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Discussion Starter #1
Forgive me if this has been covered, I searched but didn't find anything that seemed to answer the question.

As I understand it the JDM's use the MAF system standard(forgive me if I've gotten them backwards, I've been studying biochem for like 12 hours straight), but apparently most JDM users swap over to a MAP system (usually when upgrading the fuel computer). Is this simply because all the available fuel computers run off the MAP system or is the MAP system actually better?

Thanks!
 

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The OEM JDM 2JZGTE uses a MAP system, the USDM uses the MAF. They both work very well up to the limits of their design ranges but if you start making more power with more air and fuel flow required above the range of the OEM device, you have to step up to something else and almost all (if not all) aftermarket fuel controllers are MAP based.
 

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The OEM JDM 2JZGTE uses a MAP system, the USDM uses the MAF. They both work very well up to the limits of their design ranges but if you start making more power with more air and fuel flow required above the range of the OEM device, you have to step up to something else and almost all (if not all) aftermarket fuel controllers are MAP based.
I was always wondering why? To my understanding MAF is the better and more modern system compared to MAP, as it does produce neraly to none backpressure in the intake mani. So why do most aftermarket ECUs work with MAP? Is it more simple to handle?
 

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I was always wondering why? To my understanding MAF is the better and more modern system compared to MAP, as it does produce neraly to none backpressure in the intake mani. So why do most aftermarket ECUs work with MAP? Is it more simple to handle?
you got it backwards...

MAP = manifold absolute pressure, which means your MAP sensor is taking a reading directly from the intake manifold itself, which is much closer to the combustion chambers than a silly MAF a few inches behind the intake is. not to mention that MAFs can sometimes measure the amount of air entering the engine inaccurately. perhaps someone with a little more knowledge than myself could elaborate on how MAFs can sometimes take false readings.
 

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Discussion Starter #8
you got it backwards...

MAP = manifold absolute pressure, which means your MAP sensor is taking a reading directly from the intake manifold itself, which is much closer to the combustion chambers than a silly MAF a few inches behind the intake is. not to mention that MAFs can sometimes measure the amount of air entering the engine inaccurately. perhaps someone with a little more knowledge than myself could elaborate on how MAFs can sometimes take false readings.


My brother had told me that the MAF systems are prone to getting oil on the sensor from oiled intakes, which apparently wreaks havoc on the readings. But past that he had nothing bad to say about it (he's worked extensively with both). (though he didn't say one was any better than the other).
 

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AFAIK MAF systems read more accurately than MAP cars so a lot of manufacturers are switching to MAF-based fuel metering systems in their ECU's.

MAP systems aren't as accurate (from an emissions point of view by the way) in metering fuel BUT ultimately I believe MAP-based systems have greater power potential simply because there is nothing blocking the intake path as compared to a MAF.

Performance-minded people will go with a MAP-based ECU, whereas the tree-hugger of a car enthusiast (is there even such a thing?)will probably stay with a MAF-based system. :)

Goodluck!
 

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MAP systems rely on pressure and calculations to give the ECU an idea of how much air is going into the engine. MAF actually measures the volume of air itself with no calculations. MAP is easier to tune for and can pose much less of a restriction in the intake tract but the MAF can be made to work with almost any diameter pipe with a signal fudger (www.autospeed.com has more on this) and a wideband and some common sense.

There are MAF's out there that can support alot more power than the stock USDM MAF does (which becomes a restriction at around 550rwhp?).

I'm personally looking into it more as a MAF based setup can also help with high duration cams affecting idle, etc.

EDIT: Just to clarify:

JDM 2JZ-GTE = MAP
USDM 2JZ-GTE = MAF
2JZ-GTE VVTi = MAF
 

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MAP systems rely on pressure and calculations to give the ECU an idea of how much air is going into the engine. MAF actually measures the volume of air itself with no calculations.
but most MAP systems nowadays make several calculations per second (b/c they are computers/piggyback ECU's/etc.), and any error in the reading is minimal/negligible...whereas MAF's can still grossly miscalculate the amount of air coming into the motor - specifically how, i don't recall. but for instance, suppose a MAF measures a specific amount of air coming through the intake, but then an appreciable amount of that air gets vented to atmosphere by a BOV just upstream of the intake manifold - then the true amount of air that makes it to the manifold and into the combustion chambers is less than whatever the MAF originally measured...the ECU will then add more fuel than is necessary b/c it got a false high reading via the MAF, causing you to run rich. now i'm not sure if this is the best example (or even an accurate example for that matter), but i do know that MAF's can be mislead in such ways.



EDIT: Just to clarify:

JDM 2JZ-GTE = MAP
USDM 2JZ-GTE = MAF
2JZ-GTE VVTi = MAF
are all 2JZ-GTE VVTi motors MAF-based, regardless of whether its a JDM or USDM motor?
 

