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Speedometer accuracy issues again....

Posted: Tue Feb 28, 2006 5:30 am
by douglas vincent
On the drive back down from Aberdeen Washington, I was following Ralliteck in a 60 mph zone.

He was driving about 60 mph exactly and EVERYBODY was passing us. I called him up and asked him was his speedo read. 65 mph.

hmmm..... 5 faster than mine.

I asked him what his tachometer read. Withen 100 or so of mine.

hmmmm....and mine is about 150 faster than the Perfect Power reads.

So I once again started timing myself as I drove down the freeway in cruise control.

62 seconds to go a mile at 60mph (real speed = 58 mph)

50 seconds to a mile at 75 mph (real speed = 72 mph)

46.5 seconds to go a mile at 80 mph (real speed = 77.5 mph)

So it seems my speed is off about 2-3 mph (or 3%). Rallitecks speedo is off ALOT more, about 7 mph, or 6-7%.


I am using stock WRX rims and RE92s. Ralliteck is using some 17" with low profile tires that are almost 1" smaller in circumfrence.

So after doing this again, I once again through serious doubt onto those claiming to have really truly cross your heart and die gone 130-140 in our cars if they are using anything smaller than 16" rims and/or weird giant truck style tires.

Posted: Wed Mar 01, 2006 5:30 pm
by JasonGrahn
Tacoma Speedometer can recalibrate that for you.

Posted: Wed Mar 01, 2006 7:28 pm
by Legacy777
Jason,

What do they do to recalibrate the speedo on a mechanical speedo setup?

Posted: Wed Mar 01, 2006 7:37 pm
by JasonGrahn
Dunno, but I bet if you called they could tell ya at least a little bit. They've got all sorts of tricks.

http://tacomaspeedometer.com/

Posted: Thu Mar 02, 2006 12:31 am
by evolutionmovement
Going by the police radar speed display signs, my speedometer was most accurate with my 15's (dead on), but the 16's are close and still more accurate than the OEM 14's.

Posted: Thu Mar 02, 2006 6:52 am
by douglas vincent
I was the worst on my 14" rims. 10% off. 100 was truly only 90.

Posted: Thu Mar 02, 2006 7:49 pm
by Legacy777
Called them up.

Talked to Mark. (Seemed like a really knowledgable & nice guy)

What they do is take a speed reading on a dyno at 60 mph. Take that, and build an adapter, which is about 3" in length to go in line on your cable. Parts wise, he said the adpater is about $60, and cable stuff is around 30.

If they were to do the whole thing, including the dyno stuff I think he said around 150-170.

If I were going to do, I'd have to get a dyno reading down here in Houston @ 60 mph and send him that information as well as my speedo cable for him to modify.

Once I pick the size tires I want to use, I'll probably look into doing this.

Posted: Thu Mar 02, 2006 8:14 pm
by wiscon_mark
sorta off topic here...all 1st gens have speedo cables then? They're not electronic?

Posted: Tue Mar 07, 2006 8:36 pm
by Legacy777
Well....they have speedo cables, but the speedo is electronic. The cable drives a speed sensor....not the speedo directly.

Posted: Tue Mar 07, 2006 10:54 pm
by scottzg
whats the point in regearing it? The speedo jumps at 80 and 90 mph anyway. You have to watch the tach to have an accurate speed reading.

Posted: Tue Mar 07, 2006 11:26 pm
by Legacy777
I asked the guy about the speedo reading at higher speeds....and he said regearing it would fix it across the entire range. I don't know if was intending/implying it'd be accurate at 100 mph.

Posted: Wed Mar 08, 2006 12:34 am
by wiscon_mark
Legacy777 wrote:Well....they have speedo cables, but the speedo is electronic. The cable drives a speed sensor....not the speedo directly.
Interesting. I wonder if the OBDI Imprezas also had a cable, because my OBDII Legacy is all electric wiring.

Posted: Wed Mar 08, 2006 1:06 am
by Legacy777
wiscon_mark wrote:
Legacy777 wrote:Well....they have speedo cables, but the speedo is electronic. The cable drives a speed sensor....not the speedo directly.
Interesting. I wonder if the OBDI Imprezas also had a cable, because my OBDII Legacy is all electric wiring.
I'm pretty sure this is how it works. Vikash would probably be able to confirm whether I'm right or wrong.

I would probably venture to say the OBD1 imprezas are the same as the OBD1 legacies.

Posted: Wed Mar 08, 2006 4:02 pm
by vrg3
Actually, I think all Imprezas use the electric setup, with the VSS threaded into the transmission. I could be mistaken though.

Posted: Wed Mar 08, 2006 5:43 pm
by BAC5.2
I know the 1994 WRX had the VSS threaded into the transmission.

Posted: Fri Mar 17, 2006 2:36 am
by JuhaKankkunen
My 93 Legacy tell me in the spedometer 160 km/h (100 mph) when i was really driving at 150 km/h (93.75 mph). Can anybody tell me if there is a solution for that??? Thanks.

Posted: Sun Mar 19, 2006 6:05 am
by Legacy777
Yes....the website posted above can fix that.....