Using a dynamometer w-o a wind tunnel, is inaccurate simulation of usage

in a warm / hot climate, because @ high rpm, vehicle will be
moving @ high speed : the air cooling received by battery +
alternator + inlet manifold ( usually heated by radiator coolant
) + exhaust manifold & pipe & muffler will increase torque.
Only in a wind tunnel with air flow @ the same speed as vehicle
would be @, can simulation of usage be accurate.

I removed my bonnet's 3 rubber seals & small front grille to
let in & out more air : in 28 - 30ºC air I found that @50 kph,
torque rose 5%, @90 kph torque rose 10%, I think @110 kph
torque incr will be >10%.
E.g. BMW's oil sump has grooves for air cooling ( mine does
not ), so the impact of air flow on such a car must be even
bigger in a hot climate when its oil is hot.

On Jul 19, 9:38 pm, "TE Chea" > wrote:

> I removed my bonnet's 3 rubber seals & small front grille to
> let in & out more air :

The manufacturer of your car spent good money putting those
three rubber seals there. They had a reason to do it, and it probably
has to do with keeping the thing cool at LOW speeds, or sitting still
and idling, not at high speeds. Those seals and their baffles act to
keep the hot air coming off the radiator from circulating around and
getting back into the front of the radiator. Serious overheating can
result.
When I was a kid I had a 1962 VW Beetle. I bought it with a
busted crankshaft, and bought another engine and stuck it in. I left
off all that darn sheetmetal around the back of the engine "to let
more air circulate," and ended up with a really hot engine. My wise
uncle told me that auto engineers aren't allowed to spend money on
stuff that won't make the car run better or last longer (until it's
off warranty, at least), and that therefore those bits of baffling
were probably rather important. Second-guessing the engineers without
all the information can lead to unanticipated problems.

Dan