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Unread 06-25-2014, 04:23 PM
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Fair! Fair! is offline
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Join Date: Jul 2004
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Default Re: Vorshlag Miata LS1 Alpha Project

Project Update for June 25th, 2014: Long time no post on this project once again, but with some recent changes and progress we have regained some lost momentum and we are pushing to get this prototype LS1 NB Miata on the road by this Fall. After a spurt of work in January and a little more in April, some real time was spent on this project in May. Let's get caught up.

The biggest progress of late was a new milestone that was started and finished since the last post - the rear subframe and suspension was constructed. Right now the car still sits on 18x10" wheels and 285/30/18 tires at all 4 corners, with the new RX8 front suspension tacked up as well (see above). The front obviously needs more negative camber (and more adjustment range), which we're working on next.

Ryan, that started fabrication on this project has left us (left) but our new fabricator, also named Ryan, is on the case (right)

We had a few delays on this project in the months since the last post, due to a few unforeseen changes here at Vorshlag. For one, our lead fabricator Ryan B (above left) left us after almost 3 years of great work to pursue his college degree full time. He was working here part time for the past year and whenever we had to steal him for major fab work at our shop he didn't get to focus on the Miata swap often or for long. After he left we searched for over a month and found another great fabricator to join us, Ryan H (above right), who joins us with lots of race preparation and fabrication experience from a Daytona Prototype team and other previous race shops.

As soon as Ryan H started here we buried him in fabrication work on a customer's V8 swapped race car, then he spent 100 hours working on the Pikes Peak Subaru above. Once those pressing deadlines were passed he got to spend about a week and a half working on the LS1 Miata and a lot of progress happened, back in late May.

Custom Rear Subframe Construction

We weren't sure which way the rear subframe and suspension would go until we just dove in and started mocking up parts. We knew the factory rear hubs were going away, as we wanted to fix the problems we've seen in our V8 swaps to this chassis when we made ours - namely, busted halfshafts out back and fragile hub bearings at both ends.

There wasn't much to start with when Ryan got to the back of this 1999 Miata. We had looked at using part of the old factory rear subframe structure and cutting it up to fit the Ford 8.8" aluminum center section. The problem was the new diff was so large that most of the top of the old subframe had to be removed and very little structure would be left.

The stock differential housing, rear subframe and rear control arms were removed so we could mock-up the new parts we wanted to add. The rear hubs/uprights were ordered then we mocked up the Ford 8.8" IRS diff housing...

There was no way that 75 pound aluminum diff housing could fit without hacking the stock rear subframe beyond recognition, so it was set aside intact and fabrication of an all new rear subframe was started. The Ford diff housing was mocked up using some straight tubing passing through the new rear hubs and uprights we chose for this new set-up. These were chosen for their "high torque capacity" sizes on the hub bearings and the splined size for the halfshafts. Nothing that uses the OEM rear NA/NB Miata hubs or input spline can live much beyond about 250 ft-lbs of torque for very long, at least not with grippy R-compound rubber. The LSx motor that has been built for this Alpha car will make more than double that (450 ft-lbs+)

The uprights (below) we used are aluminum, very strong and work with the 5 x 114.3 mm bolt circle hubs shown above. This rear hub will work with the same wheel bolt pattern we're using up front, which we borrowed from the best OEM Mazda front bits. The entire front suspension is based on the beefier RX8 hubs, uprights, brakes and forged aluminum upper and lower control arms.

We also switched to a different rear cover for the Ford 8.8" IRS housing, which is shown above, deciding not to use the 2004 Mustang Cobra cover. This dual ear "winged" mounting style cover used is similar to the style that comes on the BMW E36 chassis and somewhat like the C4 Corvette Dana 36/44 housing - both cars we have worked with and raced hard for many years without issue. This style cover is easier to work on and mount to than the "clamped center mount" '99-04 Mustang Cobra rear cover used in our earlier mock-ups. This newer cover also has both fill and drain plugs on the cover, for use with a possible differential fluid cooler (common for heavy road course use).

continued below

Last edited by Fair!; 06-26-2014 at 11:39 AM.
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