[PA_Z06]

The tach circuit, circuit number 121. Is where the tach in our cars get its tach signal. My question is.. Can I tap into this circuit with an RPM activated switch or a window switch with no ill effects to anything else in the car ?

Any insight would be greatly appreciated.

Mark

 

[Guest]

If you need to install a RPM shift light such as an Autometer 5340 in a C5, I recently installed the one I had on my ZR-1.
You need to splice into pin 10 off the red PCM connector, which is a white wire, and also make sure that the shift light is setup for a four cylinder ignition to operate properly.

The issue is that the "tach output" off the computer on the '98+ LS1 motor is the
same as that of a four cylinder ignition (2 pulses per crank rev).
Making this cylinder selection adjustment has made the light work, and no ill effects should be seen.

This now gives you a way to set when the shift light comes on as to what RPM module you plug into the shift light unit.
This is great for when doing drag racing and you want to shift every time at the same RPM.

 

[PA_Z06]

teamzr1,

Thanks for the info. That's the pin I thought I would use. The only difference is I'm going to use pin A17 on the IPC Cluster Plug. Pin 10 on the UPC and pin A17 on the IPC are both part of circuit 121. That way I don't have to look for a place to come through the fire wall and its a much shorter run. I also can pick up a ign. 12 volt source and a ground.
I did not know about the 4 cyl. setting.
Thanx a bunch.

Mark

 

[mgarfias]

You might have to send your tach into to be readjusted though. The vette uses a 4.8v signal, and most of the tachs are setup to be 5v-11v (or something similar).

(er your aftermarket tach)

 

[PA_Z06]

mgarfias,

Thanks for the additional info. I'm not going with an after market tach. I'm making a shift light that suction cup mounts to the windshield and a quick disconnect harness so I can easily take it in and out of the car as needed. This will be controlled by a MSD RPM switch.

 

[KellyZ06]

PA-Z06
I would be VERY interested in pictures of the install as you go along. If that's to much trouble, maybe you could post a picture of the final install along with the name, model number and settings for your shift lite. I don't need a HUD but would love a highly visible shift lite

Thanks

 

[Guest]

I don't need a HUD but would love a highly visible shift lite

Thanks

Autometer makes the 5340 RPM shift light.
The light is quite large and bright so it can be seen real easy in sunlight.
It allows via plugin modules to set the RPM level as to when the light should come on.

Either the PCM is slow in reporting present RPMs or my '99 has too much power for by the time the shift light comes on and I go to shift, the rev limiter is already kicking in and that is set at 6500 and light is triggered at 6200.

 

[KellyZ06]

Thanks for the info. I guess the only way around the lite being slow is to lower the trigger point until you get it where you want it? Where are you placing it? I saw a post by the Zaino distributor and he put it in the center vent, which is really great, but way to much work for me

 

[Guest]

On 2001-06-30 21:48, KellyZ06 spewed forth this drivel:
Thanks for the info. I guess the only way around the lite being slow is to lower the trigger point until you get it where you want it? Where are you placing it? I saw a post by the Zaino distributor and he put it in the center vent, which is really great, but way to much work for me

I've set the light to trigger at 6200 RPMs and rev limiter at 6500 srill trips.
Will experiment again 4th of July at an all day drags at Sears Point raceway.

I am into racing and not into looks thus I think something you want to look at should keep yours eyes looking forward so I use double sided velctp and light is so light in weight it is held with the velcro right on top of the dash.
There is plenty of airspace between door hinges and thus you can bring the wiring in without hacking up firewall.