3/23/17 It's been a month since the last update here and a lot has been done in that time. I'll put some of it here, the rest will go into other blogs.
One bit of news is that Valerie's D4 will now be a turbo AWD one as well. And even though we started with 'stage II' engine spec for both, after talking more with George Dean, our engine builder, both motors will be getting turbo pistons, Carrillo rods and intercoolers - so basically stage III spec. They'll be able to run on pump gas to 8 psi (about 250-275hp) and can go up to 16 on race fuel (360+). So two out of three D4s we're building have basically 'creeped up' to the spec of the last turbo AWD car we built (and Tristan is considering turboing his as well). Which is great, because this is what the design is all about - putting down crazy power at super light weight (about 1,000 lbs) with AWD. It is the whole reason for having the engine on the side, and in a way a D4 configured with less potency than that is not really taking full advantage of the base architecture.
For a bit of perspective, the D1/D4 platform was designed as the ultimate trackday car - not necessarily a race car. The reality of trackdays is restictive passing rules. You can be as fast as you want in the corners (where most events don't allow or restrict passing), but if you're stuck behind a Viper or another high-power, cornering-challenged car, you're depending on them to be humble and lift on the straights to let you pass. Some are, many aren't. With a surplus of power and the AWD to put it down, the D1 and turbo D4 don't depend on kindness of others. If you want to pass, you can. Anyone. Anywhere. Neil (a D1 owner) has mentioned many times that GT3s don't lift for him, and he doesn't care :)
Anyway, building the cars is what we've been doing (these and several others at the same time). Machining of literally dozens of parts is now done. This one, the double-shear bellcrank mount, is particularly trickly. Because of the weird angles it takes seven different operations, but it's all done in a vise without fixturing. During two of the operations, locating features are machined into the part to facilitate holding it for subsequent ops.
I call the above pictured op 'the Titanic' :)
Our intern/customer Valerie has been a huge help in the process as a CNC operator - she's been running the machine (helps that all the programs were done some time ago) so I can focus on other things. It takes a think-before-you-do-ask-if-not-150%-sure attitude, and she's been great at it.
A bunch of other parts are now done as well, like the uprights for all the cars in progress. The D4 (as well as D1 and D47) uses our modular LT upright design. Like everything, we sell those separately and it's a good fit for custom cars in the 800-1,600 lb weight class.
Valerie's engine arrived recently. For Robert's car, we bought a brand new Hayabusa and are (still) parting out the stuff we don't need. In this case, I found a clean low-mileage 2008 motor on eBay. Both are valid ways to go about it, depends on whether you care that you have a brand new engine or not.
Since the turbo is here (and more on the way), we've started on the exhaust. Like everything it has minor updates from the earlier versions, to make things fit just that much better. It's how we do.
The primaries are equal within 0.1" at a nominal 22.1" each. We're using 304 stainless since we've had good experience with it in many applications. We did build a 321 header for the Pikes Peak turbo D1 but haven't really noticed anything different in how it works in our application. We use slip fits at the collector to allow heat expanson/contraction without undue stress or cracking.
We've also been working on improving the packaging and routing of the electropneumatic paddle shift system - there is now a single panel behind the driver housing the compressor, reservoir, checkvalve, regulator, pressure sensor and relief valve. More on the rest of it later. Like with many things we started by buying a complete solution and are now working incrementally towards something that's completely our own, designed to our needs.
We started out 8.5 years ago with farming out a lot of our processes. But being a low-volume customer we've inevitably (and somewhat understandably) ended up at the end of the line, always being pushed back in the schedule because of higer priority big paying jobs. Not complaining - it's the reality of business - but we don't like being at the mercy of others. So we've brought a lot of it inhouse where we can control the schedule, the cost and the quality. Every process we've done this with (design, welding, machining, and so on) the rewards have been tremendous with the only downside being a shortage of time. We've toyed with the idea of doing our own composites work several times, and now we're doing it in earnest. It's a learning curve but we've climbed a few and are not intimidated by it. Below are a couple pictures of test layups for carbon wings. Still a bit to go but getting there.
Overall, the shop is busy which feels good. A few pix of some work that is going on:
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