Had the week off so between honey-dos and being on-call, the diffuser was built. As background, the vertical strakes were going to be aluminum, but later, because there’s a fair likelihood that at some point they’ll drag on the street, I switched to HDPE (high-density polyethylene) because I had it, and because it seemed like it would wear more gracefully, unlike aluminum that would bend and stay bent.
Having made the decision to go with “wearable” plastic, the vanes and end plates were initially going to extend lower, such that there’d be only 2.5″ of ground clearance. The idea was that they’d “self adjust”, but after thinking it over, that seemed like a recipe for disaster. Images of having the leading edge(s) catch on something and having the entire assembly pulled off the car didn’t seem impossible. For that reason they were trimmed back so they’re even with the bottom of the car. Anyway, on with the pictures.
There was an aspect of HPDE that I casually considered, that it’s rather heat sensitive. Since there’s a lot of air flowing past the exhaust where it exits into the left-most tunnel, how hot could the air really be? The answer is illustrated in the last picture – “hot enough” (and this was a casual drive, I imagine on-track I’d be dripping melted blobs… sigh – they’ll be replaced with aluminum.
I’m sure you’re wondering whether the diffuser works – good question. My imagination thinks so*, and I can offer that leaves fly up behind the car. But, sometimes leaves flew up behind the car before. My thinking is that it can only improve airflow and at track speeds, will very likely be doing its thing. Oh, and the rear wing will be placed above the trailing edge, which enhances diffuser flow even further. There’s simply no easy or safe way to test it out on the street.
* Of course, after I change the oil on a car, I swear it runs smoother, so there’s that…
Over on the Locost forum, someone built a diffuser using 1/8″ (3mm) ABS sheet, doubling it on the strakes. I’ve got some left-over black 1/4″ (6mm) HPDE sheet which might work well for the strakes due to being potential wear items. I’ll have to make templates and see if there’s enough material on-hand. Given how diffusers work, it’s tempting to extend the end plates lower than the floor, though that makes them the lowest point on the car…
Worked on two projects: the cold air intake and the diffuser.
Unlike how I normally do things – scratch-building everything – this time I wanted to see if I could find something “off the shelf” to serve as the air filter enclosure. After wandering around half a dozen stores, a stainless double-wall ice bucket (complete with woven bamboo weave) looked “promising”, mostly because nothing else in the kitchen sections was even close. Removed the bamboo, then used the “death wheel” to cut out the inner wall. It was pretty amazing how perfectly it fit the conical air filter – though I did test-fit it in the store. What still has to be added is a 5″-diameter extension to pick up the duct hose. At the other end, another fabricated duct will feed air to the hose from the side air inlet next to the dry sump tank. It’s either going to be composite due to the oddball shape, or a rather curvaceous aluminum assembly.
Diffuser: after reading that excellent article, given that the bottom of the car is flat from front to back, the diffuser might actually have a chance of doing something. It’s a 24 x 48″ (609 x 1218mm) aluminum panel, with a lot of mockup work. The forward edge will be captured by the aft edge of the engine tray. Right now I’m thinking of aluminum angle below to support the strakes (yes, that’s the term), and another piece across the rear edge to prevent bending and to (very optimistically) perhaps even act as a Gurney flap. That should make it rigid, but it’s still has to be supported, either off the side panels or via tubes or cables off the inboard chassis. Mostly because of the muffler, the diffuser angle ended up being 13 degrees. Yes, I know, everyone says the maximum divergent angle should be 7 degrees, but as the article notes, diffusers run at lower speeds and with larger ground clearance can handle bigger angles. In any event, something will close off the current open area around the exhaust, probably screen just like above, though the shape needs some thought to not totally mess up the appearance.
There is a bit of concern about the nearly 2-ft extension behind the rear axle. For example, going over speed bumps, not currently a problem, could become so at certain speeds, where as the rear of the car passes over and down, the suspension compresses somewhat below ride height as the shocks compress, so the speed bump could end up kissing the bottom of the strakes. I’m trying to plan for that possibility, so that the worst that happens is a bit of aluminum gets bent, rather than it hooking on the leading edge and ripping the entire assembly off the car!
The wings – not yet fabricated – will only be mounted for track events. I’m not impervious to what people think (partly because it can affect book sales) but also because I’d feel silly driving on public streets with them. While technically functional at all speeds, they’re realistically pointless at legal road speeds, so it’s sort of a lose/lose proposition. I mention this now because to a somewhat lessor extent, the same applies to the diffuser.
The diffuser will be a 24 x 48″ (610 x 1220mm) panel with the forward edge attaching to the rear-most cross tube. Due to the muffler, it’ll have a small angle toward the front, then a larger angle behind it.
