tuning with/or out secondaries

[cpapashley]

Originally Posted by fordrule

yeah , well tom let me know because i am in the market for a kick ass tune to put down some nice N/A numbers. and BTW i have 56 days left here. I have made up my mind to use a 65mm TB, 24lb injectors and remove my secondaries.

and will be buying the PRP , it is the next mod for my car lol, my christmas present for myself

....53 days to go......

and a prp for christmas, my I look forward to those dyno figures being quite impressive in the new year

[warmonger]

Originally Posted by ilovemycar

Off topic wuestion here Tom...but would MAF counts be a good inication of the power a car might be making?

Yes and no. Not taken by themselves it isn't but if you combine it with the measured air fuel ratio then you could make some interpolation.

IF the MAF transfer function is correct then MAF counts relates directly to airflow and then if the air fuel is correct the right amount of fuel is added. This gives you potential for power but then the compression ratio and timing can actually affect the power you see .

So I would say not directly.

[cpapashley]

Originally Posted by warmonger

Yes and no. Not taken by themselves it isn't but if you combine it with the measured air fuel ratio then you could make some interpolation.

IF the MAF transfer function is correct then MAF counts relates directly to airflow and then if the air fuel is correct the right amount of fuel is added. This gives you potential for power but then the compression ratio and timing can actually affect the power you see .

So I would say not directly.

And so MAF counts is ???

is it something to do with the voltage recorded according to the cfm figure that is flowing through the MAF???

If it is could you use it as a way of predicting potential power and make decisions on timing based on it?

....and 200th post comes up for the Australian People Moooovverrrr.....

[warmonger]

Just the scale that the PCM uses to divide up the MAFs flow range.

Usually 0-900 or 1000 with lower meaning less air and higher meaning more air.

Each count actually corresponds to a voltage point.
.1volts might be 150 counts and 2.5 volts might be 450 counts, etc.

All the way up the the 5volts which can be up to 1023 counts maximum in the software. Anyway, for a given MAF the counts/volts correspond to a certain airflow. For example, on a stock Contour MAF the 4.8 volts might be about 300 cubic feet per minute. Also it might be around 600 Kilogram/hour depending on the measuring system.
For a Ford Lightning pickup that same volts/counts might equal 1300 Kilograms/hour.

This gives a lot of resolution in the sampling of the MAF for the various airflow conditions.
So to summarize:
Maf voltage runs from 0-5volts
MAf counts can run from 0-1023
Voltage/Counts on one MAF are not necessarily equal to another MAF before you ask.

[cpapashley]

Originally Posted by warmonger

Just the scale that the PCM uses to divide up the MAFs flow range.

Usually 0-900 or 1000 with lower meaning less air and higher meaning more air.

Each count actually corresponds to a voltage point.
.1volts might be 150 counts and 2.5 volts might be 450 counts, etc.

All the way up the the 5volts which can be up to 1023 counts maximum in the software. Anyway, for a given MAF the counts/volts correspond to a certain airflow. For example, on a stock Contour MAF the 4.8 volts might be about 300 cubic feet per minute. Also it might be around 600 Kilogram/hour depending on the measuring system.
For a Ford Lightning pickup that same volts/counts might equal 1300 Kilograms/hour.

This gives a lot of resolution in the sampling of the MAF for the various airflow conditions.
So to summarize:
Maf voltage runs from 0-5volts
MAf counts can run from 0-1023
Voltage/Counts on one MAF are not necessarily equal to another MAF before you ask.

Thanks so much for that Tom, so it is not linear in operation then from what you just described. And understand the point about it not being the same for each car/maf combination. So I think I now understand all this talk about recalibrating the MAF, if you put the ford lightning pickup maf on the cougar it may well not increase the voltage/maf count in the same manner as the cougar one. therefore the air fuel mixture would be all amiss. So then to recalibrate something you would then have to overlay the correct maf/count curve for the voltages read to suit a particular engine is that right?

[warmonger]

Yes, In the computer code.

Each MAF is designed to measure a given range of airflow using only a 5volt scale.

So obviously a 1500kg/hr MAF will be far different then a 750kg/hr MAF like the ones used in the contour/cougar.

Also, the graph looks sort of like a wide parabola facing up.
The rate of voltage increase vs. airflow increase will change the way the graph looks also.

So once you know the Datapoints of airflow vs. voltage for a particular maf then you just plug it into the pcm so it knows what the voltages mean.

On top of that there is such a thing as too big or too small. Imagine a big V8 engine idling drawing more air than a 2.5L V6 engine. The bigger V8 will have a MAF with less data points or less resolution in the lower voltage ranges than a smaller MAF would have. This can just make it harder to tune.

[cpapashley]

Originally Posted by warmonger

Yes, In the computer code.

Each MAF is designed to measure a given range of airflow using only a 5volt scale.

So obviously a 1500kg/hr MAF will be far different then a 750kg/hr MAF like the ones used in the contour/cougar.

Also, the graph looks sort of like a wide parabola facing up.
The rate of voltage increase vs. airflow increase will change the way the graph looks also.

So once you know the Datapoints of airflow vs. voltage for a particular maf then you just plug it into the pcm so it knows what the voltages mean.

On top of that there is such a thing as too big or too small. Imagine a big V8 engine idling drawing more air than a 2.5L V6 engine. The bigger V8 will have a MAF with less data points or less resolution in the lower voltage ranges than a smaller MAF would have. This can just make it harder to tune.

