v8 Miata Forum - Home of the v8 Miata Conversion

Quote:

Originally Posted by Five-o-joe (Post 18612)

I think I've asked the question 3 times and gotten different answers but none that answer the question I'm asking. I guess I'm not asking the question correctly or I need to clarify....

I've been told it's the driver....drive it easy and it will hold 600hp

I also was told the 7.5 is plenty strong and the 8.8 is not needed, and I'm focusing on the wrong end....I need to focus on the axles, not the carrier.

I've been told the car won't get enough traction to worry about breaking

Respectfully, I'm asking the same question and getting different replies that don't answer my question. Let me expand on my intended use and driving style for the car. The car will be making over 400whp, and eventually 500-550. it Will be able to use the power and put it to the ground relatively well, and I do not plan to drive it easy. I want to be able to drive it to my fullest capability, which means right foot on the floor, never lift, kick the clutch and snatch a gear.

Can the 7.5 with upgrades in these light cars withstand 400whp for now and this driving style? If there are upgrades that can beef up the 7.5 to handle it, I'm interested to know what they are and where to get them. If I need a different rear, I'm interested in feedback on what other units may hold the power and driving style.

I'm very familiar with the 5 liter drive lines and the 8.8 solid axles having raced them for over 20 years....but have never owned a 7.5 IRS and know very little about the IRS so your personal experiences and recommendations are appreciated..

Joe

If you want the strongest rear end you can put into the car yes the 8.8 is going to be it. Get the upgraded axle's from the driveshaft shop and call it a day. Beefing up the 7.5 can be done but it's been out of production for so long parts sourcing is going to be your problem. Martin has several supercharged ford Miatas with 7.5's and they are holding together.

When your talking about driving a high horsepower car and beating on it never lift shifting your going to find your weak link. I would think U joints before the rear end but as a drag racer for many years I have had the pleasure of buying shiny new this will fix everything parts only to find my next weak point.

What you have going for you and what alot of people on this thread are pointing out is the Miata is a lightweight car that is not capable of running serious sticky rubber (large slicks) So your tires would normally let go of traction before your driveline. Kind of a safety fuse if you will. The driveline shock loads on a hard launch are not near what they would be in say a 3000 pound car.

TLDR:
7.5 should be fine barring drag slicks or wheel hop issues, ultimate strength 8.8 with upgraded axle's.