09/03/2010 I had to look at the blog to figure out when was the last time we ran at PIR and it was exactly a year ago, at the Lotus event just like today. A few things have changed since then and this time we brought out the dp4 and the dp1/e in the Mothership. Some friends came out as well so our space had an interesting mix of cars around it. These included an Exige S240 (yes that's Kermit), a classic Mini and a Cosworth RS.
The main goal for today was to test a wing on the dp4. I've had a few conversations with Wayne at Stohr and he was saying that without a wing their cars are nearly undrivable and that I'm going to need one too. Of course if we do go with a wing Wayne will end up making them for us so he has a motive - but the first one is free :) He graciously let us borrow an old wing off of one of his DSR cars. Couple days ago Tristan fabricated an adjustable mount that would let us try several angles and elevations. With the hardware ready we came up with a plan and now we just need to do it..
In the first session I went out wingless just to set a baseline. It took a couple laps to warm up the tires (car moves around a lot when they're cold!) but when it felt like some heat was in the rubber I started progressively upping the pace. And promptly spun it coming out of the chicane - an obvious driver error trying to carry accleration and lateral g over a set of bumps. No damage done though and I simply pulled back onto the track and continued on. The car is still a bit edgy under brakes so I'm having to brake early and gently, relatively speaking. Lateral grip is good though I do have to pay attention all the way through a corner. Then the session is over and Tristan installs the wing for the next one, in the low/flat position first.
I go out in the next session and the difference is immediately noticeable - and huge! The car is now rock-solid under brakes and I can apply them a lot harder, being able to go in just past the 300 ft marker into the chicane before braking. It is unflappable in the corners too an the g forces start reminding me of my days flying aerobatics - over 2g sustained. The car is way better than me now and I'm not using all that it can deliver. I'm certain that it can do turn 10 flat out but I'm still lifting for it, although even with that I'm taking the turn at 100 mph flat which is considerably faster than anything I've logged there before (80-85 was more typical in other cars).
Mid-session I pull in to have Tristan change wing angle to our 'high' setting and go out again. A bit more stability along with a bit more drag as evidenced by shift lights coming on a couple hundred feet later on the straights. It is a hot day and my induction system for the engine at the moment consists of a foam filter sucking very hot air from under the bodywork. Far from optimal and we're only getting about 117 mph top speed so power is way down. The original dp1 prototype with this very same engine went 18 mph faster at this track - it had a scoop directing outside air near the filter. Of course what I need is to develop a proper airbox which is definitely going to be standard on the production cars. And we need to check the engine, just in case.
Next we tried a higher setting at both angles:
Up higher the wing operates in cleaner air and should be more effective but it didn't feel too different. There was no significant difference in top speed, less than 2 mph from fastest configuration to slowest. Here's a video of a lap. For the final session we went back to low/flat setting that was actually lower than the initial one but moved the wing back about an inch. M got to drive the car in the last outing. She had driven Kermit earlier in the day and now I jumped into the Lotus for a comparison. What a contrast. Kermit is a very fun car on its own and is the ultimate streetable Elise but after the dp4 it just feels sloppy, soft and slow. I'd be braking into the chicane at what feels like a conservative rate and the ABS is trying to kick in. Then through the turns the car moves around, slides and squirms. And this is after putting aftermarket shocks on along with doubling the stock spring rates. I suspect the tires are at least in part to blame and we'll try a different set on the car later.
The comparison really brings the dp4 value proposition into focus. For half the price and much lower maintenance cost you can go faster and have way more fun. We just priced replacement front rotors for the Lotus and they're $798 EACH, along with $275 for front pads. Rotors for the dp4 are $75 each and pads are $50 per set. Plus it needs them less often. The entire one-piece dp4 body can be replaced for 1/2 of what just the front clam shell on the Exige costs. So you could get a $65K Exige which is compromised both on the street and on the track, with high maintenance cost and no way of getting home if something went wrong at the track. Or you could get a dp4 with trailer AND a nice $30K sedan of your choice to tow it with, have more fun on the track and be more comfortable on the street without risking getting stranded at the track with a broken car. Same money. I know which I'd rather have.
