I thought M6s were supposed to get better MPG?
10-13-2013, 09:51 PM
#21
I'm going to say don't think of it totally on rpms pay attention to how much your pushing on the pedal. Example 3rd gear with 5% of the pedal being pushed compared to 6th wide open bogging but less rpm isn't going to matter . Rpms and throttle position % is how I look at mileage. Hope that helps
10-14-2013, 11:10 AM
#22
Until you get some clean mpg numbers we have nothing to go on. "1/4 tank" and xxx miles etc are a crap shoot due to gauge inaccuracies
Fill up the car, drive (preferably all highway for as long as you can), fill up and calculate highway mileage...still won't be 100% accurate but it will give you a good idea where you are at
if you mix in much city/ low speed stuff there are so many variables it's hard to gauge whether there is an issue or not, highway mileage is much easier to gauge effectively IMO
You also say the car is untuned which is going to hurt things a good bit too.
Fill up the car, drive (preferably all highway for as long as you can), fill up and calculate highway mileage...still won't be 100% accurate but it will give you a good idea where you are at
if you mix in much city/ low speed stuff there are so many variables it's hard to gauge whether there is an issue or not, highway mileage is much easier to gauge effectively IMO
You also say the car is untuned which is going to hurt things a good bit too.
10-14-2013, 11:23 AM
#23
I'm pretty sure that the most detrimental thing to your mpg right now is that 160 degree thermostat.
The engine is running too cold. The computer expects a 190 degree thermostat, so it runs the car in open loop until it warms up enough to go to closed loop. With a 160 degree stat, it never reaches that temperature, so the computer constantly keeps it in open loop, which is ignoring the O2 sensors and dumping fuel in to richen the mixture, trying to warm up the car.
Get the tune, and make sure it takes the 160 stat into account. Or, just put a standard temp thermostat back in (not sure why so many people go for a 160 degree so often, these aren't old carbed SBCs). I'll bet after you do one of these two your mpg will come back.
The engine is running too cold. The computer expects a 190 degree thermostat, so it runs the car in open loop until it warms up enough to go to closed loop. With a 160 degree stat, it never reaches that temperature, so the computer constantly keeps it in open loop, which is ignoring the O2 sensors and dumping fuel in to richen the mixture, trying to warm up the car.
Get the tune, and make sure it takes the 160 stat into account. Or, just put a standard temp thermostat back in (not sure why so many people go for a 160 degree so often, these aren't old carbed SBCs). I'll bet after you do one of these two your mpg will come back.
11-03-2013, 10:32 PM
#24
TECH Resident
Thread Starter
iTrader: (1)
Join Date: Jul 2012
Location: Miami, FL
Posts: 965
Likes: 0
Received 0 Likes
on
0 Posts
Well I topped off my tank and ran it all the way down to right at the E line. Made it 215 miles. About 60 miles of that was highway. Took 14.2 gallons to fill up. So I divided 215 by 14.2 to get an average of 15.1 MPG... Pretty crappy. And I barely went WOT. Tune coming this week so hopefully I get some significant improvement from it.
11-04-2013, 08:12 AM
#25
Launching!
iTrader: (2)
Join Date: Oct 2013
Location: Miami, FL
Posts: 265
Likes: 0
Received 0 Likes
on
0 Posts
Well I topped off my tank and ran it all the way down to right at the E line. Made it 215 miles. About 60 miles of that was highway. Took 14.2 gallons to fill up. So I divided 215 by 14.2 to get an average of 15.1 MPG... Pretty crappy. And I barely went WOT. Tune coming this week so hopefully I get some significant improvement from it.
now I drive from Kendall and 137 to Doral 12 st and 87 ave everyday, tank will last me the whole week.
What gas do you put in your beast btw?
11-04-2013, 08:17 AM
#26
TECH Resident
Thread Starter
iTrader: (1)
Join Date: Jul 2012
Location: Miami, FL
Posts: 965
Likes: 0
Received 0 Likes
on
0 Posts
you should try some full injector cleaner. I brought my car down from Orlando on a full tank of gas and still had a quarter left when I arrived at my house. but then again it was all highway miles.
now I drive from Kendall and 137 to Doral 12 st and 87 ave everyday, tank will last me the whole week.
