darksky

I noticed my needle speedo is off (reads 4 MPH too fast) when I compare it to the average MPH in the MID. Is there a way I can fix it (adjust it down 4 MPH) myself? If I can't do this, can the dealership do it?

Details: I set the cruse control to 74 MPH (as indicated on the needle speedo). I go into the trip computer and reset it... after about 3 miles, the average MPH on the MID is 70 MPH! This is true for speeds under 40 MPH as well as above 80 MPH. 64 MPH in the speedo is 60 MPH in the MID; 70 MPH in the speedo is 66 MPH in the MID, etc.

I believe the digital display (the MID) is correct because if I drive a known distance (the mile markers on the highway are spaced roughly 1 mile apart), the trip odometer is dead on for 1 mile of travel even after 30 miles. In other words, I reset the odometer as I passed a mile marker, even after 30 miles of traveling, they [the mile marker signs] are consistently coming up as the odometer measures 1 mile.

I did just get new tires (same size and the error should be <0.2 % based on the revs per mile difference in the stock tires to my new ones), but I would think if they were to blame for this, both the MID and the needle speedo would be off).

Thanks all!

csmeance

I believe the car was designed like this. When some 6MT guys read 160 on the speedometer, the car starts to limit them. The governer is at about 155, so about a 5 mile difference.

darksky

Can anyone else confirm this behavior in their TL by doing that setting the cruse control and going 3-4 miles experiment I outlined above? Does your speedo have this same 4 MPH offset?

BTW, the difference in revs/mile from the stock tires to the new tires is 817-820 / 817 = -0.36 % which doesn't account for this by a long shot!

Bridgestone Turanza EL42 235/45-17 revs/mile = 817
Bridgestone Potenza RE960 AS 235/45-17 revs/mile = 820

ggesq

iTrader: (1)

Might be helpful: https://acurazine.com/forums/showthr...ht=speedometer

https://acurazine.com/forums/showthr...ht=speedometer

01tl4tl

An authorized speedo repair shop can probably get you a different drive gear- assuming the new cars are not total electronic signal driven units

First I would use a portable GPS and see what it says about your speed
My gen2 read 2 mph fast at speed, much like the 5% high the court says our car reads- for purposes of what mileage indicated vs actual on an extended warranty like the trans

Bearcat94

Couple of days ago, with my daughter's new portable Navi, we compared the Mavi GPS speed to the inidcated speed on the '07 TL-S (stock tires, susp, etc).

The TL-S was dead nuts to the GPS measurement.

I wouldn't F with your speedo until you find a better way to measure your actual speed. You don't know what goes into the MID TC, if there is any lag from your reset, etc.

I agree it sounds questionable, but find a freind with Nuvi or TomTom and double check.

darksky

Guys - as sort of a follow-up request to my post here about my speedo (the needle speedo) reading 4 MPH faster than my MID's average MPH with the cruise control set, can some of you repeat my experiment and write back with your results in this thread?

Set your cruise control for whatever speed you want, say 60 MPH. Now go into your trip computer and reset it once you're convinced the cruise control has leveled out your speed. After driving 3-4 miles, what does your average MPH in the MID read?

Thanks all!

SouthernBoy

I've done this, though a while back, and the MID reads the same MPH, within 1 MPH, that my speedometer does. Best thing to do (which you have probably already done) is to find a nice level stretch of road without lights, hills, or stop signs, and light traffic. Get up to a good constant speed, such as 60 MPH, then set the MID. The MID should read within 1 MPH of your speedometer reading.

darksky

Yeah, I tried this about 10 times over the course of a 300 mile road trip yesterday; the MID is consistently 4 MPH slower than the needle speedo from speeds between 40 MPH up to 85 MPH. I tend to believe the MID for the speed based on some observations I made using highway mile markers; have a quick look at that thread I referenced in my original post for more details.

Guess I'll be calling the dealership. Anyone else care to do the experiment and report back for me?



Thanks!

