Definitive solution to 20b transmission - HGT Sequential
 

I"m sure most of us already heard of HGT transmission. It's a sequential transmission box that will handle 750ft-lb and high rpm shift. Final gear is 1.0 so keep that in mind.

The guys at HGT says they are looking into making their transmission bolt-on to our manual bellhousing. This is huge. This means keeping our clutch, starter, TO bearing, and slave. You will have to make the mount. This will save us about 3-4k for the swap and virtually guarantee fitment.

I wanted to ask how many would be interested in buying with this option. They will look at offering this more seriously if I can get some genuine buyer list going.

BTW, I won't make a cent by doing starting this thread or trying to organize the purchase. I just want this to happen and want to gauge the interest and if high enough, set up a group buy. Any discount, if any, will be distributed evenly.

I also think T56 is a great option, but it potentially poses a huge headache for many of us. most of it has to do with all the custom parts we need to piecemeal together. limited clutch option, everything from pilot bearing machining, starter fitment which blocks third rotor housing plugs, hydraulic TO bearing, lines, adapter for the TO bearing, etc. I personally haven't seen any T56 conversion kit that has seen any decent mileage.

The sequential box is also much ligher than the T56. Just wanted to gauge interest for now.

eh I guess not. Had to ask :)

Did you see Quaife recently came out with this drop in 6 speed sequential for the FD? $10K-13K

https://shop.quaife.co.uk/mazda-rx7-...ential-gearbox

It is rated 750bhp not 700ftlbs like the HGT unit, but it does have internal oil pump instead of splash lubrication, so it might be more durable in the long run.

Its Quaife...

I'm interested
 

Question: most all 20b came with automatic bell housing. So which bellhousing should I use with my 20 b for this unit?

Both Boxes are pretty good. HGT is a bit newer and I've talked to the owner on multiple occasions. They've already got Boxes in a handful of Rx7 and Rotary powered cars all over the world. They'd be my first choice for sure.

Its looking like great option. Owner stated that it won't even require the tilton pump/cooler unless you're tracking extremely hard, which would save a tad bit more. He says it should be good for over 900nm of torque, which is tons higher than the Quaife.

I also asked about dog replacements. He says you should get about 50hrs of continuous use out of the box (this is very frequently ie track use) before needing to service the dogs. Estimated no more than a couple hundred bucks for new dog rings.

The only downside (if you want to call it that) I see to this box is necessity of having to run downwards through all 6 gears to get to neutral on the street, and wearing out the dogs quickly. I mean I guess you could just clutch in and stop the car abruptly, then shift through them. The other downside is no overdrive, though he did mention that they may have an option out soon with a 0.86 ratio 6th IIRC

I would love to see you run this box. That coupled with your insane traction logic setup and you'd have one of the fastest cars in the states.

hit the nail on the head. The biggest downside I see is lack of overdrive which limits top speed and sucks for normal highway cruising. If they can offer low 0.70 overdrive, I would most likely start saving for HGT. If I knock down the rear diff to compensate for the gearing, I would need 8.8 which is more cost and weight..

The necessary downshift to the 1st gear isn't ideal for street driving for sure. but the upside would be the clutchless shifting which can be done with haltech and possible pneumatic assisted shift in the future which then would make downshifting all the way to the first gear a joy every time.

I'm torn... I'm also worried about longevity of these sequential boxes. I know the T56 will probably outlast my engine if not my car. Just not sure about HGT....

Good to hear that the cooling pump is an optional add-on.

HGT offers 0.88 overdrive now. still pretty high for the street... it may be too much of compromise for the street unless you go with something like 3.2 rear diff or something.

Just to clear it up. I talked with the Owner of HGT about Clutchless or "Flat Shift. I had told him that my experience was that the only time we ever used it was at 100 TPS. Meaning Foot Flat. Off throttle shifting on decel is possible. But again....until you actually have the box in the car I think most people forget how frequently you visit neutral in a street car. Sequential box for the street sounds cool because we all like race car stuff. But the reality is it's an absolute pain in the ass.

If you can ride a motorcycle you can live with sequential shifting on the street (obviously).

Just a bunch of old lazy habits most people have to unlearn really.

This is a good point.

IE coming up to a red light you start to slow but then it goes green again. clutch in from 6th down shift to appropriate gear, slowly lift off clutch, car in gear again and starting to deaccel apply throttle and get back up the speed.

its the part/light throttle shifts that are going to be the biggest pain in the ass on the street.

Well, some of our moms taught us to drive cars by always downshifting while slowing, never coasting in neutral or with clutch in and always being in the right gear to accelerate.

A real pain with this on a big port rotary is when the motor starts shunting under light load.

You do have to kick the clutch in let the motor settle and come back in with more throttle/more throttle and higher gear when you ease the clutch back out.

It is easier/tempting to just put it in neutral and coast if you are going down hill or in a parking lot coasting, etc.

I honestly don't think any of us really like true "race car" stuff. We want our stuff to last a long time and I for one want it to be streetable which means minimal noise, easy engagement at various rpm, and reliable.

I have been exchanging email with HGT and realized that these are good for around 5000 race miles. I genuinely asked whether they think these boxes will last 50k miles of easy street driving. They probably thought I was half joking around. Their answer was a firm no.

So... this is the true "race car" transmission. I am upgrading transmission to ensure they will be worry-free for tens of thousands of miles before rebuild or replacement. To be fair, the rebuild cost is pretty cheap but if I didn't mind rebuilding my box every 5k-10k miles I would just stick with the FD box.

This is why I've been strongly considering straight-cut gear set for the FD trans. Of course the dog rings will wear out just like the sequential, but at least you can minimize the amount of up shifting / downshifting. The company I've been talking will also make custom straight cut gears with synchro's instead of the dog rings, which would give you best of both worlds, though your shifts would be slower.

You could do the CD009 or T56, but after seeing a T56 on a 3 rotor FD, its a no for me. It barely fits in there, and you have to pull the engine to pull the transmission, unless you want a world of pain.

I know alot of your concern was noise. The company I was telling you about has a new gear design requiring less backlash and less whine. You gotta see the videos.

Meet your next best friend :icon_tup:

hahahaha