Compressor maps in a little more detail
ฝัง
- เผยแพร่เมื่อ 10 ก.ค. 2024
- One of our subscribers engaged with us in a great discussion about the technical aspects of efficiencies and related effects, we decided to do video to address this topic a little more (not comprehensively or completely) but to answer some questions that were posed. We will be releasing a multi part video series covering the complex topic of compressor maps and how ot plot on them in the coming weeks, but for now thanks B Berk for the comments, and great questions - hope this helps. Enjoy.
• Garrett G25-660 vs Bor... - ยานยนต์และพาหนะ
Mistake on the rotational speed on the plot posted in the G30-660 map at 2.5P2C - apologies this must read 125 000 rpm and NOT 170 000rpm - apologies guys.
I was about to call you out on that and tell you you don't know how to read a compressor map.
Man watching all these videos is definitely helpful in helping me choose the right turbo for my a4 quattro 1.8
Great to know - thanks Ziggy!
Compressor maps are an area I feel woefully uninformed and I know they're so important for properly picking a turbo. Thanks for all the info and I look forward to future videos. I keep sharing with friends. The few with courage enough to delve deep into these topics.
Since writing this comment I think I've leveled up quite a bit. Coming back now I understand far better. Compressor maps are no longer mysterious. What's confusing me now is the easy and correct way to plot expected paths on a map for given engine size, desired horsepower, and required boost to reach it. Seems you can come at it multiple ways.
For example, a 2.0L engine making 150HP stock. If I want to make 300HP by adding a turbo, the quick answer is I need to be at a 2.0 pressure ratio and hit 30lbs/min of air flow. Obviously that's at peak power RPM wise and could hold for a range, though I assume air flow has to go up slightly with RPM. To to plot other points on the map, is it easily possible to speculate without a full dyno graph? How do you reverse calculate at what RPM the engine won't produce enough exhaust energy to spool the turbo to make 1 bar of boost? Do you get what I mean? It seems no matter what there will be some guess work, though I understand with enough calculations you can likely get very close.
If we only think of a target such as 2.0 pressure ratio and 30lbs/min, we could pick any number of turbos which have that point in their peak efficiency island, but obviously we could choose a turbo too small that will choke a 2.0L engine and we could choose a turbo too large that takes forever to spool and actually hit 1 bar of boost. I think I get the basics of properly sizing a turbo and I can read a compressor map well, but some of these finer points on selection still make my mind go back and forth. Should I start with power goal, engine air flow NA, a dyno graph before changing or adding boost? The more I learn, the more I know I have not yet learned. I think I could at least get close to optimal!
As for the commenter's original question, I think I have a general answer. The reason the exact efficiency number does not matter is because even if there is 5% efficiency lost in compressing the air, at a given point on the map with the same pressure ration and air flow, you are still getting the same power from the turbo. If a less efficient turbo is hitting the same air flow at the same or lower boost level, then it does not affect the outcome in terms of power and feel. Basically, the efficiency of each turbo is related to its own parts and the sum thereof, not to the engine it is going on. If a turbo is making the same amount of power at the same boost level, what is the difference to you? Nothing, except if you fall outside of the surge or choke lines. Or if that turbo saved/cost you a lot of money, of course. Am I basically on the right track here?
Thanks as always for the great videos.
Thanks so much for all the info, we are learning so much more day by day. Pls keep it coming….
Thanks for the feedback - more to come.
How does this relate to exhaust flow? Does higher compressor efficiency mean less exhaust energy is required to do a given amount of compression? Turbine efficiency being equal.
In general I find there is a ton of information from both Borg and Garrett about compressor sizing, and almost nothing about turbine sizing. I got a spreadsheet I use for compressor calculations that is dead on for several cars, but I would really like to also calculate when the turbine will spool.
Thanks. Looking forward to more of your lecturing.
Thanks for the comments mate, the turbine side is very complicated and involves BSFC, EGT,s and alot of other formulae, its easier to use the matchbot (the best online match software available) for this - it shares everything from the AFR, to BSFC, expansion ratio etc which should inform you some on its own. Plotting a compressor is all about finding the right turbo for the job (drag, drift, street etc) then playing with the turbine housing AR choice, the spool characteristics are able to be manipulated.
It bothers me every time when trying to compare borg to garrett. Why is garrett multiplying x11 lbs/min to get their HP ratings? Seems like shady marketing. Should G30-G660 be called G30-600 or is EFR7670 a 715 not 650hp turbo?
On totally another subject. You mentioned in one of videos people run a flap, which below certain boost block one of the turbine scroll to help spool a "oversized" AR. Have you got any personal experience with it, maybe some back to back est on dyno. I found out about this channel couple days ago and I'm already subscribed and really enjoying contect.
