Hey guys,

I ended up in a debate for rather elementary stuff when it comes to compressor maps. I want an objective opinion I'm I unclear what I'm asking or saying. Misunderstanding is the only logical explanation for the debate with a guy from TurboDirect S.A who does youtube videos on turbos and who should know this stuff like his own pockets. I don't want give additional information from my side, so that's an even playing field.

I'm I on crack or he? The conversation is on youtube comments. But here's a copy-paste

Loverboy84

Any plans for the more in-depth series yet? It would be highly appreciated. It feels that you're oversimplifiying and it doesn't therefore click for me as I need to understand the big picture. But I get it, if the bulk of the audience is interested only the broad strokes. The compressor effiency is still big a mystery for me. What's is the theoretical and practical difference between compressor when pr is the same, mass flow is the same, rpm is the same but efficiencies are the discussed 74% and 79%. Does it mean that one turns 26% and the other 21% for the energy of the turbine wheel into heat and this is shown directly in the IAT? Also if this equation would be correct the other engine needs to have a little bit bigger displacement so that it can make up the less dense air? Thanks for the great videos.
1
TurboDirect S.A
4 days ago
Keeping it simple (it will run away from most) efficiency is the result of a said amount of work done. So a compressor that rotates at a specific speed, produces a certain amount of boost pressure and flows a certain amount of air volume. Comparing one compressor to another it is safe to say that the work done is the volume of air flow being generated. Therefore if one wheel produces more air flow (more work) than the other at the same boost pressure (P2C ratio) then this wheel is doing more work. Now if the wheel doing the most work is the same size (inducer and exducer) or operates in the same family (HP output, frame size etc) then is it safe to say that this wheel is more efficient? (ignore the percentage number - this is an outline of the work being done by the compressor in relation to its driving turbine, and not compared to another wheel) My point is simple - the Borgwarner air flow of the same size/family/HP derivative is higher than the Garrett at the same boost pressure (P2C) BUT at a lower speed -- which makes the Borg more efficient. It takes less RPM at the same boost pressure to outflow the Garrett, which requires more speed and boost to match the airflow of the Borg.

Loverboy84

3 days ago
@TurboDirect S.A Thanks for your response. What about the hypothetical situation that i presented. Regarding the conservation of energy. The work applied to the compressor wheel has to go 100% to somewhere, it cannot disappear. So when all things equal except the compressor efficiency what is the outcome? Higher IAT and therefore the engine has to have higher displacement or it needs to have higher rpm to facilitate the less dense air, so that we can have exactly identical operation points between the compressor charts. If my deduction is correct, then I understand compressor efficiency and its effect for matching a turbo in a level that is profoundly enough for me.

TurboDirect S.A
3 days ago
@Loverboy84 IAT are a result of the work done by the compressor - hense the requirement for an intercooler. IAT has nothing to do with or affects in any way the adiabatic efficiency of the compressor wheel and its design. Work done -- by what? Work done by the compressor - this is obvious. Driving force by the energy brunt in the engine is routed out the engine through the turbine housing - this drives the rotating assembly, and escapes out the exhaust system - this is the physical routing. How much "work done" by the turbine is solely dependant on the engine and its state/tuning/fuel/ability to convert fuel to mechanical energy --- its Volumetric efficiency. Displacement is irrelevant - bigger engine with an incorrectly sized (application specific/dependant) turbocharger will perform differently to an engine with a larger turbo .... boost levels will affect both efficiencies on both the turbo and engine - Is there are specific question you want some light shed on?
1

