[SweetEBPSi]

My friend put a new gauge face in his TA Ram Air and he asked me to pace him on the highway with my Si. The difference between the two was about 4-5 mph, with him being on the higher side. We both thought that his car was off and mine was correct but later he paced his dad in a different car and they were the same. Well I didn't believe him so I paced my other friend and found out that it was my speedo that was off. My question here is how do I go about getting that fixed to the right speed? Also, I haven't done any mods to affect my speedo. The rims and tires are still stock.

 

[Sam]

Speedo's are never 100% accurate. Try driving your car past one of those radar meters (displays) and you'll know what I mean. If your car is still under warranty the dealer may replace it for you. Did you install any aftermarket electronics??

 

[SweetEBPSi]

All my mods are listed in my sig. Like I said, I haven't put any mods on it to make the speedo be off. Yeah. It's still under warrenty. I bought the 7 year, 100,000 mile warrenty. Looks like it will be paid off with this and a couple of other things too. Also, how would my dealer check to see if it is off or not?

 

[Sam]

A tech at the dealer will most likely test drive it and dertermine if its an electrical problem or a defective speedo.

 

[CivicSiRacer]

That sounds about right. Most speedos are off by around 4-5mph +/-. There is no need to get it fixed as my friend who worked at a speedo shop told me they only set odometers to within 500 miles since air pressure changes the diameter of tires causing some variance.

Are your air pressures all the same? Does he run aftermarket wheels/tires? Do you?

 

[just chillin]

yeah all speedos are off by a couple mph's. don't worry about it so much. there is not a 'correct' speedo out there (though i heard bmw's and m-b's make more accurate ones).

 

[Maniac]

The speedometer is one of the most inaccurate instruments on the face of the planet. Honda's accuracy specification is +/- 5%. In addition to this fact, one thing they never tell us is that there is a range of accuracy involved with any instrument.

What that means is that the +/- 5% will only apply to a specific range of measurement. So for example a speedometer could be ranged for 0 to 160KPH. Outside of this range manufactuers don't really care what it reads anymore because you are undoubtedly over the limit and accuracy doesn't matter to them.

Running a hypothectical, at 160KPH you could potentially be reading a swing of 16 KPH. So anywhere from 152 to 168 KPH could be your actual speed and that would be considered normal error. It's actually pretty shitty considering the level of instrumentation that is on the market these days.

Now, here's where it gets really crappy. Over 160KPH the instrument could have an increasing accuracy error so at 180KPH it could be out as far as +/- 9% and at 200KPH it could be +/-12%.

There are all hypothetical numbers of course but it is entirely possible for them to be close. That is why whenever I have seen people post comments about them doing 140MPH in their Si/SiR I honestly don't believe it. The speedometer is going to be off quite a bit and when the Si/SiR hit the market it was clocked using a radar gun at 128MPH. Radar guns are much more accurate than a speedo.

So, SweetEBPSi, there is no doubt that your speedo can be easy off that much when you are comparing it to another car. The chance of Honda changing it for you are slim because that also means your odometer has to go as well. They are very liberal with the speedo accuracy so as not to mess with your odometer unless it is really far off. It's a whole ordeal they go thru when an odometer needs to be replaced.

 

[just chillin]

The speedometer is one of the most inaccurate instruments on the face of the planet. Honda's accuracy specification is +/- 5%. In addition to this fact, one thing they never tell us is that there is a range of accuracy involved with any instrument.

What that means is that the +/- 5% will only apply to a specific range of measurement. So for example a speedometer could be ranged for 0 to 160KPH. Outside of this range manufactuers don't really care what it reads anymore because you are undoubtedly over the limit and accuracy doesn't matter to them.

Running a hypothectical, at 160KPH you could potentially be reading a swing of 16 KPH. So anywhere from 152 to 168 KPH could be your actual speed and that would be considered normal error. It's actually pretty shitty considering the level of instrumentation that is on the market these days.

Now, here's where it gets really crappy. Over 160KPH the instrument could have an increasing accuracy error so at 180KPH it could be out as far as +/- 9% and at 200KPH it could be +/-12%.

There are all hypothetical numbers of course but it is entirely possible for them to be close. That is why whenever I have seen people post comments about them doing 140MPH in their Si/SiR I honestly don't believe it. The speedometer is going to be off quite a bit and when the Si/SiR hit the market it was clocked using a radar gun at 128MPH. Radar guns are much more accurate than a speedo.

So, SweetEBPSi, there is no doubt that your speedo can be easy off that much when you are comparing it to another car. The chance of Honda changing it for you are slim because that also means your odometer has to go as well. They are very liberal with the speedo accuracy so as not to mess with your odometer unless it is really far off. It's a whole ordeal they go thru when an odometer needs to be replaced.

right now. some dude on this board thinks he went a *speedo* indicated 150 mph in his gsr and cant' understand that speedo's are unaccurate, especially at that speed.

 

[SweetEBPSi]

Thanks all for your help. Now I have a question about gauge faces. Granted I'm still deciding which ones to put in, either the indiglo or reverse indiglo, what is the best way to install new gauge faces without completely making the gauge needles inaccurate? Also, if I get teh reverse indiglo gauges, what can I do to make the needle to show/light up at night? I have heard that at night they are a bitch to see.


Pauly

 

[Maniac]

right now. some dude on this board thinks he went a *speedo* indicated 150 mph in his gsr and cant' understand that speedo's are unaccurate, especially at that speed.

I think if you worked out the gearing via math you would find that his top end is going to be about the 130MPH same as our cars are. If I am not mistaken the GSR and the Si/SiR have the same tranny.

The only way he could pull 150MPH is if he was being towed by an Indy car, or if he had forced induction and changed his gearing.

I think the top end of an S2000 is around 150mph and I doubt very much his GSR can keep up with one of them babies.

 

[just chillin]

I think if you worked out the gearing via math you would find that his top end is going to be about the 130MPH same as our cars are. If I am not mistaken the GSR and the Si/SiR have the same tranny.

The only way he could pull 150MPH is if he was being towed by an Indy car, or if he had forced induction and changed his gearing.

I think the top end of an S2000 is around 150mph and I doubt very much his GSR can keep up with one of them babies.

it sounds like you're trying to argue with me, even though you're saying the exact same thing I did .

 

[Maniac]

it sounds like you're trying to argue with me, even though you're saying the exact same thing I did .

I am agreeing. Bring me the hard proof his GSR did that speed and I will believe you. Otherwise forget it.

Some of the articles I've read put FI Preludes at 150mph but never a GSR. Preludes I can believe because they are geared different from a GSr or an SiR.

Do the math and I don't think there is any arguring to be done. If don't want to do the math let me know and I have a few engineering buddies that will dig your friend a hole that will be hard to climb out of.