BRZ 2018 AT to MT gear ratio
 

Hey fellas,
My name is Stav and I am new here. So, I've got a 2018 BRZ AT (and not MT due to medical issues), and I really like it, though I wonder if I can somehow get the same gear ratios as the MT? The roads and tracks I usually go to require a little more acceleration, at minimum such as the MT, otherwise it really kills the momentum, and of course, more fun.. Is there a decent way of achieving this without throwing thousands of dollars?

Thank you and have a great new year!

Not an expert by any means, but you might be able to swap out the final drive to get better acceleration at the expense of lower top end.

Take a look at the threads of people that change the final gear (FD) to a 4.3, 4.5 or 4.7, something like this. That would be the easiest solution.

Exactly what others have said, get a 4.7-4.88 final drive installed and it's performance will surpass that of a stock manual

Do you have plans of going FI ever? Do you have any other mods?

I am not sure but in some countries the manual 2018 cars actually jave more power than the auto model about 5kw if the manuals have the red manifold.


An alternate way for better acceleration may be to get a tune and possibly catless header. Probably arround same price as buying and getting someonecto fit the different differential and you will actually have nore power and less torque dip arroind 4000

Not sure what FI means, but my car is stock. Maybe get a supercharger in a few years, right now not really though, gotta enjoy that car to the fullest first. Besides, I'd like to avoid warranty void mods such as ECU/engine power etc.

Do you know perhaps if changing the final gear will interfere with the ECU somehow, perhaps raise a flag or warnings? I don't mind not getting to 200 kmh and upward, no need for that tbh in Israel, even in the track.

F-orced I-nduction. Short for both superchargers & turbo.

Changing manifold/ header to decated one + remap will eliminate torque dip and will add about 15-20 hp (depending on tune and what you have for starters). This is definitely worthwhile and in the UK often the 1st (and probably most recommended) power mod.

For AT as many mentioned above FD is the way to go.

Both combined will make an AT GT86/ BRZ quite a lot more fun to drive (either on road or track).

I ended up going with turbo kit at the end, but certainly would recommend these 2 mods if you planning to keep your AT NA.

Not sure about warranty rules in Israel, but mids typically affect warranty only for modified components. Thus, re-map may affect engine warranty, but NA manifold + remap seem to be quite safe mod with good reliability track record.

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FI = supercharger or turbo charger. If planning on FI at some point I wouldn’t go above a 4.56, 4th will top out at 115mph and autos stop pulling in 5th. 4.56fd dropped .4sec off 0-60 even with having to shift into 3rd to hit 60.

Idk the warranty laws in Israel. But in the states nothing voids a warranty. They have to prove the modification caused or atleast contributed to the failure to not fix that particular issue.

Also they have no way of knowing you have ever flashed your ecu, you can flash back to stock before going in for warranty work. Same with putting back on stock header or any mod really.

As for the FD swap unless the work was inside the FD specifically, that should have no effect on warranty for anything else. They would also have no way of knowing unless they drove your car and knew what speeds each gear should be.

Some other mods to consider aerodynamics and weight reduction.
Take out trunk junk -30lbs
Rear seat delete mine only dropped 25lbs but has a lot more noise reduction then before
Lightweight battery, I got the largest shorai dropped another 25lbs
And a full exhaust about 20lbs for 100lbs total
Light weight rims/wheels expensive but rotational mass + better grip/handling
Wilwood BBK -32lbs unsprung
Can get to 150lbs reduction somewhat easy without ruining DD comforts.

Aero to reduce drag
Jdm underpanels
Verus tunnel cover
Verus diff cover / diffuser
Verus front wheel deflector
Side skirts

All these add up to make a pretty big difference. Less drag/weight means you need less power to accelerate.

Those aero panels are all in my wishlist but I've been hesitant to pull the trigger on them being skeptical on noticeable improvements considering total weight added.

Also suggest getting an aluminum driveshaft to save 12 pounds that is also not insignificant rotational driveline inertia reduction. I've done that, 4.56 FD, Wilwood BBK, trunk junk removal, and aftermarket wheels/tires and run E85 with the OFT tune and it is night and day compared to stock. More weight savings could be had by getting a lightweight water pump pulley, emptying the wiper fluid, and running with a low gas tank.

Drag reduction actually adds up and makes a big improvement. I wouldn’t do it as a first mod but once the low hanging fruit is picked it’s definitely worth it. Just look at modern supercars. Most have just a flat under panel from bumper to bumper. Underbody drag reduction is awesome because it lowers drag but also increases down force. Usually you have to sacrifice one for the other.

The JDM panels only add about 2.5lbs. Trans tunnel covers about 4lbs but in a major drag area. Also spread evenly across the lowest point of car.
I dont have the numbers off the top of my head but just from those I think the added weight breaks even from drag reduction at 25mph and then is essentially equavalent to 100lbs weight reduction at 100mph.

If that's true, that's good enough for me. Any links to the assessments to back it up?

The weight is a guesstimate from holding In hand. Could easily hold the far edge with just thumb/index and hold level/straight with no effort. Surprisingly light.

A lot of articles and formulas for calculating force required based on drag coefficient and frontal area. And you can find the cd reduction with some googling. JDM claims panels reduce cd by .01 , trans tunnel should be by another .0075 and wheel deflectors by .0025 or .02 total. Which is actually a lot of drag forces in lbs.

don’t have every link / article I read. But spent everyday researching and calculating things for a few weeks when I was on that “stage” of my build before purchasing, noticed a solid difference 60+mph especially 100+mph.

As speed doubles drag forces quadruple. 5lbs of drag at 20mph, is 20lbs at 40mph, 80lbs at 80mph, 320lbs at 160mph. Benefits add up a lot at higher speeds.