Hello all. I just picked up my 99 Civic LX from getting an Ls/vtec swap. It runs okay and everything but my I'm noticing my gas mileage has literally been cut in half. Before my Low Fuel light would come on at 300 miles but now it comes on at 150 miles. I know I'm not going to get the same gas mileage as my y7 but at the same time I know it's not a v8 and I feel like 25mpg is what I should be expecting. Also to note I do have an Edelbrock intake manifold and a lightweight flywheel. Also my exhaust is still stock so I know it's slightly too small for the motor. Any ideas as to what I should look into? Thanks in advance.

 

Are you driving conservatively or are you bamming around with your newfound vtec all over the place?

 

I've been pretty easy on it I've honestly only hit VTEC once it's a 0 mile motor pretty much and I want to break it in with the new clutch before I get crazy

 

is your car backfiring,is your ecu chip or program with something other then just for vtec

 

It does backfire a little and if I'm not mistaken it's just a GSR ecu.

 

Thats not right.. Should have better numbers than that. My bro had a GSR Integra that got 33-34mpg consistantly.

 

Yeah I know something is really messed up with that I'm going to try y8 injectors.

 

The Y8 injectors are the same thing as LS GSR and B16 if i'm not mistaken.

 

Yeah that's what I was told on Clubcivic so hopefully the y7's aren't putting out enough fuel so the computer overcompensates

 

bump cuz i have pretty much the same problem. and i have already done a tuneup. stock gsr ecu. only thing modified it a skunk2 intake and a ebay 4-1 exhaust manifold.

 

I'll let you know how the better injectors do as soon as I can get them put in

 

I feel like something is off being caused by the Intake Manifold. It turned out my MAP sensor wasnt in so I installed it and now it idles at 2100 rpm can will idle at the same time. Here are pics of my setup I feel like a hose might be wrong.

 

You should take it back to whoever you had do the work if sensors are off. But in the first pic you have a vacuum line open which will cause a higher idle (not huge cause its a small fitting). GSR ecu is not the right ecu to use with that intake manifold. You should have that motor tuned so you get the best power out of it. GSR ecu runs a secondary butterfly system which you dont have anymore because of the intake manifold. Take it back to whoever did the work is my best advise i could give you.