I've kinda wondered about this a bit...and just read a post by lshenretty who commented on the same thing and decided to start a thread on it. Sometimes I get the feeling that the speed my speedometer is reading is slightly faster than I am actually going. I know we have all discussed how in the TSX you dont "feel" like youa re going fast but you in fact are. But aside from that...is it possible the speedomter is off by a bit? I mostly notice this on the highway...when I think I am going kinda fast according to my speedometer...but everyone else is going roughly as fast. And I think to myself...am I not going as fast as I think I am ..or are people just driving alot faster than usual.


I dont even know if we can test this...hmmm.....

 

My speedo is off by 3 miles when I'm going 35MPH. It's the same way in my Mazda, and was in my Vw.

 

Police sometimes set up a speed detector in my neighborhood just to remind people not to speed in residential streets. All the three cars (including the TSX) I've driven past the detector have registered speeds lower than the ones shown on the speedometer at the time.

Of course, scientifically this doesn't really prove anything.

 

fdl, your timing is impeccable. I was on the highway today, and I slowed down for a construction zone. I thought I was doing 60 in a 55, but when one of those "YOUR SPEED IS..." signs popped up, it showed 58. Either the speedometer is wrong, the sign was wrong, or I guess both could be wrong.

Would this lead to a feeling that you're going fast but you really aren't? I doubt it, unless the inaccuracy gets much larger than 2 mph as your speed gets faster.

 

Had the same feeling so had my son drive along side to test it out. The TSX registered from 3 - 5 mph faster than my Hyundai Elantra, going between 50 and 80 (yeah the Hyundai can go that fast). My '97 Integra has the same problem. Must be a consumer satisfaction gimmick by Acura to convince us that the cars are fast. I'm convinced and satisfied without it.

 

Hmm...5 mph is quite a bit.

 

good thread.

this is a lot easier to test with reasonable accuracy than 0-60.

drive as close to 60 by the speedometer as you can and time yourself between mile markers. the farther you go - the more mile markers you use to time yourself - the more accurate it will be. if the speedometer is accurate, you'll average 60 seconds per mile, of course. the trick is if you don't average 60 seconds per mile.

So, count the seconds, divide by the number of miles you timed, and then divide that number into 3600. If you average 59 seconds per mile, for instance, your speed is 61.02mph.

Edit: Just had this discussion with Larch. You're gonna need to use a timing device of some kind. A watch can work, but a stopwatch is better.

 

C/D did a study on this, I think they found german cars "lie" the highest

 

What you all are suggesting is that you have some super human sense allowing you to discern the difference between 80mph & 83mph. I agree that when your traveling at interstate speeds the TSX feels like it's going slower than the speedo indicates. But it's more like it feels as if your traveling 65mph when the speedo says 80mph. And I have serious doubts that there is a 15mph discrepancy. I'm chalking it up to a good solid ride.

 

I just had another thought.....

If the speedometer is off (which it seems to be) ... is it also possible that the trip computer is off?? Then to take it a step further, wouldlnt this also lead into miscalculation of gas mileage?

Oh what a tangled web we weave ...

 

What I said was that it seemed like I was going slower than my speedo was saying because of how other cars were going as fast or faster than me. Not from "Feeling" the 3-5 mph difference.

 

Many manufacturers do this. They tend to deliberately err on the high side. While this prevents people suing for going faster than indicated and getting into trouble for it, I wish they could just get it right, or make it adjustable in some way. In many cases it doesn't affect the odometer reading (which may be taken off the differential).

One possible solution is to work out how much over it's reading (usually about 5-10%) and then pick a tire size that reduces the overstatement somewhat by increasing the overall diameter. This is not a good reason in itself to get new wheels/tires, but you can factor it in.

C.

 

or...
we could ask one of the friendly police officer/TSX owners on the forum to do some off duty testing with their department's radar gun???

 

I think it's because of the wierd V4. you've got some real forward movement going... but it feels like you're cruising along in your grandma's Geo Prism.

 

I think it could all be a big conspiracy:

1. Speed looks faster, people think the car is faster.

2. If it's connected to the odometer, MPG would be improved, looking better to potential buyers and EPA.

3. Again, if it's connected to the odometer, whos going to know that that Acura didn't really drive 200,000 miles. 3MPH difference at 60 MPH is 5% off. 200,000 miles x 5% off equals 10,000 miles the car didn't really drive. All those 10,000 miles probably add up on reliability ratings.

Not that I really agree with this, just something to think about.

 

Nice thread. New suggested direction:

What kicked this off was the debate over our own ability to observe times for 0-60. And for that, there's an additional question besides the basic accuracy of the speedometer:

How accurately does the speedometer reflect instant-by-instant changes in speed during extreme acceleration?

Even if the speedometer were 100% accurate in "steady state," which is what most of you are talking about, there would still be this additional question. I personally have no idea.

But if you all think it's impossible that the TSX 5AT can go from 0-60 in 7 seconds or less, my guess is the speedometer shows 60 prematurely, because I can just about promise you that the speedometer gets to 60 within 7 seconds.

 

Thats a bold statement However assuming that your counting may be off by .5 seconds and the speedometer is off by up to 5mph..I will buy this.

 

Very interesting topic.

Perhaps they lie a few mphs on the speedometer in order to keep your actual speed down. They might figure that everyone cheats by going 5 over (minus the 3-5) and BAM! you're doing the legal limit.

