Friend says spark plugs changed rpm at speed, please correct him.

[JMortensen]

Can I ask you guys why a car requires more rpm to travel at the same speed when going up a hill?

Either it's an automatic and the torque converter is slipping or the clutch is slipping.

[MrFancypants]

^^ Or you downshifted

 

 

- Greg -

[DavyZ]

Can I ask you guys why a car requires more rpm to travel at the same speed when going up a hill?

 

When a car is traveling in top gear on level ground at a legal speed limit, the engine is turning low rpms because it doesn't take much torque or HP to keep it running along (the engine is not making a lot of torque in higher gears and low rpm because it doesn't need to be). Once the hill comes along, the weight of the car becomes a factor and overcomes the amount of torque the engine makes at low rpm, so downshifting may be necessary to get the car within the torque curve and get it up the hill. Keep in mind this is what you are experiencing. If a car is running right along within the broad part of the torque curve, it will not need to be down shifted for higher engine rpms when going up a hill, so what the guys have answered so far is correct for other possibilities.

 

That's an over-simplification, but you must understand torque, gearing, and HP.

 

Davy

[rdsk8ter]

exactly where did he stick the plugs?

[MONGO510]

"dxpong: I talked it over with a professor at my uni

dxpong: due to an increase in HP/Torque is what's allowing the car to run at a lower RPM to KEEP the car at speed"

 

I can't believe he would ask a college professor a question about a real world problem and expect a knowledgable answer. This kid is hopeless!

[DspecDJ]

From what I understood is that platinum, double-platinum and the new iridium tipped plugs don't effect spark at all, they're just harder metals so over time there's less errosion of the plug tip meaning all those lazy people don't have to do as much maintenence on their cars, so based on what I've been tought, I'd say your friend was probably just driving on some bad plugs before and now he's getting the spark he should've been getting all along, but as far as the whole RPM thing goes, with a clutch, there should be no difference in RPM at a given speed in whatever gear it is he's using, a difference in power would only change how quickly the car reaches said RPM and speed. But at the same time it makes me think of how load effects speed and RPM, how at school on a dyno cars are capable of much higher wheel speeds than on the road due to the lack of wind resistance and engine load. Something else to think about I suppose.

[Challenger]

I was at a car show recently and this guy had an old pontiac pirresian or something to that sort with a stack at the muffler cause he was running the motor in place and was selling these little secondary coils that go between the distributor and the coil. He had a circuit board to be able shut of spark plugs and show the speed of the car so he could show how his product helped. This doesnt deal with rpm/speed but when he put the coil on at the same throttle position the car speed up about 5-10 mph.

He claimed it helped with mileage and probably a very small amount of power.

[AK-Z]

Platinum plugs are crap. Platinum is a poor conductor and multi-point plugs ar pointless IMO. Spark usually only arcs over one point to another. Just companies wanting more money. Don't know about iridium though.

 

Maybe the spark plug circuit is causing his auto trans to not shift up because of false readings? or his clutch is slipping.

[savageskaterkid]

Would a properly inflated tire do this, if it was flat before?