Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

[Fair!]

Wanted to go ahead and start this thread for JJ's Miata. He has been running the car in EStock locally for the past few years and was ready for the move up to STS2. We are working with him via our Test Program to help develop 4100 shocks for the NA/NB chassis. AST has made many sets of coilovers for these cars in the past but we here at Vorshlag have not sold them in 4100 form yet (only 4300s). Here are a few pictures of the shocks then we'll move on to the install, initial test impressions, and setup discussion.


L: Long shocks are the fronts, short are the rears. Knob is for rebound adjustment
R: Lower bushings are spherical. Upper is made to work with the stock NA/NB upper mounts


This was one of the ride height iterations, which was eventually lowered more at the rear.


Left: OEM front is 14" long and 150#/in, rear spring is 11" and 90#/in (SOFT!). We are using 7" 60mm ID Hypercos, 550 #/in front, 350#/in rear

The dyno plots of these things were beautiful. We're going to dyno the Konis that were on here before and compare. We dyno'd some Koni doubles last week that had some pretty interesting results (like "non-working adjustment knobs").


click to enlarge

Above left you can see the AST 4100 Miata rear shock being tested on our Roehrig 2VS shock dyno. Middle, you can see Hanchey making a CVP plot. Notice the large force changes over the range of rebound adjustments - this valving package can deal with a nice spread of spring rates. Right, new dyno fixtures had to be built for the lower eye mount (1.800" width) but our standard upper stem mount fixture was used for the upper mount - this was made with a VoMo camber plate, of course!

http://vorshlag.smugmug.com/gallery/6717983_45S6v = Miata 4100 Install Gallery

[Nis01]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Anymore updates on the results of the 5100 series shocks for the miata?

From what I hear you will be producing a version of the 5100s without the remote resevoir for the miata? Any chance of an update with estimated production times? Looking forward to hearing more about these shocks.

[Fair!]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Pic of Jarrett's car at Pennington Field last month. The new rates and camber settings are working great.



The latest version in Jarrett's car has remote reservoirs on the rear...

[GotCone?]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Good stuff!

[Fair!]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Update after Feb 7-8, 2009 Test/Race weekend:

Okay, we finally got an event under our belt with the new AST shocks and stiffer springs. I have good news, but first, let me give a quick run-down of myself and the car.

I started autocrossing in my 1993 Mazda Miata at the beginning of the 2006 season. Since we have five clubs in DFW hosting AX events, I was able to get a lot of seat time. I raced in a local tire class (based on E-stock) for 2006 and 2007, switched to R-comps (and regular ES) in 2008, and decided to give STS (formerly STS2) a try for 2009.

I started with an SCCA stock-classed Miata and made the following changes in the off-season to prepare for my assault on STS: Racing Beat front sway bar and end links (replaced FM sway bar with stock end links), Borla cat-back exhaust (replaced cheapie exhaust), Sutton Spec Miata Straight 1.6 Intake, K&N filter, aluminum underdrive pulley, Raceland 4-2-1 header, TDR heat shield, HP+ pads in the rear, HPS pads in the front, timing bumped 4 degrees, and most importantly, AST 4100 shocks and coil-over springs. We are currently running Toyo R1R tires on 15x7.5 Rota Slipsteam wheels (the tires came on the wheels), but we plan to switch to Bridgestone RE11 tires before the Houston National Tour.

One of the rules for converting the car to STS2 was that I had to keep it drivable on the street. Not only do I drive this car to events several hundred miles away, but my future fiancé and I enjoy occasional day-trips in the car. So, I could not make any modification that would compromise this rule. With that in mind, we originally went with 550 lb springs in the front and 350 lb in the rear when we initially installed the AST shocks. Based on my experience with my previous Koni Sport shocks (great shocks, for the price), I was concerned that even this would compromise my ride. However, I was floored by the ride with the new setup. Even with the stiffer springs, the AST shocks made the car ride better than stock!

We used the autocross school hosted by the Texas A&M Sports Car Club on Saturday (Feb 7, 2009) and Sunday’s (Feb 8th) autocross event to test the car on a course for the first time. After testing on Saturday, we decided that moving to 700/450 springs would yield an even bigger improvement for Sunday’s event. Again, I was very apprehensive about the ride quality, but I again turned my car over to Terry and Brian’s (of Vorshlag Motorsports) capable hands on Saturday night to make the changes before Sunday. When switching to the new springs, Vorshlag also revalved my shocks so I only needed to run them at the half-stiffness level for competition. (I will let Terry or Brian speak to that, since I would only look foolish.) I could tell right away that the stiffer springs and revalved shocks did not hurt my ride quality on the street. It was the same, if not better. Again, I was just ecstatic that I could run such stiff springs with the AST setup and still have a great ride on the street. There is no way that I could have accomplished this with my old Konis.

