how does the ecu determine the load on the engine?
 

I understant that in newer models, subaru installs a vaccum sensor to determine the load on the motor so the ECU can control more effectivelly the ignition time, but our SVX does not have a vaccum sensor... does it?

Re: how does the ecu determine the load on the engine?
 

No. It uses the Mass air flow sensor to meter the amount of air the engine takes in.

Re: how does the ecu determine the load on the engine?
 

Combination of throttle position sensor, RPM, MAF, probably the O2's as well... A lot of factors show how hard the engine is working.

Re: how does the ecu determine the load on the engine?
 

I am not too sure that is right. The latter ECU use the atmos sensor to change the gearbox maps, but I think it still uses the other inputs of throttle position sensor, RPM, MAF to determine the load.
The later phase 11 autos have another speed sensor on the turbine shaft to determine the difference in speed between the impeller and the turbine that gives a direct read of load.

Harvey.

Re: how does the ecu determine the load on the engine?
 

Load is determined using the mass airflow rather than manifold absolute pressure sensors like newer ssubies do

Tom

Re: how does the ecu determine the load on the engine?
 

Just saying : how on earth back in the day ( pre 1970 ) did we ever operate an automobile motor by just the use of a heat sensitive spring operating a small plate in the throat of the carb. ( automatic choke ) boy we have come a long way baby:lol:

Re: how does the ecu determine the load on the engine?
 

Engine Load is usually measured as grams of air per revolution (g/rev). Some manufacturers do per cylinder instead.

The most basic equation is divide Mass Airflow (grams per second) by Engine Speed (revolutions per second ie. RPM divided by 60).

Re: how does the ecu determine the load on the engine?
 

Isn´t it easier to have the readings of an intake manifold pressure to know the engine load and adjust it with the readings from the RPM, MAF and TPS?
what does longassname think about it? (I send you a PM some days ago)
How does the new 1av1 calculate the engine load so it can tune the timing advance? would you recomend the use of a vaccum transmitter/sensor working together wit a new chip program?

Re: how does the ecu determine the load on the engine?
 

What exactly is your goal here?

The ECUtune software acts the same as the stock ECU, just more aggressively.

Re: how does the ecu determine the load on the engine?
 

Actually it was a bit more involved than that :D

Keith:cool:

Re: how does the ecu determine the load on the engine?
 

The ECU needs to know the quantity of air it is getting, so it can work out the quantity of fuel to mix with it.

A MAF sensor measures it directly.

With a MAP based system you need to measure pressure and temperature and then calculate the quantity based on those readings. When you step on the gas, Mass Airflow changes almost instantly but Manifold Pressure lags behind. So you have to do TPS delta compensations to guess how the airflow is changing while you wait for the pressure to catch up.

MAF systems are faster to respond and more accurate. So they run smoother, especially at low rpm where precision is important. They suffer from less hesitation and provide better drivability. That's why most modern ECUs use MAF.

MAP tuning becomes a lot more useful when you increase the horsepower beyond what the manufacturer designed for. When your airflow exceeds what the MAF can measure, you either have to fit a bigger MAF (with reduced precision), or go to a MAP based system.

Some aftermarket systems like EcuTek RaceROM and Cobb Accessport can use MAF at low rpm and switch to MAP when the MAF gets maxed out. But obviously neither of those is available for the SVX.

Re: how does the ecu determine the load on the engine?
 

I've got a MY11 Forester S which runs the same engine / turbo as the MY11 Impreza... running MAF still. The only MAP based Subaru's I know of from factory are some of the MY02 Outbacks (H4 and H6).

MAP sensor is only used for boost cut and barametric compensations. However sometimes you can flash the rom to a Group N version which runs on MAP - google romraider for more.

Well said.

Re: how does the ecu determine the load on the engine?
 

Yes the Mass Air Flow sensor is far more accurate than the Manifold Absolute Pressure sensor, that was used before emissions demanded better fuel ratios. Though I think you have their actions, in reverse.:cool:

The MAP Sensor will signal the pressure change instantly, the MAF is slower as the air has mass, and pressure does not. When you floor the pedal, the pressure changes instantly, along with the fuel, but the air is not there to match it, so the ratio has to be compensated.
The MAF sensor reads the air mass that is entering the cylinder, so the air/fuel ratio can be set exactly to match the air.

Harvey.

Re: how does the ecu determine the load on the engine?
 

my goal, as always, is try to understand the control a little more. Our SVX have only a MAF, not a MAP.
The ignition timing on the original ECU fails in properlly advance the ignition, so we can feel the advance increase as we rise the RPM's in a 0 to 100 aceleration. It is too delayed. New softwares have inproved the preformance by advancing the ignition map, but what are the signal it takes and what is the weight of each of those to change the ignition map. I've read that the new 1av1 does not need to learn (the ignition timing advance) because it change the map everytime you drive the car but again, what factors makes the map be changed and in what proportion?
I'm planning to build my own HHO generator and install it on my SVX using GLP injectors @ 8-15psi. I'm working on the desing of all the components and in the software I'll use on the new micro PLC. This is going to be a seccondary ECU to control the HHO system. I'm willing to include a load injection increase feature (like the gasoline jet on the carburators). If I succes, I'll share this on this net.

Re: how does the ecu determine the load on the engine?
 

I disagree, the air flow is a consequence of the vaccum generated, so the vaccum appears first. new sensors can meassure this vaccum faster than the increase of air flow on the MAF.
in the old times, the carburetor had a barb connector for a hose thar lead the the distributor to act on a diafragm to increase the ignition timing advance. This was the "LOAD" factor on the advance. The RPM factor was done with counterweights on the rotor.
We do not have distributors now. It's all on the chip. but I do not feel any increase of the ignition advance due to "load" on my SVX. May be the only way to confirm it, is with a camera and a timing gun, some tape and run the car....