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Unread 12-17-2014, 11:16 AM
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Default Re: Vorshlag Miata LS1 Alpha Project

Project Update for December 17th, 2014: We've been busy on the Miata over the past few months but I've just been too busy to get caught up on the forum updates. We just finished construction and a big shop move for Vorshlag, doubling our available space, which ate up a lot of my time. This move has made for some extra room to work on projects like this, to add some new fabrication equipment, and just this past week for two CNC machines (lathe and mill) to finally make our machined Vorshlag products 100% in-house.

Right after the move in November a majority of Vorshlag folks also went to SEMA and then we were competing in OUSCI (Optima Street Car shootout) in our TT3 Mustang. Then Jason went to the 2014 PRI show and took 100 pics of cool new parts. Ryan stuck around at our new shop in Plano, Texas, and worked on the Alpha Miata V8 and made some really good progress. Then he found some more days in late November and early December as well. Anyway, we have all been slammed, but big progress has been made on the Alpha Miata.

The 2014 SEMA show and the OUSCI competition were fun but ate up a lot of time I where could have been updating various build threads

Front Suspension Follies!

Last time we updated this build thread, Ryan had finished re-checking the geometry on the rear bits, tweaking the rear subframe and making new rear control arms. That was back in June. In August he was freed up a bit and finish-welded the custom rear rear control arms. They are ready for shock mounts, cross bracing and custom half shafts at that point, but the rear subframe still needed to be final welded. He wanted to tackle the front before "locking down the design" (track width, ride height, etc) out back.

Now we move ahead to some time he had in August, when he moved to the front, to re-run the 3D geometry on the RX8 spindles/arms that we already had mocked up and tacked in place to the custom tubular front subframe. Well... while it looked fine to the naked eye, once the wheel was at the proper ride height (now visible with the RX8 hubs mounted to the new hub-stands, shown above) the geometry was less than ideal. Once the pivot points were input into suspension analysis software it was obvious that anti-dive and bump steer were terrible. Still, I wasn't giving up on keeping the suspension/brakes "all Mazda" up front, so I had him stick with the RX8 bits a little longer and try to move the pick-up points to try to dial some of this out.

Ryan cut off the previous pick-up points and made new ones, then rolled the mounting points as far as he could within the constraints of the stock front Miata tub and the RX8 arms. After sourcing some factory Mazda RX8 eccentric bolts and making the new control arm mounts that mimicked the factory subframe mounting points, it looked great and had the adjustments we needed, but the geometry still wasn't getting much better. He did some 3D measurements, saw some room to improve, then yanked the subframe and started over - making an all new front subframe section, from scratch, to gain some room for our the RX8 suspension at the lowered ride height and to fit with the big tires we had in mind. Two steps forward, one step back - that's how it works sometimes. The second, new subframe was tack welded together and had several improvements, and we would end up sticking with that through the next suspension iteration.

After he re-installed the RX8 bits it still wasn't good enough, so our engineer Jason and I asked Ryan to just fabricate new control arms to use with the RX8 uprights and hubs, but after an exhausting search the OEM style ball joints for the RX8 (very funky taper and size - nothing like anything supported by the aftermarket) were not available separately, so this was a dead end. Bah! I finally pulled the plug on the RX8 spindles and pretty aluminum control arms. We had already acquired brand new RX8 brake parts, too. Oh well, some ideas just don't pan out. Lots of fabrication hours were wasted based on my notion of using OEM RX8 spindles, brakes and front control arms.

After this latest wild goose chase we had Ryan stop working on the car for a few weeks while engineer Jason and I regrouped, to look for other front suspension and spindle solutions we could utilize. After this debacle we realized that swapping in another set of control arms wasn't going to work inside the narrow confines of the Miata without several miracles, so instead we focused our search on a good OEM uprights that was made for a double-A Arm suspension. The result was we found something much better than the RX8 bits - lighter, forged aluminum, even more common to find, with tons of aftermarket support, beefy front hubs, and dozens of OEM and aftermarket big brake options. So, what did we use?

When In Doubt, Just Use More Corvette Parts

Corvette C5 spindles were the chosen upright this time (C6 are virtually interchangeable, too) and the first one we purchased looked great - and proved to be significantly lighter, too. And honestly we don't care where the parts come from, if it meets the criteria for use on a hybrid build like this: use the best parts available, that can be purchased at the best price, with good aftermarket support, easily procured consumables, and the best materials/strength/design.

The C5 aluminum upright was 5.6 pounds (13.96 pounds, with hub and ball joint installed - and the unit bearing hub is BEEFY!) compared to the 15.5 pound RX8 steel upright and hub. The nice thing is that the front and rear spindles on a C5 (and C6) are interchangeable (RF and LF are the same, LF and RR as well), which doubles your chances of picking them up second hand. Once we had one of these forged C5 spindles on hand, new ball joints were ordered next (we first made sure first that they were available separately!) and Ryan started making a whole new set of upper and lower control arms.

These would be tubular, the right lengths, and after some analysis, end up with better geometry, and have more range of alignment adjustment than the "eccentric" bolts of the RX8 arms. We could now adjust camber and caster through a larger range and achieve proper geometry at the ride height we wanted without cutting up the Miata tub. The lower arms would house the C5 ball joints and the upper arms would accept the matching C5 upper. The ends we chose were firm polyurethane bushings and the lengths were to be adjustable. A lot of pieces were ordered, many more were custom machined, and a lot of hours were spent calculating, fabricating and measuring.

