The Automotive Technicalities: How Stuff Works??
- Thread Starter TSIVipul
- Start date
Turbochargers are commonly used in passenger cars to obtain greater power output from a given engine size.
The compact nature of a turbocharger means it is often a more space-efficient solution for increasing power output than fitting a larger engine.
As an example, the turbo Porsche 944's acceleration performance was very similar to that of the larger-engine naturally aspirated Porsche 928.
There are Multiple Turbochargers
Twin-Turbo Parallel: A pair of turbochargers mounted to an Inline 6 engine in a dragster. Parallel Some engines, such as V-type engines, utilize two identically sized, each fed by a separate set of exhaust streams from the engine. Having two smaller turbos produce the same aggregate amount of boost as a larger single turbo allows them to reach their optimal rpm, more quickly, thus improving boost delivery. Such an arrangement of turbos is typically referred to as a parallel twin-turbo system.
The first production automobile with parallel twin turbochargers was the Maserati Biturbo of the early 1980s.
Sequential Turbo: Another twin-turbo arrangement is "sequential", where one turbo is active across the entire rev range of the engine and the other activates at higher rpm. Below this rpm, both exhaust and air inlet of the secondary turbo are closed. Being individually smaller they have reduced lag and having the second turbo operating at a higher rpm range allows it to get to full rotational speed before it is required. Such combinations are referred to as a sequential twin-turbo. Cars using sequential twin-turbos include the Porsche 959, Mazda RX-7, Toyota Supra and Subaru Legacy.
Sequential twin-turbos are usually much more complicated than a single or parallel twin-turbo systems because they require three sets of intake and waste gate pipes and valves to control the direction of the exhaust gases.
Triple-Turbo:The head of BMW's M division has stated that the next BMW M3 will be powered by a triple-turbo six cylinder engine.
Quad-Turbo:The Bugatti Veyron uses a quad-turbo W16 engine. The Bugatti EB110 from 1991 uses a quad-turbo V12.
The compact nature of a turbocharger means it is often a more space-efficient solution for increasing power output than fitting a larger engine.
As an example, the turbo Porsche 944's acceleration performance was very similar to that of the larger-engine naturally aspirated Porsche 928.
There are Multiple Turbochargers
Twin-Turbo Parallel: A pair of turbochargers mounted to an Inline 6 engine in a dragster. Parallel Some engines, such as V-type engines, utilize two identically sized, each fed by a separate set of exhaust streams from the engine. Having two smaller turbos produce the same aggregate amount of boost as a larger single turbo allows them to reach their optimal rpm, more quickly, thus improving boost delivery. Such an arrangement of turbos is typically referred to as a parallel twin-turbo system.
The first production automobile with parallel twin turbochargers was the Maserati Biturbo of the early 1980s.
Sequential Turbo: Another twin-turbo arrangement is "sequential", where one turbo is active across the entire rev range of the engine and the other activates at higher rpm. Below this rpm, both exhaust and air inlet of the secondary turbo are closed. Being individually smaller they have reduced lag and having the second turbo operating at a higher rpm range allows it to get to full rotational speed before it is required. Such combinations are referred to as a sequential twin-turbo. Cars using sequential twin-turbos include the Porsche 959, Mazda RX-7, Toyota Supra and Subaru Legacy.
Sequential twin-turbos are usually much more complicated than a single or parallel twin-turbo systems because they require three sets of intake and waste gate pipes and valves to control the direction of the exhaust gases.
Triple-Turbo:The head of BMW's M division has stated that the next BMW M3 will be powered by a triple-turbo six cylinder engine.
Quad-Turbo:The Bugatti Veyron uses a quad-turbo W16 engine. The Bugatti EB110 from 1991 uses a quad-turbo V12.
Thread Starter
#18
Thanks a lot buddy, looking it now..
Buddy the question was:
How are petrol engines turbocharged? Not, how different turbo setups work?
Buddy the question was:
How are petrol engines turbocharged? Not, how different turbo setups work?
