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Turbo: Choose the right turbocharger


You can discuss and calculate which damper is suitable for the moment, which wheel angles to use, or whether you should use rain slicks or not before a race. Unfortunately, these areas are very diffuse and difficult to manage. Choosing a turbo unit is also an advanced subject if you don't have the correct data. We're going to walk you through the steps on how to figure this out now!

Choosing compressor wheels is easy because once you know how much power you want, you convert the power (hp) to airflow (cfm). Manufacturers of turbochargers even state how much power the turbo compressor can handle. On the other hand, the turbine side is more difficult because there are no good real-life examples like compressor maps available. See more information about turbine housing here.

Now we look at how to do it!

  1. How to choose the right turbo?
  2. The different parts of the turbo
  3. Convert horsepower to airflow (HP to CFM)
  4. What turbocharger do others use? 

Keep it simple. The choice of turbocharger is really easy with the right data. The hard part is finding the right data. Therefore, it is good to combination to see what has actually worked for others with the data you have obtained yourself. Now we have more information to back up our choice!



How to choose the right turbo?

In order to know which turbo to use, there are three very simple things to take into account:

Engine volume
Max horsepower

Engine volume and maximum RPM indicate which turbine part (turbine wheel and turbine housing) to be used. Max horsepower tells you which compressor (compressor wheel and compressor housing) should be used.

Choosing a compressor is easy as turbo manufacturers state this clearly. Simply choose the compressor that can handle the power you want. Read more about this further down under "Convert Horsepower to Airflow (HP to CFM)".

Choosing a turbine is more difficult, here you need to have a lot of data or simply see what has worked for others.

Size of turbine housing is usually measured in A/R or cm2. This is simply explained the space for exhaust gases that is in the turbine housing.
Larger space = Power higher up the power band and higher peak power.
Smaller space = Power further down the power band and lower peak power.

In addition to the size of the exhaust housing, the turbine wheel has a large part in what flow the exhaust side receives. A turbine wheel with 11 blades flows worse than one with 9 blades. Fewer blades give a worse spool but more space for the exhaust gases to pass through and thus cope with higher peak power. More blades give better spool but not as high peak power.

The Turbine's design is also of interest here. What is the angle of the blades, are all the blades the same size, what trim does the turbine wheel have.



The different parts of the turbo

If you dismantle the turbo in the simplest way, you get a compressor part, a bearing part and a turbine part. This is how we usually see turbo units in stores.

Compressor part = Compressor cover
Bearing part = The center part with the contents such as shaft, bearing, turbine wheel and compressor wheel
Turbine part = Turbine housing

When we have to choose a turbo for a certain application or power, we want to divide the turbo into 4 different parts as follows:

Compressor cover
Compressor wheel
Turbine housing
Turbine wheel
More information on turbo connections can be found here.



Convert horsepower to airflow (HP to CFM)

CFM = (fpm * area). FPM is Feet Per Minute and CFM is Cubic Feet per Minute. No, we will not calculate this, it easily gets wrong. We'll keep it simple. The turbo manufacturer has measured this and states this in theoretical horsepower that the turbo can handle and the airflow is included in the compressor map.

The manufacturers that do not distribute a compressor map are usually meant for an OEM application. Then this is already taken into account and no compressor map needs to be distributed to the public. The aftermarket, on the other hand, has compressor maps available and the data is clearly presented on the theoretical power and air flow that a turbo compressor can handle.

In other words, we see what the manufacturer states for theoretical max HP or CFM and if this is not presented, we have to rely on what works for others.



What turbocharger do others use?

When we know more about which data fits our engine, we want to confirm this by looking what turbochargers other people use.

Here we will present what turbo other people use on their engines and as we said before, there are many parameters to take into account in order to find the right compressor map and see which turbine to choose. By looking at what turbo has worked well for others, you can get a lot of help in choosing the right one. This can even be a decisive factor if weighing between two different turbochargers.


Audi 5cyl 20v

960hp / 1030nm Borg Warner S366 3bar E85 2,5L
850hp / 960nm Borg Warner EFR 8370 2,7bar E85 2,6L


BMW S38B36

980hp / 1230nm Borg Warner S369 2,2bar E85 3,6L


BMW M50B28

860hp / 940nm Borg Warner EFR 8374 1,9bar E85 2,8L



940hp / 1170nm Borg Warner EFR 9180 1,8bar E85 3,3L


Mercedes OM617

~250hp Holset HX30W Diesel


Nissan RB25

850hp / 790nm Borg Warner S374 2bar E85 2,5L


Toyota 2JZ

710hp / 980nm Borg Warner S366 2bar E85 3L
950hp / 1070nm Borg Warner EFR 9180 2,3bar E85 3L
1100hp / 1200nm Borg Warner EFR 9180 2,5bar E85 3,4L
800hp / 930nm Borg Warner EFR 9180 1,8bar E85 3L
1060hp / 1260nm Borg Warner EFR 9180 2,5bar E85 3L


 Volvo B230 8v

610hp / 810nm Garrett GTX3071R 2,5bar E85 2,3L
600hp / 810nm Holset Super HX40 2,4bar E85 2,3L
620hp / 800nm Holset Super HX40 2,1bar E85 2,3L
650hp / 790nm Holset Super HX40 1,8bar Etanol 2,5L
410hp / 550nm Garrett GT2871R 1,6bar E85 2,3L
500hp / 650nm Holset HX55 2,0bar BF98 2,3L


 Volvo B230 16v

700hp / 850nm Holset HX52 2,3bar E85 2,3L
760hp / 800nm Holset HX52 2,2bar E85 2,3L
600hp / 770nm Garrett GT40 2,0bar E85 2,3L


 Volvo T5 "white engine"

600hp / 780nm Garrett GTX3071R 2,2 bar E85 2,3L
480hp / 710nm Garrett GT3071R 1,4bar E85 2,3L
550hp / 680nm Holset Super HX40 1,8bar E75 2,3L
570hp / 700nm Holset Super HX40 1,6bar E85 2,3L
500hp / 650nm Holset HX35 1,5bar E85 2,3L
670hp / 780nm Garrett GT3582R  2,2bar E85 2,3L
519hp / 630nm Garrett GT3582R 1,7bar BF98 2,3L


Volvo T6 "white engine"

830hp / 1000nm Borg Warner S366 2,3bar E85 2,7L
850hp / 1040nm Borg Warner S366 2,4bar E85 2,9L