Did you just totally miss the whole point of what I said? My point was that NONE OF THAT MATTERS as long as it works. Is it nice to know? Yes. Does it really matter when you just want to throw a baseball? NO.

That was the whole point! Thanks for helping make it, I guess?

I'll take the physics discussion to PM as I hadn't intended to "discuss" it here.

-Adrian

 

even your warning suggested that the endless-plunkering-way was better or at least "useful" and in the end you concede... what works works...

btw < that face is pretty cute....

 

I had only intended to suggest that it was more precise and that such precision is not always necessary, like in the case of a baseball.

 

Wow... all this physics and crap for nothing.

It seems it is another debate about MAF vs. Speed Density.

Speed density can make more power. It is simple, there is less of a pressure drop and less restriction. This makes the turbo spin easier, making it push harder, etc, etc...

A MAF system is technically and theoretically more accurate... does this do anything in real life... NOPE. Absolutely not. You could tune a speed density car to run the exact same as a MAF car. The MAF car, no matter how you look at it, is less reliable and/or creates more of a restriction (less power).

On top of that.... the extra accuracy gained by the MAF could be guessed within a 90% accuracy through multiple maps and the other 10% wont make you more power... at most it would give you better throttle response. Now honestly... who cares if you press the gas and for that .001 seconds your car may run either rich or lean. No one would. The difference of this in a 30 minute course would be un-measurable. Especially considering you would gain that .001 seconds back the first time you got the high RPM at WOT.

The extra precision is worthless, as SaabTuber stated.

 

The MAF actually reads the air, the MAP estimates it, why not upgrade to a Z06 MAF, VERY unrestrictive and more accurate, best of both worlds. Also get a blwo through Maf.

 

Pressure drop? In a zero pressure area? Making it push...harder? Is this what members should expect of a "technical explaination" on this forum? I certainly hope not.

 

Although I agree that most of the added precision of a MAF sensor is wasted on extremely high-hp engines which see nothing beyond track use, there are some advantages beyond just throttle response.

It's just that the added benefits are more closely related to adaptability (IE: altitude/part changes) than actual power-making.

There is one thing for which I love MAF sensors, turbo control! Because they measure the air BEFORE it goes through the turbo, boost spikes are a non-existant problem with MAF-based boost control. (Unless your WGA sucks.)

But, for Evo's, MAP is probably the best way to go when you go beyond 500 hp, or when you car is not going to be daily-driven. (Or when you change altitudes regularly.)

So the precision of a MAF probably isn't needed 90% of the time ...

 

Pressure drop due to the (extremely small) restriction posed by the sensing element.

It makes the exhaust gasses "push harder" on the turbine wheel to give a specific massflow, etc etc etc, slightly lowering VE.

It's really not a big deal with a good MAF setup though. It's just something to consider.

 

It is scaring me that people are talking about tuning and precision not being important. A lot more engine failures using the AEM EMS vs. the Maf and the stock ECU++++.


I still think a 3.5 MAF from a Z06 will not only flow enough power to match that of a speed density, it will be more accurate.

 

Having less of a restriction on the intake side may provide less of a restriction for the turbo, but it does not actually create a pressure drop between the MAF and the turbo, because that is a zero pressure zone. The only possibility is that the pressure change occurs between the atmosphere and the intake pipe. In other words, air isn't being forced into the turbo, its being sucked in by the turbo.

and I think she was saying that the turbo will "push harder" if I understood correctly. This is completely beyond me.


Yes, if at any point the MAF sensor is a restriction, more power could be afforded by removing it. How much power, when we are talking about a 600-700hp evo? Not much. Not enough to warrant removing it. *Edit* I wanted to expand on this... The VE of the motor will change over time, as rings wear, and carbon deposits. With a MAF equiped car, this unavoidable change is accounted for over time by the sensor. However, with a car running a MAP sensor, this change is not accounted for automatically by the car, it is accounted for by the tuner. The tuner must slightly detune the car to account for the loss in VE over time, in order to prevent knock weeks down the line as the motor changes. So with that said, that 10 hp difference you see by removing the MAF on the dyno is negated by the amount of detuning that must occur in order to keep the car safe. So yes Trina, a car running off a MAP sensor can be tuned with in 90% precision of a MAF equiped car, but every day after the tune that 90% will lessen, and 1 year down the line you will find yourself with perhaps 75% of the precision that a maf car has.

 

It creates a pressure-drop between the atmosphere and the turbo. "Zero-pressure-zone" has no meaning here. Anywhere fluid flows, there is static pressure drop. It is necessitated by conservation of momentum in the kinetic theory of gasses.

The pressure change occurs across the MAF sensing element because it causes turbulence in the flow. Air is NOT an inviscid fluid either. It has viscosity. Disruptions in the flow, inviscid or not, cause restriction.

If I'm not mistaken, the technical term is "head loss".

