Intake options

[ConR3.6]

Good morning!

 

Against my better judgment, I purchased and installed the Takeda “Pro dry stage 2” intake about 4 months ago. Post-install, I loved the minor sound enhancement and the appeal under the hood, but I soon realized these are really the only benefits.

 

My gas mileage plummeted. I was averaging about ~350 miles to the tank, whereas post-install it dropped down to ~270ish. Still, I said “fine,” as I knew more mods were to come.

 

The drop in MPGs came with low-end torque loss, which is something I’ve always heard is relevant, but wanted to experience myself. The masses were right. If I was at a stop and “floored it,” my car would pick up pretty quick. Post-install, it would shoot up to 4k-5k RPMs and barely move until it caught up.

 

Then I got Raptor headers installed. Instant improvement all around, but the intake effects were still noticeable.

 

Then I got it tuned with ecuTEK by Moto-East (Xero-Limit) and there was a HELL of an improvement across the board. Mike is awesome and has dealt with all of my stupid questions and requests since I’ve been working with him.

 

However, I’m still suffering from about the same MPG loss and some low-end torque issues. The tune helped for sure, but there’s only so much you can do.

 

I’ve come down to two options:

 

-Keep the Takeda intake installed and purchase/install a high-flow MAF. I’ve been reading that there’s been some success here, and if I could draw some benefits from the Takeda intake, that would be great.

 

-Go back to the stock intake (throw a K&N drop-in filter in there), while having the tune and headers installed (which I haven’t experienced, I’m interested in the stock intake + headers + tune, and the difference in power, if any).

 

In either situation, Xero Limit is putting up with my thought process and are nice enough to take a look at the fuel trim and everything regardless of the decision I make, but I’m unsure which way to go, so I’m here for some ideas.

 

So.. thoughts?

[FLlegacy]

Shall we take a WAG as to what model year and trim level you have? I have deduced its a 3.6 from the headers and I will assume it is not a CVT.

 

With that assumption, I would go back to the stock intake and get a non-oiled (not K&N air filter) or just stick with the paper filters. I would also recommend you look at XRT tuning they have a ton of experience with the 3.6 and 5eat tuning. It almost sounds like your trans is slipping from a stop which is a known issue. Take a look at what TimothyB and Humblerumble have done with their 3.6s might give you a lead as to where you want to go.

 

As for the MPGs well more power tends to lead to more smiles/gallon than miles/gallon you may need a driver mod to recoup the lost fuel mileage, it could also be the reduced intake temps are leading the ecu to believe it needs to add more fuel when it doesn't, or it may be it is no longer running on the ragged edge of too lean.

[ConR3.6]

Wow yeah, sorry about that. That’s a massive oversight. 2013 Subaru Legacy 3.6R.

[Sarang]

Everything I've seen on here has indicated that the stock intake is the way to go. After market is not worth the effort and it never works as well as stock.

 

Of course, I haven't changed my intake so that's all hearsay.

[DrD123]

There are quite a few posts where folks have had issues with aftermarket intakes. The Legacy uses a hot wire MAF, which requires that the air flow across the wire be laminar - if you change the upstream stuff (filter, tubing, etc.) you could easily make the flow more turbulent/less laminar, in which case the MAF sensor is going to have issues reporting mass flow properly - that could easily correspond to a reduction in fuel economy (from the car running rich) - I am guessing that's what's going on - perhaps the Legacy intake just doesn't lend itself to a cold air setup?

[nads]

Very few if anyone have found the limit to the stock air box and intake track power wise on the 3.6r. So far the stock "headers" are the largest restriction (followed by the cats) and biggest gain in power with a tune for them.

[Humble Rumble]

Basically what you're experiencing with your MPG drop is generally normal, and through the process of modding, you were bound to experience it anyways. The factory tune for the 3.6R is rather lean, which is where the (admittedly still not great) factory MPG comes from. Adding the Takeda brought an increase of airflow, which your ECU compensates for with an increase in fuel flow, causing your car to run richer, which burns fuel faster. The exact same effect would have been experienced from a tune and the Raptor install, you just did them in a different order. Mine has been like that ever since my XRT tune. Car is a whole different animal to drive, but fuel consumption has suffered. Trade-offs I guess.

 

Don't fret though, a bit richer of a fuel mixture on the 3.6 is actually more healthy for the engine's longevity, but best achieved through a proper tune (like you have at this point), rather than ECU correction from an intake install. As others have said, I'd recommend going back to the stock intake for now, and picking up an AEM dryflow filter. You'll likely see the torque return as well as a bit of mileage too.

 

That said, a new listing has appeared on Raptor's website for a high-flow MAF for the 3.6R, but it appears to be a part still in development. Curious to see where it goes.