[Mike2JZ]

Any sequential or dog engagement box will need considerably more maintence then a synchro box due to the design of how the gears engage, regardless of the power. You as a driver need to learn to drive the box in a way that wont damage it prematurely, and ECU tune will need to on point to manage the torque on the shifts as well if you do clutchless shifting. Lots of power makes the previous points even more important.

Those types of boxes are awesome when they are working and really change the dynamic of the car, but make sure you have a budget set aside for servicing on them, also need to consider your downtime if you have to send box off or get spare parts in etc.

Everyone wants to do racecar shit until its time to do race car shit comes to mind.

 

[te72]

Are they that expensive now? I recall the HGT's being about 2k per gear. Planned to slap one onto a K20 swap in a Miata in the future (distance unknown).

I think that was all in, bellhousing, shifter, clutch, and a guess on driveshaft cost. They're not cheap, but you're not going to get that level of performance for the weight anywhere else.

Look up ASMotorsports, they run One Lap with a K24 swapped S2000, and do VERY well with it. They run the BMW DCT, and I was very on the fence between them. The gearing on the DCT is better, but after talking to Andy with ASM, I was more inclined to go with the HGT. Like I said, it's very much not a plug and play affair with the DCT. Now if someone were to come up with a truly drop in setup for JZ powered cars, it would likely still cost 10-12k, if not more.

The actual transmission from HGT is roughly 2k per gear still, but the other stuff adds up.

That's why I want to go the BMW DCT and get my speed set through gearing and not power. My supra is being built for autocross/ time attack/ endurance blah blah blah lol. But yes even though the DCT are heavy bastards I think its worth the weight penalty and reliability. And since I'm planning on going 1.5way LSD rear end my biggest thing is constant abuse reliability.

Good thing about transmission weight, it's actually not the worst place to add weight. It's low, and well between the axles.

Good plan to get your speed through gearing and not just power. Look at modern cars, even 200-300 hp cars are rather silly these days, and it's because of things like direct injection, responsive turbos, high compression, but more than any of that... gearing. Keep an engine in its happy spot, and it will be a rewarding experience.

Reason I suggested the HGT is that you will be up and running far before you ever would be with the DCT. Plan your differential around running a particular transmission and you'll come out ahead. I did that for my R154, and went with a 4.10 ratio. Coincidentally I ended up with the perfect setup for a T56 Magnum as well. HGT, a bit less so, as its sixth gear only has a 0.88 ratio for overdrive options. Cruising at 4000+ rpm is fun, but it wears you out on the highway.

OS Giken that rear end, by the way... just trust me on this one.

Any sequential or dog engagement box will need considerably more maintence then a synchro box due to the design of how the gears engage, regardless of the power. You as a driver need to learn to drive the box in a way that wont damage it prematurely, and ECU tune will need to on point to manage the torque on the shifts as well if you do clutchless shifting. Lots of power makes the previous points even more important.

Those types of boxes are awesome when they are working and really change the dynamic of the car, but make sure you have a budget set aside for servicing on them, also need to consider your downtime if you have to send box off or get spare parts in etc.

Everyone wants to do racecar shit until its time to do race car shit comes to mind.

It really wasn't that bad. When I was talking with Richard of HGT, and let him know what my typical use case was (couple thousand street miles per year, and as much autocross and road course as our short seasons would allow) he recommended that I drop the transmission for an inspection and fluid change every two years. Said he didn't expect it to require any rebuilding given that I was well within its operating window.

Driving it properly and having your ecu tuned to work with it is important, you are right. I believe it was closed loop operation that I was asked about when I was looking into it. Basically the strain gauge on the shifter sends a minor voltage to the ecu, as soon as you put force on that shifter, the ecu cuts torque output so the engagement on the next gear is softened.

As for budgeting, yes, yes a thousand times. Always have spare budget set aside for cars like this... but as for downtime, isn't that what determines a Supra's worth?

 

[Mike2JZ]

So I actually have some first hand experience with HGT, samsonas, quaife, hollinger, PPG on various supras & skylines. They will all tell you the same thing about how long it should last, but it usually ends in tears one way or another, usually from the fault of driver or overpowering the design or bad luck. Some brands are considerably better than others and built to tighter tolerances, better materials etc, HTG is good and their support is nice so defnately a good option. But a dog engagement box will always wear its dogs over time by design, you can't escape it. So just keep it in mind, you arent going to be doing 10'000miles a year with them and doing trackdays every weekend all year with no issues. My advise is, if you are going to track this thing a lot then service intervals to strip and inspect box should be twice a year. Far easier/cheaper to maintain the box when you know of problems developing and track them, rather than just fixing the box when the dogs are fucked and all sort of gear material has circulated round a gearset for X amount of time.

