BOOST pressure vs. MANIFOLD ABSOLUTE pressure vs. ATMOSPHERIC pressure - BOOST SCHOOL #4

AEM SS MAP sensors: bit.ly/d4a-map-sensors
AEM SS Pressure (Gauge) sensors: bit.ly/d4a-pressure-sensors
AEM boost controllers: bit.ly/D4AtruboostX
AEM ECU: bit.ly/D4Ainfinity5
AEM wideband AFR gauge: bit.ly/D4Axserieswb
Let's start with the basics. Air pressure or more specifically atmospheric air pressure. As we know, earth's atmosphere is filled with air. We are born and we die in this atmosphere, it's our natural environment, and this is why we don't really notice or feel the weight or the mass of air. But air most definitely has a weight and a mass.
All that air, the entire atmosphere, weighs about 5 million billion tons! So how come we don't get crushed by it? We don’t get crushed because all that weight is distributed evenly over the entire surface of the Earth. The average pressure you feel on your body is about 14.7 psi or 1 bar. But because you can't escape this pressure, and unless you've been to outer space, you never actually spent even a moment of your time without this pressure, you don't really feel it as you can't reference how it would feel without this pressure.
So what do you think, what's the place where you can feel the least amount of atmospheric pressure without leaving the earth? That's the top of Mount Everest of course, the highest point on earth. The highest point has the lowest pressure because it has the least amount of atmosphere above it, the least amount of air weight above it. The highest atmospheric pressure you can experience on earth if at sea level and the lowest is at the peak of mount Everest. But you can also experience very low atmospheric pressure if you contract a virus like Covid 19 and they put you into an isolation room. Many isolation rooms are actually negative pressure rooms. Inside a negative pressure room, the air pressure is artificially maintained at a pressure lower than outside the room, a pressure lower than atmospheric pressure. This is usually done with exhaust system that suck out the air of the room.
Because the pressure inside the negative air pressure room is lower than outside it, the contaminated air doesn't come out of the room when you open the door. Instead, clean air from the outside comes into it because air, like all fluids, always flows from a higher pressure area towards a lower pressure area.
Do you know what else works on the same principle as an isolation room inside a hospital? The cylinder inside your engine!
When the piston moves down inside your cylinder it creates a vacuum, or an absence of pressure. The cylinder moves down the bore at extremely high speeds and as it moves down it rapidly creates this void, or empty space, that for an extremely brief moment, has no air it, and as such is at a lower pressure than atmospheric pressure. But a turbo or a supercharger is capable of generating significant additional air pressure, and the air pressure inside the intake manifold of a forced induction engine can be double or triple that of atmospheric air pressure.
When you're looking at a boost gauge mounted inside a vehicle you're looking ONLY at the boost pressure generated by the turbo or supercharger. This means that a boost gauge isn't showing the actual pressure inside the intake manifold. It's showing the pressure inside the intake manifold - minus the atmospheric pressure. When you expose a boost gauge to atmospheric pressure it's going to show a value of zero. This is because a boost gauge and it's sensor are referenced to atmospheric pressure. The reason behind this is that you're only interested in what additional pressure your turbo or supercharger is generating, the pressure it ADDS on top of the atmospheric pressure, because that's what boost is, you're boosting your engine's power by adding more pressure than could be generated by natural aspiration i.e. the pressure of the atmosphere.
But things are different from the perspective of your engine's ECU. The ECU is interested in ALL of the pressure, both from the atmosphere and the pressure added by forced induction. It's needs to know all the pressure because it's trying to match all of the air mass with the correct amount of fuel. So the MAP sensor that reads pressure inside the intake manifold and feeds data to the ECU is referenced to absolute zero pressure. If you were to expose this sensor to the atmosphere it would read around 14.7 psi at sea level.
So boost pressure equals manifold absolute pressure - atmospheric pressure.
and manifold absolute pressure is: boost pressure + atmospheric pressure.
00:00 Atmospheric pressure
05:00 NA, Forced induction and Elevation
07:56 Boost pressure vs MAP
10:34 Stainless steel vs brass
12:22 MAP vs MAF in tuned boosted engines
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#d4a #boostschool #underpressure

