GR86/BRZ Track Comparison (Japanese)

[Jianlun]

Lots of close ups and info. But Japanese....

[Jianlun]

Originally Posted by Kona61

Yea it definitely is steel. That's interesting! It sounds like it's stiffer though? Regardless, it's not that difficult to change, and the 86 is supposedly faster on track.

You Tube auto-translate started working for some of the earlier videos, esp the Lovecars one. so i rewatched and gathered the following tidbits of info:
1. GR more playful, slides earlier, harder to hold a drift (we kinda already know this from press material)
2. GR has cast iron front knuckles/uprights to BRZ aluminium ones
3. GR MT throttle mapping more aggressive, BRZ MT more linear. GR AT and BRZ AT about same.
4. GR mounts rear swaybars to subframe, BRZ mounts them direct to chassis.
5. GR softer fronts, harder rears that BRZ.
6. GR smaller front swaybars and larger rear ones, than BRZ.


I am so getting the GR! (and changing out the front knuckles/uprights)

[Jianlun]

Some more translatable tech information.

[Sport-Tech]

Originally Posted by Jianlun

Drift King timings!
GR86 MT 1min 19.54
BRZ MT 1min 20.10
GR86 AT 1min 20.59
BRZ AT 1min 20.71

Compared to Noblesse (I assume same conditions):
GR86 AT 1min 22.09
GR86 MT 1min 22.78
BRZ AT 1min 23.14
BRZ MT 1min 23.14

If these MT-AT lap time differences for the new twins prove to be consistent, either the AT cars have less power and/or torque, or nothing at all has been done to improve the AT over the first gen. In either case, it's bad news for the AT buyer. There is just no excuse for the AT versions to be significantly slower on track in 2021. The negative effects of the extra weight of the AT cars should be more than offset by their more rapid shifting.

[nextcar]

Originally Posted by Kona61

Yea it definitely is steel. That's interesting! It sounds like it's stiffer though? Regardless, it's not that difficult to change, and the 86 is supposedly faster on track.

But why would you want to? Both steel and aluminum seem to offer advantages- unclear to me which would be better for me. Along with all the other differences (sway bars, dampeners, etc) I am sure I will have a preference between the cars, but I have no idea if I would want to swap this part.

[Kona61]

Originally Posted by nextcar

But why would you want to? Both steel and aluminum seem to offer advantages- unclear to me which would be better for me. Along with all the other differences (sway bars, dampeners, etc) I am sure I will have a preference between the cars, but I have no idea if I would want to swap this part.

Just the assumption for serious track rats, that the aluminum knuckle will reduce unsprung weight significantly.

[Jianlun]

Steel is almost 2.5x density of aluminum. The GR upright/knuckle doesn't look 2.5x less volume/material, so it definately is heavier. And i am a sucker for anything lightweight. For sure cheaper per kg to change these to alu than to get the lightest (read: mag watanabes yum yum) wheels. Wonder what's the reason, cost? Wonder if stiffness is really that significantly different and whether that makes a diff. But yeah, GR still is faster, wonder why. But then again, it's less than half a second faster. Splitting hairs haha.

[revaholic]

Alright so there seems to be some distinct mechanical differences between GR86 and BRZ


This is what I can understand from this vid but even if you don't they compare the two directly with a car cross section. Sorry if I'm not using the right terms:


Front suspension knuckle - BRZ is aluminium, GR86 is iron
Front stabilizer bar - BRZ is 18.0mm hollow, GR86 is 18.3mm solid
Rear stabilizer - BRZ is 14mm solid but has an additional stabilizer bar, GR86 is 15mm solid.

[Jianlun]

Originally Posted by revaholic

Alright so there seems to be some distinct mechanical differences between GR86 and BRZ


This is what I can understand from this vid but even if you don't they compare the two directly with a car cross section. Sorry if I'm not using the right terms:


Front suspension knuckle - BRZ is aluminium, GR86 is iron
Front stabilizer bar - BRZ is 18.0mm hollow, GR86 is 18.3mm solid
Rear stabilizer - BRZ is 14mm solid but has an additional stabilizer bar, GR86 is 15mm solid.

Also the parts about BRZ having the swaybars mounts to the chassis whereas in the GR the swaybar mounts are to the subframe. Also BRZ having that additional brace across the trailing subframe mounts.

Forgot if it was this vid but there was one where a GR staff was explaining about the rear trailing arm bushing having some compliance for toe out during compression (ie when loading up or squating). Not sure if there is difference in compliance of this bushing between the twins.

And also there seem to be some difference between the twins' rear diff mount. But didnt come across anyone explaining anything on that.

Oh and the new 2.4L pistons have proper boxed bridged now! Yummy!

[Kona61]

Originally Posted by Jianlun

Also the parts about BRZ having the swaybars mounts to the chassis whereas in the GR the swaybar mounts are to the subframe. Also BRZ having that additional brace across the trailing subframe mounts.

