Tricking Std Maf Power Fc To Use Map Sensor

[h2k]

I know it's off topic but are you running a GT4088R on an RB25DET with that engines head/inlet system/valve train ?

A .

Im running with oversized wiseco pistons and eagle rods. the head is heavily ported and polished but with stock valve train except tomei cams. I am however considering upgrading the head to solid lifters, 272 cams and stronger springs etc.

[h2k]

You've answered your own problem in a way.

Put e decent plumb-back BOV setup on (GTR is fine), and move the AFM further away, even before the throttle body end if you must.

Will fix all your issues for a couple hundred $$

I have allready tried this, used the HKS SSQV with resirc kit. Improved slightly, but didnt quite do it...

stop suggestion MAF alterations, the point is converting to MAP. darnit =)

[h2k]

The beauy of speed density systems on factory ecu's is that their model for charge temp (the actual air temp of the air in the engine) is mapped over g/s of airflow (which without a map sensor is based on rpm and MAP itself).

If I was you I would rescale the maf down to a suitable size to get good airflow figures from it. I would also place a intake air temp sensor into the manifold. I would then get a micro with at least four ADC. Three input chanels for MAF, MAP and IAT and one ouput for a psuedo MAF votlage for the PFC. YOu then will need to be able to map/tune the intake air temp sensor over MAF voltage as a multiplier of AIRtemp to give you a final Charge temp.

ie

MAF Voltage Air Temp Multiplier

0 2

0.5 2

1 1.9

1.5 1.7

2 1.5

2.5 1.3

3 1.1

3.5 1

4 1

4.5 1

5 1

The actual charge temp of the air in the engine is the "Air temp multiplier" times the current IAT sensor reading. The above mulitplier curve will need to be tuned based on the position of the IAT sensor. You will also need a multiplier of RPM as well to take into consideration the difference in voltage of a linear MAP sensor vs an expotential MAF sensor. I would then apply the ideal gas law and see what happens.

My advice is that unless you have a good understanding of microprocessor design and implimentation and a good tuning back groudround then DO NOT DO IT!!

Actually I go to a engineering school that also educates in microprocessor design tough it's not what I study(Machineengineering). But I do know a couple of buddys that do that course. I was also thinking of the MegaSquirt ecu system wich is a opensource system. All Megasquirts can run MAP system på default and they should have knowledge of how ideal gaslaw is applied and the correct scalars and mathematical operations needed based on pressure, temperature and tps signal I'll try that forum, and if I get good answers I'll get somebody at school to solder me a PCB with a microprocessor that does what I want.

Another idea is to actually use a megasquirt ecu, wich has map sensor and everything it needs, included output lines. All I'll need is a new firmware for it. And then use the megasquirth purely as a converter from map to maf, it's so cheap it will be well worth it.

Edited September 27, 2008 by h2k

[h2k]

Or you could take 5 minutes looking at the all 3 wires to change in the wiring diagrams and do it yourself, nothing inside needs to be changed. MSD timing window for $80 will run the vct at any rpm point your heart desires at a touch of a button.

H2K, you still have that link of the system i showed you that can convert the signals? cant for the life of me remember its name? Bit pricey but looked very good

"MAF Translator Pro" is the system you showed me don't remember the url but a google will find it

[Adriano]

Have you considered anything other than a PFC?

[Mr Jollwah]

both.

I allready put the Q45 internals into a 4" pipe and remapped. Problem is with such a large MAF im having trouble with idling and driving in the city. It's to rough and the signal also fluctuates because of fanblade turbulense. I have a rather large Garrett GT4088R turbo with 4" inlet and not to much space for inlet piping. Also using a atmospheric dump valve, im having a very hard time driving around without stalling the engine. But high speed driving it's no problem with a large maf. Dragracing and trackdays go very well.

But still, this is a topic I am very interested in.

pV = mRT

I've talked to a company(SplitSec) that makes alot of MAF and piggyback fuel products and I qoute them:

"Deriving MAF from pressure is very difficult. The VPC never worked well

which is why HKS obsoleted it. If you want to go map based, which you

should anyway with a big turbo, you need an ECU that can work directly off

of a map sensor"

I agree it might be difficult, but when a d-jethro can do it, im sure another unit also can and convert the output to 0-5v.

