I am confused. i have an AWD sedan (already screwed with mileage). installed the Z tube and now i feel like my car idles at higher RPMs and navigation screen/computer has been showing approx 16 mpg opposed to the usual 19mpg. I dont see how theoretically a z tube can add MPG. it adds power, with that shouldnt you always be losing...however i didnt think it would be this bad

i do admit i like to step on it now because the car pulls noticeably harder and sounds great at about 3.5k, however, ever since i installed it, my computer has been showing consistently lower MPG records.

Also, when isstalling, i lost the clamp that goes over that rubber emmissions tube. still havent gotten around to getting some sort of clamp. It seemed like the seal was tight enough as it is. could that be a problem?

does the car have to "relearn"?

 

Make sure all the tubes are sealed, so you don't have a vacuum leak. That may cause weird idle RPMs. As far as lower MPG... you probably just step on the gas more because of the nice sound

 

OP, you say it "seems" like it idles at high RMP... what is the rmp at idle?... Did you move the throttle body plate (even by accident) when you installed the Z tube?...

 

z tube does not add power... you reving your car around 3.5k for the sound is prob the cause for deteriorating mileage

 

^^^ he says e has high idle... if its idling high, the entire rmp range is high - which in all likelihood will result in lower mpg... If he moved the TB plate during install it could be the cause of high idle.

 

im kinda stupid w cars so bear w me, but how would i move the TB plate if its metal and bolted on, can u explain exactly which part is the tb plate, is it where hatch where the air enters the tb?

 

i tightened the 2 clamps as much as possible on each end of the tube. however i lost the clamp for the little emmisions tube, but it seemed like it had a very tight seal around that hose barb/nipple thing, so i kinda just left it.

 

I have not had this problem but this is what I would do.

1. Check to make sure everything is tightened down
2. Find the clamp for the emission tube

Your problem will likely be fixed.

If it is still happening you should search for instructions on resetting the ECU and Throttle Body. A good place to find these are at the end of the instructions for installing a MotorDyne plenum spacer. While you are at it you should probably pick up a 1/2" spacer if you would like more and deeper exhaust sound. MotorDyne has a very nice product.

 

Everything needs a clamp even the little hoses. Go back over what you did
to install the Z-Tube, check everything....and while you're at it disconnect
the negative side of the battery for an hour. With all hoses installed with
clamps you should be back to something like normal. Oh yea, don't let your
brain listen to the new sound coming from under your hood....it's connected
to your right foot....
Gary

 

go to ace hardware or home depot and pick up a metal clamp which gets tightened with a screw.

I lost my clamp, super glue'd slightly the emissions hose on, drove to ace, picked and fixed the clamp on!

 

The TB (throttle body) is the unit that the Z tube connect to (on the plenum side)… when the OEM intake is off the intake side of the throttle body is open – there is a plate just inside the bore of the TB, this plate is what opens and closes with the throttle… the plug behind the TB (near the firewall) is the actuator to control the TB with drive by wire (electronic/computer controlled throttle)… if this plate is accidently moved with the actuator and battery connected it will cause erratic idle – including high idle. It has happened to me and several others…

So if by chance you accidently moved that plate (while removing the OEM or installing the Z-Tube), that could be the cause of your high idle, which will result in lower mpg.

If you are certain you did not touch that plate then none of what I am saying matters.