10/30/12 The D2 has been getting most of the attention lately but every now and then we manage to make progress on our other cars too. The D4 design has been constantly evolving with everything we learn from this and our other cars being incorporated as running changes. With the experience of Pikes Peak behind us and with fresh feedback from current and potential customers, I wanted to make some updates.
The main one is updating the frame to add more side impact protection as well as improve manfuacturability and serviceability, particularly in AWD configurations. The most visible change is the extra bracing and increased tube diameters on the side of the cockpit, derived from D4PPS.
Yes, by all racing rules this is way overkill for a car this light but as a trackday car the D4 is likely to share the track with much larger, heavier cars. And some may see a hillclimb or two :) So the extra protection is an easy choice and only adds 8 lbs.
Other changes include better optimized suspension boxes, a new steering rack, updated drivetrain configuration, much lighter bodywork with aero updates, new CNC pedals with ball bearing pivots (shared with D2), removable jacking points that also serve as side-impact crush structures, bladder-type fuel cell as standard and so on (yes, in my 'spare time' from designing cars I work on making existing designs better ;). We're also working on offering a fully electronic paddle shift as an option, similar to the systems on the D1 and D4PPS. With all of the changes the car is now officially designated as MK3.
We did still have a MK2 tubing kit onhand and enough used and prototype parts to make a whole car. So I decided to let Tristan build one for himself before we update the chassis fixture to MK3 specs. He spends all his time building cars for other people so it's high time he got to build one of his own. He made quick work of the chassis, welding it up in less than two days. Now the fixture can be updated.
In the meantime the first produciton MK3 chassis is in the works, a Hayabusa engine has been bought and is on its way and a new bodywork is being built. We're hoping to complete that car right after the first D2 is drivable.
12/3/12 Now that the D2 has taken its first drive time to make progress on a couple other projects (don't worry, the D2 is still getting worked on, we now have 5 of them to build and deliver!). But first some exciting news - a D4 has set a new overall track record at at PenBay circuit in Taiwan, in its first competitive outing in Asia. Driven by Rodney Tu the D4 set a new fast time of 1:45.840. Second fastest was a 997 GT3 Cup, followed by another 997 GT3 Cup and a Lamborghini LP600 GT3 (one could buy at least five D4s for the price of one of those other cars!). Congratulations to Rodney on an excellent drive and a good start to D4 international racing career! Video HERE.
In the meantime, we've now taken delivery of the first MK3 D4 body - it is made from S-glass advanced high-temperature composite with Nomex honeycomb core. At 31 lbs untrimmed it's about half the weight of earlier bodies whch were coming in at 55-65 lbs. The styling differences are subtle and the unpainted state of the new body makes it hard to see... But overall it looks tidier and more compact somehow, at least to my eye.
Once we have it on a car and painted it will be easier to compare with the older cars.
The chassis fixture has been updated and Tristan is putting together the first MK3 chassis now.
Unfortunately the engine purchase fell through but there are plenty of others out there, just waiting to sort all the details out with the transaction. Always something...
01/12/2013 It's a bit of a juggling act (understatement ;) but we're making progress on several projects at once. The highest priority is the batch of D2s and everything which goes with that, but there's also Stiletto, some D1 updates, further Pikes Peak car development and of course the D4s. Building the last MK2 and the first MK3 frames side by side is a good opportunity to highlight the differences.
Note the much beefier tubing around the cockpit on the newer design. The MK2 frame already exceeded SCCA requirements for a car of its weight and was stronger than something like a Radical which is built entirely of 1" mild steel tubing. But keeping in mind D4's role as a trackday car that shares the track with full-size sedans I felt it would be good to go the extra mile. The MK3 chassis is 14 lbs heavier than the old version but some of this weight will be offset by savings in other areas of the car that are not safety critical.
Other D4 news is that we have made Penske shocks standard (previously they were standard only on the D1 and optional on the D4). They are custom valved and individually dyno tested specifically for the car by Shock Shop.
There are several other changes and upgrades that are part of the MK3 design some of which are pretty neat. I'm really looking forward to the completion of this car. Of course since it competes for time with all the other projects it will be a couple months before it sits on its wheels but that should be just in time for track-worthy weather.
01/19/13 The shuffle continues. It so happens that the D4 is what I took pictures of so this is the page that gets updated but they are all moving forward.