Aren't there different MAF sensors with greater resolution that you could try in your 4" pipe.

I mean the ford tuners are spoilt for chioce with SCT and PMAS sensors, If a lightning sensor can be adapted to work then these should be able to be as well.

[h2k]

I pulled this copy paste from a MegaSquirt site. Wich does lead me a bit closer to making a MAP to MAF signal converter

The Ideal Gas Law

You might remember from high school physics classes that an ideal gas (which air is reasonably close to) obeys the relationship:

PV = nRT

Where:

P = pressure,

V = volume,

n = number of moles (which is related to the mass of the gas, i.e. 1 mol = 6.023x1023 molecules of the gas, and n = mass (in grams)/molar mass(MM)),

R = the ideal gas constant,

and T = the absolute temperature.

What does this have to do with fuel injection? In order to know how much fuel to inject, we need to know how much air is going into the engine so the chemically correct mixture (called “stoichiometric”) can be achieved. So for a fuel injected engine, we use sensors to determine the pressure in the intake manifold and the air temperature. However, the temperature in this equation is “absolute temperature” measured in Kelvins which is equal to degrees Celsius + 273º.

The volumetric efficiency (VE) is a percentage that tells us the pressure inside the cylinder versus the pressure in the manifold. We know the volume (V) from the displacement of the engine. Thus we can calculate the mass of air (M) in the cylinder (proportional to n) from

n = PV/RT

=> M = n x MM = PV/RT x MM

= (VE * MAP * CYL_DISP) / (R * (IAT-32) * 5/9 + 273)) x MMair

Since:

P = VE * MAP (i.e. the pressure in the cylinder in kPa),

V = CYL_DISP = the displacement of one cylinder (in liters),

R = 8.3143510 J/mol K,

and T = (IAT-32)* 5/9 + 273 to convert IAT from ºFahrenheit to Kelvin.

Note that we can combine the constants R and MMair into one, and we will ignore them from this point on since they can be hard-coded into the assembly language code and neglected after that.

[Strik3r]

http://www.haltech.com.au/

im not trying to be a smartass.. but your trying to do something that at best is going to be a dodgy work around.. and your going to spend a few hundred dollars doing it. You can get $1400-1500 for that PFC of yours.. Sell it, buy a haltech and run a 3 bar map sensor. You wont look back.

[MAXIEL]

QUAL VALOR SERIA JUSTO POR UM PRODUTO QUE ATENDESSE ESSA NECESSIDADE DE MAPEAR UMA ECU  ATRAVEZ DE UM GERADOR DE SINAL CONFIGURAVEL SUBSTITUTO AO MAF?

ESTOU DESENVOLVENDO UM PRODUTO QUE PERMITE  USAR QUALQUER TAMANHO DE INJETORES E COM QUALQUER PRESSAO DE TURBO EM QUALQUER INJECAO ELETRONICA.

"O IMPOSSIVEL SOMENTE É IMPOSSIVEL ATÉ ALGUEM DUVIDAR E PROVAR O CONTRÁRIO"!

 

[GTSBoy]

5 hours ago, MAXIEL said:

QUAL VALOR SERIA JUSTO POR UM PRODUTO QUE ATENDESSE ESSA NECESSIDADE DE MAPEAR UMA ECU  ATRAVEZ DE UM GERADOR DE SINAL CONFIGURAVEL SUBSTITUTO AO MAF?

ESTOU DESENVOLVENDO UM PRODUTO QUE PERMITE  USAR QUALQUER TAMANHO DE INJETORES E COM QUALQUER PRESSAO DE TURBO EM QUALQUER INJECAO ELETRONICA.

"O IMPOSSIVEL SOMENTE É IMPOSSIVEL ATÉ ALGUEM DUVIDAR E PROVAR O CONTRÁRIO"!

 

If you're asking what would I pay for a product that does what the OP was asking for......then the answer is ZERO DOLLARS.  The return question when asked "how do I do this", or as you're asking, "what is it worth?" is "Why f**k about when it isn't necessary?".

As has been said above, there is no future in stuffing about with trying to make MAF ECUs read MAP sensors when you can just go buy an aftermarket ECU that uses a MAP sensor and be done with it.