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Stock Maf Limits

Exactly. Tuning with a blow-through MAF configuration is sort of a middle-ground between MAP tuning and MAF tuning. With a pull-through MAF configuration, we would get the results we want

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Old 08-20-2014, 02:43 PM   #31 (permalink)
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Exactly. Tuning with a blow-through MAF configuration is sort of a middle-ground between MAP tuning and MAF tuning. With a pull-through MAF configuration, we would get the results we want to expect of a MAF sensor, but unfortunately we would top-out the MAF sensors extremely early. With our blow-through MAFs, our ECU will detect additional airflow, it just will not detect it accurately. But its not exactly that important, since we are recalibrating the maps based on the end results... sort of a "manual closed feedback" during tuning.

One interesting flaw in pull-through MAF configuration in boosted applications is the lack of an additional air temp sensor in the plenum. The compressor and intercooler will have such dramatic effects on air temps that having the only air temp measure taken after the air filter is not dependable at all. I wonder if R35 GT-R has an additional air temp sensor... I dont remember seeing one. I will have to try and look that up.
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Old 08-20-2014, 03:08 PM   #32 (permalink)
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Charles, there is air temperature measurement circuits in each of our MAFs. To the best of my knowledge that is required to work along side of the airflow to determine its rates.

For example an uncalibrated MAF with no temperature sensor would read a very different airflow at -20 than at 80 degrees since all were doing is measuring the rate at which the flowing air cools a resistor in the MAF circuit.
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Old 08-20-2014, 03:09 PM   #33 (permalink)
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Old 08-20-2014, 03:14 PM   #34 (permalink)
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I am very aware of the air temp sensor in the MAF! You are correct, it is required for the MAF to properly function.

What I am talking about is how the MAF sensor in a pull-through configuration such as the R35 GT-R will not be aware of changes in air temp caused by the compressor and intercoolers. Therefore the ECU will not make air temp corrections (for fuel injection) based on air in the correct location.

To accurately apply air temp corrections for the fuel tables would require a secondary air temp sensor in or around the plenum, after the intercooler and compressors.
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Old 08-20-2014, 03:39 PM   #35 (permalink)
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I am very aware of the air temp sensor in the MAF! You are correct, it is required for the MAF to properly function.

What I am talking about is how the MAF sensor in a pull-through configuration such as the R35 GT-R will not be aware of changes in air temp caused by the compressor and intercoolers. Therefore the ECU will not make air temp corrections (for fuel injection) based on air in the correct location.

To accurately apply air temp corrections for the fuel tables would require a secondary air temp sensor in or around the plenum, after the intercooler and compressors.
Sorry I misunderstood you...

Id have to see the tables in the computer to see how it runs. But if I am going to take a guess I am going to say that they utilize the MAF for idle and low boost conditions, then switch to a speed density type calculation when the MAP reaches some threshold.

Also regardless the MAF measures a flow rate, all the system has to know is that amount of air is in the system and will be ingested. It doesnt matter if it heats up or cools down from there as all that would do is slow down or speed up the incoming air, which works fine on a recirc type setup. With an open dump setup this would all fall apart as now your going to have metered air leaving the intake tract. However on a recirc setup I think your error would be minimal and under WOT id expect the system to use the MAP anyways.
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Old 08-20-2014, 03:59 PM   #36 (permalink)
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Ah ya youre right, "brain-fart", changing the temperature of the air after the MAF doesnt change its volume it just changes its density.
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Old 08-20-2014, 05:33 PM   #37 (permalink)
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Ah ya youre right, "brain-fart", changing the temperature of the air after the MAF doesnt change its volume it just changes its density.
The change in temperature is going to cause both a change in volume and density the MASS will remain the same as read by the MAF, unless the pressure changes in which case density and volume could remain unchanged with the increase in pressure.

