BRZ / FR-S Boxer Engine Dyno Powerband revealed

[serialk11r]

Well, if you use the drag equation with constant Cd, then it appears that the GTR has a huge excess of power right?
The tires can't be absorbing 100hp for sure. So you mentioned gearing...so is that to say gearing prevents it from reaching a higher top speed?

[Jordo!]

Very few cars can exceed the 200 mph mark. Other than power and gearing vs drag, there's just a ton of extra engineering that needs to go into making sure the whole car doesn't start tearing itself to pieces/doesn't lose traction/can actually come to a stop.

An unlimited GT-R could probably manage to make it to something approaching that number, depending on gearing -- I'm sure someone has top unlimited speed data somewhere on the internet.

[ZDan]

Originally Posted by serialk11r

So you mentioned gearing...so is that to say gearing prevents it from reaching a higher top speed?

It is at redline in top gear at 193mph.

[pkptd447]

Originally Posted by carbonBLUE

does anyone here think they can do an overlay of this graph


over this graph (size and strech it accordingly) so i can see how much better the fa20 is compared to a stock 2zz-ge

[serialk11r]

The BRZ graph is in kW not hp. 2ZZ is not more powerful.

[OrbitalEllipses]

^Yup. The HP peaks should be touching at least (that would be whp) or the BRZ should be higher.

[Ryephile]

After finding out that the USDM car will indeed have the 4.10:1 rear end ratio, I was curious how it worked out when mixed with the HKS DynoJet data. I tried my hand at Torque to the tire contact patch chart through all 6 gears, using a visually transferred power curve from the HKS video. The HKS video has been interesting as it markedly differs from the advertised power curve, falling off sharply at higher RPM. Does this represent final engine spec? Who knows 'til production models start hitting the dynos, but for now, here's my graph. I'm using 844 rev/mi for tire rolling circumference, FWIW.

Notice that for peak acceleration, you'll need to:
hit redline [7450 RPM] in 1st
upshift at 7250 in 2nd
7K upshifts in 3rd and 4th
final upshift at 7250 from 5th into 6th [at 130 MPH, mind you]

This is strange for a gasoline production car, to have to upshift prior to redline to get peak accelerative force. Hopefully the production car will breathe a bit better at the top end of the RPM band. Note this was taken from the "wheel HP" data, so drivetrain losses are already approximately accounted for. The only thing missing is aero drag implementation, something Deslock already impressively did in his previous charts.

[serialk11r]

So when you account for aero the higher the speed, the more drag, so the lower the acceleration, so each of those lines starts to go down a little, and the shift points move up a bit, but on Deslock's chart there is still the shift before redline phenomenon.

I guess the weird drop off >7000rpm is something that can only be explained when the cars start arriving.

[Deslock]

Originally Posted by Ryephile

The HKS video has been interesting as it markedly differs from the advertised power curve, falling off sharply at higher RPM. Does this represent final engine spec?

Doubtful. For your plot, you used one of the early guesses for scale of the the screencap. I used the same scale for the plot titled "2004 WRX and BRZ (unrealistically optimistic) Estimated Acceleration vs Speed" (in post 175).

I threw that plot out because it shows the car making its peak power too early, and working backwards the engine would need to make 167-171 lbf*ft for 4500-6300 RPM. So either that's not the right scale, or the dyno is from early testing, or this engine is way under-rated. I wouldn't count on the last one, and I only included that plot in my post to illustrate why that guess for the scale appears to be wrong.

Originally Posted by Ryephile

This is strange for a gasoline production car, to have to upshift prior to redline to get peak accelerative force.

It's likely just the wrong scale. Try plotting again with the scale shown in the revised first post in that thread (where peak power is actually at 7k) and you'll get more reasonable results (like my "conservative dyno" plots).

Though it's still not quite right... we won't know exactly what the story is until we see some properly labeled dynos.

Originally Posted by serialk11r

So when you account for aero the higher the speed, the more drag, so the lower the acceleration, so each of those lines starts to go down a little, and the shift points move up a bit, but on Deslock's chart there is still the shift before redline phenomenon.

I guess the weird drop off >7000rpm is something that can only be explained when the cars start arriving.

The shift points don't change due to drag. You upshift when you put down less power in the lower gear than you will in the higher gear. The only plot of mine that shows shifting before 7450 is the one I discarded, for the reasons mentioned above (all my other plots show the car being shifted at redline).

[serialk11r]

Sorry, brain fart you're right Deslock.

[Ryephile]

Originally Posted by Deslock

It's likely just the wrong scale. Try plotting again with the scale shown in the revised first post in that thread (where peak power is actually at 7k) and you'll get more reasonable results (like my "conservative dyno" plots).

Though it's still not quite right... we won't know exactly what the story is until we see some properly labeled dynos.

Thanks for the insight. Indeed, something isn't right. The HKS dyno doesn't come close to matching the advertised engine power graph, even with the alternate 8500 RPM scaling. It ends up missing a whole bunch of low RPM torque, with an improbable torque slope below 3k RPM that wouldn't be caught dead in any recent-times OEM engine.

Indeed, we'll have to wait and see what the real production engine puts out.

[Dimman]

Originally Posted by Ryephile

Thanks for the insight. Indeed, something isn't right. The HKS dyno doesn't come close to matching the advertised engine power graph, even with the alternate 8500 RPM scaling. It ends up missing a whole bunch of low RPM torque, with an improbable torque slope below 3k RPM that wouldn't be caught dead in any recent-times OEM engine.

Indeed, we'll have to wait and see what the real production engine puts out.

The conspiracy of the missing torque continues... Heh...

[serialk11r]

The missing torque below 3k is hardly a surprise. The cam has to have enough duration for good power at 7k The 2GR-FSE has no variable duration, so it has a similar drop (or shall I say nosedive) before 2k. Torque at these ranges is limited by VE, which is limited by the amount of cam advance which is limited by internal EGR.

[Draco-REX]

I want someone to hook up an ODB scanner and log the throttle plate and either confirm or debunk the rumor that the high rpm torque dropoff is Subaru closing the throttle to reduce stress on the engine.