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GR86 General Topics General topics for the GR86 second-gen 86


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Old 01-13-2021, 06:57 PM   #253
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Some good info, LOTS of talking out his ass.
Care to share the good info and spare us his talking?
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Old 01-13-2021, 07:50 PM   #254
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Care to share the good info and spare us his talking?
TL;DR

He is using math to show that the "real wheel torque" in the BRZ is only about 20% less than the Ascent, despite the Ascent having 50% more torque, assuming you are in 2nd at 60 mph with 18" tires. Additionally, due to a much lower mass in the BRZ, the feel of acceleration in the BRZ will be closer to that of the Ascent despite having lower real wheel torque.
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Old 01-13-2021, 09:05 PM   #255
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TL;DR

He is using math to show that the "real wheel torque" in the BRZ is only about 20% less than the Ascent, despite the Ascent having 50% more torque, assuming you are in 2nd at 60 mph with 18" tires. Additionally, due to a much lower mass in the BRZ, the feel of acceleration in the BRZ will be closer to that of the Ascent despite having lower real wheel torque.
A fair summary, but a point being glossed over is that it is all theoretical. In theory, the brz/86 could be geared to match his numbers... but as far as I know, the transmission and final drive ratios of the second generation are unknown at present.

Not trying to detract from the video; just pointing out that there is a bit of speculation in the math that may not match up with the production car. It would be great if the car hit 60mph in second at redline - but that remains to be seen.
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Old 01-13-2021, 09:37 PM   #256
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Discuss . . .
Thank you - Was about to post this myself.
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Old 01-13-2021, 10:13 PM   #257
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A fair summary, but a point being glossed over is that it is all theoretical. In theory, the brz/86 could be geared to match his numbers... but as far as I know, the transmission and final drive ratios of the second generation are unknown at present.
It's going to have an acceleration advantage however they gear it. Will need 3.9 diff to hit 60 in 2nd gear, with that gearing it'll still walk the current-gen with 4.3.

Posted this a while back, here it is again, rear wheel torque for the current car with 4.3 diff in black, '22 with 4.3 in blue, 4.1 in red, and 3.9 in green, based on someone's very good (IMO) scaling of the '22's power curve from the dash display calibrated to official torque@rpm and power@rpm specs.

Either way it's gonna accelerate quicker overall. Again, with a 3.9 diff it'll hit 60 in 2nd gear. Personally I'd be happy with any of these ratios...
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Old 01-13-2021, 11:33 PM   #258
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Care to share the good info and spare us his talking?
Everything under "Why no turbo" and "Throttle Response"

Cost/Complexity - Ascent already has turbo. Is not complex. Nearly same MSRP. (Less than the cost of an aftermarket kit) All the parts are there already. Keep the compression the same if not drop it half a point and run a turbo.

Higher CG Because of bottom mount turbo. - Assumption 100%
Who is to say they couldn't mount it in front of the engine like so many kits do already. Even if they did bottom mount, I doubt the change would be drastic.

Weight gain - 100lbs??? What kind of giant ass turbo is he thinking of?
50-70 maybe, even at his overestimated 100 that is still minuscule in the big picture. Most of that weight could easily be offset by losing heated seats and stuff like that.

Throttle Response - Maybe with that big ass turbo he's thinking about.
But with a small responsive modern turbo all of those arguments don't hold up.

His engine/wtq analysis - Beside being assumption again and the arbitrary use of 60mph in 2nd gear.
There is zero reason the Ascent engine couldn't be made to rev to the same redline as the BRZ.
With those numbers made equal the BRZ makes 2,555 lb-ft, the difference is 20% in the other direction.
(Real numbers are closer to 18.5% for his numbers and 22.222222 for mine.)

Even if I drop the peak Tq down to a more reasonable 250 considering the high comp and reliability, the BRZ still has 12% more.
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Old 01-14-2021, 12:48 AM   #259
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That engine though. Where will it sit among the great 4cyl NA's?

The estimated 100lb weight gain isnít just the turbo. Intercooler, piping, oil supply, water cooling, etc. With the relatively shallow engine bay, there would be some re-engineering. Just because the aftermarket fits something under the hood, that doesnít mean an OEM can use the same placement. There are regulations about how a hood has to crumple in the event of a collision with a pedestrian. He did exaggerate a couple things, but I donít think heís completely off base.

