MAP and MAF

[willbur]

Greetings All-
Why do some engines use both map and maf sensors? I understand using the map if engine is boosted but not both for na engine. Is map a backup?

 

[jtay2024]

I get the feeling that sometimes it's for fault detection purposes. For example, if you had an air leak on the intake between the MAF sensor and the MAP sensor, the readings would end up unexpectedly far apart and a fault code could be created. Or if the MAF sensor goes bad (which can happen from contamination or damage), then the MAP sensor would read different again, throwing up a fault.

 

[Kalle.J]

MAP and temperature sensors are often combined units these days. And you want a temprerature sensor after the IC.
Easier turbo control, leak detection ?

 

[dumkid]

Some cars only have a maf and a barometer, (Volvo) and some only have a map (chevy) they both can be used to calculate air density and flow and volumetric efficiency, so you really only need one.

 

[CarDoc66]

Good question. There are a few reasons but mainly on turbo cars the MAP sensor helps with boost signal management, and most other cars it’s probably to get the calculated engine load reported back to the ecm faster and more precisely (emissions).

 

[SHOZ]

On the Genesis Coupe turbo there is a MAP sensor before the throttle body and one in the intake manifold. On the NA V6 motor they have both a MAF and a MAP, the MAF has the intake air temp sensor in it. On the turbo the intake MAP has the IAT.

 

[willbur]

Some cars only have a maf and a barometer, (Volvo) and some only have a map (chevy) they both can be used to calculate air density and flow and volumetric efficiency, so you really only need one.

I know that...but why both?

 

[dumkid]

I know that...but why both?

Redundancy

 

[techoguy]

I'm not an engineer, but I've read that engines using valve overlap can get some complex airflow inside the inlet manifold that one sensor alone can't accurately measure.

Also, some engines use stratified charge mode (throttle valve fully open, engine speed/load controlled by injector pulse-width). A MAP sensor would be next to useless under these conditions.

 

[SHOZ]

I'm not an engineer, but I've read that engines using valve overlap can get some complex airflow inside the inlet manifold that one sensor alone can't accurately measure.

Also, some engines use stratified charge mode (throttle valve fully open, engine speed/load controlled by injector pulse-width). A MAP sensor would be next to useless under these conditions.

With the adjustable valve timing it is pretty easy to get 100% load values out of a NA motor. My old Accent with 190k miles can hit 100% at 6500 rpm! It has only the MAP.

 

[ARCOgraphite]

I use MAP as a backup for WAZE - especially if EMP are anticipated.


Seems MAP could help with transitional enrichment. Altitude sense. Also keep an eye on EGR, PCV and EVAP "controlled leaks" into the I.M.

Biggest failing with ECU sensing and reporting over the decades is not enough crosschecking.

Like calling switching Lamba 1 value golden über alles or even MAF golden. Lots of "mystery novel" poor running cars due to faulty sensing.

 

[SHOZ]

The Ford Taurus V8 SHO came with the COPs that Ford just came out with in '96. They were terrible for micro cracking and shorting out. But if the cylinder closest to the MAF had the bad coil it would trip the too lean MAF code.

 

[Luftmasse]

MAF sensor would be the primary use of calculating air and load.

MAP sensor is used to monitor the EGR under load.