Sti gauge reading off - Subaru WRX Forum
 
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#1 Old 01-16-2012, 05:42 PM
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Sti gauge reading off

The setup: 03 wrx wagon, tried to strip the green off the gauges, broke the needle, had some extra money lying around so i purchased an STI gauge cluster off a 2004, installed it just fine, and that's the end of that. Fast forward 3 months, I let my dad take my car out for a cross state drive, he ends up calling me saying that at, using a GPS to test mph, when my gauge reads 85 i'm actually going 80. I had assumed that with the sti gauge going to 160 mph, and the wrx only going to 140, that the car would adjust itself. Is this completely off base ad my speedometer only goes to 140, but that is distributed across the 160 scale?
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#2 Old 01-16-2012, 06:31 PM
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it shoud be dead on as an 04 cluster is a direct swap for the most part, what size tire are you running?

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#3 Old 01-16-2012, 06:42 PM
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Stock rims, 205/55/16 rubber.
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#4 Old 01-16-2012, 06:51 PM
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have you confirmed that it's off with more than one GPS device?

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#5 Old 01-16-2012, 07:23 PM
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with two different gps devices, and with my buddys wrx on cruise at 90. Now would the fact i'm one of the few kids racing the auto out there make a difference?
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#6 Old 01-16-2012, 07:29 PM
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yes the auto's require some computer tweaking IIRC

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#7 Old 01-16-2012, 07:31 PM
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Something i could call my buddy and we could RomRaider away?
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#8 Old 01-16-2012, 08:19 PM
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Nope, it's more of an FYI for yourself now.

I have the same situation - in the summer I run shorter tires so my gauge reads high, in the winter they're stock so it reads normal. The only way to get it to read correct is to dig into the trans as far as I know.

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#9 Old 01-16-2012, 08:46 PM
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Well all the drivetrain stuff is stock, the only difference is its an STI cluster, which as we all know is stick by nature, into an automatic.

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Originally Posted by RcrsWetDream View Post
The only way to get it to read correct is to dig into the trans as far as I know.
So here's my understanding of your post, correct me if i'm wrong. You're saying that the speedometer gathers its current speed via some probe(or what have you) in the transmission, and the standard has a different way of gathering speed data so it can adjust?

once again, not trying to sound offensive in anyway, just trying to understand how this all works.
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#10 Old 01-17-2012, 03:37 AM
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Speed is generally obtained from a gear in the transmission. I don't know Subarus specifically, but if the auto and manual use different gear sizes, then your readings will be off. Changing tire sizes as mentioned above would be one way of bringing the gear ratio in sync.

Sorry I can't be more specific.
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#11 Old 01-17-2012, 07:32 AM
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with the automatics you can adjust the spedo output using the trans controller, I forgot the company that reprograms them

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#12 Old 01-17-2012, 09:53 AM
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Speedo's ain't that accurate. 85 vs 80 is as correct as you should expect. Tire wear, for example, can have a major factor. All seasons usually run about 13/32" new. If you run then down to 3/32", just for example, you've lowered your total tire diameter by 20/32". That's substantial on a car like an Impreza with a 25" total diameter. The difference can be as much as 3%. That's just one factor in speedo readings, there are others.

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#13 Old 01-17-2012, 12:04 PM
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Get a cop to clock you one night. They would do it here.

As long as you can pry them away from the local Dunkin Donuts

Paul
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#14 Old 01-17-2012, 05:23 PM
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Mosc: almost new rubber at 8/32nds and the rubber brand new was only a 10/32nds tread depth (and my alignment and balance is good)


Quote:
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Get a cop to clock you one night. They would do it here.

As long as you can pry them away from the local Dunkin Donuts
Actually on my way home from my mechanic job, I got pulled for going 4 over because evidently the kids from the nearby high school think racing at 3 in the afternoon is cool, and track ready WRXs fit the profile of high school imbeciles. At least he clocked me at 54 when i was going 54 so my speedo is accurate there.

Last edited by mr mello; 01-17-2012 at 05:24 PM. Reason: Spelling
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