This Racecar Engineering article and Willem Toet article were both very helpful (though the latter was obviously not proof-read!). Before reading the articles, I was going to leave out the strakes (the vertical vanes always seen on diffusers, but the figures graphically show why they’re a good idea. The articles were found while doing a Google search to answer whether a flat or curved diffuser works better. While neither article answers this directly, it appears that the sudden slope change at the front edge is necessary to initiate the spiral air currents drawn in from the sides. (On a related note, most forum discussions about diffusers are very inaccurate, go figure.)
Getting back to the question about street use, I’m sort of on the fence concerning the diffuser. Like the wings, even if it works, it’s of little to no practical benefit at legal speeds. Unlike the wings though, it’s not quite as “in-your-face”, being mounted down low. Also, there’s the practical issue of where to keep it when it’s not on the car. The wing assemblies will be tall and slender, and can be stored against a wall out of the way. Not so much with a large three-dimensional diffuser assembly. As of this writing I’m leaning toward leaving it on the car and putting up with the increased boy-racer look. That said, if I can drive down a leaf-covered street and kick them up high in the air behind me, that’s so totally worth it 🙂
Before anyone says “well what about the pretentious air intake on the roof?” Unlike the wings and diffuser, cooling the intake charge is of benefit whenever the engine’s in boost, which is often, so it stays.
I’ve had enough – don’t worry, it’s not about the car.
Visiting various websites, I’ve had enough of the increasing number of ads and the extremes to which some website owners will go to in order to increase ad revenue. Click-bate – and more and more regular sites – are turning into thinly-wrapped delivery systems for Google ads instead of actual content, which is being relegated to less and less screen space. What content is left has been calculated to be the bare minimum required to get people to click the next page. So to twist a saying, I’m putting my mouth where my money was and am removing Google Adworks from this site.
I know many people didn’t mind, but what they may not realize is that when webpages appear to hang while opening, it’s because Google gives priority to all the sidebar, header, footer, and embedded ads, ahead of the actual content. I don’t like them deciding that their revenue is more important than the content people came to see in the first place.
To be honest, Adworks never made much here, so I’m probably being a hypocrite; I probably wouldn’t be as righteous if it was making $10,000 a month. But it isn’t, and no longer feeling a bit like a prostitute is worth more than what their system was paying.
Cleaned the bottom and rear of the car, though it was impossible to get at all the oil. I didn’t want to use any sort of sprayer that drives water into the wiring or chassis tubes, so I’ll wait for the oil to absorb dust and fall off…
After that, it was time to install the new exhaust, this time with a Borla muffler, mostly because it’s stainless but also to test the claims of great muffling and low back-pressure. The exhaust is set up so that it disconnects downstream of the flex coupler with a V-band for track events, and a short right angle extension can be swapped in, much like how the exhaust was before today. Both wastegate outputs are also fed in upstream of the muffler – no point cruising quiet(er) but attracting the wrong type of attention while under boost.
The muffler works really well (Borla PN 40359), I’m pretty happy with it. The picture from the rear shows how it’s leaned forward, to miss the future diffuser. This leads into something I’m working on, to solve how Midlana’s been looking a bit “unkept.” One issue (in addition to the engine cover) is the chopped off lower rear panel (crunched when the car backed off-course at Willow Springs then cut off because it wasn’t repairable). The plan is to fabricate a one-piece engine tray/diffuser of aluminum or stainless. Whatever the material, the nearly 48″-wide sheet has to be thin/soft enough that it can be curved upward to form the diffuser. At the same time, I’d like it thick enough that it can serve as structure under the engine, something of a contradiction. A middle ground might be to have a shop roll the curve into it for me.
As mentioned before, the air filter’s being changed to pick up air from the side inlet instead of sucking in hot engine compartment air (now hotter because of the muffler below it). The ducting and different air filter element is on-hand; the new filter is better suited to being enclosed and fed via ducting. After finishing the muffler, the new filter was installed without the ducting just because, the large hose clamp tightened, and I headed out for another test drive.
During the drive on my newest favorite road, I saw two Alfa Romeos GTVs (my favorite model) pulled off to the side, the owners chatting. Further on were another 3 or 4 more, one with its hood up. I stopped and asked if they needed any tools. They laughed and said “we drive Alfas, of course we have tools!” We chatted some about Midlana and then I was on my way – thankfully not trailing a stream of oil like last week!
With the muffler working so well, new sounds are detectable now, and unfortunately, one sounds like engine knock under full boost. What’s unclear is whether it’s always been there and I couldn’t hear it, or if the (assumed) added back pressure from the muffler caused it. I’ll log a drive to see what’s going on; maybe it’s just something that sounds like knock. If it’s the real deal though, boost will be dialed back a bit :).
Stopped for gas on the way home and half way through filling the tank, I saw something move out of the corner of my eye – the air filter had just fallen off the turbocharger, hah. How it managed to stay on the vibrating engine through the entire drive and only fall off right then, I don’t know, but I was happy to see it happen. The hose clamp worm screw housing had contacted the compressor housing, giving a false indication of being tight – fixed.
