tach
tach Swapped a 98 LS1 into a 97 (formerly 3.8) camaro, and of course 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 the same...). 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? 
Yep, you're right. I just found the info on HPTuners. I changed the tach output, and now it works nice 
In case someone else on here has searches, I copy/pasted the info.
In case someone else on here has searches, I copy/pasted the info.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.
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.
I am going to use a stock tach for my conversion in my corvette. I am not sure I understand what numbers I need in my Tach Output Resolutions High and Low. It looks like I need to put 3 in both blanks, is this correct?
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
Yes if the tach that your trying to use was designed for an 8cyl then put 3 in both the high and low output resolutions
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Teching In
Joined: Apr 2009
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I want to make sure I got this right before I do the 12V switched with the 680 ohm resistor thing, ok?
The ecm I'm using is the 0411 and tuning with EFIlive.
The donor is corvette with the digidash( old style HEI originally)
On EFIlive instead of using the resistor I can set it( the tach value in the ecm) to switched and pull the values to 3 correct? Just making sure.
In case the info is needed, the engine being used will be a 5.3(2001) at first and then a 6.0(2004) later on.
The ecm I'm using is the 0411 and tuning with EFIlive.
The donor is corvette with the digidash( old style HEI originally)
On EFIlive instead of using the resistor I can set it( the tach value in the ecm) to switched and pull the values to 3 correct? Just making sure.
In case the info is needed, the engine being used will be a 5.3(2001) at first and then a 6.0(2004) later on.