[@d4a]

AEM SS MAP sensors: bit.ly/d4a-map-sensors AEM SS Pressure (Gauge) sensors: bit.ly/d4a-pressure-sensors AEM boost controllers: bit.ly/D4AtruboostX AEM ECU: bit.ly/D4Ainfinity5 AEM wideband AFR gauge: bit.ly/D4Axserieswb

[@jaysmooth8888]

Cool

[@m721ac]

Hello.do you have a video that is more diesel specific?would really appreciate it.woukd be nicr content for you too i would imagine.you are ver well versed and give crystal clear explanations yhat even a doorknob would understand.thank you for this and more power to your channel

[@hieronymus..bosch8532]

Reirregardless , brilliant video 😉

[@RobOnMotors]

@driving4answers do you have a video that covers the principle behind turbo flow Vs turbo pressure. I understand that bigger turbos flow more therefore make more power, however, they are able to flow more and decrease manifold pressure. How is it possible have less pressure but more flow. If the restrictions stay the same, i.e. the head and inlet. Then why doesn't that extra flow turn into extra pressure?

[@eTiMaGo]

school's back in session, kids!

[@caig9868]

Still blows my mind that this amount and quality of information is being offered for free. Big respect!

[@danielamorim2909]

I can't explain how well this series is put together. I am learning so much for my Gen 2 3SGTE swap into my ST162 Celica. Keep up the videos!

[@WanderingExistence]

2:48 Death Valley has 14.9 psi of pressure due to being a 280 ft below sea level

[@edbo10]

death valley boost balley confirmed

[@gor4988]

Not to mention some of the mine shafts we've dug out

[@fastinradfordable]

When my car had no turbo it ran really REALLY well in Death Valley. Now it has a variable turbo it runs REALLY well, all the time :)

[@bene5431]

​@@fastinradfordable Death Valley is also very hot, so while it might have high pressure the air isn't very dense (unless you drive at night)

[@TheCarbastard]

Only someone who definitely knows what they're talking about can present things in such an easy to understand way. Thanks a bunch!

[@SUNUVAGUN]

There are places below sea level on land. The dead sea depression is negative 413 meters sea level.

[@GaurdianAzzar]

Glad I'm not the only person to think of this.

[@maxcactus7]

Happy D4A Sunday, engine heads!!

[@firstielasty1162]

Light planes have an interesting variety of turbocharger wastegate controls systems. Some are as crude as a fixed wastegate that relies on the pilot watching the MAP gauge and controlling with throttle (yes, you can overboost them simply by firewalling it on takeoff), others are more sophisticated and actually regulate the manifold absolute pressure. They will maintain the set pressure throughout a climb until the wastegate is fully closed, at the "critical altitude" of the system, above which power drops with the altitude increase. Wastegates are usually hydraulically actuated by engine oil. The control systems modulate the oil pressure to the wastegate. I added a MAP gauge to my turbodiesel RV...the gauge is from a multi engine aircraft (actually a dc-3). One port I left open, so it indicates ambient pressure, the other indicates MAP. I have driven it over the Rockies several times, interesting to watch both ambient and max MAP drop. Thus, available power drops proportionately..car people think their turbo negates the effects of altitude. Wrong, unless your turbo control system is designed to do so! It is probably not.

[@shautohaus]

I honestly don't know how someone can explain something so complex, so clearly that I have zero questions at the end. Amazing.

[@MI-sw3iv]

Think I'm in love with this dude? Hope you know how articulate and concise your content is, it's veryy impressive! No teacher Ive ever seen can teach like you do with these videos !

[@ibrahimqureshi2420]

your are literally the best instructor ever i appreciate you to spend your hard work and time just to explain something to us I have by far learned so much from your videos thanks!

[@SJR_Media_Group]

There is one more thing that is important; Mean Effective CR (compression ratio) Versus Boost. This takes into consideration pumping losses, heat, and altitude. Engine might have a fairly high static CR and too much boost = obliterated engine. The actual dynamic CR will be less. I was reading a article on aftermarket boost used on a high performance NA engine. According to my 'math' the boosted CR was 17:1. But the actual CR was 11:1. I was pleasantly surprised because engine I was designing had very low static CR so I could add 5 bars of boost and not blow it up. Plus the actual CR can run on Pump Gas.

