: gas mileage poor



leosul@verizon.net
07-20-11, 12:38 PM
Can't seem to get beyond 14 around town, 17 on the highway and that's taking it really easy! I have an 06 V with Maggie, headers, stock exhaust, 8" harmonic balancer making 9 lbs boost and only 8000 miles. Spoke with Tom at Hendrix today, he believes it's "in the tune." I dynoed at 482 RWHP and 470 TQ several months ago. I repeatedly see posts with people claiming 20+ MPG and I've never even come close to this MPG. I measure by odometer, not the computer in the car. My air/fuel ratio shows a dotted red line just under 12 on the graph from the dyno, with the car almost perfectly following that line between 2-6.5. My tuner told me "that measurement is a tuner's dream," whatever that means. I gotta be missing something here!

DDS rollin a CTS
07-20-11, 01:43 PM
I vowed when I bought a car with a 6L V8 to never complain about fuel economy. You should do the same.

mberisha
07-20-11, 02:00 PM
dude......482 to the wheels.......enjoy the power.......forget the mileage......

CadzillaTN
07-20-11, 02:07 PM
Can't seem to get beyond 14 around town, 17 on the highway and that's taking it really easy! I have an 06 V with Maggie, headers, stock exhaust, 8" harmonic balancer making 9 lbs boost and only 8000 miles. Spoke with Tom at Hendrix today, he believes it's "in the tune." I dynoed at 482 RWHP and 470 TQ several months ago. I repeatedly see posts with people claiming 20+ MPG and I've never even come close to this MPG. I measure by odometer, not the computer in the car. My air/fuel ratio shows a dotted red line just under 12 on the graph from the dyno, with the car almost perfectly following that line between 2-6.5. My tuner told me "that measurement is a tuner's dream," whatever that means. I gotta be missing something here!


Average or sustained?

14 city is normal. The V is no fun in the city anyway unless it's 3am and you can stretch it's legs..

If you're on the hwy in 6th doing 70 and getting 17 on the instant, there's a hole in your tank.

Try resetting it just before getting on the hwy, then check the average before you turn off and maggie starts suckin fuel.

JimmyH
07-20-11, 02:11 PM
I would say, with your mods, with this weather, if you are averaging 17 hwy, you are not going to do much better. Stock, I was averaging 22-23, and only if it was strictly hwy, and only if I was judicious with the gas.

junoreactor
07-20-11, 02:35 PM
Are your MPG measurements on the AVG or Instantaneous DIC reading?
EDIT: Nevermind, I see you measure by odometer.


I've got a maggie and headers at 502/431 and I get about 25mpg Instantaneous reading on the hilly up and down highways in PA while cruising at 70-80mph. I initially had a problem with MPG like you have and was spending $50 on gas every three days from just 3 trips to work and back on the highway. I noticed that my AFR gauge was showing the car running rich very frequently. There was a point where if you applied the accelerator just a tiny bit too much, the AFR would fly to the rich side sharply. After taking it back to the tuner, he found out he missed something in the tune and I was entering Power Enrichment mode way too early and the car wasn't really using the O2 sensors to trim fuel, just dumping it in at a preset rate. (Or something like that, not too sure on the technical stuff, but you get the gist). Now my milage is drastically improved. Keep in mind if you are cruising on the highway, the maggie has a bypass valve so if you aren't in boost the milage should be ok.

I'd check into having the PE mode checked out by the tuner. It worked for me. Oh, forgot to add my dyno AFR graph was perfect looking just like yours. But real world driving was different.

Skidmarcx
07-20-11, 03:01 PM
It could very well be the tune... I just had mine redone and I gained 4+ MPG on average... not to mention more power... I've got 112 blower, Walbro 255, Kooks 1 7/8", Corsa, Volant. I just took a trip to Cali and averaged 21.2 over the entire 900 miles with tons of enthusiastic driving...

Twitch
07-20-11, 03:24 PM
I'm struggling to stay above the 10mpg mark with the current tank of fuel. That's about 50/50 city/highway. Usually I'm under 10. That's just how it is where i live. But if I'm on a long trip I can get it near 20mpg average. The instant shows 20-22 if I'm cruising about 75 on a flat road. Give it some gas or get to an up hill and it drops to the low teens.

As stated above, the stock maggie tune gets you into PE (rich) at like 25% throttle.
The flat AFR line on the dyno has nothing to do with your problem. That's at WOT only.

If your tuner used HPTuners, ask him to email you the tune. I can look at it for you. Not that I'm an expert or anything close, but I might be able to spot something obvious.

Like most are saying above, if you do have a problem, it's probably in the tune. But don't expect it to get much better.

Tony

JDB
07-20-11, 03:58 PM
Are your MPG measurements on the AVG or Instantaneous DIC reading?
EDIT: Nevermind, I see you measure by odometer.


