3g hemi gas mileage

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5.7 hemi said:
Iam running factory computers. Factory Rams use 1 o2 before the cat and 1 o2 after, so since no cat you use only 1, thats the logic as it was explained to me when I got the harness. The only tuning I have done was a 91 octane, raised the rpm limit, and shift firmness. I took out the 91 octane after figuring out the mpg, but have left the rest, so its basically all stock computers, no aftermarket such as fast, mega squirt, accel etc.
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Ok so if you're running a factory PCM did you have the downstream o2 sensor disabled? If not your running in permanent open loop because it thinks there is something wrong with the catalytic converter so it's in cat protection fueling.
 
Well I drove 74.8 miles, took 5.391 gallons to fill it, and that come out to 13.87 mpg...this is freaking dismal!!!! However, I did throw the 91 octane tune back on and after talking to johnparts, I also put a new o2 sensor on. I will try and get the down stream o2 hooked up, but I dont think it will help much. So now I'm leaning towards changing the center out for a 3.55 instead of the 3.91's, that should help some.
 
DFX 340 Duster said:
My 2007 Charger R/T gets 13+ around town with a normal lead foot. It gets 16-17 when I take it easy and let the MDS take affect.
On the highway it gets up to 25 mpg with the MDS and cruise control engaged for most of the time.
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Same for me with my 2007 charger rt, although I have a fresh air intake and 91 diablo tune, I run only premium and I have gotten as high as 30 mpg running at 60, up to Houghton MI as the speeds are only 55 on the 2 lane highways. can you use a diablo tuner on you car??? you could make some adjustments using that tuner, Diablo will do a custom tune for ya too,
 
well, with an average speed of 160km/h on german Autobahn I measured exactly 13,5 liter per 100km... (happy converting :-D ) 72 Dart, 6.1, 750 Holley, 5speed Toyota Supra Tranny, 3.23 rear
 
If I didn't screw it up that's 18 mpg.

5.7hemi hopefully you figure out what the deal is. I know 5.7dart had posted he was running a little better than 20 with his 5.7 dart and 3.91's with the truck tranny.
 
412 Stroker said:
Same for me with my 2007 charger rt, although I have a fresh air intake and 91 diablo tune, I run only premium and I have gotten as high as 30 mpg running at 60, up to Houghton MI as the speeds are only 55 on the 2 lane highways. can you use a diablo tuner on you car??? you could make some adjustments using that tuner, Diablo will do a custom tune for ya too,
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I just got the car before Christmas. This is good info. I had heard about using a K&N fresh air intake but I hadn't checked into a tuner yet. Horsepower increases also right? Thanks.
 
Buschi340 said:
well, with an average speed of 160km/h on german Autobahn I measured exactly 13,5 liter per 100km... (happy converting :-D ) 72 Dart, 6.1, 750 Holley, 5speed Toyota Supra Tranny, 3.23 rear
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Das ist 17.4 mpg, ja? Ser gut. (umlaut)

Practicing my simple Deutsch from my college days, oh so long ago.
 
Have I not figured the mileage out right??? 74.8 divided by 5.391 equals 13.87,so how has anybody got any different??? Thinking of getting a spun universal cat and running the rear o2 sensor just for ***** and giggles. So far I cant find any company that will sell into Cali.....that is chicken ****!!
 
5.7 hemi said:
Have I not figured the mileage out right??? 74.8 divided by 5.391 equals 13.87,so how has anybody got any different??? Thinking of getting a spun universal cat and running the rear o2 sensor just for ***** and giggles. So far I cant find any company that will sell into Cali.....that is chicken ****!!
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We were figuring out Buschi340's mileage since he posted in liters/kilometers:D
 
5.7 hemi said:
Have I not figured the mileage out right??? 74.8 divided by 5.391 equals 13.87,so how has anybody got any different??? Thinking of getting a spun universal cat and running the rear o2 sensor just for ***** and giggles. So far I cant find any company that will sell into Cali.....that is chicken ****!!
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Do you have a SES(service engine soon) or CEL(check engine light) hooked up? If you are running a stock computer,and no cat,and no 2nd O2 after the cat,you are going to run pig rich. You NEED that 2nd O2,and if you are not going to run a cat then you need this http://www.gtimotorsports.com/product/O2-Sensor-Spacer/Default.aspx?gfid=p653 or something similar to "trick" your ECM.
 
5.7 hemi said:
Have I not figured the mileage out right??? 74.8 divided by 5.391 equals 13.87,so how has anybody got any different??? Thinking of getting a spun universal cat and running the rear o2 sensor just for ***** and giggles. So far I cant find any company that will sell into Cali.....that is chicken ****!!
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5.7 I finally made it through your entire thread on FBBO... Awesome, beautiful car, the grill is sweet...