All that said, I have to admit that Kermit does look great :) It also makes every street drive a special occasion which is both good and bad. The good is obvious. The bad is the fact that parking it is a very stressful endeavor, both getting it done with no rear visibility and leaving the car there knowing there are no bumpers and that SUV drivers can't see it. Lane changes are a pain as well.
Now of course I'm faced with designing a custom wing for the dp4 that both works well and integrates better into the aesthetics of the car. I already figured out the mounts so the wing can tilt up with the bodywork and I have a general idea of how it'll work and what it'll look like. Just need to make it happen. That and the airbox.
A very good day overall. At Laguna, when I asked Jonathan Frost what would let him go faster he replied 'stability'. With the shock changes and the wing we now have that in spades. Should still sort out the power issue, but I'm now eager to find out what a better driver than myself can do with the car. I would also feel confident having just about anyone drive it now - you only need to be a pro to be very fast. Just to have fun, be safe and still go rather quickly is within any trackday driver's capability. Which is what the car is about.
09/13/2010 It's hard to keep current on everything going on so the updates are somewhat random in the absense of major events. There are several client projects in progress but lots happening on the dp4 as well. We received the new 'wave' rotors, they're a little bigger OD but a pound lighter than the old ones. We'll see how those work.
Test-fitted the existing body on the R1-powered car being built. It fits although clearance to the engine is pretty tight. Par for the course for me :)
Also got new custom-valved shocks in from Shock Shop. Since the Ohlins ST-44 that I was previously using are no longer available the new choice is Penske 8300. Pretty nice, light and looks good too. Originally I was looking at using the new Ohlins TTX36 but Chris has tested them and found that he can't get the damping forces he needs from that design. Ohlins have not shown any interest in resolving the issue and Chris' valving has been proven to work so Penske it is.
As part of the aero makeover I've been looking at the floor and realized that the side portions of it might actually be counter-productive. On a flat-floor car the diffuser is fed mostly from the side so it needs a smooth 'ramp'. But in this case it's a front-fed tunnel and entry of side air is undesirable. However the side portions of the floor were still serving as 'ramps', something predicted by CFD and confirmed with oil/dust traces in real life. So I decided to eliminate them and see how that works.
This saves about 15 lbs, eliminates complexity with supports, leaves room for jacking points and generally makes life easier. Of course functionality is still subject to verification and test. Next is fixing the induction issue and making an integrated wing for the car. All of it has been designed already, just needs to be fabricated and installed.
The learning curve with this design is pretty steep and satisfying in many ways. Of course it would have been nice to just hit it perfect on all counts right out of the gate but then I wouldn't have known why it works. What I'm learning now will be applied to all the stuff that's in the pipe and yes changes are already being made to designs still in CAD. Lots of unanswered questions remain though. Fun.
09/24/10 Among the many things happening is an effort to bring the dp4 (and later the other cars) to the virtual world. We've teamed up with Maher Solutions to create a dp4 model for the rFactor PC sim. rFactor offers an excellent level of realism and from the early results it looks like it will be a useful development tool with enough access to the inner workings to make meaningful changes and understand the results. And of course it will give people around the world a chance to 'drive' our cars at a racetrack of their choice :)
A fair bit of work remains before the car is ready for public release but the progress is encouraging. PIR is among the tracks in rFactor and running simulated laps letting the computer optimize the line it comes out with a theoretical best of 1:09 with chicane. This is about 2 sec off DSR lap record and since dp4 is very similar to those cars it should be an achievable target in real life. In fact that is our end goal for the development program, to post a PIR lap time under 1:10. But it won't be with me driving, I'm not that good - this is SCCA National champ level. I do plan on getting under 1:20 once we have the aero dialed in. The simulation does confirm that our speed on the straights should approach 135-138 mph, which is consistent with my own calculations and the DSR/F1000 data. So right now we're a whopping 20 mph down from that and the hope is that the induction changes will go a long way towards solving the issue.
Meanwhile, back in the real world we are making numerous updates to the prototype and moving forward with customer cars. Prototype tweaks include changes to bodywork and floor, exhaust and suspension setup.
The original exhaust system was hastily cobbled together from bits of the dp1 proto exhaust (reuse, recycle) but now we're at a point where it needs to closer resemble the production version. We also have some new shielding material on the way that should keep exhaust heat contained a bit better. Weather permitting, next track test is October 3 at PIR.
