ADDING FRONT CAMBER, ROUND 1: VORSHLAG PLATES!
As mentioned above, we noticed that the S650 suspension was largely repurposed S550 bits - and we mocked up our S550 plate on top of the S650 tower on Day 1. So yes, of course we were going to put Vorshlag camber plates on at the first opportunity. After Track Test #1 (baseline stock everything), we dove right in. And while the Darkhorse optional handling pack has "adjustable top mounts", they have many faults, which we will go over below.


Before Track Test #2 we wanted to add what most folks will want as their first mod with any S550 or S650 they are going to track more than once - a set of Vorshlag camber-caster plates! Before that we took the car for a "spot check" alignment at a shop across the street. Their rear toe numbers were wonky (or so we thought) - and we show the "after" alignment, too.


This was a little shop we're trying to work with to be able to do our customer alignments, and we are making progress but they need to calibrate their machine's rear heads. But their front camber numbers matched what we saw on our SmartCamber tools. We went from -1.1 deg front to -2.8 deg with the camber plates maxed out. Let's show some installation steps...



Same procedure to remove and replace as on the S550 - put the car on a lift, front wheels and brakes come off, support the bottom of the strut, bust loose the two strut to spindle bolts, and then remove the 3 top nuts. Out comes the strut, we compress on a spring compressor, remove the top nut, swap to our camber plates and perches, then reassemble.


The optional" handling package" Darkhorse comes with an "adjustable" top mount, but it has several downsides: 1) it only has about 1/2 the total camber travel of our Vorshlag camber-caster plates. 2) It has no caster adjustment. 3) It is impossible to adjust on the car, so these have to come off to adjust. Every. Time. 4) Its still a big hunk of rubber in the top which will still deflect under load. It is far from ideal and we never bothered to test that maxed as its own "Track Test".


We used some of our tricks to push the top of the strut shaft under the top of the tower to maximize camber travel - which we can do for almost any strut, when you aren't allowed to "cut the towers" with our tower cutting fixture. For SCCA "STU" class we cannot cut the towers, so we left them alone and it did not affect our total camber. We WILL get more camber once the front ride height is lowered and via the MCS struts' slotted mounting holes - and as you can see from Track Test #2 (above right) we DO need more front camber... the accelerated front tire wear proves this also.
NEW WHEELS FOR SCCA TIME TRIAL T2 + SOLO STU
We have noticed heavy front tire wear after 3 track days (2 drivers per) and the factory Pirellis are both expensive, less than 200TW (180), and don't come with much tread depth (4/32"). As quick as they are on track, I suspect that the Yokohama A052 (which comes with 8/32" of tread) is going to be faster. All costs below are from TR wholesale, but they aren't much cheaper than TR retail when you factor in the "free shipping" the retail site passes along.


We looked at two competition classes for this car to run (SCCA Solo STU and SCCA Time Trial T2 - see last entry in this post) and made a compromise decision for our first set of aftermarket wheels for the DH: These forged 19x11" VS-5RS wheels in ET52 with a brushed clear finish, plus four 295/35R18 Yokohama a052. STU limits wheel widths to 11" and I didn't want to try to squeeze a 305 or 315mm tire onto an 11" wheel. I was also worried that the 18" wheels would be really easy to catch a rock between the barrel and the caliper...


The 295mm tire is also a tick taller but that could help gearing at some key tracks and for autocross. Might not be the last set of wheels or tires we order, but it will be what we test with next. You can see the weights these 19" wheels and tires above right - dropping nearly 10 pounds per corner while gaining 3/4" more tread width than the "315" factory rear tires.


This is another reminder that THE NUMBERS ON THE SIDEWALL MEAN NOTHING - we always look at published measurements, and remember to check what wheel width it was measured on. The staggering differences between this Yokohama "295" and this Pirelli "315" are shown in this video, which you can click on above.

It took some crazy long wheel studs and spacers up front to fit these 19x11ET55 wheels to the Darkhorse, but we will show that step next time.


I am skipping ahead a bit here but it applies to this section - the stock tires are VERY short lived. The front 305/30R19 Pirellis got trashed after just 4 track days, with much of the wear likely happening at Track Test #1 when it only had -1.0 deg of front camber.


These 180TW tires aren't legal for the two classes we plan to run, and the front replacements cost me $1100 shipped (wholesale), but I went ahead and bought another new pair. Why? So we could test new Pirellis tire back-to-back against new Yokohama A052s. Sure, we could have just tested the A052s on the same track and compared times from differing days, but this way it is a better, more scientific test. Stay tuned for that next time!
CHASSIS DYNO TESTING - OCT 11, 2023
Less than a week after picking up our 2024 Darkhorse we had only seen a few dyno DH dyno videos, and each one was flawed in some way, some sort of "issue" that prevented a realistic number. I called our friends at True Street Motorsports to schedule some pulls on their DynoJet 248 chassis dyno. They had dyno'd an automatic trans Darkhorse already but it had some limitations and could not make pulls in the 1:1 gear (7th out of 10 on the 10-speed auto).


Our dyno pulls were in the 1:1 gear on a 6 speed manual (5th), so no automatic / slippage / excuses. The bone stock engine made 449 whp STD / 440 whp SAE. I show several pulls in the video below. Sorry for the cheesy video quality - but when asked online, people said they wanted to see more videos from us. Be careful what you ask for!

