ok heres the deal -
i swapped an s13 sr20det red top in to my 98. ever sense then my rpm's wont read correctly on the dash. i hooked up my afc and a have a GUS guage from stewart warner and they are correct.

what happends is this. at idle the tach is correct as i excelerate the needlese moves faster. when i am doing 2900 rpm it says i am doing 3000 and when i get up to 6500 on the tach im only doing 5750. so now my red line is all off and it sucks when i am trying to shift properly. any suggestions anyone?

Jay

 

You will know your car better than i do but they say factory tachs can be off by a lot in the higher range.....
I also read an article that tested 10 diff brands of tachs and there was as much as 1500 rpms diff between them.... so some cheaper brands may just not be as accurate.
Could just be the tach......

 

possible, but my red line its at 6500...i cant let the needle get to almost 8000 if im not mistaking

 

Do you have an aftermarket tach or the indash one?

 

both...my in dash one is whats reading wrong. the aftermarket one and my afc are reading the same, well when the afc worked.