Maf Vs. Map

[shayrgob240]

Why is it desirable to omit the MAF for the MAP to take its place? In other words, why is it better for the sensor to sense pressure than for it to measure mass? Is the MAP more reliable and therefore tuning's more accurate? And I'm obviously asking about when you have a standalone. THanks in advance.

[chmercer]

maf is more accurate but in high boost applications you cant very well have like 6 inch intake piping to accomidate a large enough maf.

[scottie]

MAFS are known to be more reliable because they rarely go lean (unless you push beyond their HP rating). MAPS can go lean if not tuned correctly but pressure it more accurate reference than air flow. I would say that if you dont plan on going big there is no need to go with a MAP.



Scott

[Josho]

Old thread but is there anymore info on this subject? Ive been reading up on this on other sites but not much has been mentioned on here. I would like input from some of you guys, hopefully somebody who is actually running a MAP sensor. I have an AEM EMS and was just curious if converting to a MAP sensor is worth the effort? Im not going for a large amount of power, maybe 350whp with my GT2871.

[240Shwag]

Old thread but is there anymore info on this subject? Ive been reading up on this on other sites but not much has been mentioned on here. I would like input from some of you guys, hopefully somebody who is actually running a MAP sensor. I have an AEM EMS and was just curious if converting to a MAP sensor is worth the effort? Im not going for a large amount of power, maybe 350whp with my GT2871.

Don't bother. Stay MAF.

[Josho]

Im wanting a little more informed response. I want to know what the gains are strickly for an sr20det. Pro's an cons of both of them. Why its better to run one or the other.
I dont want to make my decision because you told me not to do it, I would like to weight out the pro's and con's and decide after gathering the good and bad for both set-ups.
I appreciate the response but could you tell me why I should stay with my MAF rather then converting to MAP?

[revolutionz_s13]

MAP will give you a little more flexibility in tuning, as the sensor is mounted in the intake manifold. You can vent your bov to atmosphere easily, and boost leaks wont affect the car as much if you have a pipe pop apart. Other than that, when you put the intake on the turbo, you dont have to worry about a maf being so far away from the turbo or anything like that, just put the filter on the pipe and be done with it.

[Josho]

All that sounds great! Which is why Im confused about a lot of people saying dont go with a MAP, keep the MAF. Is that from lack of experience/knowledge or do they know something that others dont know. MAP sounds to me like the better choice as long as Im going with a standalone. I hear its also easier to tune the AEM EMS if you have a MAP. All the pro's seem very good about going with a MAP... Is there any bad side affects?

[Sil-Eighty SE-K]

With map you lose load point resolution once target boost is hit
Whereas maf will still have resolution throughout the rpm band as airflow increases (pressure remains constant at target)

Maf is also easier to tune there is no base map and correction map.... just correction
It'll run out of the box on a base map much better as well

Unless you're maxing out any mafs available to your setup (and you can run 600hp with a z32) there is no sense going to a map based setup IMO
And even then you can have custom mafs made to measure pretty extreme amounts of airflow

They say the drawback of mafs is a restriction in the intake... True with a stock mafs that bottlenecks... Run an rb25 or z32 and there is no restriction they are 80-90mm just like your inlet pipe

I have a map based PFC on one car and mafs based on another so Im familiar with both

Just my $.02

[Josho]

With map you lose load point resolution once target boost is hit
Whereas maf will still have resolution throughout the rpm band as airflow increases (pressure remains constant at target)

Maf is also easier to tune there is no base map and correction map.... just correction
It'll run out of the box on a base map much better as well

Unless you're maxing out any mafs available to your setup (and you can run 600hp with a z32) there is no sense going to a map based setup IMO
And even then you can have custom mafs made to measure pretty extreme amounts of airflow

They say the drawback of mafs is a restriction in the intake... True with a stock mafs that bottlenecks... Run an rb25 or z32 and there is no restriction they are 80-90mm just like your inlet pipe

I have a map based PFC on one car and mafs based on another so Im familiar with both

Just my $.02

I see your points aswell. Would you still run a MAF in my situation? Considering Im running an AEM EMS. I've read that AEM is set-up for MAP and makes it easier for tuning.
I guess what Im trying to do is seperate the good/knowledgeable info from BS info.

