LS3 into a 2004 Miata

[John is filling out Lotto slips hoping to convince you to do a NC with a 2012 Mustang V6 and 6 speed]

Update!

With all the heat shielding in place, it's time to start putting parts inside this car. Underneath, you can see the frame rail reinforcements bolted into place. The flat plate about halfway along is a mounting point for a transmission crossmember. The braided stainless line is a -6 AN fuel line, the stock 5/16" lines aren't big enough even at 60 psi. The fuel filter visible to the right of the picture is actually a stock Corvette part, which has an integrated FPR.

The diff is mounted as well, pictures to come later.

Time for wiring. Here's what a GM Performance Parts LS3 controller kit looks like. The computer is standard 2012 Corvette with a stripped down operating system and with various items such as the rear O2 sensors turned off from the factory. The wiring harness has labeled ends on it and is ready to plug in to factory connectors. It even includes two O2 sensors and weld-in bungs.

We've reinstalled the brakes including the (still functional) ABS system and are starting to run the GM wiring along with some Mazda wires.

John Brown wrote: [John is filling out Lotto slips hoping to convince you to do a NC with a 2012 Mustang V6 and 6 speed]

you would!

Joey

Okay, back from the long weekend. Time to get to work.

We move the radiator down and forward a bit to get clearance. You can see the original bolt holes here. We put some rivnuts in the frame so the bracket can be removed in the future. Not sure why you'd want to, but Mazda felt it was important so we retain that ability.

One loaded powerplant, ready to install.

No more pictures of the engine on the floor. Because now it's in the car, and it's going to stay there.

This wasn't an immediate installation. Kyle spent a lot of time easing the engine in and double-checking wiring and brake line routing. Once that was finalized, he made sure everything was properly anchored before committing.

The radiator we use is one we developed specifically for the swap. It's a dual pass so the inlet and outlet end up on the appropriate places for the engine and are the correct size. There's also a steam vent fitting on top. It has a set of high torque (not slim) Spal fans mounted to a shroud on the back. Slim fans are great for packaging, not necessarily any good for actual airflow once they're starting to pull hard.

Wiring time. Now it gets boring. But the quality of the work here has a big effect on how reliable the car is later.

Start to finish, how long is it taking you guys these to complete an LSv8 build?

Depends on if the tech is able to do the work non-stop or if he gets pulled off on something else - that pretty much always happens. For example, Kyle was getting one of our own V8 cars prepped for a track event last week. But we'll assume a full-time tech, I think it's 6-8 weeks. It also depends on the condition of the car (this one's a bit crustier underneath thanks to Michigan) and what other options the customer has requested. This particular car is pretty bare bones, so no seat heaters, custom wiring or seam welding.

This may be a silly question, but how much HP can you push before things get scary?

That depends on what you have going on in the chassis department I have about 400 wheel hp in the Targa Miata, and I need more - especially down low. Most of us here prefer the 430 hp LS3 over the 480 hp LS376/480 crate engine, but that's because it has better low speed driveability due to a milder cam. The higher power doesn't worry me.

So it's more of a torque preference?

I'm not sure what that means. Torque is good. Power is good. In a rally car, you need mid-range torque more than top-end power, and I want to be able to come off high-speed corners harder.

Our preference for the 430 vs the 480 has to do with the smoothness of the engine at very light throttle openings. Very light - the amount of throttle needed to get a 2500 lb Miata moving when using a 6.3l V8. The hotter cam has a tendency to buck a bit. You can drive around it, but the 430 (with the stock cam used in the Corvette and Camaro) is a sweetheart.

Oh, I see what you're getting at. It's how the power gets applied.

It's basically the same as a rough idle from a big cam. At these speeds, the car is barely off idle so 'rump rump rump' turns into 'lurch lurch lurch'.

The engine and transmission are still available.

More pictures!
Wiring, wiring, wiring. Here's a shot of some of the transmission wiring, reverse lockout, reverse switch and speed sensor. We're making sure everything is tied down and protected for long-term happiness. The blue-grey piece at the bottom of the picture is the transmission crossmember, particularly the cutout for the exhaust. The stainless bracket is to support the exhaust.

The PCM is mounted in the engine bay behind the passenger's headlight. It's designed for this sort of environment. Will the car ever be this clean again?

Here's a blast from the past - check out what's embossed in the top of the fuse/relay box from GM!

The big visible changes are slowing down as Kyle works on the wiring and details. Still, there are a few big steps.

Here's a peek at the tubular subframe and steering rack mounts. The subframe keeps the stock geometry for both control arm mounts and steering rack location for minimal handling disturbance. It's also about 10 lbs lighter than stock.

The rear axles in place. Since the car has ABS, we have them made with ABS trigger rings.

This shot turned out really nicely Underneath. As you can see, the exhaust is in and things are getting buttoned up down here. I think we're aiming for First Noise tomorrow.

How much does the GM ECM kit retail for?

Dang, that's clean. It looks like that motor belongs in there!

John - street cost is around $1000 for the PCM, wiring harness, throttle pedal, MAF, O2 sensors and fuse box. GMPP part 19258270.

Dang, wish I could have one of these. 1.6 Turbo can't quite compare.

Okay, it doesn't look any different. But it sure sounds different. We had First Noise today. Somehow, the fact that it runs makes it seem almost done...

Progress! Kyle was gone for a couple of days due to family reasons, but he's back on the car and working hard.

Some surgery for the new intake - we use the stock intake from a new Z06 on the cars for maximum cold air. Plus they look awesome.

Suspension is in. Yes, the stock control arms have some surface rust on them. The customer decided not to have us clean them up as he is trying to keep this on a reasonable budget.

Interior! We're getting close to the first drive. Note the location of the shifter - stock.

Keith Tanner wrote:

That front subframe is a really nice looking piece.

The whole job is really impressive. I would have a hard time leaving the surface rust on the control arms just because of how nice everything else looks.

If it were my car, I'd probably be stripping them. But the customer doesn't want to pay us to do it, which I can understand. That can be done anytime in the future if he finds himself with extra time and/or money. Besides, you'll only see them when the car's in the air!

Moar.

Sorry about the blurry picture, but we installed Frog Arms under the front fenders to add some rigidity to the front end. You can also do this by seam welding, but that's a lot more work - and thus more expensive.

The intake is now installed as well. See, I said they looked awesome.

It's amazing how much it looks like it was there all along.