Change gear ratio?
 

So im not an expert but a buddy of mine has a mustang ppl are know for changeing out the stock gears to 3.73 or 4.10's. Now im not sure what the FR-S final drive is but could we change it for quicker 0-60 times like the mustangs?

It's 4.10 here. The only lower ratio I can think of that may have chance is the 4.30 from a NA Mk3 Supra. But that's pretty much ancient history. Japan gets 3.73s on their base model.

So could we change the to 4.30 and would it make a difference? Im sure some company will pick up makeing some aftermarket gears i there is enough demand for it

We don't know yet. The diff may be an evolution of the Mk3's but that is 25 years of evolution, so they could be too far changed.

4.30 wouldn't make enough of a difference for the work, unless there are engine mods that increase the rev limit and the power up top, I think.

Oh i see and anything shorter would most likely hurt fuel economy and such so wouldnt really be worth it

If it were shorter, people would bitch about fuel economy and possibly noise/vibration from turning higher rpm. You can't please everyone. If there is enough demand, the aftermarket could supply a new final drive ratio.

Has the aftermarket ever provided a single different gearset? 0.61 6th gear would be a milder rpm drop going 5-6 than the 1-2 shift, and would save a crapload of fuel on the highway especially if you're going under 70mph.

For a small change you could use smaller diameter tires.

and throw off the speedometer if you don't have a way to change its calibration... The vehicle speed should be calculated by the wheel speed sensors through the stability control system. So if the final tire diameter doesn't change it the speedometer would remain accurate.

I would think that changing the final drive ratio would be the easiest solution to turn higher revs without other drawbacks.

I was wondering about this. I'm not planning on tracking my car, just having it as a daily driver. I was wondering if I could make 5th and 6th, or maybe even just 6th, a little longer to make it about even with the AT. Probably get 35mpg highway vs 30 currently. I guess I'd have to consider cost, potential warranty issues, etc.

For Subaru there are a few options, PPG is one company. For Toyota, Marlin Crawler has offered gearsets for the old R series transmission (Mk3 Supra and trucks).

But these were performance and strength oriented rather than economy.

On the surface, it certainly seems like turning fewer rpms would yield fuel economy benefits on the highway. And it might in certain situations. But I'm not sure where you get an additional 5mpg from--where did you get that number? Do you really think that, if 5 highway mpg (even 2) were achievable with no drawbacks from something as simple as a gear ratio change, that Toyota wouldn't have done it?

Here's what you have to keep in mind. It's a relatively high revving 2 liter engine with limited part throttle, low rpm torque. It's not a GM LSx V8 engine. If you put the thing in top gear and accelerate at Interstate speeds like on the US06 drive cycle used for certification, you are going to load the engine down further.

http://www.ft86club.com/forums/attac...1&d=1335721306

Not only could the vehicle feel more sluggish than if it had shorter gearing, the exhaust temperatures are going to increase from the additional load. Then the stock ECU would probably enrich the mixture to reduce exhaust temperatures so the cat, exhaust manifolds, exhaust valves, etc will be protected. So there goes part of your fuel economy benefit. From Toyota's perspective they could have trouble meeting CO emissions standards from the enrichment that results from lugging a high revving, small displacement engine.

Remember that due to taxation the manufacturer already has an incentive to get higher fuel economy for the vehicle as long as that doesn't cause other problems.

Why would they use the huge rear end from a Supra? More likely it's the same size as the RX-8. Those have 4.444 and 4.777 gears.

Options would still be nice. The 4.1 is a compromise.

I believe the 3.727 gears only improved MPG by 2-3 but I'd have to check again to be sure. Since the OD gear is the tallest one available in the transmission. You'd have to get a custom Overdrive gear which is $$$.

Taller gears do improve MPG to a point. But you will lose some low end acceleration. What arghx7 is saying is that if you increase the load to the open loop enrichment part of the map you will eat up any MPG benefit. It's the same way if you shorten the gear ratio so that you're cruising on the highway in open loop, your MPG will be atrocious.