10/01/10 In preparation for the next test we made a number of modifications to the bodywork. Enough that it would require a respray. So it was a natural opportunity to see what the car would look like in a color other than black. This prototype bodywork would need many more hours of prep before any half-decent painting effort would make sense so all we did was sand things down a bit and spray a coat and a half of red. Even in low-res pictures it's obvious that the surface is rough but it does give an idea of how the shape would work with the color. I'll take more pictures Sunday at the track, outside the confines of the shop.
Overall I'm pretty happy. Next is mounting the wing. We now have a pre-production wing from Stohr and today after doing a half-dozen iterations in CAD we fabricated some mounts. Production version will be similar except all laser-cut and podercoated black.
It gets attached to the car tomorrow, which is when we go to retrieve the trailer from storage, pick up the dp1/e (it'll also be doing some testing) and generally get ready. More soon.
An interesting side note: red is a fairly finicky color to display on a computer screen so I tried a few different machines and browsers. What I found is that while IE was reasonably consistent across the board, Firefox rendered the color as orange on one machine and purple on another. On the same screen I have IE window that looks reasonable and FF window that looks like Barney. Odd.
10/03/10(updated) Another test day and again we are running both dp4 and dp1/e. On the agenda for the dp4 is testing the changes made to induction, wing and floor. This is a lot like work :)
The day started out with slight drizzle from the low clouds so we actually sat out the first session. After that, I ran in Advanced and M ran in Intermediate so the car ended up doing back-to-back sessions, just stopping long enough to swap the foam seats. We've determined that it uses about 2 gallons of fuel per 20-minute session so the 5-gallon tank is enough for the two consecutive sessions and then we refuel while Novice is on the track. Works out.
First thing to check was stability under braking, which is a good indicator of downforce. Unfortunately the car is not as stable in this trim as with the previous configuration. So we had a few things to try. First was putting endplates on the wing. In one session I tried using airtabs as endplates, thinking the vortex might act as a 'fence'. The difference was definitely noticeable both to me and M but still not enough. So next we tried hastily-hacked-together aluminum endplates which worked better.
Conclusion: we need to widen the wing (this one is 8" narrower than the one we tried previously) and we'll need endplates on it. We were going to try running the 'old' wing for a direct comparison but after doing 6 sessions the chain broke ending the test day for the car.
There was considerable warning that the chain was about to go, both visually and sound-wise. You can hear it clearly in the video (I'll post it shortly). At least it's obvious in retrospect. So now we know a few more things. Looking at the broken chain it was clearly overheated - something that I suspect started when it was too loose, before we updated the chain guides. Nearly all the o-rings are gone and the chain is discolored brown and blue (compare with new below).
This could have been easily detected had we looked for it. Lesson learned. The good thing is that the chain guard did its job and aside from knocking the clutch master cylinder off the engine there is no damage. Next version of chain guard will address that also. This does remove the anxiety of not knowing what happens if a chain were to fail and how to tell that it's about to.
Other things - with the induction changes we picked up 7 mph top speed but the engine still sounds unhealthy. We accidentally overheated it idling a while back and while it still runs I think a thorough checkout is in order. The engine has had a long and tough life, starting out in the original dp1 proto (with no break-in) and continuing on in this chassis. Between the top speed gain and the downforce loss the laptimes only improved about a second, with the best of 1:24. But it is clear that the car has a lot more potential, I wasn't using all of what it can do now and we can still improve it.
Besides the induction changes I added some heat shielding internally and the result is pretty dramatic. The shift knob used to get too hot to use without gloves, now it stays completely cold. The heatsoak from the air around the headers probably contributed to the chain's demise as it was in the direct path. Lots learned today.
I do like the car in red and I think with this color it looks better with the wing on.
There was a lot of traffic both in Advanced and Intermediate groups but basically we passed everything in both. M had a nice 'battle' with a Z06 Vette and he actually passed her at first but she got the lead back and pulled away during subsequent laps. She later mentioned something that was my observation as well - after a clean lap if you get stuck behind a normal car in the corners it feels like you're on a sunday cruise. The dp4 is a fun device :)
UPDATE: Here's a video compilation from the day. I tried to illustrate the pace difference for clear lap and typical traffic although video doesn't do justice to the g forces (nearly double on clear track).
10/07/10 Did a compression test on the engine and sure enough, while first three cylinders read about 140 (should be 160), the fourth is only 65. So out comes the engine.
Hopefully we can get it fixed in the next two weeks which is how long we have before our next scheduled test day. In the meantime I looked at how well the aerogel insulation was working. Too well. Wrapping the slip joint springs under the stuff is not a good idea as it turns out. They get so hot as to completely lose their heat treat and become useless. So, a different approach - we'll get the exhast ceramic coated and then use shielding selectively on surrounding components leaving the exhaust itself at least somewhat open to cooling air. So the parts are now at the coaters and I'm waiting for quotes on engine work from a couple builders. We have no time to mess with the engine internals inhouse.
Among other changes the wing is getting widened by 8", a few chain guard components are getting redesigned and made for better function/performance and a number of maintenance items need attention. With luck (and much effort naturally) we'll get everything done in time.
10/17/10 Just a quick update. Parts are starting to tricle back in. The head is cleaned up and rady for assemly. Exhaust is coated. We chose 'tungsten' for color this time, it's basically a dark grey. Question is not if or when it will discolor (yes and right away) but what it'll look like when it does. We'll know soon enough.
At this point we're still waiting on a few gaskets from Suzuki and some updated machined parts. As of now it all still looks very doable for next wekend.
10/20/10 Only a day and a half left until we have to leave for ORP for the testing this weekend. Head gasket showed up late this morning so Tristan bolted the engine back together. Then he installed the new clutch slave cylinder that the machinists delivered to us Monday and new chain guard that we got from laser cutters today. Now the engine is back in the car. We have all day tomorrow to finish it and get it running. That's a luxury :)
The slave cylinder (the aluminum billet piece to the left of the sprocket) is now 3/4" diameter (up from 15mm), is much sturdier and works together with a steel guard that should keep it from getting knocked off should the chain break again. After we test this setup the parts will be available for sale for people using Hayabusa motors in cars. Production parts will be anodized and plated, of course.
Tristan won't be going with us this weekend (he's going elk hunting) so it will be interesting for M and I to run the dp4 and most likely the dp1/e, completely on our own. Since the goal is to make this a single-operator trackday car it's a good test. Hopefully the prototype is sorted enough by now to let us do that. Of course we are still very much in the evaluation and data-gathering mode and we'll be testing several new things including different tires and brakepads. So it'll be quite a bit more work than just a hop-in-and-drive trackday. Unfortunately the weather is looking rather iffy but I'm hoping that over two full days of open track we'll get at least some seat time.
One of the things we'll be testing is the wider wing. We decided to make the extensions level instead of continuing the curve. It came out rather nice. Still have to make endplates for it and have to remember to bring material for different size gurneys to try. With luck we'll see how all this works.
10/21/10 Work continues. Tristan finished installing the engine and the exhaust and fired it up. It actually runs and even sounds like it's running on 4 cylinders and not 3. Cool. In the meantime M fabricated endplates for the wing and installed them.
Things are also moving in the virtual world, we now have AWD and two stages of turbo powerplants in rFactor (based on dyno plots I found online) as well as a lot more detail. The latest wing will be incorporated shortly. In the picture below the car has our recent test wing, complete with hastily hacked endplates!.. A fair bit of effort remains but I'm very much looking forward to when we can release the car. I'm really impressed with the level of realism the sim provides and Maher Solutions guys are doing a great job of getting the details right. I've now sent out an early version for beta testing and the feedback has been very useful. Yet another great learning experience. Looks like the sim will be a nice tool for evaluating setups. Yes, I think it is that good.
A slightly amusing bit - when Maher recorded the sound for the car we were having engine issues and you can pretty clearly hear the misfire in the sim. We may re-record the sound later but if not then it might become a piece of trivia that those in the know will know... :)
At the end of the day we went and got the trailer from storage and picked up the dp1/e from RMS. It seems no matter how many times I back the Mothership into the shop it's always a challenge. Perhaps the fact that I'm always dead tired when I try this has something to do with it. Or maybe we just need a more compact solution.
