Speedometer accuracy, spot on.

CFar · 03-21-2008, 05:03 AM

For those that care, I finally had the chance to compare actual speed to my speedo and was surprised at how accurate it was. Using a calibrated radar which was placed at the outside "apex" of a kink on a local street, I drove straight at the radar and registered 50 mph at 50 indicated on my speedo.

Maybe its the new electronic gauges, but what ever it is I'm happy to know how fast Im going now. My previous cars up until now have been off by as much as 5 mph at highway cruising speeds.

Cheers,
Chris

chmura · 03-21-2008, 06:07 AM

I think the faster you go the more the speedo is off. So when you are hitting 130mph you are actually not going that fast.

baneonrt · 03-21-2008, 06:08 AM

For those with nav you can enter a screen that shows you coordinates, which satellite you are using and your speed. I haven't yet remembered to open that screen before starting to drive but it should work well to compare your speedo to.

Steve

serendipity · 03-21-2008, 06:10 AM

Quote:

Originally Posted by baneonrt

For those with nav you can enter a screen that shows you coordinates, which satellite you are using and your speed. I haven't yet remembered to open that screen before starting to drive but it should work well to compare your speedo to.

Steve

That speed is from the VSS, not the GPS.

If you take a handheld GPS, you can compare the speedo's accuracy.

trevoro · 03-21-2008, 06:18 AM

Mine is right on as indicated by radar also.

T

CFar · 03-21-2008, 08:34 AM

Quote:

Originally Posted by chmura

I think the faster you go the more the speedo is off. So when you are hitting 130mph you are actually not going that fast.

Speedos frequently indicate error in percentages. For instance, if you have a 10% error at 10mph indicated, you would be either going 9 or 11mph depending on which side of error youre favored on. If you were to have that same 10% at 100mph, you would actually be going 90 or 110mph.

When I ran by the radar (4x), I tried 35, 40 and 50. All of which were spot on. Now I imagine that if I were to crest 100 there will understandably be some small amount of error, but certainly not the 5% in my old cars. Maybe .5-1%. Not bad.

ploney · 03-21-2008, 08:42 AM

I'll have to double check mine with my smaller than stock tires against my MaxQdata logger on the highway.

255-35-18's

I wonder if the ecu has the ability to adjust for smaller size tires??? I doubt it, but that would be cool.

**Josh@EpicSpeed** · 03-21-2008, 09:16 AM

Mine is spot on compared to the speed reading from my Garmin Nuvi GPS. My '07 Miata is also accurate as well. These are the first two cars that I've seen with accurate speedos, so I assume that the manufacturers don't have to do the 10% thing due to Europ legislation any more.

**Digitalfiend** · 03-21-2008, 09:25 AM

That's good to hear. The old cars were horribly inaccurate, even at 60 km/h.

baneonrt · 03-21-2008, 09:31 AM

Quote:

Originally Posted by serendipity

That speed is from the VSS, not the GPS.

If you take a handheld GPS, you can compare the speedo's accuracy.

Can you confirm that you are correct? It seems to me that this screen is just the basic GPS data that is collected/calculated. There is no reason for it to come from the vehicle systems.

Steve

brantdw · 03-21-2008, 10:01 AM

I have an older Outback and 06 STI. I use a Tom Tom and the new Escort 9500i. Both of these tell the speed of your car. Both of them are consistanly 5mph off at almost any speed. Now I know why everyone in an outback is so Friggin slow.

Rootus · 03-21-2008, 10:17 AM

The 04-07 ECU was spot on, but the gauge displayed 2 or 3 mph high. It was so consistent that I'm pretty sure Subaru spec'd it that way.

midnit · 03-21-2008, 11:03 AM

Thanks for the news CFar... Currently in my05 anything over 40mph seems to be about 5mph off for me. Anything >100 is about 10+ off.

With Fairfax cops being how they are, I hate not knowing exactly how fast I'm going.

**Turninconcepts.com** · 03-21-2008, 11:52 AM

Quote:

Originally Posted by serendipity

That speed is from the VSS, not the GPS.

If you take a handheld GPS, you can compare the speedo's accuracy.

The VSS in the older models was actually correct, but the gauges were wrong. I verified this on our 04 a few years ago with a hand held gps device. The speed is 4mph off at 80; hence the speedo is reading 84 when you are traveling 80.

I have compared my 08 at 80 against the speed read out from the AP and from my D3 and both indicate the speed to be only about 1mph high at 80.

Iguana · 03-21-2008, 12:05 PM

I'm glad that my speedo reads high. That way, I'm less likely to be actually speeding.