If the business case were there, Subaru and Toyota engineers would have figured it out. There is just enough cost and just small enough volume that there wouldnít be a ROI, so those relatively minor hurdles are enough to derail a turbo BRZ/86.


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Old 01-14-2021, 07:02 AM   #260
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The estimated 100lb weight gain isnít just the turbo. Intercooler, piping, oil supply, water cooling, etc. With the relatively shallow engine bay, there would be some re-engineering. Just because the aftermarket fits something under the hood, that doesnít mean an OEM can use the same placement. There are regulations about how a hood has to crumple in the event of a collision with a pedestrian. He did exaggerate a couple things, but I donít think heís completely off base.

If the business case were there, Subaru and Toyota engineers would have figured it out. There is just enough cost and just small enough volume that there wouldnít be a ROI, so those relatively minor hurdles are enough to derail a turbo BRZ/86.


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I too am factoring in everything needed to turbo the car.
The turbo is usually the heaviest part next to the manifold.
Then manifold will almost certainly not be much of a difference between the turbo vs non turbo versions.

Spent an hour googling hood crumple zones and pedestrians.
Could not find anything to support that comment.
Even then, everything about that is well within the ability to engineer.
IF they had designed it like that in the first place.

The business/cost/ROI case is the only thing that I'd agree with.
Mainly for the part about the low volume thing.
But that isn't what was talked about in the video.

He insinuates that it would be too hard and expensive to do.'
That is just stupid going by the fact that this is a car made by large car companies and the MSRP of the Ascent.
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Old 01-14-2021, 07:23 AM   #261
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That engine though. Where will it sit among the great 4cyl NA's?

A friend, who was a powertrain engineer for Honda, told me the thing about crush zones.

Looking for an apples to apples comparison, I remembered that the Outback offered both the FB25 and the FA24DIT. In touring trim, the turbo version is 3937lbs. The N/A version is 3772lbs. Now, Iím sure the XT comes with a beefier transmission and some equipment differences, but it is getting an extra 165lbs from somewhere. It also might be an air to water intercooler which are heavier than air to air. Iím not sure.

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Old 01-14-2021, 09:15 AM   #262
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I thought the video was spot on. Jason only provided the comparative wheel torque/gearing/rpm calcs to make the point that the stock Ascent engine may not be THAT much faster than the 2022 BRZ engine given gearing that maximizes both torque curves. It served as a good mental exercise, nothing more.

But he made one comment that resonated with me. Referring to the WRX, “You get in that car, you give it 50% throttle and get 100% of the acceleration. You get full boost. That’s not what I asked for.” As someone who currently drives a turbocharged car, that is true and very irritating at times. As much as I’d like to be a racecar driver like many on this forum, I’m not and 98% of the time I drive at 50% throttle or less. Particularly with a MT, having a more precise power delivery is a huge plus for the NA 2.4 to me, even if it is slower than a turbo.
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Old 01-14-2021, 11:06 AM   #263
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I thought the video was spot on. Jason only provided the comparative wheel torque/gearing/rpm calcs to make the point that the stock Ascent engine may not be THAT much faster than the 2022 BRZ engine given gearing that maximizes both torque curves. It served as a good mental exercise, nothing more.
There's a neat shortcut to all the gearing/wheel torque/rpm calcs: power/weight. Pretty much does the same thing and gives a very good picture of relative acceleration performance.
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Old 01-14-2021, 12:35 PM   #264
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Pwr/Wt

Ascent 0.059 hp/Lb (lightest Ascent weighs 4430 per Subaru USA)
2022 BRZ 0.081 hp/Lb (Using Jason's whiteboard weight of 2815)
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Old 01-14-2021, 03:30 PM   #265
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That engine though. Where will it sit among the great 4cyl NA's?

My vote for one of the best 4 bangers of all time.....


The Toyota 22R/RE. Sure, it doesn't have a ton of horsepower, but it's literally a brick shit house. Had one in my 95 Toyota pick-up 4x4. That little truck ran forever and took plenty of abuse off road.


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Old 01-14-2021, 03:39 PM   #266
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Classic!
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