Not many people with such broad knowledge are willing to share infos, which you do with passion. Keep on good work!
I know a dude who had that, it's better than nothing but less good than true twin scroll
As for hp ratings... welcome to marketing :)
You can get higher than 10 hp/lb depending on things like compression ratio and fuel type/timing. It's not as simple as 10 hp/lb, it's an estimate.
Loads of info, thanks Chris
Thanks Thys
I'm confused. The G30-660 doesn't even plot as high as 170,000 RPM anywhere on it's map. Where you're plotting 170,000 RPM is in fact more like 123,000 rpm. Maybe you should just double check those plots real quick.
Check the comments buddy - i put up a comment correcting this. We have been doing some plots for customers, and we copy and paste the text fields, and i overlooked the speed - sorry about that.
@@TurboDirectSA no worries, it's just your premise on cost of drive energy is integral to your slide showing such high numbers.
Simple mistake, no biggy.
Chris! I'm so glad you took me on with my all of my speculation about efficiency. I still don't understand why you can look at two compressor maps and (ignoring rpm) say that the less efficient one is flat out better though. I still see a discussion of everything except efficiency. Why do they bother labeling the islands?
I mean no offense by this, but I really think you're using your experience to justify your advice, and then using the maps as support. In fact, I wanna test enough turbos to really know what the hell makes a good one.
As for my car, it's primarily a street car, like I said, so the current intercooler is what I will live with. And I haven't pushed all the way to runaway IATs, but temps high enough that timing was pulled and I worried. I have no reason to really push because I'm not competitive and not trying to be. I'm forcing too much air through a small intercooler and getting high IATs, and I probably would be no matter the turbo I used. But why not try to push very slightly cooler air?
I am amazed that you keep answering my questions, but I'm not giving up. Pick a single point on the borg map and use only the 4 variables (pressure ratio, flow rate, efficiency, speed) to convince me that it's better than the garrett at that exact same point on its map.
Why do they bother labeling the islands?
Labelling an island proves to show information - this is why i would label them, im not sure what reply the manufacturer would provide to you but you would have to ask them that. My experience is something i keep to myself, unless its to expose fact, i will never force my experience on anyone - and the compressor map speaks for itself, no way can anyone manipulate this in any way - it is what it is.
All i outlined was printed, black on white fact - use it, lose it .... up to whoever is reading/watching the map/video respectively. Testing turbos is what we have been doing for 15 years + - which results in my experience, which is why when we provide advise to builders, and they use the advise, 99% of the time the owners are happy with the advise which meets their expectations - I can tell you this (from experience) if you tested back to back the EFR7163 against the GTX3071R (similar HP output and rotating assembly size diameters) you will find the following:- EFR is far cooler in temps (water temps, oil temps etc) faster spooling, more linear in response and power delivery, and the power result will marry up to the compressor map every time.
No it does matter what turbo you use, the intercooler is a heat exchanger, and if its out of spec temps will run away - yet if i remember correctly, you pointed toward the turbo as the culprit - which is not the case. This is why its so critically important to spec the setup properly BEFORE purchasing anything, so that you know what you in for - reputable companies, experienced personnel, and people who know what they are doing with experience, are what you should look for to seek guidance - I dont claim to know everything but i have some experience and know a little about the product we involved with, however if i get stuck i ask. Im not trying to convince you of anything - that you will have to do yourself.
I can however make a suggestion for you - purchase the Garrett turbo, you seem to be leaning more towards, and enjoy the car/build/project. Whether you like, dislike, purchase, either product is totally up to you. If you want information, based on fact written on black and white, ill help you where i am able to and share my experience with you, but ultimately, its your decision what you like, dislike, purchase or not.
@@TurboDirectSA First of all, if you were local I would come talk to you in person and I would send my dollars buying a turbo your way without a doubt. Your experience is priceless. I wish I could find a tuner near me that could talk through the turbo choice with me with the knowledge you have.
That said, I still haven't seen any explanation for what efficiency means. I said shaft work that goes directly towards compressing the air, the excess work mostly heats the air. Is that wrong?
@@bberk1286 Thanks Berk - thats not the only reason i do what i do - i have a passion for this and love seeing results, and obviously others get to gain from my experience, knowledge at the same time.
Wait for the upcoming videos on compressor maps, ill go into ALOT of detail step by step, and use a specific engine to plot on a few maps, which i will then use to install onto the specific engine and cross reference back to the map after a real life test on the dyno. For now the efficiencies are the "sweet spot" where the specific compressor operates at its most efficient (driven by a specific design turbine that is. For the mean time, dont worry about the figures on the map, look at the position of where your specific engine will plot, in the various RPM range you will be operating in.