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but most MAP systems nowadays make several calculations per second (b/c they are computers/piggyback ECU's/etc.), and any error in the reading is minimal/negligible...whereas MAF's can still grossly miscalculate the amount of air coming into the motor - specifically how, i don't recall. but for instance, suppose a MAF measures a specific amount of air coming through the intake, but then an appreciable amount of that air gets vented to atmosphere by a BOV just upstream of the intake manifold - then the true amount of air that makes it to the manifold and into the combustion chambers is less than whatever the MAF originally measured. now i'm not sure if this is the best example (or even an accurate example for that matter), but i do know that MAF's can be mislead in such ways.
I can see where you're coming from. I've got a MAF on my Aristo (2JZ-GTE VVTi) and it's fine with a vented to atmosphere BOV - just gives you a massive backfire/flame if decatted when you get off the throttle at high boost/high revs. For daily drivability though it's alot better than a MAP based car apparently and no matter the calculations it's still an "estimate" where a MAP based car is concerned. I may be wrong on that though. Think we need someone who's more "in tune" with both types.

The only downside I can say is if an IC pipe blows off at night you're stranded - you can't drive home like you can on a MAP based car. Something else to look into is why a MAF is not located more upstream (ie: near the throttle body)? and located near the airfilter/induction pipe?


are all 2JZ-GTE VVTi motors MAF-based, regardless of whether its a JDM or USDM motor?
There are no 2JZ-GTE VVTi motors as far as I know as they were all JDM. All the JDM 2JZ-GTE VVTi's are MAF-based though
 

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well there's the IS300 and several other Lexuses (USDM cars) that had the 2JZ-GTE VVTi...and i'm pretty sure my sister's IS300 is MAF-based. i just wasn't sure if ALL VVTi 2J's were MAF-based.
Ok, you have been posting wrong information all morning and I didn't say anything, but you keep insisting on miss informing people.


The IS300 never had a GTE motor. It had a GE motor. And you are wrong about the MAP being more accurate. It is not. The MAF is a direct measurement of the airflow coming into the engine, not a calculation like the MAP sensor. And for the record you can't legally vent a MAF to the atmosphere. That is why BOV are illegal in CA.
 

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Ok, you have been posting wrong information all morning and I didn't say anything, but you keep insisting on miss informing people.


The IS300 never had a GTE motor. It had a GE motor. And you are wrong about the MAP being more accurate. It is not. The MAF is a direct measurement of the airflow coming into the engine, not a calculation like the MAP sensor. And for the record you can't legally vent a MAF to the atmosphere. That is why BOV are illegal in CA.
i stand corrected about which is more accurate, MAF or MAP. but that doesn't change the fact that people still run BOV's, illegal or not. and that doesn't change the concept that, if someone is using a BOV, it will cause the MAF to report an incorrect value to the ECU, causing you to run rich...and there's nothing wrong with that - you're just wasting a bit of gas (as opposed to running lean and doing actual damage to the motor). but the bottom line is that, in this situation, a MAF is not providing as accurate a reading as a MAP system would. so, i suppose a MAF reading is more accurate than a MAP reading when the MAF is taking accurate measurements 100% of the time.


...and obviously the IS300 (or any other Lexus) never had the GTE motor - i clearly had a memory lapse while reffering to ALL VVti 2J's, both N/A and TT, and momentarily failed to realize that mitulparmar787 was referring to GTE's only...it happens to the best of us now and again...
 

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i stand corrected about which is more accurate, MAF or MAP. but that doesn't change the fact that people still run BOV's, illegal or not. and that doesn't change the concept that, if someone is using a BOV, it will cause the MAF to report an incorrect value to the ECU, causing you to run rich...and there's nothing wrong with that - you're just wasting a bit of gas (as opposed to running lean and doing actual damage to the motor). but the bottom line is that, in this situation, a MAF is not providing as accurate a reading as a MAP system would. so, i suppose a MAF reading is more accurate than a MAP reading when the MAF is taking accurate measurements 100% of the time.
Can you name one car manufacturer that runs a MAF with a venting bov.... ? :scratch:

There are none. When used properly the MAF will always be more accurate then a MAP sensor.
 

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Can you name one car manufacturer that runs a MAF with a venting bov.... ? :scratch:

There are none. When used properly the MAF will always be more accurate then a MAP sensor.
that's EXACTLY my point. there are no manufacturers of F/I cars using a MAF in conjunction with a venting BOV b/c the amount of air passing by the MAF can and will sometimes be greater than the amount of air that actually makes it into the intake manifold and finally into the combustion chambers...and running rich (although it doesn't do any damage to the motor) is a problem for manufacturers b/c it raises fuel economy issues. i'm not sure what you're getting at here :scratch:

look man, i'm not trying to argue with you. there is no doubt that on an N/A car, or an F/I car with no pressure release valve on the intake side (BOV or BPV), a MAF takes a more accurate reading b/c 1) it measures the VOLUME of air directly (as opposed to measuring the PRESSURE of the air and calculating the volume indirectly), and 2) the same amount of air passing by the MAF is going to pass into the combustion chambers (assuming there are no intake-side leaks downstream of the MAF) b/c there is no BOV or BPV there to vent and decrease the volume of air. but we're not specifically talking about N/A cars or F/I cars without venting (atmospheric OR recirculating) on the intake side.
 
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