Everything you know about turbo PSI is likely wrong.
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- Опубликовано: 28 июл 2024
- Momentum Worx is the PREMIER supplier of Heavy Duty Diesel Truck Turbos & Manifolds.
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Boost pressure is only 1 parameter of many! While it is great to have a some parameter to zero in on, boost pressure only paints part of the picture of how a turbo is performing and interacting with the engine.
This video gives an overview of other metrics involved with turbos and how these metrics affect overall performance.
30 PSI is not 30 PSI - watch the video to find out more :)
Compressor Maps: Pressure Ratio, Mass Flow Rate, Surge, Choke, Efficiency Island
Pressure ratio - Absolute outlet pressure divided by the Absolute inlet pressure. The gauge in your vehicle measures the pressure above atmospheric pressure (So if you are making 12PSI, its actually 12PSI + atmospheric pressure). Absolute pressure at sea level is 14.7, this will decrease as elevation increases.
Mass Flow Rate - The physical mass of air flowing over a given time period. Often expressed as lb/min (pounds per minute), or CFM (cubic feet per minute)
How to determine desired flow rate: To generalize, gasoline engines will generate 9.5-10.5 horsepower at the flywheel for each lb/min of airflow. If your target peak horsepower is 400 Hp will require 40 lb/min. This is NOT perfect science, just a rough guestimation.
Surge Line - The left hand boundary of the compressor map. This area is plagued by flow instability, the turbo will flutter or bark. This is because the pressure is far beyond the flow capability at that time and the air is forced back through the turbo charger instead of into the engine. This can happen when:
-The throttle plate is quickly closed when you let of the accelerated and there is pressure in the air piping but no where for it to escape to. This is where BOVs and MAP groves comes into play.
-The motor physically cannot consume anymore air at this operation level
Choke Line - The right hand limit of the compressor map. The turbo is no longer efficient in this area. Shaft speed will be beyond its mechanical limits and the amount of heat generated will decrease overall performance.
Efficiency Islands - Specific segments on the maps that represent points which the compressor is most efficient. The smallest island near the center of the map is the highest or peak efficiency island. Each larger ring is less efficient then the one that proceeds it. . 
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As someone who already knew all of this, you did a great job explaining.
The size of the exhaust side is so under talked about. It van make or break your experience
I’ve watched a few videos of different guys trying to explain this. What I discovered, that I don’t think a lot of people hear from the videos, is that being in your efficiency island, is also dependant on the RPM of the engine. A prime example of this, is my truck, with the old turbo, and all the flow mods I did (intercooler, intercooler piping, exhaust, and steed speed manifold) I would get compressor surge in the middle of the RPM range, at about 10-13 psi, while excellerating. The turbo did not do this before I did all the intercooler piping and intercooler. I increased the flow enough, that the turbo couldn’t keep up, and it would surge in that particular rpm range, with that amount of PSI. As soon as I got out of that spot, it would return to its efficiency island and build to 23psi boost, because the engine had enough rpm to deal with the flow the turbo could provide. There’s a relationship between the strength of a turbo and what the engine can take. Sometimes the engine can take more but the turbo compressor can’t handle it. I replaced the turbo with one that had the same size turbine wheel but smaller housing, and a 2mm bigger compressor wheel, and a better flowing compressor, and the surge went away entirely. I find this stuff so fascinating! Thanks for the Video
Exactly!
Subscribed cuz of the weeds joke lol
Great video
I had that turbo bark in my 2015 Isx . Disconnected the throttle plate and problem went away. Thank you great info
DUH!
Pressure and flow are not the same!
It’s like most people don’t understand air tire pressure vs tire air volume.
That “turbo” is a effing fire truck hose flow 🤣
And then there is the issue of not every setup as far as this was done or that was done to the fuel pump, the head('s) the rest of the exhaust, no 2 setups are indentical. You can get a ball park range. You choose and use what someone says gave them a specific result and put that together on your setup and what the heck, I'm not getting the numbers you said I would get, or on the other hand, your setup surpassed those numbers and you feel great. Desktop dyno and spread sheet engine building ! LOL.
What if you have a recirculating valve my Volvo doesn’t have a bov it’s got the recirculating one
What turbo would you recommend cat c15 bxs accert 18:1 compression ratio converted into single turbo 550hp tune 6nz engine wiring harness & file tune as well.
How can I get in touch with you?
I have a question, I have a 2014 f150 3.5 ecoboost, one of the turbos seems t9 be releasing the boost pressure before i let off of the gas, what could be causing this issue? Someone, anyone? Pl3ase helps
I have a 3408 pc cat engine in a 81 peterbilt. What turbo do you have that is best for this engine. Thanks
Right it’s all about flow baby
Density.
@@BrodeyDoverosx nah flow. If you had the tiniest ko3 turbo I don’t care how dense the air is it’s still too small
@@BrodeyDoverosx with proper flow/sized turbo you will receive excellent “ density” unless the turbo is a tiny ko3 then your shiiit out of luck 🍀
Boost has nothing to do with calories. You just needed to say that boost is actually a measure of restriction.
Your turbo flowing into a garage will be 0psi, your turbo flowing into a 2L bottle of sofa will be much higher in restriction.
How much PSI is necessary to make 80 lb•ft more torque on a 4.0 Liter V8 that produces 320 lb•ft of torque.
320 lb•ft NA engine + 80 lb•ft boost = 400 lb•ft.
Would 3.63 PSI be enough?
80.0204082 lb•ft = (320 lb•ft X 3.63/14.7 + 1)
It depends on the VE and what the air density is.
I need to talk to you I believe you will put me on the right direction.
Not an expert? Would you look at that beard that just screams I'm an expert in my field😂👍