Lower MPG after installing cat delete/mid-pipe ?
 

Hey guys...I'm thinkin about buying an agency power midpipe with dual resonators and installing it to my factory exhaust. Was wondering if you guys have seen a decrease in your fuel economy after doing so ?

But of course. One installs a midpipe to facilitate higher performance which equates to greater fuel consumption. There's no free lunch. ;)

True..makes sense haha. I'm guessin if you just replace the muffler and leave the stock cat on...you wont get a lower mpg ?

Anyone ?

Inconsequential MPG changes from only swapping a Cat-back exhaust (aka muffler). Just an ear of the beholder item in the RX-8's context. Same goes for most intake swaps.

Hey i have a question for anyone who has the Agency Power dual res midpipe.

I just got mine installed today on the stock exhaust. I listened to videos on youtube before I bought and I thought the sound was perfect.

The problem is when I step on the gas around 4k rpm it makes a horrible raspy sound like a shitty honda civic exhaust or like a fart sound. I hate it... Are you guys getting the same thing or is it just my pipe? When I accelerate slowly it doesnt do it so im thinking maybe the mechanic didnt install it properly?

what do you guys think?

ill make a video tonight as well

The "4k rasp" is common. The higher priced midpipes rasp less, or take longer to rasp, but once it develops, it's always at 4k. AP is one of the bigger offenders.

The only midpipe that has been shown to not have the rasp is the BHR, which is still finalizing the development.

shit that sucks... After all the searching I did for a midpipe. Nobody mentioned the 4k rasp. I think I saw one post that said you can barely hear it.

Its too bad though cause I love the deep tone sound it makes but I feel shy to gun it in the streets cause I am ashamed of that sound.

Do you know of any solutions for it? What if I put an exhaust?

The problem is the packing, only the BHR exhaust doesn't have packing. Every other midpipe has some type of packing in it to muffle the sound, and over time, this packing breaks down, melts, etc..., and the rasp appears. Only option is to replace really.

BHR's pipe uses a unique resonator that doesn't block any flow and there isn't anything to break down, melt, etc...

damn i bought it from someone on this forum... He didnt mention it was broken. This thing ended up costing me over 300$ shipped.

It's not 'broken', read more carefully...a new one would eventually do the same thing.... it's just used

Any of you guys ever try a TurboXS midpipe and experienced this "rasp" ? I'm thinking about purchasing a TurboXS catback exhaust with midpipe next week.

The RB Dual Res midpipe doesnt have any rasp either. BHR or RB FTW

What about TurboXS cat-delete race pipes ? Any of you guys have experience with those ? Do they develop a 4K rasp ? Any feedback would be greatly appreciated cuz I'm planning on buying a used one !

Actually that's false. Freeing up restrictions in the intake and exhaust tracts reduces pumping loss. Pumping loss is generated from the engine having to suck air through the intake and push it out the exhaust. If you take the cat out, you get rid of the biggest restriction in the exhaust, so the engine doesn't have to push as hard to get the gas out.


That being said, more than likely you will have your foot down a lot more, which would result in decreased mileage. If you can keep your foot off the pedal though, you should be good.

Hmmmm.......Never really thought of it that way. Good point:ylsuper:. So basically your saying that installing midpipes will actually increase your gas mileage IF the car is driven under normal driving conditions right ? What are your thoughts on high flow cats like the RP supercat or SR motorsports Hi Flow cat ?

Same principle applies. There is some restriction created by the cat material, but I have a feeling that both would produce close enough MPG numbers that it wouldn't really be possible to differentiate.

They don't fit the OEM exhaust, they're designed to mate with the TurboXS catback exhaust.

I know, but my question is if they develop a 4k rasp overtime as well like the AP midpipe ?

i was doing 20mpg pushing it. now after race pipe i do 22mpg constantly. runs smooth. i like not having to put gas as often. i hope this helps.

Just to update, I have the TurboXS with race-pipe I don't notice any "Rasp" through out the whole RPM range. It's extremely loud though.

I'm getting more MPG with this mid-pipe and this 3" exhaust, than I did with the stock exhaust and cat.

and sounds like shit at WOT

Huh? Mine sure doesn't.