amazing gas mpg after tune M6 even with 4:10's
 

Using Hptuners adjusted the AFR when the cars at 7% or less TPS% most tuners just do power enrichment mid to high rpm for power

May 14th i took a trip to NJ. This was my first time i got to take a long trip since having the car tuned with hptuners, on cruise control to average my gas mpg. driving up I-77 then I-81 through from NC to southern VA has alot of elevation change so i didn't start my test till northen VA. I refueled at exit 313 on I-81N in VA this part of VA and started my test, i had the car on cruise control 65mph and a reminder i have 4:10 rear gear, my rpm is 1,700.

we have a 16.5 gal fuel tank, the fuel pump takes up some space, with this being said thats roughly 16 gallons of fuel storage. a quater tank would be 4 gallons,half a tank 8 gallons. Once i started getting closer to the half tank mark i ran into truck traffic on I-78 in eastern PA and western NJ but even then ill take the 32.8mpg average because i know that if it wasnt for the traffic and some elevation change that would be a high number.

I also know my cars in very good maintence condition:
*clean wix air filter
*MAF sensor clean
*TB clean
*acdelco iridium plugs & magnecore wires have maybe 20,000 miles
*oil had been recently changed
*tires have alot of tread and were all properly inflated
* car had been recently seafoamed so if that product does work theres shouldnt be any carbon buildup
*lucas fuel treatment had recently been used also if that product works should have no carbon build up
*also at times the big pedal on the right helps make sure no carbon buildup

Side note back in the day when i had 3:42 gears and factory tune best mpg i got was 32mpg on cruise control 65mph at 1,500rpm

at the 3/4 mark, 147.2 /4=36.8mpg

http://i695.photobucket.com/albums/v...yGuyx/gas1.jpg

at the 1/2 mark 262.6/8=32.82mpg

http://i695.photobucket.com/albums/v...yGuyx/gas2.jpg

P.S. if anyone has any thing against the way i did my test feel free to let me know so i can make a change when i make my next trip to NJ in july. By then i do plan to tweak a little more with hptuners and even hook the wideband up.

yeah but you need to keep going because half on the fuel tank is really less than half, it drains down pretty quick after half tank....youll probably end up around 26-28 mpg when its all said and done...either way its excellent gas mileage and a testament to some ls1 goodness.

with this being said when i finally filled up gas near a 1/4 tank left my average when the gas pump clicked was still above 32mpg

that last 1/4 tanks a doozy...but still awesome either way. its not unheard of to get 30 mpg out of these cars. id usually avg 26-28 without any special driving or paying attention to mileage...just good old normal driving with the spirited burst tossed in for good measure :lol:

put the car on cruise control and watch that average go up,no ones right foot is as good as a computer, and NJ has to much traffic to be able to stay on cruise for a long time.

lol ive used cruise once before, didnt like the way it feels without the foot on a pedal....felt naked....like not having a wallet in your ass pocket

that gives me a little bit of faith that my mpg wont be completely in the ****ter.. although i dont do much highway

You can never go off the location of the gauge, you need to fill it up and use the actual gallons at that point. Even then you should really have them stuff the tank since the first little splash will kick off the pump. Regardless, I would expect 30+ out of an M6 car. And 65 is too low with the 6 speed, you best mpg will be 70-75 mph if you can maintain that. My old 93 Indy Pace Car with the A4 and 3.23's got 28 mpg on the highway but that was with the LT1 and a supercharger so it's not a good comparison. A proper tune can make a big difference. My old 93 had an off the shelf SLP chip so I was happy with the overall driveability it had. That was running around 2200-2400 rmp's on highway trips so you can see where you're a little low from the optimum range which is around 2000-2200 rpm's on these engines.

i wouldnt trust that "16.5gal" i've NEVER put more than 13.2 in my tank, even after draining it.(dam diesel mix..)

i can easily pull 340 miles out of a full tank in my SS though

I used to get about 26mpg with my car when I had 3:23 gears, now with my 4:10's, Im gettign about 250 to the tank, It really dropped off. Our heads were poorly design, the ports are just plain horrible.

You can't go off of the location of the gauge. Let's just say they aren't exactly Autometer's finest.

Like Jeff said- fill the tank, drive to where you need to go, fill again. Use the amount of fuel you buy in the second fill as your fuel consumption. That will be a rough estimate.

