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White Elephant 01 8.1 burb.

folkenheath said:
I haven;t used HP tuners, but something is off on your data.

4 MPH error at all speeds would imply an offset in the equation, which is unlikely, because the intercept needs to be zero. It should be a ratio, like 4 MPH at 60 MPH, 2 MPH at 30 MPH, etc. In which case it would be 4/60 = .0667 or 6.67% error

So if the speedo is 4 MPH slow at 60 MPH, you could increase the output by multiplying the current output by 1.0667 (106.7 %)

If the speedo is fast, you could reduce the output by 1 - .0667 = .9333, multiply by .9333.

Make sense?
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I noticed the same thing with mine and I think speedometer are accurate in a small range so I calibrated at cruising speed
 
I new mechanical speedo were off by different amounts across the range. I expected electronic to be accurate for the whole range.
 
Wes Harden said:
I new mechanical speedo were off by different amounts across the range. I expected electronic to be accurate for the whole range.
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Once you get the ratio right it should be dead on the whole time. It's a ratio though, so any error is multiplied the faster you go.
 
I wouldn't trust basing your error off of GPS.
I had a gps speed app, the GPS speedometer for my CC, and my wife's phone showing speed on Google maps all showing 2-3 mph different from each other in the same vehicle on the same road trip. The was a 5mph difference between the fastest reading and slowest.
I trust a hard wired computer doing math more than space magic from the air myself.
 
shady said:
I wouldn't trust basing your error off of GPS.
I had a gps speed app, the GPS speedometer for my CC, and my wife's phone showing speed on Google maps all showing 2-3 mph different from each other in the same vehicle on the same road trip. The was a 5mph difference between the fastest reading and slowest.
I trust a hard wired computer doing math more than space magic from the air myself.
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That's why I get up on the highway and set it at cruising speed and let it settle for 20 seconds and I use that number
 
That's what we were doing lol. Smooth cruising on flat long stretch. To this day my CC one reads almost consistently 4mph slower than Google maps at 60. But not always. Some times when I check it's 2mph. Lol.
Funniest one was the app I had on my phone, (like a generic DRAGY), read different by 1-2mph than my same phone did when I switched over to goggle maps. Same device:doah::dunno:
To me GPS is a close ballpark.

Really if I get my vehicles within 3-4 either way at 65 I'm happy.
Not sure if it's accurate either, but we have one of the radar speed warning deals on the highway south of town. I usually check my dash against that.
 
The Speedhut GPS speedo in my buggy is dead on the radar speed signs. I wish Speedhut made a gps speedo for my square
 
I use an app called GPS essentials, it has speed readout among many other things, and it also tells you exactly how many satellites there are being used at the current time. When you have 12 or 15 satellites it is very accurate. Its dead on with my bone stock speedo every time. Once the vehicle is calibrated, the speedo sensor is better than GPS because it works in tunnels, under trees, etc. And it doesn't have to "load" when it starts up.

I use the same app to calibrate the autometer speedos, where you drive 2 miles. So I drive in a straight line until the app tells me I have moved exactly 2.00 miles while the gauge counts the pulses, and then I hit the button again, and then the speedo matches the GPS exactly.
 
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I just keep pace with traffic which around here is 5-10mph under the limit so it doesn’t really matter.
 
In Kommiefornia is 3 axle speed limit 55, when 2 axle at 70, but everyone is doing 80.
I'll be towing tomorrow so I need to stay under 65.
That 8.1 doesn't even know the singe axle aluminum trailer with dune buggy exists maybe 2500-2800 lb

Plus with correct odometer I expect my mpg to improve
 
6872xtc said:
I don't remember how my son did the correction in my '01 2500, but we did discover while he was watching HP tuners, that the vehicle speed in the ECM didn't exactly match what I was seeing in the speedometer. I have 265 tires, which is why he made a correction, but I had him leave it showing just shy of 2 mph fast. I would rather have it skewed that way than reading slow as I tend to drive slightly over the speed limit most of the time.
Just a thought.
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This one had 265's on it when I bought it, and GPS check of the speedo on 40 mile drive home had it dam close, those tires were junk, and noisy as F, when I replaced I put the factory size on 245 75r16. Speedo has been off since July 22. Cruise control should keep outta trouble :D while I relearn
 
Blue85 said:
Nope, a good odometer only improves your math, not the real economy. ;)
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yes sir and my maths say average 11.5 with the old calibration. hoping to see 13, will hit the same Pilot truck stops this year I did last :D
 
I can't even check my burb because no odometer at all. I figure that's a good thing though because maybe I don't want to know lol
 
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