my brain all week try to test theys damn wires

 

No, it takes significantly more power to fire a spark plug in a running engine, and that number goes up as the pressure in that engine goes up.

FWIW, for everything within reason even stock plug wires work fine… what are you trying to figure out?

 

Well i have low power at take off...I cant even cherp the tires from a stop. Last year i could kill them off the line but over the winter it started loosing power. So i have done the following

Jet Hot Headers
New Plugs X2 had bosh now have AC-delco and Wires-last week new wires (OVC) i had 2 burnt wires.

New Coil X2 (now have the MSD Coil)

New fuel pump was put in in March (Fuel Presure is now 37-40 at idel 40-45 at WOT.

new MAS and new IAT (Mabe its time for a new filter

)

I checked visualy for a vacum leak didnt see any

EGR & Air Pump removed (EGR block off plate in place)

I just keep thinking its ignition but as i swich wires i still see no improvement

The car is a 97 Formula A4 with Gear code GU2 2:73 gears

Next step for me is to buy Auto-Tap and learn how to use that to see what is going on.


ANY HELP WOULD BE WELCOME! THANKS FOR TAKING YOUR TIME!

 

Well, ignition problems generally show up first as a mis at high rpm, and if really bad sometimes as a rough, missing idle. Since you haven’t described that I doubt that that’s the place that you should be looking.

Without more info (like scan tool info), to me a soft low end is usually a sign of too much fuel, too little advance or a badly matched combination. Since you don’t list any serious changes to the car I don’t really think that it’s the combination. That leaves you looking for something that could cause it to deliver too much fuel, high fuel pressure, leaking regulator, exhaust leaks in front of the O2 sensors…, and timing wise, the only thing that would cause that kind of problem is if you had something rattling against the block or frame setting off the KS.

Of course, this is somewhat akin to me shooting in the dark, blindfolded and drunk…

 

Thanks alot for your help!

My Y-Pipe does rattle agenst the frame sometime, but not at idel Just when i hit the gas hard. And my Number 1 primary tube on the LT's is leaking a little bit (would that cause a big diffrence? )

I am going to go ahead and buy a scan tool...is auto-tap about the best for the $?


is there any thing i can do to check knock or bad o2 readings

Can i unplug the o2s or KM?

 

a header leak or a leaking fpr (end up causing the same effect for different reasons) are the top of my list of what to look for, so sure, the leaking primary is just the kind of thing that I'm talking about.

power loss from KS issues is very distinctive feeling if you have a sensitive butt-o-meter. It feels like someone mashed the pedal and then let go some (ecm retards the timing 4* at a time, making a fair difference in power).

exhaust leaks are often easy enough to spot by getting someone to block off the tailpipes and you'll see and hear where it's comming out.

Mixture issues should show up on the plugs.