The 2nd gen BRZ will have similar performance to…?

[ZDan]

Originally Posted by Blighty

I think with high horsepower a lot of weight over the rear axle makes sense for handling, particularly for corner exit which is key.

But I'm not sure how FR cars with lower horsepower would benefit. I mean I'd assume for instance that MR cars would struggle to keep as efficient a line as a FR - wouldn't there be front grip limitations?

Genuinely would like to know.

Even low-hp FR cars benefit from more rearward weight distribution. It's not just about putting power down on corner exit, there are benefits under braking and cornering. It has to do with the nonlinear relationship between tire load and tire grip. As you load up a tire, it gives less and less additional grip/load.

Acceleration: obviously to maximize acceleration potential and drive out of corners with a rear-drive car, you want more load on the rear tires under maximum acceleration. More rearward = better. For rear-drive, 45F/55R is *better* than 50/50. For reference, a radically rearward static weight distribution of 18F/72R would put 100% of the weight of the car on the rear wheels at 1g acceleration for a 100" wheelbase car with 18" c.g. height (a bit extreme and you wouldn't want that).

Braking: with a "square" tire setup, you would maximize tire grip and minimize stopping distances if you had *even* load distribution between the tires under braking. At 1g braking, that would require a *very* rearward static weight distribution of about 32F/68R
For mid-engine cars with front/rear tire stagger, an even more rearward static distribution would be ideal for braking.

Cornering: Again assuming "square" tire setup, for maximum steady-state cornering grip (not accelerating or decelerating), you would want 50/50 F/R load distribution between the front/rear outside tires (for simplicity we'll leave front/rear roll stiffness out of it for now but it plays a big role). The FT86 has a decidedly front-biased 55/45 distribution, and this not only gives *ridic* front tire wear relative to rears at the track, it is also costing us lateral grip, cornering speed, and probably a couple/few *tenths* of a second in terms of lap time.
For cars with front/rear tire stagger, the "ideal" weight distribution for cornering would be more rearward than 50/50. This includes higher-powered FR cars that need wider rear tires.

Long/short, 50/50 isn't ideal for rear-drive performance. Even low-powered rear-drive cars would have better overall performance with weight distribution more rearward than 50/50. 55F/45R is a bit shite for an FR "sports" car IMO...

[Blighty]

Originally Posted by ZDan

Even low-hp FR cars benefit from more rearward weight distribution. It's not just about putting power down on corner exit, there are benefits under braking and cornering. It has to do with the nonlinear relationship between tire load and tire grip. As you load up a tire, it gives less and less additional grip/load.

Acceleration: obviously to maximize acceleration potential and drive out of corners with a rear-drive car, you want more load on the rear tires under maximum acceleration. More rearward = better. For rear-drive, 45F/55R is *better* than 50/50. For reference, a radically rearward static weight distribution of 18F/72R would put 100% of the weight of the car on the rear wheels at 1g acceleration for a 100" wheelbase car with 18" c.g. height (a bit extreme and you wouldn't want that).

Braking: with a "square" tire setup, you would maximize tire grip and minimize stopping distances if you had *even* load distribution between the tires under braking. At 1g braking, that would require a *very* rearward static weight distribution of about 32F/68R
For mid-engine cars with front/rear tire stagger, an even more rearward static distribution would be ideal for braking.

Cornering: Again assuming "square" tire setup, for maximum steady-state cornering grip (not accelerating or decelerating), you would want 50/50 F/R load distribution between the front/rear outside tires (for simplicity we'll leave front/rear roll stiffness out of it for now but it plays a big role). The FT86 has a decidedly front-biased 55/45 distribution, and this not only gives *ridic* front tire wear relative to rears at the track, it is also costing us lateral grip, cornering speed, and probably a couple/few *tenths* of a second in terms of lap time.
For cars with front/rear tire stagger, the "ideal" weight distribution for cornering would be more rearward than 50/50. This includes higher-powered FR cars that need wider rear tires.

Long/short, 50/50 isn't ideal for rear-drive performance. Even low-powered rear-drive cars would have better overall performance with weight distribution more rearward than 50/50. 55F/45R is a bit shite for an FR "sports" car IMO...

Well that was excellent. Thank you.

I would of thought with the front heavy car would allow you to apply small amounts of acceleration to balance your cornering speed a lot more efficiently than say a rear heavy car?

Also, isn't the GR86/BRZ 53:47?

[Blighty]

Originally Posted by Code Monkey

Assuming conservatively a 15% drivetrain loss, the 2nd gen should dyno at 238*.85 = 202 whp. If you can extract the same power per liter from the 2.4 as from the 2.0, the 2.4 should be rated at 246 hp or 209 whp. My suspicion is that 246 is too close to 2.0L Supra's 255 so the engine got detuned to 238. With a header I would not be surprised to see 220-230 whp, add flex fuel and get to 240 whp.

I think there is a problem with the size of the individual cylinders and the ability for an modern emissions compliant NA engine to fill them once the revs start getting high. There was an article where the guy who designs the engine (head of power unit) said in this new edition they had to use port injection at high speed to premix the fuel with the air because the air wasn't arriving fast enough to have enough time to mix in chamber (the 2l is pure DI at high revs).

