im doing a ls3 swap and wondering if this box will enable me to use my stock tachometer(i plan on sticky with the stock guage)

http://www.summitracing.com/parts/ATM-9117/

autometer pn 9117

at almost $80, is there a better or cheaper way?

also from what i understand umust cut in the the ls3 harness, so it raises another question is there a cheaper and other resort i dont have to cut into the ls3's harness?

ive seen pocket is a veteran in the wiring department but anyones is more than welcome to chime in

thanks justin

 

You shouldn't have to buy a box for it. There should be a tach output from the PCM, which you just tie into the tach signal.

You will have to reprogram the PCM for the tach output. LS3 is the 58-tooth crank sensor, if memory serves.

Unless LS3 is so vastly different from LS1 that the PCM doesn't have a tach output - which I doubt.

 

Alan with a ls3 told me something about a resistor that I should be able to purchase from radio shack for around $5 but I'm still a lil confused

So just tie the tach signal into ecu?

 

from what I understand the ls3 put out a 4 cly out even though it a v8 that coming from the guy at auto meter

 

LS1 PCMs can be reconfigured via LS1Edit/HPT/EFILive to output a V8 signal which works fine with factory tachs in my experience. No extra hardware required.

 

I've heard of using a resistor for "bump-up voltage" to the tach signal to run a factory tach, but even that doesn't seem to be required every time.

 

Camaros dont need the booster, only firebirds

 

Actually with the E67 ECM that you are using from GMPP it is a good idea to use the pull up resistor, otherwise you are going to have a floating voltage as it switches that may cause erratic signal...

I think i sent you the schematic i used previously, if not it is in my post on LS3 engine swap

You will need to reprogram the ECM to have it correctly drive the gauge... this can be done with HP Tuners for example

You will want to set the following parameters
- Tach Type = Crank
- Resolution High = 7
- Resolution Low = 7

The last two are the pulse divisions that changes it to be equivalent to a 8 cylinder signal