Please Read --> MAF Sensors with the EMS - Great Thread!

[Mello]

It sounds like everyone is concerned about restrictions.  I must have missed something somewhere.  I didn't know that you had to flow all of the air through the MAF before it went into the motor. (Hint).

[WadZii]

only flowing part of the air through the maf seems like a bandaid fix to me.  isnt that the point of going to a standalone... to get rid of the bandaids and do it right..  anything in the intake will be a restriction and removing it will always make more power, be it 1 or 100hp.  if mafs are so good then how come none of the fast guys use em.  name me one 1000hp supra that uses the maf.. you dont see us honda guys switching to mafs b/c they are better.  if my experience with nissan's is any indication then bigger mafs are expensive.  you can get a map sensor and a iat sensor for way less and never have to worry about upgrading again

[Mello]

Remove your Throttle body.  I think it is also causing a restriction in your system.  This mod is good for at least 10hp.  Works wonders for making power.  As for a bandaid fix, go do some homework on MAS systems and how they are implemented before you offer your shade tree mechanic opinions.

[fusionsport]

the thing about the MAF in a high performance situation has already been covered.. they restrict flow and at higher flow levels lose resolution, they are not always linear and can require vast amounts of tuning to get right. This is one of the reasons that a lot of aftermarket units give end users trouble or do not deliver as promised. Having used several Granatelli, Huntley, Wolf, etc MAF conversions or upgrades.I have in every instance been dissapointed in the performance. Using a MAP sensor and appropriate  trims I have always recieved better results than with a MAF. It does take some time to get these tables optimized, and I think a lot of casual programers overlook or do not understand these trim and tables, but a little time and effort really rewards.

[SA]

All the EMS does is take this sensor’s output signal (the EMS input) and makes calculations with it to determine a calculated response (EMS output) for control.  Neither one of these setups has to output any real world values to control a vehicle.  As long as it is properly sized to cover the operating range of the motor it is being used on it can be tuned (hence percentage values).  The actual flow or pressure is just for us people, not the EMS.

Couldn't have said it better myself.  Thanks Mello.  

I'd like to add one important thing though.  The calculation used to determine load from a MAF sensor is very different than the one used for a MAP sensor.  There seems to be this misconception that the EMS treats the outputs from MAP and MAF sensors the same.  In other words just read the output from the MAF and compare it to a min and max value to determine a % full scale reading.  This is not true and simply would not work.

Do a search on the Karman Vortex MAF sensor.  You'll probably find a lot of recent information...especially considering the initial problems we had with this function using 1.03   .  There's a lot that goes into this calculation.  Since that problem has been addressed, I think most users would agree that there's nothing wrong with these sensors or the method used by the EMS to determine load based on their output.  The reading is very stable and as long as the range is scaled correctly, the system works very well.  There's always limits however.  You will not be able to stuff 1000 HP worth of airflow through a stock DSM KV MAF sensor.  At some point, you will exceed the range of these devices...unless you install more than one   .    


SA

[anoldsman]

SA Wrote:

I'd like to add one important thing though. The calculation used to determine load from a MAF sensor is very different than the one used for a MAP sensor. There seems to be this misconception that the EMS just takes the output from the MAF and compares it to a min and max value to determine a % full scale reading. This is not true and simply would not work.

I found my error regarding the Ford MAF.  I found the calibration table for the MAF and it does look like right.  How do you use the multipliers to obtain air flow from them?  I would think that a known max. or min. airflow would need to be entered.

On KV MAF's how does it work?  If it is not min to max to determine %, then how is it done?  The only data that we are allowed to enter is max flow and sample rate.  I assume that you would need the response curve (flow curve) in order to properly set it up.  If this is known than just flow testing the MAF would give me all the data that I would need.

Regarding the GM applications that you are currently working on, can you post how you are reading the frequency and how you are seting it up?  I could use that data to then install the GM sensor and remove the restrictive 1G KV MAF.

Chris

[chevyeater]

SA- Why do you refer to the KV as a MAF?

