GDE Computer Tune Question (Speedometer Related)

Tiarnon · **Posted:** Mon Sep 10, 2012 9:10 pm

Just got my Eco tune in on Friday night. Fueled up Saturday at lunch break from work, filled up on lunch break today after a drive home and a drive back (one round trip) and got 33.8 mpg. My question is, does the GDE tune do anything to correct the speedometer inaccuracy? Before it was 4-5% off, so you had to correct the mpg calculations. And your speed. My main reason for wanting to know is simply so I don't get myself pulled over on my morning commutes.

For what it is worth, the tune is absolutely worth it just for the smoother throttle response, broader powerband, and just generally more well behaved. To give some background, I have got a very consistent 23.25 to 25.25 miles per gallon all summer depending on AC use. I drive 20 minutes @ 70ish mph, then drive another 15 minutes between 30 and 60 mph with a couple of stops. I will report my mileage over the course of a full tank of fuel later.

Main thing is, am I still going 71.5 when my speedo says 75, and 62 when my speedo says 65? Don't want to get the red and blue lights.

Edit: Also, anybody have a real life number to put on the mpg gain of removing the muffler and resonator and putting a straight pipe in between? 1? 1.5?

dgeist · **Posted:** Mon Sep 10, 2012 10:21 pm

On the muffler question, probably like 1 mpg, maybe 2. The biggest difference there was the change in drivability due to the lack of restriction (faster spool and longer drift on throttle-off). Also, it raises the high-center clearance a bit for off-road. Definitely worth the 100 bucks and hour at the muffler shop.

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CATCRD · **Posted:** Mon Sep 10, 2012 10:56 pm

GDE can't change your speedo accuracy because the rev/mile info is stored in the BCM, not the ECM that they program.

Tiarnon · **Posted:** Tue Sep 11, 2012 7:07 am

Thank you both for the answers!

Big Montana · **Posted:** Wed Sep 12, 2012 6:27 pm

What's the deal with the speedo? I have a Garmin, and my 05 has always been on. I've even driven by many of those police speed readers and they seem to indicate I'm ok. Is there a reason why some Jeeps are off and others are not?

ATXKJ · **Posted:** Wed Sep 12, 2012 8:19 pm

my best accuracy - compared to GPS - was with 245/75/16's
~ 5% bigger than stock and the speedo was dead on form most of the range.

(265/75 is on at 35-40 and off at 50 - and way off at 60-65)
stock was off everywhere.

use GPS - or measure mile markers

the police speed readers may or may not be accurate - depends on how often they calibrate and what frequency (speed) they calibrate at, if it's just for a warning, they may never calibrate.

GDE Computer Tune Question (Speedometer Related)

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