Thanks

[ILoveJDM]

one less important note, but a really good one,

if youre far away from home and pop the intercooler piping right off and have no tools, you can still drive home on map. where as with MAF youre SOL and have to call a buddy etc. especially if youre piping is complex and has the couplers behind body parts etc etc

[Josho]

Have any of you guys converted from MAF to MAP? If so, PM me please.

[usdm180sx]

Having a filter and intake pipe that goes straight to the turbo is cool.

[Josho]

I think so too!!

[Corbic]

MAP all day long.

[lflkajfj12123]

Having a filter and intake pipe that goes straight to the turbo is cool.

King of Dope Total Knockout

[Corbic]

King of Dope Total Knockout

Not to mention you won't have any issues with BOVs and ICs.

[JSimpson]

Can a stock nissan ECU read a MAP sensor? Like an AEM 5 or 3.5 bar sensor...?

[SLiDe_WaYz]

Can a stock nissan ECU read a MAP sensor? Like an AEM 5 or 3.5 bar sensor...?

No, don't even think a rom tune can run a map.

[JSimpson]

Didnt think so. MAP FTW on an AEM EMS. Anything else, keep it simple: MAF

[lflkajfj12123]

Can a stock nissan ECU read a MAP sensor? Like an AEM 5 or 3.5 bar sensor...?

no way in hell

[Emeru]

Make sure if you stay MAF you vent the BOV back to the intake, if not when the BOV opens the ecu has read all that air let out and will dump all the fuel for air thats not there.

[SomeoneWhoIsntMe]

Can a stock nissan ECU read a MAP sensor? Like an AEM 5 or 3.5 bar sensor...?the stock ECU uses airflow to calculate fueling. you cannot replace airflow with pressure in the ECU's equations and come out with the same fueling curve.

[SLiDe_WaYz]

Make sure if you stay MAF you vent the BOV back to the intake, if not when the BOV opens the ecu has read all that air let out and will dump all the fuel for air thats not there.


Not sure on that one, I have a atmospheric BOV ( GReddy Type R ) and I dont run rich or lean when im under boost from it opening or closes. Does it vary on BOV types ?

[slowvia]

Make sure if you stay MAF you vent the BOV back to the intake, if not when the BOV opens the ecu has read all that air let out and will dump all the fuel for air thats not there.

Is there anyway to account for that in a tune? Ive herd that you can minimize the problem, but not eliminate it completely. Ive heard people talk about it before, but Im not sure how credible they are.
And if I remember correctly, MAF is much more user friendly, MAP's require tweaking when you change other things on the motor, whereas MAF's are pretty straight forward. Then again I havent really dealt with any of this so Im kinda just blowing it out my ass:naughtyd:

[SomeoneWhoIsntMe]

Not sure on that one, I have a atmospheric BOV ( GReddy Type R ) and I dont run rich or lean when im under boost from it opening or closes. Does it vary on BOV types ?An atmospheric BOV dumps a volume of metered air out of the inlet tract whenever it opens. that volume of air leaving what is supposed to be a closed system will throw the ECU off - it has no way of knowing that that airflow has gone somewhere else than into the engine, so it still injects fuel at the AFR it's trying to hit at that point in the fueling map.

There's not really any way around it, if you create a boost leak post-MAF with an atmospheric BOV, the car WILL run rich whenever it opens. The duration and severity of the rich spike depends on a whole multitude of variables (tune, BOV type, BOV spring stiffness, turbo, target boost, intake piping, etc etc), so it's up to you to figure out if it's a big deal on your car.