No oil leaks on the test drive, though there’s still oil from the original leak coming out of the woodwork. What didn’t help the oil leak situation was the engine tray being off the car. Not only did this allow the oil to be blown aft, but the open rivet holes allowed some of it into the chassis tubes, only to later drip out when it feels like it.
Lastly, alternator output remains at 14..0-14.5V during the entire drive, so no issues there.
Oh, ran across this pretty cool looking (and free!) PC application for designing mechanical linkages. I haven’t used it yet but it could be useful for future projects :).
Did another long back country drive, finding new and wonderfully twisty roads off the beaten path. Even on a Sunday, when motorhomes and pickup trucks with dirt bikes clog the roads heading back from the desert, there are still a few roads to be explored. About half way through this drive, the little voice in my head asked, “Do you smell something?” Me: no.
A bit later, “Are you sure, it smells like oil.” Me: Yeah, but it’s really faint and probably isn’t even coming from my car. It could be a truck and I don’t see any smoke. As I neared home, however, the oil smell had become unmistakable.
Pulled into the garage and the line of oil down the street delivered the message in no uncertain terms that something was up. The bottom and back of the drivetrain, and all the suspension and the rear of the car were covered in oil, so the immediate goal was finding the source.
Started it up and there it was, coming from around the oil-to-coolant heat exchanger. After cleaning up the mess to get under the car without taking an oil shower, a closer look found it was coming from the inlet fitting on the oil cooler. The -12 AN fitting wasn’t loose; it was the bolt-on adaptor it was screwed onto that was leaking. Oddly, the Torx screws were tight, so it seemed like the gasket must have given way after, what, five years?
After removing the fitting, it turned out that it’s sealed with an O-ring and it seemed like it had gotten pinched – or so I thought. It wasn’t until I pulled it out of the groove that I found there were two O-rings! The only thing I can think of – given that there’s only room for one O-ring – is that the assembler must have reached into a bag of O-rings and not noticed that two were stuck together. Amazing that they remained sealed for as long as they did.
I’m going to call the seller to see if they’ll give me a free replacement gasket set if I casually mention that the only reason I didn’t trash this engine was the 8 quarts of oil in the dry sump system. When the tank was drained before removing the fitting, it was a bit shocking to see that only about two quarts of oil were left. I think the leak started very gradually which is why it didn’t become suddenly obvious. Seeing the solid line of oil down the street, I doubt it would have lasted another 20 minutes. Yes, the ECU should catch the low oil pressure with a rev-limiter and a warning message, but I don’t want to test that. Close call though.
While looking at the broken exhaust, the brace from the engine block that supports the turbocharger was found broken as well. I think I know when this happened. I was leaving a driveway and accelerated hard and may have caused a “PIO” (Pilot Induced Oscillation) with my foot inadvertently getting on and off the gas due to the car accelerating and decelerating so hard. The result was a violent back and forth action similar to ignition cut. I say I may have because the ECU failed to log it (again). Anyway, the turbo support bracket was repaired – though I noted that some bonehead had left it tack-welded, no surprise it failed.
As a temporary fix, the failed stainless bellows was welded back together instead of being replaced. That’s because even before this happened, there’s been a plan afoot to adding a muffler (again). The intent is to both reduce noise and unwanted attention, and to just be more pleasant. Besides, the car has so much power that if I lose 10 hp by adding it, so what. It’ll be installed so that it takes about a minute to remove for track event.The downside is more weight and heat, which will likely lead to something else that been on the back burner, a cold air duct running from the side vent to an enclosed air filter. As it is now, the open air filter sucks hot air in straight from the engine compartment, decreasing power and increasing the chance of preignition. Adding the duct may well make back whatever power the muffler takes.
In other news, a bit more information was found regarding CS-130D alternators. Apparently they contain a temperature sensor, though it’s unclear what for. It might be to reduce output to protect the alternator as it warms up, or maybe it’s to maintain output instead of it dropping off with temperature – I suspect the former.
Also alternator related, it was noticed that at idle, the alternator vibrates some. Suspecting something was broken, it was disassembled again but nothing was found, so the mount may simply be flexing. Might have to make a new one using thicker material, or double up the material that’s there now. It was reassembled with a new bolt and after putting it all back together, turning the alternator pulley now turns the engine (apparently it had to wear in) so belt tension’s off the list of suspects.
Right now I suspect it’s just how these alternators work, varying the output with temperature. An experiment would be to warm up the alternator with a drive, then while idling, cool it with compressed air to see if the output voltage jumps back up. My brother reminded me of something I intended to do, measure battery voltage with a good DVM instead of taking the dash/ECU’s reading as fact. Good idea, because the dash reads about 0.2V low, further lessening my drive to fiddle with this issue much longer.
Received the replacement coolant temperature sensor and finally checked its calibration… well, let me back up.
