MAP Sensors

[pornstar]

Anyone wanna have a go at what it represents?

[Psyklops]

manifold absolute pressure...google is useful ;)

so what do I win? new set of coilovers perhaps? :D :D :D

[fueltank]

lol.

[Trust-Me]

Stock MAP sensor will see just over 1bar, infact about 1700mBar.
Its a measure of pressure in the intake manifold, helps the ECU decide what fuel/ignition setting is required based on MAP vs RPM

[wynode]

Why the question?

It's a measure of pressure within the intake manifold used among other things to determine engine load.

[SIKCVC]

rather vital to your car running...

[pornstar]

im glad sum1 brought up the measurements :) i was going to elude to it.

mbar was the measurement u used. anyone know the conversion from mbar to hg?

[SIKCVC]

hg what? mm of HG or inches of HG???

mbar as in millibar or micro bar.

I've got some converting program... converts everything. speeds temps area wet-volume dry volume... you name it, it converts it... but i forgot where i got it from :P

[poid]

mbar = millibar

if it was microbar the prefix would be the letter "mu"

[tinkerbell]

Anyone wanna have a go at what it represents?

it simply 'represents' vacuum.

[pornstar]

ahhhhh thats better!
Tinker, vacuum u said? Can u elaborate what the importance of that is for a high revving NA engine?

[tinkerbell]

Can u elaborate what the importance of that is for a high revving NA engine?

as the pistons move down on the filling stroke the create a vacuum that draws air into the cylinder ready for the compression stroke.

the more drawing power this has the more A/F mixture that fills the cylinder and therefore the greater the combustion energy.

so vacuum is important as it determines power.

the MAP sensor compares the air pressure compared to the absolute pressure (i.e. outside air at 1 bar) and determines how much air is getting drawn into the engine and thus calculating the pulse width of the injectors to regulate the A/F ratio...

so to answer your question, it might be better to relate to a non-NA car that has a bloody big pump forcing air into the cylinders - so you see why vacuum is important for NA cars - as it is the only thing that fills the cylinders with A/F mixture...

[ECU-MAN]

some Hondas have BARO or PA sensors to measure the outside air pressure that tinkerbell mentioned above for high altitudes

[ProECU]

The MAP pressure sensor has the same operation throughout the rev range in that its a sensor which measures pressure and "Vacuum" to some extent SO in terms of High revving NA, it is as important as low revving NA.

The job of the map sensor is to tell teh ECU how much fuel/ignition is required at a particular MAP vs RPM setting. How do i know this, well ive decompiled the bin file (ala hondata) and read the code.

The MAP sensor does NOT compare the outside pressure AT ALL. It has certain boundaries, a min/max value as a check for sensor validity. If the voltage exceeds these tolerances, a code (CEL) is returned.

tinkerbell is incorrect by stating that vacuum determines power, this is NOT the case. The ECU will only see vacuum from the MAP sensor under idling, or when you back off the gas pedal.
Power is determined by the quality of the burn in the combustion chamber (a/f) and the ignition (adv/ret) combined with many other factors such as engine load, fuel quality etc.

Cylinder filling on the other hand, is a product of piston velocity and also a process commonly known as scavenging. This is the process by which cam overlap causes a low pressure condition in the cylinder head, hence mixture is drawn from high pressure to low pressure, increasing the amount of fuel at any given combustion process.

Manifold pressure is not directly related to the combustion process. Take for example a forced induced application.
You have probably heard people talking about B16's as being a torquless motor, this is due to the low piston speeds (long rods) at low rpm.

On the other hand, the D-series motors have more torque and are "nicer" to drive at low rpm's (smaller rod -> faster piston speeds)

This is somewhat of a side-track, but hopefully an insightful one.

ProEcu

[pornstar]

thats an excellent explanation proECU. The map sensor is a common tricky sensor many get confused by. From what i have laernt, it is even less complicated than that, it merely is a temperature sensor in very very basic terms!

[tinkerbell]

so why is it called a Manifold Absolute Pressure sensor?

[pornstar]

because if u think about what the amount of pressure in the manifold is, the air is a particular volume but that volume is not the only factor, desnity si the factor to consider.

density is a function of heat :) thats what i said about the sensor in VERY VERY VERY BASIC terms is :)

[tinkerbell]

edited post.

[ProECU]

its an absolute sensor because it is relative to atmosphetic pressure

ie, stock MAP sensor reads 1000mbar = 1Bar is still not boost.
anything over this is boost. That because the first 1000mbar is atmosphetic.

