OK, you guys are missing something with the CAI.
Air leak after the MAF, possibly part of PCV system?
MAF is reversed with CAI

A CAI does not push in air, thus it can't put too much air into the engine.
What you're stating is like when people say too big a wire will fry things due to too much power getting through.

 

As long as the MAF sensor is in its original housing, installed the right way around and seeing non-turbulent airflow it should work. If not, all bets are off. Is the MAF an original Hyundai part?

There should not be any way to allow the engine to suck in too much air past the original MAF and original throttle body to lean it out beyond the ECU's ability to compensate, leading me to suspect that something is off with the values being reported by the MAF when it's part of your CAI setup. The primary suspect here then would be leakage after the MAF, regardless of whether your mechanic thinks there is or not. Alternatively something could be off with the sensor or air stream; I've read about people getting check engine lights when they attach a pod filter to the MAF housing, as the airflow becomes too turbulent for it to give a clean signal. Or it could have gotten dirty.

 

Thanks to both of you for the replies! It's great to have confirmation that a CAI should not exceed the parameters of the ECU!

MAF sensor is original, and was installed correctly. While I don't have previous experience finding vacuum leaks, I did do my own check before resorting to a mechanic. After a visual inspection did not reveal anything, I made my own smoke machine to blow through the intake, where the PCV hose would usually attach, and blocked off the intake side so the smoke would all go into the system. It looked like there were no leaks to me, if anything maybe it was leaking a tiny bit from the TPS and/or the opposite side of the throttle-body where the cables attach.

BUT there is no problem once I reinstalled the OEM intake. If there were any leaks outside of the intake itself, that would not be the case. Maybe where one of the flexible portions attaches by a large hose clamp... But I did check all those and they were very tight and secure.
My mechanic did tell me a bad MAF was a possibility, until it proved funtional with the stock intake.

As for the turbulence, the filter is not close to the MAF, and the tubing leading up to it is smooth in its travel and has a smooth surface on the inside. I'd imagine it's much less turbulent than the OEM version. Uuugh idk maybe this is what I get for a cheap eBay intake. Perhaps I can go for an expensive one later, but If it's a shot in the dark idk if I want to blow the money on it.
Lmk if you all have any more thoughts.

 

As you said in your post, you can literally supercharge the engine w/o any kind of tune, so there's no chance your CAI is pulling too much air for the ECU.

What's more likely is the way the air is flowing past the MAF sensor. aftermarket CAIs change the way the air flows across the sensor, and cheaper kits often cause problems because of this. More expensive kits will make efforts to make sure the air flows across the MAF similar to factory to avoid upsetting the air stream. Generally speaking, you want a pretty good straight section of pipe before the MAF to allow the air to kinda even out.

You can also try rotating the MAF in the pipe to see if you can find a spot that it likes more. They can be very touchy so it doesn't take much to make differences. The earlier tibs are way more flexible than the later tibs. For example, my 04 tib wouldn't even throw codes for catalyst performance despite the fact I had headers & no cats. meanwhile 07+ tibs tend to throw a fit with as little as a CAI.

 

What year is your chassis? What size engine do you have? What brand and how old is your MAF sensor? What brand and how old are your upstream O2 sensors?

Based on your description I would say your ECU is that of an 05 or newer ECU. More likely an 07/08 car if I am to guess? If not you must have a vacuum leak or a non-OEM MAF sensor giving too low of a reading. The 05/06 ECUs can lean out a little bit with a CAI but the 07/08 will do it more so. For example my 06 would go lean with even a high quality brand like AEM. The tune parameters on the later ECUs started to tighten up leaving little room for error so adding a CAI would sometimes cause your long term fuel trims to drift toward +25% causing a lean condition and a check engine light. Your ECU is always targeting 14.7:1 stoich and can compensate up to +25% on the long term and +32% on the short term for a total of up to +50%. If you had a wideband O2 sensor and AFR kit then you would see you are still 14.7:1 while cruising and idling so it's not really the problem your mechanic is making it out to be.

