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Unread 11-11-2015, 07:52 PM
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Default Re: Vorshlag Miata LS1 Alpha Project

Project Update for November 11, 2015: It has been a long time since my last update on the Alpha Miata LS1 swap build thread, so we have a lot to cover in this update. This project was on hold for a while, but was put back on the schedule in July. Since then the front and rear suspensions were wrapped up enough to put the car on the ground, wheels and tires mounted and tested, bodykit mocked up, engine's intake and accessory drive finished, and more.

Our first LS1 powered Scion FR-S (shown above right, next to the LS1 Miata) was completed enough for the customer to start driving it during that 6 month hiatus in the Miata project, and we developed some new things on that swap that will help us on the Miata. The FR-S recently came back for some follow-up development and I will update that build thread soon.

Difficult Realizations

There were many things going on behind the scenes that held up progress on this build for the first half of 2015. Obviously this project has moved beyond the original scope, because it became much more than just a "bolt in swap kit".

As we moved from section to section and addressed the weak points, the project began to fall well outside the realm of just a V8 swap kit. We were dedicated early on to removing all of the weak links that we often see fail with track abuse in other V8 Miata swaps, namely the front hubs and rear hubs, the rear halfshafts, as well as the need to upgrade the OEM brakes and control arms to deal with massive engine torque and tire grip. Addressing those issues in a kitable format was going to take serious added engineering and fabrication hours, more than we could every hope to recoup with kit sales. So the decision was made to do this car as a one-off, making both the engineering and fabrication easier and saving hours and hours of unbilled development time.

The customer and I had a good conversation in late June, after we both did some research into other Miata V8 swap costs. This is when we realized where reality was: With many turn-key swaps for V8 Miata's costing $50K (minus the chassis), our revised numbers for a one-off build didn't look so far out of the realm of possibility. We all agreed to some compromises and then moved forward. This delay ate up several months this year but we were back on track late this summer.

Does that mean we will no longer offer the finished work in kit form? After a hard look at the costs, I doubt it will be at a price point most people will want to pay for a home-built swap kit. Of course we can replicate these parts on the Alpha V8 Miata as a turn-key installation for others. Will it be cheap? No, but it won't be out of the range of other turn-key Miata LS1 swaps.

I feel that the end result will make for a pretty durable and damned fast track car that can still be street driven. It might end up being the only Miata V8 ever build to this level of insanity (this customer asked for "crazy"), but that's not necessarily a bad thing either. Let's look at some progress!

Rear Suspension Change and Major Progress

The final steps of finishing the rear suspension were pretty tricky on this car. Due to some challenges we had to think outside the box to get to the finish line.

We have taken a car made for small brakes, small halfshafts/hubs, and small wheels and tires and jammed a massive 8.8" Ford diff in there, big aluminum uprights from a RWD V8 powered production car, and are building all of this around an 18x10" wheel and 285/30/18 tire out back.

Once the custom upper and lower control arms were built and the halfshafts mocked up, it was clear there was not enough room for a coilover rear shock and spring in the normal location. We tried it upside down, right-side up, moving the upper and lower mounts this way and that - no chance. The rear suspension upright layout we are using made it impossible to fit the spring and shock there.

It was just a matter of space - there wasn't enough of it. So I decided to change the rear shock layout into a pushrod/bellcrank style, and move the spring and shock into the trunk. What the what?!

This took a lot of work - mock-ups, calculations, CAD design, CAM programming, CNC machining, fabrication, and testing - but it is in place and we now have the shocks mounted in the trunk. The suspension moves up and down and all of the motions look good, and everything is overbuilt and strong.

A big chunk of billet aluminum was used to make the pair of bell cranks in multiple steps on the CNC mill, which was a good use of our new CNC machines and skills that we added in January 2015. We bought CNC machines to make ALL of our production Vorshlag components in house, but this also allows us to make custom one-off things like these Miata rear bell cranks.

We didn't go to pushrod actuated inboard suspension to be cute, but out of necessity. The bigger, stronger rear suspension and driveline parts we felt were warranted in this V8 build just ate up too much room, and we had to spend more hours to move things around (most of which were unbillable development hours).

I will go into more details on this rear suspension once we have done some road testing, but so far I'm happy with the results. The bell cranks were CNC machined in custom fixtures over 3 operations to make the completed bits. Radial ball bearings were installed for the pivots and rod-ends are attached at each end of the bell crank - one to the pushrod and the other to the shock.

The front shock we had already built was used for the rear mock-ups and the length/stroke were pretty spot on for the rear, with the motion ratio of the bell crank and pushrod location on the rear control arm.

The rear control arms had double-shear pushrod mounting tabs added, then the pushrods were built, and the whole setup was then tested through the full range of suspension motion. Once that was confirmed the rear control arms were final welded.

We have fixed length mock-up rear shocks in place for the moment, but another pair of Bilstein ASN coilovers will be built to wrap up the suspension soon. Now we can at least check ride heights on the ground, start tire mock-up, and move forward on other systems with what we have in place.

The fuel filler neck will be relocated inside the trunk at the left corner, to leave room to load luggage for use on road trips. This car will not carry a spare tire, so some of the brackets that are used to hold the jack and temporary spare will be removed to add some much needed trunk volume.

The rear shock mounting is probably the craziest part of this swap, but again, it was the right solution for the constraints we had.

Engine Completion Work

The built LS1 longblock that we have had in place for a while was finally dressed out with many missing intake and front accessory parts in recent months. First up was the coil packs and brackets, which were purchased, assembled and installed.

There are a number of various coil packs and coil pack sub-harness ends made for GenIII and GenIV LS series engines, but if you order the main engine harness correctly, it doesn't matter which you choose. We went with F-body brackets, sub-harness and coil packs. These bolt to 1999-02 Camaro LS1 valve covers, where I used button head stainless M6 bolts to hold them in place.

The LS2 intake manifold and throttle body were installed next. I explained in detail why we used an LS2 intake and throttle body on the Alpha Fr-S in THIS POST, which you can go back and read - because it also applies for this car. Basically the LS2 manifold has the same cathedral port shape as the LS1 heads on this motor, but it has the "short" drive-by-wire throttle body needed to clear the hood. If we would have used an LS3 motor the LS3 intake manifold and throttle body would have been the obvious choice. Cable operated throttle bodies are much longer and would not clear the hood line.

continued below
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