5 mpg drop after Flowmaster install

[Trumpet]

So the computer tells me I'm getting about 16 around town. But my hand calculations tell me I'm getting around 11-12. Sure wish it was the other way around.

That's ok. My computers says I'm, getting 20mpg, and hand calc says 14mpg on winter gas.

I'd sure like the split the difference.

 

[catrains]

Really? That's interesting, please explain.

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sensors listen for noise then retard timing. not all that complicated , with a scan tool it is shown.

this is part of the engine protection system that reduces detonation .

retarded timing will drop MPG .

as blackworks stated this should not cause this effect , but could cause this effect. also exhaust leaks will do it. that is why I say scan tool to monitor the timing see if its normal range.

 

[alia176]

sensors listen for noise then retard timing. not all that complicated , with a scan tool it is shown.

this is part of the engine protection system that reduces detonation .

retarded timing will drop MPG .

as blackworks stated this should not cause this effect , but could cause this effect. also exhaust leaks will do it. that is why I say scan tool to monitor the timing see if its normal range.

Knock sensors listen for knocking vibrations at a very specific frequency, using piezoelectric sensors. The exhaust tone which is 15' away and much higher frequency is going to do diddly squat to the timing.

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[catrains]

Knock sensors listen for knocking vibrations at a very specific frequency, using piezoelectric sensors The exhaust tone which is 15' away is going to do bubkas to the timing.

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using a scan tool will help figure it out.

I think you should just ignore the MPG issue.

 

[Civiceg94]

If it's droning, you'll want a resonator or a longer muffler. I have a Jetta vr6 that will make your head explode with the amount of done it gets. Nothing ever helped in terms of insulation, etc. It was a stainless cat back though so I didn't want to chop it up.

I've also heard that extending the tail pipe further from the under carriage MIGHT help a little.

What sucks is that i was told it wasnt going to. i just dont know where to put it.

 

[riceandpho]

i would clean the maf sensor, the throttle body and intake box by the fender, then reset the ecu again, pretty much flowmaster muffler is just noise, had one before and that thing just make noise, no performance, lost some low end torque when i went 3 inch pipes. found a borla system for the cheap and swapped it out immediately. big difference.

 

[Raging Canuck]

This might be stupid but would disconnecting the negitive terminal reset the computer and then compensate for the new exhaust.

 

[alia176]

What sucks is that i was told it wasnt going to. i just dont know where to put it.

Don't feel bad, this is a very common thing with aftermarket mufflers. These mufflers are smaller and have little to no sound insulation material inside like the OEMs do. The end result is that they always produce a drone, it's physics. I stuck the OEM resonator back in after installing the Gibson cat back exhaust and it's MUCH better. But, I'm coming out the back, not to the side so I had more room to play with.

 

[Civiceg94]

Don't feel bad, this is a very common thing with aftermarket mufflers. These mufflers are smaller and have little to no sound insulation material inside like the OEMs do. The end result is that they always produce a drone, it's physics. I stuck the OEM resonator back in after installing the Gibson cat back exhaust and it's MUCH better. But, I'm coming out the back, not to the side so I had more room to play with.

So you ended up putting the tip the one that looks like a football that resonator back on ?