Intake Modifications and Fuel Flow

[thatguy11]

If you increase airflow to an engine, whether it's through a new intake manifold, cold air intake or simply better ducting, does this need to be done in conjunction with a tune to the fuel map?

Obviously adding a turbo/supercharger needs to be done with an accompanying remap, but for small increases in airflow i.e. intake modifications, should a modern car's ECU trigger any necessary adjustment in fuel flow to avoid the engine running lean?

Let's be honest about cold air intakes; they don't really increase power, at least not noticably; they just provide a better noise. How often does a higher-flow air filter/intake get installed without doing anything to the ECU? 95% of the time?

[anonymous-user]

1) most "free flow" air filters do nothing, because since about 25 years ago, OE's have designed there intake systems very well. The gains are incredibly small (significantly less than 1%) So no extra air needs no extra fuel

2) Most EMS systems use a MAF meter to actually measure the amount of air going into the engine, so more air = more fuel

3) all EMS systems have closed loop AFR control. These systems have around a 10 percent trimming capability (plus or minus) and the closed loop adaption value is carried across to any open loop operating zone

[shalmaneser]

thatguy11 said:

If you increase airflow to an engine, whether it's through a new intake manifold, cold air intake or simply better ducting, does this need to be done in conjunction with a tune to the fuel map?

Obviously adding a turbo/supercharger needs to be done with an accompanying remap, but for small increases in airflow i.e. intake modifications, should a modern car's ECU trigger any necessary adjustment in fuel flow to avoid the engine running lean?

Let's be honest about cold air intakes; they don't really increase power, at least not noticably; they just provide a better noise. How often does a higher-flow air filter/intake get installed without doing anything to the ECU? 95% of the time?

The ecu monitors the fuel/air mixture via the lambda sensors. It can increase the amount of fuel or decrease the amount by about 10% to account for wear to the engine or variations in fuel quality etc. Any more than that tends to cause a engine warning light.

For example, if a fuel pump is on the way out and delivering a lower fuel pressure (assuming this is not logged which is common on older cars) then the ecu will increase the length of the injector pulse accordingly.

This also senses knock very accurately so can reduce the advance when the car is running on 95 octane (for example) and increase it with 98/99/101 octane for increased power.

Reducing intake restrictions will increase the amount of air the engine is 'seeing' thus potentially triggering a lean condition, in response the fuelling is increased resulting in increased power to some extent.

[Olivergt]

No 2 from above ^^

The MAF measures the amount of air going in to the engine, the ECU will then figure out how much petrol to add.

I'm sure there are limits to how much extra it can add, but as MT mentions the difference between a std air filter and a free flow, cold air intake will be minimal and probably less than the difference between a hot summers day and cold winters day.

https://www.engineersedge.com/calculators/air-dens...