Closed loop control will help. Even open loop can work fine, the most important thing I've found is ramping to torque in and out smoothly to avoid bouncing the dogs as torque is re-applied. You will also need to preload the box correctly before engaging any cuts to get the most direct/fast engagements for the dogs. The more power, rotating mass and the heavier your car is the more you will need to pay attention this is done properly.

 

[te72]

That's some good info Mike. Sadly, I'm just a dreamer for the most part. Have a lot of experience with these cars and know a lot of what NOT to do. Really wish I'd put the money into the transmission rather than the engine myself. I could have lived with a yearly inspection, no problem. At this rate I'm basically going through a transmission a year anyway... and the HGT would have actually put up with my aggression. At 80 lbs, a transmission job would be easy enough anyway, as opposed to the ~120 lbs for an R154.

Actually, silly as this sounds, that weight drop is one of my biggest motivations for wanting to go sequential. I have / had plans for a 3300 lbs Mk3 with me sitting in it... and still retaining a lot of what made them great road cars.

 

[Theneil300]

Yea te72- I prep race cars and the transmission is a heavy wear item, and when your weekend is about 25k you’ll be inspecting your dog box after every weekend. Race cars driven like they are on a race track are tearing themselves apart the whole time, the main and countershaft are trying to spread apart and tear all the teeth off, the dogs are chipping and a perfect shift isn’t really in the cards when your wheel to wheel going 180 into a corner , it’s more about not crashing when your pulling 2G on the brakes trying to hold your line with 6 other morons right next to you

out for blood.

 

[te72]

Sounds like a good time, apart from the stress. I like karting, definitely more in my budget haha. I've only got that much into ONE of my cars, the rest generally fall well under that.

But hey, if you have money to blow and someone else doing the work, then full inspections are always a good idea.

 

[Supra_kewl]

Hence why I just plan on going DCT, and yes OS Giken LSD was already in the works lol.

 

[te72]

Makes sense I suppose. Just expect to be into it $10-15k and for it to give you plenty of headaches to sort out. Make room for a rather large transmission cooler somewhere.

 

[Supra_kewl]

Makes sense I suppose. Just expect to be into it $10-15k and for it to give you plenty of headaches to sort out. Make room for a rather large transmission cooler somewhere.

My front has all the room for an additional cooler since my radiator sits in the rear with the diff cooler and fuel cooler. I was planning on allotting about 20k after the engine stuff was sorted out just for the rest of the drivetrain to be completed.

 

[Mike2JZ]

Personally I'd look into ZF 8HP boxes over DCT currently. Turbolamik runs it super well, wheras reports are the DCT is a bit hit and miss depending on implementation

 

[te72]

So Mike, what all would be involved in running the 8HP? Surely there's plenty of tuning involved on that option as well?

 

[Mike2JZ]

Not really. The turbolamik runs the 8HP like stock out of the box really, so dont really need to touch anything to do with gearbox mapping unless there is something specific you need to do.

 

[te72]

Interesting. I don't really know automatics very well. In an application like this though, I'd personally prefer it to only run manual control though. Nothing like a highly loaded car, mid corner, suddenly changing gears on you... I've seen that put more than one Supra into a ditch.

 

[Mike2JZ]

Interesting. I don't really know automatics very well. In an application like this though, I'd personally prefer it to only run manual control though. Nothing like a highly loaded car, mid corner, suddenly changing gears on you... I've seen that put more than one Supra into a ditch.

Yeah you can have full manual mode, clutch pedal and some other cool features. Have a look through youtube, its definately not just an auto in the traditional sense.

 

[te72]

Clutch pedal with a torque converter auto? Well that's rather interesting on its own... I'll never likely be a customer, but it does pique my interest. Thanks for sharing Mike.

 

[Supra_kewl]

Alright peeps, using my new skillset of Cardboard aided drafting I was making my front channeling for the intercooler and I gotta say practice makes this a lot easier for sure. Now my front bumper is pretty much done for and whatnot but I wanted to see how it would look so I mocked it up just too see how it will looking whatnot.

 

[te72]

That looks fantastic. If / when I ever do another project along these lines, I think I'm going to make the ducting, then fit the bodywork to the ducting. My first effort was definitely a bit on the rough side, but it's functional, and that's all that mattered at the time. Keep it up!

 

[Supra_kewl]

That looks fantastic. If / when I ever do another project along these lines, I think I'm going to make the ducting, then fit the bodywork to the ducting. My first effort was definitely a bit on the rough side, but it's functional, and that's all that mattered at the time. Keep it up!

Thanks!! Still trying to figure everything out but the 88c cardboard helps a bunch get the exact dimensions. wish I had / knew a 3d printer to get some of these pieces made then make the negative to make fiberglass or carbon fiber versions.

 

[te72]

I don't know much about 3d printing, but I would imagine that would require a decent sized machine to make that happen. Probably a heck of a lot cheaper to make a buck out of wood or foam, then make the ducts out of composites.

 

[signalpuke]

Why not sheet aluminum?