K&N Typhoon Intake (69-8003TFK) Dimensions & Overview

This thread is about K&N Typhoon dimensions for 2005-09 Legacy GT's since K&N made the piping diameter smaller then OEM MAF housing.

 

I wanted to show the actual dimensions and on my theory on why they went this route. Figured I would raise awareness, so that members that pick them up used wouldn't blame the sellers of selling them a non-Legacy intake (yeah, that's happening to me right now...)

 

Car: 2005-2009 Legacy GT 2.5L Turbo

Part Number: 69-8003TFK

K&N Instruction Manual: 69-8003_Inst.pdf

 

Here is the K&N Typhoon installed in a 2005 Legacy GT:

http://legacygt.com/forums/attachment.php?attachmentid=260647&stc=1&d=1515727760

http://legacygt.com/forums/attachment.php?attachmentid=260648&stc=1&d=1515727760

 

 

OEM Intake

First lest start with OEM Intake's MAF housing.

 

Inner Diameter: 70.18mm

http://legacygt.com/forums/attachment.php?attachmentid=260649&stc=1&d=1515727760

 

Outer Diameter doesn't matter, but incase you need a new MAF to Inlet pipe: OD is 80.69mm

http://legacygt.com/forums/attachment.php?attachmentid=260650&stc=1&d=1515727760

 

 

K&N Typhoon 69-8003

Sorry for the crappy pic, I took this a while back and just found it.

 

Inner Diameter: 65.00mm

http://legacygt.com/forums/attachment.php?attachmentid=260654&stc=1&d=1515727760

 

Outer Diameter: 69.85mm (per K&N Support)

 

 

Why the smaller diameter?

The obvious question is, why would they undersize it? Subaru's MAFs are very sensitive to intake changes and start leaning out. This is not necessarily because of added airflow either, it's mainly because intakes (or modifications to stock intake) change how the air flows through the MAF, which leads to the MAF reading less airflow, when there is actually same if not more airflow. The proper fix is to rescale the MAF scales, but this requires a retune by a professional. To help reduce the requirement for a retune, K&N made the inner diameter smaller, which helps fool the MAF into seeing less airflow.

 

Stock vs 70mm Intake

For comparison sake, here is a graph of a stock intake vs a custom 70mm intake doing a 2nd gear pull. The AFR's were so lean I had to stop the pull short, to make sure I don't destroy my engine with detonation.

http://legacygt.com/forums/attachment.php?attachmentid=260656&stc=1&d=1515729477

 

In short, stop driving the car and get it tuned ASAP. This is dangerously lean! More detailed post about this can be found here.

 

Stock vs Typhoon's 65mm Intake

Now here is the graph of stock intake vs K&N Typhoon. Once again the AFR's did lean out, but nowhere near as much as with the 70mm intake. In a way, K&N's design did actually work, but it still leans out past the 11.1:1 AFR that is usually recommended for TMIC Subarus.

http://legacygt.com/forums/attachment.php?attachmentid=260655&stc=1&d=1515729477

 

In short, you should still get a tune, especially if your not stock. More detailed post can be found here.

 

 

Stock Inlet

I think this another reason as to why K&N chose a 65mm inner diameter pipe for their intake.

 

Stock Inlet's Inner Diameter is only 64.49mm

http://legacygt.com/forums/attachment.php?attachmentid=260651&stc=1&d=1515730889

 

Outer diameter is 71.72mm.

http://legacygt.com/forums/attachment.php?attachmentid=260652&stc=1&d=1515730889

Edited January 12, 2018 by covertrussian

I'm not looking into getting this intake, but thank you for some solid info and data to match.

Thanks for the thorough write up. I take it this means it is a poor choice, yes? A little better with a tune but, overall not good?

Thanks for the thorough write up. I take it this means it is a poor choice, yes? A little better with a tune but, overall not good?

 

The stock intake is designed pretty well, and is fairly highly regarded. Thus aftermarket offerings can sometimes have a hard time "improving on it". I didn't do lab quality power testing on this intake, thus I can't say if there are any real gains. My real world testing didn't show enough improvement/decreases that were above margin of error, but the sound and lack reduced footprint is a benefit that might be sufficient reason enough.

 

Now I personally found the stock intake system (Intake + Inlet) to have a HUGE pressure drop (-48 inH2O). A well designed system should benefit and increase power, in theory, but I haven't measured the pressure drop of the K&N intake to compare. For comparison sake, my custom 3" intake has -25 inH2O pressure drop with stock inlet.

Edited October 18, 2019 by covertrussian