Cobb Tuning dyno pull

[Jeff Lange]

Originally Posted by Subaruwrxfan

Sorry for a noob question...but why are the front tires spinning?

AWD dyno's have front rollers that are linked with the rear. Thus the rear wheels are spinning both. It costs a bit of power, so it's not always entirely accurate. A single-axle dyno would be a bit better to test with.

Originally Posted by Oriental Life

This dyno test sucks. Its a RWD car and they mount rear wheels up in the air?

What are you talking about?

Jeff

[Subaruwrxfan]

Originally Posted by Jordo!

Hmm. Runs pig rich up top.

Good, I wanna spit flames on the upshifts with an exhaust.

[GED68]

I though Subaru showed these numbers 200/151...At flywheel? vs 164/142 real world?

[tranzformer]

Originally Posted by GED68

I though Subaru showed these numbers 200/151...At flywheel? vs 164/142 real world?

[serialk11r]

Originally Posted by Jeff Lange

AWD dyno's have front rollers that are linked with the rear. Thus the rear wheels are spinning both. It costs a bit of power, so it's not always entirely accurate. A single-axle dyno would be a bit better to test with.

Jeff

Having all the wheels spin is more relevant than a single axle. Ideally you'd know transmission efficiency, effective moment of inertia of the drivetrain, rolling resistance, and power at the crank.

When you drive on the street, you lose power due to transmission loss, but the effect of moment of inertia will vary on how fast you want to accelerate, and isn't a true loss of power.

If you have one set of wheels spinning, you're ignoring the rotational inertia of the front wheels/brakes, which is silly because if you're going to include the rotational inertia of the rear wheels, you might as well include the rotational inertia of the front wheels, as on the road, you drive with 4 wheels contacting the pavement :P This way it gives you an idea of approximately how much power is going into moving the static (by this I mean non rotational) mass of the car, including rolling resistance.

Anyways, I'm surprised at this test because they're seeing much more low end torque than the HKS? run, or the Subaru published chart. I wonder if fuel has anything to do with this.

The midrange dip is I believe due to intake acoustics, not sure though.

[Grimlock]

Originally Posted by GED68

I though Subaru showed these numbers 200/151...At flywheel? vs 164/142 real world?

Testing at the wheels is always less than that the flywheel. The engine has to turn the transmission, drive shaft, differential, axles, wheels, etc so that reading will always be less than at the flywheel.

also, don't forget that every brand of wheel dynomometer will read a bit different, so don't take specific numbers to heart. The main purpose of them is to get a baseline reading (what we just witnessed), make some changes, test again, and see if there is an improvement.

[Draco-REX]

Originally Posted by Jordo!

Hmm. Runs pig rich up top.

That 20 wtq drop has got to go. That's just awful.

Pig rich? Pig rich is 9:1...:P As it is, you want mid 12s for power.

As for the dropoff, there's speculation that the throttle plate begins to close near redline to reduce strain on the engine. That would also explain the richening of the AFR. I wish someone would log the throttle plate.

Originally Posted by GED68

I though Subaru showed these numbers 200/151...At flywheel? vs 164/142 real world?

200/151 is at the flywheel. The 164/142 is at the wheels. It takes power to turn the driveline (gears, driveshaft, rear diff, axles, wheels) so wheel hp is always lower. In this case it's about 18%, but this might be a low-reading dyno.

[lupehoops26]

Originally Posted by GED68

I though Subaru showed these numbers 200/151...At flywheel? vs 164/142 real world?

Ack - whoops thought there was a unit conversion problem. carry on.

[oneday]

Originally Posted by engee

I wonder what Cobb will be able to pull out of this engine by tuning it. Definitely curious to see what results they can yield.

They sold so few Si/350Z/RX8 (and other NA) APs that it was not worth making them...so they stopped.

I said it before and I'll say it again: COBB is out of the NA tuning game...IF they decide to make an AP for this car I will be [pleasantly] surprised. But IF they do, how much are you going to be willing to spend on an AP that nets you 5-15hp? I doubt many would spend the $595 COBB gets for their FI APs and what they would sell this one for.

[subatoy]

Originally Posted by Tainen

[u2b]EVOQI-qfvxw&f[/u2b]


Enjoy!! Great numbers, imo.

Looking forward to seeing more out of Cobb in the coming months.

great numbers?!!!!!!!!

[Future]

Pretty sure Cobb (or any other) will be able to work something out... For the Mustang V6 2011+, Bama has made a flash tune that gives 18 RWHP and 22 ft-lb by pretty much only ajusting fuel/timing.

[Ryephile]

Originally Posted by subatoy

great numbers?!!!!!!!!

No need to be a jerk about it not being a dyno queen, like that's a surprise anyway. The numbers are correlative to advertised power, and torque is greater than expected.

That said, that mid-range torque dip is a massive canyon. I can only deduce it's the magic "efficiency zone" for highway fuel economy, and they chose to tune the engine to give up torque in that band to get better fuel economy. But, since the advertised fuel economy isn't that good, I'm out of ideas there other than "oops" tuning.

The torque also falls off much quicker at high RPM than the advertised engine plot, starting to give up at 6,200 instead of 7k.

Also, did everyone notice they stopped the pull at 6,800 instead of going to redline? It's likely there's no more power after that, but still, you'd think they'd want the data. Well, I'd want the data; Cobb may not care.

The stock AFR is a bit thick most everywhere. I can't think of a good reason this N/A GDI engine needs to be rich beyond peak-torque. E10 peak torque should be around 12.4:1, anything richer is just being wasteful unless this engine has a knock problem, which would be very strange considering it's direct injection and moderate BMEP.

Time will tell the story, hopefully.

[serialk11r]

I'm getting a bit worried because I just realized that if they're intentionally cutting power at the top (which is what it looks like), then they're doing it for a good reason...

By the way Ryephile, the torque dip is at 80+ mph highway speeds, definitely not going to be a magic cruising efficiency zone.
The magic cruising efficiency zone should be around 2000, where the long duration cam lobe is reducing pumping losses, and hence torque. Somehow this run shows the engine coughing out quite a lot of torque there though, so I have no idea what's going on. The more stuff we hear about the engine, the more confusing it gets rofl...can't wait to see the real thing, and logs of more parameters.

[tranzformer]

Originally Posted by Ryephile

No need to be a jerk about it not being a dyno queen, like that's a surprise anyway. The numbers are correlative to advertised power, and torque is greater than expected.

That said, that mid-range torque dip is a massive canyon. I can only deduce it's the magic "efficiency zone" for highway fuel economy, and they chose to tune the engine to give up torque in that band to get better fuel economy. But, since the advertised fuel economy isn't that good, I'm out of ideas there other than "oops" tuning.

The torque also falls off much quicker at high RPM than the advertised engine plot, starting to give up at 6,200 instead of 7k.

Also, did everyone notice they stopped the pull at 6,800 instead of going to redline? It's likely there's no more power after that, but still, you'd think they'd want the data. Well, I'd want the data; Cobb may not care.

The stock AFR is a bit thick most everywhere. I can't think of a good reason this N/A GDI engine needs to be rich beyond peak-torque. E10 peak torque should be around 12.4:1, anything richer is just being wasteful unless this engine has a knock problem, which would be very strange considering it's direct injection and moderate BMEP.

Time will tell the story, hopefully.

Could that be the reason they say to use 93 gas?