More power at higher speed?

Concorde Rules said:
I notice this effect in my golf mk1 amazingly!

If I neutral it at 70, it idles at about 1100, if I then come off at sit stationary, It drops to 900ish!

Always thought it must be colder air or something like that to cause it, weird really :)
Click to expand...


Road speed sensor? My megane and 19 previously will idle higher if the car is rolling even at low speeds.
 
helpimcrap said:
i also seem to remember ducati and aprillias as being spot on. my honda on the other hand. 140mph+ and i get done for 128mph?? bugger.
Click to expand...

my kwak was out about 6% @ 100 (though I have 5 lower profile than stock rubber), and with gearing change almost 14%, fixed that with a speedohealer and some very tricky riding at 100mph while looking down at GPS lol
 
Malt_Vinegar said:
RAM AIR

Operating Conditions
Temperature = Tair = 20C = 293K
Atm. pressure = Pair = 14.7PSIA
Cpair = 1005J/KgK
K = 1.4
The Cpair and K are constants for air.

Case 1 @ 100Kmh (62Mph) = 27.78m/s

Calculating temperature of the ram air

Tramair = ((Vcar^2/2gc)/cp) + Tair
Tramair = (((27.78m/s)^2/2(1kgm/Ns^2)/1005J/kg) + 293K
Tramair = 293.4K

The temperature increased by 0.4K or 0.4C.

Pram = Pair (Tram/Tair)^(k/(k-1))
Pram = 14.7PSIA (293.4K/293K)^(1.4/(1.4-1))
Pram = 14.75PSIA - 14.7PSIA
Pram = 0.05PSIG (gauge pressure)

So as you can see driving 100kmh will only have a gain of 0.05 psi! now lets try for 200kmh.

Case 2 @ 200Kmh (124Mph) = 55.5m/s

Calculating temperature of the ram air

Tramair = ((Vcar^2/2gc)/cp) + Tair
Tramair = (((55.5m/s)^2/2(1kgm/Ns^2)/1005J/kg) + 293K
Tramair = 294.5K

The temperature increased by 1.5K or 1.5C.

Pram = Pair (Tram/Tair)^(k/(k-1))
Pram = 14.7PSIA (294.5K/293K)^(1.4/(1.4-1))
Pram = 14.97PSIA - 14.7PSIA
Pram = 0.27PSIG (gauge pressure)

By seeing how the velocity of the car increases the ram air effect...it is barely anything! I'll conclude by saying that in racing circles where a 1/100th of a second counts, it's worth it, but don't let Pontiac fool you into thinking it works on the street.

(stolen from http://hondaswap.com/forced-induction/myths-electric-turbos-ram-air-41316/)
Click to expand...

Nice link.
Shame it states nothing about the CSA of the airbox inlet or the air consumption of the engine, making the point of that post pretty pointless. You have simply calculated the stagnation pressure at the front of the vehicle.
 
You must log in or register to reply here.
Back
Top Bottom