Mitco, while a plenum IAT sensor isn't very important as far as calculating fuel demand and air mass goes if you have the one in the MAF, timing and temp corrections for burn speed and injection angle are going to be effected greatly if there is an unmetered increase in air charge temperature.
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Old 08-20-2014, 05:44 PM   #38 (permalink)
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The change in temperature is going to cause both a change in volume and density the MASS will remain the same as read by the MAF, unless the pressure changes in which case density and volume could remain unchanged with the increase in pressure.
ya ya ya, catch me on semantics. MASS is exactly what I was talking about.
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Old 08-20-2014, 05:45 PM   #39 (permalink)
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timing and temp corrections for burn speed and injection angle are going to be effected greatly if there is an unmetered increase in air charge temperature.
there ya go. good point back to my original thought, i wasnt even considering the side effects at this depth yet.
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Old 08-20-2014, 05:46 PM   #40 (permalink)
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Mitco, while a plenum IAT sensor isn't very important as far as calculating fuel demand and air mass goes if you have the one in the MAF, timing and temp corrections for burn speed and injection angle are going to be effected greatly if there is an unmetered increase in air charge temperature.
While I agree with you on basis I would argue that real world adjustments to the fact would cause very little if at all 0 changes to the overall output of the engine since we are not dealing with direct injection engines. That argument would be valid if we were talking about emission generation and controlling the hydrocarbons. But usually when one is concerned about that it is during a constant state operation such as idling or cruising down the interstate.

On a direct injected engine that does not rely on the fuel evaporating (and thus cooling the charge before it hits the engine) I would say that yes it becomes a greater concern, in fact all the diesels I tune have a IAT right before the air hits the plenum for that exact reason. The IATs have a large effect on the burn rates in direct injected engines because you do not have the cooling evaporation effect before the air enters the combustion chamber.

Again its just my opinion on the matter. Plus if you look at the Uprev timing tables there is only so much fine adjustment available to the end tuner. Its a limitation to the memory in the ECU.
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Old 08-20-2014, 05:48 PM   #41 (permalink)
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MUHAHAHAHA you're welcome I consider it a part time job to make sure people don't use the wrong word.
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Old 08-20-2014, 05:53 PM   #42 (permalink)
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Originally Posted by Mitco39 View Post
While I agree with you on basis I would argue that real world adjustments to the fact would cause very little if at all 0 changes to the overall output of the engine since we are not dealing with direct injection engines. That argument would be valid if we were talking about emission generation and controlling the hydrocarbons. But usually when one is concerned about that it is during a constant state operation such as idling or cruising down the interstate.

On a direct injected engine that does not rely on the fuel evaporating (and thus cooling the charge before it hits the engine) I would say that yes it becomes a greater concern, in fact all the diesels I tune have a IAT right before the air hits the plenum for that exact reason. The IATs have a huge effect on the burn rates in direct injected engines.

Again its just my opinion on the matter. Plus if you look at the Uprev timing tables there is only so much fine adjustment available to the end tuner. Its a limitation to the memory in the ECU.
I'm sorry but IAT's play a HUGE role in detonation threshold so what you are basically doing is pumping a whole hell of a lot of air that can be 50-150 degrees above ambient/what the MAF is telling the ecu it is and expecting it's effect on ignition timing to be negligible? That is why the stillen kits clack away like a tap dancing festival once they are heat soaked and the ecu starts pulling gobs of timing as the knock sensor pick it up.
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Old 08-20-2014, 06:05 PM   #43 (permalink)
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I'm sorry but IAT's play a HUGE role in detonation threshold so what you are basically doing is pumping a whole hell of a lot of air that can be 50-150 degrees above ambient/what the MAF is telling the ecu it is and expecting it's effect on ignition timing to be negligible? That is why the stillen kits clack away like a tap dancing festival once they are heat soaked and the ecu starts pulling gobs of timing as the knock sensor pick it up.

I didnt think of the supercharger situation with the "suck through" maf. I was thinking only of the Turbo setup with the Mafs in their stock locations. But your right if the Maf is upstream of the FI setup (turbo or supercharger). The fix to that problem is just to move the MAFs to right before the throttle bodies. Then you can deal with it in much the same way we do with the turbo kits.

So yes your right didn't think of that condition during my reply but its an easy fix that would make that kit much easier to tune.

I was thinking more along the lines of a 5-10F increase as the metered air enters the heat soaked plenum.
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Old 08-20-2014, 06:20 PM   #44 (permalink)
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Well with the stillen kit you would have to put the mafs after the in manifold cooler, which isnt possible hence the need for a secondary iat sensor

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Old 08-20-2014, 07:00 PM   #45 (permalink)
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What about using a gtr maf? There a $150.00
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