[@MrSquezzy]

i did run over 30 psi because of my faulty wastegate. tune was on 25 psi. hopefully it didnt blow up

[@SJR_Media_Group]

@@MrSquezzy Thanks for comment. Sometimes shared knowledge is better than dry data from the engineers.

[@FinlayDaG33k]

WW2 fighter planes used turbochargers and superchargers so they could fly at higher and higher altitudes (which allows them to store more potential kinetic energy so they can start with a nice speed advantage when swooping down)

[@agentsj1]

I'm a simple man. I see a D4A video, i click Like.

[@csanton3946]

im learning a lot and this is free, you should receive value adding citizen of the earth award

[@johnlovett8341]

Love the channel and this boost series. There's an occasional statement that's off from an engineering or physics perspective ... but that's not what this channel is about. It's about understanding what's going on rather then always speaking precisely. Put on your motor head hat and this channel is 100% binge-worthy, learning experience. Go D4A!

[@barrymckockiner4887]

What did he get wrong? Just curious

[@Folderq]

Genious simply material, it will help the generations. Thanks !

[@jasonanderson2876]

New boost school!! Yes love this series👌🏼👍🏼

[@mikegreen2229]

When you do a skydive, that’s when you discover the mass and friction of our atmosphere you take for granted standing on the ground. It’s like falling through a very lightweight ocean.

[@TheMapleDaily]

I feel every day I watch at least one of your videos and learn so much in such a short amount of time, you really are efficient at teaching and staying on point!!!!! Much Love!

[@yamafanboy]

This video was so well delivered I vote that we incorporate the word "irregardless" into the english language as a tribute to the best boost school professor on earth?

[@angelopea8334]

That's a great video! Thank you for sharing all this knowledge about engine tuning and physics principles. Just for record: 1 bar is around 14.5 psi, not that far from 14.7 but wanted to make it clear. Cheers!

[@sking2173]

I never understood why manufacturers installed boost gauges in turbo cars instead of a manifold absolute pressure gauge, as used in piston aircraft. Simple, accurate, and easy to interpret ...

[@kapitainekram]

Another way to pass a MAF limitations is to devide your intake in 2, putting the MAF on only one side. It will then remain precise as it will measure only half of the air entering. Then you'll have to adjust the ECU program to take this into account (basically multiply by 2 the values related to MAF). If you want to be more precise by measuring exactly what's coming in the 2 sides, you can also use 2 MAFs, one for each side. Each will be measuring half of the air. You'll have to use a device between the MAFs and the ECU to add the 2 MAFs values and then send the result to the ECU.

[@fastinradfordable]

Great until one cylinder has a problem and it is either not noticed or over compensated.

[@breathlessboarding2791]

One of the best teachers out there, keep up the good work!!

[@divin3kag3242]

Dont ever stop what your doing i enjoy informational vids like this

[@RX7GSLSEowner]

Thanks, I've been waiting for the next installment in this series! Thumbs up!

[@MI-sw3iv]

You're the best, no other channel or content on technical mechanics and cars compares !

[@christianmeeks4430]

I know all of this already but I still greatly enjoy watching these videos and still learn little tidbits here and there. Great series.

[@corbinyoung5320]

I love how detailed the description is great info great video thank you

[@ricobelcourt3797]

Thank you so much, all the other videos made no sense and only gave me little pieces of advice and left me confused. Full understanding now thanks to you

[@martinluther1913]

First of all I am thanking you 🙏 with my bottom of heart such an experience explaining all the stuff which is all related to automobiles and I am learning a lot of knowledge from your videos. Thank you so much my brother.

[@dagridiron94]

Happy Sunday I love this channel!!!

[@danchoiordanov6740]

thanks for all series bro. apriciate it !

[@blkdna748]

Things are getting so interesting and little bit complex. D4A keep going.

[@SimbaHQ]

best car profesor on KZbin, thank you sir!❤

[@Janni069]

I think this couldnt be explained any better than in this video. Thank u very much for the uploading of the vid

[@aaa72317]

Damn, those AEM plugs are smooth AF :D Amazing videos, man. Quality is up the roof.