First we should understand Super Charger working concept: The term supercharging refers to increasing the air density by increasing its pressure prior to entering the cylinder. This allows a proportional increase in the fuel that can be burned and hence raises the potential power output.
Three basics categories are used to accomplish this: The first is mechanical supercharging where a separate pump or compressor, usually driven by power taken from the engine, provides the compressed air.
The second method is turbocharging, where a turbocharger, a compressor and turbine on a single shaft, is used to boost the inlet air density.
The third method pressure wave supercharging, uses wave action in the intake and exhaust systems to compress the intake mixture.
The main advantage of turbocharging as opposed to supercharging is that turbocharging uses the energy in the exhaust gas that would have been lost. Supercharging uses power from the engine's crank shaft and thus less power is available for propulsion
Now come to your Point: Turbocharging Petrol engines - The petrol engine uses a carburetor or fuel injection system to mix air and fuel in the inlet manifold so that a homogeneous mixture is compressed in the cylinder.
In a petrol injection engine, the piston moves down and air is drawn through the intake valve and in a carburetor petrol engine, the air is mixed with petrol. As the piston moves back up, the air or petrol/air mixture is compressed.
After than the fuel/air mixture is ignited by a spark plug (in the diesel engine, fuel is injected under high pressure and the mixture ignites spontaneously) In either case, the explosion drives the piston downwards.The exhaust gas is expelled through the exhaust valve when the piston moves up. In a turbocharged engine, the air is pre-compressed before being supplied to the cylinder during the suction stroke. Because it is at a higher pressure, a greater mass of air is held in the combustion chamber, which means that fuel is burned more efficiently.
This increases the engine’s power output, giving more torque and a higher top speed compared to a normally aspirated engine of the same swept volume, and reduces emissions.
After than the fuel/air mixture is ignited by a spark plug (in the diesel engine, fuel is injected under high pressure and the mixture ignites spontaneously) In either case, the explosion drives the piston downwards.The exhaust gas is expelled through the exhaust valve when the piston moves up. In a turbocharged engine, the air is pre-compressed before being supplied to the cylinder during the suction stroke. Because it is at a higher pressure, a greater mass of air is held in the combustion chamber, which means that fuel is burned more efficiently.
This increases the engine’s power output, giving more torque and a higher top speed compared to a normally aspirated engine of the same swept volume, and reduces emissions.
I will try to answer some questions, I'm not an expert so I could be wrong, but it's something
How are petrol engines turbocharged?
In the same way that diesel engines, the difference is that on diesel you can put all the air you want on the combustion chamber, which is precompressed and when done, the fuel enters on the combustion chamber and is burned, as just the air is precompressed there is no risk of pre-detonation so you could reach higher compresion ratios that on petrol (17:1 v/s 11:1 commonly), on petrol engines you must put an amount of air in relation with the amount of fuel (14.7Lt of air per 1L of petrol if I'm not wrong), so it limits the amount of air you can put, and if you put more air it's NEEDED to put more fuel, and if you do that, you could reach a point where the fuel burns before the spark just because the temp on the combustion chamber (it's possible on petrol because the air enter with the petrol, on diesel engines the diesel enter after the air is compreses just before it has to be burned not before)
I have read somewhere that direct injection increases low end torque. How?
Direct injection as I know, produce a better distribution of the fuel in the combustion chamber, because the injector can spray it directly, so it take advantage in a better way of all the cylinder and the fuel burning is more efective
How is AWD system ran if the engine is transversely mounted?
I don't know much about it, but I guess when the engine is transversely mounted the central differencial (if it's present) has a different shape that allows to direct the engine power to the four wheels, it should not the differents, it's only needed to do more turns before reach the wheels
Basically in common rail technology, a single fuel pump is used. How it makes the engine more efficient as well as better performing than MPFi?
common rail is the MPFi on diesel engines, the design is almost the same that on petrol MPFi engines, it's a common tube (with fuel at high pressure) for all the injectors from where they obtain the fuel. Both are more efficient that the carb because you can adjust exactly the amount of fuel injected by information about the RPM and the fuel pressure on the system
I have heard that for optimum performance, the gear ratios should be set considering the power/torque vs rpm curve of the engine. How it is done?