So given that, would you say that the maf method is maybe not the best method for the larger displacement vehicles, being better for the smaller engines say less than 3.5l or something like that? or does it come down to the useage of the vehicle that would determine which method of air calculation should be used.

I am reading a book from the library at the moment that seems to indicate that the alpha-n (throttle position) is possibly better where fuel consumption and efficiency is not really so important and air stacks are used where lots of air is the name of the game. The reason this thought was running through my head was because of that other discussion on having the vehicle run off a throttle body where the secondaries were (ie if you were really to open up the vehicle) If you knew how to modify a tps to read its voltages like a maf/count (in other words you had worked out the graph etc) and then had the tps feed the maf sensor you could basically do without the maf? or am I thinking the wrong way here?

[warmonger]

Not at all. The MAF just needs to be sized correctly to the engine. The MAF system is far superior to speed density systems I would say.

The only area where a speed density system (that's the one that used throttle position and manifold absolute pressure MAP sensor) is better is in the simplicity of it.
MAP systems use three basic sensors for most everything: temperature, throttle position, and manifold pressure (the sensors are cheaper too). The airflow does not have to be routed through a common point (the stacks you pointed out) as it does with a MAF system. Those three sensor provide the bulk of the data for everything else can be calculated or derived from them. There are tables of data in the PCM memory that are referenced to complete these calcuations that are a "best guess" to the conditions for the engine. All of this is used to determine the density of the air and therefore extrapolate the Mass of the air in order to add the correct amount of fuel. Because of this the calculations are not always accurate hence you can get driveability issues more easily with this type of system.
The MAF makes it so easy because it directly measures Air Mass so there is no doubt about it if it is calibrated correctly.

I would always use a MAF system first unless it wasn't available or if it just wasn't practical as in velocity stacks or the air intakes used on drag racers.
Some engines swallow so much air that there aren't any MAFs big enough....

[cpapashley]

Originally Posted by warmonger

Not at all. The MAF just needs to be sized correctly to the engine. The MAF system is far superior to speed density systems I would say.

The only area where a speed density system (that's the one that used throttle position and manifold absolute pressure MAP sensor) is better is in the simplicity of it.
MAP systems use three basic sensors for most everything: temperature, throttle position, and manifold pressure (the sensors are cheaper too). The airflow does not have to be routed through a common point (the stacks you pointed out) as it does with a MAF system. Those three sensor provide the bulk of the data for everything else can be calculated or derived from them. There are tables of data in the PCM memory that are referenced to complete these calcuations that are a "best guess" to the conditions for the engine. All of this is used to determine the density of the air and therefore extrapolate the Mass of the air in order to add the correct amount of fuel. Because of this the calculations are not always accurate hence you can get driveability issues more easily with this type of system.
The MAF makes it so easy because it directly measures Air Mass so there is no doubt about it if it is calibrated correctly.

I would always use a MAF system first unless it wasn't available or if it just wasn't practical as in velocity stacks or the air intakes used on drag racers.
Some engines swallow so much air that there aren't any MAFs big enough....

That explains why some of the aftermarket systems look to the map type systems, simplicity. Makes lots of sense. And I can also understand why driveability is so good in the maf cars over the map. Actual readings certainly always beat any guestimate tables.

But to entertain my thinking on this for a moment. Assume a change to a CAI on a maf based vehicle, I can see how the maf would pick up the change in air density immediately, with the increased voltage needed to maintain the hotwire. So the increase would then mean more fuel can be put in and therefore more power.

But with something like a map I cannot see how the system would pick up that there has been a change. Unless there was a change made to the parameter tables. Or am I just missing something here???

[warmonger]

Originally Posted by cpapashley

That explains why some of the aftermarket systems look to the map type systems, simplicity. Makes lots of sense. And I can also understand why driveability is so good in the maf cars over the map. Actual readings certainly always beat any guestimate tables.

But to entertain my thinking on this for a moment. Assume a change to a CAI on a maf based vehicle, I can see how the maf would pick up the change in air density immediately, with the increased voltage needed to maintain the hotwire. So the increase would then mean more fuel can be put in and therefore more power.

But with something like a map I cannot see how the system would pick up that there has been a change. Unless there was a change made to the parameter tables. Or am I just missing something here???

No, the MAP system still works just not as exact. The tables don't change just the variables in the equation.
It will see the change because the MAP system will sense a change in pressure and temperature and therefore extrapolate the higher air density.
If the cold air system actually works then it would deliver cooler air to the engine. Lets assume that the manifold pressure stays constant, then it would still indicate to the PCM that the air is more dense because it senses cooler air.

So both systems work. However, have your temp sensor, or your MAP sensor, or your tps go out on your speed density car and the thing will amost not drive at all!
Go out to your MAF system and unplug the Temp sensor, or the TPS, and the thing will still run almost perfect but with a check engine light.
Or, assume all your sensors are working but the MAF is not. Then the MAF system will be able to revert to a speed density system through extrapolation of manifold pressure. It will still run reasonably well.

Go out and try it, unplug just the MAF and then start the car and watch it will run pretty good.
In fact, that is one way to tell if you maf is dead and giving bad signals. You can unplug it and start the car. If the car runs better then you need to look into MAF related issues like vacuum leaks, bad mafs, etc.