So I have a K&N cone filter intake and a y-pipe on the max now and am thinking of getting a high flow cat converter from custommaxima. Thing is I'm driving her cross country to cali at the end of summer and am looking to get the best possible mpg on this trip. Havent had time to test the mpg I'm getting now since I've been away at college and now busy with work.

So was wondering what your say on this is...does this combo give you better gas mileage than stock? My gut is that since this combo is making the engine more powerful, the mpg suffers. Am I right? Should I wait til I get out to cali then get a high flow cat converter? Would getting a good muffler help or hinder things?

Thanks y'all

 

I used to get like avg of 33ish mpg. Yes I mean avg as in I would get anywhere between 30-38. With just a catback and shortram style intake. After I put on my Y-pipe and hiflo cat I am getting like 25-30 MPG. Also though, I put 1 step colder spark plugs on about the same time I did the Y and cat. So not sure if that has an effect or not.

 

Your gas mileage wont decrease unless your going WOT. If anything it might even improve.

 

As long as you keep the same driving habits, then your gas mileage should improve.

But I find it hard to keep my foot off the pedal after a new mod

 

Ha, i find it hard to keep my foot off the pedal at all times. I have CAI, y-pipe and cat-back, i drive hard and get about 20mpg mainly city driving. Im sure my milage would be way better if i drove like gramma, but I just can't.

Is 38 mpg even possible?

 

I wouldn't get a high flow cat unless your current one is bad, and even if it were bad, I would go OEM. Heard stories about aftermarket cats going to ****.

 

I heard that too. I have a y-pipe, catback and stock cat. And get like 20mpg, but my low mpg is due to other things.

 

I got a random technologies cat for about a yr and a half or so and i can't tell you if it's better. My flex pipe was cooked, so i put on a stillen y-pipe and got the cat at the same time. I felt a power increase for sure and I am still happy with the power it gives(no mods after that). I heard that high flow cats are the same as having an oem one, but when I got it, i actually thought it was more like a straight pipe...performance wise, but legal. I say, if you have to buy a catalytic convertor, get a high flow one. They're about the same price, maybe even less then oem and they should have an edge over oem. I'm hard on the gas pedal so, my mpg are pretty shiiityy on both cars(95 auto modded and 99 5spd stock). Also my friend has a 92 caddy fleetwood brougham with a 350 and drives only city and all he did is take out the cat and he gets more mileage/tank then me, but he also takes 25 liters more then i do. So the point being, complete exhaust and cone filter should give you better mileage/gallon, but we don;t drive civics either

 

With a freer flowing exhaust, and at cruise, you should see better mpg. I would also ditch the hi-flow cat unless yours is broken.

 

sorry bro, but i think getting 30-38 on average gas mileage on a max is just not possible. 25-30 maybe, more like 28 at the most. i get 25 on average and thats driving the speed limit and no WOT. about 22 with WOT

 

Ok good to know, i guess i'll just leave the regular cat on, it seems to be working fine...would getting a new muffler make sense? If so what do you guys suggest for a good tailpipe at a good price?

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

are these ebay mufflers a good buy u think?

 

don't get anything from ebay...it's a fart can. It's not even authetic Nismo or else it would have been advertised as nismo and not HKS. i don't know the brand, might be good, but i won't trust it. I say cattman or greddy sp2...even a flowmaster 40 series if the rest is stock or else no

 

Greddy sp2 ftw, worth the $500 if u ask me.

 

I wonder about the 30+ mpg's people report too. How in the world do they get that? Even on the interstate? 30 mpg would get you 480 out of 16 gallons, which would still be just before the light comes on in my car.

 

how do cattman and greddy sp2 differ, soundwise and performancewise? is it worth getting a full cat-back system vs. just a muffler?

on a side note, it might sound crazy but i'm worried about getting a large expensive and noticeable muffler like the greddy sp2 b/c of theft...my buddy who i go to school with got his big *** $500 muffler jacked right off his WRX in our campus resident parking lot. that means im leaning towards the more subtle looking cattman muffler right now. then again if you can convince me otherwise that getting a greddy is better than cattman and worth the risk im making it out to be, by all means...

 

bizzzzzump

 

Some people have fitment issues with the greddy sp2, in that it seems to hang down to low. The cattman, I think looks good, but it is pricey. There was a group buy on a meagan exhaust system. Do not know much about it, but it looked pretty good.

 

i have never seen above 25 mpg, 28-30 sounds alright on highway

 

oh also what about an unorthodox underdrive pulley? my gut is that it would release stress on the car making it peform better when im driving it cross country and overall? can anyone tell me their experience with these udp's?

 

I am pretty sure the 4th gens could do 30+ MPG highway. My 2nd gen automatic did about 30MPG (30.9278 MPG to be exact) on a 105 miles total round trip with 80% or so highway driving(driving like a grandma). I did about 20% city driving and a few instances of WOT and traffic. And I did all this with a leaky #3 injector. The main way I know is that I filled the car up after the trip to see my MPG and I filled up with exactly 3.395 gallons(till gas tank spilled some gas out).

 

I agree 100%, there is no way I could drive slow enough to get 38 mpg...but if you can more power to you i guess

 

With a y-pipe, no cat and straight thru exhaust I'm getting about 25 mpg on average.