12 replies to this topic

[.Jack.]

I have a K&N filter on my SPI cooper, it currently does not have an intake sensor on it (the green one!). I have never had any problem with this however i was wondering if it has any effect upon the performance of the engine once its hot? Does not having one make the ecu revert to thinking the intake is cold, therefore run lean or does it do the opposite and think that its running hot? thanks

[IainStallard]

Without the sensor, the temperature defaults to 36 degrees centigrade

[.Jack.]

Ok thanks, what effect will this have on the running/performance of the engine on a normal, lets say 15 degree day?

[IainStallard]

Probably not too much of a difference, really only affects cold starting

[Fast Ivan]

at best the ecu wont be able to calculate the amount of air being used accurately and therefore the fuelling wont be correct, how critical it is I don't know but it wont be running perfect

[IainStallard]

The air temperature sensor contributes to 25% of the fuelling I think

[Fast Ivan]

The air temperature sensor contributes to 25% of the fuelling I think

 

wow that's quite critical then!!

where did you get that info from iain?

[FlyingScot]

MEMS uses the air temperature measurement to infer the density. Sprocket quotes 20% effect on fuelling' but either way it's going to make a difference.

FS

[IainStallard]

The air temperature sensor contributes to 25% of the fuelling I think

 
wow that's quite critical then!!
where did you get that info from iain?

I stand corrected, 20% according to FlyingScot and Sprocket

[.Jack.]

Maybe I should put one on then!

[xrocketengineer]

Not trying to be a smart ass, but the MEMS system is of the earlier type of electronic fuel injection with no MAF (mass air flow) sensor. Instead it uses a cheaper MAP (manifold absolute pressure) sensor. Therefore, since the ECU knows the volume of air flowing based on the displacement of the engine and RPM. The MAP sensor provides the manifold pressure and the air temperature from the AIT (air intake temperature) sensor. From these two the ECU can guesstimate the air density. With the density and the volume it then calculates an approximated mass flow rate. Then using the CTS (coolant temperature sensor) the mixture is finally fine tuned based on richer if the engine is cold and leaner if warm. And finally the O2 (lambda) sensor determines if the mixture is stoichiometric (around 14 to 1 air/fuel ratio by mass) since that is what the catalytic converter requires in order to operate properly.

[FlyingScot]

Better more detailed explanation ^^^^^.
Which is why it is important that all the elements of the system are present and working correctly.

FS

[Fast Ivan]

Not trying to be a smart ass, but the MEMS system is of the earlier type of electronic fuel injection with no MAF (mass air flow) sensor. Instead it uses a cheaper MAP (manifold absolute pressure) sensor. Therefore, since the ECU knows the volume of air flowing based on the displacement of the engine and RPM. The MAP sensor provides the manifold pressure and the air temperature from the AIT (air intake temperature) sensor. From these two the ECU can guesstimate the air density. With the density and the volume it then calculates an approximated mass flow rate. Then using the CTS (coolant temperature sensor) the mixture is finally fine tuned based on richer if the engine is cold and leaner if warm. And finally the O2 (lambda) sensor determines if the mixture is stoichiometric (around 14 to 1 air/fuel ratio by mass) since that is what the catalytic converter requires in order to operate properly.

smart arse!!