Author Topic: M3 tach swap advice (Read 4073 times)

robrez · « **on:** May 14, 2010, 01:34:48 AM »

I bought an m3 tach. I was planning on keeping my original tach and just swapping my gas economy gauge for the M3 tach's oil temp gauge. Now I'm wondering if I should use the m3 tach too?

I have a MarkD chip, which raises the redline to 7100, but is the m3 tach's upper rev end realistic? Would I need to re-calibrate it too?

Not mine below, but the same, minus the red needles.

DesktopDave · « **Reply #1 on:** May 15, 2010, 08:29:16 AM »

I believe that the mechanics of the gauges are identical, so if a different scale of numbers is used on the faceplate you'd have to match the chip to the cluster. FWIW, the original cluster isn't all that accurate.

I'd just swap it out and keep mental notes on what was what. It's a larger scale so you'd be about 10% optimistic on the upper end of the rev range. Better than being down 10%! Programming that cluster chip to change the needle sweep ratio is probably pretty easy but I've never found a good write-up on it.

colin86325 · « **Reply #2 on:** May 16, 2010, 01:45:14 AM »

I think you will be ok.

Usually the concerns are from converting between 6- and 4-cylinders.

robrez · « **Reply #3 on:** May 18, 2010, 11:45:16 PM »

Thanks for the help. I picked up a euro 240 km/h speedo to go along with the 8k tach. Too bad I couldn't find a euro m3 speedo.

Uber E30 · « **Reply #4 on:** May 25, 2010, 07:11:26 PM »

The tach is ran by the coding plug. If you swap that tach into your current cluster then 8k will be 7k in reality. If this bothers you, you can simply put the face plate from your current tach over the 8k face and have an accurate reading. Who really looks at those anyway? I just go by sound.

KenC · « **Reply #5 on:** June 20, 2010, 06:53:44 PM »

Bump.

I'm wanting to install one of these as well. I have a MarkD chip so the redline is now 7100rpms. I'd like an accurate tach to reflect this.

Any ideas about the coding plug?

jscribble · « **Reply #6 on:** June 20, 2010, 08:36:38 PM »

Seconded. I would also like to know more on this. Just did a chip swap and was hoping that I could swap in an m3 tach, or recalibrate mine for a new face. I recall reading about a lag with the factory tach, but does anyone know how bad it really is?

318/6 · « **Reply #7 on:** March 25, 2012, 03:06:55 PM »

I swapped an M3 8k tach card and M3 coding plug (p/n ending in 699) in my 318is, simple plug and play. Tach reading is correct all the way to 7200.