Every engine has a power band, where it deliver it's best power/torque. As I know, if you need power you need to be between the max torque RPM and max power RPM, below and above this the engine loose too much power and it gets slow. The point of max efficience of the engine is at torque RPM, if you could travel at this RPM it's the best way to save fuel, but it you NEED that amount of power, what it means? probably if I need to travel at 80km/h in an engine with torque at 3000RPM, probably on 4th gear the engine will be at 3000RPM and it's the max efficient point but I need to mantain the engine at that rotating speed so I loose energy by friction, and in 5th gear probably the engine will be at 2400RPM, where the efficiency is not max, but with the power delivered at that range is more that enough for mantain that speed, and as it's rotating slower, I loose less fuel and it has fewer cycles so I need less fuel to inject. It's just a thing of power needed for what you want to do, in the same engine and the same speed, for overtake you must be on 4th gear, for have more power, and because on 2400RPM the engine is not efficient and you loose fuel by trying to produce power at that speed. Remember that those values are obtained with the engine at full throttle, we don't travel at full throttle, at least all the time..
What are these low rolling friction tyres, how do they work? In fact how are they different from our regular tyres?
Tyres always loose energy by touching the road and low friction tyres just have a different thread on the design that allows to loose less energy by touching the road. The problems of this is I guess it must affect the grip of the car, at least a little, but nothing considerably. I don't think it can save more that 1-2% of fuel, so I think you could lose that amount of grip (almost nothing)
what are the differences in different fuels like petrol, diesel, LPG and CNG?
between petrol an diesel I explained it on the first question, if any doubt just ask, I will try to do my best. About LPG and CNG I don't know too much, but the way they are burned is similar to petrol, needing an amount of air in relation to the amount of fuel, but I think it's efficiency is below that the petrol, but as they are cheaper, it compensates..
Another problem of LPG and CNG is that they are dry fuels, so it can't lubricate a little the combustion chamber, and the engine will get old faster.
A bonus track: the diesel is a little oily so it can lubricate in a better way the combustion chamber and protect the rings, also as they have torque at lower RPM, they rotate less times that a petrol engine, so it life is longer. That's the reason why truck engine could do that amount of kms.
what will happen if use different fuel than the expected one [diesel in case of petrol and vice-verse, LPG in case of CNG and vice-verse]
using diesel on petrol engine usually don't damage the engine, but it doesn't start, so you have to clean the tank. using petrol on diesel is more dangerous, but usually don't start neither. between LPG and CNG I don't know =P
why only petrol vehicle can be converted to LPG and why not diesel engine
because the way that the fuel is burned, LPG need a spark to ignite the mix of air and fuel just the same as the petrol, on diesel the fuel is ignited by the compression and the temp of the combustion chamber (just the thing should not happen on petrol engines). Also that fuels will not support that compression ratio and amount of air presents on diesel engines
why only LPG can be replaced petrol not CNG?
they are different fuel, LPG is propane and CNG is natural gas, and as I know both can replace petrol, but for CNG you need to mod the ECU and some parts of the engine for reach a good combustion, so it's more complicated but possible.
"why diesel engines have more torque than petrol one"
Because the compression ratio, the higher amount if air that increase the pressure and because the construction of it's moving parts, bore is the size of piston on surface, and stroke how much it moves vertically, more stroke means more torque at low RPM but less max RPM, less stroke means less torque but allow to reach higher RPM, and power is torque multiplied by RPM so you can calculate, diesel engines has more stroke (torque at low) and petrol engine has less stroke (less torque but more RPM, so it can produce more HP), it's a little complicated but you can read more about that concepts, both determine the size of an engine on cc. As I can understand that, if you need move heavy thing like a truck you need torque, if you need max speed and acceleration you need power, but remember that power is determined by torque anyway.
How are petrol engines turbocharged?