SouthernBoy

Keep in mind that if you have changed tires and your newer tires are larger or smaller in diameter, your speedometer will register slower or faster speeds respectively.

ggesq

iTrader: (1)

To the OP, I am merging both of your threads. No need to have a brand new one.

Adobeman

Is 4mph error really something all that important to obsess about ? We're not talking about an aircraft quality gauge here.

Ron A

Since you are using highway mile markers already, what you really need to do is to set your cruise control at any constant speed. Then, if you have a stop watch (if you don't, have a passenger start timing) when you are next to a mile marker. When you reach the next mile marker (I usually try to go 3 miles, if possible, to get a more accurate reading) stop the stop watch or have your copilot note the number of seconds that elapsed.

Then, do the following calculation:

Divide 3600 by the number of seconds you counted. (If you went 3 miles, divide the result by 3 to get an average reading for 1 mile).

This will give your actual miles per hour. You can then compare this to the miles per hour you were travelling when you performed this calculation.

This is the only positive method to determine the accuracy of your speedometer.

I have done this several times and my speedometer is always less than 1% off, which means if I am going an indicated 60 mph, I am actually going around 59.4 miles an hour, which isn't enough to really worry about.

Krazylegs

If the spedo is off by 4 MPH, wouldn't Your odomitor be at least 5% higher than actual. If you are in a lease and drive your actual 15,000 miles, you odomitor is going to be 2,250 miles over your limit. This could cost you thousands of dollars of overages that you do not deserve.

Here is another test, compare the odomitor to the MID

trancemission

this pretty much sums it up for me

who gives a shit what the MID says. I never look at what my average speed is...

darksky

@Adobeman - I can be a bit obsessive about my vehicles
@Ron A. - Good idea, I'll have to pick up a cheapo stop watch and try this.
@Krazylegs - The odd thing is that the odometer is spot on when I reset it as I passed a mile marker. 30 miles later, it was still accurate (rolled over to xx.0 as I passed the mile marker sign). When I compared the MID to the odometer, they matched up to the nearest mile (since the MID has only whole numbers).
@trancemission - I guess I can just ignore my MID's average speed and MPG calculation but that sort of defeats the purpose of having that feature!

Seems as though my needle speedo is correct or at least consistent when compared to the wife's car... so assuming her car is accurate, this means the average speed in the MID is incorrect and likely, my MPG as well.

I need to borrow a GPS from a friend later in the week to verify the needle is indeed accurate.

Anyway, thanks for all the replies!

steve9207

Regarding what Ron A said about the stopwatch idea...I'd go this route, rather than relying on your MID for accuracy. Perhaps the MID is off and not the spedometer?

I've noticed that when I check my Average MPG everytime I fill up it is off anywhere between .5 to 1.5 MPG. I know this because I always fill up at the same station (same pump most of the time) and let it fill till it shuts off. So, I take the miles I drove (lets say 200), divided by how many gallons I filled up (lets say 10), to get 20 MPG. I'm sure there's other factors involved (such as not shutting off at the exact same time each fill up, but I guess my point is that the MID is not always dead on... my

Ron A

The average miles per gallon feature is useful if you use it as it is intended, which is to tell you your average MPG for the entire tank. This will give you an idea if something is wrong if you have been driving as you usually do and your MPG drops suddenly. And my MID has always been dead on whenever I manually calculate MPG by dividing the gallons used into the miles driven, taking into account that the MID rounds off the figures.

There are too many variables involved to make comparing the MID average miles per hour to the speed you are actually driving. It never occurred to me to compare MPH in the MID to what the speedometer is reading.

darksky

Cool, thanks, Ron. I have a GPS now and will compare it to my speedo later today to put this to rest once and for all. I guess as long as it's displaying my true speed, I'll be happy.

As to the trip computer, I assumed that MPG feature would be more useful than just displaying the MPG for the entire tank. Seems like I could reset it when I start a highway trip and get an accurate read of the mileage on that trip... I'm thinking that if the average speed is off by some %, the MPG would also have to be proportionally off too.

Anyway, I'll let you guys know how the speedo compares to the GPS.

