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Vehicle: 2006 Mustang GT Premium Auto - Vista Blue
Location: Deep in the <3 of Tx
Posts: 2,852
Quote:
Originally Posted by Tylus
that is kinda high rpm don't you think?
No it's not. My calculations (as I said) were done against the auto 5R55S which has an O/D (5th) of .75:1 ratio. Compare that to the 5-speed manual's .68:1 5th. This is why people say 3.73 for auto and 4.10 for manual. The math works out to be nearly the same between those two due to the auto having lower ratios.
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Vehicle: 2006 Mustang GT Premium Auto - Vista Blue
Location: Deep in the <3 of Tx
Posts: 2,852
Quote:
Originally Posted by HotDogN
I put a taller tire on it. 28", so my RPM at 70 is only 2600 to 2700. still averaging 24 MPG on highway.
It should be 2873 rpm (since you have an auto ). Which makes sense b/c of my previous calculation was assuming a stock 27" tall tire (27.17 if you want to be exact).
I was able to get 24.x MPG at 80 MPH a while back, which for me right now is 2456 RPM, and that was with my bama tune which seems to give me slightly worse MPG than my Brenspeed tune. So I guess if the tune is good, hitting 24 at your RPM (with the taller tire) makes more sense to me now.
I think I have lost 1-2 mpg on the interstate, but what I have noticed is that my around town driving has acutally improved my mpg. So kind of a trade off. 5th becomes a nice cruising gear for around town...so far I love them.....I would do it again in a heart beat....wish I had done this as my first mod.....
What if you have a 20" rim. How does that change things betweem 373 and 410. The whole thing kinda confuses me. Some people say if you have 373 and a 20" rim then you would really have like a 355 rear. Somebody explain this to me please.
__________________ 2008 Black GT "Midnight express"
Pypes MM System
UPR Offroad x pipe.
Steeda CAI.
Steeda UDP's.
Hurst Short throw.
Bamachips 91 Race tune.
Vehicle: 2006 Mustang GT Premium Auto - Vista Blue
Location: Deep in the <3 of Tx
Posts: 2,852
Quote:
Originally Posted by Midnight Express
What if you have a 20" rim. How does that change things betweem 373 and 410. The whole thing kinda confuses me. Some people say if you have 373 and a 20" rim then you would really have like a 355 rear. Somebody explain this to me please.
It's not the diameter of the rim that matters, but the diameter of the tire. The stock diameter is 27.17". So the bigger the diameter you go, the effective rear ratio will become a smaller number.
The stock tire circumference is about 85.36 (in this document I made, I have it as 85.34 for some reason. I guess I didn't use enough numbers for PI or something, lol).
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). Which makes sense b/c of my previous calculation was assuming a stock 27" tall tire (27.17 if you want to be exact).