[wynode]

Great info ProECU

[pornstar]

Good technical discussion, what I was actually trying to lead people to with this discussion about map sensors is what the difference was in how people treat things. for example, most people would refer to the state of NA as negative manifold pressure or a vacuum. For most tuners, its anything below 100kpa, 14.7psi absolute, less than 1000mbar, but I was trying to get the point across that they are all the same thing, and when most people describe something as vacuum, I prefer to call it a little pressure ;)

[tinkerbell]

some Hondas have BARO or PA sensors to measure the outside air pressure that tinkerbell mentioned above for high altitudes

yeah, they do, but not in Australia (it is too flat here).

however, that is not what my erroneous “compares” statement was alluding to...

my mistake was trying to convey the ‘absolute’ nature of the “thing” that the MAP sensor represents, it being an ‘absolute’ measurement and not real representation of vacuum i.e. it takes the vacuum represents it as a pressure

but it was early, i had just arrived at work and it seemed like pornstar needed some technical input to fuel his attempt to lead us to the controversial conclusion that MAP sensors are really just very very basic temperature sensors, for whatever bizarre reason he wanted to do that…

[ECU-MAN]

yeah, they do, but not in Australia (it is too flat here).

however, that is not what my erroneous “compares” statement was alluding to...

my mistake was trying to convey the ‘absolute’ nature of the “thing” that the MAP sensor represents, it being an ‘absolute’ measurement and not real representation of vacuum i.e. it takes the vacuum represents it as a pressure

but it was early, i had just arrived at work and it seemed like pornstar needed some technical input to fuel his attempt to lead us to the controversial conclusion that MAP sensors are really just very very basic temperature sensors, for whatever bizarre reason he wanted to do that…

AUDM 1989 A20A4 Accord had a baro under the glove box, all POA ECU for 94-98 have in the ECU, A20A4 prelude just like the accord under the glove box. OBDII P30 have the BARO in the ECU. 94 ledgend ECU has it as well. these are jsut the ones Iv seen Im sure there are more in other models :)

[ProECU]

I know for a fact that the BARO sensor is used in the code as a backup to the MAP sensor when there is a problem with the MAP sensor.

I dont actually know what the BARO does, exactly, however it must function similar to the MAP based purely from what ive seen in the code.

[tinkerbell]

well, it is funny you should say that you dont know what it does - considering you have seen the raw code from the ECU's

if in fact ECU-MAN is correct (i dont see why he wouldnt be, i simply had heard Honda decided not to use BARO sensors in Aust. due to lack of any mountains) and Aussie Hondas do have the BARO sensor then the ECU's do actually *compare* the outside air to the MAP signal and use this as an altitude correction function in determining injector PW's...

so for your info - the BARO does not function as a back up to the MAP sensor - how could it? it is not even connected to the intake manifold...

and it is exactly the same as the MAP sensor in its reference voltages as it is the same type of sensor.

[fueltank]

its an absolute sensor because it is relative to atmosphetic pressure

ie, stock MAP sensor reads 1000mbar = 1Bar is still not boost.
anything over this is boost. That because the first 1000mbar is atmosphetic.

so is it possible for a N/A car to produce over 1bar? (boost).

[tinkerbell]

so is it possible for a N/A car to produce over 1bar? (boost).

yes, through a carefully designed intake and only when the car is moving (probably rapidly)...

it is much easier to do this for motorbikes, these commonly have Ram-air induction...

[pornstar]

hmmm i never thought about it like that dave.

to be honest i dont see how it could create a pressure greater than 100kpa because there is no other force besides the atmo pressure creating the induction into the engine.

but im not saying its not impossible. wanna explain how it becomes greater than atmo pressure without another force exerting compaction or compression?

[ProECU]

Tinkerbell
I find it interesting how you can comment with such confidence as to the operation of the BARO sensor when you have no clue what a MAP sensor is.

NO offence intended here, but, Get a clue my friend, you contradict yourself above when you mention the BARO & MAP share the same reference voltages. Why would they share same voltages but have different operation.

Stop posting false information to the masses if you clearly do not know for certain.

For those who are interetsted, here is a segment of the code detailing the MAP & BARO definitions
F5 A4 : LB A, A4 ; Load Baro (as Backup MAP)
EA 12 05 : JBS off 12.2, 0A15 ; jmp if MAP error
EC 12 02 : JBS off 12.4, 0A15 ; jmp if MAP error
F5 A7 : LB A, A7
8A : STB A, R2
60 00 70 : MOV X1, #7000 ; MAP constants

FACT: some Australian delivered cars DO have BARO sensors. Ive seen them in OBD2
FACT: BARO is a backup for the MAP sensor
FACT: NA cars can see boost ONLY when volumetric efficiency is greater than 100%

This is my evidence to support my claim, where is yours?

