carmudgeons.com - View Single Post - What the Mazda RX-8 should have been (new autocross car build)

John V · 06-03-2022, 07:56 AM

Long story short, I ended up getting replacement axles the night before I had to leave for the NJ Pro. I got the car back together and on the trailer and it performed flawlessly during competition...

... then I put a hole in the side of the block during the first round of the challenge. I'm not entirely sure why, but it dropped an exhaust valve in cylinder #3 which destroyed pretty much everything in the engine. It even took out the baffling in my oil pan, so that'll be fun to reconstruct.

So I'm pretty much dead in the water until I can build a new engine. Slightly different formula this time

2.5L block - same as before. 89mm bore
2.3L forged crank with 94mm stroke from an Ecoboost - replaces 2.5L cast crank (100mm stroke).
Billet connecting rods, about 10mm longer than before for better geometry
10.5:1 forged pistons
EcoBoost sodium-filled exhaust valves

EcoBoost oil pump

This will give me a 2,344cc engine (vs 2,488 from the last one) but it should be much happier at high RPM and it'll tolerate even more boost, so it should make the same or more power and have a higher RPM ceiling. It might make a touch less torque at 3,500 RPM but it was already traction-limited there, so no loss.

06-03-2022, 07:56 AM	#448
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,753	Long story short, I ended up getting replacement axles the night before I had to leave for the NJ Pro. I got the car back together and on the trailer and it performed flawlessly during competition... ... then I put a hole in the side of the block during the first round of the challenge. I'm not entirely sure why, but it dropped an exhaust valve in cylinder #3 which destroyed pretty much everything in the engine. It even took out the baffling in my oil pan, so that'll be fun to reconstruct. So I'm pretty much dead in the water until I can build a new engine. Slightly different formula this time 2.5L block - same as before. 89mm bore 2.3L forged crank with 94mm stroke from an Ecoboost - replaces 2.5L cast crank (100mm stroke). Billet connecting rods, about 10mm longer than before for better geometry 10.5:1 forged pistons EcoBoost sodium-filled exhaust valves EcoBoost oil pump This will give me a 2,344cc engine (vs 2,488 from the last one) but it should be much happier at high RPM and it'll tolerate even more boost, so it should make the same or more power and have a higher RPM ceiling. It might make a touch less torque at 3,500 RPM but it was already traction-limited there, so no loss.