The transmission is back from the shop after being freshened up and is now for sale. Details on the Ebay ad
Here you go – Rear engine mount test video
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.
I started typing up what’s “on the list” in the Midlana forum and it just kept growing, so I thought I’d post it here as well since it sees more visitors. In no particular order.
The transmission shop is repairing and inspecting the transmission in preparation for its sale – ad here http://www.midlana.com/forum/viewtopic.php?f=22&p=8941#p8941
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.
The pieces of debris are from a synchronizer hub, which is probably the best of all the things it could have been. “Best” meaning that they’re not bits off the expensive aftermarket gears and being an OEM part, it’ll be less expensive to replace. The transmission will be sent to the same place that built the new one, which works out well since they regularly build PPG gearboxes. When the unit is put up for sale, it’ll be advertised as having been verified as 100%-good.
The rain let up so the car was taken out for a short test drive. The new gear ratios are closer, with first gear being the most noticeable. Now, the car sounds much more like a road-racing car when leaving a stop; with the lower ratio, the ratio has to be slipped a bit more. Being new, the synchros are a little sticky but that’s to be expected. It’s true what Honda owners said about these gears (and the ratios) are terrible – for OEM-weight cars.
With everything that was removed and replaced, it was good to see that nothing leaked or fell off. The rebuilt rear engine mount though, is transferring too much vibration. I’ll probably have to redo it again and am considering something like having a block mounted off the engine that in cruise conditions, “hovers” between two rubber-lined stops in the engine mount. That way, vibrations will only be transferred when under hard acceleration. We’ll see.
First, the good news –
Got the axle CV cup back, assembled the driver’s-side axle, then filled the transmission with OEM fluid to break it in. With some rare rain going on though, the test drive has to wait.
With the car stuck in the garage, finally got around to added 15-mm wheel spacers, since I’ve long had tire scuff marks on the inboard panels. Adding the spacers necessitates cutting down the OEM wheel studs, which went fine and while I was congratulated myself on my fine work, my brother called. I asked what his tire-to-chassis clearance is and was surprised when he said less than 1″, which is what I had before adding the spacers. Well nuts. He reminded me that the tires I’m now using (same as his) have stiffer sidewalls (though I don’t know how he knows that), so that’s one variable. Another is that he has roughly 450 lbs on each tire, while I have around 600 lbs on the rear tires due to being mid-engine. Another difference is that my rear suspension is IRS, so the tops of the tires move inboard under acceleration and braking. Between all these differences, it’s unknown how much the tires will squirm around. The irony is that having added the spacers and switched tires, while there won’t be any rubbing, I won’t know why. Oh well.
The bad news, well, I’m not sure how bad it is yet.
When I took my old transmission to WaveTrac to have them fix their differential design flaw, I expected them to do just that, pop out the stuck axle stub, fix the LSD, then give me a call. Well, they did:
Them: “While we were in there we also found some gear bits stuck to the magnet. We’re sure you will want to fix this so we’ll hand it back to you taken apart.”
Me: “No, I want it reassembled, then I’ll decide what to do after seeing the little parts.”
They agreed, I drove up to get it yesterday, and:
Them: “Okay, here it is, reassembled but not sealed.”
Them: “We’re sure you’ll want to take it apart, so there was no reason to seal it.”
That isn’t what they agreed to do… Anyway, when they handed me the parts, they did indeed look like broken gear teeth. After thinking it over and looking at them again later, I’m not so sure; the “teeth” on them are really small, flat-topped, and not helical. I’m wondering if they’re off some sort of slider component, though why that would break instead of the gear teeth is a mystery.
Anyway, the first step is to identify what these bits are. At best would be hearing they’re of no consequence (yeah, I know) and at the other extreme, it gets shipped to a tranny shop and torn down – again.
Made the self-imposed deadline – the drivetrain is back in, hooked up, and running. Driving it has to wait until the missing axle piece is back, but it’s basically done.
I’ll check online to see if the gear manufacturer, Gear-X, recommends any particular break-in oil, or just go with the stuff they gave me.
With this out of the way, it’s on to wings!
Drivetrain reinstallation should be complete tomorrow. The goal is to have the garage cleaned up before she gets home. It will be, well, all except for one rear wheel and tire because I don’t have the driver’s-side CV cup back yet.
Speaking of that, the differential shop said they were able to remove it without damage and also fixed the differential. The transmission will be picked up this coming week and then it’ll go up for sale.
Pictures from today show there’s a lot of stuff in a twin-scroll turbo car with a dry sump! Several hours were spent looking for hoses touching anything else and they got the dual zip-tie treatment to keep them from abrading.
The last shot is a reminder to all builders to always snip off the left-over tang on Nylon zip ties. I can’t count the number of times an overlooked one caused needless bleeding.