[@fastinradfordable]

That’s what she said

[@scotthodges5214]

Learning a lot from this series. Thank you~

[@876Shottas]

Learning alot on this channel, thank you

[@mpower3144]

this is the best ever explanation i have seen, i was struggling with the sensors functions ,

[@jakubtrzpis2595]

I'm waiting for the assembly of a 4A engine

[@mr.mr.2318]

Thank you D4A, you make very very good videos

[@komoru]

Thank you for the great explanation and most of all, for not using cheesy background music!

[@80Loke]

This is just explained in perfection, very very good:)

[@fernandoanatomia]

I like your videos because they are educational and at the same time enjoyable to watch.

[@MrCheeto01]

Could one not experience higher atmospheric pressure by visiting Death Valley that is -282.2 feet below sea level?

[@d4a]

You're right! And it's still on the surface of the Earth

[@MrMatty1974]

this is just so, so good.

[@zues2013]

Always learning so much from Your channel despite being a tech keep the vids coming!!

[@NightWrencher]

Your growth has been insane, keep it up

[@fastinradfordable]

That’s what she said

[@fastinradfordable]

I mean come on it’s too good

[@NightWrencher]

@@fastinradfordable thats what she said

[@terjejohnsen3651]

Good video as allways thanks alot.

[@MikeyMotorsport]

Very good video man. Thank you!

[@Pep4dalovofcars]

Really love this channel bro awesome work😎💯👍🏻

[@arnoldodida]

always a pleasure

[@JoeBob79569]

This is fantastic. I've got an issue with my car, likely the MAP sensor, and I've been searching for hours online for one, only to finally realise that all the shops online call it a boost pressure sensor, but my workshop manual calls it a MAP sensor.. Which is obviously how I ended up on this page!

[@fastinradfordable]

Manifold air pressure Is boost pressure

[@JoeBob79569]

@@fastinradfordable Yea I know that now, but everybody calling it different names is kind of annoying when you don't know, and you're searching online for a MAP sensor but can't find the right one! But it turns out my MAP/boost sensor was fine after all, it was my EGR valve that wasn't closing properly, and it was throwing off the pressure readings..

[@zakaryreilly]

This is exactly the kind of video I was looking for

[@kjnkjnkjhkjhjk8465]

Irregardless is with regard or with respect, high estimation of value. Regardless is without regard, respect, or low estimation of value. Ir equals not, so ir-regardless becomes not regardless, thus with regard. A person I worked for did me a solid by correcting me on this matter. Thanks Shelly. Great video series, I've learned a lot.

[@AAAA-vm2nk]

i am so unpatiently waiting for the full 100+ video playlist to be complete

[@d4a]

It will take a while 😊 but I'll do my best to make sure it's worth it.

[@dawricktyndale7550]

always enjoy the content.. real useful information keep it up nuff respect from jamaica

[@MrWilliam.Stewart]

Ever tired giving a wave to a passing motorist who's let you overtake him on your superbike and you'll feel the weight of air. As it happens, aground 1.2 Kilograms per cubic meter. Ahh, altitude, necessity is the mother of all invention, thank you to the Aircraft industry for the exhaust turbine charger.

[@denisfontaine2938]

nice Renault R5 Turbo vive la France time 9:50 even if I know everything you explain you show me a different way and my knowledge is kinda sharper. Thanks great videos!!

[@oshanechin5395]

Thank u

[@scriptmike]

I'm from Detroit, the Silver Dome in Pontiac when is was there had a pressure higher than 14.7 PSI to hold the dome up.

[@warrendegonzague]

I love your videos, man.

[@ChadilacE30]

Actually educational and interesting to watch. Liked and subbed!!!

[@twinforce_fusion6560]

Made me smarter, now makes sense that the boost Pr curve is very similar with the MAP curve. Now makes it easier when I read my data logs.

[@evilpanamajack]

Great vid thanks

[@TheChrismsanchez1]

Excellent!

[@Excepticus]

i really love these videos. problem is if i ever get a car i wouldnt know how to ever start modifying because i have no experience with doing mechanical things.