What gas do you put in your beast btw?
now I drive from Kendall and 137 to Doral 12 st and 87 ave everyday, tank will last me the whole week.
What gas do you put in your beast btw?
11-04-2013, 02:12 PM
#27
TECH Fanatic
iTrader: (1)
Join Date: Jul 2006
Location: MPLS MN
Posts: 1,215
Likes: 0
Received 0 Likes
on
0 Posts
while a tune is probably the answer , have you done a basic tuneup? plugs , wires, air filter, fuel injector cleaner. you should be getting 20 city & 25 hwy. better with an light foot. ? for other posters / mechanics could he have a clogged cat?
11-04-2013, 06:47 PM
#28
On The Tree
iTrader: (2)
Join Date: Jun 2012
Location: Mason, MI
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
I get 17-19, almost never see highway, and plenty of hooning. On the highway, i get close to 30. My car is a 2000 ta with lt, ory and a bit of a tune, also an m6. If you are getting less, most likely need a tune up, or a tune. Pull a plug and see how it looks. Check all the basic stuff.
11-05-2013, 05:24 PM
#29
Launching!
iTrader: (2)
Join Date: Oct 2013
Location: Miami, FL
Posts: 265
Likes: 0
Received 0 Likes
on
0 Posts
you know what you should do too I am going to do it tomorrow, Clean your Air filter MAF and tb.. I am gonna do that because that can be a reason I got my idle messed up.
11-09-2013, 08:20 PM
#31
TECH Resident
Thread Starter
iTrader: (1)
Join Date: Jul 2012
Location: Miami, FL
Posts: 965
Likes: 0
Received 0 Likes
on
0 Posts
Well I got tuned. Cleaned some stuff and pulled about 17.2 mpg driving more like a grandma than ever on the tank just before the tune. Now with the tune I'm hoping to get a consistent 18.
11-09-2013, 10:28 PM
#33
TECH Resident
Thread Starter
iTrader: (1)
Join Date: Jul 2012
Location: Miami, FL
Posts: 965
Likes: 0
Received 0 Likes
on
0 Posts
Keep in mind this is about 80%ish city driving in Miami with a good bit of stop and go. 18-19mpg seems to be pretty normal/good city mileage for these cars. Sorry but I don't believe that your car with that many mods through an auto with that big of a stall and 4.10s is doing 18mpg around town with little highway time.
11-09-2013, 10:47 PM
#34
TECH Senior Member
iTrader: (96)
Join Date: Aug 2007
Location: Turnin' Wrenches Infractions: 005
Posts: 24,240
Likes: 0
Received 81 Likes
on
72 Posts
I almost spit my coke on my computer!! 
Have you ever actually tuned a car? Do some reading on fuel trims sir.
What temp does the engine go into closed loop? What temp does an engine run with a 160 stat and stock tune? how about with an aftermarket tune? What temp do they run stock? Do you have any factual information to add?
Your car needs a tune up, i.e. maintenance. 15mpg sucks and it ain't because of the headers regardless of what these boneheads try to tell you.
Have you ever actually tuned a car? Do some reading on fuel trims sir.I'm pretty sure that the most detrimental thing to your mpg right now is that 160 degree thermostat.
The engine is running too cold. The computer expects a 190 degree thermostat, so it runs the car in open loop until it warms up enough to go to closed loop. With a 160 degree stat, it never reaches that temperature, so the computer constantly keeps it in open loop, which is ignoring the O2 sensors and dumping fuel in to richen the mixture, trying to warm up the car.
The engine is running too cold. The computer expects a 190 degree thermostat, so it runs the car in open loop until it warms up enough to go to closed loop. With a 160 degree stat, it never reaches that temperature, so the computer constantly keeps it in open loop, which is ignoring the O2 sensors and dumping fuel in to richen the mixture, trying to warm up the car.
Well I topped off my tank and ran it all the way down to right at the E line. Made it 215 miles. About 60 miles of that was highway. Took 14.2 gallons to fill up. So I divided 215 by 14.2 to get an average of 15.1 MPG... Pretty crappy. And I barely went WOT. Tune coming this week so hopefully I get some significant improvement from it.