We then swapped in the K&N filter replacements on the dyno, made pulls, and it consistently lost 3 whp, so we un-did that filter "upgrade" for now. We left the "carbon traps" inside the intake tubes, which you can see below right. I've seen folks claim that removing these is worth +10 whp, and others that say they lost power. I mean they cannot HELP add airflow, but we're going to leave all of this alone until HP Tuners make a custom tune available for this car.


Since NASA and other racing groups that require dynos want to see SAE correction factors on Dynojet chassis dynos, we went ahead and showed the SAE versions of the stock (below left) and with the K&N "upgrade" (below right). We have used this same exact chassis dyno at True Street for every Mustang we have ever owned, so there is dyno consistency there, too.


This 440 whp number is tiny bit more power (+5 whp) than we made in stock form on our Gen3 Coyote powered 2018 GT, and about even with our Gen1 Coyote in our 2011 GT with headers, exhaust, and a cold air and tune. I feel that we can add more power to this Gen4 Coyote with the typical bolt ons allowed in the classes we want to run (long tubes, cold air and a tune). The 2018 GT made 435 whp SAE in stock form and 474 whp SAE with long tube headers, cats, CAI + a custom dyno tune (+39 whp peak gain). I feel like the Gen4 will respond similarly - stay tuned for that.
TRACK ALIGNMENT AND PREP BEFORE TRACK TEST #2
It was late October and my shop manager Brad was on vacation, and I just didn't trust the alignment shop across the street's work yet. We left the old 19x11" Forgestar wheels and crusty 5 year old Bridgestones on the car that we installed for the dyno test (so as to not trash the stock tires with unnecessary street driving cycles) and drove the car to BSP Motorsports, who does our performance alignments. And sure enough they found some issues that needed to be fixed.


Turns out the Before alignment numbers they took (ie: untouched out back - from the factory) had some wonky rear toe issues, which they sorted. They dialed in -2.67deg front camber, which had gone up to -2.85 on one side up front, but we pulled it back to match. Then they dialed in -2.0 deg rear camber, and set the rear toe at the ".28 deg total toe in" that I like on S550 cars.


We picked up the car and back in the shop, Stephen, our operations manager, helped me swap back to the stock wheels, which I cleaned and added aluminum tape to the stock stick-on weights (they were already starting to slip around). With the stock Pirelli tires aired up, it was loaded into the trailer for the track test.
TRACK TEST #2 - NOV 3, 2023
I hauled the Darkhorse to MSR Cresson to tackle Track Test #2 on a cool Friday morning. I brought two friends with me to help (Jason and Paul), since I had knee surgery one week earlier and was still in a knee brace, hobbling around. I bribed them both with laps in the DH, and Jason took me up on it.


I took the DH out in the very first stint, but sadly with 1/2 of a tank, so it started to fuel starve right as the stock Pirelli tires "switched on". So I came into the paddock, tossed 5 gallons into the tank from fuel we brought, bled the tires down to 33 psi hot, and rushed back out there and took 2 more laps. And that's all I needed. This was the first time I had experienced fuel starve in the car.


The Darkhorse REALLY woke up with some fuel in the tank, and the tires switched on for my first hot lap on the second part of that stint - where I saw a 1.1 second drop from the already outstanding Track Test #1 best lap of 1:20.6. Initial turn-in was improved as was the overall handling balance at all speeds. What used to be a slight push was now neutral, just by going from -1.1 to -2.67 deg front camber and to -2.0 deg rear camber. This lap below tells the story.

After that 1:19.5 lap followed by a 1:20.2 lap, I came into the hot pits and hot swapped driving duties with Jason. He went out and took a number of laps in the same session, then we loaded up and were gone by 10 am. A quick test but it was very informative!


As you can see, my first few laps weren't fast, but I was in some traffic and fighting fuel starve for the first time. It is REALLY bad once you load the tires up hard in a long left-hander, and the MSR 1.7 CCW course has several long left-hand corners. With 3/4 tank of fuel or more, it was fine, and I found that fast lap immediately.
Jason has been out of a race car for a bit but he took to it quickly and enjoyed the laps. He and I both commented on incredible balance and brakes this car has. Again, the only mods were Vorshlag plates + track alignment as well as our brake cooling deflectors. These 18 laps were all made in the same 30 minute session and none of us noticed ANY brake fade.
ADDING FRONT CAMBER, ROUND 2: SPL PARTS FRONT ARMS!
If the pace of development doesn't seem "ultra fast" you have to remember, this was all done in THE busiest part of the Time Trial season while I am competing in Trigger and Amy is competing in her 2023 BRZ, so we're running a LOT more track events than you can see here (we did a total of 29 track days or competitions in 2023).


At one of the NASA events we attended in October (the day after my knee surgery) we ran into the guys at SPL Parts out of Austin. Sean and Turner are both the NASA Texas Time Trial directors and the guys who design and build the SPL arms, and they wanted us to test fit the S550 arms to see which of 3 optional tapers the S650 Darkhorse used - or if it needed a 4th iteration.


These are the same front lower control arms that fit the various S550 Mustang models, and this was the first S650 these were ever tested on. Of course I took weights but you don't do this to drop "ones of pounds", you do these arms to gain more camber and caster adjustment, as well as remove some LARGE rubber bushings - which deflect under braking and lateral loads. This part above is the TC rod, which is used to alter caster.
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