Any publication strap this car on a dyno yet?
 

Like to see what it puts down to the wheels in the real world. the k20 in the Si is pretty underrated putting down 180whp, like to see what this new engine does.

Nothing released or has been posted

This will have much higher drive train loss then the FWD K series. I would expect around 160ish wheel horsepower. But we will not know for sure until we see the same car in the same conditions run on a Mustang or Dyno Dynamics, etc. Inertial numbers are pretty much bunk.

This is not an AWD car. There will not be 25% loss.

25% drive train loss would be 150hp. My quote was "160ish" wheel horsepower; my estimate, not fact. The "160ish" hp number could be between 16% and 20% drive train loss, and a completely reasonable estimate. For the nit picker or mathematically challenged that could be anywhere between 160whp and 169whp. Thanks for playing.

Maybe its underrated from the factory and the 200 will be to the wheels........sigh....we can hope I guess

I would not get my hopes up, would be nice though. :D

Stock 2011+ Mustang GT puts down 375WHP, that's 10% drivetrain loss...

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Before anyone replies with, "Well that's a v8!" I understand this, I'm just pointing out that sometimes horsepower is underrated.

the 5.0 is underrated.

All the media coverage so far has been under the supervision of Toyota/Scion/Subaru at racetracks. As far as we know, nobody's been able to take one out in the wild...and to a known-quantity chassis dyno.

We'll see in time what the FA20 puts down. With any luck the people doing the dyno are smart enough to post a known quantity and have reasonable datalogging to see operational conditions.

This, also one must take in to consideration calibration, inertial vs eddy current, SAE corrected or uncorrected, wheel diameter, drag compensation, etc. The dyno really only tells you what you are making on a given day, with your particular car on that particular dyno. I was a dyno operator/tuner for 5 years of my life.

for the nitpicker or mathematically challenged i would think that 160ish would be more like 155-165 but seriously i can the upper 160s being most probable

i wonder if the solid rear axle can reduce drivetrain losses. i think most of the losses from rwd comes from the fact that you have to deflect the energy if you keep the wheels on the same plane as the diff there would be less total deflection...anybody know?

There are so many factors there. The short answer is may or may not. depending on the size of the pumpkin, the mass of the axles, the mass of the hub/wheel/tire/brake rotor/CVs, etc. Hell, even the viscosity of the differential fluid would effect drive line loss post transmission... This is all ignoring the transmission/engine itself. I do not think there is a simple answer to that, apples to oranges.

I think the 00+ Celica GT-S had 160 HP to the wheels, from its 180 HP engine. Granted it's FWD, but my point is that it's similar to this car, 4 cylinder, <2.0 L engine, and high revving.

I think expecting 160 HP to the wheels is too low, I can't imagine a drivetrain loss that much.. Maybe on conventional oil in the transmission, haha!

:word:


A dyno with a wideband and pyrometer are fantastic tools for tuning, but timeslips/laptimes are where it counts.

yeah i'm going to go out on a limb an say they underrated the car a BIT and that it'll push over 165 to the ground

GT-S :D!!! ill miss mine :cry:

http://www.youtube.com/watch?v=SiqkEEvcVoM

the gencoupe has more weight and didnt lose 40hp through the drivetrain. i think it'll post no less than 180hp

Rule of thumb for a rwd car is usually in the 15-20% range of course SAE correct and varying with dyno type.
With better tooth profiles, thinner fluids, etc these are lowering but bigger brakes also increase it. We'll see as it's all speculation for now.

16%-20% through a modern transmission? You might see that kind of loss if you're running power through an ancient automatic transmission but not a more modern unit and especially not a manual.

I would expect to see a high of 180, and lows of 170 on the dyno.

I'm only interested in the curve.


Not a momentary number under somewhat imprecisely logged conditions on a dyno with any possible unknown miscalibrations or correction factors that will just spark more debate anyway. Is it high? People will say the dyno reads high and others will say 'expected'. Is it low? People will say it reads low and others will say 'expected'.

