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2020 Onyx
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Depending on who you ask, K&N and similar filters are safe and effective, or they're engine eating goblins.

In reality both are true, depending on the circumstance. Like millions of others, I have used K&N and similar filters (cone and panel) for over a decade, including selling custom intakes using them. I never had a problem, none of my customers ever had a problem. It does offer less restriction than a paper filter.

There's also talk of oil contamination of the MAF - which K&N denies is possible, but there are enough anecdotal accounts of this that I wouldn't dismiss it. MAF cleaning with CRC MAF cleaner is easy in any case, but a dirty MAF can result in leaning out of the engine.

But the biggest potential issue is having more dirt pass through the filter. I've never found my air filters of any kind to be caked with dirt. I drive on clean roads, not behind plumes of dirt. What I find on my air filters are mainly black dust (probably from tire/road particles) and maybe a feather or small leaf.

But I've stopped using K&N style filters because the small gain in horsepower isn't worth the potential risk to ME - for others, it may be worth it. If I were doing autocross or racing I would potentially use them, but not off road with heavy dust loads. I did however remove my carbon filter.

 
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Discussion Starter · #206 ·
Well, based on their product page, the '+30hp' was based on Map5 with E30....


Regarding the cold air intake 30 horsepower gain - I would bet 25 of that is from removing the carbon filter. All of the aftermarket intakes (not drop in) get rid of the carbon filter since they're not using the original housing that contains the pillow shaped non-pleated carbon/charcoal filter.
 

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Well, based on their product page, the '+30hp' was based on Map5 with E30....
Right, Map5 with E30 with a paper filter + carbon filter vs Map5 with E30 with their oiled gauze filter and no carbon filter.
 

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I took out the charcoal filter today and installed a new K&N filter. Firstly I was surprised by how dense the charcoal filter is and I’m wondering how the **** the car can breathe through that thing. Secondly whatever the effects/gains of removing the charcoal filter is on stock boost is magnified when you’re pushing +6psi more boost with the JB4 E30 map. As far as driving impressions, you can hear slightly more the turbo spool and BPV not to the point of being annoying like aftermarket intakes. The car is more responsive with throttle inputs and the turbo spools up way more readily with that restrictive barrier removed. I highly recommend this modification for being cheap, easy, and beneficial!
 

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Update with JB4: Recently I have noticed some behavior from the CVT that I don’t think is concerning, rather an effect of the altered boost curve.

I’ve noticed that the CVT will ‘rev hang’ more often now even when driving conservatively in town. I believe this is a result of increased boost pressures and boost ramping up earlier than the stock tune profile. This also would explain why I mentioned earlier that the car feels much more nimble now as the power band seems to be much broader coupled with the CVT trying to keep my RPMs higher.

Anyone else notice this with their Outback? I am running Map 2 (93+).
Anyone have any more feedback or observations related to this? Doesn’t necessarily sound worrisome, but it would be good to know if this is something that we should expect to see when running the JB4 in maps 2+
 

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Discussion Starter · #213 ·
Update with JB4: Recently I have noticed some behavior from the CVT that I don’t think is concerning, rather an effect of the altered boost curve.

I’ve noticed that the CVT will ‘rev hang’ more often now even when driving conservatively in town. I believe this is a result of increased boost pressures and boost ramping up earlier than the stock tune profile. This also would explain why I mentioned earlier that the car feels much more nimble now as the power band seems to be much broader coupled with the CVT trying to keep my RPMs higher.

Anyone else notice this with their Outback? I am running Map 2 (93+).
I have over 3k mi with my JB4 and it’s been ‘as expected’ for me (pretty great). I’ve said it many times, I have a Wilderness, and it gives me exactly what I was looking for.
@Buru Jenkins ; what were the circumstances when you felt the CVT was ‘hanging up’? Was it actually turbo lag? What was the ambient temp outside? Was this the case after a few hard pulls? Or perhaps heatsoak having just pulled away from slow traffic? You’ll see less than optimal results in those scenarios from what I’ve experienced. When we take a step back and look at it, for a reasonable investment, we’re able to run 30+ hp. And unplug and remove it in a matter 30min for a trip to the dealer. A blown CVT, they’re not going to expect it would come from a JB4, in an OBW. Because they’re known to fail on their own. Now, if you roll in to the dealer with a blown CVT and are have an ETS intercooler, J pipe, full stance as you’ve built a sports wagon, they might be suspect to dig a bit. Thanks my take. I think you have a better chance blowing the CVT towing regularly than a few increased boost spurts.
I did an 800mi road trip a few weeks ago and it was just why I got it. I was at speed and able to whip around semi’s (tractor trailers that is!) etc on the highway with ease. I actually had quite a few more capable cars pull along side of me and give me the while looking at the car like wtf?#?#
It’s fun to have it installed. When it’s below 50F and I throw E30 in and run map4, it’s a blast.
 

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I've had the stock car rev hang on me when quickly jumping on and off the throttle since it's attempting to keep the boost high in expectation of another required burst of power.

I assume the JB4 just makes those conditions easy to happen due to the changes required in order to get the bump in power.
 

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Looks like the cobb dropped for the manual wrx

Cobb told me they haven’t released it for the CVT WRX because they had transmission issues :( if they ever release one for the CVT WRX, the Outback XT should follow soon after
 

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Cobb told me they haven’t released it for the CVT WRX because they had transmission issues :( if they ever release one for the CVT WRX, the Outback XT should follow soon after
Still struggling to understand why Cobb can't figure out the CVT handling more torque issue but the in-line JB4 can magically add horsies/torquies without similarly nuking the rubber band contraption.
 

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Still struggling to understand why Cobb can't figure out the CVT handling more torque issue but the in-line JB4 can magically add horsies/torquies without similarly nuking the rubber band contraption.
The JB4 for the WRX is still in beta and the absence of reported CVT issues is not evidence BMS has figured out the CVT. It could be nothing more than Cobb is more conservative in what they will sell.
 

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Cobb has many years tuning Subaru Turbos with the TR690 so they are acutely aware of potential issues. JB4 is expert but new to the Subaru CVT game - it's still a Beta device. Perhaps Cobb could put one out today as a "beta" to see what happens but I think their internal testing shows them that it's not ready.

It could be that Cobb would later on release a package only when paired with a CVT fluid cooler or some other thing to ensure transmission health.

But aside from fluid overheating there may be other issues.
 
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