Long tube headers average miles per gallon

[Ricco]

Just curious what other guys running set up like mine Long tube headers, catted y , corsa extreme, kn cai, bbk tb, and cust tune are averaging , i went with jdm cust tune told 30-40 hp and torque gain with average 12-13 miles per gallon, well my 12 went from 12 , to below 8 !!! Tried reinstalling tune a few times , been thru 3 tanks of 93 octane still no change below 8 and ive been doing speed limit for sometime. So far not worth time and money deff didnt pick up 30hp just worse gas milage .

 

[CoronaRaptor]

I have sw long tubes with catted dual ex, not tuned, factory AB, get average around town 12.6, hwy in the mountains around 17.0 doing the speed limit (60-70).


Hmmm: wonder if you're overdrive is working, when I towed a trailer loaded, I got 9.9 on the hwy to California.

 

[Ricco]

Yea ill check that , i cant figure this out , thanks for that ill get back to ya

 

[MTF]

Without doing any mods to increase air intake like cams or modified heads and valves,
that BBK TB isn't doing you any good with HP and MPG.
Haven't heard one good thing about it for as long as I've been on this forum.

Did you tell JDM that you put one on? I believe they don't like it either.

I can tell you that with my Whipple Supercharger and having 720 +/- HP
I would have to work pretty hard to get to 8 mpg. with all city driving and long remote starts.

You may need to do a Data log with JDM to figure out what's going on.

 

[Ricco]

Thanks bro

 

[B E N]

Do you have any error codes? This sounds like an O2 sensor issue. You shouldn't see any change from headers, maybe a little + if you drive exactly the same way with them installed. They should improve pumping efficiency. Same deal with a tune.

 

[Ricco]

Im showing no codes , been driving like my grandma just to see if any changes lm thinking on pulling tune and drive stock i no ill be throwing codes then but drive easy for day and try reinstalling tune

 

[MTF]

My 2 cents

You need to put the stock Throttle Body back on.
The stock TB has been proven to be more than enough for the stock NA 6.2L
That BBK TB is most likely messing with the AFR and the PCM is dumping fuel.

Messing with removing and reinstalling the Tune isn't going to solve anything.

Keep in mind that it takes 50+ miles of mixed street and highway driving with three 60 mph to 0 to finish the Fuel Trim learning cycle.
And sometimes an 8 hr. shut down period to set O2s to ready for inspection.
And this sometimes can take up to three days.
And up to 300 miles to finish the Transmission learning cycle.

Now back to the headers, what did you do?
Get a Tune with the rear O2s off.....or did it right and get rear O2 spacers and keep the rear O2s on?

 

[B E N]

Any chance your upstream o2 sensors got flipped from bank to bank?

Downstream O2 don't have any effect on fuel trims, they are catalyst efficiency monitoring.

I agree about the throttle body, just a headache for N/A trucks.

Even running long tubes without a tune shouldn't cause the losses you've got, the only thing that changes for tuning long tubes is transport delay and it's minor.



Elephant in the room is vacuum leaks. Make sure all the clamps are tight, grab the cold air and give it a firm wiggle to make sure its solid in there. Make sure there aren't any ports that got left unhooked. Did the BBK come with new O-rings? Remove it and make sure they are in there.

 

[Ricco]

Will do ill check all that thanks for info bro