Turbochargers push air. Though it may not seem so simple to you at the moment, "sucking" and "pushing" have essentially the same meaning in a fluid. "Sucking" is merely pushing mollecules out of the way so that the other moving mollecules take their place. Because those mollecules are moving at well over a thousand miles-per-hour ... the displacement makes it appear as though it is being physically pulled in. In reality, it is being "pushed" in by the gas behind it.

All of the work the turbocharger does is done by "pushing" the turbine wheel with backpressure- that force "pushes" air into the engine ... literally.

It depends on the size of the pipe to which the MAF sensor is attached. In some cases the MAF sensor will not work well with a larger pipe (even after tuning. In those cases, MAP is highly preferrable.

What I would put forth is that the decision to move from MAF to MAP should be based on an individual setup and whether that setup can truly benefit from the increase in flow.

Some setups might se more benefit in the precision of the MAF. Some might see more benefit in the flow from a MAP. It's an individual's decision and I think people shouldn't get carried away with "accuracy" ... or "flow".

Find what works best for you ...

 

..

 

yes, three months ago

clearly some temporal distortions at work here - that poor baseball is ****ed

 

Hah. Ok, fair enough. I mist misinterpreted what you said.

Not really a restriction in itself. The Bernoulli effect would still exist even in a truly inviscid fluid which has no resistance to flow due to the effects of conservation of momentum. The Bernoulli principle basically just says that, unless you raise the temperature, moving a fluid does not change the average speed of the particles within that fluid. As a result, if you give those particles an ordered componant of motion (dynamic pressure), their random componant of motion (static pressure) has to drop to conserve total momentum (total pressure).

Unfortunately, as I am going back to school, my car is 500 miles away and not an Evo.

But I have some friends who have done/seen intake testing on the inlet tract of the B235R from the Saab Viggen. One of the people was referencing formal research. It's interesting to note that, in his case, the most important thing to measure wasn't pressure drop, because you'd need to know the velocity of the gas at that location to factor out the Bernoulli Effect. Instead, temperature was measured. Any restriction dissipates energy into heat through the viscosity of the fluid, so a restrictive pipe actually heats the intake gasses, which makes changes in heat a great way to determine overal flow efficiency.

My other friend was measuring intake restriction in a much less formal way. I had to remind him that the pressure drop across a particular part isn't very meaningfull if you do not know the respective velocities of the intake gasses at each point of measurement. Just because you have a low static pressure due to high velocity does not mean you have a large restriction.

Here are some things I would humbly suggest being considered for any intrepid souls out there actually wanting to measure the effects of a restrictive intake:

1) To find the amount of pressure-drop due to the Bernoulli Effect at any given point in the induction system, find the massflow of the system as a whole (it doesn't matter where, it's conserved) find the temperature at the location you are measuring the pressure and measure the approximate cross-sectional area. That should allow you to find the pressure drop which "should" exist due merely to the Bernoulli Effect. Once you do that, the difference between that pressure and the measured pressure will be due to restriction alone.

2) Try to find a way to record Wastegate Duty Cycle. One of the tell-tale signs of a restrictive intake is a lower wastegate duty cycle as the turbine needs more of the exhaust gas passing through it in order to drive the compressor. (IE: the turbo must "push" harder)

One of the problems with installing an intake on the Saab B235R is that, though the ECU can adapt to more restrictive setups which decrease the WGDC, it does not adapt well to less-restrictive setups which raise the WGDC. When the ECU's adaption factor creates an excessively high WGDC, the ECU lowers target airmass to avoid a potential boost-spike. That actually causes a loss in power which is often seen in that engine with the addition of an intake. (Similarly with TBE and high flow intercoolers, which also raise the WGDC.)

3) Remember that the intake flow has a "shape". The highest velocity regions will be on the outside of bends, or in the center of straight pipes. This can affect your readings sometimes. In some cases, that means you might want to measure the flow on both sides of a particular section of pipe.

4) Make sure you are measuring static pressure and not total pressure. If you point the probe into the flow, you will get a very different pressure reading. (Thank you captain obvious. heh)

Anyway, those are just suggestions. I feel that, if you are going to "prove" whether an intake/MAF is restrictive or not, you need to be sure your readings are meaningfull. If you aren't scientific about the process ... your data may not be very usefull. But that's just my oppinion, so take it only at face value.

-Adrian

 

Errr ... I can't believe I didn't mention this before ... but, for parts which are properly removable, there is a REALLY easy way to measure the restriction with pressure drop alone. Measure the pressure with the part connected ... then without the part connected. Easy as pie.

The problem is that not all parts can be removed without fudging up the data by adding other parts to replace them ... yadda yadda yadda. Like if you want to find the restriction of the MAF alone, you have to be able to remove ONLY the MAF without changing anything else about the setup. That can sometimes be tricky.

But yeah, sorry for not mentioning this in the last message!