That's not to say that if you couldn't throw money at the problem, like Porsche and their trick intake pressure wave timing on individual intakes and the probable exotic materials on cats and inside to make the pistons flow like butter.

Or just delete the cats that would certainly help the air suck through.

[ZDan]

Originally Posted by Blighty

Well that was excellent. Thank you.

I would of thought with the front heavy car would allow you to apply small amounts of acceleration to balance your cornering speed a lot more efficiently than say a rear heavy car?

Also, isn't the GR86/BRZ 53:47?

In the brief overview I totally separated braking, cornering, acceleration. In reality you'll have initial 100% braking followed by combined braking/cornering followed by combined cornering/acceleration. But the basic points are still valid. I.e. while trail-braking into a corner, you'll have more total combined braking and cornering grip with more rearward weight distribution than 50/50.

They advertised 53/47, but the mags tested them and found them to be 55/45, which is exactly what I found weighing my initially stock car at the track with a full tank and me in it. Now, with a 5 lb. battery (-25 lb.), 2-piece brake rotors (-12 lb.), near-empty washer reservoir (~-6 lb.) and a catless header (-10 lb.?), ~53 lb. off the nose of the car, my car is at 53.5F/46.5R with me in it, full tank. It was never anywhere near 53/47 stock...

[PulsarBeeerz]

Originally Posted by Code Monkey

Assuming conservatively a 15% drivetrain loss, the 2nd gen should dyno at 238*.85 = 202 whp. If you can extract the same power per liter from the 2.4 as from the 2.0, the 2.4 should be rated at 246 hp or 209 whp. My suspicion is that 246 is too close to 2.0L Supra's 255 so the engine got detuned to 238. With a header I would not be surprised to see 220-230 whp, add flex fuel and get to 240 whp.

The USDM cars will feature 228bhp not 238. As mention in the Ken Gushi ride along iirc, the new cars dyno around 195whp+. This is good given the 228hp rating which I'm sure was done on 91oct.

[OkieSnuffBox]

Originally Posted by PulsarBeeerz

The USDM cars will feature 228bhp not 238. As mention in the Ken Gushi ride along iirc, the new cars dyno around 195whp+. This is good given the 228hp rating which I'm sure was done on 91oct.

I'll be it was done on 93. I know my old Mustang (2013 GT) for example, was rated/advertised at 420hp. Then when you read the fine print in the manual it said 420 on 93, 410 on 91.

[Code Monkey]

My bad, 228*.85 = 194 whp.

[Dzmitry]

Not sure why we are comparing dyno's again... 206 whp on some dyno with a 100% chance of different conditions is not a good comparison to the ~195 whp that has been a number provided with no additional information whatsoever.

The most interesting information that could compare the two was CatDaddysBBQ's article which described his bolt-on and E85 tune on his first gen to feel "EXACTLY" the same as the new gen.

[OkieSnuffBox]

Originally Posted by Dzmitry

Not sure why we are comparing dyno's again... 206 whp on some dyno with a 100% chance of different conditions is not a good comparison to the ~195 whp that has been a number provided with no additional information whatsoever.

The most interesting information that could compare the two was CatDaddysBBQ's article which described his bolt-on and E85 tune on his first gen to feel "EXACTLY" the same as the new gen.

Ahhh yes, the old "butt dyno" is definitely superior.

[Dzmitry]

Originally Posted by OkieSnuffBox

Ahhh yes, the old "butt dyno" is definitely superior.

I was only referencing the only piece of information we have that is actually kind of useful. And it is absolutely superior to a couple dyno comparisons that we know absolutely nothing about further from peak whp numbers.

[dragoontwo]

Originally Posted by Dzmitry

I was only referencing the only piece of information we have that is actually kind of useful. And it is absolutely superior to a couple dyno comparisons that we know absolutely nothing about further from peak whp numbers.

What about trying to extrapolate a number from the 0-60 times published?

[Dzmitry]

Originally Posted by dragoontwo

What about trying to extrapolate a number from the 0-60 times published?

What's the point. We have HP/TQ numbers and graphs.

[OkieSnuffBox]

Originally Posted by Dzmitry

I was only referencing the only piece of information we have that is actually kind of useful. And it is absolutely superior to a couple dyno comparisons that we know absolutely nothing about further from peak whp numbers.

Sure thing.

How's your credit? I have a bridge for sale.

[drift86]

Originally Posted by ZDan

Long/short, 50/50 isn't ideal for rear-drive performance. Even low-powered rear-drive cars would have better overall performance with weight distribution more rearward than 50/50. 55F/45R is a bit shite for an FR "sports" car IMO...

I don't think it's a 'bit shite' at all. It all comes down to personal preference and I think the 55F/45R balance perfectly suits this type of car.

I've owned the 86, 50:50 FR and rear biased MR cars. They are all good for different situations. But for the low power level of the 86, I've never felt I needed more rear weight bias.

The front bias of the 86 provides a lot of predictability. It's very forgiving, allowing you to really overdrive the car and still be able to catch it in situations where you will have no chance in a rear biased car.

The twins are designed to be 'fun' cars rather than 'performance number' cars. There are many cars that will beat it if you are just looking at objective performance. But not many cars can beat it for feel and fun.