Forgot if it was this vid but there was one where a GR staff was explaining about the rear trailing arm bushing having some compliance for toe out during compression (ie when loading up or squating). Not sure if there is difference in compliance of this bushing between the twins.

And also there seem to be some difference between the twins' rear diff mount. But didnt come across anyone explaining anything on that.

Oh and the new 2.4L pistons have proper boxed bridged now! Yummy!

I'm not so concerned about the pistons, I'm curious about the rods. They aren't offset any more, and they look bigger both thicker laterally and longitudinally, but I could be mistaken. Definitely has a bigger rod bearing on the bottom end.


Also, the more I watch these videos, the more I want to buy one. I really, really miss driving stick. I also miss the feeling of N/A.

[Jianlun]

Use Google translate.


https://car.watch.impress.co.jp/docs...n/1338876.html


Omg omg more tidbits! Notable mentions that I didn't catch previously (correct me if I am wrong cos it's kinda interpreting from Google Translate results):
1. The brz alu front upright is 1.5kg lighter per corner than the GR cast iron piece. But GR say cast iron more responsive (go figure... or they use cast iron cos aftmkt gonna change to billet anyway hahah).
2. Slight offset seating position ie steering wheel not aligned to driver, now that the driver and front passenger are placed 7.4mm closer together (to centralise the mass).
3. Brz front swaybar is 18.3mm and hollow. GR is 18mm and solid.
4. Rear trailing arm bushing for GR is more compliant. Brz uses stiffer ones cos Subaru do not like geometry change.
5. Rear subframe stiffness up 70%. Together with the
+60% front axle and +50% torsional rigidity that we see in press kits.
6. Pistons are 56g heavier due to 94mm vs 86mm diameter. Con rod now split horizontally cos they found the diagonal split has some oil lubrication problems.
7. Fuel starvation problem cured by a bigger lifter pump on right saddle tank and bigger lines.
8. Carbon synchros in 4th gear and some detail changes in the shifter for better shifting across gates.
9. The author (who races brz 86) says torque dip is gone, steering is more responsive. With 86 sharper/agile/busy and brz more stable.
10. And yes. There is artifical.sound.... I quote the article below (via Google translate)

"It is the existence of active sound control that supports it. This system, which lets you hear the power of the middle rotation range of 200Hz to 400Hz and the power of high rotation of 600Hz or more from the speaker after removing the miscellaneous taste, is a beat that seems to be a rotary engine, although the manufacturer is different It's interesting because it develops a sound that works."




Anyway the author/master-at-work:

https://car.watch.impress.co.jp/docs/news/1338901.html
Same author's review of the GR86 one make series prototype vehicle.

[Dzmitry]

Originally Posted by Jianlun

6. Pistons are 56g heavier due to 94mm vs 86mm diameter. Con rod now split horizontally cos they found the diagonal split has some oil lubrication problems.
7. Fuel starvation problem cured by a bigger lifter pump on right saddle tank and bigger lines.

I am actually growing interest in these types of subjects. Particularly how or if the oiling has been improved in the car, and it seems to be good news that fuel starvation is taken care of.

[Yoshoobaroo]

Originally Posted by revaholic

Front suspension knuckle - BRZ is aluminium, GR86 is iron

Another factor may be durability too. Much easier for a tech to mangle an aluminum knuckle than an iron one. Had a mechanic I trusted on my BMWs absolutely wreck a front knuckle trying to get a ball joint out. I don't go to him anymore.

Originally Posted by Jianlun

~ BRZ having that additional brace across the trailing subframe mounts.

Forgot if it was this vid but there was one where a GR staff was explaining about the rear trailing arm bushing having some compliance for toe out during compression (ie when loading up or squating). Not sure if there is difference in compliance of this bushing between the twins.

The Supra does this too. Explains why it’s harder to hold a slide on the GR. Most people don’t like it on the Supra. It makes initiation of the slide very easy but it does make it more unpredictable.

[ZDan]

Originally Posted by Jianlun

4. Rear trailing arm bushing for GR is more compliant. Brz uses stiffer ones cos Subaru do not like geometry change.

Neither do I!
I don't know why they never learn this lesson, Japanese sportscar makers have often tried to have rear toe change (one way or the other) with bump and/or with lateral loading, and it has *never* worked out. 2nd gen FC RX-7, earlier 1st-gen NSX, early 2nd gen MR-2, AP1 S2000, Nissan HICAS rear-wheel-steering. C'mon, leave it alone! The best rear suspension setup in my opinion is to have as nearly ZERO toe change with lateral loading and with suspension compression as possible. Keeps the handling linear when pushing it hard near and over the limits of grip.

Hard to believe Toyota is still making this mistake of being "clever" with rear toe change under dynamic conditions. Frankly, I think it's stupid, gimmicky, and counterproductive.