The car was incredible at the event on Sunday. While my normal co-driver (Thomas) was not able to make the Sunday event, I was able to pick up an abnormal co-driver (Brad) that morning. Watching Brad’s first run, I could not believe how flat the car was! Once behind the wheel, I was impressed by how responsive the car was and the sharpness through corners. It just felt so right and it was so much more fun to drive than my old “stock” setup, even on street tires versus my old R-comps. We won our class (I was less than a tenth faster than Brad). Since I had so many people tell me how great the car looked on the course it was not just my overzealous impressions of the car.

The drive home was very comfortable and I have no regrets about my change to the heavier springs. At this point, I highly recommend the revalved (Jerrett-valving?) AST 4100 shocks with 700/450 springs on any NA Miata used in autocross competition. Just incredible, and I can only imagine how much better it will get with additional testing and seat time.
------------------
Jerrett Jan

Thanks for the report, Jarrett. Nice job on the 1-2 finish at the car's first event in STS prep!

Big thanks to TurboTodd (a National level CPrepared racer) for loaning the Vorshlag crew and testers access to his shop the night of Feb 7th, which we were in College Station for the test/race weekend. We were able to revalve shocks and swap springs on several cars that night. The test facility at the TAMSCC event site is about as close to Nebraska's site (Nationals) as one could hope fore - the same vintage & size concrete airfield - and we'll be doing more testing and races there throughout the year.

We were busy testing/prepping with about 8 cars and even racing in the event ourselves so we didn't get as many pictures at this event as we would have liked, but here are a few below we managed to snap the morning of the event, in the pits. As with all of our Vorshlag Test Pilots that send us pictures, this car has its own picture gallery on our website: http://vorshlag.smugmug.com/gallery/6634337_fU9qH





Its so nice to see a car like this, that once had marshmallow springs & shocks and huge amounts of roll/pitch/dive, and turn it into a flat cornering, cone carving machine with just the right selection of parts - yet keep it civilized and usable for daily use. The myth is that you can't have both, but with higher end monotube shocks and proper valving you can have your cake and eat it too.

We'll make a point of putting the data logger in this car and snapping more pics and/or video of this one at the next event. The fresh Toyo R1R tires on the Miata felt SUPER SOFT - me thinks someone at Toyo has changed the compound.

[Miatamoto]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

We had to roll the fenders today for the 15x7.5 Rota Slipstreams and 205/50/15 Toyo R1Rs. The car feels great but I think we could use some higher springs rates.

I can't wait to try out the car at College Station. See you guys there.

[Fair!]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Some "After" pics:





Impressions from Jarret:

(Day 1) I played around a little on my way home ... and the car seemed to handle much better. There is far less body roll. Plus, at the current soft setting, the ride was the same or better than what I had before, so there is no problems with the street drivability. Any future customers asking about this should be told that when set to soft, it is no worse than stock, and possibly a little better.

Leaving Terry's, I took the turn under the bridge pretty fast. My left side hit some bumps in the road and made a squishing sound, but the car stayed very composed. In fact, other than the sound and a little vibration in the wheel, I would not have otherwise known, judging by the composure. Very impressive.

I cannot wait to try this out on an AX course!

---

(Day 3) I put the shocks on one click from full firm (for a test drive). I could tell a difference, but the ride was much better than the Konis on full firm with the stock springs. I did not have much of a chance to test the cornering, but when I did, it felt really well. We put them back to the soft setting for the way home and Leilane mentioned that she thought they rode a lot better than the old shocks and springs.

That's what we like to hear. We've more than tripled the stock spring rates, but it still rides as good or better with the AST shocks. Seems like a success to me.

[Fair!]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

Some shock install pics:





Corner weighing

Left: 50.1% cross weights with driver. Right: Locking down the spring platform

Quick alignment check:

Most corners were set at -3° degrees for initial testing

[Fair!]

Re: Vorshlag Tester Jerrett Jan's STS2 Miata (NA chassis)

If you've ever driven a stock suspended Miata you know how soft the factory springs are. We went the extra step and put the front and rear springs from Jarrett's Miata on our Spring Rater and checked them over 4" of travel. Here's the numbers:


Above: The testing of the rear OEM spring, from 0" to 4" of compression. At 4.000" of travel there was 348 pounds of load.

• OEM front springs = 14" long x 150 #/in (from our testing)
• OEM rear springs = 11" long x 90 #/in (from our testing)
• The new front springs = 7" long x 550#/in
• The new rear springs = 7" long x 350#/in

Left, above: The Miata's OEM rear spring had a staggering 14" Overall Length (OAL). When installed they had almost 4" of preload, just sitting at ride height!
Right, above: The OEM rear spring was 3.9 pounds. 7" long, 60mm ID Hyperco OBD coilover springs are 2 pounds