I agree. It's now a topic that I'm staying to research into (how to correctly size a turbo for your application), and this video was the perfect introduction to it. Only disappointing thing is at the end he mentions that for further information there is more info available online, but some links or suggestions for good sources of information would be helpful

+whatdaf11 These are a complex subjects with numerous variables and caveats. My suggestion to be successful is to get a good grasp of thermodynamics, fluid mechanics, fluid-dynamics and gas laws first. Here are a few good turbo specific places to start... garrett.honeywell.com/ www.turbobygarrett.com/turbobygarrett/ www.turbobygarrett.com/turbobygarrett/boostadviser www.turbobygarrett.com/turbobygarrett/compressor_maps www.enginelogics.com/read-a-turbo-compressor-map/ www.enginebasics.com/Advanced%20Engine%20Tuning/AR%20turbo%20ratio%20explained.html www.google.com/search?num=100&newwindow=1&q=how+to+correctly+size+a+turbocharger&oq=how+to+correctly+size+a+turbo&gs_l=psy-ab.1.0.0i22i30k1l2.143921.160184.0.169847.24.23.1.0.0.0.426.2516.16j6j4-1.23.0....0...1.1.64.psy-ab..0.24.2517...0j0i20k1j0i13k1j33i22i29i30k1j0i13i30k1.FSud9yGj0qs

That assumes output pressure has remained unchanged

Yes I'm saying he errored at 1:17.

oh gotcha

Yep. I agree.

no, he still said 1 bar BOOST. not an absolute output pressure. so 1 bar in and 1 bar boost = ratio of 2...0 .9 bar in and 1 bar boost is 1.9 bar ratio of 1.9 i.e less...

well it's important for the engine power but the talk in the video is about the turbo efficiency itself.

jack black I believe he said it was a basic idea of how it works, he's not going to do a uni course on explaining it.... Find an engineering explained video if you want that

You can write books about this shit. Actually, Corky Bell and many others already have! Can't expect him to answer it all, we'd be here for hours.

jack black Agree. As the others have said, this is a very complicated topic, and way more than you could expect to cover in a short You tube video. But at the very least i would have liked to see him explain how to calculate the estimated air mass consumption of a engine for a given RPM and boost. Without this piece of info, looking at compressor maps is basically a waste of time. But once you have calculated the estimated air requirements of your engine. You can then plot that data over the top of a compressor map. And this will fairly accuaretly be able to tell you how the turbo would be expected to perform on your engine. And allow you to best choose a turbo for your application. This should have been covered in the video, as without this step, what is even the point of looking at a compressor map? It means nothing to you if you cant relate where you engine will be operating on the map.

Mishellis gauge pressure versus absolute pressure.

1 bar of compressor pressure is 2 bar absolute pressure so 2bar absolute divided by 1 bar ambient pressure equals pressure ratio of 2 or 14.7 psi of boost pressure is 29.4 psi absolute soo 29.4 psi of absolute divided by 14.7 psi ambient equals... you guessed it pressure ratio of 2

@@blago6 Wow, I don't know what I was thinking when I said that 4 years ago. Thanks

MrSlowestD16 Agree 100%. Without working out the approximate air mass your engine is expected to be consuming, these maps arent gonna help you choose a turbo. But with some info on engine size, max boost, max RPMs and such, you can pretty easily guestimate the amount of air your engine will roughly use at various RPMs and various boost levels. First step would be to try and get an approximate amount of air mass that your engine will consume. There are plenty of online calculators available that will give you an approximate value if you punch in a few bits of info. Displacement, boost, RPM and sometimes volumetric efficency. (Some online calculators are very detailed and allow for temperature and elevation aswell.) If you work out the approximate airflow you expect your engine to consume at certain RPMs and at certain boost levels, you can then plot that info onto a compressor map of a turbo you are considering and that will then help you best choose a turbo. You can see what RPMs the turbo should be at peak efficiency on your car. And what rpm and/or boost it will start to fall off the efficiency islands. But these maps are only half the story. They are only compressor maps, and they have no consideration to turbine size or AR. And how that will effect things. For example Garrett fo a gtx3076 and a gtx3576. Both have the same compressor, but the 35 has a larger turbine. These maps will not explain any of this to you. But you can use some guesstimation and assume the one with the larger turbine will be slightly slower to spool, but support a little more horsepower. This is exactly the steps i used when choosing my last turbo. And once fitted, the characteristics very closely matched my predicted calculations.

When calculating the estimated air consumption of an engine. Some things are gonna be pretty easy. Dispacement, boost and RPMs are pretty easy to punch into an online calculator. As is temps aswell. But they will sometimes ask for a volumetric efficiency (VE) figure. Which is gonna be difficult to know. But you can make a pretty good guess for this. Most 4 valve per cylinder dohc engines are gonna be up in the 90s these days. Cars with big cams may push this out a bit further and/or later into the rev range. Other breathing mods like performance exhausts and intakes, and especially things like cylinder head porting and such willl also generally net better VE. (Its why mods like that make more power) With that info, you can then plot the points over the top of a turbo compressor map and this will then give you a pretty accurate estimation of how the turbo in question will perform.