Regards
ProECU

[tinkerbell]

taken from tech2tech.net:

All Rights Reserved 2000 Sure Seal Products Inc
This manual printed 4/9/00 from the file pgmfiobd_002.
14 MAP / BARO Sensors
14.1 General Overview
The manifold absolute pressure (MAP) sensor and the barometric pressure (BARO) sensor are virtually identical sensors. One reports intake manifold pressure information to the engine control module (ECM) and one reports atmospheric pressure information to the ECM. They both use the same pressure-sensing component and therefore will indicate the same voltage when both are measuring the same pressure, such as key on/engine off (KOEO).
Both these sensors report the values in absolute pressure to a scan tool. Absolute pressure is just another way to measure vacuum. Absolute pressure uses a total vacuum as its base and therefore our normal environment is considered a pressure.
The pressure unit is in inches of mercury (HG) just like vacuum. The result is that the absolute pressure readings are similar to vacuum readings except the values are opposite. A high absolute pressure reading means a lower vacuum.

Now that you are totally confused, let me make a suggestion. Forget vacuum readings and absolute pressure readings and just use the input voltages to monitor the engine vacuum. You can see from the table that the MAP input voltage at idle,
no load, should be .95 volts. Remember that number, it is one of the critical numbers that you will need to memorize. If the MAP voltage is just under 1 volt at
idle, with no load, the engine vacuum is right. So, why not just use a vacuum gauge? A digital volt-ohm meter (DVOM) hooked onto the MAP or BARO sensor input wire is the most accurate way to measure the engine vacuum. Most vacuum gauges are not very accurate and the input voltage is the signal that the ECM monitors. Regardless of what your vacuum gauge reads you will need to check the
sensor by checking the input voltage anyway.
When a Honda is running extremely rich or lean, always check the MAP sensor input voltage first. Chapter 7 is dedicated to the MAP sensor / injector PW relationship.

14.2 How Do They Work?
The MAP/BARO sensors are standard 5-volt reference sensors. The ECM applies approximately 5.0 volts and a ground to the sensor on two wires and a third wire returns to the ECM an input voltage, as shown in Illustration 14-1.
The normal MAP input voltage is approx. .9 volt at idle, with no load. At wide-open throttle under a load or KOEO the voltage should be close to 2.75 volts or the same as the BARO sensor voltage. The normal BARO input voltage is approximately 2.75 volts. This will vary slightly depending on your elevation and the atmosphere's barometric pressure.

[tinkerbell]

so how does the BARO back up the MAP from inside the glovebox?

[ProECU]

like i said earlier, I do not know EXACTLY how it operates, and I dont have a datasheet of the MAP or BARO sensors to comment further.

I ask you this, why do all manuals group these two sensors together?
Why does the code group these together?

As a stretch, why can G-sensors be mounted inside the car and give a reading also?

I dont have the answers, Perhaps you can enlighten us all !

[tinkerbell]

I know for a fact that the BARO sensor is used in the code as a backup to the MAP sensor when there is a problem with the MAP sensor.

I dont actually know what the BARO does, exactly, however it must function similar to the MAP based purely from what ive seen in the code.

see my friend - you might need to get a clue,

if you are basing your comments COMPLETELY on your *interpretation* of the code,

and i am basing it on what someone else has written - and accords with commonsense.

whilst i completely admit that i may have been wrong in this thread, maybe it is my turn to be right about the BARO?

[pornstar]

nice info tinker. question: The baro is limited to atmo level pressure ie anything less than 100kpa, 1000mbar or 1 bar absolute as u can tell that it takes inches of mercury as its reading? Or can the baro read above inches of mercury and take above 100kpa?

btw, im still thinking about how the NA engine can see "boost" without an externally generated force that makes the cylinder take above 100% VE. Theoretically, I dont see how.

Not having a go at ya dave, just asking. i think its great we having this talk :)

[ProECU]

You are not right about the BARO! :)

[tinkerbell]

thanks for that, what would you like to be enlightened about that is not contained in the excerpt copied from the tech2tech site?

it says they are the same sensor, and measure the same thing, and are used to trim the PW of the injectors, but the MAP has the most biggest influence on PW by far...