Loverboy84

2 days ago (edited)
@TurboDirect S.A Thanks for your response. It rose a lot of questions. We might have a little misunderstanding going on, so let me use some arbitrary numbers to avoid misunderstandings. Turbine side and intercooler are irrelevant when talking about compressor efficiency, so when can ignore them. We have an electric motor that spins the compressor wheels and the process is assumed adiabatic. A) We have two compressor wheels with 70% and 80% efficiencies. Following conditions are applied for both. Compressor wheel rpm 100krpm pr 2bar Mass flow 400lbs/min My hypothesis is that there is a temperature difference between the compressors’ air temperatures and the power that the electric motor requires. The power from the electric motor converts into pressure, mass flow and temperature. Some of the energy will convert into heat inherently, we are not interested that part because it is a thermodynamic law. In order for the better compressor (80%) to produce 10kW, it takes 10kW/0,8 = 12,5kW and for the worse compressor (70%) to produce 10kW, it takes 10kW/0,7= 14,3 kW. The extra (14,3kW-12,5kW) = 1,8kW, is directly shown in the temperature. 70% efficiency has higher IAT. B) Now we would have a situation where we have the same pr (2) and the same mass flow (400lbs/min) but difference in temperature and therefore difference in volumetric flow, let say 80% compressor produces 90m3/min and 70% compressor 100m3/min When using better 80% compressor in a 2.0 litre, 400 flywheelhp (400lbs/min) producing engine is running at 5000rpm and it consumes 90m3/min of air. When using the worse 70% compressor in a 400 flywheelhp (400lbs/min) producing engine is running at 5000rpm you need to increase the displacement ~11% from 2.0 into 2.2 litre because the engine consumes 100m3/min of air instead of 90m3/min. Hopefully this clarified what I was asking. So if you can comment why A and B are wrong, or was it just a misunderstanding? Thanks for you time!

TurboDirect S.A
2 days ago
@Loverboy84 temperature has nothing do with the electric motor - the electric motor has nothing to do with a turbine wheel, mass flow, pressure ratio, AR of the housing and we not even talking about EGT's, calorific value of fuel, AFR, etc. Compressor efficiency is simple - how much work is being done by the compressor at what pressure, and how fast does this need to rotate to accomplish this. as explained above. Electric motors do not operate nor resemble a turbine stage at all - so cannot be compared in any way im afraid.

Loverboy84

2 days ago (edited)
@TurboDirect S.A "temperature has nothing do with the electric motor - the electric motor has nothing to do with a turbine wheel, mass flow, pressure ratio, AR of the housing and we not even talking about EGT's, calorific value of fuel, AFR, etc. " Hmmm... The electronic motor was just a proxy, because it feels that there is still a huge misunderstanding between us because I'm asking something and in your response is answering to a different question and giving the impression that I've presented something that I haven't. Like above. I believe I was was really clear that we can disregard the turbine side because the compressor wheel doesn't care what makes it spin. I thought that we would avoid confusion if we but just an electric motor there. Then the situation is somewhat realistic. Turbine wheel, EGT's fuel, AFR etc. doesn't have anything to do with compressor efficiency, therefore we can ignore them unlike pr and mass flow. "Compressor efficiency is simple - how much work is being done by the compressor at what pressure, and how fast does this need to rotate to accomplish this. as explained above. " Yes, you have said this multpile times, but that is not what I'm asking. Please read A) again. Are the IAT's identical? Literary and my deductions say no. What is your stance? "Electric motors do not operate nor resemble a turbine stage at all - so cannot be compared in any way im afraid." At steady state they do. Manufacturers plot the diagrams at steady state. This isn't a transient situation. I don't want to come out as rude and disrespecteful, you make great content and I really appreciate your time anwering a keyboard warriors like myself. I have a master's degree in energy technology and you had an interesting way to describe compressor effiency. So I wanted to know if there is something that I don't know. Maybe turbocharger compressor effiency is calculated differently than how it is normally calculated, which I severely doubt. But I wanted to ask a professional whose bread and butter this stuff is and maybe learn something new.

TurboDirect S.A
2 days ago
@Loverboy84 Unfortunately its not possible to dissect the manner in which a turbo operates. The turbine is critical to the compressors operation and efficiency - changing the AR on the turbine side - has a direct effect on the compressors ability to rotate, https://www.borgwarner.com/matchbot/ Visit the above and have a look at the turbine settings on the page - play with some of the settings and you will see that a simply AFR change, moves the plot points on the compressor. Hence my video keeping the explanation simple as possible - because this is exactly what happens when you delve into this subject. There are things which i will not divulge in the arrangement for obvious reasons, but the basic outline is something i have covered in my video and few others on the channel. The topic is hugely technical and in depth, and most viewers arent able to grasp this as the understanding requires a background in various other highly technical subjects in order to combine together to form the complete picture.

