rki2007

Technical terms and details-explanations

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Hi automobile lovers we all would have come across many technical terms in the cars/bikes discussion threads, offcourse many of them know about all that and have technical knowledge about that. But for people like me, there exists no idea about all these following terms. Can any one explain.

1) What is Torque (Nm/Kgm)

2) What is RPM - Even though i have seen it in my bike, i am not aware of the technicality involved in it.

3) What is BHP- Roughly i have an idea about it as horse power.

4) What is Turbo Lag.

 

Even other technical terms and issues are also welcome. Please share in your knowlegde.

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@singhji, make use of EDIT option while posting in short intervals

Turbo lag is the lag time between the pressing of throttle(accelerator peddal ) and the response of the vehicle. This is generally applicable on diesel engines.

Small correction here,

Normally in Turbo Diesels, Tubro kicks in around say 2000rpm. After this there will be a sudden surge of power.

The lag in power between 0rpm and 2000rpm(i.e., till Turbo kicks in) is called Turbo Lag

 

Diesels are Torquey and

Petrols are Revv happy

 

Torque is a main character of Diesel, which helps in pulling the car seamlessly(initially).

In Diesel engines, max Torques will fall at mid max rpms.

i.e., say an engines has max rpm is 6000rpm, and its max torque hits at 3500rpm,

This means, there is no point of accelerating your engine more than 3500rpm, as there will be no use. Only Fuel loss and no power gain if done.

 

For this only, a Tachometer is used (to know engine's rpm).

When you buy a car, see its torque, eg 89PS@3500rpm. So with the help of Tacho, make sure you engine doesn't cross 3500rpm speed.

 

 
creativebala2009-10-23 20:07:52

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beautiful singhji1977- i am really impressed. Are you an automobile/mechanical engineer

 

I didn't understand the diagram. Can you explain please!!!!
rki20072009-10-23 20:04:06

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Common Acronyms

 

HVAC heating ventilation and air conditioning system
NVH Noise, vibration, and harshness

ICE, In car entertainment

ABS, Anti lock braking

ECU electronic control unit

OEM original equipment manufacture

SRS Supplemental Restraint System (air bag)
OBD onboard diagnostics
EBD, Electronic brakeforce distribution 

traction control system (TCS), also known as Anti-Slip Regulation (ASR)

PSI pounds per square inch

VTEC (Variable Valve Timing and Lift Electronic Control) also VVT,VTVT

CRDI - Common Rail Direct Injection

VGT/FGT-  Variable/Fixed Geometry Turbocharger
creativebala2009-10-23 20:26:53

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I understand the torque part but if an example can be given considerig a certain car, that would be great.

So if a car hits its maximum torque at lets say, 4000 rpm or something. Does that mean that in every gear, reving it after 4000 rpm is useless or does this apply only to the 5th or the top gear?

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torqueb.gif

To produce same torque at the nut- A has to apply 20 pounds and B has to apply 10 pounds of force.

 

The practical implication is that if we change the wheel size of the car then it effects on every thing. 

 

1) RPM of larger wheels are less as compared to smaller wheels if the engine is same.

2) the torque effect is more in smaller wheels as compared to larger wheels if the engine is same.

3) average of the vehicle is affected as we change the tyre sizes other than company recommended.

 

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beautiful singhji1977- i am really impressed. Are you an automobile/mechanical engineer

 

I didn't understand the diagram. Can you explain please!!!!

Thanks for the compliments rki2007. I am not a automobile but a FIRE ENGINEER.

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Relation: engine rpm nd torque

If the torque value is more at lower rpm, than frequent gear changes r not required. more torque at less rpm means the car engine is peppy nd will give initial thrust to the engine. this will indeed help in city/ traffic driving.

Some more technical terms:

Overdrive gear: A gear that drives the vehicle faster than the engine.

Notchback: Booted version of the hatchback.

DOHC engine: Having a double overhead cam shaft. i10 & Ritz both have DOHC engines.

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RPM is rotation per minute of engine shaft when car is neutral. But when gear is engaged the RPM means the rotation of wheel per minute. 

I seriously doubt it. As fas as I know, RPM is rotation per minute of engine shaft, even if it is not in neutral.

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Overdrive gear: A gear that drives the vehicle faster than the engine.
Notchback: Booted version of the hatchback.

 

An overdrive will give you an additional gear above the normal high gear in a transmission. Its most common application is to reduce engine RPM on the highway, allowing less wear and tear, noise and improved fuel mileage.

 

In a notchback, the roof is abruptly dropped down to the leading part of the boot, also called Fast Back

 

My Request: Please google and confirm your posting and make sure it is informative and does not mislead.(not be taken in a wrong way)

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Another explaination for RPM

Revolutions per minute (abbreviated rpm, RPM, r/min, or r!?min−1) is a unit of frequency of rotation: the number of full rotations completed in one minute around a fixed axis. It is used as a measure of rotational speed of a mechanical component.

Standards organizations generally recommend the symbol r/min, which is more consistent with the general use of unit symbols. This is not enforced as an international standard. In French for example, tr/mn (tours par minute) is commonly used, and the German unit reads U/min (Umdrehungen pro Minute) or 1/min (= 1 min-1).

The corresponding unit in the International System of Units (SI) is hertz (symbol Hz) or s-1 (1/second). Revolutions per minute is converted to hertz through division by 60. Conversion from hertz to RPM is by multiplication with 60.

1 rpm = 1/min = 1/(60s) = 1/60 Hertz = 16.667 mHz

Another related unit is the SI unit for angular velocity, radian per second (rad!?s−1):

1 RPM = 2|D rad!?min−1 = 2|D/60 rad!?s−1 !O 0.10471976 rad!?s−1
cartoos2009-11-29 15:53:36

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