mg drop off with exhaust???

Abjonesiii · January 11, 2014

I can't help it I am a sucker for a mean set of pipes coming out the back of a truck. Sooo I had my guy at the local shop (who does really good work btw) drop the stock exhaust off and hook up a Flowmaster 40 series to dual lines exiting straight out the back. 3" lines i believe.

Weird thing is mpg seems to have dropped. I was getting 14'ish around town (lot of stop lights here) and around 19.5 hwy. Now i am getting 12'ish in town and 17'ish hwy?

Anyone got a clue what happened??

Thanks

SLESierra · January 11, 2014

maybe more foot to listen to the exhaust?

Abjonesiii · January 11, 2014

maybe more foot to listen to the exhaust?

haha well yes the first tank i new would vanish because i was playing with it but now even being intentionally easy on the throttle I can't get the mpg back to were it was.

bigdeer1 · January 11, 2014

Di/do? That's the same set up I had installed. When u can hear the v8 sing you'll never get the mpg u had... Especially a truck that u wouldn't notice running.

mike94silverado · January 11, 2014

maybe more foot to listen to the exhaust?

I'm guilty of this lol

Abjonesiii · January 11, 2014

Di/do? That's the same set up I had installed. When u can hear the v8 sing you'll never get the mpg u had... Especially a truck that u wouldn't notice running.

bigdeer1 how do you like the 40 series? I had it on my last silverado but was really nervous about putting it on this one because so many people were saying it would drone awful in V4 but honestly I haven't noticed it.

bigdeer1 · January 12, 2014

Coming from an 06 Sierra with straight duals no mufflers I like it honestly... It's got nice tone to it which is what I was looking for. Wish it could be alittle louder WOT.. It honestly seems to get quieter when pressing the gas threw some of the gears like 2nd to 3rd.

BUT- the v4 drone I could do without.. It gets annoying but I'm getting used to it. I removed everything besides the cats on the stock exhaust. I didn't keep the resonator or the valve.

To sum it all up. Yes I do enjoy it... But for 275$ I would have left it stock.. Just my .2$

TxTruckMan · January 13, 2014

Some people will say I'm wrong, but from what I've been told, the OEMs tune the intakes and exhaust for max fuel economy (and sound of course). Any changes to the intake or exhaust will most likely result in worse fuel economy. If there were gains to be had from those two components, the OEMs would be all over it. They're looking to save tenths of MPGs any way they can.

TJay74 · January 14, 2014

Black03yukon that is about as far off base as possible in regards to OEM stuff. They have to tune for NVH and dB levels that have to meet federal and state requirements. Along with that now you have buyers that complain about vehicles being too loud, so in order to market a vehicle you make sure it is pleasing to your general market and then let the rest go thru the aftermarket to change certain aspects of the vehicle.

With that I have noticed no change in mileage other than due to winter gas and colder temps.

thewhitestallion · January 14, 2014

flowmasters aka chokemasters will rob you of mpg. I had one on my gmt 800 I went from a dynomax to the chokemaster then back to the dynomax b/c the chokemaster took the gas mileage away and to be honest magnaflow/dynomax or really any mufflers sound just as good if not better than any of the flowmaster series mufflers.

Jon A · January 14, 2014

There's nothing "balanced" about the exhaust in that way. Like every factory exhaust it's way more restrictive than you'd want for best power or efficiency due to many other considerations.

If one wanted to "tune" the exhaust for better mileage, you'd start out with a set of long tube headers. The increased VE and torque at low RPM would allow it to cruise more efficiently and require fewer downshifts on slight grades, etc.

fondupot · January 14, 2014

Keep your foot out of the throttle! haha

mzodarg · January 14, 2014

When I had the the Magnaflow installed, the temp dropped down in the low teens for a high, that and I love the way it sounds. I assumed my mileage drop was due in part to the weather and of course my heavier foot. All that being said, now that it's warmer out (for now) my mileage is back up form 13.9, to 16.7 in town. Oh and I'm accustom to hearing the truck so it's no big deal and my foot is lighter.

Mike

TxTruckMan · January 14, 2014

Black03yukon that is about as far off base as possible in regards to OEM stuff. They have to tune for NVH and dB levels that have to meet federal and state requirements. Along with that now you have buyers that complain about vehicles being too loud, so in order to market a vehicle you make sure it is pleasing to your general market and then let the rest go thru the aftermarket to change certain aspects of the vehicle.

With that I have noticed no change in mileage other than due to winter gas and colder temps.

There's nothing "balanced" about the exhaust in that way. Like every factory exhaust it's way more restrictive than you'd want for best power or efficiency due to many other considerations.

If one wanted to "tune" the exhaust for better mileage, you'd start out with a set of long tube headers. The increased VE and torque at low RPM would allow it to cruise more efficiently and require fewer downshifts on slight grades, etc.

I've read dozens of articles and interviews with OEM engineers regarding Fuel Efficiency. All OEMs struggle for gains of tenths of a MPG. TENTHS. They leave no stone unturned. Exhaust and Intake are tuned for FE and sound from the OEMs. You may be able to alter and achieve similar FE results, but you will not be able to mod and tune to achieve better MPG results. I'm talking normal driving, not high-RPM driving.

What's cheaper for OEMs to add to a vehicle? CAI and "Long tube headers" or AFM, DOD, FlexFuel, Hybrid systems, turbos, Aluminum components, active grill shutters, start/stop, etc? If there was anything left to be gained from a $50 intake and $200 exhaist, they'd surely take that first over these other MUCH more costly systems.

mzodarg · January 14, 2014

I've read dozens of articles and interviews with OEM engineers regarding Fuel Efficiency. All OEMs struggle for gains of tenths of a MPG. TENTHS. They leave no stone unturned. Exhaust and Intake are tuned for FE and sound from the OEMs. You may be able to alter and achieve similar FE results, but you will not be able to mod and tune to achieve better MPG results. I'm talking normal driving, not high-RPM driving.

What's cheaper for OEMs to add to a vehicle? CAI and "Long tube headers" or AFM, DOD, FlexFuel, Hybrid systems, turbos, Aluminum components, active grill shutters, start/stop, etc? If there was anything left to be gained from a $50 intake and $200 exhaist, they'd surely take that first over these other MUCH more costly systems.

Your theory brief's well. But I respectfully disagree. Initially I did lose mileage, again I have concluded it was due to the weather, auto starts, and putting my foot it in it. Now it's been in the mid 60's, no auto start and my foot has been lighter and my mileage is very comparable to what it was before the Magnaflow.

All the above is only my opinion, yours may differ.

Mike