why? if you get X air, you need Y fuel to get the desired AFR. The amount of air flow on different turbos varies even if they boost to the same PSI.

 

The OE PCM uses a combination of MAF, BARO, IAT, ECT and APP/TDC to come up with a numerical value that represents the load on the engine at any given moment.

Read the first post of the thread.

 

I see what your saying but its not an accurate way of doing it.

 

Why do you think its not an accurate way of doing it?

 

Yes it is, the EVO and STi are MAF only from factory. Why use a MAP sensor to estimate the mass airflow when you can measure it directly from the mass airflow sensor?

 

Correct. Air mass/fuel mass calculations are the most accurate.

I am not trying to argue, but that is not true. Almost all OEM turbo vehicles meter fueling and ignition calculations through a MAF sensor; Subaru WRX, Mitsubishi EVO, Skyline GTR R32, R33, R34, & R35, Audi, Porsche, Mazdaspeed3, etc.

MAF calculations are the most accurate means of metering fuel and ignition calculations. A T28 will flow drastically less air mass than a GT35R at 10psi. Metering with a MAP sensor would not be the most accurate way to develop calibrations for the engine through an ECM. Calculating load by employing a MAF sensor would and is the most accurate means for now. This allows VE changes to be measured, rather than estimated by using a MAP based system.

Take care,
Christian.

 

I should have reworded it. Its not the most accurate way when dealing with a turbo car at least the ones I have tuned. Supras, RX-7's, EVO's etc.. all prefer a MAP setup over a MAF, but that is with a true standalone.

Im relating this more to a standalone than a piggy back or flash. It was my bad as I forgot the Accessport is not a standalone, so I was wondering how it was reading pressure.

 

Well, the MAF estimates the exact amount of air based on readings from it recieves from itself, and the barometric sensor. It uses the trim to make exact corrections to this number.

Cars like the evo, wrx, and others use both a MAF and a MAP sensor.

N/A cars like the rx8 use the MAF and the BARO sensor.

Needless to say, you need an ambient pressure reading to accurately calculate the mass of air

 

On a turbo application like this, you factor in the estimated efficiency of your turbo and intercooler into the tune. and Hope the ECU trims itself to weather changes.

 

Even the interceptor X gets readings from the stock MAF to determine temperature to correct itself to some extent.

 

MAF sensor isn't a magical device that can accurately measure exact percent oxygen in the air. Its a heated wire that is cooled in accordance with the amount of air blowing by it. As it's cooled its resistance changes.

Well, that air blowing by it could be at sea level or at 20 psi. There's no way for it to know.

 

MazdaManiac can i get a tracking number???

 

Yes, a MAF based system is most accurate. The preference is most likely due to the tuner who does not quite understand how the MAF system works. A MAP system is a more simplified and easier to understand IMO. My guess is that you may not be as familiar with internal ECU calculations. Nothing negative, but once you fully understand MAF based tuning...you will never want to go back to speed density. Below are some additional details which may be helpful. Again, I am not trying to argue, just openly debate. A main point that I am trying to get across is that one does not need a MAP sensor to be able to tune a turbo engine. That is a complete farce.
Actually, the MAF system is the most accurate load metering device available to man today, thus why almost all vehicles employ one. Long story short, your explanation is not quite how it works. The sensor actually measures MOLES of air. A mole of air touches the heated element and a heat exchange occurs. Taking into account Ohm's Law and Impedance: Voltage (V) = Current (A) X Impedance (R). The amperage is fixed, so when the resistance increases through a decrease in temperature (as a mole touches the heated element and transfers heat), the voltage increases. Long story short, as the motor continues to breath air, it will increase MAF voltage. When MAF voltage goes constant, you can tell the engine is no longer breathing (HP will flatten or decrease on a chassis dyno). Fun stuff!
This is again absolutely not true. A MAF based system measures the MASS of air entering through an engineered and calibrated MAF housing. If one operates an engine at higher elevation, where less moles of air are available per volume of air, the engine measure this. The only thing one would have to calculate for is a change in fuel mass (running race gas vs. pump gas of X quality). You do not have to estimate anything, more mass of air is measured, then more mass of fuel is added and less ignition advance is needed. I hope this geek out is perceived the correct way, I am just trying to clarify something that needs clarification. The system is very simple actually.
Well, a USDM EVO and the RX-8 do not have a MAP sensor. They have no means of measuring manifold pressure. This measurement is not necessary to calculate fuel and ignition calculations. The MAF sensor is used for this, and compensatory calculations are made using other sensor inputs. This will be fun, and I am posting this just to educate those that are not familiar with ECU load calculations. I am not posting to begin an argument. Using a baro to calculate mass is absolutely not necessary. A Subaru has a MAP sensor, but that is mainly used for controlling boost on the turbo. The EVO actually uses the MAF sensor to control boost.

I need to go out to Miller Motorsports Part to tune some race vehicles. I will be back later to appropriately respond. I want to make sure those reading this understand the different between the various metering systems (Alpha-N, MAP, MAF. Others metering systems exist, but we will limit it to these main three for this discussion) and why a MAF system is used due to is increased accuracy compared to the other systems. Please no one take offense to this posting, this is simply an open discussion.

Take care,
Christian.

 

lol, wait until they start telling you 87 octane fuel is better in an RX-8 too ...

 

its cool Christian- we go on this same path every 6months or so

 

Has anyone tried this one an NA AT Rx8? I am curious to see what the benefits are for AT's without FI.

 

It's coming from what I know. MM has told me soon. Might be next week. But I will let him give the for sure.

 

Just so you guys can see the effect of having an improper intake can do to your car when using the MAF:

http://youtube.com/watch?v=HFovWJhUBkA

That same setup is perfectly fine with the int-x (MAP), but the filter is next to the MAF, no screens. The car basically runs like crap. When I had this same intake on my car and stock PCM, it reacted the same way, so this has nothing to do with the AccessPort, but more of a warning on what to expect if your airflow isn't smooth across the MAF. There should be varying degrees of problems, mines drastic since it's really turbulent.

Jeff is hooking me up with a better CAI shortly.

 

I got the Mazsport CAI for my car recently.

Would my Cobb AP work well with that intake in your opinion?

 

did you ask scott to make the maf area 3.5"? if not, you'll need to make sure jeff scales your maps properly to work with the 3" maf housing.

I can't tell you how well that cai will work since I've never used it. But it's design is similar to how many are doing it, so I would guess it's OK

 

Received, thanks Jeff!

Once I get the maps, I will gladly report to fellow Canadians whether it will work on our cars!

 

grouch, the ap is preloaded with the cobb maps, so you can actually try those out right now before you get the maps from jeff.

 

I asked Scott to make it out of aluminium and I just sent him a PM to make sure the intake tube is 3.5". He is supposed to ship me one next week.

 

WOOOOOOOOOOOOOOOOOT!!!!

 

So if I have the stock Greddy MAF intake tubing and I buy the AP from MM I need to ask him for the better CAI to make it work properly?