[ProECU]

Both the BARO and MAP sensors can see boost in absolute terms.
The max the MAP can see is about (approx) 1700mBar and since BARO shares the same voltages, (and i think Honda intended it whis way) so too can the BARO.

[tinkerbell]

btw, im still thinking about how the NA engine can see "boost" without an externally generated force that makes the cylinder take above 100% VE. Theoretically, I dont see how.

:)


through a carefully designed intake and only when the car is moving (probably rapidly)...

it is through 'ram air'

imagine the throttle open and you blowing air at 200km/h towards this open throttle,

similar to a turbo perhaps?

yes, it will only be marginal, but *theoretically* it is possible.

and is used most *practially* on motorbikes.

[tinkerbell]

Both the BARO and MAP sensors can see boost in absolute terms.
The max the MAP can see is about (approx) 1700mBar and since BARO shares the same voltages, (and i think Honda intended it whis way) so too can the BARO.

so what is your point?

the BARO is not the backup for the MAP sensor...

[tinkerbell]

like i said earlier, I do not know EXACTLY how it operates, and I dont have a datasheet of the MAP or BARO sensors to comment further.

I ask you this, why do all manuals group these two sensors together?
Why does the code group these together?

ANSWER: 'cause they are the same sensor, like the ECT sensor and IAT sensor are.

As a stretch, why can G-sensors be mounted inside the car and give a reading also?

ANSWER: due to them not measuring changes in air pressure

[pornstar]

im still lost. the physical limit is that the air is still atmo pressure levels of air. moving at 500kmph or 200kph doesnt change the physical mass of the air, i dont see how the density of the air can physically be compressed.
Am I wrong that the speed of the car can aid in compression of the air going into the cylinder?

[ProECU]

Hold on
I think we're arguing the same point here.
Ive been saying they have similar operation from the start.
They share too many similarities and from the code one backs up the other.



thanks for that, what would you like to be enlightened about that is not contained in the excerpt copied from the tech2tech site?

it says they are the same sensor, and measure the same thing, and are used to trim the PW of the injectors, but the MAP has the most biggest influence on PW by far...

[ProECU]

Pornstar,
colder air, holds less volume than warmer air. This contributes to Volumetric efficiency as well as other factors such as, port flow efficiency & cam design.

[pornstar]

i dotn see why a baro sensor would see kpa when seea level is the lowest level and thus anything lower is physically impossible.
the air at higher altitude would see less desnity, and ie less PW per cycle of injector. but the map sesnor can do this. why would the baro do this? >.< stupid late nite drinking owns my brain

[ProECU]

Tinker

disconnect your MAP sensor and tell me if the bitch still idles!
There's your proof right there!

[pornstar]

yer i know the density argument, but the colder air that an NA car draws into the chamber is still the same temp as ambient air outside. Therefore if we define VE as to be 100% filled cylinders, it is 100% filled but filled with 100% colder air, the reason for boost being above 100% VE is that the physical volume of the air in the cylinders equates to more than 100% of the chambers capacity compared to ambient outside.

unless u have a different definition of VE? or that im wrong that the cars speed does not affect the airs compression into the chamber!

[ProECU]

I agree with you entirely, cam overlap causes a "suck" in the piston chamber which will allow you to fill the cylinders.

[tinkerbell]

this whole thread has been a pissing comp on who has the best information.

it is highly likely that we will all be arguing about very similar concepts, if not from slightly different perspectives on the same issue...

hence the appearance that we are arguing when we are really thrashing out the info we have to develop a combined stance on the controversial issues.

poor pornstar is caught in the middle trying to grasp what we (or maybe just me) are still ourselves trying to comprehend and convey to the world...

-------

pornstar the BARO and MAP *see* things opposite, that is why the MAP is called an ABSOLUTE sensor, it tries to see vacuum as a positive rationale to make it a useful input to the MAP/RPM table

[tinkerbell]

Tinker

disconnect your MAP sensor and tell me if the bitch still idles!
There's your proof right there!

proof that there is no 'back-up' for it? proof of what?

are you saying disconnect from the ECU or from the vacuum reference? i guess it will die if you disconnect from the ecu...

it is a very important sensor in the who engines operation isn't it!

[pornstar]

I dont see this as a pissing comp at all. Im actaully enjoying thinking through all the arguments. In fact this thread was about how the same thing can be described by differeent people as different things.

the baro reads below 100kpa in absolute value, in traditional values, its feet of mercury. essentially tho, its reading below sea level pressures of ambient air. The map sensor can do this, just different expression, i guess the map can account for temps whilst the baro cannot.