NightRider

With several Acuras and a MB under my belt, I have found that the average speedo seems to be off around 3 mph average over the actual speed traveled at. This has been determind by GPS, navi, police mph signs, etc. Most car companies do it as a safety measure, they would rather you think you are going slightly faster and have a cushion than to get into trouble for going over the speed limit unintentionally. This is also why many 0-60mph tests are also measured in 0-100km (which is actually 62 mph). I believe it is an inherent design feature and not anything to be worried about enough to contact the dealership about. Chances are they will think you are just a nitpicking, over analyzing bastard (a category I sometimes fall into myself).

Bearcat94

Just did the Speedo vs Portable GPS/Navi thing again. This time in the '02 TL-S. Again, speedo is dead nuts to the GPS.

I did notice that there is a small lag in the GPS speed (which makes sense). So when you do the test, get stablized on a speed and give the GPS a few seconds to catch up.

BTW NightRider - Your theory on 0 - 100km vs 0 - 60 doesn't hold up. The 0 - 60 tests or the 0 - 100km tests don't use the Speedo. They use independent timing/scoring systems, GPS systems, etc.

There's no way you could get reliable and repeatable results with some guy holding a stopwatch and the driver saying, "NOW!" -

darksky

@bearcat94 - I just borrowed a Magellan 4000-something-or-other and found that if I set my cruise for 70 MPH, the thing bounces between 68 and 69 MPH. Which at worst is a 3 % error. I did learn one thing: I don't care for the Magellan series of GPS devices!

erick3

Yup...i'm about 3 off, but it's been like this for a while; i asked acura of lynnwood to check it out, and they just told me that it was fine... w/e

eric

Bearcat94

Well if your real speed is, say, 68.5 and your speedo says 70, that's not so bad.

Somebody did a calculation on the difference between new tires and tires worn to the wear bars and the Revs per Mile changed by ~3%, which would change the speedo. I know you said you were running new tires though, so it that shouldn't be make any significant contribution.

NightRider

:gheylaugh: Ya I just hypothesized that the 0-100km (62mph) was done to eliminate the chances of 0-60 actually being 0-58 (heaven forbid).

darksky

Well, the needle speedo acuracy aside, can anyone do that experiment where you set your cruise for some speed (say 70 MPH), then reset your trip computer and drive for a few miles and compare the average speed to the speed you set your cruise for and report back for me?

Something just doesn't sit right with me: if my speed is a CONSTANT 70 MPH, the average speed should also be 70 MPG, not 65 or 66

Thanks all!

leedogg

keep the speedo out of wack, and if you ever get a ticket, you can get a speedo calibration test to prove your speedo is off, and the judge is likely to dismiss the ticket. Saw it happen to somebody else when i was in traffic court. Unfortunately mine was inline when i got it calibrated...ironically I have 19's with 245/35/19 tires...which have a slightly longer diameter than oem...

darksky

Yeah, the best defense is not to offend. Learn to set your cruise for 7-10 over and just keep it as such :p

How about you leedogg... is your speedo inline with your ave speed in the computer?

avs007

I doubt you can adjust the speedo. There is no gear in it, and there is no spinning cable connected to it....

The speedometer is actually digital, and receives speed information from the ECU. It just presents this info to you using a needle....

Even my 98' Pontiac is setup this way. If Acura is still using a mechanical cable to drive the speedo in this day and age, I'd be surprised.

Krazylegs

Try driving the car and taking the car up to Max speed and pin the needle at 160 MPH. That might correct the problem.

Bearcat94

In the Navi Setup area there is an option for "Tire Calibrate".

I don't know how it works, but is suspect it for Oversize or Undersize diameters. Assumiing that's right, if you adjusted that by x% wouldn it "fix" the speedo?

darksky

Wonder how to access this feature for TL's wo/ Nav?

McKulit

I did the experiment on my way to Newark Airport. From Princeton it's about 30 miles. My mid said 70MPH speed average. I have an 04 TL with A-spec rims.