In the same way that diesel engines, the difference is that on diesel you can put all the air you want on the combustion chamber, which is precompressed and when done, the fuel enters on the combustion chamber and is burned, as just the air is precompressed there is no risk of pre-detonation so you could reach higher compresion ratios that on petrol (17:1 v/s 11:1 commonly), on petrol engines you must put an amount of air in relation with the amount of fuel (14.7Lt of air per 1L of petrol if I'm not wrong), so it limits the amount of air you can put, and if you put more air it's NEEDED to put more fuel, and if you do that, you could reach a point where the fuel burns before the spark just because the temp on the combustion chamber (it's possible on petrol because the air enter with the petrol, on diesel engines the diesel enter after the air is compreses just before it has to be burned not before)
I have read somewhere that direct injection increases low end torque. How?
Direct injection as I know, produce a better distribution of the fuel in the combustion chamber, because the injector can spray it directly, so it take advantage in a better way of all the cylinder and the fuel burning is more efective
How is AWD system ran if the engine is transversely mounted?
I don't know much about it, but I guess when the engine is transversely mounted the central differencial (if it's present) has a different shape that allows to direct the engine power to the four wheels, it should not the differents, it's only needed to do more turns before reach the wheels
Basically in common rail technology, a single fuel pump is used. How it makes the engine more efficient as well as better performing than MPFi?
common rail is the MPFi on diesel engines, the design is almost the same that on petrol MPFi engines, it's a common tube (with fuel at high pressure) for all the injectors from where they obtain the fuel. Both are more efficient that the carb because you can adjust exactly the amount of fuel injected by information about the RPM and the fuel pressure on the system
I have heard that for optimum performance, the gear ratios should be set considering the power/torque vs rpm curve of the engine. How it is done?
Every engine has a power band, where it deliver it's best power/torque. As I know, if you need power you need to be between the max torque RPM and max power RPM, below and above this the engine loose too much power and it gets slow. The point of max efficience of the engine is at torque RPM, if you could travel at this RPM it's the best way to save fuel, but it you NEED that amount of power, what it means? probably if I need to travel at 80km/h in an engine with torque at 3000RPM, probably on 4th gear the engine will be at 3000RPM and it's the max efficient point but I need to mantain the engine at that rotating speed so I loose energy by friction, and in 5th gear probably the engine will be at 2400RPM, where the efficiency is not max, but with the power delivered at that range is more that enough for mantain that speed, and as it's rotating slower, I loose less fuel and it has fewer cycles so I need less fuel to inject. It's just a thing of power needed for what you want to do, in the same engine and the same speed, for overtake you must be on 4th gear, for have more power, and because on 2400RPM the engine is not efficient and you loose fuel by trying to produce power at that speed. Remember that those values are obtained with the engine at full throttle, we don't travel at full throttle, at least all the time..
What are these low rolling friction tyres, how do they work? In fact how are they different from our regular tyres?
Tyres always loose energy by touching the road and low friction tyres just have a different thread on the design that allows to loose less energy by touching the road. The problems of this is I guess it must affect the grip of the car, at least a little, but nothing considerably. I don't think it can save more that 1-2% of fuel, so I think you could lose that amount of grip (almost nothing)
what are the differences in different fuels like petrol, diesel, LPG and CNG?
between petrol an diesel I explained it on the first question, if any doubt just ask, I will try to do my best. About LPG and CNG I don't know too much, but the way they are burned is similar to petrol, needing an amount of air in relation to the amount of fuel, but I think it's efficiency is below that the petrol, but as they are cheaper, it compensates..
Another problem of LPG and CNG is that they are dry fuels, so it can't lubricate a little the combustion chamber, and the engine will get old faster.
A bonus track: the diesel is a little oily so it can lubricate in a better way the combustion chamber and protect the rings, also as they have torque at lower RPM, they rotate less times that a petrol engine, so it life is longer. That's the reason why truck engine could do that amount of kms.
what will happen if use different fuel than the expected one [diesel in case of petrol and vice-verse, LPG in case of CNG and vice-verse]
using diesel on petrol engine usually don't damage the engine, but it doesn't start, so you have to clean the tank. using petrol on diesel is more dangerous, but usually don't start neither. between LPG and CNG I don't know =P
why only petrol vehicle can be converted to LPG and why not diesel engine
because the way that the fuel is burned, LPG need a spark to ignite the mix of air and fuel just the same as the petrol, on diesel the fuel is ignited by the compression and the temp of the combustion chamber (just the thing should not happen on petrol engines). Also that fuels will not support that compression ratio and amount of air presents on diesel engines
why only LPG can be replaced petrol not CNG?
they are different fuel, LPG is propane and CNG is natural gas, and as I know both can replace petrol, but for CNG you need to mod the ECU and some parts of the engine for reach a good combustion, so it's more complicated but possible.
