where to pick up tach signal for dyno

[Don M]

We probed every dern wire under the hood today trying to find a place to pick up a tach signal to get the torque reading on the dyno. This is the second time the truck has been on the dyno and I have not gotten the torque readings yet.

Any ideas which wire it is? Location and color.



Don~

 

[gitchesum]

When we had our dyno session in Houston back in January, we were told by several sources that there is no kind of RPM pickup on the 12 valvers.



What kind of dyno are we talking about here? If it's a DynoJet, There is an accessory that you can purchase that will allow you to get the RPM's. If I remember, it cost about $400.



I wish someone could prove otherwise, that was I can get some true torque numbers myself.

 

[Don M]

Yeah it was a dynojet both times. Wish I could figure something out as well.

 

[illflem]

The tach wire is gray with light brown tracer under the dash on my '95s. I connected to it when I installed a remote starter so that you couldn't try to start a engine that's already running. Not sure if it will work in your application but it does send a pulse equal to engine rpm. The PCM needs to interpret the signal from the engine speed sensor before sending it to the tach, maybe that's why you had trouble finding the right wire under the hood, try under the dash.

 

[SLang]

I think there is a crank position sensor (gasser terms) on the front of the engine. This is how the tach is operated. I'll check to see wire color/exact loaction tonight. My trucks @ home.



Also why do you need a tach for the torque? A dyno measures torque and uses the tach to calculate HP. HP can not be measure directly, it is a calculated figure.

 

[Don M]

SLang,





HUH? you sure you dont have that backwards?



Don~