Tach not correct
10-19-2009, 07:47 AM
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Tach not correct Hello,
I have an LQ4 in a '67 chevelle and I have all my autometer guages working properly except the tach. at first the tach would barely register and my research on this site said it must be set to 4 cylinder, so I did this and now my tach constantly shakes up and down and reads too high. it say's I am idling at around 1100-1200 but HP tuners say's I am idling at 650-700 rpm. I understand that I can change setting in HPTuners for tach output, but I have no understanding of those settings. right now they are both set at 6, I have read to set it to 3, but what in fact are these settings controlling?
How do I get the tach to read correctly and how do I get the needle to settle down? What exactly do the settings above for tach output control/change?
Thanks
Rob
I have an LQ4 in a '67 chevelle and I have all my autometer guages working properly except the tach. at first the tach would barely register and my research on this site said it must be set to 4 cylinder, so I did this and now my tach constantly shakes up and down and reads too high. it say's I am idling at around 1100-1200 but HP tuners say's I am idling at 650-700 rpm. I understand that I can change setting in HPTuners for tach output, but I have no understanding of those settings. right now they are both set at 6, I have read to set it to 3, but what in fact are these settings controlling?
How do I get the tach to read correctly and how do I get the needle to settle down? What exactly do the settings above for tach output control/change?
Thanks
Rob
10-19-2009, 01:58 PM
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I run a autometer tach on my ls1 set on 4cycl worked perfect. My needle does flutter some at idle but not enough to worry about for me. I was told that you need to install a resistor to correct the flutter issue but I can't help if it just isn't working. Perhaps the lq4 puts out a different signal than the ls1 ecm.
10-19-2009, 05:16 PM
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I run a autometer tach on my ls1 set on 4cycl worked perfect. My needle does flutter some at idle but not enough to worry about for me. I was told that you need to install a resistor to correct the flutter issue but I can't help if it just isn't working. Perhaps the lq4 puts out a different signal than the ls1 ecm.
what software are you using to tune? Is your Tach Output resolution set to 6?
Thanks
Rob
10-19-2009, 07:10 PM
#5
It sounds like the opposite from when i had my autometer tach set up for 8 cyl. Rev limiter bumped at an indicated 3600 rpm when actual was 6850. Idle was an indicated 500 and actual was 900.
Try clipping the wires on the back and set it up for a 6? Good luck.
Try clipping the wires on the back and set it up for a 6? Good luck.
10-19-2009, 08:30 PM
#6
The tach signal setting in the first post works like this:
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
10-19-2009, 09:02 PM
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The tach signal setting in the first post works like this:
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
I thought the resister was only needed if the tach didn't work at all. The tach works, just seems to a grand or two too high or maybe double what the engine is actually turning. Are you thinking cleaning up the signal is going to make the tach read correctly or just stop the needle from wobbling?
by the way, your site [lt1swap.com] was very instramental in getting my car wired and running.....THANKS.
Rob
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10-19-2009, 09:32 PM
#8
I would think that if the tach is just reading off some, then its the # of cyl setting on tach, or programming in pcm.
If it is bouncing around more then it should, might try the resistor. The resistor just makes the tach signal stronger more or less. The stock tach signal is a 5 volt square wave signal. Adding the resistor makes it a 12 volt square wave.
The bouncing of the tach could be that it is missing some of tach pulses, due to filtering inside the tach its self. (why some tachs work, some dont.)
If it is bouncing around more then it should, might try the resistor. The resistor just makes the tach signal stronger more or less. The stock tach signal is a 5 volt square wave signal. Adding the resistor makes it a 12 volt square wave.
The bouncing of the tach could be that it is missing some of tach pulses, due to filtering inside the tach its self. (why some tachs work, some dont.)
10-20-2009, 12:31 AM
#10
??? The tach signal setting in the first post works like this:
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
24x crank shaft sensor divided by '6' = 4 tach pulse per engine cycle
so, setting the values to '3' will get you. 24/3=8 tach pulse per engine cycle.
So, if your tach is set for 4 cylinder mode, leave the setting at 6.
as for tach wiring, try this to clean up the signal. I had to add this to my 2003 PCM to make my autometer tach work.
Hmmmm,
I thought the resister was only needed if the tach didn't work at all. The tach works, just seems to a grand or two too high or maybe double what the engine is actually turning. Are you thinking cleaning up the signal is going to make the tach read correctly or just stop the needle from wobbling?
by the way, your site [lt1swap.com] was very instramental in getting my car wired and running.....THANKS.
Rob
I thought the resister was only needed if the tach didn't work at all. The tach works, just seems to a grand or two too high or maybe double what the engine is actually turning. Are you thinking cleaning up the signal is going to make the tach read correctly or just stop the needle from wobbling?
by the way, your site [lt1swap.com] was very instramental in getting my car wired and running.....THANKS.
Rob
Ok, thank you. Sorry for the interruption, please continue.
Nice site, lots of good info! busta9876 =
10-20-2009, 10:44 AM
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10-20-2009, 04:48 PM
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10-20-2009, 05:07 PM
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are you half high or half low? and do you know what your tach resolution is set at now?
I will change it to 3 when I get a chance. But If I understand those settings correctly now, that is going to make it an even higher reading. We'll soon see.
Thanks
Rob
10-27-2009, 11:06 AM
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OK,
I figured out that my tach is showing double what the PCM is showing. I changed the above setting [tach output] to 3 from 6 and then my tach showed I was idling at 2400 rather than the 600-650 the pcm was showing. I then changed it from 3 to 12 and it now shows what the Pcm claims but the needle is bouncing all over the place now. I am not sure why my tach seems to be different than everyone elses. I sware it is set to 4 cylinder. I guess it is time to get the wifes makeup mirror out and pull the dash half apart again.
Anyone know why I would need to use 12 in the tach output setting to get a correct reading?
Thanks again,
Merv, I am pretty damn sure changing from 6 to 3 is going to fix yours now.
Rob
I figured out that my tach is showing double what the PCM is showing. I changed the above setting [tach output] to 3 from 6 and then my tach showed I was idling at 2400 rather than the 600-650 the pcm was showing. I then changed it from 3 to 12 and it now shows what the Pcm claims but the needle is bouncing all over the place now. I am not sure why my tach seems to be different than everyone elses. I sware it is set to 4 cylinder. I guess it is time to get the wifes makeup mirror out and pull the dash half apart again.
Anyone know why I would need to use 12 in the tach output setting to get a correct reading?
Thanks again,
Merv, I am pretty damn sure changing from 6 to 3 is going to fix yours now.
Rob
10-27-2009, 05:01 PM
#17
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on my autometer purchase there were 2 4 cyl settings . one for 1 pulse and one for 2 pulse - it turned out to be the 2 pulse setting- forget the mirror you are taking the whole thing out. JOHN
10-28-2009, 12:44 PM
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not if I can help it!!! Which guages are those that you have with the chevy emblem? I don't think I have 2 4 cylinder settings, but I will check it out.Rob
EDIT.... My Ultra lite guages have two dip switches that are used to set either, 4, 6, or 8 cylinder. No single pulse or double pulse 4 cylinder settings.....
Last edited by robbied31; 10-28-2009 at 01:03 PM.
06-07-2016, 04:25 PM
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Tach reading about half After installing the resister, my tach reads about half what it should. The gauge cluster is from an 80's vintage camaro. I'm guessing that it's reading 8 cyl's and the signal is 4. Any way to change it or will I need an adapter?