Loverboy84

1 day ago (edited)
@TurboDirect S.A That matchbot seems awesome. I will play with that for sure! Thanks for the tip. I will have to disagree with you that you can't make theoretical review between isolated compressors from rest of the turbo. AFR or A/R of the turbine side doesn't change the compressor map, it changes the operation point. There is a significant difference. Apples and oranges once again. Compressor efficiency is just one factor that you have to consider when picking the most suitable turbo for your application. Money being probably the biggest factor. :D Hopefully you will make more in-depth videos series about compressor efficiency to shed some light into the topic, so that I would better understand your point of view. Thanks for your time.

TurboDirect S.A
1 day ago
@Loverboy84 I think once you have played with matchbot - you will understand that in fact ANYTHING you change on the turbine side, has a direct effect on the compressor plot - ofcourse it will, because this is what drives the compressor.

Loverboy84

1 day ago
@TurboDirect S.A I'm really excited about that matchbot. Can't wait to get to home and play with it. Hopefully it clarifies things. Thanks again.

TurboDirect S.A
1 day ago
@Loverboy84 Pleasure buddy - happy to help.

Loverboy84

1 day ago (edited)
@TurboDirect S.A I spent some time with the matchbot, and like I said, NOTHING you change on the turbine side have any effect on the compressor map. If you want to change the compressor map you would have to have a compressor with variable geometry. The compressor map and its efficiency islands are fixed. That is an indisputable fact. Like I said earlier: "I will have to disagree with you that you can't make theoretical review between isolated compressors from rest of the turbo. AFR or A/R of the turbine side doesn't change the compressor map, it changes the operation point. There is a significant difference. Apples and oranges once again." ANYTHING you change on the turbine side has a direct effect to the operation point (please read above). You can prove me wrong, by pointing which one of these parameters have an affect to the compressor map, not the operation point on the map, the actual compressor map which has been the topic of this conversation. Displacement Ambient Air Temp Altitude Fuel Type Engine Speed Volumetric Efficiency Boost Pressure (Gauge) Intercooler Effectiveness Intercooler Pressure Drop Air Filter Restriction Muffler System Backpressure Compressor Efficiency Turbine Efficiency Exhaust Gas Inlet Temperature Turbine Expansion Ratio BSFC A/F Ratio It's more and more evident that you're talking about the turbocharger's efficiency the whole time, while I'm trying to discuss about the compressor efficiency. IRL what happens on the turbine side will affect the compressor efficiency by changing the operation point. I believe you are talking about this? - From a passionate guy to another

TurboDirect S.A
1 day ago
@Loverboy84 Sorry i disagree - change the fuel, AFR or turbine expansion and watch the plots move.

Loverboy84

23 hours ago (edited)
@TurboDirect S.A I never said the operation points (plots) wouldn't move. I unambiguously stated that THEY WOULD (read quotes below), so don't know with whom you're disagreeing with. I'm sorry but I really don't understand your response. "AFR or A/R of the turbine side doesn't change the compressor map, it changes the operation point. There is a significant difference. Apples and oranges once again." "You can prove me wrong, by pointing which one of these parameters have an affect to the compressor map, not the operation point on the map, the actual compressor map which has been the topic of this conversation" I can do a video on the weekend, that shows that changing fuel, AFR or turbine expansion doesn't change the compressor map.

Loverboy84

23 hours ago
@TurboDirect S.A If you have an industrial radial compressor that is run by electric motor. The manufacturer has a compressor map for their product. Now if you modify the compressor that it's been run by exhaust gas, will it change the compressor map? I'm saying no. What do you say?

TurboDirect S.A
21 hours ago
@Loverboy84 Not sure what your question is from the start - also not in the business of proving anything or anyone right or wrong --- not sure what you mean there with this comment either. You clearly dont understand the relationship between the turbine and compressor stages - unless you have a question im simply not understanding what you are trying to understand/asking. Not possible to "teach" you in a text joust on youtube im afraid.

TurboDirect S.A
21 hours ago
@Loverboy84 How long is a piece of string is what i can say in reponce to your question. Running an industrial compressor (which is totally unrelated in every way to a turbocharger designed compressor) to be driven by exhaust gas --- what pressure ratio, what gas, what temperature, in what housing, with what volume, what gas loading, turbine expansion ratio, and what velocity/mach speed..... And the questions go on -- hence BorgWarners Matchbot exists to answer these questions for you.