i had my vortex header, new downpipe, magnaflow high flow cat and exhaust installed today, and as i expected the car feels much more powerful, however:

1. i had a cracked cat on the stock system a few months ago, the new cat makes the same buzzing noise the cracked stock one made under any kind of acceleration.

2. on the highway my fuel economy has dropped by 5-6 mpg
on the service road it has increased by slightly???

isnt a full exhaust supposed to increase fuel economy?


opinions??

anyone?

 

im taking a wild shot at this but if you installed a 3 inch exhaust and dont have enough power to push it, that may be why you are losing gas milage. you have no back pressure for our superchargers which need it. i believe your losing torque which means you have to push the peddle a little further down in order to speed up causing you to lose mpg. just a shot in the dark as i dont know what size exhaust your running

 

Magnaflow isn't 3" so that wouldn't be the problem. Are you having more fun with the car? If you're taking advantage of that extra power it's going to burn more gas.

 

to answer the first question its a 2.5 and i wasnt putting my foot down whatsoever, i was cruising at 65 mph, on cruise control, while i did that i reset my mpg meter, it read 23... under half throttle my mpg goes down to 5

 

see my post in JBP section.

 

Holy ****. Down to 5!?!?!? I hope you mean it went down BY 5. Cause if it went down to 5 while you're chilin in cruise control at 65mph you shouldn't be driving that **** around.

 

Look at that header you have on.

 

 

OUR SUPERCHARGERS DO NOT WORK OFF OF BACKPRESSURE.

SEARCH FOR EXHAUST VELOCITY.

Rediefined...

and im sorry dude but that is the craziest thing i have ever heard. Even if he had a 3" exhaust, that would have NOTHING to do with it, because that scenario is just wild....

a 3" exhaust doesnt make you push the pedal down further... because of power loss... or for that matter in any way...

 

more like 3/4 throttle, i can floor it in the winter, no traction.... but i reset the mpg, give it a go and under 3/4 it says 5.x it stayes between that and 7 heavy acceleration... the shop has to do a check up next week, its standard for them to inspect after 500 kms. my engine check light also went on, but i assume thats bewcause the engine si breathing better

 

There are no DTC codes thrown when an engine "breathes" better. O2 sensors probably not installed correctly if at all.

 

will that effect my gas economy also?

 

i'm gonna guess that youre just playin with the car more since you got it installed and thats whats eaating up gas. i was on the kansas turnpike last nighht about midnight-1am coming to topeka. and i was cruisin at 80 in 5th and every now and then stepped on it(in 5th) and got up past 100. i think i hit 110 atleast 5 times, and 120 once. and 100 countless times

 

read the post at the top, i was putting my foot down on occasions, but, i put the car in a 65 cruise and reset the mpg meter, and it showed 23 over 10 miles, without me touching the accelerator once

 

Considering he replaced his downpipe, headers, and CAT... thers no doubt he has a check engine light...

You only need 1 o2 sensor installed, and thats the one on the front... the rear one doesnt need to be installed.

 

uh, unless you reflashed the pcm to get rid of the p0420, you need the second o2 sensor installed. previous owner got rid of the p0420 on my car, however when i built my exhaust and left the 2nd o2 sensor unhooked (even tried just hanging it outside the exhaust) it set heater circuit codes.

if you did all this with no tuning, id guess the code is p0420- low cat efficiency, because of the highflow cat. however get it looked at.

 

Well.. thats true...

i didnt say you wouldnt get a code.. but... the car still runs.

 

so your seriously telling me that our roots type supercharger doesnt require some back pressure?
seems you dont know as much as you think you do. you lose power if you put on to big of an exhaust, if you dont think thats true i hope you go put a 4 inch exhaust on your car lmao

 

If he isn't, I am.

 

could it be that since it is flowing a lot better the computer is giving it more fuel to make up for the extra air?

 

explain yourself please


if you dont have any back pressure there goes your low end torque.............

 

The only reason backpressure can cause changes in torque is because of the changes in A/F ratio CAUSED by backpressure. Less backpressure will equate to a leaner burn. When tuned for properly, less backpressure with equal EGV will always produce some gain whether it's noticeable or not. There is no physical advantage to having more backpressure ever unless your fuel/ignition system does not permit. I can explain it in far more detail if you'd like there is a lot of evidence of people losing tq due to huge decreases in backpressure, but it's not specifically because of that, but because of what that can cause. If your fuel system is adjusted accordingly, which it should unless you have a major change in back pressure, then it will be more efficient.

Unless he was running a catless setup or something, a loss in backpressure would likely not be the cause of his problems.

 

stop thinking backpressure, it doesnt make torque. scavaging makes torqe. look up what exhaust scavaning is, its the basis of why we put a header on a car. velocity is very important in scavaging. when you go to a large exhaust you lose velocity, and you end up with little scavaging. i could write pages on this stuff, but i wont cause only 1 or 2 people will understand it and its a waste of my time.

 

That's exactly what im saying. You can decrease back pressure without decreasing egv. better flow doesn't necessarily mean less low end torque. Especially when you have positive pressure on the intake side.

It depends on valvetrain components and others what kind of effect this will have because scavaging occurs during overlap mostly. At the same time, an n/a engine benefits much more from scavaging than a forced induction application. With the positive pressure on the intake side of things when under boost, there is no need for nor benefit to scavaging.

 

Damn do you guys think i lost tq ? Here are my mods.

tvs supercharger
20 psi
cti header
cti 3 inch catless dp
cti 3 inch catback
79 lb injectors
cai
do you think the exhust is to much?