Of course, here in Detroit, the average speed is 20 miles per hour over as of two weeks ago. We have the fastest highwats in the U.S. so I wasn't surprised. If 20 is the average....you can imagine who is not just doing 20 over! YIKES!!!

 

Well, I've GPS verified my VW speedometer as being exactly 3 mph high (at least up to 85 mph or so).

Friends BMW 325i is a constant 2 mph off.

Despite the speedometer "error" (I think this is built in and deliberate to avoid ticket liability), my VW odometer is accurate to less than 1%. OTOH, my 88 Integra odometer was 3% high...

 

if you're speedo is wrong, your mileage is wrong. i don't think the speedo is off until you're going fast, like 100+. then it can vary about 10mph, i've heard.

 

oh another thing, if your speedo is off, and you get a ticket, can't you complain that your speed isn't what your thought? and you can get out of the ticket that way?

 

heh not if the speedo is showing faster than you were really going.

Judge: you were going 90 in a 55!
You: but I thought I was doing 100!

 

Wow..thats a big difference.

 

I thought it was widely assumed and well known that speedometers tend to be a couple of mph's high. I've occasionally tested it on my cars, and found it to be true. Never as much as 5, but maybe up to 2 or 3.

This doesn't make that much of a difference in the "self-tested" 0-60 time, which was what kicked off the question. My strong impression is it's much closer to 0.1 second than the 0.5 that some people say.

BUT -- we were also wondering about differences between 0-60 mph and 0-100 kph -- which is AN ADDITIONAL couple of mph. Add them together, and now we're talking something more substantial. I'd say the total might make a difference of 0.3 sec.; I know most people think it's more.

I still wonder if there might be an additional factor from the speedometer possibly being further off during extreme acceleration.
I have no idea about this, and I guess nobody much thinks this could be the case.

About what Donut said: I'm sure it's not routinely anywhere close to 10 off when you're "just driving." As to whether it might be that far off during extreme acceleration, that's exactly what I'm wondering about.

 

My earlier post when I said 3-5 mph was based on 5 mph under acceleration as opposed to 3 mph steady cruising (not totally scientific but close enough). The speedo definately seems to spin up more quickly under acceleration than it should. Given that, I still feel as you do, that the 0-60 times are better than most mags post. The mags timed my 140HP 97 Integra LS from 7.5 - 8.0 and my (50 year old) seat of pants feeling is that the TSX is much faster.

 

Some insurance companies will test your speedo for free. Mine doesn't but if you're part of the AAA Club of California, they have free speedometer checks with AAA membership every so once in awhile.

 

I don't think AAA would like to see many of us in speedos....:P

 

It would be great if someone can clearly identify just how much the speedometer is off in the TSX. rb1 do you volunteer? If you can GPS your car that would be awesome. Then again...how accurate is a GPS anyways?

 

Is that something that any GPS can do? And is it easy - is it a readout it will give you?

 

Someone here posted a thread about checking out the accessories we don't get on the Honda Germany site.

When looking at the wheel options on that site I noticed the 17" wheels came with 225/45/17s not 215/50/17s. Which begs the question, how does the speedo get set at the factory? And for what diameter tires?

Also if you look at the specs for tires at the tirerack's site, the same size tires in different models and brands will have slightly different diameters according to the manufacture's data.

So who knows? I

 

This thought crossed my mind as well. But I certainly hope that the speedo has been set properly for the diameter of our tires.

 

So could the speedometer registering a higher speed be the reason the trip computer is registering higher mileage numbers?
This would make sense.

 

Im also convinced my trip counter is not consistent.

 

On my X5 and my 325i there was a "trick" one could use to "hack" into what the computer was actually doing. It would give real speed, real fuel economy, engine temp, among a plethora of other things. On a trip last week I decided to use this function and found that while the speedo was reading 142 I was actually only going 136. Interestingly, there was actually a setting for "speedo speed" which digitally displayed exactly what the speedo was showing.

Bottom line is, I think the car knows better than we do in terms of odometer reading. In terms of speedometer error that's built in to save us from ourselves, but if the manufacture allowed the same discrepancy in terms of odometer reading then that would be fraud.

 

If anybody noticed in the C/D article, it also mentioned odometer accuracy. Odo does not work alongside with speedo. Their reading is based on undriven wheels.

Someone mentioned the accuracy of GPS. Depending of the equipment, it can be very accurate. But even the worse won't be a long way off. I would say, steady state cruising without acceleration should record the most accurate reading.

 

Yes you can (in some places). I once got a ticket significantly reduced once by producing a speedometer calibration report indicating my speedometer was off.

 

I would think you were lucky, unless you weren't going very much over the limit, anyway. I think the way the laws in most states are written, the burden is on the driver to drive at or below the legal speed, no matter what the speedometer reads.

 

Yes, I suppose the laws do vary from state to state, but the law is not necessarily absolute -- otherwise there would be little need for judges.

In my case, the original ticket was for 84 in a 55. I produced a speedometer calibration certificate showing speedometer was off by 22 mph, and the judge changed the ticket to 62 in a 55. This made a big difference in both the fine and the points, and I also avoided having the ticket reported to my insurance company.

At least one other person in the courtroom got completely out of their ticket this way...

 

Last night i was on the highway doing 60mph when i drove by a speed sign. the sign said that i was doing 57mph...

 

Sounds about right.

Although I bet if you had a magnifying glass you would have seen your speedometer was saying only 59.4, and the sign really meant 57.3.