I don't care one bit about that number. But when I hand it to Agile to tune, I will be comparing pre and post curves. THAT I care about.

If its anything like the 370Z, expect around 17% for both MT and AT on a dynojet with SAE correction..

amen.

Who do brakes reduce wheel HP?

Wow, glad to see someone in here understands what's important :thumbup:

I think on the dyno it might read lower since the increased rotational inertia absorbs a little energy. But it's not really lost energy, just energy that doesn't appear on the dyno sheet ;)

Unfortunately marketing a single HP number is a lot easier than explaining the power curve to 99% of the population.

I love curves. In all their forms. :)

Carrying only about the if probably as ignorant as carrying only about the numbers

What?

Remove the words carrying and insert caring.

I think the friction between gears increases with higher forces. So if you increase the torque of the engine the loss increases. Not to mention the loss is different in each gear, as the differential sees higher forces in lower gear. Otherwise say a Ferrari which can lose almost 100Nm after the input shaft would always need >100Nm to turn the transmission, which I don't think is the case. Otherwise Ferraris would be getting more like 3mpg instead of 10 on the highway or whatever lol.

Drivetrain loss is neither a flat % nor a fixed number.

Rotational-only components before the transmission (such as flywheel, crankshaft) soak power, but only when RPMs change. They do not soak any power when the RPMs remain constant. Higher mass (weight) parts increase the power soak. This is one reason people go after lightweight flywheels. There is no difference between a lightweight and a heavy when you keep the RPMs the same, but the heavier one resists engine change more, which steals a bit from acceleration, but can also be of a benefit when you want to maintain momentum (typically not an issue for performance oriented driving, but a common factor for commuter cars)

Rotational-only components after the transmission (such as driveshaft, axles, wheels) soak power, but only when the vehicle speed changes. They do not soak any power when the vehicle speed remains constant. Higher mass (weight) parts increase the power soak. Carbon fiber driveshafts improve engine response, but are really tied to vehicle speed, not RPM, so they have a greater impact when the speed change desired is the greatest. Smaller vehicles of the same drivetrain configuration typically have less loss from this aspect since their driveshaft, axles, and wheels are typically smaller. It's the mass of the parts that matter though, not the size (different materials can make larger parts weigh less than smaller ones of a heavier material)

Mechanical linkage before the transmission (such as the e-shaft gear in a rotary, input gear on the transmission, alternator, pulleys) soak power at an increasing rate as RPM increases. This number can easily change for cars based on lubricating fluids and surface treatments. Race teams apply REM and WPC treatments to gear contact surfaces specifically to reduce drivetrain losses, and it works.

Mechanical linkage after the transmission (such as the output gears, diff gears, axle joints, wheel hubs) soak power at an increasing rate as vehicle speed increases. This number can easily change for cars based on lubricating fluids and surface treatments. Race teams apply REM and WPC treatments to gear contact surfaces specifically to reduce drivetrain losses, and it works. The frictional surface area matters here as well. For example larger wheel bearings generate less heat and drag than smaller ones (of the same material and velocity).

Fluid and air pumps before the transmission (oil pump, water pump, any vacuum drag from emissions components or the engine itself, power steering pump if you have a fluid system) soak power based on RPM at an exponential rate. The rate of loss increases dramatically as RPMs increase. The viscosity of the fluid and pump efficiency can make dramatic differences as well. For example, the RX-8 OEM water pump uses flat vanes on the impeller to push the water through, and a common upgrade is to go to a spiral impeller design, and this has been proven to increase measured WHP between 5-8whp. Obviously it doesn't do anything to the engine's output itself, it's just reducing some of the drivetrain loss.

Fluid pumps after the transmission (diff) soak power based on vehicle speed at an exponential rate. The rate of loss increases dramatically as the vehicle speed increases. Power losses are also impacted by fluid viscosity. The dyno difference of an RX-8 on the same dyno/same day between cold diff fluid and hot diff fluid is around 5-7whp.


