gas milage after catback install?

[wickedh3]

First time poster, been browsing the site for a few months.

I recently just installed a Bassani catback on my H3. Its the single muffler where the resonator was and splits into dual pipes over the axle.

My gas milage has gone to **** since the install. I regularly got 17-18 mpg with mixed drving. I am now getting 15-16.

I understand about having more power and keeping your foot into it too much, but after careful driving, increasing tire pressure to 38 psi and mostly highway milage, i cannot get the milage back.

Since these vehicles are drive by wire im wondering if something needs to be done in the torque demand tables in order to take advantage of the exhaust and efficeincy.

What are other people experience after installing there catback systems.

[jphh20]

I installed the Billy Boat dual exhaust catback system and experienced a decrease as well. Since I live in CT I was trying to determine if it was the change in season up here being winter and all or the catback. I experienced 15-16 mpg B4 Catback and 14's mpg with Billy Boat. I'm running the 33's with automatic transmission.

[wpage]

Did you folks do anything on the intake side. For example cold air intake or the like?

[jphh20]

I'm stock under the hood.

[wickedh3]

stock under the hood also.

I own my own shop building mustangs and tuning them in NJ. so im very familiar with the ecm stand point. I have a call into diablo to see if theres something that could be going on in the drive by wire tables due to the increase in torque.

I know the reasons for an exhaust to zap fuel, but if you drive "softer" the milage should come back, unless the ecm isnt allowing it.

Anytime you increase torque production at a given rpm fuel requirements go up. So i know thats where the intial fuel lose went...but easier driving should allow it to get back to that area.

All i know is my girl is bummed that her 17-18 is now 15-16. The truck feels great and def has alot more ummpfff, but at a cost of fuel like this? i dunno if its worth it.

[Bro]

WickedH3, you have a PM.

[jah5207]

i put the magna flow on my 065 speed and mileage went up to 16 from 14-15

[richl]

what state do you live in ??????? are they still using oxygenated fuel???( winter blend) if so that alone will cause any vehicle to drop in mileage .......

wait till mid early summer again . and check your mileage i bet it will go up .

winter blends on fuel burn way easier ( gm has a ton of service bulletins on this) . and you mileage will suffer about 10-25% .. i hear this complaint every late fall to early spring ..... mine drops off about late October and don't pick up till the end of march mid April ..on that fuel alone.. but i am a master Ase tech as well as a gm master tech . i don't know a thing .........

at lease that what the wife keeps telling me .............

and don't waste your mula on 93 octane. the computer was not calibrated to run on that exclusive. well cross that bridge when we come to that ....

[wpage]

Originally Posted by jphh20

I'm stock under the hood.

You could try adding a CAI cold air intake mod or one of these ebay available air mods to increase air flow. Do a search for details...
Adding a header increases exhaust backflow. Without complimenting this on the intake side is incomplete.
Do more research to satisfy your own decision.

[wickedh3]

we run e10 all year. Unless they are playing around with the blends.