20 Feb 2018

Synchrotech Transmissions provided pictures of the transmission build. I’m familiar with the insides of engines but transmissions have always been a little mysterious; I would have liked to have been there but the pictures are almost as good at showing what’s involved. Dealing with Synchrotech went smoothly; once they received the parts, the build and delivery happening promptly, can’t ask for more than that.

As part of the transmission change was the thought of also changing the twin-disc clutch; could a replacement be found with lighter foot pressure and possibly quieter (twin-disc clutches have a characteristic rattle when in neutral). The twin-disc also has a feature that for a race car is a non-issue, but for the street is a little annoying; there’s always some slight coupling between the input and output even with the clutch fully disengaged – meaning the gears are still spinning slightly. Shifting into gear from neutral, it can always be felt that the gears are moving, so it has to be done deliberately.

I contacted Competition Clutch, maker of the clutch, and explained the situation. They said that one of their “Stage 4” clutches would do well, even after I explained the 430 ft-lbs of torque, chewing-gum-soft tires, and being mid-engine, traction increases under power rather than decreasing like a FWD. They also said that pedal pressure would be about the same – not sure how I expected it to be less. Part way through the discussion though, I realized that swapping in any other clutch meant also changing the flywheel, since it’s unique to the twin-disc. Separately from that was the realization that because I’m switching back to a synchro transmission, it’s highly likely that any slight gear rotation in neutral will be dealt with by the synchros and no longer be noticed.

I was a little skeptical how a single disc clutch could hold the same torque as a twin-disc, so to get a second opinion, K Series Parts (formally Club RSX) was called. The surprising advice was “stick with what you have, it’s the right solution.” They said that the engine’s torque is too much for any streetable single-disc clutch and it either won’t last or will be a real bear to operate (high pedal pressure). It really impresses me when a business gives an answer that prevents a sale – that right there demonstrates that they’re  more interested in the right solution. They weren’t left empty-handed though, as I bought the Gear-X gear set through them.

Lastly, with yet another engine pull looming, I wondered if there was any way to drop the engine out the bottom rather than pulling it out the top. Looked at the engine bay today and was surprised to see nothing preventing it – other than the cross-bracing of course. It would have to be cut out and then either be converted to a bolt-in assembly, or welding back in after the fact.

18 Feb 2018

In a couple weeks, the Honda K-series “DC5” transmission in Midlana will be up for sale. The specs:

Straight-cut dog-engagement 1-4 PPG gear set, rated for 1000 hp:
1 – 2.615
2 – 1.611
3 – 1.15
4 – 0.909

5th and 6th stock helical Honda (even though it’s a DC5, 6th was adding for freeway cruising:
5 – 0.825
6 – 0.659

NOTE: Because 5th and 6th are present, this transmission does not contain the PPG “center brace attachment”.

Final drive: stock Honda 4.389

WaveTrac LSD.

Full disclosure, the WaveTrac LSD is apparently one of their early units that has a known issue where it wasn’t machined correctly and traps the driver’s side CV housing in place – mine’s stuck good. The good news is that WaveTrac offers free repairs and the transmission will be delivered to them to be corrected before being sold. It’s a win-win because the buyer gets a known-good LSD, their axle won’t get stuck, and I get my CV housing back. That last part matters because the axle shop wants $250 just for that part…

The transmission works perfectly. As for price, it was $7000 to build and given that it only has 5000 miles on it, it’s worth $4000. If it doesn’t sell via this site, the Midlana forum, or K20.org, it’ll head to Ebay.

Because of the cost, I made a demo video, just some casual driving showing that the transmission is operating perfectly and it also demonstrates what a straight-cut dog-engagement gearbox is like. There would have been more video but the bug-ridden GoPro struck again, stopping the video mid-drive. Oddly, the red light continued blinking, indicating that it was recording, and when turned off, acted normally. I’m This Close to switching to the Sony like my brother has…

17 Feb 2018

With the finished transmission on the way, it’s looking like it’ll go into the car at the end of the month during a marathon garage session. While I’m doing that I’ll also be figuring out how to attach the rear wing assembly. On the Midlana forum I received a good tip about making the mount hinge so that the assembly can be rotated down out of the way for engine access. Thanks, Bill!

10 Feb 2018

Back when the oil and smoke incident occurred during the dyno tuning session, the theory at the time was that maybe the turbo oil return line got sucked flat by the dry sump scavenge pumps. My buddy Dave asked what crankcase pressure was; how did I know that it wasn’t just the opposite, that under heavy boost, maybe blow-by (past the rings) was pressurizing the crankcase to a positive pressure and actually pushed oil back up the return line? I said that can’t happen because it’s a dry sump; the crankcase is always at a vacuum. He countered with, “do you know that for sure; have you measured it, or are you just guessing?” Ugh, he was right, it’s bad science to just decide something without knowing for sure, and even worse to make decisions based upon it.