On the D4 front, we test-fitted the new slower steering rack. This has been suggested by several people who drove Pearl and thought the steering was too heavy and quick, and it's something that I've come to agree with. Of course in taking it apart we realized that much of the heaviness was due to badly sticking pivots (these are on Pearl only, production D4s have a needle bearing design that eliminates the problem). Still, the new rack, at 2 turns lock-to-lock vs 1.5 for the old one (for 30 degree angle at the wheels each way), is a good change. It also has less play and half the cost so there's that. To fit it I had to design and machine new mounts but now it's done. The usual 1/4" clearances have been reduced to 1/16" in all directions for this one but it still works. A bit of a pain to install as a retrofit but for new builds it won't be too bad. It's not a frequently serviced item.
Another reason the D4 work is taking place now is that we need to clear the layout table for the D2 frames. So while we're waiting for the rest of the D2 tubes to arrive (due on the 23rd) we're making the best of it in welding the suspension box mounts on the two frames in progress.
It's busy. Today was a Saturday which for me consisted of a meeting with a customer, several hours of CNC machining, some component design and several CFD runs which continue as I type this post at midnight (learning a lot with this!). Yes I can keep three or four computers very busy at the same time. Tomorrow is more of the same. Good thing I enjoy doing this stuff! :)
05/21/2013 The D4 is basically to the point where we take it for granted - it'll be there and it'll work. So when we bring it along the attention is usually on other cars. Our California trip was no exception. D2 as the new kid on the block has been the star of the show and actually has shown great promise in being another take-for-granted trackday machine. The D1 has been held back by noise issues with is 106db exhaust so Karl didn't get enough seat time to begin to use it. The D4 has been a backup - just jump in and go. This was the assumption as we set up at Laguna.
So it was a bit of a surprise when in the first session we got flagged for 97db. Ouch. At Thunderhill we did a sound check and got two readings, both under 90db. Due to a miscommunication I had assumed that the second reading was for the D4 but it turns out that both were for the D2. Fortunately Jonathan was able to scavenge a beat-up Supertrapp from the school's junk pile and I was able to figure out a way to mount it. Problem solved, 87.4db.
So Karl was able to go out and have some fun while the D1 was relegated to a static display. Here's a short video from one of his sessions.
This trip, having all three cars there, has really highlighted the differences between them.
By being the most conventional the D2 is the easiest for people to just get in and go fast. Everyone who has driven it (Pete, Karl, Jonathan) LOVES the car. Jonathan was able to quickly get into 1:35s at Laguna which is pretty decent for DOT tires and he feels that 1:30 is easily within reach with some tweaks to the brakes. That's before any aero is added.
The D4, while technically faster, takes some getting used to. It gets its lap times from high corner speeds and high g loads. If you're not calibrated to the corner entry speeds it's capable of it is hard to reach its potential. It expects skill, focus and commitment and rewards them greatly. Yes, one can readily drive it like a normal car but then normal car speed is all you'll get.
The D1 is like the D4, only doubly so (literally - having twice the power). It is capable of LMP lap times but, unsurprisingly, it is not something you do casually. This is really a dedicated enthusiast's car. We do have a development program planned focused on making it more accessible - lighter steering is in the works, as well as tweaks to aero and other systems. And we also need to add bigger mufflers to make it a more realistic trackday car.
So, for a casual enthusiasts or anyone wanting to drive on the street and/or carry a passenger, the D2 is the obvious choice (and it will pass sound at any event without doing anything). I'm not aware of any other car that can match the user friendliness or price for anywhere near this performance.
For people wanting a dedicated trailered trackday toy that is fast, reliable and easy and economical to maintain the D4 is the way to go.
The D1 remains the halo car that requires a substantial commitment on the part of its driver. Over the summer I'm hoping to benchmark what it can really do and that will take spending some time on getting the driver familiar and comfortable enough with its performance envelope to push the edges. It won't be with me driving :)
All in all a great trip and we'll be doing a lot more of this going forward.
11/01/13 Perhaps the final trackday for the season and just one of many lately for the D4. None of us have gotten any decent seat time in the last year or two - always customers to support, demos to offer, etc. This was our opportunity to just play and that's pretty much what we did, taking out the D4 for M, Tristan and Jay and the D1 for me. Yes, both fit in a 20 foot trailer :)
The car now has over 30 trackdays on it (lost actual count some time after 29), It's the most that I've put on any car I've ever owned and it's held up really well. Still, it will need some maintenance over the winter - engine needs to be gone through, everything checked out and cleaned. I'm looking at a number of upgrades also. An evolution of the Pilot Pod based on the D2 seat design, new generation pedals, different intake, a new electronic dash (also from D2 development), etc. Should be fun.
06/28/14 This is actually a cumulative post for everything that's been happening lately (I don't want to do separate ones). The reason it's on the D4 page is that about a month ago we got an order for a 'hillclimb' configuration of the car, with AWD, turbo and extra rollcage bracing. This gives me the opportunity to implement all the updates that came from everything I've learned with the D2 so far. More on that below, but first other items:
On the Stiletto, the decision has been made to go with the more 'traditional' windshield. The factors are many and I believe it's the right way to go for the car. More updates on that shortly.