[ILoveJDM]

Is there anyway to account for that in a tune? Ive herd that you can minimize the problem, but not eliminate it completely. Ive heard people talk about it before, but Im not sure how credible they are.
And if I remember correctly, MAF is much more user friendly, MAP's require tweaking when you change other things on the motor, whereas MAF's are pretty straight forward. Then again I havent really dealt with any of this so Im kinda just blowing it out my ass:naughtyd:

i used to have a MINES tuned ecu on an sr20. the never stalled after shift with maf or on decel, the tune was made so that upon decel, it would catch itsself on idle at 1100 rpms or so, and slowly come down to proper idle speed. this was with HKS ssqv, and no BOV at all.

after that i went from MAF to MAP with a powerFC, full-race gt30. saved time making intake piping, sometimes ran just a filter right on the turbo. had a greddy manifold and the MAP sensor screwed into the tapped holes on the bottom. couldnt have been easier than this. tuning it by myself too was also a cakewalk.

[SomeoneWhoIsntMe]

Is there anyway to account for that in a tune? Ive herd that you can minimize the problem, but not eliminate it completely. Ive heard people talk about it before, but Im not sure how credible they are.
And if I remember correctly, MAF is much more user friendly, MAP's require tweaking when you change other things on the motor, whereas MAF's are pretty straight forward. Then again I havent really dealt with any of this so Im kinda just blowing it out my ass:naughtyd:It's possible to tune around it, but I expect it would be a bad idea.

You'd have to pick what condition you want to try and tune around... for instance, if you were concerned with getting the car as fast as possible in a straight line and you were convinced that bogging during gear changes was slowing it down, then you would log data while doing WOT runs going through a few gears. Now, I don't know which variables the base fueling map on the Nissan stock ECU is based on, but based on how it works on my WRX it's probably something like RPM vs. Load (calculated based on TPS and MAF). So, you'd figure out the RPM and Load where the BOV opens in your data logs, then take fuel away from that part of the map until you're at the AFR you want to be at under fast shifting, and the car behaves how you want under those conditions.

Problem is, the BOV being open has almost nothing to do with RPM vs. Load. During your tuning sessions doing WOT runs on the freeway, the car may behave much better during shifting, but if there's another situation that can cause the engine to be at the same RPM and Load that you just changed the fueling for, but NOT open the BOV, then you're fucked. If you were running 20% rich under shifts, you're now going to run 20% lean if the BOV doesn't open and you hit that cell in the fueling table.

I don't know how well I explained that, if it doesn't make any sense then let me know.

[fliprayzin240sx]

Both setup up has its pros and cons. I have run rom tunes and piggyback SAFC with Z32 MAFs. I decided to go MAP for the simple reason of not having to worry about getting a bad MAF again. Also, if I have a boost leak or crash the car where the piping are destroyed, I can still drive the car home no problem. The only downside of a MAP is if you have any boost leak, the car wont "let you know" it has a leak. On a MAF setup, if you have a leak, the car will run rich and potentially bog. On a MAP setup, the car will just feel slower.

[Corbic]

You could did the BOV or just Recirculate it (ala stock style)...

[daftphunk]

I was under the impression that ambient temperatures would also affect the tune/how your car would run with a MAFS as well, no?

[Melonburst]

As far as the load sensors (MAF vs. MAP) debate goes. Yes, MAF's are preferred for low horsepower applications because they are easy to tune with higher accuracy success rates and enable tighter control of emissions. They measure actual air flow and take into account barometric pressure, altitude changes, humidity, and ambient temperatures and adjusts fuel accordingly but also has a higher chance of failure due to its design, break the hotwire with a slight wall tap (combined with old crappy S-Chassis harnesses) and you run rich and risk engine failure. Another downside to MAF sensors is that at idle or low RPM situations there can be vacuum pressure which tampers with its accuracy, they also don't respond well to the cold since condensation can occur on the hotwire again leading to inaccuracy.

