HKS mushroom filter damaging to the engine?
 

Hey guys, I'm a first time poster and literally just got an 86 last week.

The car came with HKS racing intake with the orange mushroom filter. After browsing some of the forums, I realised it wasn't the best intake out there especially in terms of hp gains, but some of the guys in the Supra forums were talking about the green ones being outright dangerous (link: https://www.supraforums.com/threads/...-truth.440717/).

I know I gotta replace the filter often so the foam doesn't fall apart and stuff up my engine, but I'm really concerned about it not filtering very well and sucking in particles that could be damaging to the engine.

Has anyone heard anything about this? Is it worth spending more money to replace it or should I just focus on maintenance?

Side note: I don't really care about the power as I'm not gonna spend a few hundred for +3hp when I can just get a tune.

I could see them being not so good at filtering. If it fell apart and got sucked into the motor, it probably wouldn't actually hurt anything... Probably. If you're worried, just get a KN filter that fits in it's place. Cost you about 50$. You can go to their website and sort by sizes to find one that will work. Take that part number to Google/Amazon.

Supra guys are running big turbos with big suction and an impeller. Not really the same thing as what you're working with

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Best & cheapest way imho would be to put back stock air box (if you or previous owner still has it) with stock or aftermarket filter for it. As more expensive route i'd consider TRD or Grimmspeed intake. I'd ignore all the other options that bring more cons/issues/headaches then actual gains, including OP's HKS one.

Agreed. Stock, TRD, and Grimmspeed should be the only options you're looking at for an NA car. Every other option has significant downsides, be it HP loss, filtration issues, or general headaches. The stock box is very well optimized and very hard to improve upon.

I've heard bad things about the mushroom filters since the late 2000s. Their filtration in particular is pretty crap IIRC.

I would not take any chances and replace the mushroom filter with one of those 3 options.

Have heard experiences with other owners where chunks of the sponge filter eventually started to crumble and lodged itself in the intake. The owner couldn't find any issues until they finally tore down the intake manifold and found some of the filter media just before the intake valves.

Still shouldn't really hurt anything. The poor filtration would be a bigger issue than the foam itself. The crumbs would just get burnt up in the combustion chamber

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Poor filtration is reason enough to yeet the filter. I don’t want silica wearing my rings/bores, or contaminating my oil.

It was bad though - the car would stumble and hesitate out of nowhere with no CEL. It took the poor owner about a month with different shops to figure out the problem.

100% correct.
I have personally seen this exact thing happen on a BRZ, a NA Miata, a 240sx and a civic.

If it's a small piece you may get away with it. You may not.

Or you can simply purchase a new foam in the correct diameter with more filtration. IIRC there is red, green and yellow. One of them is max suction, maybe go for the least aggressive one.

Genuine HKS filters that aren't exposed to severe overheating and if checked regularly should be safe. Exception if you are driving in dusty conditions regularly. I've had a green with my setup for around 7 years. I think I replaced it once after spilling oil on it accidentally, and otherwise I clean it with dish soap if it looks dirty. I also remove the MAF sensor and spray it clean occasionally. Works great.

Was probably because it was pulling air too easily

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When I first bought my previous car it came with foam mushroom filters on the carbies. Sure enough one disintegrated after a while. The car stumbled and felt down on power for about 100 meters along the road, so I gave it some throttle (I was younger and dumber) and a few seconds later an almighty bang shot out the exhaust accompanied with a huge plume of black smoke. The car drove fine after that and there were no issues in the 8 years following that. That motor was far less sophisticated and tough as nails compared to the FA20 so its comparing apples and oranges I guess.

If it were me I'd swap it out for the stock intake or a quality aftermarket like the grimspeed but there is no hurry. Drive the car as it is and keep an eye out for one of those intakes that suits your budget :cheers: