Is this for track use? I think the general consensus is that on a track 4.77s are faster overall, although you will be spending more time shifting. I know someone that went that route, was not sure at first because of having to shift more, but says he is overall faster on that setup. And of course, if doing anything competitive gearing changes may fit into your classing/mod factor easier than adding much more power via boost. There are many spots on track where I do wish I had shorter gearing.


For an AP1 tune, if you can find someone selling a Karcepts Emanage setup that is one route. Karcepts no longer sells them (contact Brian to be sure on that) but that is what I have been running since 2016. You definitely want a HFC or test pipe with it. The tune was built with a PLM header too but that makes far less difference than the HFC with this tune. He spent a lot of time building a tune for the AP1 that works pretty much across the board and required zero additional tuning. A friend had a gernby and our dynos looked identical. There are of course stand alone options if you want to go that route.

 

Just shortens the gears. Shorter/higher number = More torque feel. I think the other difference people have said between the 4.44 & .4.56 is the RPM/MPH shifting point. Been ages since I researched this.

 

It's a ratio. The AP1 and AP2 differentials are both a 4.10 ratio. 4.1 revolutions into the differential to 1 (one) turn out. Higher numbers are a lower gear ratio. (AP1 and AP2 gearboxes have different final drive ratios but the differentials are the same.)

4.10/4.44=0.92 will be and feel 8% quicker
4.10/4.56=0.89 11% quicker.

6th gear AP1 rpm at 75mph (AP2)
4.10 4036rpm (3968)
4.44 4359rpm (4358)
4.56 4480rpm (4404)

The jump from 4.10 to 4.44 is pretty big by comparison to the jump from 4.44 to 4.56. At any road speed the engine will be turning faster and using more fuel.

-- Chuck

 

Thanks for the explanation you guys. Maybe I will try the 4.56 over the 4.44 if that is the case.

 

If you're looking for an eManage with the Karcepts tune, I have one I'll be selling.

 

I'm currently having my diff rebuilt and getting an OSGiken installed. We went through a gearing calculator for a while before settling on a 4.56. With that ratio, 5th gear i think topped out at 132 and my top speed on track is generally 125, so that's what I decided on because I don't want to use 6th gear on track. We also decided on the 4.44 as a secondary option if we couldn't source the 4.56, because I don't think they make them anymore... I forgot which company he sourced it from, but he was able to locate a 4.57, so that's what's going in mine.