RPM drops during acceleration downslope.

• bmw_lover

  9 May 04, 08:39

  I just realized that the RPM drops even when i accelerate while going downslope. can anyone tell me why?
• hell_jul

  9 May 04, 09:47

  BeCos' Yr accerlerator cable is broken...
  so when U step on it it seems 2 u as if u R acelarating But actuali u r not...
• Mercury_1

  9 May 04, 11:57

  Originally posted by hell_jul:

  BeCos' Yr accerlerator cable is broken...
  so when U step on it it seems 2 u as if u R acelarating But actuali u r not...

  If the cable was broken I dun think he could even reach the crest of the hill in the first place
• Theatre Of Dreams

  9 May 04, 12:25

  
• bmw_lover

  9 May 04, 12:36

  this is smth i noticed on a few cars.... wondering could anyone clarify my doubt?
• manualisbetter

  9 May 04, 13:08

  Originally posted by bmw_lover:

  this is smth i noticed on a few cars.... wondering could anyone clarify my doubt?

  I believe when going downhill, the rotation on the wheels is higher than what the gearbox is actually rotating... in this case, no power is needed to turn the wheel, and that's make the RPM lower. If you are going on flat ground or upslope, the high RPM is because the car needs to be push by the engine.
  
  Is yours a manual car? Becos auto mode when going down hill, the wheels and gearbox are still synchronized locked and the wheels rotate the engine RPM too.
  
• tailslide

  9 May 04, 14:44

  i'd assume your car is an auto? manual gearboxes have fixed speed/ rpm/ gear ratios so unless you change to a higher gear manually, it is impossible for the rpms to "drop" on their own.
  
  think for most autos, the ecu will automatically kick up to a higher gear when it senses the gradient going downslope to maximize the efficiency of the engine (go downslope, engine can relax mah). higher gear means for any given car speed, ur engine is turning at a lower rpm at a higher gear compared with a lower gear. (confusing? i hope not, this is a basic driving knowledge) it saves u fuel in fact. think i never experience my dad's auto gearbox drop gear when i accelerate downhills, quite impossible unless u using step/tip/tronic.
  
• bmw_lover

  9 May 04, 14:46

  rpm is how faster your engine is rotating right? so theoretically dusent matter downslope or slope one as long as u acc(to increase speed) your rpm should increase right? I'm driving a manual but i've also driven an auto car, and it applies for both. maybe someone could try it next time.
• bmw_lover

  9 May 04, 14:48

  Originally posted by tailslide:

  i'd assume your car is an auto? manual gearboxes have fixed speed/ rpm/ gear ratios so unless you change to a higher gear manually, it is impossible for the rpms to "drop" on their own.
  
  think for most autos, the ecu will automatically kick up to a higher gear when it senses the gradient going downslope to maximize the efficiency of the engine (go downslope, engine can relax mah). higher gear means for any given car speed, ur engine is turning at a lower rpm at a higher gear compared with a lower gear. (confusing? i hope not, this is a basic driving knowledge) it saves u fuel in fact. think i never experience my dad's auto gearbox drop gear when i accelerate downhills, quite impossible unless u using step/tip/tronic.
  

  oh then it must just be my imagination. haha. but i'm so pretty sure the rpm dropped.
• Praetorian111

  9 May 04, 15:02

  Originally posted by bmw_lover:

  oh then it must just be my imagination. haha. but i'm so pretty sure the rpm dropped.

  Dun think there is anything happening to your car dude....
• dansplace

  9 May 04, 22:18

  Do you have problems accelerating at all?
• HENG@

  9 May 04, 23:39

  u never accidently step brakes?
  
• bmw_lover

  10 May 04, 10:14

  lol no... i just let the car roll down abit(with acc) till the rpm increases, then i step the acc, and i saw the rpm drop.
  
  *mind boggling*
• dansplace

  10 May 04, 18:48

  "Hello? Performance Motors? .... "