[pornstar]

but i still dont see how an NA car can see boost! :(

[tinkerbell]

yeah, well whatever it is i enjoy it too...

it is good for this forum too - there are def. not enough tech discussions on here, particular involving someone of your caliber ProECU

i have found soem (biased) info on VE and ram-air:

How Does Ram Air Make HP?
This is a question we hear a lot. The answer is really quite simple and founded in science. A motor is really an air pump. The idea is to get as much air in and out as quickly as possible. However, stock motors actually do not take in as much air as their displacement indicates. This air comes into the motor under vacuum and is assisted by the weight of the atmosphere pressing down (barometric pressure). This process is not very efficient. This ratio of actual air entering the motor versus the actual displacment of the motor is called volumetric efficiency V.E.

A typical stock fuel injected motor is rated at about 85 % V.E. This means that out of the 346 cubic inches of air your motor could theoretically take in, only 85 % of that volume enters the cylinders. This translates to about 294 cubic inches of air. Some all out race motors can reach 100 % VE and supercharged or turbocharged motors actually exceed 100 % by forcing the air into the motor. Not everyone can afford a supercharger but there is definately room for improvement for the stock motor if you make it easier for it to get air into the motor for combustion. This is what ram air does.

As speed increases, the air entering through the sealed ram air kit actually becomes pressurized. This positive pressure helps to fill the cylinders more efficiency and raises the VE of the motor. As the VE increases, the motor becomes more efficient and produces more HP and also gives you better fuel economy. You will also find your throttle response dramatically improved. The motor is working less hard to fill the cylinder and is greatly assisted by the high pressure air. The faster your go, the greater the pressurization effect. This is similar to a mild supercharging effect.

The second benefit of a ram air system is that is supplies the engine with colder air than what it would normally breathe. Colder is more dense and contains more oxygen for the combustion process. For every 10 degree drop in intake air temperature, you can expect 1 % more HP. The ram air kit supplies cold air from the bottom of the car which is forced into the sealed air box. Unlike the stock system, the ram air kit does not let the motor breathe superheated air from the engine bay. Additionally, the computer detects this colder air and adds additional ignition timing. This makes more HP!

To maximize the efficiency of the ram air system, it is highly recommended that you install a high flowing aftermarket induction lid in conjuction with the kit. The factory induction lid is restrictive and will cut down on air flow. We recommend the Direct Flow induction lid which is available in a package or seperately. "

http://www.fasttoys.net/ramairsystem.html

whilst not directly stating theat VE goes to 101% with ram-air, it goes close and describes it as a "mild supercharging effect"

[ProECU]

Its been enlightening at the very least and educational as well.
I just wanted to make 1 last argument

"The manifold absolute pressure (MAP) sensor and the barometric pressure (BARO) sensor are virtually identical sensors. One reports intake manifold pressure information to the engine control module (ECM) and one reports atmospheric pressure information to the ECM. They both use the same pressure-sensing component and therefore will indicate the same voltage when both are measuring the same pressure, such as key on/engine off (KOEO)."

Based on this, (and i am no expert on the BARO as i have mentioned already) but how do these read in oposite terms as you putit Tinker, when they are the same pressure sensing component?

I Dont know, thanks for the discussion guys, time now to do some work & earn my employer some money

Cheers

[pornstar]

Dave,

that is biased :P haha

I dont see a ram air unit creating enough pressure to even fill the cylinders above 100% VE, just dont see it happening, the chances of it happening are liek those mini electric superchargers :P

I never did physics but a quick thought about this is that the pressure in the cylinder is going be equal in the chamber or less as the pressure outside. Without an external force generating pressure excess of whats in the cylinder on its induction stroke, there cannot be above 100% VE.

I do like the sales pitch of that tho haha :)

theoretically and scientifically speaking the VE of the car cannot be physically changed without creating positive pressure in the manifold, but to do that, u would need a force larger than the atmo of 14.7psi, 100kpa, 1000mbar, or 1bar absolute. following the laws of energy, there must be an additional energy used to create the force that is required to push the VE above 100%.

[pornstar]

again u can call me drunk if im wrong, cos im not 100 sure

[ProECU]

ya, its scavenging, & cam design/overlap

[tinkerbell]

Its been enlightening at the very least and educational as well.
I just wanted to make 1 last argument

"The manifold absolute pressure (MAP) sensor and the barometric pressure (BARO) sensor are virtually identical sensors. One reports intake manifold pressure information to the engine control module (ECM) and one reports atmospheric pressure information to the ECM. They both use the same pressure-sensing component and therefore will indicate the same voltage when both are measuring the same pressure, such as key on/engine off (KOEO)."

