That's what my arguement was, that it's more accurate to look at a set HP loss. But we've been through all of this and there is no chance of getting either side to budge so just do a search for the last dyno thread.

 

Yes, you are correct about this part. It is all the same system. Dyno wheels are way bigger than the anything else that has to rotate inside the car. That is why you get 240 HP at the dyno wheel and loose 40, 50, or even 60 HP inside the drivetrain.

So, the same way that big heavy dyno wheel gets to measure the power passed on it from the wheels, some of that power goes to the all of the rest of the rotating parts. So, if you spin that big wheel from speed V1 to speed V2 in the time T1 that would give you HP rating of P1. Now if you do the same thing from V1 to V2 in shorter time that we call T2 (remember T1 is bigger than T2), you will also get bigger number for the power P2 compared to the P1. That was all happening while trying to spin a big mass of M1 from the speed V1 to V2. That is how you get your HP readings.

Now move inside the trainy and check one of the gears that has to spin during the same process. This time your gear has a mass of M2 which is much smaller that the dyno wheel mass that was M1. To accelerate that small gear with the mass of M2 from the speed V1 to V2 in a time T1, you will need Pp1 amount of power. Now, if you have more power and spin it in time T2 (shorter than T1 in the first case), you will also have to spend more power on that small wheel and if you would measure it, you would get Pp2.

By adding all of those power numbers from P1 over the Pp1 and the rest of them (Pa1 + Pb1 + Pc1 + ... + Pp1 + ... = SP1), you will get total power number for the case one. In the second case you will have P2 and SP2 (sum of the Px2s). Ratio between those two will stay the same all the time, which will give you your losses.


Fedja

 

Aston

 

More then likely all the car's tested so far are preproduction test mules and may be a little different from actual production models. Considering the lead times of magazines, all of this stuff we're reading now was done 2-3 months ago, back when we didn't know how much hp it was supposed to have.

 

The only test we know for sure done by a magazine, was done at LACR, and I'm assuming it was R&T since they list the same #'s someone posted it ran at LACR. Like we discussed before LACR is 2700ft above sea level and has a crappy surface. Everyone I know with forced induction that runs at LACR generally runs about .5 slower in the 1/4.

 

In reference to the argument about percentage or constant drivetrain loss, look at the amount of power that JoCCe and yelo3 put down in their Evos at the crank, and how much power they have at the wheels. JoCCe puts down something like 650 hp at the crank, and 530 at the wheels. I don't know what yelo3's crank power is, but he puts down 590 at the wheels. Just looking at his mod list, you can tell he has something like 725 or so.

These cars are losing around 18% to the wheels across their drivetrain, which is less than 24% because of mods they did to the drivetrain, such as magnesium wheels, lightweight flywheels, dogboxes and lightweight clutches.

If the constant theory were right, JoCCe would make 530 at the wheels and only 580 or so to the crank, and the same would apply to yelo3.

 

Have they actually had the engine out of the car and HP measured at the crank? If not, then none of those numbers mean anything, they're just estimates.

 

Even the AWD cars? An AWD car should still be able to get a decent launch. Maybe not the best launch, but I doubt it would spin enough to loose .5 seconds. True there's the altitude as well, but that doesn't effect FI cars as bad. So if it really were over 300hp I'd still expect better than 13.8.

 

Hey Claudius!

Well ......... no use waiting any longer....... preemptive it is. Your an arss!!! LOL


Speedlimit.......

 

"Have they actually had the engine out of the car and HP measured at the crank? If not, then none of those numbers mean anything, they're just estimates. "


I should say brake horsepower then. I'm sure that they've both had their engines out, but I can't say whether they've actually tested hp at the crank when the engines were out. Nevertheless, even with brake horsepower you can tell about what crank hp would be.

And their losses are % based to their wheel outputs.

If the constant theory were right, then the 1000+ hp skylines and supras would only be losing 50 hp to the wheels from the crank, and i've never seen one of those cars with that little drivetrain loss.

 

why is everyone saying BRAKE horsepower?
maybe they had a few too many

 

thats what bhp stands for.

 

wow.. awesome numbers!!

 

Brake Horsepower (bhp)
(various explanations from various places)

- the amount of horsepower the engine actually delivers after internal friction and parasitic loses are taken into account.

- the vehicle’s horsepower measured where the power is delivered (for example, at the rear axle of a truck tractor). Shaft horsepower is the power measured at the engine itself, before any losses from the clutch or differential occur.

- the rate at which an engine does work, expressed in horsepower. It is measured by the resistance of an applied brake.

- Dynamometers measure torque by use of a brake. Brake torque is simply a measurement of how much resistance is needed to hold the engine at a steady rate of speed. This is commonly referred to as a step test, usually taken in 250 rpm increments. Brake Horsepower (BHP) is then figured using this formula, HP = (rpm × Torque) ÷ 5252 . The problem with brake torque is that it is not effected a measurable amount by the inertia of the engines rotating and reciprocating parts. For an acceleration engine, there is a better way.

- etc.

 

I thought bhp stood for base horsepower