An authentic Honda coolant temperature sensor is roughly $45 online, and me being a cheapskate, looked for alternatives. Found one on Ebay for about $8, with the picture showing the sensor next to an authentic Honda part bag with the correct number on it. I knew better than to think it was actually what the picture portrayed and bought it anyway. Sure enough it arrived in a plain box with no markings whatsoever, so no surprise it’s a knockoff.
Boiling water in a Thermos was placed in the engine compartment where the wire harness could reach. The new sensor was plugged in, and it and an accurate mercury thermometer were submerged in the hot water. The sensors were allowed to settle for several minutes and then the temperature read; the thermometer settled out at 91C, while the sensor read 77C. Sigh, it wasn’t expected to read exactly right but this is kind of ridiculous. To be fair, I don’t know how accurate an authentic Honda part is, but doubt it’s that bad. We’ll see since a “real” sensor has been ordered.
Took Midlana and the granddaughter to the new Cars and Coffee location, currently at the Outlet San Clemente mall (one can only wonder how long it’ll be before they get thrown out from there as well, which seems to be the fate of the event, for noise, exhibition of speed, etc). This was the first time she’d been to any car show and, it went about as expected, not much interest, but the point was to expose her to it at least once so she knows they exist and what it’s about. I told her that I’d be happy to take her again but she has to ask – I won’t pester her to go.
No good deed goes unpunished and the traffic for the 50-mile trip home was brutal. The clutch was used about a million times because even at idle in first, Midlana wanted to move along faster than traffic. Being around 28 C didn’t help but it was a good test of the updated cooling system; coolant got up to around 90C but no higher. On the way up it was the exact opposite temperature-wise, dipping as low as 6C, brrrr. With such low temperatures, engine coolant only got up to about 80C.
Speaking of that, I’ve been watching how alternator voltage varies with temperature. In cold weather, charging voltage is 14.1V, perfect, and turning on the radiator fan caused it to drop to about 13.5V, still pretty good. On the way home in the heat though, charging voltage slowly dropped off to around 13.6V and dropped to 12.9V with the fan on. I was going to check to see whether the Chevy pickup alternator I’m using has an “S” input (Remote Sense). As I type this though, I just realized it doesn’t matter if it does or not. If there was a voltage drop problem at higher air temperature, it would still be there in cooler weather, but the problem is only during warm weather, ruling that out. It’s not like the alternator is being overheated either; right now there’s neither an engine cover nor belly pan. Also, since this is a cross-flow engine with the alternator on the intake side, it’s not near anything hot. I suspect the built-in alternator regulator just isn’t very good over temperature.
I could try running a cold air hose from the side vent to the alternator, but related to the above, since it’s already fairly well ventilated, there’s a good chance that the “cool air” being fed to it through a hose from the outside isn’t much lower than the air already swirling around the engine compartment. Of course, zooming way out on the problem, I’m not sure how much it matters. That is, it’s been this way for years and hasn’t been an issue, though I do keep a battery tender on it when in the garage. Then, during the endless traffic jam yesterday, I managed to stall it once and forgot the radiator fan was still on; when cranking, the battery clearly wasn’t happy at all about having to run both (sounding like a run-down battery). So there’s several approaches: do nothing, get the aftermarket alternator and hope it’s less temperature sensitive, or set up a cooling air duct for the existing unit and hope the outside air is a lot cooler than engine compartment air.
Finished the radiator ducting, though it still needs paint before being permanently mounted. It was assembled with temporary rivets and Midlana was taken out for a drive, again confirming a 2-3 degree C decrease in coolant temperature under all conditions.
Twice now the same cylinder head exhaust manifold bolt has backed out, the first time completely and the second time about a centimeter. Not sure why since it’s torqued to Remflex’s recommended 20 ft-lbs. It was okay after today’s drive but if it does it again it’ll be safety-wired.
Went on a longer test drive into the back country, up “my” Palomar Mountain “test track”. This time there was an interesting mix of events.
At the base of Palomar Mountain, they were fishing a balled-up sportbike out of a ditch, the driver nowhere around. Heading up the mountain I got stuck behind a cruiser Harley where the rider was apparently still learning to ride. That’s fine, except he was going between 22 and 32 mph, I checked. At first I was polite – everyone starts somewhere – but after a while it got kind of annoying as he kept passing places he could have pulled over. And then…
After ruining about 80% of my ride up, a Harley was coming down the hill the opposite direction and correctly assessed my situation in a flash. It was quietly hysterical what he did, first tapping his helmet and then giving a palm-up gesture toward the Harley, like, “dude, how long you been holding him up?” I don’t know if the Harley ahead of me finally noticed me, or if the guilt worked, but he immediately pulled over. I had a very hard time to not laugh as I gave him a thank-you wave.
