I have a Y-Pipe with dual electric cutouts..... can having them open affect gas mileage

 

I have Bolt ons and if anything I think my gas mileage went up?? I get no less than 260 to a tank with 100% city driving right now. When I drive to and from school its all highway and I get 300+ easy.

 

do u have ur rear 02 sensors still???

 

what kind of maintennance did u do to your car after the mods..like fuel filter ,spark plugs+wires..etc

 

I didn't notice any seat of the pants improvement with my mods until I started tuning it myself so my tune is free . It feels snappier now more then it ever did. I have LS6 intake, QTP LT, QTP ORY, Corsa Catback, and a lid. I never really did deviate from the stock milage though. Long tubes will make you go lean since the cylinder is able to move more air efficently through the exhaust valve which leans out your tune. Also changing anything in your intake without tuning the maf usually will make you run leaner as well. I would guess that would increase your milage minorly. And to put it into perspective you want your "Long Term Fuel Trims" (LTFT) to be with in 5 and -5 (posative = more fuel which means a lean condition). My LTFT's were sometimes tripple that amount and EVERYWHERE was lean on my car. Now that I'm dialing more fuel I can feel how much smoother it is and there is more torque in more areas when cruising. I haven't done WOT tuning yet so I don't know how well that will do until I get my WB installed. I wouldn't tune anything though untill a cam swap or heads are involved, it's just not worth it to spend hundreds on bolt-ons unless you plan on doing nothing further. Only reason I'm tuning is I want to learn how and what to do for a winter heads+cam combo I'm getting.

Thats why I'm sugesting you take a look at your sensors and getting everything else up to speed. I'd replace the plugs and wires at least. I did with mine and it was lower milage then your car and I noticed a difference. Like I said I can get 30+ MPG if I let CC do all the work for me.

 

on highway im getting 30mpg which is over 400 miles to the tank. however my city driving is on average 17mpg. sounds like you got something wrong.

i just have catback exhaust slp lid and msd wires and ngk plugs

 

Makes sense about the plugs and wires.....about tuning would u suggest buying a handheld programmer to tune it because i know pro tuning costs cheddar $$$$$ and that would be a temporary until i drop a cam and heads

 

about the 02 snesors i have a OBD 2 scanner and it doesnt throw me any codes for front 02 sensors just the rear ones that i dont have them hooked on anymore .....i dont even have simulators ..is it possible to blow out your front 02 sensors and not throw a code for it?????

 

I'm pretty sure a handheld isn't going to touch your closed loop/part throttle tables at all. Only way to go is a full tuning suite IMO. It is $$ but HP Tuners was by far the best money I've spent on the car. Now I can make any upgrade I want to the car and know how much time and effort was put into a tune.

It is possible for them to be faulty and not throw a code. They can switch incorrectly but it's not that common for it to happen. I'd just try the plugs, wires, fuel filter, and a can of MAF cleaner to clean out the intake. Probably a total of 70 dollars and see where that gets you.

 

I had a single cutout at one point and definitely noticed a loss of low end torque with it open but more pull at the top end. The LS1 likes a little back pressure and headers definitely reduce that. Add to that the cutout and you might have to push the pedal down more at the same speed on the freeway.

Before the turbo I had Hypertech programmer, lid, Slp loudmouth, Z06 MAF and car was lowered about 1.25" I got 29.98mpg on the way back from vegas (300+) miles. I fiilled up as soon as I got home so I could see how well it did on pure highway. Oh that was with cruise at 75+, with a stint at 90 and at 100 (it was the morning after thanksgiving no one on the highway in the middle of the desert).

After the turbo I average about 20-22mpg with about 70% highway. The closest to all highway trip since the turbo I've gotten 25 mpg but that was with driving around in the town to shop.

I would definitely do the fuel filter, plugs, wires, and check your air filter. The plugs alone will help at lower engine speeds. May want to get a tune to adjust for the headers (they can change your A/F ratio).

Good luck!

 

very well then i'l go for the basic tune for now until i get a hp tuner

 

thanx alot 1987 firechicken and th erets of you guys this will save me $$$