tach and speedo mod questions.....

Topic: tach and speedo mod questions..... (Read 1563 times) previous topic - next topic

tach and speedo mod questions.....

April 02, 2005, 12:21:57 AM

i didnt want to put this in the new thread reguarding new cluster faces. basically i just have a few questions reguarding the tack mod and the speedo mod. i have both my original sport cluster as well as an 87 turbo coupe cluster appart at the moment.

first off, how much accuracy do you sacrafice for the 140mph mod?

secondly, im okay with using my sports tach. i did notice however that i can use the turbo coupe tach with the "V8" mod for use with a V8. from what i understand, when you do the mod you are basically making the 4cyl tach into a V8 tach as far as the needle is concerned. but when i hold the turbo coupe tach and the sport tach next to each other the gradients are different. it the moded tcoupe tach accurate with the v8 mod? or can i print up a new 7k face for the sports tach? im a little confused on this. basically, id like a 7k tach but ill keep the sports if it will be more accurate. i still want to print up a face to match the 140 speedo..

anybody have any advice input or sujjestions.

also does anyone have any extra capacitors for the 140mod...id rather not have to buy 10 of them.

how does the face look if you sand the black down to the green and post the new "bumper sticker" face over that...i havnt seen any pics...

thanks guys....john

Re: tach and speedo mod questions.....

Reply #1 – April 02, 2005, 01:37:56 AM

Yea the sweep is different between the two tachs... The TC tach with the mod is still a 7K tach, but due to a different value resistor in the Sport unit it's just a 6K. Other than the face and resistor, both tachs are identical. I've compaired the accuracy of the Sport tach and the modified TC and they were very close. Note.... its common for either tach to be off 300-400 rpm, so slightly juggling the resistor value will get some degree of accuracy.

Since I already have a 140 speedo, I didn't really get involved with derermining the accuracy that mod. But one of the techies over on NATO did some extensive testing and said Joes mod was accurate.

Re: tach and speedo mod questions.....

Reply #2 – April 02, 2005, 02:15:17 AM

so the sweep is different but the tcoupe 7k tach uses the same resistor as the sports tack for the mod. in otherwords, can i print up the 7krpm face and put it on the tcoupe tach, and take the resistor in question out of my sports tach and replace the one in the tcoupe tach with that one?..hope you could follow that...lol

Re: tach and speedo mod questions.....

Reply #3 – April 02, 2005, 02:26:10 AM

Quote from: shame302

so the sweep is different but the tcoupe 7k tach uses the same resistor as the sports tack for the mod. in otherwords, can i print up the 7krpm face and put it on the tcoupe tach, and take the resistor in question out of my sports tach and replace the one in the tcoupe tach with that one?..hope you could follow that...lol

NOPE... The value of the resistor in the Sport tach is different than the modified TC tach.. If you use the resistor from the Sport tach, you'll have a 8cyl, 6K TC tach(with the 7K face) that ain't accurate at all.

Re: tach and speedo mod questions.....

Reply #4 – April 02, 2005, 03:07:40 AM

gotcha..thanks. i somehow thought that the resister you put in the turbo tach was the same as the one in the V8 tach...makes much more sense now. thanks again....john