After I passed the Harley I went tearing up the rest of the hill, trying to make the best of my shortened “course.” The new tires are, well, amazing. The old ones had really lost their stick because these new ones are pretty incredible. I haven’t even managed to slide the car yet because doing so means going into a turn fast enough that if it does become unstuck, I’d likely end up in the ditch along with the sportbikes. Speaking of that, came around a turn and there was a second sportbike being retrieved from the rocks. Not far away, a cop was making an accident report but heard me coming and had a good long look at me as I came by… I waved to acknowledge, “yes, I know you see me and are thinking ‘how can that be legal’, and that I’m cutting it close.” Thankfully all I got was the look.
All the way up, coolant temperature stayed lower than it had on previous drives – I’m happy. Drove around the top of the mountain a bit then headed back down. This time I had a Harley behind me who wanted to play. I let him pass and once past the cop, we had some fun heading down the hill. I’m curious how I would have done behind a real sportbike, but that puts us both in a situation where things get serious. I previously wrote that I always wanted a car that could keep up with sportbikes heading up the hill and I may well have that. The thing is, there’s a small chance that one or both of us might go off (as said above, two bikes already had). If he went off with me right behind him, I’d stop, and then things could get really interesting, like, would he sue me because I was pressuring him, him hoping to avoid his share of responsibility?* Would the cops arrest us for street racing? Serious thoughts – or maybe I’m just old. I passed a group of sportbikers at the base of the mountain, apparently grouping for another “assault”, and sure enough, they got all excided when they saw Midlana. I waved, but decided that stopping and getting involved might not be wise.
Oh, I got my very first thumb’s-up from a Harley rider, the first out of the 500 or so I’ve passed over the years. Meanwhile, sportbike riders give enthusiastic thumbs-ups about 30% of the time – I have theories.
On the way back, passed the local university and a car pulled up alongside with several hot and crazy college girls, screaming how “sick” my car is. Ah, if I were but young and single…
During the weekend’s drives, the alternator may or may not have been acting up. It normally stays mid-13Vs, which is a little low and is why I’m considering an aftermarket adjustable unit. It’s as if my alternator heard my thoughts because now it’s charging at around 14V, which it’s never done before. Also different is that with the radiator fan on, a few times at least, voltage sagged down into the 12.XV range, which was new. Checked for loose wires and found nothing.
No bites on the transmission, but at $4000, it’s not surprising that it may take a while. The price is what it is because of the work done to ensure it’s as close to “new” as something used can be, so for now I wait. We’ll see if and when my idea of its worth matches anyone else’s!
I have all the parts to start building the rear wing, and at some point I also have to figure out airflow in the proposed location (how high it needs to mount to be in clean air). There are various ideas, one involving smoke bombs… that could be interesting…
Lastly, I tried fixing something that’s low on the annoyance scale but there nonetheless – the perpetually-crocked steering wheel. It’s because the splines on the steering wheel adaptor are fairly course, so it’s either wrong in this direction or that direction, take your pick. I finally realized that the Miata splines further down the steering column are more fine-pitch, probably around double, so I tried offsetting it by one spline, and it’s much better now.
*There’s currently a lawsuit between a sportbike rider and Laguna Seca Raceway. He had gone off-course and hit some sandbags, which threw him off. He’s claiming that Laguna unnecessarily made the track dangerous and caused him to lose control. Well, what was he doing off course if he hadn’t already lost control, but anyway, people sue for all sorts of reasons.
Went to the local hot rod show with my brother. He wanted to talk to Tremec, his transmission builder, about how the front of his case has cracked, something that’s reportedly happened to other people as well, but wasn’t much satisfied with their answers, which were a little wishy-washy. I told him the right ($$$$) solution is to suck it up and buy their next model up in strength, else the probably may well happen again. The first picture with my hand on the gears is one of their upper models. Yeah, those gears look like they could handle some pretty good torque.
The rusty white truck had a turbo about twice as large as mine, with an air cleaner about 8 times smaller than mine – yeah, it shows signs of collapse.
The yellow and red show car looks like something the Simpson’s or a few Minions should be driving.
The green truck had a complete 425 (or 455) c.i. Oldsmobile Toronado in the truck bed. The picture from the side shows just how compact the drivetrain is, with the engine sitting directly over axle centerline. Compact yes, light, nope.
That tire? A “405/25-24”. I fear tires are still heading up in size.
The engine with the bluish valve covers isn’t anything remarkable, but the fuel and nitrous plumbing was “noticeable.”
There were a few rat rods, and then there was what appeared to be a very old stock vehicle, but it turned out he’d created it from authentic odds and ends from that era, including a V12 out of something. Another car had a V12 in it as well; the header fabrication would have been a fun project.
The light blue/silver car was amazing, kit or otherwise, as was the period correct engine in another car.