I've got a maggie and headers at 502/431 and I get about 25mpg Instantaneous reading on the hilly up and down highways in PA while cruising at 70-80mph. I initially had a problem with MPG like you have and was spending $50 on gas every three days from just 3 trips to work and back on the highway. I noticed that my AFR gauge was showing the car running rich very frequently. There was a point where if you applied the accelerator just a tiny bit too much, the AFR would fly to the rich side sharply. After taking it back to the tuner, he found out he missed something in the tune and I was entering Power Enrichment mode way too early and the car wasn't really using the O2 sensors to trim fuel, just dumping it in at a preset rate. (Or something like that, not too sure on the technical stuff, but you get the gist). Now my milage is drastically improved. Keep in mind if you are cruising on the highway, the maggie has a bypass valve so if you aren't in boost the milage should be ok.

I'd check into having the PE mode checked out by the tuner. It worked for me. Oh, forgot to add my dyno AFR graph was perfect looking just like yours. But real world driving was different.

Where in PA are you? I've only ever seen one other V in the last 15 months. Going to V Day doesn't count.

Who did the tuning?

junoreactor
07-20-11, 04:19 PM
Where in PA are you? I've only ever seen one other V in the last 15 months. Going to V Day doesn't count.

Who did the tuning?

I'm in Lock Haven, right in the center of the state. Between Williamsport and State College (Penn State). I had the car tuned by Mike Kleman from Rapid Motorsports down in Birdsboro/Reading area. He's a great guy and excellent tuner.

OP, if you could get that tune file and have Twitch help you out that would be great. Good luck and keep us updated.

leosul@verizon.net
07-20-11, 11:13 PM
[QUOTE=junoreactor;2659102]Are your MPG measurements on the AVG or Instantaneous DIC reading?
EDIT: Nevermind, I see you measure by odometer.


I've got a maggie and headers at 502/431 and I get about 25mpg Instantaneous reading on the hilly up and down


thanks, I emailed the tuner today (J&M Motorsports, Manchester CT.), haven't heard back yet.
http://www.jandmmotorsports.com/

VChewy04
07-23-11, 02:19 PM
Ok I am officially jealous! Seems like all the maggied guys get better gas mileage than us stock guys. I typically average around 22-23 and I do A LOT of highway driving (work about 30-40 minutes from where I live).

I'm curious if I may also need a tune even though I'm stock I am pushing 92k (sad day). I would like to do a maggie at some point but is it pointless with that kind of mileage? I'll tell you one thing my friends, these cars are not very reliable when you get into daily driving and higher mileage (either that or mine is a fluke).

I don't care how many miles he gets on him, I just can't part with him! :-)

JDB
07-25-11, 04:46 PM
I'm in Lock Haven, right in the center of the state. Between Williamsport and State College (Penn State). I had the car tuned by Mike Kleman from Rapid Motorsports down in Birdsboro/Reading area. He's a great guy and excellent tuner.

You're not far away. I was thinking about driving up to Beaver Springs, since I have a free pass for a street night that I was given for signing up as a member of the Keystone Garage Club. I'm not a 1/4 mile guy (I like turns.), but it would be interesting to see times and trap speeds.

Seems like people like Mikey at Rapid Motorsports, since a quick internet search found his info on a Corvette forum after someone had a cam and tune done there.

Do you know anything about Don's Performance Corner in Harrisburg? (I think they moved to a better shop in Hershey area.)

junoreactor
07-25-11, 08:35 PM
You're not far away. I was thinking about driving up to Beaver Springs, since I have a free pass for a street night that I was given for signing up as a member of the Keystone Garage Club. I'm not a 1/4 mile guy (I like turns.), but it would be interesting to see times and trap speeds.

Seems like people like Mikey at Rapid Motorsports, since a quick internet search found his info on a Corvette forum after someone had a cam and tune done there.

Do you know anything about Don's Performance Corner in Harrisburg? (I think they moved to a better shop in Hershey area.)

No, I've not heard anything about Don's Performance Corner. Mikey though, tunes tons of Corvettes from Phoenix Performance.

OP, any update from the tuner? I'm going to be calculating my AVG MPG by odometer here for the next week. I'll post up my results then.

JDB
07-26-11, 08:13 AM
No, I've not heard anything about Don's Performance Corner. Mikey though, tunes tons of Corvettes from Phoenix Performance.

OP, any update from the tuner? I'm going to be calculating my AVG MPG by odometer here for the next week. I'll post up my results then.

Wow, small world. When I was living in the Philly area, I happen to run into the guys at Phoenix..back when I was doing Time Trials/Attacks with my heavily mod'ed Audi A4. If Mikey is tuning for them, he must be one of the best. They turn out some front runners in SCCA.