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Dynoing w/o tach

Old 02-19-2007, 11:47 PM
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Dynoing w/o tach

Is it possible to properly dyno without a tach?
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Old 02-19-2007, 11:50 PM
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Originally Posted by Underpsi View Post
Is it possible to properly dyno without a tach?
Absolutley not.

Of course, any dyno that you dyno at will attach their tach themselves, so it's kind of a moot question...
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Old 02-20-2007, 12:06 AM
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Where would they attach it to on a non ic'd truck?
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Old 02-20-2007, 12:14 AM
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I Dynoed successfully without a Tach on my 93.
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Old 02-20-2007, 12:35 AM
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Originally Posted by Underpsi View Post
Where would they attach it to on a non ic'd truck?
As far as dynoing my 93, they ended up putting a piece of reflector tape on my fan belt. Some type of Object (Laser pointer) that was hooked up to the dyno, was placed under my fan belt to get a tach reading.
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Old 02-20-2007, 12:41 AM
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So it shouldn't be a problem for ANY shop with a dyno to get a tach signal?
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Old 02-20-2007, 05:27 AM
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Originally Posted by Underpsi View Post
So it shouldn't be a problem for ANY shop with a dyno to get a tach signal?
Thats right, they should put a piece of reflective tape on the dampener and get the signal that way. Even if you had a tach or had the wiring so they could hook up to it, its still alot easier to use reflective tape, not to mention quicker.
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Old 02-20-2007, 10:29 AM
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Would only shoips familar with diesel know how to do it or is it pretty much standard for guys to know how to do it with any dyno?
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Old 02-20-2007, 11:27 AM
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I think a rev on the crank is a rev on the crank is a rev on the... Gasser, diesel, don't matter.
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Old 02-20-2007, 03:03 PM
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I think that if you are giving your rig to someone who is going to mash it up to full power and tourque, And they are stumped with a tach hookup, You should get back in your truck and go somewhere else!!!!!! I wouldn't trust them.
Peter.
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Old 02-20-2007, 04:07 PM
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To count revs while dynoing, both times I had mine done, the operator put a reflective piece of tape on the harmonic balancer and the computer does the rest. You don't need an onboard tach to dyno.
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Old 02-20-2007, 04:15 PM
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great, thanks guys. Hopefully mine will be going on the dyno very soon. hopefully I will have a 64/14 on it first
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Old 02-21-2007, 12:46 PM
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On a dynojet if they can't get a good signal from the reflective tap on the damper, which happens alot, you won't get a torque reading. You'll only get a HP reading. Typically once the boost gauge levels off and falls off, you're done, no more power.
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Old 02-21-2007, 05:32 PM
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Originally Posted by bgilbert View Post
On a dynojet if they can't get a good signal from the reflective tap on the damper, which happens alot, you won't get a torque reading. You'll only get a HP reading.
Wouldn't it be the other way around, as horsepower is a function of torque and RPM?


I'm pretty sure that they all use optical tachometers. How would they supposed to use a tach hookup on the truck? Do surgery on every truck that gets on the dyno to splice out the hookup?
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Old 02-22-2007, 01:31 PM
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Originally Posted by Begle1 View Post
Wouldn't it be the other way around, as horsepower is a function of torque and RPM?

I'm pretty sure that they all use optical tachometers. How would they supposed to use a tach hookup on the truck? Do surgery on every truck that gets on the dyno to splice out the hookup?
I said DYNOJET. I've never been on a load or mustang (gasser trash) dyno before. I have no idea how they work. With a dynojet they measure HP by how fast you spin the rollers, which are a known weight (IIRC). Do a search if you wanna know the basics, differences.

With the tach pickup, they have to mount either a magnetic type mount or clamp type tach pickup underneath the engine/truck to read the tape on the damper. If for some reason this can't be done because of too much grease, something in the way of the tach pickup, can't get the pickup close enough etc, then you get no torque reading.
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