Hi guys I recently installed a set of motordyne ART pipes for my 03 G35 Coupe. And I definitely noticed the gains. And I love it! However my gas mileage has went down a lot! From 18-19mpg to 11.8mpg. Is this normal? I know adding more power means more gas, but is it supposed to be that much? I'm driving my car normally too. Not going red line or juicing it. My existing mods are. Injen CAI, 5/16 motordyne plenum spacer and Skunk2 true duals. Anyone else run into this problem? Do I need to reflash my ecu, get a return or anything like that. Any help would be great thanks in advance.

 

Reset the ecu and go from there. U will definately benifit from the Osiris tune.

 

Try reseting the ecu. But i think its time to get a tune.

 

Not sure if Osiris supports his 03, I know the early 03 sedans still ran a different ECU from the 03.5s and up. OP check that and if you're eligible for the tune you should do it as mentioned before.

 

Thanks for the input guys! I'll try the items mentioned above. I've been hearing a slight hissing sound when my car is idle I'm hoping it might be a simple exhaust leak that's causing this problem.

 

One thing that can cause the decline of your gas mileage is you're listening to the sound of your exhaust. Sure, the ECU reset will help and I'm surprised running ART Pipes you don't have SES error code from running lean. If you can get an Osiris tune, that's one way to gain lots of RWHP. Ear plugs and a tune will help your gas mileage....Gary

 

Sorry quick side question, is an exhaust, plenum spacer and z-tube need a tune? As in will I be running into the same problem as the OP? Or is that just really due to the ART's?

Thanks

 

I never had any problems with the exhaust, plenum and intake when I put them on, well initially I had problems with the intake but the problem went away after a few days. The ART's I dunno yet, but I'll play around with it this weekend and see what happens. A tune isn't really necessary. It's only necessary if you want to bring out the full potential of your bolt ons or in my case if its running to rich/lean.

 

i was running really lean when i had exhaust plenum spacer and z tube and intake... then was super lean with art pipes.. and by the time i finally got my osiris tune, i was consuming oil already get that ish tuned asap.

 

How did you know this? Did you get pinging or any other weird noises? I really want to put these bolt-ons on right now (sitting in my garage) but I don't want to have to get a tune (if I would be running lean enough to do damage to my car over time, car only has 30K miles on it currently and I want to keep it for awhile).

 

it was knocking at above 6000 rpm. went to get it dynoed at church's and the afr was way out of wack. I was also using shell gas , which apparently shawn church of church's automotive was a big no no. but yeah.. most of the mods will lean out the car.. just do it right and put it all on and get a tune.

 

I tightened some exhaust bolts a few weeks ago, it didn't do much. But the bad gas mileage problem seems to have went away now. I think the ECU just needed some time to do some relearning. I'll see if I can find someone who can tune the car here in Calgary, to see if I can squeeze a little bit more power from the mods.

 

So I know everyone obviously recommends Osiris, but that is a ton of money. What is the benefit of an Osiris tune instead of just taking it to a tuner and spending $250 to have it tuned?

 

Its a little bit more than 250... lol

But the benefits are a better running, more responsive engine, no CEL, you get 5 maps that you can switch between using the cruise control buttons, better shifting for autos, etc etc.

 

Nah about every 2 months or so a shop close enough to me runs a special with a tune for $250, that why I was curious to the benefits. Osiris is around $600 right?