Speedo Correction for Larger Tires

[Howard70]

Hello Folks:

I'm new here - lurking to learn about Sportsmobiles before we hopefully purchase one. I'm not sure this is the sort of correction some of you are looking for, but I just purchased a simple and relatively inexpensive ($80) from 12Oclocklabs (http://www.12oclocklabs.com/) to correct the speedometer of our Tacoma running 33" tires. It's an emprical correction - you use a GPS to determine your actual speed at an indicated speed, use their formula to calculate the percentage correction required, and enter that % correction into the unit.

It requires tapping into the OEM speed sensor lead and a 12 volt power lead.

12OClockLabs sells them with a satisfaction guarantee, so if it doesn't work on your van you can send it back. While they were designed to correct speedometers on motorcycles, they apparently work on many (most?) other wheeled vehicles. I'm using ours to replace a larger and less weatherproof unit from Superlift (http://www.superlift.com/accessories/truspeed.asp). That unit worked OK for quite awhile, but has not resisted water very well.

Howard Snell

[geoffff]

Originally Posted by Howard70

I just purchased a simple and relatively inexpensive ($80) from 12Oclocklabs (http://www.12oclocklabs.com/) to correct the speedometer of our Tacoma running 33" tires.

Thanks, Howard -- This may be exactly what I'm looking for. Maybe I'll try using the 12oclocklabs product with my Diablosport Predator tuner.

I've been trying to make some engine modifications using my Diablosport Predator U7152 (specifically, the speed limiter), but it screws up my speedo calibration, which is frustrating. I just heard back from Diablosport, and they say that they can't calibrate the speedo signal. ("[...]this is a feature that is not supported on the V10s due to the fact that they calculate tire size through the ABS module, which the Predator does not communicate with.")

-- Geoff

[Howard70]

Hello Geoff:

The 12OClockLabs might work. Although I'm not certain, I think that what it does is alter the signal sent from the sensor to the computer unit that then tells your speedo indicator what to display. If your sensor sends 1,000 pings a minute to indicate 60 miles an hour, but your real speed is 10% less than that then the unit receives the 1,000 pings, but only sends 900 pings on to the computer. If I'm correct (which is a big assumption...) then the unit isn't changing any thing in the computer - it is only changing the signal sent to the computer.

Good luck,

Howard

[geoffff]

Originally Posted by Howard70

Hello Geoff:

The 12OClockLabs might work. Although I'm not certain, I think that what it does is alter the signal sent from the sensor to the computer unit that then tells your speedo indicator what to display. If your sensor sends 1,000 pings a minute to indicate 60 miles an hour, but your real speed is 10% less than that then the unit receives the 1,000 pings, but only sends 900 pings on to the computer. If I'm correct (which is a big assumption...) then the unit isn't changing any thing in the computer - it is only changing the signal sent to the computer.

Good luck,

Howard

Exactly! That's what I'm hoping for. As far as the van computer is concerned, it's getting a speed pulse rate that indicates the speed appropriate for the original/default wheel/tire setup.

I'm not sure yet if the signal from the ABS system matches the "3 wire Hall Effect type sensors, [or] 2 wire Ground Switch type sensors" the SpeedoDRD unit is looking for -- or if there is an easy way to splice in between the ABS and the computer.

-- Geoff

[Ford_6L_E350]

It may make your speedo accurate, but at the cost of a constant ABS error. There are 3 ABS speed sensors, one on each front wheel and one for the rears. If the ABS detects a speed difference it may give an error or release the rear brakes to prevent a skid.

Mike

[carringb]

It should work with the V10 since the speed signal uses the tone ring in the transmission tailshaft. The ABS signal is from the differential and front wheels.

on edit: oops. Just noticed the year of the van. For newer vans using the PCM to do it is the correct way. I'm not when, but at some point the vans switched to the ABS sensor for speed.

But... On 2000 vans, it's in the tailshaft.

[geoffff]

Hmmm, thinking about the idea of the ABS sensor being used for speed -- I just read online a thought that makes sense to me: How can it be using the ABS sensor if the speedo is 4x (or whatever) off when the Atlas transfer case is in Low range (as it is on my van)?

If my van was really using the wheel ABS sensor, it should be unaffected by anything but wheel speed, right...?

-- Geoff

[Christopher Thwaites]

I ordered a tuner from 5Star and had it loaded with 3 programs. 87 0ctane, 87 Octane while towing, and 92 Octane. I'm half way through a 2500 mile trip and so far my avg. mpg has improved by 2 mpg. The tuner also corrected the speedo error for my larger tires. Shift patterns have changed and are much smoother. I haven't towed anything yet. I am very happy with my results. I don't know anything about other tuners but each 5Star is individually programmed based on your particular vehicle and needs.

[jlrray]

Originally Posted by geoffff

Being an engineer-type, I'd love to have a programmer device that has an "advanced" mode like the Scangauge, where you just send the PCM computer raw number codes and get raw numbers back -- so people can invent & trade ideas & hacks online. (I love my Scangauge.)

What kinda things can you do with your scangauge?

[BroncoHauler]

Originally Posted by Christopher Thwaites

... and so far my avg. mpg has improved by 2 mpg. The tuner also corrected the speedo error for my larger tires...

Chris,

If I were to get a tuner, I would get an SCT. Seems to have a great rep. Is your mileage comparison based on hand calculations, or based on what the van or ScanGuage tells you?


Herb