A test setup was assembled consisting of a 200kpa (+/-15) psi gauge, hose, and valve cover adaptor. I prefer kpa because it’s clear what vacuum is – 0, and ambient is 101. With English units, “zero” can be confusing because it depends upon context; it can either be ambient pressure or a perfect vacuum.  Ironically, the gauge manufacturer scaled the meter wrong; there’s no such thing as negative kpa, zero is zero, a perfect vacuum.

Warmed up the car and crankcase pressure settled out at 55 kpa (-13 in. Hg). The picture below was a couple minutes after starting it and before oil and coolant came up to temperature. Took it out for a test drive and during cruise, crankcase pressure fell (meaning vacuum increased) to about 40 kpa (-18 in. Hg). Found a deserted stretches of road, cranked up the boost to 15 psi and did a few 4th gear pulls*. Vacuum dropped to 55 kpa (-13 in. Hg), the same as at idle. This was a relief because that’s what’s supposed to happen; the dry sump pump maintaining a negative pressure even when producing maximum power. So for now at least, the collapsed turbo oil return hose still seems the most likely cause of the engine spitting out all the smoke and oil. Being immersed in hot oil for extended periods of time under vacuum very likely softened the rubber hose enough to allow atmospheric pressure to squash it flat. Once that happened, the oil couldn’t leave the turbocharger and filled up the center section and pushed past the seals into the inlet and exhaust sides. The anomaly hasn’t happened since, but than again it hadn’t happened before, and the rubber hose was since replaced with a Teflon part.

After the test and after shutting off the ignition, it took about 30 seconds for crankcase pressure to slowly rise back to ambient pressure – sort of a poor man’s leak-down test and a reassuring sign that there aren’t any major crankcase leaks.

*Ever since the retune, the car is a serious handful at full boost. Even a very slight bump in the road causes some wheel spin at even triple digit speeds. It’s one reason why there’s a knob on the dash for boost and it’s normally kept turned down to keep both me and the car out of trouble. That said, flooring it in fourth on the freeway at full boost is – frankly – effing awesome, as it’s as if everyone else put their brakes on 🙂

8 Feb 2018

All the transmission parts are on the way to the builder, who’s also sourcing the core. This avoids the concern about shipping him a used tranny of unknown history,  bought from a stranger from out of state, and having the builder possibly say, “this core is trash.” After checking what used transmissions go for and what the shop’s charging, their price is very fair so we both benefit.

Regarding the LSD, I found some good information in an unexpected place, Porsche 911 forums. 911s have an higher rear weight bias than Midlana, and being Porsches, many owners track their cars, so the topic of limited slip differentials often comes up (“what’s ‘best’ “) . There are many brands that fit 911s and the Giken holds its own. It was informative to read how the Giken helps stabilize the tail-heavy 911 under braking, during partial mid-turn throttle, and during full-throttle corner exit, all things I’m interested in. Of course, the Internet being what it is, you have to stand back to get an overall view of impressions instead of fixating on only desired posts.

Another good tidbit was that you shouldn’t install just any LSD into a mid- or rear-engine car because the chassis dynamics are different from front engine cars, be they FWD or RWD. Because of the differences, a proper clutch-type LSD for a mid-engine car is a “reverse 1.5-way”, and you can tell from the name that it works opposite what a front-engine configuration needs. Very glad I found that out before having it installed! As an aside, I also found that OS Giken is owned by Toyota, which seems like a good thing.

Speaking of 911s, I found this post which I can relate to:

“One of the things I had to force myself to accept when I first was learning to race [rear-engine Porsches] was that “more throttle equals more rear grip”. It was very counter-intuitive.

Luckily I was driving my instructor’s car and he kept pushing me to “Get on the gas!” at corner apex when I “knew” I was at the limit of adhesion.

So I remember thinking “Well I’ll show him, I’ll do what he asks and then he’ll see that the car is going to spin”. I mashed the throttle and the car hooked up and flew out of the corner. “Wait, what?!”

I’m hoping that the transmission shows up before the end of the month because with the wife out of town, there’s an uninterrupted week to do the laborious gearbox swap. It’s going to be a ton of work but it’ll be worth it. Another reason to do it while she’s out of town is so I don’t have to hear about her car sitting outside for the duration.

In my spare time I’ve been (re)reading my aerodynamics books. Until now I’ve skipped the wings chapters because all I cared about at the time was cooling system design and whole-vehicle airflow.