I believe it's the same diff as the IS which has its roots with the old Supra and that's the only lower diff ratio I could remember off the top of my head. Trans is related to the RX-8, but not sure the diff is.

Just to get this straight, the Beams powered IS/Altezza also had the AZ6. But did they all share the same rear differential?

I wouldn't go longer gear as well. It will hurt the acceleration which I don't want. I am thinking 4.5 or 4.6 would be nice, it will be a 10% noticeable difference by math.

So the BRZ diff is a Toyota diff ? Or a Subaru diff ?

I'm not 100% certain but given Toyota's past models the diff pumpkin and axles will be universal for the model but with internal ratio and open/lsd options to suit the car's performance.

I think Jeff Lange on here could clarify.

Toyota.

arghx7 IIRC the EPA test doesn't even spend much time in 6th gear does it?
If the AT cruises along at super low rpm, and it does fine on emissions, what's the problem with having MT do the same? I guess the AT automatically kicks down a gear for acceleration which would reduce CO/HC and stuff, but last time I checked higher load in closed loop decreases CO/HC, so it's not clear to me that this is an emissions related thing.

I did a few rough extrapolations and the AT gearing allows the car to be near the BSFC-optimal load point at 80mph, so I think fuel enrichment is only an issue if you're trying to floor the gas in 6th while at 2000rpm or if you're going like 100mph, which you shouldn't be doing on the highway.

That's why I think something like a 15% decrease in 6th gear rpm would be nice, you maintain more passing power than the AT, it'll drop 75mph rpm to ~2600rpm and reduce noise, and will improve fuel economy by a little, which matters a lot to people who commute long distances. I used the BSFC chart for a 1NZ-FXE and specific torque, so it's going to be a little bit different, but the fuel consumption difference was ~15% at 60mph, ~10% at 70, ~8% at 80. If the FA20 is better at being efficient in low BMEP range then the difference is smaller, but the EPA test is coming back as 34 vs 30 which is a massive difference :/

Part of the reason why I think this is a good idea is because the moment people start trying to rev this engine higher, people will start dropping higher final drives in to increase acceleration, and it would be particularly nice if that didn't mean cruising along the highway at S2000 like rpm.

The US06 does. See attached standard shift schedule from the EPA website--scroll all the way down to the bottom for US06, 6 speed manual (it's in some weird ass format). You will notice that it is ~1200 seconds long. That's because the US06 certification test actually repeats the same drive cycle; the first ~600 seconds is a warmup and doen't actually sample from the tailpipe.

http://www.ft86club.com/forums/attac...1&d=1335721306
in the standard EPA shift schedule, you are in 6th gear from seconds 62-122 and from seconds 147-488.

We don't know if the AT does fine on emissions. It might do really well or it may be borderline.

If the vehicle has to enter enrichment, CO is the main thing to suffer--CO is very closely related to the AFR entering the converter. CO is the big concern on the US06 cycle. On other cycles it isn't such a big deal because the engine is under a lot less load. HC is typically a bigger deal on cycles that have a cold start component (LA4/FTP cycle) due to unburned fuel and catalyst light-off.

Ah but the US06 goes to 80mph and with the standard shift schedule you are in 6th gear. And then it depends on the road load coefficients used on the dyno. When they run these tests, the dyno uses exponential road load based on a quadratic function. The coefficients of the function (A + (B)x+ (C)x^2) and the weight determine the road load. There's a whole process for determining these values. They are there to approximate wind resistance etc.

We don't know if it will reduce noise. It depends on the resonant frequencies of a bunch of things. It might though. Somebody in the NVH (noise, vibration, harshness) engineering department would know. But of course they're not talking.

Hopefully, but it's hard to say how much. I'd like to see how back-to-back tests on a US06 with two different 6th gear ratios.

