Hypertech inline speedometer calibrator module

[Stormgray]

Originally Posted by agtitan06

Nissan allegedly does that on purpose to make your warranties run out faster. I believe there is a class-action lawsuit regarding that exact matter.

Not to jack the thread but this would include alot of people. Is it in the US or just Canada?

[bigdog]

I just found this article and thought this paragraph was relevant to the discusion:

One other point about changing gear ratios – in modern vehicles the computer that controls virtually everything has to have accurate road speed information. Vehicle speed information is typically generated at the transmission, which is “upstream” of the rear axle. Which means, of course, that changing the rear-axle ratio results in inaccurate speed information. This information plays an important part in controlling the fuel injection, the airbags, ABS, and speed display. If the rear-axle ratio is changed (or even if wheel/tire sizes are changed) the computer has to be updated for everything to function properly.

This seems like a pretty good argument in favor of getting the inline speedo calibrator. This seems to confirm the theory that tire size change affects alot more then the speedo and could be costing you MPG.

[Mainerunr]

Originally Posted by tomtom

I just found this article and thought this paragraph was relevant to the discusion:

One other point about changing gear ratios – in modern vehicles the computer that controls virtually everything has to have accurate road speed information. Vehicle speed information is typically generated at the transmission, which is “upstream” of the rear axle. Which means, of course, that changing the rear-axle ratio results in inaccurate speed information. This information plays an important part in controlling the fuel injection, the airbags, ABS, and speed display. If the rear-axle ratio is changed (or even if wheel/tire sizes are changed) the computer has to be updated for everything to function properly.

This seems like a pretty good argument in favor of getting the inline speedo calibrator. This seems to confirm the theory that tire size change affects alot more then the speedo and could be costing you MPG.

forgive me if I'm a bit skeptical about the mpg comment considering what I've averaged with larger tires, I just dont believe it.

further, well, nevermind that, we all know nissan can be stupid so yeah, they probably do base a lot of stuff on a parameter that cannot be adjusted to account for other changes (without aftermarket hacks that is)

[hunterdan]

I found the speedometer in my 08 to be reading about 3 mph or so fast. I just figured it was programmed with the NISMO tire size, 265/76/16's as opposed to the 267/70/16's. That could explain why the NISMOs seem to be more accurate.

Dan

[bigdog]

Originally Posted by Mainerunr

forgive me if I'm a bit skeptical about the mpg comment considering what I've averaged with larger tires, I just dont believe it.

further, well, nevermind that, we all know nissan can be stupid so yeah, they probably do base a lot of stuff on a parameter that cannot be adjusted to account for other changes (without aftermarket hacks that is)

hey, np being skeptical here, I think that's one of the advantages of the forum. I don't know the answer to this question either. As near as I can tell only one person has installed this speedo calibration module and he seems real happy with it. Everyone else is "doing the math in their head"

As for the Nissan comment, I don't think this is a Nissan specific issue, other then perhaps the lack of aftermarket options, but I'm not sure we can blame them for that either. The fact is when you change your tire size you change your "final drive ratio" and there is no way for the computer to compensate for that unless you tell it, and I'd be surprised if any production vehicles give you the ability to do that without some form of aftermarket tool. Its also pretty clear that most (if not all) modern vehicles use that information to control fuel injection, manage shifting, airbags, abs, and a host of other things. So not adjusting for this change can have a negative impact on the vehicles operation. What is not clear to me is how much of an impact will it have and how much is bad. Clearly going from 31" to 33" is less of an impact then going from 31" to 35", but I'm not sure at what point we should be concerned and make a correction.

It also seems clear that more important then getting the speedo right, is getting the gear ratio right. At some point we are increasing the gear ratio beyond the design specs of the drivetrain and that needs to be corrected by changing the pinion gear ratio of the rear end. It looks like we all (2nd gen) either have a C200K or M226 rear end. And within both of those variants there are multiple gear ratio combinitions. So swapping a C200K from a 6 cyl CC AT with that of a 4 cyl AT may give you the gears you need to compensate for the bigger tires. Ideally we could swap the gears without swapping the whole rear end, but I have not found that option for the C200K yet. This option is definitely possible on the M226 (Dana) rear end.

What's interesting is bigger tires with deeper gears brings you back to the original "final drive ratio" and may elimiate the need for speedo recalibration.

[Mainerunr]

Originally Posted by tomtom

hey, np being skeptical here, I think that's one of the advantages of the forum. I don't know the answer to this question either. As near as I can tell only one person has installed this speedo calibration module and he seems real happy with it. Everyone else is "doing the math in their head"

As for the Nissan comment, I don't think this is a Nissan specific issue, other then perhaps the lack of aftermarket options, but I'm not sure we can blame them for that either. The fact is when you change your tire size you change your "final drive ratio" and there is no way for the computer to compensate for that unless you tell it, and I'd be surprised if any production vehicles give you the ability to do that without some form of aftermarket tool. Its also pretty clear that most (if not all) modern vehicles use that information to control fuel injection, manage shifting, airbags, abs, and a host of other things. So not adjusting for this change can have a negative impact on the vehicles operation. What is not clear to me is how much of an impact will it have and how much is bad. Clearly going from 31" to 33" is less of an impact then going from 31" to 35", but I'm not sure at what point we should be concerned and make a correction.

It also seems clear that more important then getting the speedo right, is getting the gear ratio right. At some point we are increasing the gear ratio beyond the design specs of the drivetrain and that needs to be corrected by changing the pinion gear ratio of the rear end. It looks like we all (2nd gen) either have a C200K or M226 rear end. And within both of those variants there are multiple gear ratio combinitions. So swapping a C200K from a 6 cyl CC AT with that of a 4 cyl AT may give you the gears you need to compensate for the bigger tires. Ideally we could swap the gears without swapping the whole rear end, but I have not found that option for the C200K yet. This option is definitely possible on the M226 (Dana) rear end.

What's interesting is bigger tires with deeper gears brings you back to the original "final drive ratio" and may elimiate the need for speedo recalibration.

not sure I agree with your take on changing the gear ratios out of the design specs. I've got 3.69's, the tires make it behave as though it is higher (numerically lower). Now, even those with 3.36's arent dropping below 3.13 so I doubt there is a problem here.

It may be more of an issue with the computer not having accurate info on an auto but in a manual, the biggest issue I see is the ABS.

[sleepy23]

mine decision was purely speedo and odometer. my wheel/tires are slightly smaller and about 10lbs lighter (each) than the stock nismo combo...

[Sangster]

my 08 Nismo shows 80 on speedo when GPS shows 82. 60 on speedo when GPS shows 61.

[bigdog]

Originally Posted by Sangster

my 08 Nismo shows 80 on speedo when GPS shows 82. 60 on speedo when GPS shows 61.

My 06 shows 60 on speedo when GPS show 58, and 70 on speedo is about 67.

I wonder if they have the same speedo setup on all these vehicles regardless of tire size and gearing and that's why some are acurate, some are high, and some are low? I've got 30.5" tires stock and the NISMO had 32" (i think) looks like you could split the differance and have an acurate speedo.

[Phil'sFrontier]

My speedo vs. GPS(Garmin GPSMap 60CS) turned up results similar to above. Ranges from 3-4mph, down to 1-2mph faster.