Bigger Intake Common Sense


Sometimes posts are made that a rich with opportunities, here’s one such example:

Data is out there
Data is out there

Post Analysis:

In the last sentence of the post the person states:

its also a bit of common sense bigger parts = more cold air coming in = more power

Mk7 enthusiast

I find it amusing when someone refers to aerodynamics as being common sense. This simplistic bigger-is-better viewpoint ties in nicely with a misleading statement on the EQT website for the Blaze Performance intake.

On the page the company states:

The Blaze Performance Turbo Inlet Flange features a 74mm inside diameter at the neck and tapers down to 56mm to fit perfectly with any stock machined compressor cover.

Equilibrium Tuning

The Blaze turbo inlet flange with a 56 mm inside diameter is larger than the stock compressor inlet ID which is approximately 49 mm. During my first test of the Blaze intake components, I mentioned this difference.

Blaze Performance Adapter Standard Test
Blaze Performance Adapter Standard Test

A sudden constriction like this can create pressure losses, or in the case of flow bench testing at a fixed pressure, a reduction in airflow.

A closer match of piping inside diameters should cause less pressure drop, allowing higher airflow at a fixed pressure differential.

Turbo flange without insert
Turbo flange without insert
Turbo flange with insert
Turbo flange with insert

In the case of the Blaze inlet flange the company had sent me a design file to print an insert for use with their flange.

Blaze Performance Inlet Adapter Insert Model
Blaze Performance Inlet Adapter Insert Model

This insert reduces the diameter at the outlet of the flange so that it matches the diameter of the stock IHI compressor housings.


To find out how much of a difference the flange insert makes, two intake configurations are being tested:

  1. Blaze Performance ATOM V2 intake system with 100 mm turbo inlet hose and turbo adapter
  2. Modified stock GTI airbox with Blaze Performance 76 mm turbo inlet hose and turbo adapter

Modifying the stock GTI airbox entails removing the snow guard, replacing the filter with an aFe Dryflow filter, and opening the front of the duct on the driver’s side.

Both intakes are attached to the flow bench using an adapter that is sized similarly to the turbo compressor inlet of the IHI IS20/IS38 turbochargers.

Two test points will be recorded for each intake, one without the flange insert, and the other with the flange insert.

The intakes are tested at 28″ of H2O.

Test Results:

The modified stock airbox flows 370 CFM without the insert and 382 CFM with the insert.

Modified Stock GTI Intake Insert Test
Modified Stock GTI Intake Insert Test

The ATOM V2 intake flows 378 CFM without the insert and 392 CFM with the insert.

Blaze Performance ATOM V2 Intake Insert Test
Blaze Performance ATOM V2 Intake Insert Test

Comparing these results using a bar chart:

Intake & Insert Comparison
Intake & Insert Comparison

The next tables summarize the airflow changes resulting from the insert (first table), along with the airflow changes resulting from the different air intakes (second table).

Airflow Change Due to InsertATOM V2Modified Stock
Addition of insert+3.7%+3.2%

Both airboxes show airflow increases with the addition of the insert.

The common-sense-based statement by the enthusiast above, “bigger parts = more cold air coming in...” is not supported by these results. With both intakes, reducing the diameter of the turbo flange outlet led to increased airflow.

Airflow Change Due to AirboxWithout InsertWith Insert
Modified Stock -> ATOM V2+2.1%+2.6%

Changing from the Modified Stock airbox to ATOM V2 intake shows airflow gains with and without using the insert.

Notably, the insert makes a greater effect on airflow than changing the rest of the intake system.

Key Point
Following the statement from EQT will result in reduced performance with stock IHI turbochargers compared to using the Blaze Performance insert that reduces the outlet diameter of the flange from 56 mm to more closely match the 49 mm turbocharger compressor housing inlet.


Turning back to the comments made by the enthusiast regarding the existence of evidence that supports the claims EQT is making about the Blaze Performance intake. They state that:

the results and information James At EQT and EQT has is probably based on the European market and people who have been able to access these products before they got to us, EQTs results may not be in and may be pending but the information is out there…

Mk7 Enthusiast

Ah, the ever-hopeful “the information is out there...”

The data is out there… if you only look hard enough!

Starting with “probably” (the hypothesis) and ending the same sentence with the determination that “the information is out there” demonstrates a degree of naivete that is an enabler for companies to get away with making baseless claims – thumbs up and a like for that from James At EQT.

There’s also this bit when it comes to selling a product and “working on” getting data in support of claims later:

The Commission emphasizes that as a matter of law, firms lacking a reasonable basis before an ad is disseminated violate Section 5 of the FTC Act and are subject to prosecution.

Federal Trade Commission


If you plan to use the Blaze Performance intake parts with an IHI turbocharger, or another turbocharger that uses the same size compressor housing inlet, be sure to also get the insert for the turbo flange. Not doing so drops the performance of the intake down to that of a modified stock GTI air intake.