Tech Post: Why Intakes Need a Retune

[solidxsnake]

Was this from the K&N Typhoon intake or just drop in filter? Before I thought you meant drop in filter only, but I can see that from a full blown intake.

 

Funny thing is I got to know one of my neighbors. He has a 2008 LGT. He bought it new and installed on day 1 a typhoon type K&N filter. I asked him if he got a tune for it. He did not. He now has probably 150k+ miles on the car and apparently never had any engine issues .

In any case, I told him that he should definitely tune for it despite the fact he never had any issue. I will go see him soon and use my btssm app to pull an LV from his ECU. Very curious to see his learned fuel trims.

 

Just goes to show the ability of the ECU to compensate (at least in closed loop), and further confirms to me the whole mindset of these cars absolutely requiring a tune for every minute change for regular daily driving is just overblown.

[covertrussian]

The problem is most people don't easily drive their cars, most love to beat the piss out of them right after starting it .

 

The dangers with his setup is, we don't know how lean it was outside of closed loop, coupled with running timing meant for lower loads, it's just a recipe for disaster. I know that his learning views were clean, but stock LV's don't have a column for loads above 1.60g/rev, while stock cars tend to go to 2.00-2.25g/rev. That means driving half spiritedly will wipe out those learned values from learning view.

 

Another fun one that I ran into was a local friends car, just about bone stock (muffler deletes) 06 OBXT. The car was showing +15% on all but idle ranges, was ~13:1 AFR at WOT and loved to knock. I had him replace the fuel filter and FPR, that helped a little, but still was badly lean. In the end looking at his logs I saw that he was only hitting ~1.60g/rev at 11psi, replacing the MAF solved that issue (started hitting 2.25g/rev). Previous owner ran K&N drop in filter, so we are thinking oil from it killed the MAF.

[xt2005bonbon]

He has a typhoon type K&N filter. And he's been driving with it for 153k miles . Never done anything to the engine!! Amazing.

[covertrussian]

He has a typhoon type K&N filter. And he's been driving with it for 153k miles . Never done anything to the engine!! Amazing.

 

Alright gonna ask for clarification on this one.

 

Does he have the full blown intake, ala:

http://legacygt.com/forums/attachment.php?attachmentid=257167&stc=1&d=1508942795

 

Just the round K&N Typhoon filter (duct taped to the box)

(no pictures for this one, but my mind is running wild )

 

Or K&N Drop in filter (right most)

http://legacygt.com/forums/attachment.php?attachmentid=252699&stc=1&d=1500431800

[xt2005bonbon]

Alright gonna ask for clarification on this one.

 

Does he have the full blown intake, ala:

http://legacygt.com/forums/attachment.php?attachmentid=257167&stc=1&d=1508942795

 

Just the round K&N Typhoon filter (duct taped to the box)

(no pictures for this one, but my mind is running wild )

 

Or K&N Drop in filter (right most)

http://legacygt.com/forums/attachment.php?attachmentid=252699&stc=1&d=1500431800

 

It is the full blown one. I saw it cause I checked his engine bay for leaks and stuff. So yeah, it's crazy.

[covertrussian]

Well K&N did downsize the piping to make up for the increased airflow, which made for about 5% leaner AFR's, which is within margin of error for ECU to be able to correct and on a stock car & tune, shouldn't be too much leaner then 11.5 AFR.

 

If I had to run an aftermarket intake, it would be the K&N for this reason, it's one of the "safer" ones that I've seen for a stock car. As for power gains from it, that's a different story that I'll cover in the next post.

[covertrussian]

K&N Typhoon Intake Fine Tuned Testing

 

Pulling this from my build thread, figured it would fit in with this thread.

 

I tried to fine tune the K&N Typhoon intake to see what's the max power that I could get out of it. Keep in mind that on a stock tune, the intake might actually give you decent gains, but on a fine tuned car, your just gaining noise and high IAT's.

 

http://legacygt.com/forums/attachment.php?attachmentid=257167&stc=1&d=1508942795

 

The heatshield doesn't seal all that well, causing high IAT's.

http://legacygt.com/forums/attachment.php?attachmentid=257168&stc=1&d=1508942795

 

After a couple minutes of 90F city & parking lot driving my IAT's would hit 160F...

http://legacygt.com/forums/attachment.php?attachmentid=257169&stc=1&d=1508942795

 

Onto what really matters though, does it make more power then stock airbox?

