pdonket

They usually have to keep them subtle, because owners usually take it the wrong way when a company says "oh yeah, you know how the old drive shafts used to explode at high speeds? our new cars don't!" lol. Especially on cars that are meant to be pushed to some extent, that's a dangerous move.

jc_puckett

I bought my son a 2013 Mustang Coupe with 305 hp, 3.7L V6 about two months ago. On the long, lonely, straight road to Cedar Key, Florida, I opened it up and was shocked that it would only go 111 mpg (Garmin GPS mph). I tried five times during our 4 day vacation.

My 2015 Honda Pilot 300 hp V6 will outrun my son's Mustang. That is ridiculous. So, what is a "tune" and where can I buy one? And which brand / model no. should I order.

Jim Puckett
Midland MI

danzcool

First make sure you take care of the safety items, like the driveshaft, here's a video of one failing, generally the stock driveshaft (on the V6) is not to be trusted above 120MPH, that's why the speed limiter. Also make sure your tires have the right speed rating. SCT tuners are good, you just need to ask whoever's writing your tune to bump up the limiter.

jc_puckett

Who's driveshaft do you recommend?

Jim Puckett

danzcool

It depends on your goal. You really need to do the math to figure out how many RPM's your driveshaft will be making at the target speed, then call up the various driveshaft manufacturers and see what the critical RPM for their driveshaft is. Critical RPM is the speed at which the driveshaft begins to develop harmonic vibrations which can quickly lead to failure.

1st, you take the target speed, let's say 150MPH, convert that to feet/minute, which is 13,200.
2nd, you figure out how many feet are in the tread length of your tire, so take the actual tire height which we'll assume is 27", multiply it by pi to get about 85" or abuot 7.083'.
3rd, divide 13200 by 7.083 to figure how how many wheel revolutions you have per minute... which is about 1864.
4th you multiply the wheel revolutions by your rear gear ratio, so assuming you rear gear is 2.73, 1864 times 2.73 is your driveshaft RPM of 5,089.
but if your rear gear was say a 3.31, then the driveshaft RPM would be 1864*3.31=6170
and if you had a 3.73 rear gear then it would be 1864*3.73=6953.

Of course if your tire is smaller then your numbers also go up.
One thing to keep in mind is that the larger the diameter of the driveshaft the higher the critical RPM, but the longer the driveshaft the lower the critical RPM, the material also affects the critical RPM as far as it's rigidity & weight play. Lighter and stronger = higher critical RPM, so a well built carbon fiber driveshaft will give about the highest critical RPM, it'll also cost you over $1000, so usually people go with aluminum or chomoly which can usually be had for around $500-$700.
Best bet is to just call the driveshaft manufacturer and tell them what your goal is, they have calculators that figure this out and can tell you what you need... or you could trade in for a 2013-14 GT500 which already has a carbon fiber driveshaft that Ford says will get you to 200MPH.

jc_puckett

Thank you danzcool. I just want to do a "tune" to up the Speed Limiter past 111 mph to 130 mph. We will change the OEM tires to Michelin, but to get a "V" speed rated tire, it looks like we will have to go to a 19" wheel and I don't know if a 245/45-19 wheel/tire combo will fit my son's 2013 3.7L v6 Mustang Coupe.

http://www.americanmuscle.com/alumin...v6-manual.html

Jim Puckett
Midland MI

Chromeshadow

The factory wheels on the 2012 3.7 performance package are 19" with 255/40R19 tires.
This would be my choice if I wanted 19s. Btw, the top speed limiter is the same for both the 3.31 and 2.73 differentials, which means if you have the 2.73 rear end, the drive shafts is fine at 130mph.

azdriveshaft

We offer a Upgraded Driveshaft for the Mustang that is a one piece aluminum direct bolt on that eliminates the need for an adapter at the rear differential. By changing from the factory two piece steel shaft and going with a one piece aluminum shaft we can offer more than double the critical speed & horse power rating over stock.

Norm Peterson

There are plenty of tires in 18" and even 17" with speed ratings of "V" or higher. Most Michelins seem to be at least "V", looking at Tire Rack's specs for several different Michelin models only a few I saw come with an "H" rating, and that includes several of their all-season tires.


I'm surprised nobody mentioned tire speed ratings when this topic was first opened up. High speed + Dubai climate . . . hmmmm


Norm