Manifold Pressure

[@apackwestbound5946]

The "best" teachers are able to break concepts down to their simplest level.

[@NWTejas]

Thank you for a clear concise explanation of M.P. I have not been able to find a simple explanation to confirm my thoughts. This cleared things nicely.

[@lone5463]

Very well explained. Thank you!

[@phantom_legend_]

Thank you so much for making these vids, I love your content on TikTok and it honestly helps me out, if I don’t understand it in class I watch your vids and it really does help!

[@maxcfi7718]

You’re very welcome!

[@LieutenantLysol]

Just started my checkout for high performance endorsement, so just beginning to use this gauge. Video definitely helps!

[@royalwilson6640]

thanks for the run down..Im studying for my- PP -and I still need to hear it explained. Sometimes we need to hear like a 3 year old...thanks again

[@edixonocilis4482]

Nice - short and sweet. At 0:59 you said "as the cylinders descend" which I take to mean as the pistons descend in the cylinders.

[@Flow-.-]

Simple yet perfect. Thank you.

[@laiyiyiisa]

It is such a clear explaination! thanks!

[@Bobtree6853]

Thanks simple and to the point.

[@DavidHuber63]

Awesome! Thank you!

[@arafathnawaz1825]

just studying for my agk atpl exams and was struggling to get the basic understanding of this, so thank you very much!

[@maxcfi7718]

Glad to help!

[@openagarcia]

Holy fuck was this helpful. Can you make a video explaining turbo chargers and super chargers?? I love your content!

[@alk672]

Jesus finally someone explained it!

[@bobu5213]

This is the best explanation on the internet, hands down

[@Joserae]

agree.

[@mebeingU2]

I don’t know. I’ll go watch…you’re putting a lot of pressure on this explanation. /s

[@bobu5213]

@@mebeingU2 -_-

[@bluemodem1]

Since airspeed is determined by and increase on the point/port of the pitot tube. It seems that the air pressure on the air intake would experience and increase in pressure for the same reason? As speed increases the air pressure on the front of the aircraft would increase and would be sensed throughout the air intake through the carb and into the intake manifold?

[@hl6859]

Thank you.

[@hookecho9609]

I'm just starting flight sims and this answered my question perfectly. Thank you

[@maxcfi7718]

Glad it helped!

[@johnyx.official]

Believe it or not, but you just helped me, making my first landing in DCS World 😅

[@bekomcar554]

Can diesel engine MAP value with turbo charger during idle have the atmospheric pressure?

[@downwindchecklist6567]

Nice clear explanation. Thx for posting. I will explore more of your gems of knowledge. Just subscribed too!

[@maxcfi7718]

Thank you! Glad to have you

[@yamidgaray9074]

Thank you...!

[@atakancalik8306]

brilliant explenation

[@johntscanlon3929]

Hi can you tell me what readings would you expect to get as you are using a vacuum gauge in your drawing

[@canuckwing0195]

Depends on RPM. At idle with the throttle valve almost closed and the piston moving slower and less strokes maybe 11 to 15 inches. At full power, just slightly less than atmospheric pressure as the open throttle still slightly restricts airflow.

[@bluemodem1]

You said on aircraft with constant speed propellors the throttles can be moved without any change in RPMs. How does that work? Increasing the prop pitch would increase the load on the engine resulting in a decrease in the rpms. Reducing the prop pitch would decrease the engine load would allow the engine RPMs to increase. So what change are you making that doesn't effect RPMs? So maybe there is some corresponding action occurring in the prop hub as loads increase and decrease? And the way to measure the increase and decrease in the power delivered to the crank shaft by the engine since RPMS are no longer relevant might beeee....... Manifold Air Pressure???? Opening the throttle will; 1. increase airflow and increase manifold pressure. 2. power would then be increased due to the increase in air and fuel. 3. As each ft pound of torque is increased by the throttle/power increase by the additional fuel and air the prop senses the increase in torque from the engine which should result in an increase in rpms but since it is not a fixed position prop the increases and decreases in LOAD on the prop result in ADJUSTMENTS by the prop. Increase power should result in increased rpms, but the prop sensing the additional power/speed adjust to a higher pitch increasing the load and coincidentally about the same rpms. On single engine airplanes. Its a lot of money, a lot of annual/inspection/AD requirements for a system that doesn't provide a very significant increase in speed. Buy a bigger engine

[@you1680]

Hi! While studying about the piper arrow limitations, I’ve notice that in the POH it says “avoid continuous operations between 1500 and 1950RPM below 15’ Manifold Pressure” when using a certain propeller. I know that you cannot operate for prolonged time with high manifold, low rpm cause it will damage the engine, but the opposite is weird. Can you explain??

[@apackwestbound5946]

It may not be a "damage" issue at all. It might have to do with vibration. I'm am saying may and might because I don't have the specific answer. Since the limitation is for only one specific type of propeller I doubt it is an engine issue. Some Piper dealership or expert should have the "textbook" answer to that question.

[@you1680]

@@apackwestbound5946 thank you

[@whalesong999]

I get confused. It functionally looks like vacuum. So, it is actually pressure of the intake fuel/air charge due to the period of the intake being closed and the rushing intake air stops momentarily causing the pressure?