To be fair to each setup, I fine tuned both setups for maximum safe power. Then on a different day I tested one intake, installed the other intake, flashed the fine tuned tune for that setup and did another test. These logs were taken about 1 hour apart.

 

http://legacygt.com/forums/attachment.php?attachmentid=257170&stc=1&d=1508942795

 

Power Gains: K&N Intake made fairly minimal gains, and that's with it running 1/2psi more boost then the stock intake. I think the K&N intake would actually make the promised 15whp gain on a stock tune (since it's filthy rich and not optimized). But on a fine tuned setup, the gains are simply much more negligible.

 

Now this is also with the worse flowing OEM filter (16546AA10A) with 25k miles on it. Newer style better flowing OEM filter (16546AA12A) might actually close the gap more. I didn't learn about the filter differences until after I did these tests, so don't have a good comparison graph for newer filter.

 

AFR: AFR's were richer for the K&N intake, when I fine tuned it the week before, it was tuned to 11.1 AFR, temps got warmer so it got slightly richer unfortunately. I personally don't think there is all that much power to be had from making it slightly leaner.

 

Boost: K&N Typhoon spools slightly faster and runs slightly more boost (I'm on wastegate pressure only with no boost controllers, so it's not tune or anything else at play).

 

IAT: Less then 5*F difference, so shouldn't impact HP comparison all that much.

 

Ignition Timing: K&N Intake wanted 2* less timing, running the same timing as stock intake made it loose power. When I tried to decrease timing by more then 2*, I lost power.

 

Gas Mileage: I only did one city and one highway test, in both tests I lost about 1/2 MPG, but I'm wiling to bet it's really a wash, more importantly MPG didn't increase at all. My detailed post on the MPG side can be found here.

 

Conclusion

With very minimal fine tuned power gains, no MPG gains, and IAT's skyrocking much faster then stock. Besides making cool turbo noises, at my power levels this intake is not worth the drawbacks.

[Perscitus]

Great posts and analysis CovertRussian. I might have a potentially interesting sealed air-box filter for you to test if you're up for it: http://www.bmcairfilters.com/eng/air-intake-systems/ota-oval-trumpet-airbox/14/c2

 

The airbox itself is universal and we'd have to figure out a way to ship to/from, perhaps a Spring 2018 project?

[covertrussian]

Great posts and analysis CovertRussian. I might have a potentially interesting sealed air-box filter for you to test if you're up for it: http://www.bmcairfilters.com/eng/air-intake-systems/ota-oval-trumpet-airbox/14/c2

 

The airbox itself is universal and we'd have to figure out a way to ship to/from, perhaps a Spring 2018 project?

 

Design is interesting, I would be up for trying out, just because I like data .

 

I do wonder about the oval design vs round. Round in theory would flow better and have more volume.

 

What's the filter element made out of? I'm growing real weary of oil based filters for our cars. A local friend had some serious issues with the MAF sensor and car that ran K&N filter most of it's life. After replacing the MAF car was happy, we think the oil from the filters baked on the elements and caused it to read way low, leading to very low MAF voltages.

[Perscitus]

ha thats exactly why I offered it up (takes one to know one I guess).

 

The filter element is actually a cone, inverted at that but still a cone.

Great build quality and fully sealed.

 

Filter media is sadly an oiled mesh design (not my favorite either, much prefer stock or Denso paper elements, Amsoil Ea Nanofiber or AEM dryflow, optionally Donaldson Powercore G2 or Powercore PSD filter elements) but hey its the same Subaru uses on the Nurburgring Challenge 2015 and 2016 STIs and many FIA WRC and BTCC and WTCC teams.

[covertrussian]

The cool thing about this design is it works like an inline filter, which means you can easily route this intake to a fresh air source, or even a ram air setup. But I do wonder about it sucking up water too.

 

I'm also gonna use an Amsoil Ea filter once I get around to rebuilding my intake and airbox. I just wish they had more different sizes, one I got to is pretty long so might be hard to fit.