Based on this, (and i am no expert on the BARO as i have mentioned already) but how do these read in oposite terms as you putit Tinker, when they are the same pressure sensing component?

I Dont know, thanks for the discussion guys, time now to do some work & earn my employer some money

Cheers

yeah, sorry they do not 'read' or 'provide output' in opposite terms, but rather 'see' in opposite terms as one starts at one end of the scale and the other sits at the other end of the scale.

ie one will almost always be at 1bar whilst the other varies from close to zero to 1 bar...

sorry, it is still unclear and is kinda not relevent,

but you are right: they both have the same voltage output in response to the same pressure conditions...

[tinkerbell]

following the laws of energy, there must be an additional energy used to create the force that is required to push the VE above 100%.

isnt that force the movement of the vehicle through the air?

[ProECU]

Guys

just as an aside, attached is a excel file I built a whice back to give you the psi equivalent to MAP pressures

needs to be renamed to .xls

enjoy

[pornstar]

if that is considered a factor to creating the pressure dave, then u raise the problem that to be moving fast enough to create positive pressure in the manifold, the car must be moving substantially fast enough. but for the car to be moving that fast, the rpms of the car have to be high enough to propel it there, then it falls back to the problem that the head of the engine becoems a restriction :)

so in a circular way, its not possible...well in my opinion.

[pornstar]

lol evan sif u need to do that, anyone with half a brain could figure it out if they know 14.7psi is 100 kpa, 1 bar, 1000mbar!

then again we have a few nissan ppl here, so we better make it nice and simple for them

[ProECU]

Yeah you know how it is, Honours Maths grads cant do simple maths!

[2ds]

wow I like this pissing contest more than my one =D (jk)

Last time I checked I believe most air ram designes (attached to normal cars, not ones with specially made intakes) didn't manage to show any ram effect until about 150kph (or so, this could be very wrong)

BUT

not only is this possible, it looks like it's going to be part of the future of powered flight. lol, maybe it's hubris to try and use it for ground bound designs .. =)

http://en.wikipedia.org/wiki/Ramjet (ramjet)
http://en.wikipedia.org/wiki/Scramjet (scramjet)

[tinkerbell]

Last time I checked I believe most air ram designes (attached to normal cars, not ones with specially made intakes) didn't manage to show any ram effect until about 150kph (or so, this could be very wrong)


yeah, i dont think anyone is doubting that ram-air has an effect...

the unresolved question is regarding whether the ram-air can create manifold pressure higher than 14.7psi...

(i stopped looking for info on this at about midday and decided to do some work...)

[2ds]

It definately can, the question is, can the car reach the speed required to do it.

-2ds

[pornstar]

im not sure if u guys missed my last post, but clearly if u account the speeds that the car has to be going for such a large effect of this so called "ram air" the revolutions would be way too high to allow the cylinder to fill with enough air to get past 100% VE.
I just dont see if being physically possible

[2ds]

lol, i say we convert your car into a ramjet and do some testing =)

-2ds

[ECU-MAN]

this is my thoughts of Pornstars questions
I have no proof to back this so Grill me if you want.

I know the MAP sensor mesures Manifold pressure so Im not talking about what happens in the chamber. , say your driving at 110KM/h at WOT ( wide Open Throttle ) you manifold presuure will become atmospheric, your valves are opening and closing thus causing a restriction of for the air to freely flow past. now add ram air intake and the curved intake runners of your manifold. we know air can be compressed so with the restrictions from the valves causing a flow restrictionr ram air can build up in the intake manifold. also the inertia of the air passing the curved intake runners helps draw more air in.

do an experiment. drive down the street and hold a paper cup out the window with the opening of the cup facing the front. you will feal the air building up in the cup. of you cut a hole in the cup the air will escape from the back but as long as the hole in front of the cup where the air first enters is larger than the hole in the back of the cup where it escapes there will be a build up of air waiting to escape. this would be air compressing ram style would it not, and compressed air reprisents a positive pressure.

maybee this is a question for DR Karl :)

Ill be listening on Thursday :)

[pornstar]

Ecu-man the logic/thought process that u have described i agree with. The only problem is this, at say one rpm, that is one engine revolution per minute, which is 360degrees of the crank shaft turning. think about that for one second and keep that in mind.

