l2r99gst

iTrader: (2)

Of course I am using the ideal gas law. And, no, you still can't have greater than 100% VE. Again, it matters on what your pressure/temp references are for befroe and after and if you are taking these changes into account into your VE calculation. A 2L container can only hold 2L of gas. That container isn't changing volume. The mass of air may change due to pressure or temp changes from before to after, but the max volume a 2L container can hold is 2L.

But, there is no need to argue. Some people use 100% as a VE max and some people don't because they don't incorporate the changes into the VE calculation. Neither way is wrong as long as you know what you are doing and where your values are coming from and how they will be used in subsequent calculations.


It looks like tephra is using a mass airflow as the map axis like they are now in the stock ECU code.

But, your comments above aren't 100% correct anyway. If you used straight MAP and RPM to calculcate fuel, and only used VE to adjust, then your fueling would be way off due to temperature/weather changes. You would need a seperate 3-D for temperature correction, since your map doesn't have that incorporated into it.

I think that was the whole argument between you and me pages ago about the axis. Using MAP as an axis does NOT automatically account for density changes due to temperature changes as you are indicating. A mass airflow axis does.

03whitegsr

iTrader: (8)

l2r99GSt, temperature compensation is already taken into account by using the ideal gas law in the first place. Temperature compensation is taken care of in a process that runs in the background. Any temperature compensation beyond this is strictly to account for how the motor reacts to the temperature (ie detonation threshold with respect to air temps).

You are also missing the point on the VE. You have pressure pulses that travel down the runners and back. The pressure pulses can be well above the plenum pressure. These pulses can effectively push more air mass into the cylinder. True, the cylinder will not hold more then a given volume at a given pressure, UNDER STATIC CONDITIONS. But the pressure in the motor is not constant. You have inertial effects that can improve or kill charge fill efficiency. It is a dynamic system. It is these dynamic conditions that allow for VE changes.

You cannot deliver fuel based on these dynamic conditions though. The ECU simply doesn't operate at a high enough speed and it's unnecessary anyway because the motor will behave in a predictable manner. Instead, you have to look at manifold plenum pressure (much more stable then runner pressure) and use that as your basis of pressure reference. This is how you get >100% VE because VE is based on manifold plenum pressure, and not runner peak pressure, or the integral of runner pressure, or anything else.

l2r99gst

iTrader: (2)

OK, I don't really want to argue with you anymore, since it's not helping this thread that much....but a MAP axis vs RPM does not take temperature into account. A mass airflow axis does.

Also, as far as VE, you are agreeing with me, but you are trying to word it differently. A volume of space is a volume of space, period. If you want to calculate a VE, or filling efficiency, and you keep your before calculated temp and pressure the same, then yes, you can have over 100% VE. But, you are never exceeding the fixed volume that you are dealing with. You mass airflow may be over 100% of what you expect, but it is due to either increased pressure or decreased temperature...most always a slight increase in pressure, as you have mentioned.

I think it's safe to say, let's just table this argument until tephra has a chance to start working with his new sensors and coding something up for people to play with.

03whitegsr

iTrader: (8)

"That's what I said...Booty Traps"

dudical26

iTrader: (17)

I have a question about IAT sensor placement with meth injection but I don't want to clutter up this thread with that info. There are tons of people in here that are super knowledgeable about speed density so if you could please take a look over here at this thread I created.

https://www.evolutionm.net/forums/sh...40#post6278740

l2r99gst

iTrader: (2)

Is that from Goonies?

dan l

iTrader: (3)

In reply to the VE discrepancies.

I know it doesn't make sence, but a NA motor can achieve more than 100% VE utilizing the inertia timing of the incoming intake charge. Even with a manifold pressure of 0 atmospheric the tuning of the intake inertia charge allows for more than 100% VE.

Doubling boost does NOT double VE. If you quadruple the amount of oxygen molecules in the cylinder with double the boost then you have doubled VE.

I know these concepts are confusing, but they are important fundamentals in how say a stock NA honda map is set up. It would be nice to have numbers that make sense with the rest of the standalones out their.

l2r99gst

iTrader: (2)

This implementation isn't going to be like most standalones out there. That's the whole point.

And I do know that NA motors can have over 100% VE. But, that is being measured from atmospheric pressure and temperatures. The 'more than 100%' VE is because the cam timing/tuning can slightly allow a pressurized cylinder. So, you have more 'than you expect' from your standard atmospheric pressure and temperature.

Like I said many times, it simply matters what your reference is. But in reality, you are never over 100% VE. VE is talking about volumes, not masses. A cylinder is a fixed volume...it doesn't change. It can't be more than 100% full from a volume standpoint. The mass can change a lot with the same filling percent, though. So, the 'mass efficieny', if you want to call it that, can be well over 100%. That's what our turbos do, as a matter of fact and what properly tuned NA cars are doing. They are putting slightly more mass of air than is expected.

I thought we agreed to stop arguing about this, though.

RoadSpike

iTrader: (5)

But air volume is air mass by its very definition. The ideal gas laws completely show this. Air volume isn't like a liquid where you physically fill up the proverbial cup air always takes up all the space it can so it achieves uniform pressure. By your definition any air in the chamber is always 100% filled. If you didn't use some reference pressure to determine the gases volume you'd never know how much you had.

The Ideal Gas Law PV = nRT

Where:
P is pressure
V is volume
n is the number of moles
R is the gas constant
T is the absolute temperature

Example:
For example, an AL sized cylinder is filled with nitrogen at 2000 psi. What is the gas volume of nitrogen from the cylinder?
P (1) is 2000 psi
V (1) is the internal volume of AL cylinder 29.5 liter*
P (2) is 14.7 psi
V (2) is the unknown volume of gas

Solving the equation above for V (2) gives:

V (2) = [p (1) x V (1)]/P (2) = (2000 psi x 29.5 liters)/14.7 psi = 4013 liters (approximately 140 cu. ft.)

tephra

iTrader: (6)

Guys - where should I install my IAT.

Initially I was going to get it tapped into the IM.

Will there be any difference in getting it installed into the UICP (like in Mrfreds thread)

Cheers
D.

cossie1

Over here when the guys have switched to aftermarket ecu's and needed to use IAT's they have had them put in the UICP near to the throttle body and it seems to work fine

MR Turco

iTrader: (16)

is there any reason not to install it in the IM?

mrfred

iTrader: (50)

There are two things which may affect air temp in the IM vs in the UICP.

1) During vacuum conditions, the venturi effect due to the throttle butterfly will cool the air. There is a proper name for this effect, but I can't remember it at the moment. The cooling effect can be strong enough to cause icing on the throttle body on some cars (my old VW bug would freeze bad in the winter).

2) The coolant circulating in the throttle body may cause a slight heating.

These will only matter for off boost performance, but may effect how well the engine runs when cold.

cossie1

Only that if there is nowhere to put it, it's a pita to remove the IM and have it tapped, compared to removing the UICP.

MR Turco

iTrader: (16)

But wouldn't that mean measuring the temp in the IM would be a more accurate measurement of what the air temp is going into the motor?