26" or 28" for boosted car?

[SolarFlare]

Pretty sure you can't change revs per mile via Ngauge.

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[1quick]

Next time I drive my car I'll gps it and report back

 

[dubster99]

I was just curious because I just changed to a 28" tire so I went to adjust the revolutions per mile in the tune like I used to with my 14 gt, and it was the same deal in the sct x4 let me pick the size and flashed it in, I never did check the speedo to gps to verify it was right though

not sure why it never gets mentioned but to change tire/gear sizes you have the following choices:

-Custom email or dyno tune (requires buying SCT or nGage)
-HP Tuners (can purchase your own version for $399, scan your tune and reflash with correct tire/gears)
-Whipple Flash Tool

Whipple may be the cheapest route if ALL you are doing is changing tires and gears, but if you are considering slicks you probably already have a tune, which would mean the first two options are the cheapest.

Custom email/dyno tune via SCT/ngauge will NOT change your speedo. Yes, it says in the SCT you can change revs per mile, but this is a tuner that can be used across multiple platforms. On other platforms, it works. On the S550, it does not. When I was running 305/35, my speedo was 4mph slower than the GPS, even after changing the tire size in the sct, and having it set by a tuning company. You need the flare tool, as this modifies the as built data. Or you need a bluetooth obd2 dongle and a software that will allow you to modify it.

 

[TooSoonJunior]

I know HP tuners works so then it's Whipple and HP that works

 

[Legionofone]

Modifying as built is super easy and cheap, 30 bux for the usb to obd2 from amazon and then a free program. I fixed my speedo to within .5 of GPS

 

[1quick]

Modifying as built is super easy and cheap, 30 bux for the usb to obd2 from amazon and then a free program. I fixed my speedo to within .5 of GPS

What program do you use?

 

[Bartly]

What program do you use?

Lol, here is the post about how to do it. 1500 posts to read through with the info all spread around inside there somewhere. I haven't had the urge to go read it all, but it starts off with some instructions.

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