So there’s always the question: make the parts myself using the lathe (the dowel pins in this case), or just buy them. Given what they do and because I needed two, I took the lazy way out and stopped by the dealer. In the first picture below are two dowel pins. One of them cost $1.72 and the other cost $3.55, so why is that? The Acura dealer only had one in stock (I needed two) so they called the Honda dealer down the block and confirmed they had another, and who charged me double. I couldn’t help but wonder if they figured (correctly) that I was in a bind and doubled the price. I paid it but will keep that in mind.
While leaving, there was a formula car on display so a few pictures were taking of the wing support, which appeared to be 0.25″ aluminum plate. I fell better about seeing that so I won’t feel bad building a similarly-strong/heavy support. The wing itself appeared fake, likely explaining why pitch wasn’t adjustable.
On the way home, stopped off at a off-road shop and bought plastic plugs and caps for the AN hose ends. They help keep dirt and debris out of the AN fittings while they’re disconnected – I should have bought these years ago.
Anyway, once back home, the pins were installed, the engine/transmission mated up, then the assembly reinstalled. Amazing how much easier it went in… after the tank and shifter bracket were removed to be out of the way, and noted for next time. The rest of the day was spent reconnecting and reinstalling various bits; it always much takes much longer to install things.
The engine’s out but I didn’t help the process due to the combination of cutting corners and forgetting what had to be removed first. Lifted it halfway out and it got stuck between a chassis tube and the dry sump tank. End result, one scratched up chassis tube. Also left the push-pull cable bracket hanging free, thinking it wouldn’t get in the way… wrong. It of course got wedged between the chassis and the transmission. It’s a very unpleasant situation trying to unstick an expensive 400-lb lump hanging tenuously by a chain…
Finally got it out and safely on the ground, then removed the transmission. Transferred everything over I thought I’d need: the throw-out bearing and lever, plus the push-pull shift lever plate. Immediately loaded it into the truck and delivered it to WaveTrac, who will remove the stuck CV housing and fix the known circlip groove issue which was in an early batch of the units. That way I can both sell it with a clear conscience and advertise it as having a known-good differential.
Got back home, intent on plugging the new transmission onto the engine, then realized the new transmission has the same issue the old one did: a lump of aluminum near the input shaft that’s just high enough to contact the spinning clutch. (I contacted Competition Clutch about this back when it was noticed on the original transmission and was surprised by their seemingly disinterested shrug.) Did a measurement and sure enough, the lump is 2.435″ from the front end of the bellhousing, and the twin-disc clutch extends 2.44″ into the transmission. Well, yup, that’s a problem, cured by a die grinder. Hard to believe that I’m the only one on earth with this interference problem, but it’s likely anyone using a twin-disc clutch is putting it in a noisy race car and never hears it grinding away…
With that done, time to plug the transmission into the engine, only that requires two dowel pins for proper alignment, which of course were stuck in the old transmission… far from home – well nuts, guess I know what I’m buying tomorrow. To not waste time, other odds and ends where completed, removing the old gasket off the exhaust manifold and grinding a recess in the dry sump pump bracket so that it no long contacts a stainless-braided hose.
I just keep reminding myself, “This is all for fun!”
It sometimes seems to take women forever to get really ready to leave. Reminds me of a comedian who said that when your wife says she’s ready to go, it means you can watch the second half of the game and not hold her up.
Anyway, with the “storage area” of the garage freed up, work continues on pulling the engine. Interesting what you find when you take apart a car when you think there’s nothing wrong:
Leaves, dead bees, and small rocks in the intercooler – surprising given how little time the ducting has been in-place.
A braided-stainless oil line that passes right next to the alternator bracket, where the two are wearing into each other.
Found the mystery oil leak that’s been messing with me every since the engine was installed. I’ll get a better look once it’s pulled out but there’s strong evidence of a casting flaw that’s allowing oil to leak right through the pan. Will either weld it or use something like JB Weld or even gasket sealer.
Will probably pull the drivetrain tomorrow, then immediately drive the transmission to WaveTrac to have the axle CV housing removed and get the differential fixed. They don’t want me hanging around, waiting for them to remove the axle part, so it means delaying getting the fully running. The reality though is that the delay probably won’t matter because it takes a lot longer connecting everything back together than removing it, and then there’s the side project of correcting the rearr engine mount.
Started in on the transmission swap, just ancillary parts for now since there’s no room to store the big stuff yet (wife’s car’s in the way!). During removal and inspection, found the likely source of the recent vibration that’s been noticing during acceleration. The rear engine mount plastic insert has deformed (squeezed out) enough to allow the two halves of the mount to contact metal-to-metal, hence the extra vibration. With more than 400 ft-lbs of torque, I guess I should expect this sort of thing. Going to have to redesign the mount but that can be treated as a separate project.
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.
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
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…
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!
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 🙂
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.