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YOUR RESEARCHspeedo error
Leading reported evidence
Check speedo
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Performed · outcome unconfirmed
(The trip odometer worked ok.) I brought the car to the dealer and the stupid dealer checked the speedo and because it read ok deemed the odometer ok as well.
Leading evidence: 'Check speedo' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust reading back' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
Simultaneous with this I reset my Garmin GPS's trip to zero.
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Performed · outcome unconfirmed
Best bet is to get a good GPS handheld or NAV unit (I've used both having a NAV unit now) or something to connect to the OBD2 port and view your vehicle's speed in real time to 'calibrate' your car's speedo.
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Suggestion · Original poster
On one of those cable shows they hit 206 in a GT3 RS but had to adjust the reading back to 198 mph.
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Performed · outcome unconfirmed
(The trip odometer worked ok.) I brought the car to the dealer and the stupid dealer checked the speedo and because it read ok deemed the odometer ok as well.
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Suggestion
I went along with this for a while but since I was clean (of course) and had nothing to fear even if I was pulled over I sped my car up to the limit and pulled out in the fast lane and the black car then pulled over into the slow lane ahead of the other car and in not too much time I left both the black car and the other driver and his car behind me.
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Suggestion
The speed error will vary depending upon speed and can change a bit over time as tires wear and if so then when you replace tires or possibly if you switch to a different tire.
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Suggestion
The speed error will vary depending upon speed and can change a bit over time as tires wear and if so then when you replace tires or possibly if you switch to a different tire.
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Suggestion
Very early in my 02 Boxster's ownership I took a 200 mile drive after having reset the car's trip odometer to zero and at the same time the odometer flipped over a new mile.
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Performed · outcome unconfirmed
Best bet is to get a good GPS handheld or NAV unit (I've used both having a NAV unit now) or something to connect to the OBD2 port and view your vehicle's speed in real time to 'calibrate' your car's speedo.
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49 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Outcome without a verified action link
The "only blowin the carbon out officer!" defense actually worked for me once before a judge.
I know 911's have some speedometer error, when my 996 tells me I'm going 100 how fast am I really going? Is the error shared by all 911's or does it vary from model and year ect?
And it is also 4 mph at 50, 60, 70, and 80. You have an electronic speedo that has a built in error from the factory of about +4 mph at most speeds.
I admit, I have not checked it with my GPS at speeds over 100 mph.
However, does 4 mph
really
matter at any speed? Only if you are driving through radar traps at the speed of heat.
If you know that:
A. You have 4 mph give to the plus side, and
B. Police generally won't give you a ticket for doing only 4 mph over the posted limit, then
C. You might assume that driving an indicated +8 mph over the posted speed limit
should
be
safe
... unless,
D. You are driving a Porsche,...
E. Particularly if it is red, or a convertible with the top down.
My escort 8500 sniffs those mirror shade wearin jack booted party poopers long before they can get a gun on me! (famous last words).
The "only blowin the carbon out officer!" defense actually worked for me once before a judge.
My gps says -3 mph too. Never checked at 100, but even when the speedo says 30 I'm going 27...it drives people in my neighborhood nuts since I won't go over 30 on the speedo.
+3 or is it 4. Checking my GPS, I'm at +4 as well. As far as the Escort vs. the V1, I thought long and hard, did a lot of reading, and bought the escort 9500xi. Great detector, little falsing. It is an up to date detector. The V1 is old technology.
Larry
i read 2 mph higher than gps at all speeds i have looked at (probably 90 or so). also checked it against fixed/unmaned police radar trailers in my town. same 2mph higher than the radar trailer says.
Based on the responses so far we can conclude:
A. Most if not all 996's speedo's read high.
B. The degree to which they read high probably is related to the year, model (C2 vs C4) and
C. The wheel and tire combinations giving various rolling circumferenci (just made that up as the plural of circumference).
D. Radar detector performance is totally subjective to how badly you have to justify/defend your purchase choice and price.
E. Radar guns in police trailer signs are fun to play with (until you find out that they actually also transmit a signal to a properly equipped local police car receiver, with a crosshair photo of the car it is locked onto at the moment).
Oh, yes, a radar detector thread is just about as universal as an oil thread.
I was driving down a 4 lane divided blvd very late (or was it very early) in the night (morning.) My 9500 went off, and as I always do, I tromped on the brake to get me down to speed limit. I had just finished passing a crotch rocket, and he went zipping past me as I braked. He slowed down as well, and for the better part of a mile, he paralleled me.
