Horsepower % lost - 986 Forum - The Community for Porsche Boxster & Cayman Owners

blue2000s · 10-24-2007, 06:30 AM

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 · 10-24-2007, 09:24 AM

Quote:

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.

10-24-2007, 09:40 AM

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 · 10-24-2007, 10:13 AM

Quote:

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 · 10-24-2007, 10:14 AM

Quote:

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 · 10-24-2007, 10:35 AM

Quote:

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 · 10-24-2007, 02:54 PM

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 · 10-24-2007, 02:59 PM

Quote:

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.

rule1 · 10-24-2007, 03:26 PM

I pulled 207 HP and 172TQ on Imagine Auto's dyno. I have a 2000 2.7 with EVO intake, headers and exhaust. Heres the ? should I do the GIAC flash or is it worth it? By the 15% I am already getting 243.6 HP to the crank. Will the Ecu flash really ad more?

edevlin · 10-24-2007, 03:30 PM

"I pulled 207 HP and 172TQ on Imagine Auto's dyno. I have a 2000 2.7 with EVO intake, headers and exhaust. Heres the ? should I do the GIAC flash or is it worth it? By the 15% I am already getting 243.6 HP to the crank. Will the Ecu flash really ad more?"

I picked up about 12 hp when I added a chip to my car.

Ed