BRZ / FR-S Boxer Engine Dyno Powerband revealed

[OrbitalEllipses]

Originally Posted by 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.

And that is why I will always prefer a throttle cable.

[Ryephile]

Originally Posted by Dimman

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

LOL, yes it appears it does.

For the time being, I'm going to make a blanket assumption that the HKS dyno data is unrepresentative of the production engine. Who knows what random yet-fine-tuned parts they had already slapped on the car...or how they were able to induce two separate RPM redlines?

I know Subaru/Toyota don't have to have the engine SAE certified, but it would be very shameful if they didn't....and Japanese aren't very willing to accept such public shame. Considering both Scion and Subaru are advertising 200HP in the US market, I'm willing to bet the engine makes no less than 201HP peak on a poorly broken-in engine [i.e. BMW-style break-in], and upwards of 220HP on a properly broken-in engine. These days, having an engine that doesn't average more than the SAE rating just doesn't cut the mustard. Just for the record, however, I can't substantiate this other than basing it on the current state of the industry.

[Bristecom]

Originally Posted by serialk11r

On bobistheoilguy it said that ALL oils are too thick at startup, the thinnest synthetic bases are like 70cS at room temperature or something, while at operating temperature it goes down to single digits cS (the correct viscosity), which is why you don't rev a cold engine, because the cold oil doesn't flow well. Since the oil pump is positive displacement I take this to mean that the oil doesn't penetrate the bearings or something like that.

At the dealer I used to work at, people would rev engines to redline as soon as they started them. I cringed every time. I hope to gawd nobody will have done that to the FR-S I buy.

[Dimman]

Playing around with a gearing spreadsheet and eye-balling a couple of the dyno screens I noticed a couple things about the dip/flat-spot. First thing, is in performance all-out redline shifting, it has basically no effect. The rpm drop from the upshifts at 7400+ rpm always (well almost, 2nd starts just a wee bit from the flat area) put the next gear's rpm in the upper super-flat torque area. I calculated the following;
1-2 @ ~4500
2-3 @ ~5200
3-4 @ ~5800
4-5 @ ~6100
5-6 @ ~5700

@ 4500 rpm the dip is starting its rise and is probably ~90%+ of peak. So shifting at redline we will probably (based on the dyno graph accuracy) ALWAYS have at LEAST 90% (95%?) of max torque AVAILABLE ALL THE TIME.

The second thing is what the dip may be like while putting around town. Given the curve, based on feeling the torque taper down for the dip it may encourage short shifting at ~ 3600 rpm which puts the next gear just on the other side of the low rpm peak (which looks very close to the 151 total peak). So it will probably feel pretty strong even taking it easy. Maybe a minimum of 80% of peak available in this operating range.

Only places I could see the dip being noticed are on the highway and trying to accelerate from cruising to passing without downshifting, and light aggressive (no wheelspin) launch in first gear only (like taking off gently then punching it).

Lastly with the power, torque and rev limit shifted up ~ 800 rpm, plus a ~5% torque increase in the upper range (5k+), and a 4.3:1 rear end (Mk3 NA Supra, if the guts are interchangeable), this car would run with an out-going model GenCoupe V6. This may be just headers, intake, exhaust and a re-flash. But would probably kill the nice putting around town effect.

Other thoughts? Corrections?

[carbonBLUE]

Originally Posted by Dimman

Playing around with a gearing spreadsheet and eye-balling a couple of the dyno screens I noticed a couple things about the dip/flat-spot. First thing, is in performance all-out redline shifting, it has basically no effect. The rpm drop from the upshifts at 7400+ rpm always (well almost, 2nd starts just a wee bit from the flat area) put the next gear's rpm in the upper super-flat torque area. I calculated the following;
1-2 @ ~4500
2-3 @ ~5200
3-4 @ ~5800
4-5 @ ~6100
5-6 @ ~5700

@ 4500 rpm the dip is starting its rise and is probably ~90%+ of peak. So shifting at redline we will probably (based on the dyno graph accuracy) ALWAYS have at LEAST 90% (95%?) of max torque AVAILABLE ALL THE TIME.

The second thing is what the dip may be like while putting around town. Given the curve, based on feeling the torque taper down for the dip it may encourage short shifting at ~ 3600 rpm which puts the next gear just on the other side of the low rpm peak (which looks very close to the 151 total peak). So it will probably feel pretty strong even taking it easy. Maybe a minimum of 80% of peak available in this operating range.

Only places I could see the dip being noticed are on the highway and trying to accelerate from cruising to passing without downshifting, and light aggressive (no wheelspin) launch in first gear only (like taking off gently then punching it).

Lastly with the power, torque and rev limit shifted up ~ 800 rpm, plus a ~5% torque increase in the upper range (5k+), and a 4.3:1 rear end (Mk3 NA Supra, if the guts are interchangeable), this car would run with an out-going model GenCoupe V6. This may be just headers, intake, exhaust and a re-flash. But would probably kill the nice putting around town effect.

Other thoughts? Corrections?

ive done the calculations and for a 86 to have the same power to weight as a 3.7 v6 mustang you would need 200 whp prob 205-210 to be at the v6 gencoupe power to weight

intake, headers, exhaust should add the 20 whp you would need to be that fast in a straight line, but we would leave them around the corners with out a doubt

[Levi]

Originally Posted by Dimman

Playing around with a gearing spreadsheet and eye-balling a couple of the dyno screens I noticed a couple things about the dip/flat-spot. First thing, is in performance all-out redline shifting, it has basically no effect. The rpm drop from the upshifts at 7400+ rpm always (well almost, 2nd starts just a wee bit from the flat area) put the next gear's rpm in the upper super-flat torque area. I calculated the following;
1-2 @ ~4500
2-3 @ ~5200
3-4 @ ~5800
4-5 @ ~6100
5-6 @ ~5700

@ 4500 rpm the dip is starting its rise and is probably ~90%+ of peak. So shifting at redline we will probably (based on the dyno graph accuracy) ALWAYS have at LEAST 90% (95%?) of max torque AVAILABLE ALL THE TIME.

