The most common criticism we get on this part deserves a straight technical answer rather than a marketing one: what the openings are for, what they are not, and why the sealed factory airbox has a specific weakness the moment you pull away from a light.
The criticism, stated fairly
The objection goes like this: McLaren engineered a sealed airbox fed by ducting from the side scoops, so the engine only ever breathes cool outside air. Cutting openings into the top of that box puts the filter in communication with the engine bay. The engine bay is hot. Therefore the system is a hot air intake, and whatever it gains is given back through higher intake air temperatures and lower charge density.
That is a coherent argument. It is also the argument we had to answer for ourselves before committing to the design, because if it held across the operating range we would not ship the part. Our position is that it describes one operating condition accurately and then generalises it to conditions where it no longer holds.
How the factory air path is actually arranged
On these cars the airbox is completely sealed. Its only air source is a duct that starts at the side scoop, runs back through the car, and terminates in the box. Air travels that full length, passes through the filter, and only then reaches the turbo inlets. There is no secondary path and no relief of any kind.
That is a long run with bends in it, and every bend and every metre of duct wall costs pressure when air is moving through it. This is ordinary friction and form loss, not a design flaw. The interesting question is what pays for that loss.
At speed, the scoop pays for it
Once the car is moving, the side scoop is pressurised. Air is being forced into the duct by vehicle speed, and the pressure behind it covers the losses along the way. The box ends up at or above ambient and the engine is fed cool outside air with something pushing it along. This is a good design, and it is why we did not touch the ducts.
At a standstill, nothing pays for it
Stop the car and the ram-air effect goes away. Nothing is pressurising the scoop. The engine still has to move the same mass of air, and the only thing available to move it is manifold vacuum acting back through the whole path — scoop, duct, box, filter, and finally the compressor inlets.
The result is a measurable pressure drop ahead of the compressor. Lower pressure at the inlet means less dense air per unit volume, so the compressor has to work harder for the same mass flow. To the driver that reads as a slightly lazy response in the first moment off the line, before speed builds and the scoop starts doing its job again.
The window we are addressing is narrow and specific
This is not a claim that the factory intake is restrictive in general. It is a claim about one operating window: high air demand with no vehicle speed. That window happens to contain the moment most owners care about most, which is a standing start.
Figure 1 — Airflow, standstill vs. at speed
What the supplemental openings actually do
They give the airbox a short, low-restriction path to draw from during the window in which the long path is unassisted. When the box is under negative pressure, air arrives by whichever route costs it least, and an opening a few centimetres from the filter costs far less than the full duct run. The engine gets the mass of air it is asking for without pulling as hard for it.
What they are not
They are not a replacement for the factory cold-air ducts. We kept those ducts because they are the primary and the better air source whenever the car is moving. Anyone who removes or blocks them and relies on the openings alone has misread the design.
This is the part that tends to get missed in the forum version. Flow through an opening requires a pressure difference across it. At a standstill that difference exists and the openings do useful work. As speed builds, the box goes from negative to at or above ambient, and the condition that was drawing engine-bay air through them largely disappears. “Hot air intake” therefore describes a state that exists at zero mph and stops being descriptive once the car is moving — which is the only time intake temperature is doing meaningful work on your power figure anyway.
The other reason we replace the airbox: the factory foam
Separate from the flow argument, and worth reading even if everything above left you unconvinced.
The factory McLaren airbox contains foam. As these cars age, that foam degrades. It loses structure, breaks apart, and the debris does not leave the box — it ends up sitting against the filter element. Two things follow. The first is added restriction, unevenly distributed across the filter face, which is the opposite of what anyone wants regardless of which intake they run. The second is a filtration question: material shedding inside a path that ends at two compressor wheels is not something to leave unexamined.
You do not have to take our word for it. Pull your own airbox and look. On a car of a certain age and mileage you will either find intact foam or the beginnings of what we are describing. Either result is worth knowing.
Our system replaces that component entirely, so there is no degrading foam in it to shed. We would rather you check your own car than take a claim at face value.
What we are claiming, and what we are not
We want to be precise here, because the temptation in this category is to overstate.
- What we found in our own testing: the car is significantly faster from a standing start. That is our testing result on our cars, stated as such — not a lab figure and not a certified measurement.
- What we are not claiming: a peak power number, a percentage, or a wheel horsepower figure. We have not published one and we are not going to imply one.
- What we are not claiming: that the factory intake is poorly designed. It is well designed for the condition it was designed around, which is a car that is moving.
- What we are not claiming: that intake air temperature is irrelevant. It matters. Our argument is that the condition drawing warmer air through the openings largely coincides with the condition in which you are not asking for sustained power.
Where this leaves a sceptical owner
If you have read this far and still think the sealed box is the better answer for the way you drive, that is a defensible position. A car that lives on long, fast roads spends almost none of its life in the condition the openings were designed around.
If you spend real time at a standing start — light to light, roll-ons from low speed, launches — then the window we have described is one you are actually in, and the reasoning should at least make sense now, whether or not you buy anything.
And regardless of where you land on the openings: go and look at the foam in your airbox.
If you have a technical question about any of the above, or you want to push back on the reasoning, write to info@shopprojectgamma.com and an engineer will answer you.
