Horsepower % lost

[tholyoak]

Yes the frictional loss will increase, but do you really think it would account for a 30 hp loss in the two examples, I for one don't think so, as the amount of heat generated would be pretty extreme and lead to failure of parts in pretty short order.

Anyway, I think trying to extract flywheel numbers from rwhp numbers is pointless.

Todd

[blue2000s]

Originally Posted by tholyoak

Yes the frictional loss will increase, but do you really think it would account for a 30 hp loss in the two examples, I for one don't think so, as the amount of heat generated would be pretty extreme and lead to failure of parts in pretty short order.

Anyway, I think trying to extract flywheel numbers from rwhp numbers is pointless.

Todd

Yes, it will increase in direct proportion of the power (actually torque, but whatever) increase.

[Lucky]

Originally Posted by tholyoak

...the amount of heat generated would be pretty extreme and lead to failure of parts in pretty short order...

Believe it. That is exactly why there are trannies desiged for 300 HP and different ones for 100 HP.

[blue2000s]

Every system in the transmission is built with what's called a factor of safety, which means they are overdesigned for purposes of functionality under extreme conditions, accounting for any manufacturing variations/defects, accounting for any misjudgement in engineering or inaccuracy in calculation, and longevity. When a more powerful engine is placed in a car that wasn't designed to accept it, this margin for safety is reduced, but it still may be enough for the car to work, at least for a while.

[Grizzly]

Originally Posted by blue2000s

Every system in the transmission is built with what's called a factor of safety, which means they are overdesigned for purposes of functionality under extreme conditions, accounting for any manufacturing variations/defects, accounting for any misjudgement in engineering or inaccuracy in calculation, and longevity. When a more powerful engine is placed in a car that wasn't designed to accept it, this margin for safety is reduced, but it still may be enough for the car to work, at least for a while.

So that's why I go through so many AODs.

This is what I think Tholyoak is saying:

Let's say you have a 986 Boxster with 240 HP. If it looses 15% HP (or 36 hp) you have about 204 HP at the wheels.

Now you do a engine swap with a 3.6L engine that has maybe 330 HP. It will be in the same car with the same exact tranny, tires, everything. So, how much HP to the wheels? 330- 36= 294 HP or 330-15% (50 hp) = 280??

[blue2000s]

Originally Posted by bmussatti

This is what I think Tholyoak is saying:

Let's say you have a 986 Boxster with 240 HP. If it looses 15% HP (or 36 hp) you have about 204 HP at the wheels.

Now you do a engine swap with a 3.6L engine that has maybe 330 HP. It will be in the same car with the same exact tranny, tires, everything. So, how much HP to the wheels? 330- 36= 294 HP or 330-15% (50 hp) = 280??

Like Lucky and I said, 15%.

[Grizzly]

Originally Posted by bmussatti

This is what I think Tholyoak is saying:

Let's say you have a 986 Boxster with 240 HP. If it looses 15% HP (or 36 hp) you have about 204 HP at the wheels.

Now you do a engine swap with a 3.6L engine that has maybe 330 HP. It will be in the same car with the same exact tranny, tires, everything. So, how much HP to the wheels? 330- 36= 294 HP or 330-15% (50 hp) = 280??

I think 280, but of course, I didn't finish engineering school. I went a different route.

[JackG]

Originally Posted by Grizzly

So that's why I go through so many AODs.

No, it's your right foot that's to blame.

[tholyoak]

OK well I really didn't believe that in transplanting my 2.5L engine for my 3.6L X51 motor that it takes 15 more hp to get the power from the crank to the wheels.

I think I found the answer. It turns out that the 15% loss has to do with the rate of acceleration of the large drums on an inertial dyno. On a load control dyno, you assume a constant amount of parasitic drive train loss.

A good explanation can be found here for those that are interested.

http://home.earthlink.net/~spchurch/churchautomotivetesting/id12.html

Todd

[blue2000s]

Originally Posted by tholyoak

OK well I really didn't believe that in transplanting my 2.5L engine for my 3.6L X51 motor that it takes 15 more hp to get the power from the crank to the wheels.

I think I found the answer. It turns out that the 15% loss has to do with the rate of acceleration of the large drums on an inertial dyno. On a load control dyno, you assume a constant amount of parasitic drive train loss.

A good explanation can be found here for those that are interested.

http://home.earthlink.net/~spchurch/churchautomotivetesting/id12.html

Todd

That's accounted for and subtracted out when you get the dyno sheet so it's not part of the loss we're talking about. You're stuck with 15% man.