[@maxcfi7718]

it’s nothing more than the air pressure in the intake manifold. no fuel. try not to think of ‘vacuum’ as a distinct quantity. it’s not. it’s just the absence of air pressure. the lower the air pressure the greater the vacuum.

[@whalesong999]

@@maxcfi7718 Thanks, I'm getting a handle on it now. I hadn't thought of the simple atmospheric pressure as the starting point. I was thinking vacuum entirely.

[@maxcfi7718]

@@whalesong999 exactly. with the engine of the mp gauge just reads the ambient atmospheric pressure

[@whalesong999]

@@maxcfi7718 ++!

[@nimbapilot6925]

thanks for the video

[@maxcfi7718]

you’re welcome! side note - I used to live in Liberia!

[@nimbapilot6925]

@@maxcfi7718 Oh really? Nice! how do you like being a cfi? we should link up sometime!

[@g.stephens263]

Thanks, always wondered what made manifold pressure important in aircraft engines. Now, however, I'm wondering why auto engine designers don't find the measuring of it important in auto engines? I've owned a couple vehicles with chargers (one turbo and one super) with boost gauges, is that basically the same as manifold pressure?

[@maxcfi7718]

i don’t know too much about cars but i think it’s probably the same. it’s a bit more critical in airplanes since going up in the atmosphere drastically changes the air pressure and thus the power a non turbo engine can produce

[@jayminer5336]

@@maxcfi7718 Yes, your boost gauge is measuring the same thing. if you notice anything below o psi is measured in in/hg, inches of mercury, just like the one in the video. his only reads in/hg because its naturally aspirated, so its measuring the vacuum in the manifold. boost, or positive pressure, is measured in PSI, pounds per sq inch

[@dukecraig2402]

@@jayminer5336 Not always, in WW2 US aircraft boost guages measured inches of mercury, as I recall somewhere around 76" of mercury was 30 psi of boost. British aircraft boost guages measured straight psi. But German aircraft boost guages displayed ATA's or "atmospheres" of pressure, 1 atmosphere being 14.6 psi.

[@canuckwing0195]

@@jayminer5336 Lots of modern aircraft, measure boost In inches of manifold. Lycoming and Continental both do.

[@aminaiqbal4529]

Throttle vale

[@brianbusboy333]

This is completely wrong! Manifold vacuum is highest at idle with the throttle closed and lowest as the throttle is opened fully. Please explain how you feel I am wrong.

[@maxcfi7718]

Well, since a vacuum is the absence of pressure, yes, manifold VACUUM would be highest at idle but that’s not what’s being measured here. This is manifold PRESSURE, kinda the opposite of a vacuum

[@johntscanlon3929]

@@maxcfi7718 Hi I think I see where brian busboy is coming from, as a machine I have used manifold pressure to check engine condition and that pressure is normally negative reading of approx 17 to 20 in hg with the throttle closed on a snap opening of you throttle the reading would be approx 0 in hg .If the engine has a turbo fitted you could expect a positive reading which is a psi measurement ,also you have used a vacuum gauge in your drawing ,I think explaining manifold pressure using vacuum would make it easier to understand

[@maxcfi7718]

@@johntscanlon3929 oh interesting! i see. this is geared towards an aviation context where we measure positive manifold pressure

[@johntscanlon3929]

@@maxcfi7718 I see,as a matter of interest what readings would you get in a aviation context

[@theiaminu5375]

You have never seen an actual vacuum gauge attached to an engine have you ?,,,, the engine will have the highest vacuum at closed throttle and the lowest vacuum at wide open throttle ....What you are describing would only happen outside the throttle valve ...

[@maxcfi7718]

this is not a vacuum gauge as i’ve explained before. it is a manifold pressure gauge.

[@theiaminu5375]

@@maxcfi7718 The manifold pressure is a vacuum the entire time the engine is running unless you have a supercharger ...the "pressure gauge will have numbers on both sides of zero .... all pressures are relative to atmospheric pressure ,,,, we do not take them to space to calibrate them .....

[@maxcfi7718]

@@theiaminu5375 yes, but this is measuring the actual pressure in the manifold. hence why it’s lower when the throttle is closed and equal to atmospheric pressure when throttle is wide open (for a naturally aspirated engine.) my understanding is a vacuum gauge would measure the difference between atmospheric pressure and the manifold pressure, so it reads higher with the throttle closed. we do not normally measure vacuum on the engine in aviation

[@theiaminu5375]

@@maxcfi7718 It's backward from what you would encounter in the REAL world ... low is to the left (counterclockwise)and high is to the right (clockwise) in every gauge you will find ....Even on a mass spectrometer ...

[@maxcfi7718]

@@theiaminu5375 yes? and it is also on the manifold pressure gauge. not understanding what you’re getting at 😂

[@BillyG869]

Very poor explanation….missing most technical points

[@maxcfi7718]

and which technical points would those be, Bill?

[@andremetayer1467]

@@maxcfi7718 No reply… Bill has at sea falen…

[@spebsqsa11]

At 1:00 you said “as the cylendars decend….. “. It’s the PISTON that decends.

[@maxcfi7718]

@@spebsqsa11 yes you are correct