And then we come to our favorite, the ratty-looking pale green Chevy truck. We’d have walked right by it had we not just seen it at the autocross. Watching it approach the first turn we both said out loud “he’s never going to make that”, and then did. The thing was flat-out amazing, beating about 90% of everything else. The secret is its Corvette chassis, suspension, and drivetrain, but you couldn’t tell from the outside, though the huge brakes are a hint. The interior looks much like an old 1960’s truck, albeit with racing seats. He’s looking forward to taking it to a trackday, and it would be pretty funny seeing him pass “real sports cars.”
Went for a couple test drives to get more comfortable with the new transmission and the close ratios. Something else though, came to light during the drives that consumed my attention.
Ever since the engine was retuned I noticed that coolant temperature seemed a little higher. It wasn’t a lot though and since coolant temperature is affected somewhat by outside air temperature, it was never really clear if it really was or not.
As mentioned before, Midlana has always had this somewhat odd trait where when idling with the fan on, coolant temperature is fine (mid-80s, C of course), and when on-track and driving hard, coolant temperature is about the same. But then there’s just plodding along on the freeway at 65-75 mph. One would think in that low-power situation, coolant temperature should again be about the same, only it isn’t. Given enough time, the temperature very slowly creeps its way up to around 90C, and this weekend on the freeway while going up a long incline, it hit a new record of 93C. If it was the middle of summer it wouldn’t have been as big a deal, but outside air temperature was only 17C.
There’s about a dozen things that could be going on, and in no particular order: radiator too small, weak electric water pump (or plumbed backwards(!), mechanical water pump turning the wrong way(!), defective coolant temperature sensor, air going around the radiator, big air bubble in the cooling system somewhere, engine timing, a collapsing hose or obstruction, low coolant, or maybe something I’m missing.
First, a back story regarding pumps, which involves Kimini, predecessor to Midlana. Kimini’s new owner added an electric water pump to help move coolant from the mid-mounted engine to the radiator and back. It apparently worked well enough that he stopped paying attention to coolant temperature, because soon after, the engine was destroyed due to severe overheating. Turns out that he’d wired/plumbed the pump so it was moving coolant the opposite direction as the engine’s mechanical pump! This caused very interesting symptoms – had he noticed. At idle, the electric pump probably won the tug of war regarding flow direction, so it stayed cool. At freeways speed, the mechanical pump, now spinning fastest, probably won the fight, moving coolant the opposite direction. But consider the case of driving at some magic lower speed where the flow generated by the mechanical and electric water pump perfectly balances. At that speed, coolant flow through the engine is zero – end of story, and end of engine.
As a sanity check, both pumps were checked for proper rotation; the mechanical pump because I’d rerouted the belt, and the electric pump, just because. Both were fine, so they’re off the list.
To keep from wastefully replacing stuff, the car was warmed up to an indicated 80C, then the radiator cap on the header tank removed and the temperature measured with an accurate mercury thermometer, which read about 68C. At first it seemed like “ah hah”, but probably not because the header tank is filled by two bleeder hoses, a small one from the cylinder head, and a larger one from the top of the radiator. It’s likely that the header tank will always be somewhat cooler than the coolant measured by the sensor itself inside the cylinder head. That said, I’m going to buy a new coolant sender anyway, plug it into the harness outside the cylinder head, and put it and the thermometer in a heated container of water. The reason is because an inaccurate calibration of one of the ECU manufacturer’s default Honda sensors has already been identified. I’ve never tested the coolant sensor so this would be a good reality check.
Another reason the header temperature might be inaccurate is because coolant flowing from the engine to the radiator flows first through an oil-to-coolant heat exchanger, which can add or subtract heat depending upon oil temperature.
Because of the bleed lines, I don’t believe it’s possible for a big air bubble to be trapped in the cooling system; it’s self-purging by design so that’s off the list. The radiator being too small doesn’t fit either, since it works fine under hard use at the track. Coolant level is fine; I don’t think (without proof) that there’s any obstructions because I only use distilled water and Water-Wetter. That leaves air going around the radiator… hmm.
As a quick test, rags were stuffed around the radiator where I could reach and another test drive performed. Well huh – taking the very same route, at the same speeds, and in the same weather, coolant temperature struggled to reach 90C, and when I let off, it dropped faster than before. This leads to the theory that at idle with the fan on, air gets sucked through the radiator by the fan, so the gaps around the sides don’t matter. At speed on-track, there’s so much air coming in that even with the leaks, there’s sufficient air flowing through the core that cooling is sufficient. That leaves the freeway situation. Here, there’s less air coming in the nose and maybe half (a big guess) is going around rather that through the radiator and providing insufficient cooling. It’s just a theory but seems to fit the facts. So first thing was to cut off the support for the horn (it sticks around the side of the radiator and makes sealing it in that area impossible). The horn will be relocated behind the radiator. Paper templates are being made for aluminum panels to extend from the inside of the nose cone to the forward face of the radiator, with foam between the two. This is so when lifting the front cover, the panels sealing the radiator will move away from it without snagging on anything.
