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

[Alan]

Very cool ... loving this thread and wow I give you a ton of credit, your knowledge is really admirable.

Btw I just drove the yellow RX8 the other day, not side tracking the thread but I continue to be amazed by how good this car is ... even with the slow unreliable rotary which btw really is my biggest disappointment with this car ...

[equ]

Awesome. Great write-up too.

[clyde]

Nice.

Are you going to duplicate the build thread elsewhere?

[John V]

Clyde, I don't know. I'm not interested in hearing about how I'm doing it wrong at every stage

Sorry I wasn't clear but I'm using a Mazda "L" engine, aka Mzr, aka Ford Duratec (designed by Mazda) in the 2.5L displacement. It's a very light aluminum four cylinder with 9.5:1 compression, factory forged crank and pistons, designed from the start for boost. Obviously I'll build it to handle the power I plan to make (around 520 at the crank).

Same basic engine as the Ford ecoboost inlne 4.
Jv

[John V]

Everything disconnected and the engine crane (thanks Bren!) hooked up to the one engine lifting point. My floor jack is under the tailshaft of the transmission.



Gradually lowering...



Lowered onto furniture dolleys



And, out! Installation is not quite the reverse of removal at this point. But now I can at least start to take measurements.



It looks like what's been said by the few people who have tried this is true... the back of the cylinder head wants to occupy the same space as the firewall. But it's only about an inch. The taller 2.5 that will replace this 2.0L is another inch taller as well. But honestly, that's not bad news. The factory subframe has enough room to easily move the engine three inches forward, and if I ran a dry-sump oil pan I can lower the engine easily three inches as well. I'm probably speaking too soon, but this doesn't seem like it is the disaster everyone says it is.

I guess part of that is because I'm not going to use the power plant frame, a big heavy steel beam that ties the back of the transmission to the nose of the differential. So I'll need to make a custom transmission mount and have a custom driveshaft made, but... no biggie?

[clyde]

Originally Posted by John V

The factory subframe has enough room to easily move the engine three inches forward, and if I ran a dry-sump oil pan I can lower the engine easily three inches as well. I'm probably speaking too soon, but this doesn't seem like it is the disaster everyone says it is.

If it's a choice, three inches lower seems a lot more preferable than three inches forward. But, 1) dunno what I'm missing and 2) not sure three inches forward is bad enough that it's that bad.

Sandbox or elsewhere thread would probably get a lot more activity than it will get here. And probably more helpful questions/suggestions, too, but I'm sure you'll have it covered anyway.

Gonna be fun to watch either way.

[Biggins]

I'm excited to see the final product! I'm sure you'll run into some snags, but I know you can work around them to make it a cool car that is hopefully really fast too.

[John V]

Attached is a picture of a stripped MZR on an engine stand. It's not my engine.

On the rear of the block /cylinder head there are two accessory items that stick out. One is the EGR valve (rear of cylinder with black "top hat") and the other is the cylinder water outlet (the black pipe on the rear of the block, above the Miata headlight in the pic). Both of those foul on the firewall when you put an MZR in an RX-8.

The EGR I'm not worried about - I'll delete it and put a blockoff plate in its place. The water outlet is a bigger problem, because obviously I can't delete it. One good thing about choosing the MZR is the engine is cheap, light, and as a result popular for swapping into stuff like Caterhams and old British cars. There are a few companies that have designed unique water rails which remove that factory water outlet and replace it with something much lower-profile. this piece takes the water and routes it above the exhaust ports on the passenger's side of the engine towards the front. I think if I use something like this the engine might come close to bolting in without anything other than lowering it a couple of inches.



anyway... options.

[Alan]

Totally off topic question ... it is cold as Sh*t ..your garage is heated ?

[John V]

Originally Posted by AF

Totally off topic question ... it is cold as Sh*t ..your garage is heated ?

Kinda. I've got a huge propane heater in there (hanging from the ceiling above the workbenches), but I keep it set to a really low temperature and still manually cycle the thermostat when I'm working in there to keep costs low. The detached garage where I'm doing the work is a cinder block building with no insulation and with very drafty old garage doors.

If the air temp is in the 45 degree range I'm perfectly comfortable working in there... the annoying part is the garage is built on a very thick concrete slab and it stays cold basically all year long. Great in the summer (except water condenses on it in the summer) but not great in the winter. Even with ski socks on and work boots my feet get really cold out there.

In the next few years I plan to frame out the walls just enough to put some rigid foam insulation on the walls, replace the old wooden doors with roll-up doors, insulate the attic and epoxy the floors, but I don't know when I'll get to that.