Making this car as a one-off build would have been SO much easier - we would have just notched out part of the frame and made the RX8's control arms pick-up points fit in space where they would work for the geometry. But we have been going to great lengths to keep this subframe and suspension a reproducible kit, and to keep it a purely bolt-on set of parts, which meant not chopping a chunk out of the front frame section to move the upper control arms upwards. In the end we found that the C5 spindles, with the OEM ball joints aimed as they are, allows for the geometry we needed within these MX5 chassis constraints, using these custom control arms. BOOM!

Steering Rack Placement + New Steering Shaft

Once the new front control arms were fabricated and tacked welded, then geometries rechecked (both manually/visually and in software), it was at a good stopping point. Ryan then began to tackle the front steering rack mounting.

The NB Miata steering rack was placed in the ideal location for the slightly altered wheelbase and new front Corvette spindles, keeping in mind the necessary oil pan clearance. We have a half dozen different LSx oil pans around here to test with, so we worked with those to find the right combination to clear the steering rack without adding bumpsteer. The final rack mounts were fabricated and tacked to the crossmember.

This new rack location (and the small wheelbase change) would mean we would need new, slightly longer intermediate steering shaft assembly in the engine bay. Luckily we're used to making those for all of our BMW LSx swaps, so this is another bolt-on solution. What you see above is a mock-up - with one of the two aftermarket steering U-joints installed with a piece of 3/4" Double D shaft, to check lengths. The final solution will be a proper 2-piece collapsible steering shaft assembly like our many Vorshlag BMW steering shaft assemblies (see below). We make these to improve header clearance for V8 swaps on various BMWs, improve the heat resistance of the U-joints (the OEM steering shafts on LHD cars with inline engines are not meant to see exhaust heat) as well as to remove nasty rubber "rag joints" (steering shaft isolators) in the shaft, for better steering feel. We even sell a lot of these steering shafts to BMW racers who keep the BMW engine, just for the improved feel.

Olof took a fresh NB steering rack core and converted it to a de-powered rack (we do this work on NA/NB Miatas often), welding up the bits necessary. We will use no power steering in this car initially, then switch to an electric assist solution if it is deemed necessary.

Front Drive Accessories

Running no power steering pump will create some headaches but also solve some potential problems. Hydraulic fluid power steering assist is always a hassle in any car; the system can make for a huge mess when it leaks, and requires an engine-driven hydraulic pump, reservoir, cooler, and high end hoses on a tracked car. This system is the number one cause of on-track fluid leaks and underhood fires, so taking hydraulic power assist out of the equation is fast becoming part of our track-worthy upgrade list for all cars. Many OEM cars these days are coming with "EPAS" systems from the factory, which makes for aftermarket electric steering assist solutions that are numerous and proven - since many are just re-purposed OEM systems. This means they can even be cost effective. And lighter. And no longer based on flammable, high pressure fluid that robs power from the engine to pressurize. Win!

A recent LS1 mock-up (October) with a set of accessories that does NOT have a power steering pump

And while it might seem simple to run any old LSx engine without a power steering pump, it was actually pretty tricky. This particular accessory drive arrangement was figured out on our FR-S LS1 Alpha swap, with some help from the itnernets plus some custom machined bits made here at Vorshlag. That car has an electric assist in the column, so it did not need the pump.

We couldn't find a factory set of LS series engine accessories without the P/S pump, so we went with a proven version that had GOOD front clearance (shown above on the FR-S LS1) and narrow packaging, then the normal main serpentine belt routing was changed to bypass the missing power steering pulley. To accomplish this an extra idler pulley was added, and things were moved around to give proper belt wrap on each pulley - especially the balancer (SFI unit secured with a massive 12-point ARP bolt). We took some measurements then borrowed this set of accessories from the FR-S and test fit onto the built Miata LS1 motor, it fit great (see images above), so we're replicating that set-up now for the Miata. It took a few iterations but we finally got the right length belt (these were the "almosts")

Motor Mounts and Transmission Crossmember Design - With A New Twist

Once the newly modified, de-powered NB steering rack was mounted to the subframe with some beefy, fabricated brackets (see above) we wanted to then lock down the designs for the motor mounts and transmission crossmember. But now that the tubular subframe was built and the rack was tweaked to fit the C5 spindles, Ryan saw some extra room and tried something I didn't expect... he put a Tremec T56 6-speed behind the LSx mock-up motor and stuck it back in the car. Again. Yes, after all the testing and trouble we went through to make the Tremec TKO600 5-speed fit, he went and stuck a T56 in there.

I had told Ryan when he came on board at Vorshlag that the T56 would never fit this car, both because we tried this transmission before (with the OEM crossmember, and then a cut up OEM crossmember) as well as the fact that all of the other LS1 swap kits for the Miata require cutting the tunnel to make the T56 fit this car. "Waste of time."

Thankfully, I was wrong this time. Now the bigger, stronger T56 did fit - and fit with room to spare! Apparently in our previous T56 testing the Miata's OEM front crossmember was the limiting factor. That big, bulky plate steel structure moved the drivetrain up significantly, which is why the T56 never fits the Miata tunnel on most swaps without cutting the tunnel to make room.

Left: The initial LS1/T56 mockups were a bust with the OEM crossmember in place. Right: With the tubular crossmember we have lots more room

This is because the LSx/T56 drivetrain is being moved upwards inches from where we have our drivetrain. With our latest (version 2.0) bolt-in tubular front crossmember, the engine sits lower and so does the transmission, so now it fits. It still has ample ground clearance to the oil pan, which is tucked up just above the bottom of the crossmember and bottom of the Miata tub. The T56 shifter location lines up perfectly with the factory Miata shifter hole. Moving this drivetrain down worked another miracle, and it lowers the CG, too. Win-win.

continued below

Last edited by Fair!; 12-19-2014 at 07:41 PM.
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