Warranty Concerns:
Warranty is a legal liability warranty like any other. (I went through a warranty fight with Toyota over my previously mentioned engine) That being said, you have to understand what a warranty claim actually is, and what it isn't.

When someone (a manufacturer, dealer, finance company, etc...) issues a warranty, they are accepting liability for that period of time/distance, accepting that any issues within the warranty coverage areas are either A) not supposed to happen or B) happen infrequently enough that they will be able to cover the cost of the repairs from the warranty charges from others that don't. Legally, it is only A), but practically, it is both.

When something breaks on your car, and it should be covered under warranty, your request for warranty service is legally a request for the warranty issuer (usually the manufacturer) to accept liability for damage/repairs as agreed.

If the warranty issuer accepts liabilty, which is usual, then they reimburse the shop for the costs of repairs. This is true even of dealers. Dealers charge the cost of repairs to Mazda USA, and get reimbursed. They make a lot of money on engine replacements. This is a critical point to keep in mind. The dealers can choose to not even file for warranty coverage (usually due to laziness), or they intentionally or accidentally misrepresent your car and modifications to Mazda USA during the discussion when Mazda is deciding on if they will accept the liability or not.

Moving closer to an answer to your question, sorry, there is some ground work I like to explain out, because I end up there anyway later on with more questions

If a warranty issuer decides they don't want to accept liability, then there is a fight ahead, at some level. Dealers are notorious for making this decision without even asking their parent company. Warranty requests are something of a mark against dealers I think. However, another critical point to recognize is that when a vehicle that is still within warranty period is denied warranty coverage, the warranty issuer has the burden of proof legally. They have to prove that a non-OEM part, a non-approved action, or a lack of required action caused the failure. If your only mod is a short shifter and your visor breaks, they can not possibly prove the link legally, because there isn't any. (Dealers have been known to try crazy stuff like that). If your transmission syncros fail though, well, there is more gray area. Legally, they have to prove the short shifter caused it, but there is enough gray that they might get it by.

Maintenance records is the big one. For all of history of warranties being issued, dealers have asked for maintenance records as proof of service before coverage. However, it isn't actually proof. Records simply close a loophole that they might try to exploit to get out of accepting liability. A vehicle with no service records at all can have an engine failure, and the warranty issues has to prove that a lack of service caused the failure. Legally. Of course getting to that point might still be costly fighting that battle, whether in time, money, and/or stress. They "win" alot of the warranty requests because the owners don't know any better, aren't prepared to fight them, or they are flat out lied to. Talking about all manufacturers here. Mazda is a bit better than most in my opinion, though they are certainly not exempt.


So directly back to your question, keeping all that in your mind, there is no intake or exhaust modification that will directly void your warranty legally. However, there are certainly dealers which can tell you that it will, tell you that it did, or even tell Mazda USA that you have an "illegal" or "not street approved" or "non Mazda" intake component, which could certainly cause them to deny you. And no, most people never hear those conversations. Conversely, there is another dealer I know about that ignores heavy modifications on an 8 that is routinely in for service and tells Mazda USA that the car is stock, because the dealer is intelligent and knows that the mods have nothing to do with the warranty work and introducing them into the conversation would make it harder on the honest customer.

The oil pressure mod is slowly gaining popularity as a reliability increase, however it would almost certainly cause a voided warranty if recognized, since it is a modification to the oil system, and lack of oil lubrication is a big cause of the failures around here, though there is basically zero chance that dealer would be able to detect it. Legally, it would a non-OEM change that the engine "wasn't designed for" and they would legally win that fight. Though practically, it just boosts the oil pressure up to where Mazda did OEM for the Series 2 engine. Rough call there if detected.

Given the history of failure with this engine (though smaller than people think it is), if it got to a legal fight, Mazda has very little chance at winning unless there was something changed about the engine itself (turbo, supercharger, oil, seals, rebuilt, etc...). But you don't want to get to that part. So in the end it comes down to 2 realistic options: 1) Build a relationship with your neighboring dealer, soaking the extra cost of time and money for routine maintenance so you develop that relationship and grease the gears if something warranty pops up, or 2), do everything yourself, and any warranty claims are more casual attempts where you are willing to take it on yourself if denied. I chose option 2. I figure I save more in money over time doing my own work than it would cost me to replace my engine myself, if it comes to that. Though I certainly will make an attempt at warranty coverage first.

Another thing to keep in mind is that dealer techs largely don't know what they are doing. A small few understand that the rotary is different, and very rare few actually know what they are doing and what to look for. 90%+ of Mazda techs don't even know that coils can fail during the life of the car, and there is a very real possibility that a lot of the early engine replacements simply needed new coils, not a new engine. (similar symptoms) With any issue, come here first. The collective knowledge here is far more than any tech at a dealer. (though there is alot of misinformation too, so you have to learn to sort through it and get backup clarification, etc...)

Case in point, my 8 not being back to normal after my cat failure. It got to the point I was having multiple problems that we couldn't figure out here, but it was all pointing towards engine failure (hard start, no start, misfires, low of power, etc...) I brought it a local dealer for a straight compression test, to rule that in or out (compression test is one of the few things you can't do yourself, unless you buy an electronic compression tester designed for a rotary. Standard ones won't give you all the readings you need). The tech I thought was dealing with the car talked to me like I was stupid for a while, claiming all sorts of crap about the cats don't fail and resetting sensors was a "special mazda way", etc... Finally they put it on a lift and start diagnosis. They give me the lowest compression readings I have ever seen on here, a clearly failing vacuum voltage reading, and then claim that there is no replacement needed. Clearly just lazy and don't want to do the work or the paperwork, but didn't charge me, instead charging it under the powertrain warranty. I brought it to another dealer, who then couldn't duplicate the first dealer's readings at all, in fact couldn't find anything wrong outside of a bit of rust on a plug wire and weak/failing starter. Nothing failing that could be covered under warranty, but he felt bad so he only charged me dealer cost on the labor of diagnosis, and nothing more (like 1/10th of what it would have been). Nothing wrong under warranty, nothing to submit, so he had to charge me. So the first dealer wasn't just lazy, they were incompetent as well.


So when you ask if something will or will not void a warranty, it will very rarely be a "yes, that will void it", but that doesn't mean you won't have a fight. Be prepared.