Then we both turned right onto another highway, and I was ready to turn left into the parking lot. The rocketeer twisted around on his seat to see what was following us (if anything). Just then, I turned left, and he accelerated. Right behind me was a PD SUV accelerating past me towards the crotch rocket.
I never figured out why he paced me for so long and then took off. Was he thinking that he was going to outrun the SUV PD Car? Didn't he recognize that this was a police car, and he thought I was just driving slowly for the hell of it? Ah, yes, we will never know. But my Escort 9500ix had saved my butt again, just as it has done dozens of times. Thanks, I don't have a real need to justify my purchase to you guys. I have already justified it to myself 4 - 5 times a week over the 3 months that I've had it.
larry
IIRC, plugging into the OBD-II port, the "Vehicle Speed" parameter gives you the correct (higher) reading compared to the speedo. (My memory is a little hazy, so i could easily be wrong)
R
My car is 4mph faster.
I believe this is so you can change tire sizes and never read a speed slower than you are going.
As for the 8500 vs 9500 I beleive from my research (i'm looking to upgrate my old K40) uses gps to remember false readings. But I beleive the range is equal for both detectors. So if you live someplace that you get lots of false readings consider the 9500. I believe it is the best on the market right now. But the 8500 is a couple hundred $ cheaper. FWIW I'm leaning toward the 8500 based on the places I drive.
Best bet is to get a good GPS handheld or NAV unit (I've used both having a NAV unit now) or something to connect to the OBD2 port and view your vehicle's speed in real time to 'calibrate' your car's speedo.
The speed error will vary depending upon speed and can change a bit over time as tires wear and if so then when you replace tires or possibly if you switch to a different tire.
I've calibrated/characterized my cars' speedos well enough if conditions permit I'll pass a police or highway patrol car that is going just under the limit with no fear. And so far I've never been stopped.
Sincerely,
Macster.
I don't encounter them too often, but the last one I remember was a CHP on I-580 going up and over the 'mountains' into Dublin CA. For reasons known only to the officer his car was traveling about 60mph (5mph under the posted limit).
No light bar lights on. No weaving like they do during a traffic break. The road ahead looked ok to me. So I put the car's speed at a true 65mph and drove on past.
Some years ago I encountered what I thought was a state police car on I-40 crossing the Texas panhandle east of Amarillo TX. It looked 'official' (Crown Vic) and was all black but looked like some kind of plains clothes car to me. No light bar on the roof.
Another driver in another car and I had been making 'good' time until the black car showed up. Of course we both slowed down to the limit. I suspected the black car was a ground unit for a bear in the air speed trap but the black car never put on what I suspected was an inside the car light bar nor made any signs of wanting either of us to pull over.
After some time both the other driver and I ended up with our cars in the slow lane with me behind the other driver and his car.
The black car then slowly, ever so slowly, came up in the fast lane. It paced my car a bit then moved up to the other driver's car.
When the black car got a bit ahead of my car I spotted the 'Interdiction' lettering on the back.
The black car's speed slowly dropped and the driver of the car ahead of mine slowed his car's speed to match the speed of the black car.
For a bit of time (it seemed like ages) all 3 cars moved at something under the posted limit.
I went along with this for a while but since I was clean (of course) and had nothing to fear even if I was pulled over I sped my car up to the limit and pulled out in the fast lane and the black car then pulled over into the slow lane ahead of the other car and in not too much time I left both the black car and the other driver and his car behind me.
As long as I could I sneaked a glance in the rear view mirror expecting to see the other driver and his car pulled over but I never saw this and since I was now making the speed limit the other cars were soon out of sight.
Sincerely,
Macster.
Not necessarily.
Very early in my 02 Boxster's ownership I took a 200 mile drive after having reset the car's trip odometer to zero and at the same time the odometer flipped over a new mile. Simultaneous with this I reset my Garmin GPS's trip to zero.
After 200 miles the car's trip odometer and the Garmin's distance traveled differed by just 0.2 of a mile.
I can't remember now which was ahead of the other, but the difference was so small that in 50K miles (warranty miles) the error would amount to just 50 miles.
Now some cars (not Porsche though) have an odometer error that not only results in the car gaining miles faster than actual but this also affects miles penalties for leased cars.
Sincerely,
Macster.
interesting info. Thanks! I was under the impression it was higher than just 4-5. On one of those cable shows they hit 206 in a GT3 RS but had to adjust the reading back to 198 mph.