"why diesel engines have more torque than petrol one"
Because the compression ratio, the higher amount if air that increase the pressure and because the construction of it's moving parts, bore is the size of piston on surface, and stroke how much it moves vertically, more stroke means more torque at low RPM but less max RPM, less stroke means less torque but allow to reach higher RPM, and power is torque multiplied by RPM so you can calculate, diesel engines has more stroke (torque at low) and petrol engine has less stroke (less torque but more RPM, so it can produce more HP), it's a little complicated but you can read more about that concepts, both determine the size of an engine on cc. As I can understand that, if you need move heavy thing like a truck you need torque, if you need max speed and acceleration you need power, but remember that power is determined by torque anyway.
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Excellent thread Vipul. Rated 5 star.
* How petrol engines are turbocharged?
Juan has explained it well. As far as I know, petrol engines are supercharged (correct me if I am wrong). Its similar to turbocharging. Difference lies in its drive. While turbocharger is powered by engine exhaust, supercharger is driven by engine itself or a motor. So unlike exhaust gas turbos, superchargers have immediate response.
* Common rail technology is used in diesel engines, while MPFI is for petrol engines.
Earlier, in diesel engines each unit used to have its own pump. And this pump was driven by a camshaft. So they used up a part of engine power. But in common rail system, a single pump is used to feed all the units. And because of automation, we have better control on timing. So commonrail system is more efficient than earlier system.
Sethu sir's queries
1. Rightly answered by Vipul
2. Petrol engine uses more volatile fuel. So lower compression pressure and spark ignition. While diesel engines use lesser volatile fuel and achieve combustion temperature by imparting higher compression pressure.
3. If we use diesel in petrol engine, it wont fire. And if we use petrol in diesel engine, it will detonate.
4. and 5. depends on the reasons above. To explain better, I need to brush up my knowledge a bit.![[:)]](https://www.theautomotiveindia.com/forums/images/smilies/Smile.gif "Smile [:)]")
Juan, Jaydev and Vipul have already answered most of the queries in detail though.
@ Robin your last post (#19) is hard to understand. Too much of irrelevant information..
* How petrol engines are turbocharged?
Juan has explained it well. As far as I know, petrol engines are supercharged (correct me if I am wrong). Its similar to turbocharging. Difference lies in its drive. While turbocharger is powered by engine exhaust, supercharger is driven by engine itself or a motor. So unlike exhaust gas turbos, superchargers have immediate response.
* Common rail technology is used in diesel engines, while MPFI is for petrol engines.
Earlier, in diesel engines each unit used to have its own pump. And this pump was driven by a camshaft. So they used up a part of engine power. But in common rail system, a single pump is used to feed all the units. And because of automation, we have better control on timing. So commonrail system is more efficient than earlier system.
Sethu sir's queries
1. Rightly answered by Vipul
2. Petrol engine uses more volatile fuel. So lower compression pressure and spark ignition. While diesel engines use lesser volatile fuel and achieve combustion temperature by imparting higher compression pressure.
3. If we use diesel in petrol engine, it wont fire. And if we use petrol in diesel engine, it will detonate.
4. and 5. depends on the reasons above. To explain better, I need to brush up my knowledge a bit.
Juan, Jaydev and Vipul have already answered most of the queries in detail though.