now lets say for arguments sake that we would have to be going at 110kmph like ur suggestion at WOT. what gear would u be in to be at 110kpmh at WOT? 3rd gear or so id imagine? lets say 3rd gear in a honda and not gear 17 in a nissan. at 3rd gear in our average 4 cylinder, what rpms is that? for arguments sake, lets say 6k rpms.

at 6krpms, thats 6000 revolutions of 360 degrees of crankshaft rotation ( could be wrong im not sure how u want to express rpm, cos strictly the rpm = 720degrees of crankshaft rotation) per minute. lets divide 1 minute by 6000 to get the time it takes to get to 1 rpm.
1minute = 60 seconds therefore divide 6000 by 60 seconds to get rpms per second. i got no calculator so correct me if im wrong but by my honda brain and not my dumb nissan side that would take me to 100rpms per second. Expressed as the time for one rpm, that would be 1/100th of a second for the engine to do one rpm at 6k rpms at wot at 110mph. Now hold that thought for one second, the intake stroke of the engine is only for 1/2 of the rpms if im corect in defintion that one rpm = 360 degrees rotation. or if by defination im wrong and that one rpm is actually 720degrees od crankshaft rotation, then u divide the rpms by 4. im pretty sure that one rpm = 720degress od crank shaft, but to give ur argument a better chance ;), ;lets say its 360 degrees, so divide that 1/100th of a second for that one rpm to get the intake stroke of the engine. that is 0.005 of a second time that the engine will take in air to fill in teh chamber.... as u can see, i jsut dont see it happening....

Another argument that I have not raised is this. If speed did help with creating positive pressure with ram air or not, because it creates as u think a positive pressure built up against the intake valves, then any car after 110kmph would see positive pressure or 100+kpa right? Cos by the same reasoning, the speed of the car is the force or the main contribution to compacting the air.

It leads me to believe that unless that air is already precompacted, I dont think it would work. Ram air or mini electric fan supercharged air. For me, the intake valves on the intake when lifted create a vibrational resonance that can be used to help better atomise the fuel mix in the chamber for a better and thus stronger burn, but the drawback is that it serves as a restriction. By following my thought process I think its not possible.

Again this is a technical discussion and I am only putting my argument up. Im open to be corrected or proven wrong. I enjoy reading input from others as it really keeps the honda aftermarket weed out the bull$hit that happens in other aftermarkets, ie 13s stock silvias, claims of stock Ball bearing turbos that they saw when they "opened theirs up" when they never did and u know the usual dumbshit stuff u see from internet mechanics.

To be honest, I think the ram air thing would serve to be a restriction to the air flow at high rpm. Thats why when dyno tested, most of those electric supercharger fans that claim to make boost lsoe power. IMO it robs the air of a free passage.

maybe we could sell it to a nissan owner? ;)

[2ds]

lol. read the two links i posted earlier, ram air serves as a restriction when the vehicle reaches mach 5.

-2ds

[pornstar]

read what i wrote. teh restriction at high rpms is the head

[tinkerbell]

some good reading here:

http://www.yawpower.com/techindx.html

[h22a accord]

holy shit, i read the whole thread and i still dont understand it. All i know is that if ur map is not working ( bad sensor or wiring fault) then your car wont go lol.

[tinkerbell]

Another argument that I have not raised is this. If speed did help with creating positive pressure with ram air or not, because it creates as u think a positive pressure built up against the intake valves, then any car after 110kmph would see positive pressure or 100+kpa right? Cos by the same reasoning, the speed of the car is the force or the main contribution to compacting the air.


OK - maybe you are thinking too narrowly...

ram air in your mind is about 'forcing' more air in, but it is also about 'pulse-flow' dynamics...

i know *nothing* about pulse flow - except that you can design great headers once you got the theory down pat,

but allow http://www.pumaracing.co.uk/power2.htm to explain in brief detail (the 15th paragraph down):

You might think that it is only possible to get 100% Volumetric Efficiency from an engine - after all when a cylinder is full of air at atmospheric pressure surely that is the end of the story. What this fails to take into account though is what is called "Pulse Tuning" which is taking advantage of the pressure waves which exist in the induction and exhaust system. These pressure pulses can actually ram air into the cylinder to achieve up to 130% VE although it takes very carefully designed pipe lengths and diameters to achieve this and the effect only works over fairly narrow rpm bands - usually with a corresponding adverse effect somewhere else in the rpm range.

