Why Do Cars Lose BHP?

[DrivingTheDream]

Why do older cars when dyno'd have a loss of BHP? Sometimes quite a big loss. If all parts are working the same etc? I read somewhere that NA cars tend to do this more so than turbo'd cars, is this correct?

Also while I'm on will my K reg Supra have lost quite a bit of power (there's no decent RR's from what I know in the NE to test).

[richardstock1]

Valves may not be sealing properly, injectors may be getting sticky, piston rings may be wearing and loosing that little bit of pressure, moreplay in the bearings which means bhp lost due to more movement, camshafts would be wearing so valves dont extend as long etc stuff like that

[bromy]

General wear.. friction causes the wear increasing the manufactures engine tolerances reducing efficeincy

[GeordieSteve]

Plus dynos aren't completely reliable at the best of times

[DrivingTheDream]

How do Supra's fair over time compared to other cars? Also is it true regarding turbo'd cars lasting better than NA cars?

[bondango]

Yup definately down to the Effeciencey of Engine and supporting components.

[Max Headroom]

So if someone was to have their engine rebuilt, their bhp would go up then, given that engines are now 12 or 13 years old?

[bondango]

I would like to think so, but also theres the Effeciencey of the Turbos, exhaust system, the Fuel system. the electrical system Etc etc that needs to be taken into consideration.

Also, a lot of manufacturers have been known to tell little white lies when they release power figures -

I would like to know though, were the orginal figures measured on an engine dyno when they were 1st done 14 years ago??

[Max Headroom]

Don't have to worry about turbos, havent got any. :)

[bondango]

yeah but im taking on the broader theme of engines and power loss over time lol

but it depends on how much your actually down on the quoted factory figures, if you dyno'd 20bhp less, would you invest in a FULL rebuild to gain it back?