The 1NZ-FXE is a 1.5L miller cycle engine for a hybrid (1st and 2nd gen Prius) with a power-split planetary gear set for a transmission. It's not a sports car with a 6 speed manual transmission or conventional 6 speed step automatic. FYI, You know Toyota just brought back the 1NZ-FXE in revised form for the new Prius C? They added a bunch of EGR to it and the BSFC map has changed.

Unless Toyota publishes a BSFC map, nobody will ever know the BSFC curve without spending $Texas to buy a production engine and do combustion analysis on it.

It's hard to say exactly what causes the big difference in mileage between the A/T and M/T, and I'm just curious as you are. The EPA numbers are calculated based on 5 test cycles and weighted according to an arcane formula. The throttle mapping, gearing, A/T shift schedule, lockup schedule, VTC mapping and all sorts of stuff could be causing the huge difference in numbers. A few people know, and they're not talking.

If you're that far into the game, you would hope that you have an aftermarket cat, tuning to reduce enrichment under heavy loads (enduring higher exhaust temps), and a way to turn off check engine lights for catalyst efficiency. So the whole situation changes potentially. I was more referring to a situation of a mostly stock vehicle but bolting on a catback and different rear end like people do on Mustangs and Camaros.

Yea I guess you're right.

I didn't notice before, but the US06 cycle has some brief but quick acceleration in 6th gear, and I suppose that could possibly be an emissions concern.

I was told that the diff is an R200 (?I think by Hitachi?). If so, it's stout, and that also means there are plenty of OEM and aftermarket gears already out there. It's been used on a variety of cars out of Japan for decades.

I hope there will be some aftermarket mod or shorter differential for a shorter final drive. The 6th gear is just too long.
Every hot hatch I've driven (Mini JCW, Renault Megane R.S.) could hit the rev limiter in 6th gear. If i want to look after fuel consumption I'd rather buy a Prius.

The differential is not an R200, it is a Toyota unit. In the past referred to as the G-series (8.0") it is now referred to as the F20SX/F20TX/FD20A/FD20AT (205mm) unit. The same basic differential was used in many Toyota cars and trucks, notably the 86-92 Supra, 01-05 IS300 (with the same Torsen T2 LSD that the Zx6 gets), and the 06-15 IS250. The older models usually have a different outer case (pumpkin), however the internals are still near identical. The newer models like the IS300/IS250 have the same case and internals as the Zx6 in the 86/FR-S/BRZ.

There are many ratios available for these cars, and quite a few part numbers out there from Toyota, even for the same ratios (ring & pinion sets typically include the pinion seals, stake nut, ring gear bolts and retainers -- if applicable). Using older Supra ring and pinion sets will require you to get a different pinion seal, as the housing is different.

Still, here is a partial list of some of the ratios available from Toyota, along with some of their part numbers that will work in the Zx6:

3.58:1 - 41201-80125
3.73:1 - 41201-80050
3.91:1 - 41201-80052
4.10:1 - 41201-19605
4.30:1 - 41201-29606 (Included pinion seal will not fit)
4.56:1 - 41201-19557 (Included pinion seal will not fit)
4.88:1 - 41201-80183 (Included pinion seal will likely not fit)
5.13:1 - 41201-80300 (Included pinion seal will likely not fit)

As for the TL70 (Aisin AZ6) Transmission, it is very similar to the Toyota-designated J160 transmission from the Altezza RS200, but the ratios are actually the same as the AZ6 used in the Silvia S15, Nissan-designation FS6R92A. The TL70 in the Zx6 is a newly developed version of the AZ6, though it shares most of its design with predecessors. While most of the gear and synchro setup between the TL70/J160/FS6R92A are all the same, the external cases vary quite a bit, and the TL70 has a different shift pattern, placing reverse beside 1st instead of beside 6th. That gear pattern difference obviously necessitated considerable revisions to the shift linkage internally. The TL70 in the Zx6 also has a larger case, allowing for a higher gear oil capacity (1.8L for the FS6R92A, 2.2L for the TL70).