@ Robin your last post (#19) is hard to understand. Too much of irrelevant information..
petrol engines can be turbocharged or supercharged, both have pros and contras, but it's possible by the two ways ;). And as you say turbocharger uses exhaust gas to move the compressor and the supercharger uses a band to the engine to do that
Supercharger has a wider range of RPM where they work but uses a considerably amount of engine power to make the compressor work, and turbocharger are more efficient because they don't make load to the engine, the problem is that their range of work is narrow and usually at high RPM only.
Which use depend on the engine, on big engine with lots of power you can use a supercharger because you have power to move the compressor and it will give you more power (but lossing efficiency), on smaller of less powerful engine you must use a turbocharger because it don't make mechanical load to the engine and anyway will give you a good boost.
Something I forget to say on how turbocharge, is that when you put a turbo on a petrol engine as you increase the amount of air you should change the amount of fuel for make the air-fuel ratio efficient, so you have to change the config on your carb or ECU to increase the fuel injected, I have read somewhere that ECUs allows a ~20% of changes without problems thanks to all the sensor it has, so you could increase in 20% the amount of air without the need of mod the ECU, but beyond that you will have more work to do..
Supercharger has a wider range of RPM where they work but uses a considerably amount of engine power to make the compressor work, and turbocharger are more efficient because they don't make load to the engine, the problem is that their range of work is narrow and usually at high RPM only.
Which use depend on the engine, on big engine with lots of power you can use a supercharger because you have power to move the compressor and it will give you more power (but lossing efficiency), on smaller of less powerful engine you must use a turbocharger because it don't make mechanical load to the engine and anyway will give you a good boost.
Something I forget to say on how turbocharge, is that when you put a turbo on a petrol engine as you increase the amount of air you should change the amount of fuel for make the air-fuel ratio efficient, so you have to change the config on your carb or ECU to increase the fuel injected, I have read somewhere that ECUs allows a ~20% of changes without problems thanks to all the sensor it has, so you could increase in 20% the amount of air without the need of mod the ECU, but beyond that you will have more work to do..
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Thread Starter
#23
Thanks a lot for clearing this friends, so finally I got it that how turbocharging in petrols is different from diesels.
Next query:
What are the dynamic pros and cons of having fatter than prescribed rubber(tires)?
Next query:
What are the dynamic pros and cons of having fatter than prescribed rubber(tires)?
Having wider tires helps grip the car better and ensures better cornering. It also makes the car more stable and planted. But it affects the mileage slightly because the car now has more friction to deal with and it also has more road noise because of the same reason.
Thread Starter
#25
Okay guys, here is a new one:
I have got to know that there is nothing called 'twin turbo' under the hood of Quanto, it's a twin scroll turbo instead.
Can anyone verify the same and explain this twin-scroll turbo in simple words?
I have got to know that there is nothing called 'twin turbo' under the hood of Quanto, it's a twin scroll turbo instead.
Can anyone verify the same and explain this twin-scroll turbo in simple words?
Metric Thread designation requirement
Hi all,
I would like to know, the designation for M8X1.25-R, In this what R means?
I tried a lot to find out the detail. But i couldn't get it.
If someone can help me. it will be helpful.
Hi all,
I would like to know, the designation for M8X1.25-R, In this what R means?
I tried a lot to find out the detail. But i couldn't get it.
If someone can help me. it will be helpful.
Re: Metric Thread designation requirement
HI Vignesh,
Welcome to TAI
"R" denotes "Right Hand" and "L" for Left.
Regards.,
HI Vignesh,
Welcome to TAI
"R" denotes "Right Hand" and "L" for Left.
Regards.,
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Re: Metric Thread designation requirement
Thank you Mr.Kiran, But it will be denoted like RH or LH...correct me if i am wrong.
Thank you Mr.Kiran, But it will be denoted like RH or LH...correct me if i am wrong.
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Re: Metric Thread designation requirement
Kiran is correct. It is applicable to Rod Ends, not simple screws. You can check examples in 1st and 2nd Tables at this link https://www.pegasusautoracing.com/productselection.asp?Product=3067
Kiran is correct. It is applicable to Rod Ends, not simple screws. You can check examples in 1st and 2nd Tables at this link https://www.pegasusautoracing.com/productselection.asp?Product=3067
Last edited by a moderator: