27-01-2015, 12:46 AM
Thought I'd just do a post explaining a few bits about turbochargers and what people mean when they talk about them as I know when I first started, it was horribly confusing.
- Compressor Wheel
The "Cold Side", "Intake Side", "Impeller" - this is the part that actually compresses the air to be delivered to the engine. General rule is bigger this component - more airflow - more power suppported.
- Turbine Wheel
The "Hot Side", "Exhaust Side" - this is the part that the exhaust gasses pass through to turn the turbine, which is linked to the compressor.
- Housing
Sometimes known as a "Compressor Cover" - the part that fits over the compressor or turbine, directing the airflow and accelerating the airflow in and out of the wheels.
![[Image: gt35r_comp_housing_2.jpg]](http://www.himni-racing.com/images/gt35r_comp_housing_2.jpg)
- Inducer
Both the compressor and turbine wheels have an inducer - however GENERALLY we talk about the inducer in reference to the compressor wheel, this affects how much air is drawn in by the compressor. Measured in mm normally, for example a BMW M57N 330d GT2260V has a 44.5mm inducer.
- Exducer
Again, both compressor and turbine have an exducer - however as with the inducer, we tend to talk about the exducer in reference to the compressor wheel. This measurement is in relation to the inducer size - generally the bigger the ratio between the inducer and exducer, the better the turbo is at sustaining higher pressures.
![[Image: Garrett_rotating_group_enlarged.jpg]](http://www.turbobygarrett.com/turbobygarrett/sites/default/files/turboTech/TurboTech-Advanced/Garrett_rotating_group_enlarged.jpg)
This explains the difference between inducer and exducer of a compressor wheel.
- Trim
This is a measurement that appears to be wholly misunderstood by anyone in Diesel land from experience, but is an incredibly important measurement. It is the relationship between the inducer and exducer of the compressor wheel - trim describes this as a number:
For example a GT2871R turbo has a compressor wheel with a 53.1mm inducer and a 71.0mm exducer. To calculate the trim from this - there is a formula:
Trim = (Inducer^2 / Exducer^2) * 100
So..
(53.1mm^2 / 71.0mm^2) = (2819.61 / 5041) *100 = 55.933544
Round that up gives us a trim of 56 - the bigger this number, the larger that ratio between the two. Generally this means that the bigger the number, the more air the wheel can move, but not always, other things will change that affect this!
- A/R
A/R or Area over Radius is a way of describing the housings design - the best way I can describe why this is important is by a really simple idea - imagine standing up a christmas card, grab a drinking straw and blow at the card - the card falls over. Now grab a drainpipe and do the same thing, try and make the card fall over - you can't! This is becuase your breath is being accelerated through the straw and is travelling quickly as it comes out the end, conversely the drainpipe the air barely moves...
Notice however that you had to put in a lot of effort to blow through the straw, you can blow harder and harder, but seemingly you can't get much more air to come out the end of the straw, the air is going a bit quicker, but you go red in the face and light headed. Conversely you seemingly can blow as hard as you want down the drainpipe, but you can barely get the gas going quick enough to even budge the card!
This is exactly what A/R describes - it's how small/big the "throat" into the turbine wheel or out of the compressor is - small being like the straw, big being like the drainpipe. The compressor is affected by A/R, however not to the same extent as the turbine wheel. The measurement is defined as "the inlet (or, for compressor housings, the discharge) cross-sectional area divided by the radius from the turbo centerline to the centroid of that area" - it's very difficult to measure, so we tend to go off the figures printed on the housings.
What you really need to know is that the bigger the number A/R - the larger the throat into the turbocharger.
![[Image: Garrett-Housing-AoverR.jpg]](http://www.turbobygarrett.com/turbobygarrett/sites/default/files/turboTech/TurboTech-Advanced/Garrett-Housing-AoverR.jpg)
This affects at what RPM the turbo is able to really start providing pressure to the engine, smaller the A/R, quicker the gas is going - it also affects at what RPM the exhaust side starts to become a restriction.
- VNT
Known as VNT or "Variable Nozzle Turbochargers" simply take the above explanation of A/R and cause that to be adjustable - meaning you have the best of both worlds, you can get your low RPM response from a small A/R, which would be a real restriction at high RPMs, but at high RPMs you can open the vanes and allow more air to move.
Enough for tonight - I need to go to bed. I'll do more tomorrow when I can't sleep
- Compressor Wheel
The "Cold Side", "Intake Side", "Impeller" - this is the part that actually compresses the air to be delivered to the engine. General rule is bigger this component - more airflow - more power suppported.
- Turbine Wheel
The "Hot Side", "Exhaust Side" - this is the part that the exhaust gasses pass through to turn the turbine, which is linked to the compressor.
- Housing
Sometimes known as a "Compressor Cover" - the part that fits over the compressor or turbine, directing the airflow and accelerating the airflow in and out of the wheels.
- Inducer
Both the compressor and turbine wheels have an inducer - however GENERALLY we talk about the inducer in reference to the compressor wheel, this affects how much air is drawn in by the compressor. Measured in mm normally, for example a BMW M57N 330d GT2260V has a 44.5mm inducer.
- Exducer
Again, both compressor and turbine have an exducer - however as with the inducer, we tend to talk about the exducer in reference to the compressor wheel. This measurement is in relation to the inducer size - generally the bigger the ratio between the inducer and exducer, the better the turbo is at sustaining higher pressures.
This explains the difference between inducer and exducer of a compressor wheel.
- Trim
This is a measurement that appears to be wholly misunderstood by anyone in Diesel land from experience, but is an incredibly important measurement. It is the relationship between the inducer and exducer of the compressor wheel - trim describes this as a number:
For example a GT2871R turbo has a compressor wheel with a 53.1mm inducer and a 71.0mm exducer. To calculate the trim from this - there is a formula:
Trim = (Inducer^2 / Exducer^2) * 100
So..
(53.1mm^2 / 71.0mm^2) = (2819.61 / 5041) *100 = 55.933544
Round that up gives us a trim of 56 - the bigger this number, the larger that ratio between the two. Generally this means that the bigger the number, the more air the wheel can move, but not always, other things will change that affect this!
- A/R
A/R or Area over Radius is a way of describing the housings design - the best way I can describe why this is important is by a really simple idea - imagine standing up a christmas card, grab a drinking straw and blow at the card - the card falls over. Now grab a drainpipe and do the same thing, try and make the card fall over - you can't! This is becuase your breath is being accelerated through the straw and is travelling quickly as it comes out the end, conversely the drainpipe the air barely moves...
Notice however that you had to put in a lot of effort to blow through the straw, you can blow harder and harder, but seemingly you can't get much more air to come out the end of the straw, the air is going a bit quicker, but you go red in the face and light headed. Conversely you seemingly can blow as hard as you want down the drainpipe, but you can barely get the gas going quick enough to even budge the card!
This is exactly what A/R describes - it's how small/big the "throat" into the turbine wheel or out of the compressor is - small being like the straw, big being like the drainpipe. The compressor is affected by A/R, however not to the same extent as the turbine wheel. The measurement is defined as "the inlet (or, for compressor housings, the discharge) cross-sectional area divided by the radius from the turbo centerline to the centroid of that area" - it's very difficult to measure, so we tend to go off the figures printed on the housings.
What you really need to know is that the bigger the number A/R - the larger the throat into the turbocharger.
This affects at what RPM the turbo is able to really start providing pressure to the engine, smaller the A/R, quicker the gas is going - it also affects at what RPM the exhaust side starts to become a restriction.
- VNT
Known as VNT or "Variable Nozzle Turbochargers" simply take the above explanation of A/R and cause that to be adjustable - meaning you have the best of both worlds, you can get your low RPM response from a small A/R, which would be a real restriction at high RPMs, but at high RPMs you can open the vanes and allow more air to move.
Enough for tonight - I need to go to bed. I'll do more tomorrow when I can't sleep
![[Image: 22f2b6b2-758b-4c1c-96fb-6fa9c6059b13_zpsf306b56b.jpg]](http://i585.photobucket.com/albums/ss299/Ha11elujaz0rs/22f2b6b2-758b-4c1c-96fb-6fa9c6059b13_zpsf306b56b.jpg)
![[Image: tapatalk_1427020983519_zpsnwvozlhb.jpeg]](http://s768.photobucket.com/user/annegg5511/media/Mobile%20Uploads/tapatalk_1427020983519_zpsnwvozlhb.jpeg.html)