10/23-10/24/10 (updated 10/25) A two-day test outing at ORP. This is the first time we've run at this track without also hosting the event. This weekend was organized by a group who call themselves "the Porsche Train" - driving down from Canada and mostly bringing Porsches (up to and including a Carrera GT), the reason for the name is obvious. Any concern over possible snobism disappears once you actually talk to these guys - they are a great group of enthusiasts, very down to earth, egos well in check and like-minded people are welcomed no matter what they drive. The PT guys run a similar format to what we've been doing at our events except no bikes - so it's open track, open passing with pointby, be courteous and have fun.
The weather was a known concern going in and we did get a lot of rain, wind and cold. But there was enough dry time on Saturday for both M and I to get some seat time.
I did about 10 minutes just before lunch, as the rain stopped and the track was beginning to dry. Then in the afternoon M went out for a stint, came back in for refuel and went out again. The weather continued to cooperate so I took the car out for a few laps to actually evaluate the changes we've made. The wing seems to be working although without load cells in the suspension it's hard to tell for sure. Plus it's cold and still a bit slippery. Still, I manage a 1:53 in traffic which matches what I've done here before in much better weather and clear track. Of course speeds at ORP are lower than PIR so aero has somewhat less effect overall and that's a factor as well.
One of the key goals today was to have other people drive the car and get their feedback. So we made some time before the end of the day for a couple test drives. Both came back with very positive impressions and the second driver, benefiting from a more thorough briefing on what to expect, got into 1:56s right away. It's nice to see someone just jump in the car and go fast. Plus it's very gratifying for me to see the car out there with someone else driving. It's a sense of accomplishment.
Also did a quick run in the dp1/e until one of the cells in the pack started overheating (I know the smell now!). So far the pack has had 3 cells that went totally dead and two that have been venting early. The moral here is that when buying cheap Chinese batteries, buy a few extra cells. Not entirely unexpected. The car again turned the best lap at the start and the comparison to the dp4 is interesting. The cornering is on par (stiffer sidewalls of the R compounds producing higher peak g on turn-in) but power is obviously way down. The result is a 2:11 lap (blue), still not all that bad. And clearly I'm overbraking for some corners because the 1/e can take them nearly as fast as the 4.
In the evening, a dinner at Wild Winds Ranch hosted by the PT group, then back to the Mothership for the night. It's nice to have the living quarters there. With rain and wind hammering outside, the shelter and comfort are all the more appreciated both at night and during the day.
Sunday it was supposed to rain the whole day and aside from a couple brief sunny breaks that's basically what it did. I caught up on some work (ORP now has free wireless internet) and M went out passengering to get more familiar with the track. She talked to a few people and came back with the announcement that she had arranged for a pro to drive the dp4. Despite the cold and wind the track was somewhat dry at the moment (albeit with heavy clouds lurking nearby) and I was eager to see what the car can really do here, so we rolled the dp4 out of the trailer and got it ready. The driver, B.J. Zacharias, was there to provide coaching to some of the PT guys. It's been over 10 years since he's driven anything similar but once he was out there it was a good illustration of the difference between a pro and a mere advanced trackday guy like myself. On the 4th lap in a car he'd never seen before, with traffic, cold and rain starting again, B.J. got into 1:48s while 'taking it easy' by his own description. The data is below, should be obvious which is which.
Yes, a determined hand can get nearly 4g transient out of soft sidewalls :) The most obvious difference is down to throttle usage, just getting better drives out of corners and staying on it longer. B.J. is confident that with some practice and better weather a 1:40 flat is well within reach. Which is what I thought too but it's nice to hear from someone who can actually do it :) He also said the drive was the highlight of his weekend - that was nice to hear too.
The video equipment was uncooperative both days (ok, user error in failing to charge fully combined with heavy electrical interference in dp1/e and failure to find a mounting spot that works on Sunday) so there isn't much new to post that's watchable. But overall this outing has been very useful. The main thing I walked away with is a confirmation that the car has lots of potential that's still untapped. So this is a car that's a lot of fun for an intermediate driver, challenging for the advanced and can keep a pro thoroughly entertained as well. It isn't something you'd outgrow anytime soon and yet you don't have to wait until you're 'better' to start. Which was the goal all along - a perfect trackday car :) Definitely generated a lot of interest this weekend. We'll see how much of that converts to actual sales.
UPDATE: I managed to salvage the video of the fast lap by cropping the hell out of it, the quality is nothing to brag about but it's still fun to watch - here it is.