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 owner what gear ratios 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.