11-09-2013, 11:21 PM
#35
Otherwise, I would hope you have at least a rough idea of what temp your car runs at stock, unless you've never bothered to look at your gauges
I've "been there done that" with thermostats, operating temps, and tunes, and was offering this info to try to help. Have you?
11-10-2013, 12:38 AM
#36
TECH Senior Member
iTrader: (96)
Join Date: Aug 2007
Location: Turnin' Wrenches Infractions: 005
Posts: 24,240
Likes: 0
Received 81 Likes
on
72 Posts
Are you suggesting I'm lying to him or something?
Otherwise, I would hope you have at least a rough idea of what temp your car runs at stock, unless you've never bothered to look at your gauges
I've "been there done that" with thermostats, operating temps, and tunes, and was offering this info to try to help. Have you?
Otherwise, I would hope you have at least a rough idea of what temp your car runs at stock, unless you've never bothered to look at your gauges
I've "been there done that" with thermostats, operating temps, and tunes, and was offering this info to try to help. Have you?
I know exactly what the answers are to the above questions because I monitor my engine temps 24/7. And no not from "looking at the gauges". 
I'm not suggesting anyone is lying but rather rambling without providing any useful information. My car has a 160 stat are you suggesting my car stays in open loop and the PCM continues to try to "warm the engine up" all the time? That's plain goofy to suggest that.
11-10-2013, 09:14 AM
#37
I almost spit my coke on my computer!! Have you ever actually tuned a car? Do some reading on fuel trims sir.
What temp does the engine go into closed loop? What temp does an engine run with a 160 stat and stock tune? how about with an aftermarket tune? What temp do they run stock? Do you have any factual information to add?
Your car needs a tune up, i.e. maintenance. 15mpg sucks and it ain't because of the headers regardless of what these boneheads try to tell you.
Have you ever actually tuned a car? Do some reading on fuel trims sir.What temp does the engine go into closed loop? What temp does an engine run with a 160 stat and stock tune? how about with an aftermarket tune? What temp do they run stock? Do you have any factual information to add?
Your car needs a tune up, i.e. maintenance. 15mpg sucks and it ain't because of the headers regardless of what these boneheads try to tell you.
First he starts with a cute joke....
Then he issues a straight forward keyboard challenge....
And finally resorts to classless name calling....
all while standing at the top of mount LS1 with his "I have more posts than
you and I used to be a mod" mentality...pontificating to us lesser folk......
We surrender Steve..you win..none of us have anything valid to say on here
and YOU are always right about everything !!!!!!!
11-10-2013, 09:35 AM
#38
I have a valid contribution.
I currently have 160 stat on my car and it used to have colder fan settings. My hpt logs would indicate slower o2 sensor readings and they would fail eventually. The aftermath of slower o2 readings is poor fuel mileage almost immediately.
My options were get rid of the 160 stat or change the fan settings to come on much later temperature. I did the latter. I have the fans come on 185-190ish temp and my o2 sensors aren't sluggish anymore and my fuel mileage improved. It's been 3 years since then and the o2 sensors are still actively switching. On track days I do lower fan settings to compensate with the motor running hotter during lap runs.
I currently have 160 stat on my car and it used to have colder fan settings. My hpt logs would indicate slower o2 sensor readings and they would fail eventually. The aftermath of slower o2 readings is poor fuel mileage almost immediately.
My options were get rid of the 160 stat or change the fan settings to come on much later temperature. I did the latter. I have the fans come on 185-190ish temp and my o2 sensors aren't sluggish anymore and my fuel mileage improved. It's been 3 years since then and the o2 sensors are still actively switching. On track days I do lower fan settings to compensate with the motor running hotter during lap runs.
11-10-2013, 12:30 PM
#39
https://ls1tech.com/forums/dynamomet...tune-take.html
11-10-2013, 05:31 PM
#40
Keep in mind this is about 80%ish city driving in Miami with a good bit of stop and go. 18-19mpg seems to be pretty normal/good city mileage for these cars. Sorry but I don't believe that your car with that many mods through an auto with that big of a stall and 4.10s is doing 18mpg around town with little highway time.