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proof that there is no 'back-up' for it? proof of what?Quote:
Originally Posted by ProECU
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!
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.
but i still dont see how an NA car can see boost! :(
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"
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
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%.
again u can call me drunk if im wrong, cos im not 100 sure
ya, its scavenging, & cam design/overlap
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.Quote:
Originally Posted by ProECU
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...
isnt that force the movement of the vehicle through the air?Quote:
Originally Posted by pornstar
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
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.