ssdungeon

iTrader: (24)

Is there a sensor that could be bad? I assumed the ECM did all the signal work for this but here goes.

I have the car riding well idling well....
I have 4.10 gears, and 19" C6 wheels on the rear. No matter what I do on HPT pro I cant get the tach right nor the speedometer right.

I have it where the tach is about 400rpms too low and the speedo is about 6 mph off depending on the speed.

Does anyone know what to plug in the speedo section to just fix this?

when I did the tire/gear I got 6.29 on HPT forums someone gave me some values a while back and they didnt get me there either.

This for the 98 Z in my sig.

soundengineer

iTrader: (16)

need to know actual tire diameter in inches...
or need to know size written on sidewall

example: 285/35/19
285/25.4 = 11.22047244
30% of 11.22047244 = 3.366141732
*2 + rim size = 25.73228346

tire/gear = 6.276

you may have something else wrong on the file...
did the other stuff get changed as well

Might want to compare to a stock file...copy in the Speedo stuff to get a stock setup to start with, then do the tire/gear change values again...

you should also see in the general tab, the VSS Pulses per mile will change and the trans/revolutions per mile will change

so will some trans shift point values...but that wont matter for your manual transmission...

also, make sure your Tach output resolution settings are both set to 6(stock values)

ssdungeon

iTrader: (24)

Thanks Scott I remember coming up with 6.29 and thats whats plugged in there now.
tire size is 295/35/19
What else could be wrong?
The tach outputs are 6 for sure. I tried this on a stock file but I can definately try it again wiht the 6.276 on a stock file.

Thanks,
And mainly thanks for the formula.

flame

iTrader: (13)

The stock gauge clusters are not the most accurate. Mine is off 150rpm at idle and speedo is off compared to the gps usually by a few.

2xLS1

iTrader: (25)

Use 6.38.

ssdungeon

iTrader: (24)

Yea I know I remember in the SS it was off quite a bit but usually only when I was at WOT or past 5000 RPMs but this is off cruising through a parking lot.
6.38 is off very little at low speeds/rpms but as I go faster it gets further and further off. At 40 on HPT its showing 49 on the dash. The pics show where its set now. I can't find any 98s in the tune repository with 4.10s and 19" wheels.

Anything else ill try and thanks for the help guys.

2xLS1

iTrader: (25)

You should be comparing what the scanner is showing for MPH against a GPS, not the cluster. That will indicate the accuracy of the calibration.

soundengineer

iTrader: (16)

I agree... you could have a cluster with issues.....
if HP Tuners closely matches a GPS...then you will know for certain.

ssdungeon

iTrader: (24)

I figured HPT would be the one that was correct.

I hooked up my TomTom yesterday but havent turned it on. I will take a little spin down the road.

Thanks for the idea.

ssdungeon

iTrader: (24)

HPtuners is staying with the GPS or within 1mph to be exact. My dash is the only thing off by 9mph.

Any suggestions?

soundengineer

iTrader: (16)

replace the cluster with a new one or one that is known to work correctly...
or go to an aftermarket setup with Autometer gauges and senders...

ssdungeon

iTrader: (24)

Should I be looking for a cluster for a 98 or will any from 98-2002 work?

ssdungeon

iTrader: (24)

Never mind I just found the answer I have to get a 98 one. Thanks fellas

soundengineer

iTrader: (16)

needs to be a 98....
99 and newer use a digital cluster signal...

98 uses all analog signals(which is why I recommended a bunch of aftermarket gauges possibly...)