So things look promising, though it’s something I should have done back when the car was built. Of course back then there was a big push to get it on the road, so some things got pushed off.
Oh, and there’s one other variable – ignition timing. From my understanding, timing really affects how much heat gets pushed into the cooling system. The tuner noted that he advanced timing quite a bit, so it may well be that that’s the source of the higher coolant temperatures.
Lastly, I’ve been trying to find what the normal coolant operating temperature is for a Honda K24, something that’s surprisingly vague and variable. It seems to be somewhere between 80-95C, so it’s not like the engine is overheating. This motivation to get to the bottom of this came from seeing temperatures it had never reached before, so adding the radiator ducting is the right thing to do, regardless.
Looks like the lower most layer or two need stiffening up, which is now easy enough to do.
I enabled the HDR-AS300’s GPS overlay and while it’s interesting, it may prove to be something of a novelty since GPS speed lags so far behind (how does my dash keep up with the same data?). The route information is interesting, but again, not sure how useful it’ll prove to be.
Forgot to mention yesterday that the transmission shifts so easily, I twice shifted into the wrong gear. Doing so while just cruising (like I was) isn’t a big deal, but having that happen on-track is a different story. Going to have to get better accustomed to the new gears, syncros, and shifting effort.
Lastly, my dog-box transmission is being boxed up and shipped home. Once it’s here it’ll officially be for sale.
Spent the weekend building the new rear engine mount, which took way longer than expected. Part of this is my own doing though, because with Kimini, I planned everything out to an extreme and as a result, fabrication went smoothly and very little had to be redone. With parts of Midlana though, I’ve been testing how much I can “wing it” and still have it turn out right – this one just made it.
The plan was to have the engine mount rubber “field-tunable”. The OEM mount works fine in an OEM application – but not so much with 400+ ft-lbs of torque. Also, applying torque to the side of a bolt in a rubber-filled tube just doesn’t work well when a lot of force is applied because it’s so concentrated. That’s why a 2″ x 4″ steel “foot” is used to spread out the load and rests between layers of polyurethane sheet. Being a rear engine mount on a clockwise-spinning engine means that the layers below handle acceleration torque and the layers above handle deceleration. This allows using different durometer rubber for each layer. So the prototype was built but the unknown was how much it would deflect under power and deceleration – and how much vibration would be transferred to the chassis.
“If only I was able to watch it.” Presto, that’s what the new Sony camcorder is for, so it was attached to a rear tube and aimed at the engine mount. About now you’re probably looking for the link – well, there isn’t one yet. It’s late, the camera’s new, and I have to figure out its editor. Hopefully it’ll be good enough else I’ll have to find a “real” video editor. I watched the raw video and it’s pretty cool what you can see and hear – I’ll post it up sometime this week.
In other news – the clutch! With the new transmission having synchros instead of dog engagement, I again used Competition Clutch’s instructions to set the clutch stop for the twin-disc clutch. With the dog-box, I couldn’t set it as instructed because it would instantly drop into gear even without the clutch. The instructions say to gently push the gear lever like you’re going into a gear, while at the same time slowly depressing the clutch. At some point it’ll drop in, then push the pedal another 1/4″ and set the clutch stop there. Well, I did, and holy smokes does it change the character of the car. Clutch throw is now much shorter and with the close gear ratios, it makes shifting much faster. I’m really happy how that turned out.
Every now and then I get caught up in the excitement of buying stuff for the car but getting too far ahead of what’s needed right now, such as wanting to pick up aluminum stock for the wing while the rear engine mount isn’t complete. I learned the hard way that if I have parts on-hand for half a dozen project, I actually make slower headway than if I just focus on one at a time.
Somewhat related, before the wings are built, air flow over the car needs to be researched, and the new Sony camcorder should help that happen.
Then there’s the higher-output alternator which was almost ordered, but again, first things first. Even when it does percolate to the top of the list, it needs to be seen if just running cool air to it might be enough.
Just remembered another task – radiator ducting. The car never overheats, but when cruising at freeway speed, coolant temperature gets higher than when driving hard on the track – why is that? The theory is that some (or even a lot) of the air coming in the nose goes around the radiator instead of through it. At freeway speed, there may be insufficient flow through the fins to carry away all the heat, but at high speed, even with much of it going around, there’s still plenty left over for actual cooling. Will probably tape up some cardboard and see if the theory’s correct.
Weather cleared up so an 80-mile drive broke in the new gears/synchros/LSD. Observations:
The ratios are noticeable closer, which isn’t a surprise but I kept catching myself pausing between gears, waiting to match gear speeds, a habit learned with the straight-cut gears, but when I let the clutch out with the new gear set, it’s clear I’m waiting too long. That’ll solve itself with time.
