Just intalled a Super 40 Flowmaster and i noticed a major fuel consumption. Could it be posible?

The up display tells me im doing 18.8 lts/100km but i just filled the tank and the average was 22,5.

Could it be possible that the computer tells me wrong?

Before the muffler i was doing 20lt/100km in worst driving conditions....

 

if you are looking at one test you might want to do a few more test before jumping to ideas. if you ARE getting less MPG the parts might installed wrong. may be the experts here can help.

 

yes a new exhaust system can affect mpgs for better OR worse (typically worse)

it is more likely that most of the difference is that your driving habits have changed so you can hear the exhaust better than it is the exhaust itself.

also you CANNOT trust the overhead or any other built in fuel economy meter THEY SUCK and can be wrong in eithe direction (high or low). also as stated one tank of gas is not a conclusive test.

 

my trip computer is usually pretty accurate. Last time I did the math it was only off by .1 mpg

 

you got lucky when you checked, that is far from a typical outcome, mine has been dead nuts on but it has also been off by as much as 8 or 9 mpg all numbers that i share with the forum are hand calculated numbers

 

I've never seen mine off more than 1 mpg. It's usually really accurate.

 

I had other cars that were that accurate. Its very rare of this one being so erratic. Maybe in this stations they put a lot more fuel in it.
Driving habits???? Nahhh, this exhaust is too loud, im even thinking of swaping for a 70 series. But it is loud at 1500rpm, in the everytime rev range its too loud. If i drive past 2000rpm you can barely notice it, but then ill go too fast, so i drive with a lot of sound.
Although i am feeling it to be a bit underpowered than before......... Very strange!

 

sorry matt, your the only one in these forums who thinks its accurate


as for the change in power its possible, changing exhaust and intake dont make or eliminate power, they just shift the power band around, changing the exhaust could have shifted the powerband up the rpm range making it feel like its not underpowered off the line.

 

Maybe consider a magnaflow. Mine doesn't start to get loud until you get towards 2000 rpm (except when the engine is cold) and doesn't really open up until around 2500 rpm. It doesn't drone when you're cruising down the highway either. I like that it's kind of understated a bit too, and what I mean by that is it doesn't scream "LOOK AT ME" like some of these people around here running glasspacks on their lifted pickups that are never offroad (I'm on a college campus, so it's douchebag central), but instead it makes a nice rumbling/growling tone down low without being obnoxious, until you step on it.

It's been over 10 years since my Magnaflow was put on so I couldn't tell you exactly how, if at all, it affected fuel economy, but I still average about 14 mpg (12 city, 15-17 highway) in a 5.2 so I don't think it's hurt it.


I guess mine's special then. Besides, even if it wasn't accurate at all (which seems like the case for some) it does have another use, my buddy is jealous because his ferd exploder doesn't have anything like that.

 

Man you getting better millage the my 98' 5.2l. But yes the exhaust will affect your MPG (or where I am from Letters per 100k). A magnaflow exhaust should help it. By opening up the exhaust you have made it easy for your engine to push out the left overs from the combustion. That in turn also help give the engine more power so you HP to weight ratio is a bit better making it less work for your motor to move your 4694+lbs of metal down the road.
So is you have seen your MPG get worst it is either installed wrong or the O2 sensor is damaged. This might sound nuts for a possible cheep fix try unplugging you battery for about 5 min then checking out you MPG. This will allow your computer to reset it self, it's a shot in the dark but might work or worst case you have to reset you clock.