What would you recommend to replace an APS SR40 turbo on an EJ207 Version 8 AUDM delivered so has factory forged pistons and rods, produced 368 awhp on the APS turbo and 412-20 ft/lbs torque I think from memory. Turbo comes on hard at about 3100rpm give or take and pulls solid until 6250rpm then drops off and has a dip at around 5000rpm of torque and power before rising again I think 3800 or something may be full boost which was around 30psi or at least 2bar gauge pressure. Haltech ecu controlled, fmic, aps intake intercooler, bov, and aps top feed and injection parallel fuel lines, I’m unsure of if it’d any work done internally as I bought it for a guy that didn’t really speak English well and I don’t think he knew anyway as he was the second owner. Any help on brand and sizing etc with possibilities to reach over 500awhp possibly without turbo coming in at 5000rpm and it’s just a weekend cruiser with no racing ambitions just like to drive it.
Hang fire for a few weeks - i have a video that we working on where we will swap out various options on the EJ257 (yes its a different motor to yours) which will give you a good idea on the expectations you can decide on.
How would you go about finding info on turbos from cars that you cant find info online? I have a turbo from a 1.4L diesel car and i want to use it in a 400CC 4Cyl motorcycle engine that it revs up to 12000rpm. Is there any way to find out before fiting the turbo? The 400CC engine at peak RPM will require about half the air flow of he 1.4L engine at 6000 RPM.
10:12 where do you get the 170000rpm figure? The point you've plotted and pointed to is UNDER the 130000rpm line. It's higher than the BW for sure, but nowhere near 170k RPM.
Thanks for the heads up here - this is in fact a mistake, apologies. At the 520HP the speed is around 140-142000rpm - if you max the turbos HP potential out, it reaches 165000RPM
So what's the purpose of running a turbo at higher boost levels? If efficiency islands are located lower on the Y axis would this cause the turbo to work less to produce that flow rate? Why would the compressor need to generate the same power at different boost levels? Wouldn't the idea be to generate as little boost as possible but increase flow rate? I am pretty sure that is what you alluded to when you made the Garrett comparison. I see why you can't look at boost to figure out what turbo to use the size of the turbo matters more and the compressor speed in relation to flow rate.
Thanks for the comment - purely limited and characterised by the engines ability to "use" the flow provided at the various boost levels. The fact that the higher boost levels, will 'force' more air into an engine with a lower VE (volumetric efficiency) to get it to produce more power, in comparison to an engine which is more efficient and is able to produce the same HP at lower boost levels as a result.
What application are you running that you want to spec a turbo for?
@@TurboDirectSA
All-around performance, not looking to make this into a drag car but would like to be competitive in roll race events or even take it out on the track and shake it down.
400 - 650hp range, on matchbot revving the engine out past 9k RPM's it will not pass the choke line at 12 PSI or roughly 72k RPMS of turbo speed with the EFR 8474.
I have honda k20a2
With factory pistons 11.0 cr made 225 on 93 pump at 8200. Rev limiter set to 8600
This set up is going into my 2002 RSX(DC5) type s. I am currently in the process of converting the drivetrain over to CRV components to be Awd at 400-650HP.
The engine is at the machine shop fully building the bottom end. 86.5mm bore and 86mm stroke. CP pistons (9.5 : 1), eagle rods. Ferrea valves, 80lb valve springs. S2k oil pump.
@@TheRobertChannel EFR8474 Black Series for sure - this is where i would go, and still keep some in reserve for later in case you decide to up the boost ---- which i know you will want to do. This will be capable of over 900HP on that motor once fully built.
A sweet 😋 hearty educational meal for the brain 🧠
the Garrett GT3582R
is 80% efficiency in 1 bar and 40 lb/min!!!
no turbo charger brand
have this efficiency?
thank you
79% at P2C off 2.0 (1.0bar gauge) and just touching 42lb/min -- very good product and a cast compressor wheel - this turbo made the claimed power in the day - GTX then stepped this up. When Garrett went bankrupt - their G-series product went downhill, both in quality and claimed output power.....
It would be awesome if you could compare the borg warner 7670 efr compressor map and the new 8370 compressor map in depth I could really benefit from it thanks.
Thanks Sam, ill do so in the coming videos.
@@TurboDirectSA sounds awesome I’m looking forward to it!🤘🏼
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 a big mystery for me. What 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.
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.
@@TurboDirectSA 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.
@@loverboy8476 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?
@@TurboDirectSA 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!
@@loverboy8476 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.