94formulabird

I have the stock MAF on my car, and someone told me that it would be maxed out and start to make the car lean under high boost. Is this true. I have a friend with a granettelli MAF hell sell me pretty cheap. Would I want to do this before a tune, so they can tune for it. Sorry for all the questions latly

qqwqeqwrqwqtq

-IF- you are going to run a MAF sensor, run the stock one.

Bryan Wilkinson

iTrader: (1)

What happens is that with the MAF maxed out the computer can no longer compensate with fuel, so you have a couple of options. The fella that posted above me, option 1. Do not make any changes to the stock maf, it is calibrated and changing it will not do anything but make matters worse.

If you have EFILive, or access to a tech 2 you can monitor the Freq under WOT and see how far you are going, If you are only doing something like 8-12 psi. You can manually add what fuel you need in the VE table.

If you are over that, you really should consider the 2 Bar or 3 Bar setup from HPTuners. Believe it or not, drivablity improves with this setup. Significantly.

Option 3, is a Pro-M Maf setup. They can recalibrate their MAF to read up to 1200hertz as opposed to 5??. Then you can readjust your MAF table. They will give you the step conversion to change in your MAF table.

Hope that helps.

99SS-T

iTrader: (5)

So how much of an investment is it to get a 3 bar setup? Would I have to get a new ECU and all that other stuff taht costs big bucks? Or is it a minor change in the stock ECU to make the 3 bar map sensor work?


John

ddnspider

iTrader: (26)

is a 2 bar setup like speed density, no maf aat all?

Wicked_Hugger99

iTrader: (1)

i dont guess so cuz im running a 3bar SD tune and i dont see a maf anywhere under the hood. Jim?????
99SS-T, i run a 3bar SD tune w/ stock pcm using HP Tuners i believe

Bryan Wilkinson

iTrader: (1)

The cost of HP Tuners, the 2 or 3 bar setup and the map sensor. You remove the MAF, and your off and running. This is what they call a speed density tune. Drivability is much better.

HP tuners has rewritten the Operating System to allow you to adjust throughout the entire 2 and 3 bar range. if you are not going to be in the 3 bar area with your boost, dont get a 3 bar.

Bryan Wilkinson

iTrader: (1)

That is correct. All of the GM cars were like that in the 80's.

ddnspider

iTrader: (26)

and the advantage of speed density is....?sorry just havent read much about it.

99SS-T

iTrader: (5)

Ya im confused about that as well. How do you know exactly how much air is gettin into the engine with out a MAF? I kno wya put a MAP sensor in tehre but that doesnt tell teh engine how much air is goin in right? Like wouldnt ya be runnin rich on a hot day and lean on a cold day cause ya got hte same amt of boost BUT alot mroe air on a cold day? Hope ya can help me understand!
Also how sells the 3 bar setups? Thanks


John

Pro Stock John

iTrader: (34)

Map sensor:

Definition: Refers to a manifold absolute pressure sensor, a variable resistor used to monitor the difference in pressure between the intake manifold at outside atmosphere.

(MAP) A sensor which monitors the engine's intake manifold pressure and transmits the data to the engine controller. A pressure-sensitive disk capacitor used to measure air pressure inside the intake manifold. The Map sensor sends a signal to the computer which uses this information to determine load conditions so it can adjust spark timing and fuel mixture. Also called manifold pressure sensor or pressure differential sensor

Pro Stock John

iTrader: (34)

Manifold Absolute Pressure (MAP)
The Manifold Absolute Pressure sensor measures changes in the intake manifold pressure resulting from engine load and speed changes. The computer sends a 5-volt reference signal to the MAP sensor. As pressure changes in the intake manifold occur, the electrical resistance of the MAP sensor also changes. By monitoring the sensor output voltage, the computer can determine the manifold absolute pressure. The higher the MAP voltage output, the lower the engine vacuum, which requires more fuel. The lower the MAP voltage output, the higher the engine vacuum, which requires less fuel. Under certain conditions, the MAP sensor is also used to measure barometric pressure. This allows the computer to automatically adjust for different altitudes. The computer uses the MAP sensor to control fuel delivery and ignition timing.