All you folks worried about the restriction a MAF creates, I have two words- blow thru.

I'd like to run my car like most modern vehicles. A MAF (I prefer the latest GM sensors) and a Speed/Density "throttle flow" (NOT MAP alone) backup check and balance system. May be pie in the sky though.

[SA]

SA- Why do you refer to the KV as a MAF?

Because the Karman Vortex flow meter is actually three sensors in one.  The main output is a frequency signal that is proportional to the VOLUMETRIC FLOW RATE through the sensor. The second is a pressure sensor and the 3rd is a temperature sensor.  Combined they provide everything necessary to calculate an engine load parameter that is proportional to the MASS FLOW RATE through the device.

SA

[chevyeater]

Thanks for the reply.    I just thought it was a bit confusing since the Mass Air Flow is calculated.

My Supra came with a KV with the barometer internal to the ecu. I can't mount that KV sensor in a blow thru setup because it does not account for density of the compressed air. It is possible to mount a real (hotwire) MAF like that though with consideration for straight airflow thru it. Turbos love to blow, the aren't too good at sucking though.  

I'm still confused about what the EMS does with a MAP sensor. It is not bieng used to calculate throttle flow like an OEM application, correct?    What effect would activating the internal barometer have on a MAP converted EMS?

[andris]

It is possible to mount a real (hotwire) MAF like that though with consideration for straight airflow thru it. Turbos love to blow, the aren't too good at sucking though.  

Possible... But the turbulent airflow might not make it last a long time (battering the hotwire).  It should theoretically give correct readings in that setup, but might not be as reliable as a draw-through setup.  also, the aforementioned turbulence may cause some erratic readings, as they prefer clean airflow.  

In regards to those poo-poo-ing MAF sensors; each has its place, but in the end, a speed density system is measuring several factors and making calculations and compensations based on pressure(manifold and sometimes barometric), temperature, throttle position, etc. to arrive at something that represents the amount of oxygen entering the motor (so it can inject the right amount of fuel) .  A mass airflow sensor is as close as you can get to actually measuring the amount of oxygen entering the motor.  Mass is independent of humidity, temperature, elevation, pressure, volume, velocity, density...

I lack direct experience with other makes, but in Nissan cars using hotwire sensors, fuel calculations are based entirely on MAF signal when under load.  With adequate sensor range and fuel mapping, you can make drastic changes to turbo size, boost level, cams, headwork, etc. with zero effect on tuning or AFR.  

andris

[BLKMGK]

Ummm, NO. MAP sensed cars use a MAP sensor and an IAT sensor to figure out load. MAF sensed vehicles use the MAF, often times IAT (at the MAF sensor not intake), AND a Baro sensor. The mappings use a MAP sensor for load input don't care about TPS except to do accel fueling (just like MAF) and for idle things etc.. MAP isn't nearly as complicated as you think.

Each does have it's place, I'll agree. MAF is particularly good when you cannot access the internal tables to tune - MAF will compensate FAR better than MAP for changes in effeciency of a motor. Ask any FD3 owner I wouldn't mind trying a MAF sensor on my car but it owuld have to be one that I couldn't max out, could read LOW speed airflow well, and was big enough not to create a restriction...

[chevyeater]

Neither of my MAF Tuned Port Camaros (an '86 and an '88 ) had a baro sensor anywhere on the car.

[WadZii]

come on now... ur talkin about a 86 camaro... did they even have computers way back then    lol

[BLKMGK]

Neither of my MAF Tuned Port Camaros (an '86 and an '88 ) had a baro sensor anywhere on the car.

You sure it wasn't internal to the ECU itself or perhaps part of the MAF sensor itself? In a MAF setup you must trim for Baro to do it right otherwise driving to the top of a mountain would cause you to run pig rich. Closed Loop might compensate at part throttle but once in Open Loop it would be a mess!

[Mello]

Must agree with BLKMGK with the baro thing.  Flow systems need to have a baro sensor somewhere or the system will not be able to properly do it's job.