Some components have more dynamic drivetrain loss explanations, such as the transmission fluid. Part of it's loss is based on RPM, part on vehicle speed. Some components also change based on ECU or triggers. For example the A/C compressor on an RX-8 soaks lots of power, until you pass a certain point in engine load, and then it internally shuts itself off on command from the ECU until engine load drops back under the threshhold.

There is also loss from the tires themselves, somewhat based on vehicle speed, but it's more dynamic than that, due to the change of shape a tire undergoes as the speeds increase, and every tire is different based on internal composition, sidewall flex, tread squirm, etc...

So in the end, it's always a moving target, and many people just try to give a % of what they think the loss rate is at, but even that isn't really that precise since it can change easily just by dyno'ing in a different gear (and thus having a different 'vehicle' (wheel) speed that changes the loss rates of the diff and tires) or with a different / non-stabilized fluid temps (repeated runs will heat up the fluid, reducing viscosity. One team just runs their RX-8 on a dyno until their transmission, oil, and diff fluid temps stabilize before bothering to record the result.)

If anyone is interested in the discussion, I can link in two dyno's from RX-8s where one is OEM components and one has REM WPC treatments on the gears, low viscosity fluids, etc... for curve comparison. The race dyno is notably higher across the board, but the curve itself doesn't drop off in high RPM at nearly the same rate as OEM. The owner of that team shares lots of his R&D, and is quite serious about reducing drivetrain loss (especially since the RX-8 has so much of it from the start)

Edit:
Added more examples and adjusting factors.

^Nice post!

Hell yes. :)

Before I post these, PLEASE UNDERSTAND THIS:
I am not posting for "Bragging rights" or "omg the rx-8 is slow" or whatever results. I am only posting these for comparison on what anti-friction coatings can do to reduce drivetrain loss when applied to the gears

I am also not posting them as embedded images to avoid people that ignore what I'm saying and see a dyno chart and immediate start with a knee-jerk response completely outside of the intent. So please refrain from comments that would turn this into a flame war in any direction.

This chart (http://www.rx8club.com/attachment.ph...0&d=1305560087) is one of the clearest OEM charts we have, and also a very good baseline to compare the REM/WPC curve to. The lower stock curve is in blue. The upper curve in red is with a quality rebuild and porting work. This comparison is important since the rebuild and porting work are roughly equivalent to what the race team does for their race engines, and can help you factor out what is just engine modifications.

This chart (http://www.rx8club.com/attachment.ph...7&d=1308147670) is from a race team's dyno (Owner's website: http://www.meyer-motorsports.com/Home/Home.html Sponsor driven website: http://www.xowii-racing.com/XOWii_Racing/Home/Home.html) with the REM / WPC treatments on the transmission and diff gearing.

The torque curve is significantly flatter throughout the entire range. The low torque increase is from their intake, exhaust, and tuning (mostly), but it holds that torque REALLY well, because they are able to mitigate so much drivetrain loss that normally increases as the RPM / speed increase. The team owner stated that most of the lack of drop-off from the 7k+ RPM torque curve is as a result of their REM / WPC treatment. He did not post a pre-treatment dyno chart for comparison however.

It should be noted that this team has unlimited access to a particular dyno shop (he doesn't share the name), so all of their dynos are on the same machine, and they have run literally thousands of dyno's on their car (with various engines). So they measure the hell out of any small change.

I think pump power increases as the cube of speed, not exponentially, small detail.

Also the losses to the fluids in the transmission/diff/whatever increase with speed, but the frictional losses (as a proportion of power/torque) should be torque dependent, not speed dependent. But I guess we are talking max torque curve so that's relatively constant.

I think I've seen people try just different viscosity fluids in the transmission and the differences in loss are pretty huge.

yeah. stupid swype fails me again

increasing by the cube power is increasing something exponentially