68 Chevy II Build
09-17-2014, 01:08 PM
#141
On the tach call autometer tech again ... I think you need to install a 10 K ohm resistor in line... At least that's what they said for my Stocks ECU with HP tuners.. I have just been using the LS1 shift light that I robbed off my old Camaro though.
09-17-2014, 02:00 PM
#142
I used an Autometer tach with my HP, I didn't have to do anything, just use
the signal wire in the loose leads to the tach
my harness had some wiring errors from Holley, so you might want to buzz the lead back to the pin in the main plug
I remember my tach and relay wire color didn't match the dia.
the signal wire in the loose leads to the tach
my harness had some wiring errors from Holley, so you might want to buzz the lead back to the pin in the main plug
I remember my tach and relay wire color didn't match the dia.
09-17-2014, 07:36 PM
#143
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Do you remember the part number of that tach? The blue/white wire is outputting a signal that rises with RPM as confirmed with my multimeter. I want to go to the track and race this thing before winter hits and this problem is the only thing holding me up.
09-18-2014, 03:55 PM
#145
It should definitely only be a one wire hookup to the tach from the loom. I can't remember te color of the wire. I'd suspect the tach at this point. Also, I sent you a private message regarding our tune up. Fo some reason I wasn't able to ask it on the forum itself. Thanks and I'm looking forward to your answer. Nice car and nice build. It should haul!
09-18-2014, 04:10 PM
#146
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The laptop shows rpm correctly, and I've tried a couple different tachs even bought a new one with the same results. Holley has no insight other then "it should work". I might have to pull the damn harness and computer at this point and send it to them to figure it out. I'm convinced that after trying 3 tachs that can't be the problem. I tried Different power sources and grounds as well with no change.
09-18-2014, 07:43 PM
#150
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I don't know of anyone with one Ron, i put my multimeter on hertz I believe and it showed a number which climbed evenly as I revved the engine so I know its putting out some sort of signal.
09-18-2014, 09:44 PM
#153
Assuming 1000 rpm, 8 pulses per revolution, divided by 60 would be approx 133 Hz.
Prob more important is what voltage it reads. In AC volts.
DVM reads RMS voltage. So multiply the RMS value by 1.4 and that would give you the peak reading.
Then compare to what the tach needs.
09-19-2014, 03:46 AM
#154
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[QUOTE=adrynalinjunkie;18434649]Check this link out see where it says tach resistor?
http://m.summitracing.com/parts/atm-528
I have confirmed with both holley and autometer that they both do a 12v square wave so nothing else is needed to hook it up.
http://m.summitracing.com/parts/atm-528
I have confirmed with both holley and autometer that they both do a 12v square wave so nothing else is needed to hook it up.
09-19-2014, 03:48 AM
#155
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You could do some math and see if the HZ matches rpm.
Assuming 1000 rpm, 8 pulses per revolution, divided by 60 would be approx 133 Hz.
Prob more important is what voltage it reads. In AC volts.
DVM reads RMS voltage. So multiply the RMS value by 1.4 and that would give you the peak reading.
Then compare to what the tach needs.
Assuming 1000 rpm, 8 pulses per revolution, divided by 60 would be approx 133 Hz.
Prob more important is what voltage it reads. In AC volts.
DVM reads RMS voltage. So multiply the RMS value by 1.4 and that would give you the peak reading.
Then compare to what the tach needs.
09-20-2014, 06:44 PM
#156
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Well I got a manual boost controller today so put that baby on and what a difference 7lbs to 10lbs is. It still pushes through the brakes at 7lbs but I flipped the transbrake and it built 10lbs very quickly. It spools up faster with the contoller on for some reason, even with it backed off it got to my spring pressure faster then with spring alone. It also annihilates the drag radials letting the brake go at 10lbs which was really cool to feel the thing come unglued.
I was planning to hit the track tomorrow but rain is in the forecast. Hopefully I can get up there next weekend.
I was planning to hit the track tomorrow but rain is in the forecast. Hopefully I can get up there next weekend.
09-21-2014, 10:16 AM
#158
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That's what holley & autometer both told me as well. I tried yet another tach a sunpro this time from my buddy and it's doing the same thing. I'm going to pull the computer and send it back to holley once the cold weather hits and have them go over it. The wire is in the right connector and pin on the harness, it outputs a signal that does not match actual rpm so It has to be something in the computer.
09-21-2014, 01:10 PM
#160
68II how old is the harness? I had a problem with the ls1 harness a couple of years ago where 2 wires were mixed up at the connector. Once I knew what two wires were the problem it took one min to fix and my tach worked. On my new build all my stuff is from Holley so I didnt have that problem this time around. Maybe your stuff is older - just a thought. I'll dig through some emails and see if I can find it.