You can!
This was a big topic on the boards when the Boxsters first came out in '97 or '98. The dealer can reprogram your speedo to be accurate. My friends at the dealer did this to my wife's '99 Boxster 9 years ago. I have checked it with my GPS and it's dead on.
I never had my 996s recalibrated, I may have my Turbo done if it ever goes to the dealer.
The "analog" speedo, the digital speedo, the odometer, and the trip odometer are all electronically operated. Unlike the early days in cars, there is no actual mechanical connection. The pick-up sends its signal to the computer, and the computer decides what signal(s) to send to the various displays. They can in fact be programmed to work together or seperately at different ratios. It is all done by computer and programs and coding.
Thus, it is entirely possible to to have an "error" programmed into the digital speedo readout, but not the "analog" gauge (there is nothing analog about it but the moving needle). A program is created for each readout. So "flashing" the computer to correct the imbedded errors is only possible if you are a real major computer geek who knows how to work through the actual programming to find the codes to correct, and what the codes should actually be. Think about the levels you would have to work through. Nobody who does this would take the time to do it for such little reward.
And the small size of the "analog" speedo makes it impossible to really see those details of speed, which is easily seen by watching the digital readout. Then there are also external factors like paralax error...
Also, 4 mph error does not equate to 4% error. Depends on your current speed. 4 mph at 50 mph equates to 8% error. And the trip odometer and non-resettable odometer can have a totally different factor or even no error factor vs the speedo's.
As for GPS accuracy, the military depends on the pinpoint accuracy of the same satellite-based transmitters as your hand-held Garmin...
And sea-level navigation through treacherous inlets such as those found in the Carribean Islands is now far less dangerous because of those same transmitters.
And the WAAS scrambling and error programming of a decade ago has long since been turned off or cancelled out by the programming in newer GPS's.
I have the latest version of a PST2 and there are no speedometer calibrations possible within the unit. I have also flashed my DME with the map that comes with the final version of PST2 software version #24 (reported by several posts to be one of the "software" fixes available at the dealer to calibrate the speedometer).
I've heard the "rumor" about correcting the speed readout before, but have not seen any evidence it can be actually done.
I do not believe there is a speedometer calibration function within PIWIS either, but could be wrong.
Perhaps it is model year dependent and what type of instrument cluster version one has, but at least on the 1999 car I would be hard pressed to find evidence it is possible to adjust the speedo without doing modifications outside of what is "sanctioned" or "available" by the dealer/Porsche.
Using a motorsports datalogger/precision GPS I noticed at 30mph the error is 3mph, 4mph at about 40-70 and then 5mph above that. UK 99 C2 new tyres.
This is consistent with the local radar units that show you your speed as you approach them.
Based on my observation/confirmation at least with my Boxster while the speedo reads optimistic the odometer does not have the same optimism so I would have to say the speed display and the speed displayed on the dash and the odometer and distance traveled are not connected, not directly. I see no reason why Porsche would do this for the Boxster and not for every other car it makes.
Sincerely,
Macster.
Porsche has deliberately built overstatement into the speedo. They are very sensitive about this, and will NOT allow their dealers to correct it. We need to start a campaign to embarrass the company into behaving responsibly.
Both my Targa and my Boxster read 3 mph fast
IIRC, it has something to do with German law and liability that a speedo must not read slower than true speed so they make them read a little fast just in case.
My VW's also read 3-4 mph fast
Doesn't bother me any. As soon as I confirmed to my satisfaction there was no error with the odometer which would or could affect the mileage and result in less warranty coverage I just adapted to the fact that my Boxster's speedo read between 4 and 5 miles optimistic.
I can't recall now if my 2008 Cayman S's odometer was optimistic but my 2003 Turbo's odometer is just 2mph optimistic.
Also, it could be worse. My '96 Mustang GT odometer would stick and after over 15 miles of driving would gain only a few miles. (The trip odometer worked ok.) I brought the car to the dealer and the stupid dealer checked the speedo and because it read ok deemed the odometer ok as well. I found out much later there was a recall on this the lube IIRC used in the speedo gearing dried and caused the odometer counter to not turn properly.
But the car was still under warranty and the "error" was in my favor so I said to heck with the stupid dealer and lived with the problem. But that was my last Ford.
I hope you guys noticed that the Poster with 3 posts resurrected a 4+ year old thread that has already been beaten to death. Plus he drives a Cayenne. I am not embarrassed by Porsche...ever!
