Sloppy has a Cattman CAI on the 1997 I30t. Unless its just my heavy foot (I like the growl), I think my mileage may have dropped 1-2 mpg (based on 3 fill-ups using the same 94 octane gasoline from Shell Oil.

Question: If a CAI rams colder, more dense air into the throttle body, doesn't the car's ECU compensate and add more fuel? How does the computer controlled fuel system work anyway? Please delete if this is a repost. Thanks. -Sloppy

Fixed: And it's normal.

At 50% (not sure but hi throttle setting) the ECU has a set map it uses, regardless of O2 sensor input, so that would negate the effects of the metered air(dense or not), since the map its running in is open loop (pre-set)

You're probably using more gas b/c you want to hear the intake more so you step on the throttle a lil' bit more.

Wow , that was a no brainer.

Is your I30t and auto or 5 speed? Auto's don't take well to aftermarket intakes.

They do if you keep the stock intake resonator. That's the key.

Open-loop starts at 40% throttle and around 3k RPM.


And the ECU does take cooler air into consideration since the two primary inputs at open-loop are the CPS (POS) for RPM and MAF voltage. Cooler air will remove more heat from the MAF heater element and the ECU will have to add more voltage to compensate. This translates into the ECU seeing more air coming in, and adding more fuel.

My I30t is a 1997 year with auto transmission.

Please excuse my ignorance but could you please tell me which part the stock resonator is? Description or picture would help. I am assuming it is the plastic, rectangular-shaped piece that I removed when installing the Cattman CAI. Can someone confirm? Thanks. -Sloppy

Thank you Nismology. That is a very good explanation. -Sloppy

That's the one. Reinstall it and you'll restore your throttle response and low-end punch to stock while still retaining the advantages of a true CAI. That's the best combination to me.

Not trying to be a complete doofus, should I install the stock resonator in the stock postion (post MAF sensor that is)? Imay need to shorten one or more of the Cattman CAI kits rubber hoses for a good fit. Sound like the right approach Nismo? _Sloppy

The stock location is before the MAF.

Throttle body->resonator->MAF->piping->filter

Sounds good to me.

Yep...just looked in the FSM. Thanks for pointing that out. I'll probably make the modification today. I'll try to post a before and after picture in the next few days. I really appreciate your help. -Sloppy

Nismo - With the stock resonator, how did you hook the intake temperature sensor back up?

My Cattman CAI has the port for the intake temperature sensor on the piece of tubing that I just removed (the piece that replaced the resonator in the first place). I can't find a good mounting location. Do I just tneed to extend the wiring 6-7 inches and drill an appropriately sized hole in the metal tubing that leads into the MAF?

It just doesn't look like the sensor can easily go into the flex tubing between the throttle body and resonator or between the resonator and the MAF. I guess one option might be to drill a hole in the OEM tube section where the MAF sensor resides but I do not want to disrupt the air flow with the temperature sensing element. Anyone have any advice? Thanks. Sloppy

it can take teh ECU up to 400 miles to fully adjust

also dose the stock intake resonator really make a big diff on autos?
I took mine out, what is the advantage

Put it back in. ... ....

Well...I ran three (3) 18-gallon tanks of Shell 94 octane premium at 405 miles per tank (see original post). 1215 miles total. Safe to say it isn't the ECU

"That's the one. Reinstall it and you'll restore your throttle response and low-end punch to stock while still retaining the advantages of a true CAI. That's the best combination to me." by Nismology