23 Oct 2016

Bah, it took all day to sand the plug so there was only time for two coats of wax before the day was over. This type of composite construction doesn’t technically require a smooth surface on the plug – which becomes the inside of the final product – but because I know it was rough it was smoothed down any  way just because. There are still small low spots sprinkled about but they’re gentle and unlikely to affect airflow.

After applying the second coat of wax, the car was taken out – it was nice to drive her again! For the first time in over a year, gasoline was added, diluting the ethanol roughly 50/50 just to see how it ran. It should have run fine but even with an ethanol detector it was good to see that it still does no problem. There are plenty of back country destinations around here that don’t have ethanol* so it’s nice to know the car handles either. Also, 85% ethanol (“E85” around here) cuts fuel mileage by about a third, a significant dent in range, so knowing gas works is reassuring when low in the middle of nowhere.

*I don’t understand that lack of availability out there, the desert attracts all kinds of people with crazy off-road vehicles and the higher power ones run on E85 – which owners have to transport from home. Why the small towns out there don’t take advantage of that I don’t know. Instead, E85 pumps show up here in larger towns where it’s great for people like me, but makes zero sense for anyone else, short of those wanting to “buy American” at a premium,  since it’s not cheap enough to make up for the decreased range. I suspect there’s some sort of kickback thing going on with stations to install them because the only cars I ever see at the pump are one strongly suspected of running tweaked engines. It’s always fun to ask the STi and Evo owners about that and listen to them swear they’re stock. Of course they are 🙂

22 Oct 2016

Coated the foam plug of the largest section. Tomorrow it’ll get sanded then covered with mold release wax, though how long that’ll take depends how smooth the surface turns out, and how long each coat of wax takes to harden. If time is short then the first two sections – also coated today – will be sanded to see what’s what, or said another way, to see how many go-arounds of epoxy/micro and sanding might be expected before it’s deemed smooth enough to paint.

With both sections set aside to cure today, the car was warmed up (for the first time in a long time!), then an oil change done with full synthetic (mineral-based oil was used for break-in). The car was vacuumed out to remove as much foam dust as possible because I don’t want it blowing into my eyes while driving (never mind inhaling the stuff).

The last picture is a used “magnehelic” meter I picked up off ebay. It’s a very sensitive (1″ H2O) meter for measuring pressure differences, useful for testing airflow in ducts, intercoolers, radiators, but especially for determining proper placement for vents, measuring diffuser effectivity, airflow around wings, all sorts of interesting goodies 🙂

20 Oct 2016

Ordered enough fiberglass cloth to ensure stock for the last and largest subassembly. There’s enough carbon already on hand that should suffice for stiffening the larger surfaces (by the way, when fabricating, curved surfaces in composite or metal are much stiffer than flat). Expect a lot of progress over the next couple weeks, and after endless sanding, it’s on to paint!

In other news, Lulu is running a 30%-off sale through 24 Oct, code “OCTHIRTY”, book links: coil-bound and regular-bound. Lulu doesn’t notify authors when they have these promotions but I try to pass them on when I see it.

17 Oct 2016

Spent the day touching up the two front pieces to get them ready for a thin layer of epoxy/micro – a layer easily sanded in preparation for paint. Part way through that I figured the middle section should be riveted on as part of becoming a permanent assembly, so that was done. Then I figured there’s no point in fully prepping the front sections with the intercooler section still sitting there in foam.

First up was making a proper aluminum frame that’ll become a permanent part of the assembly, a frame so I don’t have to worry about the attachment points tearing out for whatever reason. It also allows a close tolerance on the fit-up between the composite and intercooler to minimize leaks. With that done, the foam was pushed into place and (not shown) a few areas had epoxy/micro added to bond the aluminum to the foam for now.

In the last pictures is this little guy I found at work  – “little” being relative because a praying mantis is really big for a bug at about 3″ long. It was really cool how how his head could turn just like a person’s and it was intimidating how he’d turn his head and track my movements. In this picture he’s looking at the camera upside down.

3 Sep 2016

Here’s progress on the intercooler duct. The 36″ x 72″ red fiberglass board arrived by truck in a 48″ x 96″ cardboard container! I won’t say what shipping was due to embarrassment since I didn’t notice the amount until it was too late. Anyway, the fiberglass paneling helps speed up fabrication – thanks to my brother for the suggestion. Cut to fit, it became the roof* and is flexible enough to follow the tubes down to the windscreen. The front half of the intercooler duct will get built on this and the ducting will drop down below the main roll hoop to connect to the section shown.

The next delivery included a big piece of foam and about 15 hours was spent shaping it. Moldless-construction means once the foam is shaped, fiberglass is draped over it, epoxy is added, it cures, then the foam is removed. As seen, a band saw sure comes in handy, and a die grinder, and sand paper, and sanding blocks, and a hacksaw blade, etc. Doing it over I’d buy thinner material and stack sheets appropriately instead of cutting it from one large piece. What you see here is probably 90% done, complete with a few goofs though they won’t be visible.

So what’s with the shape? A couple things. I learned that the inlet duct should be roughly 25% of the core area, which works out to 3″ wide as seen from the rear. That’s when it hit me, that it could be shaped such that my coveted rear view mirror might still be useful. So far it looks promising, check out the last several pictures. Mostly by coincidence, the intercooler duct lent itself well to having a minimal frontal area right along the rear sightline. The last picture is what I see from the driving position, where visibility goes right through the “waist” of the duct. The last picture was taken early during shaping, ignore the duct’s asymmetries.

