KK

iTrader: (4)

The real point Shiv brought up that I think make the most sense is what's the difference. If you car makes 100hp to the flywheel, but only uses 50hp at the wheels, then all you really have is 50hp at the wheels.

I think the best way to prove what works best would be to dyno a setup on a chassis dyno, then remove the engine and run it on an engine dyno and compare the averages. Then repeat for additional modifications to see if the average loss was nearly the same.

Mark

Ben

Most dyno's work on the principle of accelerating a large mass, and determining how much HP the car has by how fast it accelerates the large mass right. Well, I'd imagine that the weight of the drivetrain does have some effect. However, that weight is just being added on to the already large weight the car is accelerating on the dyno, which would make the drivetrains mass have not much of an effect on the final result. The 0-60 and 120-0 cases you posed have no bearing as many other factors are involved(tires, vehicle weight, drag, gearing, etc, etc).

MrAWD

You are forgetting other looses that exist in there. The major one is the momentum of inertia for every single rotation part. The thing is that 500 HP will spin everything in there much quicker (faster rate of the acceleration, not speed of the rotating parts it self) and that will require more energy, so the losses will go there. Check my previous post about that!

Fedja

WestSideBilly

iTrader: (1)

Tuning is 90% practical experience and 10% technical knowledge. Some of the best tuners in the world have never taken a math class past high school geometry, they just know what works based on past successes and failures, which is why you don't find many 22 year old tuners. Writing for a magazine is a credential? He writes tuning articles - minimal technical knowledge, from those I've read. I'm not slamming the guy, because he is a good tuner, merely pointing out that extracting horsepower from a motor is not the realm of scientists.

That said, he ignores nearly every aspect of mechanical loss in his writeup, and improperly explains how dynos work to boot. I realize he's trying to simplify it to something a non-engineer can understand, but his explanation is wrong. End of story. The only thing he says right is towards the end:

Sweft's example is actually a fairly good one. There are losses unrelated to the power at the input end, but most of the losses increase as the amount of power is increased - some exponentially.

We're pissing over an insignificant point, regardless. The supposed dyno which only one person here has seen, was done on an unknown dyno in unknown conditions by an unknown source. Comparing it to random WRX dyno plots is pretty useless. No use getting riled up over it

MrAWD

OK, one more try and I am out!


You are mistaken on what is causing the losses in the first place. It is not the weight of those parts that are causing it (well, in one sense they are, but let's not get that deep into this). Let's try it from the different angle then. If something (let say a tennis ball) traveling at the speed V1 and hits you, it will hurt. If other ball has a velocity of the V2 = 2 x V1 (twice as fast), you pain is going to be bigger (try it if you don't trust me). Now, in order to accelerate ball one to the speed V1, you need certain amount of force (lets call it F1). To accelerate bal number two to the velocity V2, you will need pretty close to the twice of the F1 (kind of like F2 = 2 x F1). The same thing will happen if you replace the velocity with the acceleration (derivation or integral of one of those will give you the other one)

The same goes inside the drivetrain parts when you have a rotational speed/acceleration instead of the straight line speed/acceleration. To accelerate a gear from one speed to the other in the twice a shorter time, you need twice as much of the force to get there. There are your additional losses that where not accounted in original article.

Have a first and maybe and think of this!


Fedja

boostedwrx

iTrader: (27)

can we get a link or picture of the dyno chart???? Where did this source come from anyway?

DSMBRETT

Actually Shiv is my boss and does know what he is talking about The same dyno was used for both cars to give accurate numbers as to the real world power of the EVO VIII over the WRX. It made over 40 wheel horsepower more than the Subaru. This is not to say that Dynojets(model the 2 cars were tested on) do not read higher than other dynos. On our in house dyno dynamics dyno a stock European spec EVO VII made 212-217 wheel horsepower on 91 Octane gas. The stock WRX makes around 160 Wheel Horsepwoer on this same dyno. These numbers can be compared to one another, as can the ones I posted at the start of this thread. As you can see the European spec car is making 52-57 wheel horsepower more than the WRX. The US spec car is only making around 40 wheel horsepower more than the stock WRX. This I beleive makes the US car pretty close to it's claim of 271 horsepower.

Brett Payne
Manager
Vishnu Performance
www.vishnutuning.com

Ben

Haha, what's the chances of that, the manager of vishnu tuning being the poster of this thread. How long till you guys think you'll have parts specific to the US STI out? Also, any power estimates for the WRX's Stage 3?

Anyway, MrAWD, I understand what you're saying, but the drivetrains relatively small weight and moment of inertia is just added on to the weight of the dyno rollers and their much larger moment of inertia. So in the end when the HP and torque are figured out, the drivetrains inertial effect is much smaller than you say. On the road, the vehicles own weight takes the place of the rollers. Sure it's not rotational weight, but it's still a large mass that needs to be accelerated, thus making the drivetrains effect smaller. If you were to simply measure the drivetrains loss with no additional weight in the equation(either dyno, or vehicle) then what you're saying would be correct.

gtr

iTrader: (6)

DSMBRETT ,How's the torque for the evo viii? I'll assuming that scc wouldn't want you to give us the curves so i'm not going to ask for them but is the torque comparable to the eurospec.

gtr

iTrader: (6)

Forgot to mention what gas was the evo 8 tested with 91? Is there going to be huge performance gains with 94?

broeli

iTrader: (19)

I thought you said the US spec Evo dynoed 230. That would be 70hp more than the 160 of the WRX and more than the Euro spec VII..correct? Maybe I read your post wrong

MrAWD

That big dyno roller is actually driven by the wheel HP of the car. The same goes for the vehicle weight when driven on the road. In either case, your drivetrain losses are the same and have nothing to do with the weight of the car or weight of the rollers on the dyno.

Well, I know I said I am done with this, but it was too hard. And you didn't get that either!!

Fedja

Sweft

I believe he was refering to a different dyno machine comparing the Euro spec evo to the WRX so the numbers don't translate over, but only comparisons do.

KK

iTrader: (4)

If you were to compare the European Evo VII dyno with the US Spec Evo, how would our version fare?

Didn't the Euro Evo VII have a lot of pinging and pull timing at 91 octane? Just wondering if a remapped ECU could do a little better hp wise for that car.

Thanks for all the info!

Mark

gtr

iTrader: (6)

I'm hoping the only thing differnt between the US and euro is the computer mapping