On the D2, we received and tested the updated halfshafts as well as another stability tweak.
I put a full 2 hours of tracktime on the car at ORP and evetything worked well. The CVs do run a bit on the hot side, 300-320F, but well within the 400F+ rating of the grease. It's a challenging installation with angularity (due to inverted gearbox), high speed and tight packaging. By the narrowest of margins it does fit. As is tradition.
The stability tweak, basically replacing a street-oriented balljoint with a rodend to reduce compliance in the system, seems to work well. I did both skidpad and track and the car is very neutral and easy to recover if a mistake is made. The neutrality can be a bit intimidating actually because the limits are so high - it can carry so much corner speed with no indication of under or oversteer that it makes you wonder what will happen when it does break loose. Of course with only 4.5lbs for each horsepower there's enough thrust available to overwhelm traction in a corner anytime. When it does step out, as long as the driver is expecting it (should be, he's the one that just pushed the pedal!) it's easy to get back by just backing off a bit. Full lift throttle of course does make it step out more. Doing 'throttle ABS' in the skidpad setting was very useful actually, to see exactly how the car responds. Made me dizzy though.
The dash setup is evolving quickly and we've made numerous software and hardware updates. The car comes with the permanently installed display unit, a 'box' to talk to the rest of the car and a companion Nexus tablet for analysis of data that is wirelessly coupled to the display/logger. It can email a screenshot, upload data and diagnostics and download updates with a wifi connection.
Yes, that's 0.96 forward acceleration AND 0.61g lateral at the point in question. Peak values I was seeing were about 1.3g lateral and 1.2 g longitudinal, both braking and acceleration. Some may recall that this is my idea of a 'well rounded' car, with the traction circle looking like an actual circle (I know this may not make sense to some, there's always google ;).
Still a few things to iron out but this is turning out to be exactly what I had envisioned some time ago. No other system on the market does this that I'm aware of. Yes, you'll be able to buy it separately. Pete is running it in a BRZ right now as a test.
D2s chassis numbers 1-6 have now been delivered. The next three are being built as a bach. Next bodywork is a cool color, Azzurro California (found on Ferraris and Porsches). The pictures in the dark shop only give a vague idea but even in this setting I like it.
OK, back to the D4 (yes it'll be getting the new dash, as will the D1). We built a new Gen III frame and bodywork some time ago so they're all ready to go. I'm now in the process of making new suspension bellcranks and boxes, as well as crush structures, all based directly on what we've learned with the D2.
One bit of feedback I've gotten from numerous sources is that the D4 (and to a lesser extent the D1) looks too 'cute' due to its diminutive size and near-square proportions. So for the last couple of months I've been running various CFD scenarios at night to see how a more aggressive looking Pikes Peak style package would perform. Pretty well, it turns out (after several dozen iterations).
I run all the calcs at 100mph, it's a number frequently seen on track and is what I consider to be the most relevant range for track car aerodynamics. Through all the iterations I've gone from about 60 lbs of lift to over 360 lbs of downforce (yes there's a drag penalty). That's about where I want to be with this car, I don't want a crazy downforce monster (very few can actually drive those to capacity anyway and I'm not among them) but just enough to make it positively stick at speed.
It has become very clear a while ago that we need to increase our resources. Lots of projects are far behind schedule, only some of it is vendor-related the rest is just due to the fact that there aren't enough hours in the day for 5 people to get it all done. I was just going over the jobs that I personally hold at the company. Below is a partial list and at least some should really be full time:
General Management, Finance, Sales, Marketing, Customer Service, Mechanical Engineering, Electrical Engineering, Chassis Engineering, Styling, Aerodynamics, Pattern making, CNC Programming, CNC Machining, Safety, Document Control, Vendor Relations, IT, HR, Transport Driver, Test Driver, and so on (Blogger, too;). Try to fit all THAT on a business card :)
Others on the team have fewer titles but everyone contributes their share. We've had a couple great additions lately and it has already made a big difference, hopefully it's a trend we can continue. Things are getting done and it feels good.
On a different subject - some may recall that a while back I transferred the tooling and CAD for my very first design, the dp1, to Preble Highschool. I recently got some photos of the current versio of the chassis. It has been updated and evolved to fit the students' needs and is really all new, only the dimensions and layout match the original. I really like the solutions - clean, effective and realistic. Very happy to see continued learning taking place, it's the best 'second life' for the design that I cold have dreamed of.