What the Mazda RX-8 should have been (new autocross car build)

John V · 01-07-2018, 12:52 PM

So, the rear diff. The stock diff is something like a 4.44:1. For a rotary with a 9,000 RPM redline or whatever that's fine, but the 2.5L MZR (aka Ford Duratec) that I'll be using won't want to rev past 7,000 regularly, so this is way too tall. I was searching for something with around a 3.73:1 ratio to give me 75MPH at 7,000 RPM in second gear. Also, this thing is a pig.

82 lbs!

01-07-2018, 12:52 PM	#6
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,753	So, the rear diff. The stock diff is something like a 4.44:1. For a rotary with a 9,000 RPM redline or whatever that's fine, but the 2.5L MZR (aka Ford Duratec) that I'll be using won't want to rev past 7,000 regularly, so this is way too tall. I was searching for something with around a 3.73:1 ratio to give me 75MPH at 7,000 RPM in second gear. Also, this thing is a pig. 82 lbs!