My BRZ is Alive!! Upgraded Final Drive

[nikitopo]

Originally Posted by bfrank1972

There's another thread on here somewhere where I discuss it in a bit more detail, and posted a spreadsheet that shows everything in basic mathematics.

I still remember this excel. It was a good work.


http://www.ft86club.com/forums/showp...1&postcount=40

[KoolBRZ]

Originally Posted by bfrank1972

Yup, in gear acceleration will be harder, but shorter. As soon as the lower geared car shifts it loses it's advantage over the longer geared car (assuming both are in the upper power band). There's another thread on here somewhere where I discuss it in a bit more detail, and posted a spreadsheet that shows everything in basic mathematics. No doubt a lower FD makes the car FEEL more fun to drive though

What you fail to consider, is the effect in an AT car. The longer it is in a gear, the slower the acceleration is. With under 200 hp, AT cars just don't have the power to accelerate at anything close to the rate the MT cars do. An AT car would have to have a FD of 5.404 to match the 6th gear of a MT. A 4.88 FD upgrade is ideal for AT's to bring the acceleration back up, but only close to MT acceleration. Mileage only suffers because of how much more exciting it is to drive in the city. Highway mileage is almost the same. So, to conclude, I recommend a 4.88 FD as an upgrade to an AT car, I don't recommend it for MT cars unless you need a certain gear for a certain stretch of track, And then I might recommend a 4.44, 4.30, 4.55, or even a 5.29.

[bfrank1972]

Originally Posted by KoolBRZ

What you fail to consider, is the effect in an AT car. The longer it is in a gear, the slower the acceleration is. With under 200 hp, AT cars just don't have the power to accelerate at anything close to the rate the MT cars do. An AT car would have to have a FD of 5.404 to match the 6th gear of a MT. A 4.88 FD upgrade is ideal for AT's to bring the acceleration back up, but only close to MT acceleration. Mileage only suffers because of how much more exciting it is to drive in the city. Highway mileage is almost the same. So, to conclude, I recommend a 4.88 FD as an upgrade to an AT car, I don't recommend it for MT cars unless you need a certain gear for a certain stretch of track, And then I might recommend a 4.44, 4.30, 4.55, or even a 5.29.

Nah same basic concepts, just longer gears. AT is inherently parasitic. Longer gears also feel slower. AT *will* benefit more from lower rpm as lower rear FD will get it from idle to the upper power band quicker - that's a REAL benefit. Once there however your actual advantage virtually disappears (though in gear acceleration feels faster). Counterintuitive I know, but read thru this thread, did some simple calcs to illustrate what I'm getting at;

Final Drive: 4.56 vs. 4.88
http://www.ft86club.com/forums/showthread.php?t=98677




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[Toyota86.ir]

Originally Posted by KoolBRZ

What you fail to consider, is the effect in an AT car. The longer it is in a gear, the slower the acceleration is. With under 200 hp, AT cars just don't have the power to accelerate at anything close to the rate the MT cars do. An AT car would have to have a FD of 5.404 to match the 6th gear of a MT. A 4.88 FD upgrade is ideal for AT's to bring the acceleration back up, but only close to MT acceleration. Mileage only suffers because of how much more exciting it is to drive in the city. Highway mileage is almost the same. So, to conclude, I recommend a 4.88 FD as an upgrade to an AT car, I don't recommend it for MT cars unless you need a certain gear for a certain stretch of track, And then I might recommend a 4.44, 4.30, 4.55, or even a 5.29.

I use AT GT86 with FD 4.88
it is good in 1 2 3 but gear 4 and 5 are not good. FD 5.3 or 5.7 make 4 a-little better but they are not good for gear 1 and 2 and i think FD 4.88 is ideal for AT and if we want to have better performance we should buy MT because it's gearbox ratios are ideal.

GT86 AT gear ratio are not similar to a sport car.