Jealous am I, thats some amazing stuff!

I dread highway driving.

i get 215 miles with a full tank

I was getting 26mpg on the highway with my TA with a cam, full exhaust and 4.10s. 6 speed also.

Hows that so? higher speed means a higher TPS % higher the tps % the more fuel the fuel injectors are reqeusting

I just recently put 14.1 gals in my car, the check gauge light comes on roughly 2.5-3 gals of fuel left in the tank

factory gm guages aren't the best i know that being that for example the rpm gauge is slow and for your second statement refer to post #3.

You can’t guess off the gauge. My olds intrigue (short star!) gets 210+ miles out of a 1/2 tank and ~360 miles a full tank. The Z is the same way. So that is skewed.

Fill tank, note mileage. Drive. Fill tank, note gallons pumped and mileage. Miles driven/gallons = mpg. Over time you will see the average mileage. It’s the only decent method you can use.

I track the mpg in the daily drivers and watch for drops in mpg. This is how I know winter gas and snow tires both hurt mpg. I reset the trip odometer every fill up. The gas receipt has the gallons on it. I jot the t/o mileage on the receipt and do the math. I got 25.2 out of the olds last tank. All highway I’ve pulled down 28. All local it gets ~19.

True, you will be using more fuel in a given amount of time, but you will also be covering more ground in that amount of time. Every combo will have a sweet spot where it gets the best mileage. For LS1 M6 cars, that spot is typically in the 70-75mph range (roughly 2,000 rpm)

- Justin

Refer to post #3 i also did this i nearly do this every time i fill up my car

Ive done a ton of highway driving and even when i had 3:42 gears on a factory tune my best mpg was closer to 60mph on cruise. Im not your average driver 90% of my driving is on the interstate, i live a 1/4 mile from the interstate and have done the long trip from NC-NJ 10 total times, every time i do testing from when the gas pumps click/ miles i have traveled.

Back when i had 3:42's and factory tune

My gas mpg's went like this

60mph gas mpg = 32
65mph gas mpg =31
70mph gas mpg 30
75mph gas mpg 29
80mph gas mpg 27-28

something aint right, my cav does better at 75(34) then at 65(31), its a 02, z24 2.4L twin cam 5spd manual with 3.92 final gear ratio. it might take more fuel to get to a higher rpm, but to maintane it, it *might* be more but not by much. momentum has alot to do, hell my dads 01 solara (3.0 24 valve, 5spd manual) gets better at 70 then he does at 65 but it drops off after 70

I get 17-19 all city in my A4 with 3.23's

I can't wait to put the 6 speed in and see what I get with 6th and the 3.23's hahah

Im going to toss an orange into here and make this apples vs orange

Heres my friends 98 corvette, a corvette is more aerodynamic and weighs less than a fbody. has an LS6 intake.He has also used Hptuners to tune the AFR below 7% TPS.

http://i695.photobucket.com/albums/v...orvettempg.jpg

Yeah, those things are rarely correct. The only way to tell is keep track and look at a big sample of fill ups.

Sorry bud I didn't get that from this and I didn't see you mention actual gallons vs actual miles, i kept seeing references to the gas gauge.

The C5's mpg calculation is off by at least 4-5mpg. I have verified this through filling the tank and checking against the computer's average mpg reading. Also, one can reset that calculation whenever they want in the C5, and skew the results.

Yeah the fuel gauges are always off, when my tank is full it goes all the way to the skip shift gauge...


On my way back from college (400miles) I had the car stuffed w/ a good amount of weight, filled up to the ceiling from the seats back, and I averaged 28.5 mpg switching cruise on/off.

I did the same trip out there with nothing but myself and a few things and managed 31.x mpg

You should definitely be getting the best mpg around 75mph. With a 6 speed it might even be closer to 80. These engines are most efficient around 2000-2200 rpm's so the 1700 is too low. Never look at the computer estimate, always go off actual miles and the gallons of gas. If you have a non stock size tire for your car and did not correct the speedometer/odometer you need to take the difference into account as well. I log every mile and every gallon of gas ever put into any of my cars. That's the only way to see the real changes from 1 tank to another, weather changes, etc. I'm not surprised you're getting 30+ but you might be able to get a little more with a higher cruise speed. Keep your windows closed as well during those drives, it will make a difference.