99SS-T

iTrader: (5)

So where cna i get a map sensor setup for hte car?


John

Bryan Wilkinson

iTrader: (1)

Actually it does a better job of measuring the air than the MAF. Pressure is pressure. If you are at 1000ft above on or below sea level, air pressure is air pressure. There is a bladder in the MAP sensor and when it moves based on air pressure, it sends a voltage signal to the computer from 1 volt to 5 volts.

Now here inlies the problem with old school and how it was fixed with new school. Old school, had 1 2 and 3 bar setups. All 3 read on 5 volts. 1 is for 1 atmosphere, 2 for 2 and so on. However, the scale gets smaller and smaller the more you are trying to read because it is still 5 volts. Enter new school. HP tuners rewrote the software so that the computer could better examine 2 and 3 bar in the same 5 volt range. Thus better drivablity. The MAP sensor is also only limited to is Barometric calibrations. 1 atmosphere, 2 atmospheres and so on. There is acutally a 4 and 5 bar that you can use with a FAST or Big Stuff engine management system.

The MAF is not as accurate as the MAP sensor. In my opinion. When I switched to the MAP 2 bar tuning package with the stock computer, drivability improved 10 times.

ddnspider

iTrader: (26)

got a link for that by any chance...the package

Lostpatrolman

iTrader: (3)

http://hptuners.com/order.php

I guess the 3 bar setup isnt out yet?

Trvln Nalzmn

You can if you are also measuring RPM at the same time. The swept volume of the motor is constant so to find out how much air is getting into it at a particular point in time you just need to know the speed and how dense the air is, which the MAP sensor can tell you.

turbolx

Are you aware the whole core of the fuel calculations being performed inside the PCM is a ratio of air mass to fuel mass ? Input from the MAF sensor gives the PCM a direct measurement of air mass from which to work, making for very robust fuel and load calculations. Speed density systems must back calculate from pressure, temperature and a speed reference table (VE map) to come up with an air mass value. It can be plenty accurate, it just takes a couple more steps to get to what the PCM really needs to know, air mass.

The point where most "tuners" have issues is that the signal from the MAF no longer represents reality. Modifying the MAF ends, changing the plumbing into the meter, or changing the meter altogether REQUIRES remapping of actual MAF performance before any other airflow (load) based functions can be accurately performed. Many people miss out on this step. The VE table should still be modified as needed, since the PCM uses this for transient calculations at lower engine speeds, even with the MAF attached.

The irony is that when going "MAFless" many of these same people take the time to carefully build the VE map to represent the new physical reality of the system and declare it to be "superior" to the uncalibrated MAF based system they replaced.

The proper solution for MAF based systems is to employ a meter with adequate range AND a proper calibration in the PCM to reflect the actual mass flow with respect to output of the new sensor as installed in the system. If this is done, there's no reason the car can't have excellent drivability.

No flames intended here, just shedding some light on how the PCM really works.

FastKat

iTrader: (10)

This is all well and good, but I remember searching the posts and found that the engine stock ECU can only read a certain level of airflow from the MAF... and that's it. After that, you were on your own as far as tuning is concerned... even getting a wider-ranged MAF wouldn't help because the engine could only read SO MUCH air and that's it... I believe the limit was around 1,000CFM. Does the MAP sensor beat this shortcoming of the stock ECU?

turbolx

Yes, and there's ways to work around this if you're creative. It's called "load scaling". Basically, you reduced the actual MAF output by the percentage the new MAF would be over the PCM max. To keep fueling accurate, injector size is scaled down by the same percentage. To keep load calculations accurate, engine displacement scalar is also scaled down by the same percentage. The nice part about this is that when done correctly, the tuning process remains the same. I.E.. a 5% commanded fuel change yields a 5% actual fuel change from the engine.

This keeps the acutal performance right on for all load based calculations (including spark, EGR, idle, et. al.) while allowing for significantly higher measured range. The primary downside is a slight loss of resolution at low flow rates, but since MAFs have an exponential transfer function there is a lot of resolution to give down low before experiencing any trouble.

This method works so well that Ford did the exact same thing on the production calibration for the GT supercar and still passed CARB emissions and all their internal performance standards.