Built and installed a custom intake (shown in picture). For two tanks of gas prior to install I average 26.5 mpg (calculated by car) and 28.2mpg calculated manually.
after install the first tank of gas average 17.5 and 18.6 and the second 17.2 and 17.9.
Is there a problem here??? Or is this what is to be expected from an intake on this car? Going to be removing it and installing the stock box back in to see if it improves.

 

On my 2015 RS9 (w/same Engine as yours) TRD Center Exhaust (RS9) and stock Intake, I average 26.4 mpg (calculated by car) originally.

After my TRD CAI Install I now average 25.2 mpg (calculated by car) But, I Gain Overall 11 whp and 13 tq: https://www.scionlife.com/forums/sci...-232519/page2/

Yes, the TRD CAI is pricey at $365, but you get what you pay for.

Yes, gas mileage will vary depending on your I/H/E.

No one can tell you what to expect from your Intake because it is a Custom Intake. All you can do is put your stock intake back on and see what happens.

 

Thank you very much for the info... I've looked at the TRD CAI, and it surprises me that you get the gains you did. Seems to me it's simply a slightly larger intake tube and snorkel with a K&N filter.
The charcoal filter is still in the box, isn't it? That seems to me to be the biggest issue with our stock intakes.
I just swapped the stock one back in and will go fill it up this afternoon and see what happens.
Thanks again, much appreciated.

 

Just went and read the thread you linked... Very informative. I will strongly consider going that route.
thanks again!

 

Yes, it has the Charcoal Filter uptop. That's why it's C.A.R.B. Legal.

Mine is an Auto Transmission w/CA Emmissions. Tony, the Dyno guy at SVS Dyno was Surprised at the Gain.
He said: "You got all of that, with just an airbox?". He dynos Camaros, Mustangs, and Hemi's all day long.

Hey, C.A.R.B. legal, No CEL codes, 11 whp and 13 tq overall improvement, only lose a 1.2 Mpg.

I'm a Happy Camper
Y.M.M.V.

 

So after replacing the stock air box, filling up and resetting the mpg calculation I am showing 28.3 on the car after half a tank of driving.
So obviously something about this intake does not get along with the car. I've put these Spectre I takes on other cars before and never had an issue.
Looking at ordering the TRD intake next week.
Thanks for the info!!?

 

I don't know anything about your custom intake, but maybe without all those CARB legal filters it's getting alot more air than the stock and TRD intake. So it could be running lean and the o2 sensor where the cats are is telling the ecu that and it's just dumping more fuel to correct the air fuel mix. Just a thought, not sure why else the mpg would be that low and I don't know if the ecu correcting it being lean(possibly) would affect it that much. It's still a 4 cylinder and should get better gas mileage.

 

My MPG went up about 0.5 mpg when I put my intake on. Likely you are just driving it harder because the motor feels a bit more alive. Or there may be an issue with the intake/filter you installed and how it works with the MAF sensor.

 

Glad to hear you were able to sort it out. That's why 3rd party intakes are problematic. Some work fine. Some not so much. It's a gamble.
That's why I recommend the TRD CAI. Yes, it's pricey. There's is a reason for that. It maximizes the performance and it works w/o problems.

Quality is never cheap.

 

I just removed the secondary emissions filter, put a K&N filter in, and called it done. Throttle response improved, gained a little bit out sound (so it's getting more air), and my MPG were not noticeable. Hell, I can still pull 30+ on the interstate. I also have a CNT Racing mid-pipe that adds good sound, deletes the scuba tank (2nd Cat/Res), and improves the overall flow of the exhaust by eliminating the up/down steps of the exhaust sizing. (good for low end torque but restricts top end)



Keep your foot out of it, and you'll be fine. Car's drive by wire anyhow, so it'll never give you full throttle right off the bat like a cable throttle will.