The TL70 shares a similar style case to the J160, both utilizing remote-mount shifters, while the FS6R92A had the shifter mounted directly on the tailshaft housing.
The TL70 shares gear ratios with the FS6R92A, while the J160 has a taller 1st gear and a shorter 6th gear, the TL70 and FS6R92A have a shorter 1st gear and a taller 6th gear (selected presumably for better fuel mileage).

EDIT (04/30/2016): Updated some information, added a couple more available ring and pinion sets.

Jeff

The big hang up for me deciding to buy one of these cars is the lack of power but knowing that a gear swap is an option (and maybe a reliable FI package) would help make the decision a lot easier. My background is with modern muscle cars (Camaro, Mustang, Challenger) and with the 6 speed transmissions these days you can get away with more aggressive rear end gearing without it effecting fuel economy much. The lower gearing improves "city" economy and the tall 6th gear helps minimize the impact at cruising speeds. We typically see no more than about a 2 MPG loss when swapping a Camaro SS from 3.45s to 4.10 but the equivalent torque gain is approximately 20%.

We don't know tuning specifics yet here in the States, but in Japan, we have a few companies we are working with some companies that have come up with final drive kits. As to the overall impact to fuel economy / power gained, we have to communicate with the companies directly with consumer concerns and desires. Here is one example we are currently offering from ARROWS Japan...

http://i584.photobucket.com/albums/s...nalgearset.jpg

offered currently in 4.556 or 4.3.

Please PM us for other options or for more information. Best thing to do is give us a call with your overall goals so we can custom tailor product packages for you and your budget.

check it out in our thread of other Arrows products if you'd like (here)

:party0030: PM sent.

@Jeff Lange

Jeff, are the Marlin Crawler 8" ring and pinion sets the same 8" guts?

If so that would give us heavy duty 4.11:1, 4.56:1, 4.88:1 and the 5 something options...

I know there are some differences between the trucks and cars as far as bearing thickness and ring gear spacing. I'd have to do a bit more research before stating 100% that the truck gearsets would fit the Zx6, but it is likely that there are some USA-sourced gearsets that would fit, yes.

Jeff

Man a 4.56 would be $$$.

What's the difference in the pinion seal, and is there a pinion seal that will fit?

It's a different outer diameter. The pinion seal meant for the FR-S will fit.

Jeff

I ordered this from my Toyota dealer. Delivery is promised to be with in 2 weeks.

4.56:1 - 41201-19557 (Included pinion seal will not fit)

Just recived my Toyota final gear kit.

I hope I can install it during the weekend

http://i1278.photobucket.com/albums/...psca55bbff.jpg

http://i1278.photobucket.com/albums/...ps596fa854.jpg

http://i1278.photobucket.com/albums/...ps930b9b9e.jpg

ohh yeah? does it fit bolt in ? that would be great for a boosted car running a high speed track !

Please let us know what other bits you needed to install. Thanks!

Well, though I have limited personal experience with a gear change (via a 5.0 mustang). I went from 3.27 to 4.10 gears in an automatic transmission. Wow, what a positive difference in performance that made. This was a naturally aspirated car with only boltons, no head or cams, just the full exhaust, pulleys, airfilter and a good tune. It ran on 91. It made 215hp and 288 tq on a dynojet in 86 degree weather. From personal experience (though in a sense comparing apples to oranges 4cylinder vs 8) I would not change a gear ratio from 4.10 to 4.30's. This assumes a street car and a budget minded enthusiast of course. However, I would consider going to a 4.50+ if I was to change gears. I would need to take the amount of highway miles (average speed or speed limit) into consideration. Also, like one of the others mentioned, tire size/wheels makes a difference also, as this "changes" the gear ratio. These two combinations can make a considerable difference, a significant change indeed. There are many gear calculators available, I was thankful for that, not sure if you considered.

There is also this thread by Racecomp if you're wanting a 4.55 FD.
http://www.ft86club.com/forums/showthread.php?t=27647

humm

No options inside the tranny?