Modding turbo tach for v6

Topic: Modding turbo tach for v6 (Read 1442 times) previous topic - next topic

Modding turbo tach for v6

February 06, 2006, 07:56:40 PM

Ok now I've got the proper resistance and it still doesn't work. I've added a 330k resistor parallel to the 100k on there. That gives me 75k wich erics site says should work for a v6. Well heres what it does. The tach never reads below 1500rpm even with the car warmed up and you can tell its idling around 700. And when I take it out for a drive it doesn't climb as fast as the engine does and then all of a sudden it shoots up to 4000. But wont go about 5000. And I know I was running that thing out to 6000 at least!:D So has anyone actually modded a turbo tach for a v6?

Modding turbo tach for v6

Reply #1 – February 06, 2006, 08:26:45 PM

You were running a 3.8 at 6 grand and didn't have to go back and pick up your crankshaft? :D

About the best idea I can come up with is to put a variable resistor (0-100k trimpot) and temporarily install a diagnostic tach (either a cheap aftermarket one or a timing light with tach display, etc). You could adjust the trimpot until you get it to read the same as the diagnostic tach

Modding turbo tach for v6

Reply #2 – February 06, 2006, 08:31:08 PM

And I just paid 13 bucks for a bag of 500 resistors to get 1. I've got a second tach, I'm going to mod it and see if it will be any better.

Modding turbo tach for v6

Reply #3 – February 07, 2006, 10:54:42 AM

Well the second tach reads about 500 rpm higher all the time than the first one. !!! WTF

Modding turbo tach for v6

Reply #4 – February 07, 2006, 12:00:12 PM

That's because you suck :D

I think you're gonna have to go with the trimpot on this. AFAIK the 75k resistor theory is only a theory (I don't know of anybody that's actually modded a tach for a V6). While logic would dictate that a 6-cyl value would be halfway between an 8 and a 4, this is only if the resistance variation value is linear. If the variation is on a curve it could be anywhere between 50 and 100k

Modding turbo tach for v6

Reply #5 – February 07, 2006, 12:32:28 PM

Is there not a "calibration" resistor in there as it is?

I'm not that familiar with the later tachs, but I know on some of the earlier Fox tachs there was an adjustable pot. resistor that they set and "lock" with a dab of paint.