Sorry about your luck with mpg. Those are depressing numbers for sure, I am gonna run 3.91 without OD, so i am worried about mine for now. Are you sure the converter is locking up? That is all I can think of, it would be interesting what a wideband would show.

BTW, shoot me a PM if your interested, i could give you my address for a CAT, I would forward it to ya...

Joe
 
joeboy said:
5.7 I finally made it through your entire thread on FBBO... Awesome, beautiful car, the grill is sweet...

Sorry about your luck with mpg. Those are depressing numbers for sure, I am gonna run 3.91 without OD, so i am worried about mine for now. Are you sure the converter is locking up? That is all I can think of, it would be interesting what a wideband would show.



I was wondering.the same thing on the gas mileage. I'm running the same gears as Joeboy with a 727 and i was hoping for 17 mpg.
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Blue87D100 said:
Do you have a SES(service engine soon) or CEL(check engine light) hooked up? If you are running a stock computer,and no cat,and no 2nd O2 after the cat,you are going to run pig rich. You NEED that 2nd O2,and if you are not going to run a cat then you need this http://www.gtimotorsports.com/product/O2-Sensor-Spacer/Default.aspx?gfid=p653 or something similar to "trick" your ECM.
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I was under the impression the second O2 sensors are for checking catalyst efficiency only, and the upstream are what determines the fuel trim?
 
It was my understanding that only California cars used four O2 sensors, two before the Cat and two After.

I BELIEVE if you use the factory service tool you can turn off the two sensors after the catalytic converter.

Also If you are looking to find someone to ship a catalytic converter to you in California (I had to order one for a 79 Chevy PU, and couldn't get anyone to ship one to me for a while) Try Amazon, they had EO (executive order) Cats that are California legal. Plus they were pretty competitive on price.

Regards,

Joe Dokes
 
Ok, I thought I was doing some sort of Obama math, lol!
I have the plug in to check for engine codes and the funny thing is, NO codes. I did get some early on, power steering temp is high, battery temp is high, cant fins gauge cluster, stupid stuff that does not pertain to the engine or trans. I checked again just awhile ago, NO codes what so ever.
Joeboy, thanks for the compliment. Doing the grille was fun, long, but fun. The trans shifts into all gears, converter locks up, unlocks when down shifting and I can even take it out of overdrive with a push od the button (hidden in the ash tray). In other words, it hits all gears up and down, sometimes barks the tires from first to second.

You know, I just might try and install a bung and put the rear o2 on, just not sure if it help since no codes with just the upstream o2 hooked up.

Maybe I should step back, look at the "TOY" and just drive the piss out of it while enjoying every minute....decisions decisions.
 
Joe Dukes, the 03 ramsonly used one upstream and one down stream, and usinf factory computers, 1 pcm and 1 tcm, I have evrything hooked up right according to Chris at hotwireauto and Mark at Street and Performance. Hell, I even watched the dvd I got when I bought the wiring harness from Street and Performance last night to make sure I hooked up the o2 right "Just hook up the upstream and tie the other one out of the way", thats word for word.
 
5.7 hemi said:
Joe Dukes, the 03 ramsonly used one upstream and one down stream, and usinf factory computers, 1 pcm and 1 tcm, I have evrything hooked up right according to Chris at hotwireauto and Mark at Street and Performance. Hell, I even watched the dvd I got when I bought the wiring harness from Street and Performance last night to make sure I hooked up the o2 right "Just hook up the upstream and tie the other one out of the way", thats word for word.
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There's your problem, following the directions, nothing ever good comes from that. ;)

I think your decision to drive the piss out of the car is the wisest idea yet.

Regards,

Joe Dokes
 
Stacked360 said:
I was under the impression the second O2 sensors are for checking catalyst efficiency only, and the upstream are what determines the fuel trim?
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While that is the case,when the computer receives no feedback from the downstream sensor, it reads it as lean, and can cause the upstream sensor to overcompensate. I would be interested to see a wideband O2 installed to see what is really going on.
 
Just my $.02, I wouldn't drive the piss out of it running pig-rich like that unless I wanted my rings to wear out prematurely... I agree with Blue87D100 get a wide-band O2 sensor and standalone meter hooked up so you really know what's going on with the A/F ratio.
 
Have you checked your speedometer, if its off it could mess things up a little.
Maybe against a gps would be a good check.
You may be going more miles than you math is figuring.
 
Blue87D100 said:
While that is the case,when the computer receives no feedback from the downstream sensor, it reads it as lean, and can cause the upstream sensor to overcompensate. I would be interested to see a wideband O2 installed to see what is really going on.
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That was my suggestion. I said either run a cat and a down stream or get a simulator for the downstream o2.
 
I got my harness and computer from Hotwire and it uses 2 upstream O2's and no downstream. But I know my ecm has been programmed to ignore them, I wonder if yours has?
 
Can you disable the downstream with a Diablo sport tuner?
 
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