hrcslam

Ummm, the PCV system gets it's pull 2 ways. One, from the intake vacuum at partial or close throttle (in this case the filter and MAF have zero effect on the system). Two, from Bernoulli's principle at WOT (in this case the filter or MAF have zero effect on the system). The only caveat to the second way it get's it pull is the location of the vent line has to be correct, or you get nothing (also in this case the filter or MAF have zero effect on the system).

When talking about air, volume IS mass. Hence MASS air flow sensor. The MAF measures the volume (or mass) of air the engine is actually taking in, thus allowing the engine to apply the correct amount of fuel (by mass) into the engine (along with the MAP and IAT sensors). Power is effected (not created) by this and about 100 other things.

hrcslam

ANY MAF that isn't stock (or a MAF located not in a stock location or within stock plumbing) will require a tune. The important part here is air flow accuracy. A MAF's job isn't to make power, it's only to ACCURATELY count the amount of air the engine is taking in.

The stock MAF on the LT1 obviously has enough to support just about any build out there. Or, instead of getting an expensive MAF that requires a tune. Ditch the MAF and go SD and do a tune. If you think an SD tune is only for WOT you are probably just a poor mechanic that blames his tools.

kingtal0n

iTrader: (1)

volume is not mass my friend. turbos, compressors, engines, flow volume, what I mean is, their displacement does not change, a 350cid engine will always move 350xrpm/3456 cubic feet of air per minute, plus or minus factors which affect Volumetric efficiency. MAF sensors do not read volume, they use a wire that maintains a specific temperature (a "hot wire") and report the voltage necessary to maintain that temperature to the ECU which has the parabolic voltage curve correlating to mass of air (not volume). In a stand alone ECU this curve is adjustable, such that one might "port" a maf sensor, then test bench it and re-write the voltage values down (you can use any kind of hot-wire in any kind of tube and call it a maf sensor, as long as you can test bench it for the output signal you can use it on any ECU which accepts that signal, or any scale you desire provided you can provide a means for it to correlate fuel or timing adjustments. In other words, exactly some number of volts or Hertz from any hot-wire sensor, lets say 3.578 volts, can be whatever scale on a timing or fuel map we desire since we can write the input value. )


Power is how well our engines can use peak mass flow of air molecules per unit time, or the point at which an engine uses the most air molecules the most well (trying to be as correct as possible. you can have an engine with a peak power at lower rpm than expected if it does not use the air molecules as well at higher rpm for some reason, mechanical or otherwise). This can be calculated based on the pressures the engine produces, i.e. an engine whos intake manifold and head ports are sitting at atmospheric pressure will ingest it's full displacement difference (difference between the atmospheric pressure and any vacuum signal (low pressure signal) produced by the engine), plus or minus any air velocity adjustments due to the nature of the valve timing and piston location during valve events and many other factors which nickle and dime one way or the other. Anything that gets in the way of fulfilling the pressure difference (causing the cylinder to become atmospheric or to whatever we set our hearts desired boost level to) or adjusts the pressures before or after the engine will affect final total power, this can be an air filter, exhaust gas pressure, too small of a head port, tight bends, incorrect plumbing size, too thick of an intercooler core, too small of a maf sensor, etc... its the same as saying the tube is too small to allow the movement of so many air molecules at a given temperature without having a negative consequence to flow rate (friction causing raised temperature, or pressure increase due to restriction, for example as air molecules approaches the speed of sound there are consequences to flow I am told). Temperature is the reason for all of this explanation- the lower temperatures allow more air molecules to fit and flow through a given tube, as you turn up the power output you need more air molecules per unit time. That can come in the form of improvement to volume OR mass, i.e. we can spin the engine higher for more volume, or, we can try to increase the mass of the air we are working with, by reducing temperature or increasing pressure where it flows through the plumbing on it's way to the engine. Since air fuel ratios are calculated in moles of fuel to air ratio, which is a mass per mass ratio of matching units, thus when we say maf sensor we mean a sensor which can directly correlate fuel molecules to air molecules ratio (as programmed by us, which can be done wrongly. So having one is no guarantee of anything). I think I understand what you meant by "volume is mass", we should be careful however and really specifically use the unit which fits the situation for best viewing, that molecules per unit time is the feature of power output and maf sensors, where volume is just another way to view the flow rate without considering temperature for situations where we already know that we want to minimize temperature (compressor discharge situations) but we are more curious about flow rates in cubic feet per minute so that we can tell if the compressor is going to be spinning too slow or too fast.




I am not really sure what you are getting at in your post but if you are more clear with a question maybe I can help you where you are having trouble.

Ill help you with this,
Air only moves when air pressure is higher or lower nearby. If the pressure here = the pressure there, then there will be no net movement of air molecules, besides the traditional quality of entropy which drives gas molecules to seek the ends of their containers.