[pornstar]

OK - maybe you are thinking too narrowly...

ram air in your mind is about 'forcing' more air in, but it is also about 'pulse-flow' dynamics...

i know *nothing* about pulse flow - except that you can design great headers once you got the theory down pat,

but allow http://www.pumaracing.co.uk/power2.htm to explain in brief detail (the 15th paragraph down):

You might think that it is only possible to get 100% Volumetric Efficiency from an engine - after all when a cylinder is full of air at atmospheric pressure surely that is the end of the story. What this fails to take into account though is what is called "Pulse Tuning" which is taking advantage of the pressure waves which exist in the induction and exhaust system. These pressure pulses can actually ram air into the cylinder to achieve up to 130% VE although it takes very carefully designed pipe lengths and diameters to achieve this and the effect only works over fairly narrow rpm bands - usually with a corresponding adverse effect somewhere else in the rpm range.


not at all man :) this is the aprt u should look at in depoth in that paragraph

"works over fairly narrow rpm bands - usually with a corresponding adverse effect somewhere else in the rpm range."

[2ds]

okay, so that's for 130% VE, what if you only wanted to tune for 101% could you use more of the band ?

-2ds

[tinkerbell]

im not sure if u guys missed my last post, but clearly if u account the speeds that the car has to be going for such a large effect of this so called "ram air" the revolutions would be way too high to allow the cylinder to fill with enough air to get past 100% VE.
I just dont see if being physically possible

oh, i thought you wanted to know if it was possible...

sounds like it is - over a specific range of engine operating parameters...

whether it is 130% or 101% - it is still possible,

and i KNOW it is used in motorbike tuining... so it is a worthwhile effort to be put into mass production :cool:

[pornstar]

Dave, Have they got any actual evidence of this? ie, is there a motor or anything of theres that is totally NA that sees above 100kpa, because i still dont think its possible.

That physical pulse energy that they are referring to, if u think about it must be created by the atmo pressure of 14.7 psi....

If there is no evidence that tehre is above 100kpa in any of their engines i wont believe it, as it still seems impossible...

[tinkerbell]

http://www.vararam.com/reality_of_ram_air01.html

there are some formulars there, and graphs, and MAYBE some proof,

but i really dont care whetehr you belive these people...

the point is that ram air works - i hope you are not disputing that?

and BTW -


That physical pulse energy that they are referring to, if u think about it must be created by the atmo pressure of 14.7 psi....

is not true when you consider pulse flow dynamics...

ie the piston moving up and down...

[tinkerbell]

nice pic of a "ram air engine dyno"

http://www.vararam.com/images/tech/f1_engine_on_dyno01.jpg

[pornstar]

Dave, im not that knowledgeable to dispute it, but from what ive based my arguments, does it seem that it would be hard to generate any actual "boost"?

The piston moving up and down, now thats funny cause the movement of the piston going down is cause by the force of the combustion process, the piston moveing up is cause by the rotation of the crank adn teh conbustion of the otehr piston/chambers in relation to the one we are talking about. So as for air going into the cylinder the force that pushes new air into the chamber is stil 14.7 psi (the atmo pressure)...again these are my views and i could defintealy be wrong, but please correct me with why i am wrong cos im also learning.

[tinkerbell]

hence why i am providing you with some links that might help you understand...

this is becasue you are missing the point...

and if you keep on thinking that your arguement holds weight - without considereing the other possibilities, then i am wasting my time.

[wynode]

So as for air going into the cylinder the force that pushes new air into the chamber is stil 14.7 psi (the atmo pressure)...

What about the vacuum created by the piston moving down?

[tinkerbell]

What about the vacuum created by the piston moving down?

this is what casues the pulse-flow phenomena...

[pornstar]

wyn, what makes anything vacuum? what makes something "suck" air into it? In actual fact, its not a vacuum, its the pressure of 14.7psi atmo that pushes air in to fill that void, thats why im still confused by what could cause this 14.7 to increase without any increase on the propulsion side.

Dave please simplify what those links say, cos im not sure what the point is that ur referring too. As for that pulse flow phenomenon, I guess for me the point was that no matter what that void is, the air can only fill that void at 14.7 psi of pressure created by the atmo?

[tinkerbell]

wyn, what makes anything vacuum? what makes something "suck" air into it? In actual fact, its not a vacuum, its the pressure of 14.7psi atmo that pushes air in to fill that void, thats why im still confused by what could cause this 14.7 to increase without any increase on the propulsion side.


but yet it can create greater than 100% VE?

it must be a miracle!

[pornstar]

dave pls explain how in clearer simpler terms, cos i dont follow

[2ds]

this kinda maybe alludes to some of the stuff being talking about

http://conceptengine.tripod.com/conceptengine/id17.html