hi,

i was wondering if theirs anyway to calibrate the factory tachometer, mines off by about 500rpm. or if you need to just replace it with an accurate factory unit

 

Karack recently mentioned that he found the tach to be off- by about 500 rpm- as well.
I'm not aware of a way to calibrate it but do wonder what real difference it makes?

 

Depending on what engine speed it's off at you might be in spec..
Look at the table on page 15-29 of the FSM [S4]

As for calibrating... I've never heard of a procedure to calibrate it. The FSM just says to replace :/

 

I wish we could calibrate it. I really don't want to get a tach gauge. Might as well redo the whole cluster with aftermarket gauges then.

 

I guess im not doing bad, my tach is only being off 200rpm at redline(s5 na)

 

What are you comparing it to?

 

i have stg2 rtek, so I am watching it live with the palm pilot.

 

500rpm is a lot

Is it off a lot more at high rpm then at low rpm?

Mines is 100-50 rpm off at low rpm, but once it gets to like 4k+rpm, it gets to be atleast 300-400 rpm off....

 

And that is a reliable tach source? That's debatable. The commander to my Power FC is off ~200 RPMs from the stock tachometer... My boost and vacuum readings are off, too.

 

LOL mine is off by 1200rpm! i have microtech ecu with handset, im planning to install a rev light shifter so i dont have to look at my gauge

 

1,200?! Damn... Seems like a bit much.

 

Wait.. Are you saying that the Commander is or isn't a reliable source? I'd assume it to be accurate [as I assume my SAFC is as well].

I have to admit my ignorance here.. Does the ECU send a signal to fire the coils or does it simply get a report that they have fired? [I've always assumed the former..]

 

more at high rps, its off about 200-150 at idle

comparing it to the display on my neo afc

 

There are 2 variable resistors at the backside of the tachometer. I know the bigger one is for setting the range of the tachometer. If you turn it anti clockwhise the tachometer range will increase which means you will for example hit the rev limiter while the tachometer only is showing 6000 rpm.

I guess the smaller resistor is for setting the lower range but I never tested it.

I had a S5 tachometer for a while because my original S4 one was damaged. I had to change a part on the PCB and resolder everything. The S5 tachometer was showing much too low rpms when idling because I still was using the S4 needle which is a bit longer and thereby heavier. I think I could have adjusted that by turning the small resistor because all the electronic parts on the PCB were exactly the same as on the S4 PCB but as I said i never tried it because it only took 2 days to repair the S4 tachometer.

 

so i just need to adjust them counterclockwise a touch i think, i'm guessing that they both work in the same manner so to adjust the entire range down i'll adjust them both an identical amount