03-21-2008, 05:03 AM	#1
CFar Professional STI Driver Location: NOVA Posts: 498 Join Date: Jun 2006 Trader Rating: (1)	Speedometer accuracy, spot on. For those that care, I finally had the chance to compare actual speed to my speedo and was surprised at how accurate it was. Using a calibrated radar which was placed at the outside "apex" of a kink on a local street, I drove straight at the radar and registered 50 mph at 50 indicated on my speedo. Maybe its the new electronic gauges, but what ever it is I'm happy to know how fast Im going now. My previous cars up until now have been off by as much as 5 mph at highway cruising speeds. Cheers, Chris This ad is not endorsed by this member. Please register or login to hide this ad.

03-21-2008, 06:07 AM	#2
chmura STI Driver Car: 07 Lexus IS250 Fav Mod: Future 09 STI Owner :) Location: Orange County, CA Posts: 206 Join Date: Dec 2007 Trader Rating: (0)	Re: Speedometer accuracy, spot on. I think the faster you go the more the speedo is off. So when you are hitting 130mph you are actually not going that fast.

03-21-2008, 06:08 AM	#3
baneonrt Junior STI Driver Car: WRB '08 WRX STi Fav Mod: Cobb AP Stg1 Location: W Sacto Posts: 100 Join Date: Dec 2007 Trader Rating: (0)	Re: Speedometer accuracy, spot on. For those with nav you can enter a screen that shows you coordinates, which satellite you are using and your speed. I haven't yet remembered to open that screen before starting to drive but it should work well to compare your speedo to. Steve

03-21-2008, 06:18 AM	#5
trevoro Junior STI Driver Car: Silver 08 STI Fav Mod: none...yet Location: Sheridan Posts: 78 Join Date: Jul 2006 Trader Rating: (1)	Re: Speedometer accuracy, spot on. Mine is right on as indicated by radar also. T

03-21-2008, 08:42 AM	#7
ploney STI Driver Car: White 08 STI Fav Mod: Volk RE30's and 255-35 Dunlop Z1's Location: Redondo Beach Posts: 257 Join Date: Sep 2006 Trader Rating: (0)	Re: Speedometer accuracy, spot on. I'll have to double check mine with my smaller than stock tires against my MaxQdata logger on the highway. 255-35-18's I wonder if the ecu has the ability to adjust for smaller size tires??? I doubt it, but that would be cool.

03-21-2008, 09:16 AM	#8
Josh@EpicSpeed Authorized Vendor Car: '08 RallyCross STI Posts: 23 Join Date: Mar 2008 Trader Rating: (0)	Re: Speedometer accuracy, spot on. Mine is spot on compared to the speed reading from my Garmin Nuvi GPS. My '07 Miata is also accurate as well. These are the first two cars that I've seen with accurate speedos, so I assume that the manufacturers don't have to do the 10% thing due to Europ legislation any more.

03-21-2008, 09:25 AM	#9
Digitalfiend Super Moderator Car: 08 DGM STI Fav Mod: My wife :) Location: Brooklin, Ontario Posts: 5,144 Join Date: Oct 2003 Trader Rating: (0)	Re: Speedometer accuracy, spot on. That's good to hear. The old cars were horribly inaccurate, even at 60 km/h.

03-21-2008, 10:01 AM	#11
brantdw Amateur STI Driver Car: Blue 07 STI Location: Beaverton oregon Posts: 16 Join Date: May 2007 Trader Rating: (0)	Re: Speedometer accuracy, spot on. I have an older Outback and 06 STI. I use a Tom Tom and the new Escort 9500i. Both of these tell the speed of your car. Both of them are consistanly 5mph off at almost any speed. Now I know why everyone in an outback is so Friggin slow.

03-21-2008, 10:17 AM	#12
Rootus S204 Racer Location: Africa Posts: 2,742 Join Date: Sep 2005 Trader Rating: (1)	Re: Speedometer accuracy, spot on. The 04-07 ECU was spot on, but the gauge displayed 2 or 3 mph high. It was so consistent that I'm pretty sure Subaru spec'd it that way.

03-21-2008, 11:03 AM	#13
midnit Silver Member Car: 08 Aspen White STI Location: Northern, VA Posts: 591 Join Date: Feb 2007 Trader Rating: (0)	Re: Speedometer accuracy, spot on. Thanks for the news CFar... Currently in my05 anything over 40mph seems to be about 5mph off for me. Anything >100 is about 10+ off. With Fairfax cops being how they are, I hate not knowing exactly how fast I'm going.

03-21-2008, 12:05 PM	#15
Iguana Spec C Club Car: 06 Aspen White STI Fav Mod: Defi's Location: Northern California Posts: 1,318 Join Date: Apr 2006 Trader Rating: (0)	Re: Speedometer accuracy, spot on. I'm glad that my speedo reads high. That way, I'm less likely to be actually speeding. This ad is not endorsed by this member. Please register or login to hide this ad.