Poor MPG

Rootus · Sep 28, 2004

Grn92LX said:
Wrong. The 160* stat will NOT effect going into closed loop. Open loop to closed loop is TIME based.

True and false. True that the 160 thermostat will not keep the computer from entering closed loop. False that closed loop is only time based. It *does* depend on ECT, but it's very low -- about 135 if I remember correctly. And of course it also depends on load, the computer will not enter closed loop in a high load situation. And also, a H/C/I 5.0 will miscalculate load, causing open loop to occur much more often. This can be fixed with a good chip or EEC tuning device.

For the guy who suggested measuring with the highway markers -- bad idea, they are very inaccurate in most cases. I've checked using my GPS and found that the markers vary by plus or minus 20%. Use a GPS if you want to verify your speedo reading.

Dave

revhead347 · Sep 28, 2004

Running too cold can hurt your gas mileage, but we don't worry about that in Florida.

Kurt

1105 · Sep 28, 2004

I dont know how cool my car is running because I dont have an aftermarket water temp gauge, but after I took out the A/C condensor, the the needle on the stock gauge (not saying much) went from 1/2 way across to only a 1/4 way across. As far as I know, I'm still running the stock O2 sensors. How exactly do bad O2 sensors cause poor gas mileage? I'm going to turn my FP down to 40psi with the vac line hooked up, and see how many miles I get to a tank then, then might change my O2's out if its still bad. I'm looking for a Tweecer R/T right now to tune it so once I find one, I'll be able to do some more stuff.

Zero Signal · Sep 28, 2004

There's no way the gears could have affected the mileage that much. The temp won't affect it too much as long as it's decently hot and in OL. I run my coolant around 190° (ECT read) and I'm getting about 250-260mi/13gallons and it doesn't change if I run it warmer.

ANyway, I just don't see gears changing it much if at all.

1105 · Sep 28, 2004

Again, not saying much, but the needle sits between the N and O in NORMAL... Never gets hotter than that.

revhead347 · Sep 28, 2004

If you are still running stock 02 sensors, then it's probably time for a switch. When they get old, the cycle slowly, and the car will compensate by conservatively running richer.

Kurt

viperos · Sep 28, 2004

you know, when my car was stock, I was getting about 16mpg on average... now, since the O/R pipe, I can go about 260 before I refuel, or about 21mpg I guess that's just my car though... one of the lucky ones.

OinkAodeOink · Sep 28, 2004

Ide love to have an answer too...

from asking around, posting on this site and others, the real answer is, no one really knows, when it comes to tuning, except the pro's.

hell, im probably getting worse milage then you, ( i dont even bothering calaculating mpg, its that bad)
with an 8.0 a/f ratio at cruise and WOT.

my bumpers covered in black suit! lol

smokediver27 · Sep 28, 2004

mo_dingo said:
If you have 3.73's, and a 23 tooth speedo gear, then for every 100 miles your odometer, you actually only went 95. Which means when you calculate your gas mileage, you need to take 5% off of the mileage on the odometer, then divide it by the amount of fuel used. So you are getting WORSE mileage then you what your odometer is telling you!!! Sorry, just wanted to correct you on that point.
Scott

Hold on now, I'm drinking me some white russians now, so let me think about this I did not change the speedo gear, I used the Electronic SpeedCal by Dallasmustang for the cluster calibration.

My Car
1 Mile = .9 Odometer Miles
10 Miles = 9 Odometer Miles
100 Miles = 90 Odometer Miles
200 Miles = 180 Odometer Miles.

Am I making sense here??? So if i go and get 5 gallons of fuel after driving 100 miles per the odometer, I have attained 20mpg. Problem is, if the odometer reads 100, I have actually covered 110-111 miles , thus 22 mpg? Am I way off here???

Silver85TC · Sep 29, 2004

One more thing to check for those of you who still have the stock air pump/thermactor system....

My car wasn't getting the mpg's I thought it should so I started checking a few things. Plugs and O2's looked like the car was running rich (hence the poor gas mileage). I discovered the diverter valve for the air pump was stuck in the position that allows air to go to the heads!!! The PCM was totally thinking the car was running really lean (therefore adding more fuel to the mixture) because the O2's were seeing so much oxygen in the exhaust!!! Doh!!

I fixed the diverter valve (it should only feed air to the heads for 30 secs or so right after you start the engine) and my gas mileage has improved a ton.
An exhaust leak ahead of the O2's would cause the same problem.

Cheers.

Grn92LX · Sep 29, 2004

HairyCanary said:
True and false. True that the 160 thermostat will not keep the computer from entering closed loop. False that closed loop is only time based. It *does* depend on ECT, but it's very low -- about 135 if I remember correctly. And of course it also depends on load, the computer will not enter closed loop in a high load situation. And also, a H/C/I 5.0 will miscalculate load, causing open loop to occur much more often. This can be fixed with a good chip or EEC tuning device.

Dave

I disagree and even what I posted from fordchip says its only time based.

Mustangless · Sep 29, 2004

my stock car was(is) getting bad gas millage. I am not exactly sure how much but it is just about on empty with 113miles since I filled it up. Ran a test on it and came up with a bad o2 sensor. Changed 1 sensor now I will see if it gets better.

DFG 5OH · Sep 29, 2004

what test would i need to run to check my O2 sensors? Would bad O2 sensors also hurt your performance, or just gas milage?

revhead347 · Sep 29, 2004

Hook a volt gauge to the signal wire. The voltage should cycle quit rapidly at cruise. It should cycle up and down about once a second.

Kurt

94TURBO5 O · Sep 29, 2004

Zach I get the same mileage on my car . I'm hoping to be able to put a conservative tune in the PMS for city driving and see what it will do. 110 was my last full tank @ $30.28

Killercanary · Sep 29, 2004

Guys, I'm at 230miles now on the same tank I posted about earlier and it is just a needle width under 1/4 right now. I did stop and go driving ALL day today. I will get an easy 250 miles on this tank of fuel. My O2 sensors are still stock.

King Cobra 22 · Sep 29, 2004

smokediver27 said:
Hold on now, I'm drinking me some white russians now, so let me think about this I did not change the speedo gear, I used the Electronic SpeedCal by Dallasmustang for the cluster calibration.

My Car
1 Mile = .9 Odometer Miles
10 Miles = 9 Odometer Miles
100 Miles = 90 Odometer Miles
200 Miles = 180 Odometer Miles.

Am I making sense here??? So if i go and get 5 gallons of fuel after driving 100 miles per the odometer, I have attained 20mpg. Problem is, if the odometer reads 100, I have actually covered 110-111 miles , thus 22 mpg? Am I way off here???

I also have a speed cal but with 4:10's.Would I be getting 1 mile = .9 miles etc... on my odometer or would it be different?

Also with the speed cal,how much off is the speedometer?

BTW I get about 17-18 mpg city driving and driving fast and hwy and city I get about 19-20 mpg.Thats with 4:10's and a bunch of other bolt on's.

FlyBy763 · Sep 29, 2004

Holy crap....with my 100% stock car Ive been getting around 190 miles per tank on 100% city driving...Maybe I should start driving like Miss Daisy is in the back?

onebad95 · Sep 29, 2004

I too was getting bad gas milleage after the vortech install until I put a tornado in the inlet tube. Now I am seeing 24 mpg. I can't believe that thing worked so well.

Killercanary · Sep 29, 2004

onebad95 said:
I too was getting bad gas milleage after the vortech install until I put a tornado in the inlet tube. Now I am seeing 24 mpg. I can't believe that thing worked so well.

Poor MPG

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