So yeah, I’m a little excited, looking forward to a better track experience, but I also realize that the above changes aren’t a magic bullet and don’t correct bad driving habits.

4 Feb 2018

The wing material is on the way and until it arrives, it gives time to figure out something that’s been bouncing around a long time – my transmission. The current unit is a base-model RSX 5-speed converted to a 6-speed, gears 1-4 being straight-cut with dog engagement and 5-6 being OEM, and a stock Honda 4.39 final drive running a WaveTrac LSD. In short, another transmission’s going to be built. I can already hear it “why do you keep messing with stuff instead of driving it?”, and, “why didn’t you think this through the first time?” Easy answer to the latter: the gear sets weren’t available then. As for the former, well…

Anyway, the existing transmission works great on the street but isn’t optimum for the track on several points. As previously mentioned, 5th and 6th are OEM so they can’t be “used in anger” on the track with a turbo engine (I turn boost down to protect them). This isn’t a problem on the street because presumably you aren’t going >150 mph. The OEM gears can deal with ~160 ft-lbs from the stock engine but users report bad things happen when pushing high torque. Additionally, first gear also isn’t that useful on-track because it’s numerically than optimum, better suited for the street or drag racing. Lastly, the differential works perfectly on the street but like the gears, isn’t the best for on-track. All these issues came together into the idea of building a new transmission and selling the current one while it’s working perfectly. It’s worth decent money, versus practically nothing if I break it. The idea is that it can help pay for the new one, which will consist of:

1. Full Gear-X gear set, with lower numerical ratios and stronger 5th-6th
2. OS Giken LSD (reverse 1.5-way clutch type)
3. Carbon synchros

The final drive ratio will remain the same, 4.389.

Gear-X offers two gearset ratios, identical other than 5-6 which vary slightly depending upon application. Assuming a self-imposed redline of 8000 rpm, the more long-legged set tops out at a theoretical 170 mph, while the very slightly shorter set tops out at 162 mph. The fastest Midlana might ever see is about 160 mph at AutoClub Speedway, but wings are planned, so expected top speed will drop to something less, so the slightly shorter gearset appears best. Back in the practical world, with this gearset, 70 mph on the freeway results in  an engine speed of around 3400 rpm, so that works.

I asked an Arial Atom wonder about the gear ratios since he uses because this particular Atom has as much or more power than I do. The reason I asked is because the Gear-X first gear is really low numerically (2.313) compared to 2.615 of the current PPG first, which is lower than the OEM ratio – it’s a pretty big difference. Because of this, there’s a lot of complaints that such a low first gear ratio makes it all but impossible to take off fast and is “obviously just for road racing, not the street.” The Atom owner correctly pointed out though, that when those ratios are put in a car weighing half as much as OEM, it changes everything and is downright perfect.

Regarding the differential, everything I read indicates that the OS Giken LSD is good for somewhere between 0.4-3 seconds a lap. Granted the numbers are anecdotal with little basis in hard fact, but what was telling was how virtually everyone who switched to it said they went faster. It’s supposedly also able to make the car easier to control in turns. Again, what “easier” means, who knows, but it’s promising that all the comments are positive. BTW, the “reverse 1.5” configuration of the LSD was recommended by the manufacturer specifically for the mid-engine Midlana and would not be a good choice for a FWD engine placement.

Because the above gear set is rated for 500 hp and is also helical, I’m somewhat taking a step backwards. The reason is that for street driving, it’s the right choice for me. On the other hand, for someone who’s built a turbo car for drag racing and wants to be a badass on the street, the dog-box will serve them well.

Lastly, adding the carbon synchros should prevent the dreaded Honda 2nd-gear grind that tends to happen if shifted too energetically for too long. There’s still some logistics to work out but it looks like it’ll happen. When it’ll be done and when it gets installed, who knows.

Okay, there might be one more perk of the above gear ratios. Between the new first gear ratio, the existing final drive, tire diameter, and the engine’s red-line, I can reach 60 mph in first gear – I’ve always wanted at least once to own a car that can do that. The reality is that it’s totally pointless, good only for setting a rather awesome 0-60 time :)

I’d love to try out a sequential gearbox but can’t justify the ~$10,000+ entry fee. There’s the cost, but there’s also the suspicion that it might be a pain to live with in traffic, given how shifts aren’t buffered by clutch engagement, going “bang” every single time, up or down, unless you perfectly match gear speeds. Also, users report that the sequential unit should be considered a wear item (caused by imperfect shifting) that requires periodic teardowns. I think I’ll pass.