During the drive, 80 mph (GPS) was 4000 rpm, so back-calculating, the rolling diameter of the tires at speed is 25.1 inches (they compress about 0.5″ due to running ~15psi). That rpm is a bit high for cruising and will ironically serve to keep me more in line, read: driving slower on the freeway. Another reason to slow a bit is because boost is right there and ready to go by 4000 rpm, so it’s like riding a thoroughbred racehorse at a trot but who is ready to go right now. A third reason is that when in boost, fuel mileage takes a nosedive. That said, though the rpm is where MAP can reach maximum, since the throttle’s mostly closed, it’s only about 60 KPa (40 KPa below ambient). I read somewhere that a turbocharged engine can actually improve gas mileage somewhat by overcoming the pumping inefficiencies inherent in gasoline engines due to the throttle plate obstruction. Obviously not a big goal.
(Because of the rolling diameter of the rear tires, if I absolutely must reach 60mph in first gear, I either have to increase the rev limit to 8150 or put enough air in the rear tires to increase the OD to 25.6″, hah.)
After the drive, the OEM transmission fluid used for break-in was drained and replaced by magic oil supplied by the gear manufacture in unmarked bottles. Went for a short drive for gas and it “seems” to shift a bit easier, though it could also be my imagination. I assume it’s going to take several hundred miles for the carbon synchros to wear-in. Speaking of oil, I had an issue with the old transmission where the gear manufacturer, PPG, recommended brand X, while WaveTrac specifically recommended not using brand X. With the new transmission it’s similar, with Gear-X recommending their stuff (of course) and Giken recommending their stuff (of course) which, of course, wasn’t the same. I ended up getting both of them to hash it out on a group email and Giken finally said that Gear-X’s mystery oil would be fine.
There hasn’t been a peep out of the limited slip, or maybe I can’t hear it. Some people complain that Gikens makes noise, though others say it’s silent. Doesn’t matter either way, just a note.
If there was any question before, the test drive confirmed for sure that the engine mount has to be redone – way too much vibration.
During the test drive, logger data was used to recalibrate the ECU’s calculated “gear”. The transmission doesn’t produce gear position directly but the ECU has the variables to create one. It’s handy for various things, such as boost-by-gear. Speaking of that, boost in 5th and 6th was increased (back) to the maximum value – that’ll be fun. Assuming it’s clear this weekend I’ll do a longer drive to fully break in the gears, then change the transmission oil as requested by the gear manufacturer.
I reworked the rear engine mount (which resists torque) while the engine was out but don’t like the result, too much vibration. I have a plan to basically roll my own and I’ll post pictures. The sweet thing is that the new design will make it easy to change the stiffness on the fly.
There’s the wings to make, which is a significant project but since it’s fairly compartmentalized, the car can continue to be driven while that’s underway.
There’s the rear diffuser, and right after that, filling in the gap above it, created when the damaged panel was cut out after my off at Willow Springs. Will probably use screen mesh for that.
Engine cover: Been wanting to redo it for awhile because without it, the car looks unfinished. More concerning though is the small worry about an engine fire at-speed, there’s a strong likelihood that the flames will be swept forward by the swirling air. That would be bad.
Upgrading the alternator. If I’m driving at night in stop-and-go traffic, the lights, electric water pump, radiator fan, fuel pump, and of course the ECU are all on, which is around 80 amps. I’m considering adding a small oil pump and cooler to the transmission (already have both) which moves the total current closer to potentially 90 amps at idle. The OEM Chevy pickup alternator produces around 14V when I first start the car, which is fine, but as it warms up it drops off. On the freeway with just the essentials (water pump and fuel pump), battery voltage ends up around 13.5V, and around 13V at idle when fully warm, lower than I’d like. I’d like to be able to run everything instead of having to sometimes load-shed things as the battery voltage drops off.
There are a couple solutions, like feeding cooling air to the alternator and putting on a slightly smaller-diameter pulley, though it’s being spun about as fast as it should be (18,000 alternator rpm at 8000 engine rpm). I’m currently leaning instead toward a unit that can support everything even at idle, such as the PowerMaster 478618. Better yet, it has remote sense and adjustable output voltage .
Long ago I bought LED signal flashers because the old-school mechanical ones don’t work with LEDs. Until recently, LED car lights weren’t a “thing”, so it’s random chance how the mechanical flasher sockets are wired (since polarity didn’t matter). Of course mine are backwards backwards (both the turn and emergency flasher) so the new LED-compatible flashers don’t work. I’ll have to pull out the fuse block and swap the pins.
Other things on the back burner are adding a transparent bulkhead window behind the seat to see what that does for possibly reducing wind and noise. Then there’s door fabrication. Pretty sure how I want to do them; it just endless details like: material, frame substructure, hinge type, fabrication, and placement, weather stripping, and a latch.
Lastly, I finally had enough of the buggy GoPro and have ordered a Sony action cam.