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Old 07-06-2008, 06:34 PM   #1
Drake13
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2004 STI
WRB TBE, TiaL 44mm EWG

Default Speedometer off.. need help!

Hey fellas I have a 04 STI and noticed a couple of weeks ago my speedometer is quite off. More like 5-7mph slower then what i'm actually doing. I passed one of those radar traps on the road doing around 60-62 and the radar reflected 55-57, speed limit being 55. I was the only one on the road. Anyways any ideas where to start so I can correct this? I've always wondered why people were flying by me while I have the cruise set at the speed limit... now I know why

Side note: stock tires / rims.. everything
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Last edited by Drake13; 07-06-2008 at 06:48 PM.
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Old 07-06-2008, 08:47 PM   #2
b0nd18t
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2007 STI
Blouch Dom3

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mines reads about 2mph faster than im actually going, noticed it right away after buying the new car. subscribed.
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Old 07-06-2008, 09:03 PM   #3
GreenLantern
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most cars come stock with the speedo reading anywhere from 3-5mph higher than your actually going. if it really bothers you ride on something with a larger diameter (rims and tires). My 07wrx was about 3-4 mph over my actual speed stock and i got 18's with 235/40 tires on em and now i seem to be dead on with my speedo on actual speed.
good luck
-GL
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Old 07-07-2008, 11:14 AM   #4
skingfreak
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^^^What he said, with stock 16" on my WRX it read fast, with 17's and beafy tires it reads DEAD on GL
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Old 07-07-2008, 12:56 PM   #5
Drake13
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2004 STI
WRB TBE, TiaL 44mm EWG

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Well I guess this is only gives me two things to do.. reason for buying new rims and tires or take it to the dealership to get looked at?
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Old 07-07-2008, 12:59 PM   #6
growling_boxer
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2007 STi

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i think the STi is little farther off than the average car because it is a performance car. many manufacturers do the same thing. i believe the max speed shows up as 153, but it is actually 147. I'm not sure how much it is scaled differently. I went up to 245/40R18s on mine, and the speedo still reads faster than i am going. i have a scangauge on my column, and it is calibrated to my real speed. with the bigger tires i'm still about 2mph off at 80.
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Old 07-07-2008, 01:47 PM   #7
Drake13
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WRB TBE, TiaL 44mm EWG

Default

Thanks for the input.. i've done several searchs on here and find it hard to believe no one has brought up this subject. I know changing the tires/rim size does. but just plan stock it is off. I read one internet artical that mentioned if your speedometer is off there is a good chance your odometer is off as well due to it using the same sensor....??? not sure how true that is, anyone?
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Old 07-07-2008, 01:53 PM   #8
fullerton
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Quote:
Originally Posted by Drake13 View Post
Thanks for the input.. i've done several searchs on here and find it hard to believe no one has brought up this subject. I know changing the tires/rim size does. but just plan stock it is off. I read one internet artical that mentioned if your speedometer is off there is a good chance your odometer is off as well due to it using the same sensor....??? not sure how true that is, anyone?

pretty sure the ecu reads the correct speed, the speedometer just displays it incorrectly.

question is, which source does the odometer use?
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Old 07-07-2008, 04:43 PM   #9
Badler
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Quote:
Originally Posted by Drake13 View Post
i've done several searchs on here and find it hard to believe no one has brought up this subject?
Been covered millions of times. SAE +/-5% variance acceptable on cluster. These are mass produced gauges, far from accurate. Beating a dead horse. The speedo and odometer read off seperate inputs, allegedly.
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Old 07-07-2008, 05:08 PM   #10
ProdriveDreams
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Quote:
Originally Posted by aaronmsadler View Post
Been covered millions of times. SAE +/-5% variance acceptable on cluster. These are mass produced gauges, far from accurate. Beating a dead horse. The speedo and odometer read off seperate inputs, allegedly.
you are correct as far as +/-% being acceptable, it might even be a bit higher than that. Either way there is only one VSS in the car unless you count the ABS wheel sensors which are not used as a VSS in our cars. The way to check if your odo is accurate is to check what speed your ECU sees. the speed your ECU sees often does not match the speedometer, this is more a failure of the gauge itself than innacuracies in the system.
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Old 07-11-2008, 03:51 PM   #11
ChuiSTi
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i do believe that the ECU reads the correct speed of the vehicle. I have a defi VSD (heads up display) and it displays a speed about 5mph slower than the speedo when i'm going around 70-80mph. Also when i was getting tuned, i asked the tuner and he said the vsd was showing the correct speed (directly connected to ecu) as opposed to the speedo.
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Old 07-15-2008, 12:18 AM   #12
Spootypuff
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My sti reads about 3-5 mph faster than its actually going. I don't mind tho cuz it keeps the cops away
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