Now MAP sensors are praised for their simple and minimalistic design measuring actual manifold pressure (Pressure! which is Baro Pressure + Altitude changes) but does NOT take into account humidity. Then the IAT sensor measures the temperature and is read earlier by your EMS to calculate A/F ratios and improving throttle response over MAF sensors. MAP sensors rarely if ever fail/break, again due to its design. MAP sensors aren't as accurate and require a lot of knowledge to become so and in addition are much harder to tune. A properly tuned MAP based system is far more beneficial compared to a MAF based system on a forced induction car. Especially when you're running a car with over 450hp.

In conclusion they both have their pros and cons and ultimately it comes down to the users preference and platform/supporting mods and the tuners skill level. Hope this clears things up a bit.

[S14DB]

MAP does not take Barometric Pressure into account unless the ECU is designed to take a Baro reading before the engine starts. It goes on the Vacuum Pressure at idle compared to the expected value. If the VE of the engine changes it can't compensate.

Some modern ECUs will quickly grab a Baro Value on ignition on before engine start to correct the base map. Earlier models had a idle trim pot on the ECU to dial it in depending on the altitude and VE.

I have not seen a aftermarket ECU that grabs the Baro Value before engine start.

[Gription]

I'm surprised no one has suggested doing a blow through maf setup.

[smelly240]

MAP does not take Barometric Pressure into account unless the ECU is designed to take a Baro reading before the engine starts. It goes on the Vacuum Pressure at idle compared to the expected value. If the VE of the engine changes it can't compensate.

Some modern ECUs will quickly grab a Baro Value on ignition on before engine start to correct the base map. Earlier models had a idle trim pot on the ECU to dial it in depending on the altitude and VE.

I have not seen a aftermarket ECU that grabs the Baro Value before engine start.

AEM has an internal baro - Haltech has a internal baro -

just about every standalone has some sort of baro (some do it before u start the engine like lots of stock computers - like megasquirt)...

Blow through lowers the max hp capable of the maf. I maxed out a z maf at 456 - put it draw through and i got 51 more hp before it maxed... Also nissan mafs dont seal well... you gotta fill them up with epoxy.

If you're running 360hp on your 2871 and dont plan on going much past 400 - maf is great. After 400 - I recommend a standalone. Yes you can make 500 something on a std ecu - but you'll find out that it is far less stable.

readings get less stable - and the runs arent going to be as repeatable. A lot of it has to do with the stock crank/cam angle sensor with its remarkable resolution... it just isnt good for a hard revving engine. It is excellent until you get up in HP.

AEM ships now with a CAS disc with 24/1 configuration with their EMS because of stability issues at high HP/RPM. Mazworx also makes a sweet trigger setup similar to what t1 does for hondas.

Mazworx SR Hall Sensor Kit - Electronics - Mazworx (http://www.mazworx.com/product/electronics/hall-sensor-kit/mazworx-sr-hall-sensor-kit)

Either way - SD/maf - both have positives and negatives - but it depends what setup you're running. Street cars dont need to go MAP. Racecars and high HP cars definately benefit from it.

[Corbic]

Either way - SD/maf - both have positives and negatives - but it depends what setup you're running. Street cars dont need to go MAP. Racecars and high HP cars definately benefit from it.

LS-series run MAP, and I believe the JZ-motors are all MAP as well.

A GM MAP sensor is around $60. MAF sensors are stupid expensive.

[smelly240]

LS-series run MAP, and I believe the JZ-motors are all MAP as well.

A GM MAP sensor is around $60. MAF sensors are stupid expensive.

LS1 has a maf as do all LSX

2jz has a maf (except Aristo)

a nice map (stainless steel 3.5 or 5 bar) is like 155 bucks GM 3bar is ok - but i recommend a restrictor pill or a tiny vac line or you'll see all sorts of fluctuation comapred to a nice map sensor.

A z32 maf at the auto parts store is like 120

[Corbic]

LS1 has a maf as do all LSX


I guess I haven't been around a stock LS1 in to long a time. My 5.3 setup uses a MAP.

[SomeoneWhoIsntMe]

I have not seen a aftermarket ECU that grabs the Baro Value before engine start.megasquirt does, and you can add a second MAP sensor to take constant baro readings