[SUB-FT86]

Originally Posted by bfrank1972

Nah same basic concepts, just longer gears. AT is inherently parasitic. Longer gears also feel slower. AT *will* benefit more from lower rpm as lower rear FD will get it from idle to the upper power band quicker - that's a REAL benefit. Once there however your actual advantage virtually disappears (though in gear acceleration feels faster). Counterintuitive I know, but read thru this thread, did some simple calcs to illustrate what I'm getting at;

Final Drive: 4.56 vs. 4.88
http://www.ft86club.com/forums/showthread.php?t=98677




Sent from my iPhone using Tapatalk

Typically when a automatic car is geared more aggressively in comparison to its manual counterpart it is either quicker or the same regardless of parasitic loss of the auto transmission. The 370Z is a good reference. The Auto makes 265whp while the manual makes 280whp but the auto is a monster in gearing and it posted the quickest 1/4 mile I have seen for a Z 13.1 or 13.2 in C&D

[SUB-FT86]

Originally Posted by Toyota86.ir

I use AT GT86 with FD 4.88
it is good in 1 2 3 but gear 4 and 5 are not good. FD 5.3 or 5.7 make 4 a-little better but they are not good for gear 1 and 2 and i think FD 4.88 is ideal for AT and if we want to have better performance we should buy MT because it's gearbox ratios are ideal.

GT86 AT gear ratio are not similar to a sport car.

How do you know 5.29 is not good for 1 and 2? I would think if you had some sticky and wider rubber it would fix the problem. You can make a auto faster than a manual but it would only be until 100-103 mph. All you have to do is make sure the first 4 gears are much shorter than the manuals. If you think I'm bs-ing look at the ratios of a 370Z auto and manual. The first 4 7AT ratios make the auto Z faster until 126 mph. Now I don't care for speeds above 100 as I don't track my car or drag race but it seems like all you need is a 5.1 or 5.29 in a auto to be perfect.


Manual with 4.1 FD

1st gear. 14.87 36mph
2nd gear. 8.97 60mph
3rd gear. 6.31 86mph
4th gear. 4.97 109mph

Auto with 5.29

1st gear. 18.72 30mph
2nd gear. 10.90 51mph
3rd gear. 7.43 73mph
4th gear. 5.29 104mph

Auto with 5.1

1st gear. 18.04 31mph
2nd gear. 10.51 53mph
3rd gear. 7.16 77mph
4th gear. 5.1 108mph

A manual does 0-60 in 6.3 and 0-100 in 16.5 while the auto stock is 7.5-7.7 to 60 and 20.1 seconds to 100. The biggest change to 100 can only happen with a Auto and a 5.1 or 5.29 FD. A manual with a greater FD might have issues to 100 in less than 16.5 if it requires a 5th shift to 100.

So the Manual will get to 36 quicker while the Auto gets to 30-31 quicker
The auto will get to 51 to 53 quicker while the manual will get to 60 possibly quicker by a few tenths
The auto will get to 73 to 77 mph quicker while the manual gets to 86 quicker
The auto will reach 104-108 quicker while the manual reaches above 109 quicker.

Safe to say the auto is capable of 0-100 in 15.5 to 16.2 seconds with a 5.1 or 5.29 FD which is a 4-4.5 second better time than a auto 4.1 to 100 mph. Now above that I couldn't care less.

[bfrank1972]

Originally Posted by SUB-FT86

Typically when a automatic car is geared more aggressively in comparison to its manual counterpart it is either quicker or the same regardless of parasitic loss of the auto transmission. The 370Z is a good reference. The Auto makes 265whp while the manual makes 280whp but the auto is a monster in gearing and it posted the quickest 1/4 mile I have seen for a Z 13.1 or 13.2 in C&D

Agreed - was just illustrating the other poster's quote of how the AT is slow, it's partially the parasitic loss of the transmission. The other factors include gear spacing (manual transmission gear spacing is better, and it matters on our tiny motors), which impacts actual acceleration. The FD is the least of those factors - though a lower FD would definitely make a real difference when starting at low RPM's, just much less so once both cars are in the power band.

Someone else on this thread made a good point - say your max speed is 100mph, and you don't care about going over that speed. Lower your FD so at the top of 3rd gear you're going 100mph, then you're optimizing your FD to maximize it's advantage over OEM gearing at 100mph and it will be faster to 100mph every time. In this way, a lower FD will make a big difference - but eventually the OEM geared car will start to gain ground again.

There are many factors that influence how FD impacts acceleration of a car. Wind drag for instance - if you look at those calculations I did, they are made 'in a vaccuum', and the higher geared car catches up in every gear eventually. In the real world, say the lower geared car reaches 100mph and then shifts. It's at this point the lower geared car has its greatest 'advantage', and it's also the point where the higher geared car starts slowly closing the gap... but it's also where both cars are starting to fight significant amounts of wind force. So the higher geared car will have an uphill battle when trying to close the gap - this is one of the reasons why a car with a lower FD has small but tangible actual advantages overall, while mathematically speaking there is no advantage once in the optimal power band.