The Y axis only contains the pressure ratio. If your boost holds 1 bar above atmospheric and your turbo has a very good intake without losses, you're very close to a 2.0 pressure ratio. You will stay at 2.0 pressure ratio unless you start asking your boost controller for more or less boost across the rpm range.

The issue is that static displacement only tells you part of the story, and every turbo is going to react differently on every engine, yielding a near infinite number of combinations, each incomparable to another, even with similar turbos. You can't just list boost, because atmospheric pressure plays a role, as does the pressure at the inlet of the turbo in the case of vehicles where you're limited on plumbing. You just can't list this out with hard numbers unless it's for a very specific combination with all parts being known. 1 Bar on a 2L four versus 1 bar on a 4.6L eight is going to have VERY different airflow requirements, with no turbo able to efficiently accomplish both. Hell, even hitting 1 Bar at 3000 RPM versus being at 1 Bar at 7000 RPM on the same engine is going to have a major difference in what you're going to be asking of the turbo because of differences in airflow and cylinder filling. A SOHC 2.0L engine with a crap head and restrictive manifolds is going to move less air than a DOHC 1.8L with really high flowing heads and manifolds, RPM being equal. This is why turbo manufacturers use compressor maps rather than anything else. The charts are relatively simple, you just have to know how much air your engine moves at the RPM you want peak boost at (you can ballpark it and still be fine), and how much boost you want. At sea level on a calm day, you'd see 1 Bar of atmospheric pressure, so if you wanted 1 Bar of boost, you'd want a pressure ratio of 2. With the vertical axis being pressure ratio, that tells you how much pressure, relative to the barometer, that the turbo will be happy at and the horizontal tells you how much airflow it'll be good with. In the map shown, that turbo will be happiest with between a pressure ratio of 1.75 at 20 lb/min of air, and 2.75 and 32lb/min of air. That would have a 2L engine pretty happy at 1 bar at 4000 RPM, or it would have a 4.6L engine making the same boost at 2300 RPM nearing the top of this turbo's highest efficiency island, if I have my math right. That 4.6L engine would be so far beyond the compressors choke point at 4000 RPM that neither it or the turbo would be long for this world. Short answer: This is as simple as compressor maps can be explained and not just turn into armchair racing with potential for huge inaccuracy. TL;DR: Just get whatever the forums says works for your car and power goals.

aerocharger.com/aerochargers/#technology

check that site out! that is the most helpful tool I've seen for calculating what turbo to get! after you put your values in for your area you live and your motor specs etc. go plug the numbers into any of the turbo graphs and your in business!

They're woefully optimistic about power numbers, that's for sure.

Try this... www.turbobygarrett.com/turbobygarrett/compressor_maps

You want the air flow to be in that center island were the efficiency is best and never outside the map. However that isn't easy. It has to do with the size of the engine, rpm, boost level, and few other things like volumetric efficiency.

Ok, so I've kinda got that. Can the other side of the Turbo be mapped as well? Map how effective the Impeller is? And can you then look at both of the maps and work out the best impeller for the best compressor for the application you're looking for? I think I need to find a good book.

Yes but it might only be a flow chart. Look at garrett turbo website and their turbos have maps.

Jose Luis Ramos Keep it as is, it doesn't have much life left in it and adding a turbo would only reduce its life significantly.

You can go from any decent size such as a 73mm turbo to a 2x90+mm setup :)

Daniel Napast that's the point of my question ik most hemi's last between 200,000 to 300,000 and I want to test what might make it faster strong with a bit more torque so when I drop in the new engine ik what setup I can put in without destroying it this is the first engine and I plan on making the second engine last as long thanks.

Jose Luis Ramos Td04 will be fine mate😉😂

+Jose Luis Ramos Try this... garrett.honeywell.com/ www.turbobygarrett.com/turbobygarrett/boostadviser

2:1 or 2.5:1 he just left the compare to 1 bit as assumed...

thats retarded thanx tho

No, it is always implied when working with ratios.

Savage boy Arturo Factory Tuners don't care...Go Fast Brett does😄

Flutter sound under acceleration.

Fernando C wow. I don't even know where to begin. How do you think the experts learned? They started as full level experts? No. There are smart people out there that have and can figure things out for themselves, people like you or sheep, are preventing innovation and creativity.

NOT BY WATCHING KZfaq ROFL .there's trade certificate involved mate

Fernando C FYI, they don't teach compressor maps in engineering in Ontario. So yes, KZfaq isn't just a source of entertainment it is a source of education. Inquiring minds can now purchase books for the rest of the maths, like fuelling requirements. I wouldn't bother with a certificate, if you're intelligent enough you can figure it out on your own; I know I have and there are certainly smarter people out there.