The second thing is what the dip may be like while putting around town. Given the curve, based on feeling the torque taper down for the dip it may encourage short shifting at ~ 3600 rpm which puts the next gear just on the other side of the low rpm peak (which looks very close to the 151 total peak). So it will probably feel pretty strong even taking it easy. Maybe a minimum of 80% of peak available in this operating range.

Only places I could see the dip being noticed are on the highway and trying to accelerate from cruising to passing without downshifting, and light aggressive (no wheelspin) launch in first gear only (like taking off gently then punching it).

Lastly with the power, torque and rev limit shifted up ~ 800 rpm, plus a ~5% torque increase in the upper range (5k+), and a 4.3:1 rear end (Mk3 NA Supra, if the guts are interchangeable), this car would run with an out-going model GenCoupe V6. This may be just headers, intake, exhaust and a re-flash. But would probably kill the nice putting around town effect.

Other thoughts? Corrections?

When I head from the review about this dip, and then it got confirmed by the dyno graph, I made excactly the same interpretation as you. And in fact the dip does not hurt unless you drive the car as if it was turbocharged. When I drive normally in my car which has a similar torque curve, with the dip but still less flat, I shift between 2.5-3.5K, I the car pulls quite well. When I do a spirited driving, the I use the range between 4.5-6.5K. The GT86 will be far better.

[Dimman]

Originally Posted by carbonBLUE

ive done the calculations and for a 86 to have the same power to weight as a 3.7 v6 mustang you would need 200 whp prob 205-210 to be at the v6 gencoupe power to weight

intake, headers, exhaust should add the 20 whp you would need to be that fast in a straight line, but we would leave them around the corners with out a doubt

It's not only about power to weight, but also wheel torque to weight and shift points which has to do with where in the rev range torque is made, gearing multiplication, how much rpm you have available and wheel size.

[carbonBLUE]

Originally Posted by Dimman

It's not only about power to weight, but also wheel torque to weight and shift points which has to do with where in the rev range torque is made, gearing multiplication, how much rpm you have available and wheel size.

yup im just saying that its close enough, the 86 is geared a bit better for torque, weight also helps the 86 aswell

the mustang and gc has a larger contact patch when it comes to tires

ill do my mods and put it up against my friends 3.7 andd see how things compare


im just speaking theoretically ofc

[Deslock]

Not to resurrect an old thread, but I thought it'd be interesting to compare the COBB dyno to the January 2012 screencap.

To recap, Spaceywilly and Ryephile plotted curves based on the Jan 2012 screencap, but the plots showed peak power and torque coming at earlier RPMs than the official numbers, and much lower tranny losses than one could reasonably expect (only 3.5%). It seemed too good to be true, and there was speculation about the hard-to-read scale. WingsofWar plotted a hypothetical curve with a different scale.

Earlier in this thread, old greg and I had plotted wheel torque for the original crude curve from the .jp website, and then I later plotted against both interpretations of the screencap.

Now a video has surfaced showing results from a COBB dyno run of a stock BRZ. My initial reaction was "Oh, only 164 whp... that's a bit low." Then I looked more closely and realized its shape is close to the original interpretation of the Jan 2012 screencap. Output is lower, but it still seems too good to be true. If COBB's dyno run is representative of a typical BRZ:

• Peak torque is at 4500 and 5800 RPM (official spec is 6600 RPM)
• Peak power is at 6200 RPM (official spec is 7000 RPM)
• Peak power is a tad low due to the 6200 RPM dropoff
• The FA20 is underrated below 6200 RPM (since it shows a tranny loss of only 6%)

COBB's dyno stopped at 6800 RPM; here's a plot assuming it continues to drop at the same rate until 7400:



Wheel torque for 6MT with 4.1DR (using a tire dia of 24.3"... it might be as low as 23.9" or as high as 24.6"):



Estimated Acceleration vs 2004 WRX:



Something seems amiss because the 2004 WRX's traction advantage shouldn't be enough to overcome a deficit this large (going by MT's BRZ test, the 2004 WRX hits 0-60 and the 1/4 in less time, but the BRZ traps at a higher speed).

Of course, I'm comparing cars run on different dynos with different conditions (and perhaps COBB's BRZ had an especially strong engine or the WRX from that dyno was on the weak side).

Estimated Acceleration vs 2009 WRX:



Estimated Acceleration vs GTI:

[Guff]

[Zaneman]

Quality stuff good sir. Now if we could just work that terrible dip out of the curve we would be in business.

[Dimman]

Interesting thing about the 'too good to be true' numbers is that someone said that Cobb uses a Mustang dyno which is one of the 'heart-break' dynos. Very curious what an inertial one like Dynojet will read.

[Ryephile]

Here's my revised torque at tire plot based off the InsideLine dyno, where RPM scale is easily readable. My assumptions are using 844 rev/mile for tire rolling size.

[DarkSunrise]

Just saw this thread. Great job Deslock and Ryephile, very useful data there. Looks like optimal shiftpoints for the BRZ are: Redline in 1st and 2nd; Few hundred RPM short of redline in 3rd-5th.