924Board.org

[CBass]

This is the engine I've settled on, for many reasons. First and foremost is cost, if I could afford a 968 3.0 and cams, header, standalone management, that would go into the car, but I can't. A low mileage KL-ZE can be had for $600, or with tranny and manifolds for $1000.

The basics:

2.5 liter naturally aspirated V6
DOHC, 4 valves per cylinder, quench type combustion chamber similar to 968 combustion chamber, with excellent intake port angle and geometry. The tappets and valves are of extremely lightweight design, making the stock valvetrain capable of sustaining 9000rpm.

Bore 84.5mm, stroke 74.2mm, makes for a light revhappy engine. The pistons are very short, and very light, with a long connecting rod. The crankshaft is forged steel, triple lapped, mirror polished with bearing journals that are partially ground, and then rolled to finished dimensions for extra strength, before plasma nitriding. The stock crank has been tested at over 800hp, and is nigh indestructable.

The block is a split crankcase style, like the 911. It has a rigid lower half that bolts to the upper half of the block, housing the crank in between. This means the crank does not wander, even at extremely high engine speeds. The block is made of cast aluminum, with iron alloy cylinder sleeves that provide excellent strength. It has oil jets that spray the piston for extra cooling as well. The oil pump is a front mounted trochoidal unit, which provides much more than adequate oil pressure and volume.

It has Mazda SEFI, and a variable resonance intake manifold that us quite similar to Varioram. For my purposes though, I'll be junking both, in favour of stand alone EFI and a individual throttle body manifold of my own design. The engine does not come with an ECU, because of importing regulations, so I'd rather spend the money putting together a Megasquirt EFI system, using the stock Mazda fuel maps, and distributorless ignition.

The engine has been shown in stock form(with free flowing intake and open exhaust" to be capable of sustaining 8900rpm for 4 hours, by Ford engineers at their Dearborn test facility.

With a fairly restrictive intake system and quite restrictive cast iron exhaust manifolds, the engine makes 200hp. With bolt ons, they dyno around 180whp. I figure with headers and my manifold design, it should make around 240hp, in the high 7000rpm range.

It's quite compact, lots of room on either side, and due to it's short stroke and small oil pan, it's not all that tall. With the new intake manifold and a custom crossmember, clearance should not be an issue. The motor weighs around 250lbs dry, which is quite a bit lighter than the 2.0 in our cars, which weighs a bit over 300.

What did Mazda put this incredible engine in? The JDM MX6 and 626. This engine definately belongs in a sports car, and would have made an excellent option for the Miata. The US and ROW spec MX6s received a detuned version, simply called the KL. It had weaker cams, lower compression pistons and different engine management, but other than that, it is the same engine. They're in junkyards all across the world, just waiting for a good home.

For the installation, I plan to have a custom flywheel made to fit the KL-ZE engine, using a 911SC pressure plate and the Bronco 4.0 clutch disc. Cost for the flywheel is going to be around $500, I have a few quotes already.

The engine will be mounted using stock mazda motor mounts, and I will make a crossmember out of aluminum square tube and 1/4" plate. The engine is quite a bit shorter than the 924 4 cylinder, and leaves plenty of room for intake plumbing. I want to make something along the lines of the Mercedes Benz DTM intake, just because I love the way it looks, and it's an excellent design.

http://membres.lycos.fr/amprilly/photos/montages/warsteiner/clk-10.jpg

The only pic I could find was of a model, but you can see the design pretty clearly. I would make the plenums smaller, for a little higher intake velocity, and I wouldn't have the restrictor bottlenecks right before the plenum like they run in the DTM series.

Here's a SAE paper on the engine, with technical diagrams, and lots of good info.

http://www.rs-productions.com/RSP_Motors/tech/sae-920677/sae-920677.htm

[/rant]
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'81 931 in various states of assembly

[sickboy14]

A motor I always wanted to try in a 924 (from a FWD car, anyways) is the taurus SHO motor (Yamaha built)....

The motor itself was capable of sustaining 11k RPMs, but the accessories limited the motor to 7500 RPM....
With 220 h.p, those motors were pretty sweet, too.... They can also be found for cheap...

On the same note, i want to see a 2.3T Form Thunderbird or SVO motor in a 924... that would rock my socks...
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'81 924 N/A 5-speed-project in early stages...
'93 Volvo 850 GLT-N/A -stolen