Map Sensor

[hoony]

hey everyone,

i've done a search but have not found any answers, was hoping you guys could provide some for me

i have an R34 GTT manual and was wondering, what the hell does the map sensor do and what is its use besides being a boost cut...?

my map sensor decided to die at the workshop and i'm waiting for a new one to come from Japan and after i get the new one thrown on it will finally get dynoed...

however, it drives nicely and doesn't seem to have any problems except turning the engine check light on, the workshop says it's fine to drive besides the fact that the car may feel a bit crappy in the lower revs (i have to drive it because it's my only car, map sensor will take ten days to be sent, i pick up the car tuesday and maybe half a week later the map sensor will arrive)

was told that guys that throw on high-mounts end up getting rid of them anyway and obviously if you go for an aftermarket ECU (which i will be in the near future) like Power FC or Vi-PEC you get rid of it too

so really i just want to know what it does, besides being a boost cut and making my car run slightly shit

any help would be greatly appreciated folks, thanks in advance

Andrew

[paulr33]

mythbusters ahoy!

the r34 GTT uses a map sensor, to check for excessive boost pressure, more as a fail safe in case something fails or someone is fiddling

the ecu when it detects a high level of boost, drops to safety maps to protect the engine

a map sensor is used to, as the name implies, sense manifold pressure or "sense mass air pressure".

EFI based cars commonly use an airflow meter (or hotwire afm or MAF) to detect how much air the engine is sucking it.

it then uses this information to tell the computer so it can work out how much fuel to add into the engine

an alterante method to this, is to remove the MAF or hotwire AFM and replace it with map sensor.

the computer then uses the pressure signal as a "engine load" much the same as a MAF / hotwire sensor and the engine adds in fuel accordingly.

its commonly done when uses do big turbocharger upgrades etc.

so in summary, do nothing and just keep driving around with the check engine light on (commonly listed as CEL)

but you should certainly replace / fix it as its probably it safety maps (ie lower timing and slugghish)

[aphid]

The firmware on the stock ECCS ecu can also be reprogrammed to use only the MAP sensor, or to replace the afms with MAP sensors.. if you're keen

[Duncan]

and... you will still get the same error code on a PowerFC because it checks values of all the factory sensors. Your probably won't on a link/vipec unless someone has gone to the trouble of programming it specifically for the expected values of a 34 GTT as they are generic not model specific

If you have a powerfc one option is to feed the correct voltage to the MAP signal in pin to remove the error. This is one of the changes required to run a 34gtt powerFC in a stagea.