Cold Air Intakes & MAF Sensors
5 min read
Cobb Big SF intake needs a remap
Cold air intakes, probably thee most popular aftermarket modification.
Prices range from under 50 dollars for generic, universal, non branded products to over 2000 dollars for intakes made of exotic materials like carbon fibre and Kevlar.
One thing 99.9% of these intakes have in common, regardless of price, is they use the original MAF sensor.
Features
One of the biggest “features” highlighted by cold air intake manufacturers is the “big bore”/”mandrel bent”/”smooth piping” etc of their intakes.
A few issues
While the pipe may be a larger diameter the intake system will almost always neck down to the diameter of the original pipework, at least in the section that contains the MAF sensor.
The intake manufacturers have to do this to maintain the accuracy of the MAF sensor.
The intake is only as good as the biggest restriction, the neck of the “performance” air filter may be three inches versus the two inches of the factory intake but if the factory intake and the performance intake both have the same diameter at their narrowest point the benefits of bigger pipework elsewhere in the intake will probably be negated.
Having said all this, generally speaking cold air intakes don’t yield big power gains, at least on engines running close to stock power so the restricted air flow through the MAF sensor is usually a mute point.
Sensor accuracy.
One of the key points in fitting a cold air intake is that it removes the “restrictive” factory pipework with “high flow” pipework.
By definition this means altering the airflow through the intake system and when we alter the airflow through the intake system it is safe to assume that the airflow through the MAF sensor will also be altered.
If the aftermarket intake system is as good as the manufacturer claims flow should be up. This is fine and the factory MAF sensor should pick up the extra air flow.
However if the pipework is changing the path of the air through the MAF sensor, the accuracy of the sensor may be reduced.
For example on the factory intake piping the MAF sensor is placed before a bend in the piping whereas the performance intake either removes the bend completely or puts the sensor downstream of a bend.
If an aftermarket intake manufacturer wants to improve the factory design they must make changes to the pipe routing.
If an aftermarket intake manufacturer wants the end user to have no issues after fitting their intake system they have to keep the routing, the positioning, the dimensions the same.
You see the issue?
If the factory pipework was perfect, great flow, accurate MAF readings, why would we fit an aftermarket intake?
If an aftermarket intake is mirroring the positioning and routing of the factory intake system, why would we fit it? It’s the same as the original pipework.
Altered Flow
If an aftermarket intake manufacturer bins the entire design of the original intake and comes up with its clean sheet design that puts performance above every other consideration (like sound or lack of it) it should acknowledge that the MAF sensor is not going to be performing the way it was in the original intake.
If the MAF sensor is not giving an accurate reading to the car’s ECU than fueling is not going to be what it could be. Even though the engine is consuming more air, the less than optimum air fuel ratio with the new intake wipes out most of not all of the power gains.
Three Solutions to this Problem.
1.The intake manufacturer could say that their intake requires a remap or that their intakes works best when the engine is remapped. Very rare but it happens. Cobb Tuning sticks out here with maps designed specifically for their intakes.
2.Or they can supply their own software/product with their intake so the customers realises the full potential of their products. I do not know of a single manufacturer that does this. Cost is probably prohibitive.
3.Not do it. Just make an intake that mirrors the factory setup. Most intake manufacturers do this.
Custom Intakes.
It is relatively easy to make a completely custom intake system at least with regards to the piping and hoses.
I think it is safe to say MAF sensor placement in a custom intake system will not be exposed to the same rigorous testing as the OEM intake system.
The MAF sensor will be put where it fits and/or where it looks like it will get the most airflow. This location may or may not match with the car manufacturers placement decision.
With a custom intake we are freed from the constraints of making something that is easy to service and/or something that is quiet.
Modern engines are very well designed from the factory but if you have modified your engine your engine may be flowing more air than the designers anticipated. In these circumstances we can improve the factory design, at least from a flow point of view.
This is the easy bit but we also need to give the ECU an accurate signal from the MAF sensor. We could tune the MAF sensor position to suit the ECU.
If we had a lot of spare time and money.
Or we can remap the standard ECU or fit a MAF scaling device such as the MAF Manager Rivazza which allows the user the customise the MAF signal according to RPM and load.
In summary
Unless a intake kit manufacturer is saying you should use their product with a remap to get the most benefit, we can probably assume that the air flow characteristics through the intake system is the same as the factory intake piping (and at least through the section of the intake that contains the MAF sensor)
Does same air flow mean no extra power?
It depends on the vehicle and it depends on the intake. If there is an actual restriction in the factory intake system then less restriction will make more power. We can test if our intake system is a restriction by using a vacuum gauge between the air filter and the turbo. If we get a negative pressure ie pressure less than ambient there is a restriction and a “free flowing” intake might make more power.
One thing we can sure of.
If a manufacturer (such as Cobb) says their intake needs to be used with a remap we can be sure that the intake is changing the airflow the intake system and that the intake is not just a cosmetic addition.
Question?