ChiDiddy

Hey guys,

My car has been getting terrible gas mileage and i need help trying to figure out the issue. It is a DD and equipped with a Whipple HO kit(no GT500 fuel pump, using KB boost a pump, set at 40 amps) on a 3.625 pulley making 419rwhp.

Before my new tune from JDM(email) i was getting about 150 miles to the tank before "50 miles to E" comes on( this is with a custom dyno tune). After the JDM tune, i got 110 miles out of the tank, all street driving, maybe 10 miles on the hwy. this calculates to around 8-9 mpg!!! What makes this even more hard to swallow is that i have 3:31 gears and the gas mileage i achieved above was with BABYING the car off of every red light, trying to get it to shift before 2k rpm.

Another thing to consider which may also effect my MPG, i have the stock Saleen 20s with 315/35/20s in the rear, which are pretty heavy, but i don't think they are heavy enough to make it this bad.

I just changed the spark plugs, so that's not the issue. Next would be changing the fuel filter, Strapping it on a dyno and get the email tune straightened out, probably running too rich.

I can smell fuel every time i drive, so does that mean the car is running very rich? Does the BAP make the car dump more fuel than i need? Does the higher amps i set it at make for worse MPG? Technically at my power level, a KB BP is not even needed.

Could it also be a bad o2?

Any help would be appreciated.

NOTES: 5r55s transmission, which JDM says i should easily be able to achieve 15 mpg on street and 22-25 on hwy....... ESPECIALLY with my low gearing!

ChiDiddy

Just read the codes and 4 were found... :/

P0153 O2 Sensor Circuit Slow Response
P2196 O2 Sensor Signal Stuck Rich
P2197 O2 Sensor Signal Stuck Lean
P2198 O2 Sensor Signal Stuck Rich


Keep in mind i do not have catalytic converters. Could this be why its throwing all these codes?

S197steve

Just an FYI, we're running very similar setups except I have the Saleen... a bad tank of gas and I get 15mpg, most times I get around 18mpg and that's about 70/30 city and highway. My fuel warning doesn't usually come on until 220-230 miles on the tank.

You say you don't have cats, do you have the O2 sensors turned off in your tune?

candymanjl

something is definitely wrong. 100% city and I'm usually around 17mpg and that's with some punching it here and there at least a couple times a day. on the highway at 75mph I get 24mpg. I've got 3.55's on my car so I'm revving a little more than you but not that much. that's on KB's stock tune.

ChiDiddy

wow yalls numbers are killing me.....

Steve, what kind of rwhp are you putting down? Gearing? What about tuning? Auto?

Candy, u have 50rwhp on me and higher gears yet your getting wayyy better mpg than I..... Are you manual or automatic?

BruceH

I drove to the track yesterday, made 11 passes, drove home, had 220 miles on it when I filled up this morning and averaged 18 mpg. I'm making over 500 rwhp.

You need to get that thing on a dyno.

candymanjl

I'm manual and when I'm not flooring it I'm cruising in 5th to help with the mileage. you're probably just running too rich in part throttle. I know that on my tune it's 11.5:1 in full boost and 14.5-15.0:1 in cruising/part throttle.

conejo172

I know you guys all have 8's and mine is a 6 but I at bare minimum get 280 miles per tank, D.C. Area traffic mixed highway/city driving. My best was 420 miles on the tank during a all highway trip, filled up literally just before the gas light came on! I shift around 2500-3000 rpm regular and at least a couple times daily shift around 5,500 rpms when I need a little excitement

ChiDiddy

thanks for input guys.

Cone, theres another factor also. We are all supercharged lol so we are gonna have even less mpg, putting the v8 aside.

Will be getting it on the dyno later this week after finals.

Is it a good indicator of running really rich when i pretty much smell gasoline 75% of the time cruising around?

SirKnightTG

I would say yes. Boozshey said the same thing with his JDM mail order tune. Dumping lots of excess fuel out the engine and hitting the cats destroying them causing a clog, and you know what happened from that.

Good thing you don't have cats.

Get on a dyno fo sho.