The_Evenger is correct about how the air flows past the MAF sensor. CAI's change how that air travels past the MAF and it affects accuracy at different RPMs. That's not entirely a bad thing but it does make things difficult from time to time. I've found that clocking the MAF so the square top piece is tilted towards the driver side at 1-2 o'clock helps alleviate this problem to a small degree. It gives me more accurate airflow readings in my opinion. If your MAF harness is still the OEM length you've probably already discovered that you had to clock it toward the passenger side or upsidedown to reach the MAF sensor. Stretching of the MAF harness intermittently as the engine rocks back and forth in the engine bay can cause the MAF signal to cut out or read lower than desired. Simply extend the harness using water tight splices to alleviate that as well so you can clock it in the 1-2 o'clock position. Here's a picture of my dirty engine bay showing the direction I've clocked my MAF:

If I do need a tune, is there some way of doing a cheap and easy A/F ratio only tune that doesn't require an actual reprogramming or replacing of the ECU? Seems like I am seeing mention of the sort in these forums but I can't find it explained anywhere simply enough for a Tune-noobie like myself to understand. I have 0 experience and knowledge with real engine tuning, since I've only done bolt-ons with no engine management issues until now.

Short answer:
No, in most circumstances you don't need a tune. No there is no cheap easy A/F ratio tune. Best cheap solution is to ECU swap with an 04 model with 5WY17 for a 2.7L or 5WY16 for a 2.0 CVVT model.

Long answer:
Yes every modification can benefit from a tune but you should save the tune for after all your modifications have been bolted on. No there is no tutorial for beginners to read and apply a tune for themselves, yet... I did poorly write up a "how-to" that's more of a mad scientists long form notes a few years ago. Have a read if you like but it's a long one and a little outdated here. I intend to clean this up and post an easier to follow how-to with reflashing over OBD2 options as well.

https://chase.cc/blog/chiptuning-the-gk-2-7-ecm/

04 ECUs were highly sought after and there's not many of them left so I've been forced to convert other ECUs from Sonatas, Optimas, Tucsons, Sportages and other similar vehicles so we have access to more used cores. That is an option if you can't find one yourself. I can source an ECU of the 5WY17 or 5wy16 types and convert it to the Tiburon software if needed. I also reflash ECUs for N/A with intake/headers/exhaust for a performance application so if that's something that interests you, send me a private message.

 

Chiptuning the GK 2.7 ECM – Chase

chase.cc

...holy crap that's a good write-up. Answered a lot of questions I'd had on my mind and many I hadn't gotten to yet. You are doing legendary work here.

 

What year is your tiburon? 07+ often have CELs when CAIs are installed. and if everything works out when you put the factory intake back on, well that kinda rules out everything else.

Honestly, cold air intakes do little more than make noise when your naturally aspirated. Only time you start to need to open up the intake is when your getting into F/I or making serious N/A mods that can take advantage of the additional airflow. That would include cams, porting, etc. when N/A.

If it were me, I'd just drop the factory intake back in and forgetaboutit.

 

Honestly, cold air intakes do little more than make noise when your naturally aspirated. Only time you start to need to open up the intake is when your getting into F/I or making serious N/A mods that can take advantage of the additional airflow. That would include cams, porting, etc. when N/A.

If it were me, I'd just drop the factory intake back in and forgetaboutit.

Yeah, that's probably solid advice 🥲 I wasn't planning on a real performance improvement, but it really does help with sound. I might just leave the stock the stock one on for a while but soon enough the engine noise crying to be unleashed will probably get the better of me 😂

 

That makes sense! Thanks for the tip on the MAF rotation. I do have an 07 but maybe a nicer intake and the right rotation will do the trick then 🤞

 

If I do need a tune [...]

Sorry for the long post, any help is much appreciated 🙏

No, you don't need to do anything other than get used to ignoring the Check Engine light. My 2003 is the same way. It's fine.

UPDATE: Oh! Yes, the later ECUs are less forgiving. Sorry.

 

Nah Tibs do fine with no tunes. The FL2 07-08 models have notoriously finicky computers. So you'll likely need to get used to it if you have those years assuming you installed it correctly. Also the arrow ⬅ on the MAF sensor needs to point towards the engine; not away for it to work properly; common mistake.