[@andersdaun3950]

Thank u. Greetings from Sweden.

[@saligator8879]

Great video!

[@MattFahnix]

Whoa! The hair is gone! Loving the series. Thanks so much!

[@802Garage]

Boss as always.

[@marcstlaurent3719]

Don’t forget about Death Valley , it’s 282 ft below sea level

[@noahwhite7848]

A video explaining sensor resolution and how it affects tuning would be much appreciated 🙏🙏

[@mamen99]

Thanks

[@menooaderohanian4129]

Like before . I cant find words to explaine how much your videos is awsome

[@slightlyinsaneraf]

School was never so fun kids

[@danielferraro59]

you are the best !!!

[@bobross6677]

Ill refer to this cause i dont have any work to keep this fresh in my head

[@remiltonsilveira7314]

Comment for the algorithm

[@stevebj6433]

Excellent

[@Lilmiddwest]

Now make more sense great video

[@TurboHappyCar]

Great stuff man! Dropping a comment just to help out the algorithm.

[@bowez9]

MAP has major draw back of not taking into account of wear. Either compression loss with less vacuum produced which is interpreted as higher eninge load irregardless of actual load; or blocked air filter which result in the exact opposite. Where as MAF measures the MASS of no matter state of eninge. As for modifications its as simple of upgrading the MAF and calibrating the ECU. MAF and MAP can do the same job but the MAF isn't relying on a reference table for interpolation--which is affected by wear items--as MAP is.

[@marc21256]

Isolation rooms are negative pressure because they aren't airtight. There are microscopic cracks. A negative pressure room will suck "clean" outside air in the cracks, and exhaust only decontaminated air via filtration. If the room were positive-pressure, with air being filtered and pumped in, as is most common with commercial HVAC, you'll push "dirty" air out the microscopic cracks. That's why in the movies, you'll see people in labs in puffy suits. The suit is positive pressure, to protect the person in the suit, and the room is negative pressure to protect the people outside the room. Pressure should always be higher where you are protecting and lower for the "dirty" area, to ensure proper protection. Taking this back to cars, a clean room for painting a car will be kept at positive pressure, so that dust and contaminates can't come in. The air is pressurised through the filter system to prevent impurities. The room needs to be cleaner than outside, so it's kept at a higher pressure.

[@mcdonald2037]

Your a great teacher ... I'm subscribing

[@tdogg2535]

I get so excited to watch your videos! Roll myself a joint, make a coffee, sit back and relax! so educational your content, PLEASE DONT EVER STOP!

[@fastinradfordable]

Damn straight T dogg

[@Bullshit_Media]

2:26 I'd just like to add that the illustration is probably not to scale to him.

[@mrinalkarmakar4066]

Make in depth videos on car sensors and their functions

[@scunnerdarkly4929]

Always great content, brilliant lo-fi presentation without unnecessary gloss, and above all, the enthusiastic delivery. How about a name to go with the face? Turbo Jesus came to mind before the haircut happened...

[@fastinradfordable]

D4a Is a good name no?

[@stevenduke260]

Excellent 👍

[@96blackjacket]

Technically Death Valley in Nevada is well below sea level it’s also a cool place because not only is it the hottest place on earth it has rocks that move on their own and there are places were the earths plates are folded on each other which effects gravity and you can stand diagonally without falling or watch rocks curve as they fall

[@kusee.]

Best teacher

[@LeZturbo]

Great !

[@pgtmr2713]

You may not feel the pressure at altitude but you can feel the effects of hypoxia. I wonder if orientation of a sensor relative to the engine position helps, perpendicular to the engine tq and not over the top of the head.

[@user-pc1er8zy7c]

Good Video as always. Can you do one video on wheels, like whether cheap cast aluminium one's are even lighter than their steel equivalent given their lower material strengh. And also what would be the ideal shape for them.

[@gwenmotor]

Awesome 👍👍👍

[@shadowopsairman1583]

Anything over 29.92" Hg or 14.7PSI at 59°F/15°C standard day sea level is considered boosted over MAP. Boosting is needed to either sustain 29.92"Hg in Aviation or to provide more horsepower.