tach is off

[runtwrestlin]

I just swapped a 98 LS1 into a 97 (formerly 3.8) camaro, and the tach is off. I tried using a 98 LS1 gauge cluster, but nothing worked properly on it (which didn't make sense to me because the pinouts for the 98 LS1 & 97 3.8 clusters are identical...). The gauges all work fine with the 3.8 V6 cluster, except for the tach gauge, which shows fewer RPM's than what I'm really at. Is there way that I can retain my V6 cluster and adjust the tach, or would a 97 V8 cluster work?

And yes, I posted on LS1tech as well, but I've gotten too many good answers from this board to not ask here too. Thanks

[runtwrestlin]

Re: tach is off

Well, i just found the answer. Might as well copy/paste the info to help out.

I did a search for this information and could not find it using keywords Tachomter and Tach.

I am looking into adjusting the tach output for my 98 VCM due to putting the motor into a 6 cylinder BMW. The stock setting for high & low resolution is 6. What is the proper adjustment to make the tach output the same as a 6 cylinder motor? I know the LSx output is seen as a 4 cylinder by tachometers. Nothing else on the car uses the tach output.

EDIT
Did some math & research & some more math, this looks to be correct:
The number of crankshaft medium resolution pulses (24x pulses) to hold the tach output high (should match {G1205} "Tach Pulses Low").
The number of output pulses P is calculated as P=24/(N*2) where N is the value of this calibration.

Sample values for this calibration:
For 12 pulses, use N= 1
For 6 pulses, use N= 2
For 4 pulses, use N= 3 (Note- 8 cylinder tach setting)
For 3 pulses, use N= 4 (Note- 6 cylinder tach setting)
For 2 pulses, use N= 6 (Note- LSx 8 cylinder & 4 cylinder tach setting)
For 1 pulse, use N=12

N=6 same as you see in HPT (for Gen 3 motors)

Pulse Calculator: V8 tach reads 4 pulses per revolution, so 24/8=3. 6 cylinder reads 3 pulses per revolution, so 24/6=4. 4 cylinder reads 2 pulses per revolution, so 24/12=2. These are the "N" numbers for above that are plugged into the HP Tuners Tach Output fields.

[bigbrian442]

Re: tach is off

I just swapped a 98 LS1 into a 97 (formerly 3.8) camaro, and the tach is off. I tried using a 98 LS1 gauge cluster, but nothing worked properly on it (which didn't make sense to me because the pinouts for the 98 LS1 & 97 3.8 clusters are identical...). The gauges all work fine with the 3.8 V6 cluster, except for the tach gauge, which shows fewer RPM's than what I'm really at. Is there way that I can retain my V6 cluster and adjust the tach, or would a 97 V8 cluster work?

And yes, I posted on LS1tech as well, but I've gotten too many good answers from this board to not ask here too. Thanks

The cluster pin outs might be the same but did you check the PCM pin outs?
If I put a 98 LS1 cluster in my 98 V6 car everything but the tach and oil pressure are correct. The oil is wrong because the gauge only goes to 80 on the LS1 cluster and 120 on the V6. The needle runs in the same place.

I plan on doing the LS conversion before spring but using the 01-02 motor and wiring harness.

[runtwrestlin]

Re: tach is off

Yea, I def checked all of that too. The gauge signals run through connectors c230 and c220. There were some slight differences in those from the LS1 engine harness to my 3.8 body harness, so I switched and matched and spliced where needed to send the right signals through the right wire. The main one was the fuel level gauge. The 98 LS1 gets it from teh PCM, whereas mine came directly from the tank. There were some others, but I'm too tired right now to rmeember (esxcuse..sp...wow...)

Awesome man. Have fun with your swap. I can't believe the difference in driving. Lots more getty-up an go :)

Unless you already have access to the pinouts of the connectors and stuff, I highly recomend subscribing to alldatadiy. The wiring diagrams on there made it so simple that even I, a novice with little to no prior experience, could do it.

[bigbrian442]

Re: tach is off

I plan on changing to the 01 up fuel level sender and under dash harness to the instrument cluster and cluster with 01 up the engine wiring harness. From what I have been reading all should work when changing everything like that. Harness to the fuel pump didn't change so that should be OK.

[Tom Rs]

Re: tach is off

so did you change out your body harness also in the interior ? Have any pics ? Also what about the fuse panel under the hood ? i am looking to do the swap this spring