So consider now the above picture. The air pressure after the air filter = the air pressure of the atmosphere, if the filter is "perfect" (no filter and no restriction) thus, there will be no net vacuum here, thus, the air molecules will move out of the engine when there is any measurable blow-by (and the pressure in the crankcase exceeds atmospheric pressure). This is not what we want, because it means that the crankcase is "pressurized" which is bad for performance, economy, and oil quality. Instead, the OEM manufacturer derives this position as a vacuum source by depending on a slight restriction of the air filter to generate a slight pressure drop (before the turbo inlet), thus the air pressure after the air filter becomes lower and lower (below atmospheric) as the air filter becomes more and more restrictive. If we cap off the air filter completely and spin the engine then we will have a full vacuum signal there, as an extreme example. NOW that we have a lower pressure than atmospheric in this position, we can "positively" draw air molecules from the crank case (PCV action) and thereby lower the crankcase pressure to below atmospheric.

hrcslam

I think you misunderstand. For the purpose of an internal combustion engine and air flow, Mass and Volume are interchangeable terms because of how the ECM is calculating target fuel flows. Yes, mass and volume are different units of measurement, much different. But, for what we need in tuning an engine, it's pointless to differentiate the two.

On to the PCV thing. You are way wrong friend.

The air filter provides zero effect on PCV. Neither does the MAF. The sole purpose of the air filter is to prevent particulates that can damage and engine from entering. That is literally all it does, saying it does any more than that is wrong. Remove the air filter and the PCV system will work flawlessly.


The sole purpose of the MAF is to measure how much air is coming into the engine (it doesn't do it alone either). Saying it does more than that is also wrong. If the MAF has a primary effect on the PCV system then the MAF would pre-date the PCV. But it doesn't. Remove the MAF and the PCV system will work flawlessly (so long as your VE tables are good, as an engine running too rich or lean will definitely effect intake manifold pressures along with crankcase pressures).

The MAF doesn't make power, it only provides the ECM with an estimate on how much air (in mass or volume, which ever term you prefer to use) is entering the engine so the ECM can calculate how much fuel needs to be injected. I say estimate because it cannot accurately state exactly how much mass is entering the engine without also knowing the ambient pressure (MAP) and temps (IAT). It can get close (so long as it's calibrated correctly), but it cannot get it perfect. Hook up a wideband and check your AFR's. Now disconnect the MAP and see it change, then try it with the IAT disconnected, then try it with both disconnected.

As to your input on how an engine makes peak power (I know how all of that works), all of that is not a result of the MAF (although the MAF can effect it, along with the MAP, IAT, etc. etc. etc.). It's easy to prove really. My car made the exact same amount of RWHP and TQ with the MAF than it did without. The curves were identical. If the MAF made power, it would've beat my SD tune. But, it didn't. Because all the MAF does is give the ECM an estimate (a very good one) of how much air the engine is using at that particular moment. An estimate that also needs the MAP and IAT to do so, accurately. Remove the MAF and use the IAT, MAP, and RPM's and you can build a VE table (which the LT1's like even in MAF mode) that will render the MAF almost completely useless and more of a restriction to the air entering the engine than a tool for the ECM to use.

Beyond that, the MAF does have advantages (which is why OEM's have gone to them). They adjust to environmental changes better than an SD tune does. They also adjust to small modifications without needing a re-tune of the ECM (cat-back, etc.). They are much easier to tune than a VE table as all that is required are data logs at each RPM and not at each RPM/MAP and BLM cell. The MAF can also keep the engine running if the MAP fails, but an SD tune the car wont run. A MAF also fuels better without the IAT than the SD tune does. This list goes on. Lots of benefits to a MAF, the biggest being vehicle reliability. A MAF tune on top of an SD tune makes for a very reliable vehicle, which is why all new cars come from the factory with both.

Shownomercy

iTrader: (1)

https://ls1tech.com/forums/forced-in...ressure-7.html

Don't argue with the durp.

kingtal0n

iTrader: (1)

You take the air filter off and measure the pressure there- it will be the same as atmospheric, with me so far?

During boost your crankcase pressure is above atmospheric.

How can air pressure move molecules from a low point to a high point? It cannot, by itself. Thus pressure exits the crankcase to equalize with atmospheric, exactly as if you have an atmospheric vented crankcase (NO PCV ACTION).

I recommend a book in classical physics for your next read.

hrcslam

Um, you obviously have no idea how this actually works. There WILL be a DROP in pressure between ambient and the air in the intake tube even without the filter so long as the engine is running. Period. If the engine is off, the pressure inside the intake tube and ambient will be equal, filter or not. Period.
It is so without boost too! Crazy thought right? The whole 800-1500psi of combustion pressure somehow getting some of that past those pesky little piston rings.


This makes no sense. If you are talking about a low PRESSURE point to a high PRESSURE point, it doesn't.... ever. It always goes from high pressure to low. Just like temperature always goes from hot to cold.

You obviously have no clue on how the PCV system works, or why. You also seem lack the knowledge on why MASS is used in the ECM and why it's pointless to differentiate that from volume when it comes to air. The point of all of this is that it doesn't matter if you call it mass or volume or air density or moles or molecules or electrons and protons or nitrogen/oxygen. The sensor will still need to be accurately calibrated and the way to do that is the same regardless of what you want to call it.

You sir, may need the "Classical" physics book for your self. You may also want to brush up on your fluid dynamics a bit too (the whole air in motion thing, you know higher velocity = lower pressure). While you're studying up to have this discussion on a level with everyone else here, go a head and read up on how the PCV system works too, this way you look like less of an *** when you post something here.