Debating what to do tomorrow. On the one hand I’m kind of beat and am thinking of taking a day off and going for a drive. On the other hand I’m making great progress and hate to give up a day. On the third hand, driving tomorrow would be nice since it’s unusually cool here (for the first time I can remember, the first week of September isn’t the hottest), but uf course, cooler weather is good for working in the garage. Since Monday’s a holiday, that’s when all the motorhomes will be clogging the back roads, leaving tomorrow relatively quiet. I don’t know, we’ll see.

*I was right to be concerned about the roof; getting out of the car with it in place is a pain. Still haven’t figured out how to adjust my routine to make it easier.

31 Aug 2016

Ordered thin fiberglass sheet, foam, epoxy and flox. Building the foam form is the fun part; getting it ready for paint so that it doesn’t look like crap is where all the time (and complaining) comes in.

A few people have asked why an air-to-water intercooler isn’t used instead of ducting. First, what it is: an air-to-water intercooler setup consists of a water-enclosed intercooler, reservoir, pump, hoses, and a front-mounted radiator. Heat absorbed by the water is pumped to the front of the car where it’s dissipated by a separate radiator.

So why aren’t I using one? For the street or drag racing it works fine because the engine isn’t under boost very long. At a trackday or hill-climb however, it can be challenged to shed heat faster than it’s generated, resulting in high water temperature –  heat-soak – and then there’s how to get rid of all that heat once it’s in the system. Other negatives include increased complexity, cost, weight, reduces cooling of the regular radiator, and adds the potential for more leaks. While the air ducting is a project, it’s far simpler in the long run and can be run at speed for an unlimited time.

In unrelated news I ordered two new windscreens, a replacement and a spare. Several years ago I was on a group drive on mountain roads where it had rained the night before. The car in front kicked up a lot of sand and left my windscreen slightly sand-blasted. Every time I drive the car it bugs me, so that’s another thing on the to-do list. Lastly, the polyurethane showed up and the rear mount changed once again. Haven’t driven it but it’ll be better than the Delrin version.

Here’s the record-breaking run of the 1000 hp Nissan GTR at the 2016 Virginia City Hill Climb: https://www.youtube.com/watch?v=L9YMuQWVLL8

29 Aug 2016

First off, my brother did very well, placing third out of approximately 50 cars with a time of 3:22; the only car that beat him was that 1000 hp Nissan GTR and a McLaren 675LT. He took his GoPro 3 to record his run and not very surprisingly, it screwed him over by refusing to power up even on a full charge. He said he’s completely fed up with GoPros and I can’t say I blame him.

Someone asked why a turbocharged car retains more power at altitude than a normally-aspirated car:

As altitude increases, two things changed in favor of a turbocharged engine. First, lower air density means that the compressor has less load, so it naturally increases speed until it reaches a new equilibrium. Second, there’s also less exhaust back pressure (less pressure the exhaust has to push against in order to exit the exhaust pipe), so the turbine sees a larger pressure differential and spins faster as well. Both factors cause the turbo to adjust itself to a higher speed that self-compensates to the higher altitude. It’s not perfect though because the turbo is now compressing air at a lower pressure to a larger factor (a larger pressure ratio). Compressing the air more raises the temperature and in addition, the intercooler has less cooling air flowing across it, so the air entering the engine is warmer than it would have been at lower altitude. Even so, the end result is that a 400-hp turbo engine (measured at sea level) will still make about 370 hp at 6000 feet (without active control to make more), while an equivalent normally-aspirated engine will make about 330 hp.

There is however a negative aspect of turbocharged engines that can even the playing field: heat-soak, where the intercooler can’t keep up and the air entering the engine gets so hot that the ECU must back off on boost. This is a fairly common issue for lower and mid-market turbo cars, where they simply can’t stay at full boost for longer than perhaps 10 seconds. Most of the time that’s perfectly fine, but put that car on a 3-4 minute hillclimb and whatever power the manufacturer promised likely isn’t there at the top of the hill.

In other news, regarding the intercooler ducting and it possibly becoming part of a roof, I didn’t realize how much I use the roll cage when getting in and out. Getting in without the cage’s help isn’t bad, but getting out is, well, entertaining to onlookers; I’ll have to try some other techniques to see if it’s just a matter of a different habit or if it’s a real issue. I haven’t firmly decided which way to go for the ducting, but the list is getting short. The sightline looking into the rearview mirror passes about 1.5″ above the intercooler, so regardless how the ductwork routes, it’s going to block some portion of the view. The difference between the approaches is how much it blocks. It turns out that having inlets at the top corners of the main hoop are even worse because they’ll completely block the blind spots, arguably more important that the view directly behind. Of course it could be argued that that’s what side mirrors are for, which I don’t have. It’s a fair point; I just want to see how much visibility I can retain with some thought rather than chucking it all out the window right at the start of this. If side mirrors become a necessity, so be it.

A derivation of the above is having the inlets at the upper corners turn the air sharply inward, combining together above and just forward of the intercooler before turning downward. I’ll have to mock it up but already think it’s more work than just having the inlet above the windscreen.

Another suggestion was having scoops down low on the sides of the chassis; it’s what “real” mid-engine cars use, but due to Midlana resembling a Seven, there isn’t room between the engine and main roll hope for large ducts to pass through. Even if it could, then what? It would have to raise up out of the engine compartment to feed air into the intercooler from above. Of course, another approach would be feeding that same air into the bottom of the intercooler and assume there’s sufficiently low pressure above to allow it to flow out. Since there’s no room for ducting however, this approach can’t happen.

Lastly, there’s picking up air from under the car – again, there simply isn’t enough room for large ducts to pass air up past the engine.