As I mentioned in the other thread - I'm seriously thinking of upgrading the FD in my car as well. Not looking for huge advantages over a stock car, but will just make it feel more energetic to drive. Perception of speed and actual speed are many times quite different

[Toyota86.ir]

I say fd 5.3 for AT is not good not for spining gear 1
Because driving feeling with gear 1 is alittle aggressive with fd 5.3 and 5.7 and i do not like fd 5.3 because gear 4 & 5 of AT is so long and it kill acceleration. Going to 5.3 will bring gear 4 at 116km/h.
I have no problem with higher FD if we do for MT car because gear 4 & 5 in MT are so shorter than AT

[churchx]

MT has advantage of having option of not just FD, bet also close ratio gear set, that make 1&2 more usable. Most probably there will never be such option for AT, at least at reasonable prices.

[dem00n]

Originally Posted by FRSBRZGT86FAN

you wouldn't happen to know anyone in NJ or PA that is reputable enough to do a quality final drive upgrade would you?

Hit up AZP Installs.

[SUB-FT86]

It's funny but when I look at the gearing for a GTI and 370Z the automatic counterparts gearing is also wider spaced in comparison to the manual version yet the manual version still gets there ass kicked in overall acceleration. Think I'm joking? Look it up, the auto versions just have a better gear + FD multiplication in the first four gears at least.

[KoolBRZ]

OK, I think we can agree that a FD won't increase the horsepower of the engine. It will increase the power to the tire however. Allow me to prove it to you. Two cars one an FRS, and one a BRZ both with stock engines. The FRS has stock manual gearing and a 4.10 FD. The BRZ has stock manual gearing and a 4.88 FD. At 60MPH the FRS engine is spinning at 2575 rpms, while at 60MPH the BRZ engine is spinning at 3065 rpms. Both engines have the same horsepower, but the power to the wheels is different. The FRS has 7295.83/PI*R2 horsepower per minute, but the BRZ has 8684.17/PI*R2 horsepower per minute.

[SUB-FT86]

I used to own a G35 coupe with the crappy auto gear ratios and 0-60 was 6.8 seconds and the manuals were 5.6-5.7 with better ratios but the same engine. Then Nissan made the G37 7AT more aggressive as far as gear torque for each gear and now the auto is .2-.3 seconds quicker. Gearing affects the same car with the crappier gearbox ratios(AT) much better than it would the one with better ratios. Even a couple guys on here knocked off 1 second off their 0-60 time with just the 4.88 by itself. I also saw a video of a guy using e85, headers and 4.88 running a 5.9 seconds for a Auto. That is a 1.7-1.8 second reduction and I know that can't be just e85 and headers.


[ame="https://www.youtube.com/watch?v=XuXT5n-ds4A"]0-60 mph BRZ - YouTube[/ame]

This auto acts more like a DCT!

[bfrank1972]

Originally Posted by KoolBRZ

OK, I think we can agree that a FD won't increase the horsepower of the engine. It will increase the power to the tire however. Allow me to prove it to you. Two cars one an FRS, and one a BRZ both with stock engines. The FRS has stock manual gearing and a 4.10 FD. The BRZ has stock manual gearing and a 4.88 FD. At 60MPH the FRS engine is spinning at 2575 rpms, while at 60MPH the BRZ engine is spinning at 3065 rpms. Both engines have the same horsepower, but the power to the wheels is different. The FRS has 7295.83/PI*R2 horsepower per minute, but the BRZ has 8684.17/PI*R2 horsepower per minute.

Hi, Just read that other thread where I did that spreadsheet - look at the calcs and it will show you. What you're talking about is torque multiplication. Power is not increased at the wheels, torque is multiplied, and at the same time, RPM of the wheel is divided. It's why we even bother to rate things in both HP and TQ. HP is RPM dependent.

Regarding the other post regarding AT with wider gear spacing being faster than narrower gearing on a MT equivalent, that's entirely believable if the car has a broad torque curve. You see the same thing with Camaros, Corvettes, etc. You need close gearing to optimize a narrower power band, 370z's and GTI's likely don't have that issue. Not sure about the Nissan, but pretty sure the VW is dual clutch too which avoids the losses associated with "slush boxes" (I think I'm dating myself with that comment!) in these cases your shift times are often better than your typical MT driver, and you probably have some sort of launch control. Yay computers!


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