mike, the digital tach
#1
04-22-2002, 09:08 PM
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mike, the digital tach
hey mike,
i have read some of your posts before about the accuracy of the stock tachs. about how it can be and most of the time is about 500 rpms off especially at WOT. well i was messing around with my odometer checking out all the features i never new i had. (pretty cool actually) when i came upon the tach. i tried it and it worked pretty good. my question is how accurate do you think or know that this tach is? just curiouse, thanks for the info.
i have read some of your posts before about the accuracy of the stock tachs. about how it can be and most of the time is about 500 rpms off especially at WOT. well i was messing around with my odometer checking out all the features i never new i had. (pretty cool actually) when i came upon the tach. i tried it and it worked pretty good. my question is how accurate do you think or know that this tach is? just curiouse, thanks for the info.
Last edited by LBC150; 04-25-2002 at 01:16 AM.
#2
04-24-2002, 11:00 AM
Former Sponsor
Hi LBC150,
Ahh, so you've discovered the trick of turning the digital odometer into a number of different digital gauges......... pretty neat, eh? It will also give you numerous other displays, like a digital speedometer so you can see how fast the truck is going once the analog speedometer is exceeded, etc.
I don't think anyone has ever really checked out just how accurate it's digital tach display is, no testing, so we really don't know. In general, digital tach readouts don't work really well in my humble opinion, as they're generally slower in their response, or I should more accurately say, they used to be, I don't really know if that is still the case today, as we don't use them. The digital tach feature of the odometer is getting it's electronic signal from the same source as the dash tach I believe, but it is a different gauge, part of the odometer, so it will have it's own unique characteristics.
Also, just to be clear, I wouldn't say that all of these tachs are off by 500 rpm; a good number are, but that does vary as well. Some of these tachs can be fairly close, within 100-200 rpm, and then we've seen some read too high, and even a few read too low. But not *all* of them are the exact same in that regard. When idling and when cruising, the tachs are pretty accurate; the issue of inaccuracy is primarily when accelerating hard, and more so in 1st gear, naturally, as that is the forward gear in which the engine gains rpms the quickest. So while a lot of them can be 500 rpm off when nailing it just before the upshift, not every single one of them gives that exact result. No big deal, I just didn't want to leave you wioth the wrong impression that they all did the exact same thing, there is some variance.
Ahh, so you've discovered the trick of turning the digital odometer into a number of different digital gauges......... pretty neat, eh? It will also give you numerous other displays, like a digital speedometer so you can see how fast the truck is going once the analog speedometer is exceeded, etc.
I don't think anyone has ever really checked out just how accurate it's digital tach display is, no testing, so we really don't know. In general, digital tach readouts don't work really well in my humble opinion, as they're generally slower in their response, or I should more accurately say, they used to be, I don't really know if that is still the case today, as we don't use them. The digital tach feature of the odometer is getting it's electronic signal from the same source as the dash tach I believe, but it is a different gauge, part of the odometer, so it will have it's own unique characteristics.
Also, just to be clear, I wouldn't say that all of these tachs are off by 500 rpm; a good number are, but that does vary as well. Some of these tachs can be fairly close, within 100-200 rpm, and then we've seen some read too high, and even a few read too low. But not *all* of them are the exact same in that regard. When idling and when cruising, the tachs are pretty accurate; the issue of inaccuracy is primarily when accelerating hard, and more so in 1st gear, naturally, as that is the forward gear in which the engine gains rpms the quickest. So while a lot of them can be 500 rpm off when nailing it just before the upshift, not every single one of them gives that exact result. No big deal, I just didn't want to leave you wioth the wrong impression that they all did the exact same thing, there is some variance.
#4
04-25-2002, 01:21 AM
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#5
04-25-2002, 01:45 PM
I would have more faith in the degital tach. Granted it responds to the same input signal but its responce is instantanious. The analog tach has to over come the friction of the needle moving.
The question is weather it reads true or not. The only way to tell is to try and set your engine speed to a fixed rpm and note the difference in the two readings. I checked my digital tach VS the analogue. I get A= 2100 D= 2180, A= 2900 D= 2900 A=3500 D= 3524. All I can be sure of is that when I hit the revlimiter I know for sure the Engine is turning 6500 rpm
The important thing for a tach to be is consistant. Even if it is off by as much as 500 rpm, as long as it is always off by that much you can still get the job done.
Regards
Jean Marc Chartier
The question is weather it reads true or not. The only way to tell is to try and set your engine speed to a fixed rpm and note the difference in the two readings. I checked my digital tach VS the analogue. I get A= 2100 D= 2180, A= 2900 D= 2900 A=3500 D= 3524. All I can be sure of is that when I hit the revlimiter I know for sure the Engine is turning 6500 rpm
The important thing for a tach to be is consistant. Even if it is off by as much as 500 rpm, as long as it is always off by that much you can still get the job done.Regards
Jean Marc Chartier
#6
04-25-2002, 10:55 PM
Former Sponsor
Hi JMC,
Good point, thanks for you post.
Actually, you raise my curiosity, I wonder just how it actually is these days, meaning the comparison of the actual response time of the digital tach feature versus the movement of the analog needle; you're probably right in terms of time to register data in that regard, when you put it like that it sounds like a no-brainer.
It used to be, for years, digital gauges of virtually any kind, from speedometers to tachs, etc., have been plagued by slow response rate (data refresh rate), specifically in terms of their ability to display rapidly changing data, like a tach or speedo when accelerating hard. Digital readouts don't give the smooth kind of linear progression like you get with an analog needle dial, where you can see it sweep thru it's static numbers in perfect linearity; meanwhile, the digital only displays one data set per each response it's capable of. Even in Corvette digital speedos, it's common to see them jump from say, 5 mph to 27 mph to 43 mph and so on when accelerating hard, and to actually register as much as 15+ mph after coming to a sharp stop. To say nothing of a digital tachmeter response rate, or perhaps I should say, sampling rate.
As always, you make me think JMC!
Good point, thanks for you post.
Actually, you raise my curiosity, I wonder just how it actually is these days, meaning the comparison of the actual response time of the digital tach feature versus the movement of the analog needle; you're probably right in terms of time to register data in that regard, when you put it like that it sounds like a no-brainer.
It used to be, for years, digital gauges of virtually any kind, from speedometers to tachs, etc., have been plagued by slow response rate (data refresh rate), specifically in terms of their ability to display rapidly changing data, like a tach or speedo when accelerating hard. Digital readouts don't give the smooth kind of linear progression like you get with an analog needle dial, where you can see it sweep thru it's static numbers in perfect linearity; meanwhile, the digital only displays one data set per each response it's capable of. Even in Corvette digital speedos, it's common to see them jump from say, 5 mph to 27 mph to 43 mph and so on when accelerating hard, and to actually register as much as 15+ mph after coming to a sharp stop. To say nothing of a digital tachmeter response rate, or perhaps I should say, sampling rate.
As always, you make me think JMC!