I'll be putting on my Jethot Lts / no cats, on Thursay and I was wondering if I'll be getting better gas mileage or worse?

 

i say better! motor isnt having to work as hard to push the exhaust out and is able to pull in more air therefore making it more efficient.

 

actually when you first drive the car for a while you will get crappy gas mileage cause you will not want to keep your foot out of it!

 

I was pretty sure that was going to happen, cause the way I drive anyway.

 

im not saying your gonna get better or worse, but how does pulling more air through and engine make it more effiecient? for every 14.7 parts of air you pull through the motor you are theoretically supposed to have one part of fuel to go with it. the way i look at this matter (which isnt correct in the real world) is that it takes a certain amount of energe (horsepower) to move your car down the road. if you are making more power at cruising rpm due to a modification (lts), then you shouldnt have to press the pedal down as far to make the needed power.

 

i got better but i got a tune at the same time so that might have helped

 

well when you get a good intake filter or buy an intake why does that improve your gas mileage? So your saying if i have a crappy intake itll let less air in which will give me better gas mileage...i think not

 

I think he's getting at the fact that the O2's are suppossed to adjust the a/f ratio accordingly, so more air would cause more fuel to be needed. But if the ecu took care of that properly we wouldnt need to tune our cars....they would do it themselves. I think that from the factory the cars run a little rich, so adding more air (via cai or better filter) the car runs a little more lean so less fuel is used...

And the whole more power less pedal less gas theory, well you wouldn have to push the pedal down as far to get it going, but since everything in vehicles are set up through gears the engine will still be turning the same rpm's at the same speed. And then again if your producing enough power to make a difference, then you're already using more fuel anyways because of the tune used to produce that power.

I was thinkin about this the other day and these are the conclusions i came to.... not sure how accurate that is.

 

Less restriction = more HP and gass mileage. Is it easier to use a coffee stir or a straw to drink with? A tune is need with the LT'S though.

 

Like stated above. Get a dyno tune or send your PCM out to be tuned. I picked up a spare just for this same reason. No waiting

 

Very true. But once you get so much air in there you need a tune to add more gas. Hence people getting bigger injectors with higher hp applications. You usually end up running lean with cai and Lt's so you need the tune to add more fuel which inturn you end up with worse gas mileage (maybe not noticeble but it will drop).

 

I know I need a tune but I'm holding off on that till I build the spair motor I have. The headers have AIR and EGR connections so I'm going to keep those for now and I have O2 sims for the rear O2 sensors. I shouldn't be throwing any codes with that setup right? I'm sure that without a tune I'm not going to see the full gains with Lts but there should be a significant difference right?

 

Oh and I also have a spair PCM so that if I need to I can send it in

 

You don't NEED a tune to run the Lt's, ive been doin it for months with no problems (i've been waitin to get the last parts for my cam swap, then its off to the dyno i go). But to get the best power you will always need a tune, no matter what you do to the engine. Deff. noticed a difference though, car seemed to run smoother than when i bought the thing and top end picks up some.

 

Better gas mileage because there is less restriction against the piston to push the air out the exhaust.

 

never thought of that, could be right but i doubt it would make enough difference to see a change in mpg

 

...if hes ditching the cats wont he loose a couple MPG's?

 

I thought that might make it better cause there's less restriction?

 

cats != gas mileage

he'll just bomb emissions

 

You have a sports car/muscle car mpg are irrelevant unless it's your daily driver.