SpeedCrazie

iTrader: (23)

Looking for a new Mid Pipe since I want to replace my cat anyhow was wondering what everyone’s thoughts are? Will the SMB be louder then a resonated mid Pipe? Will a substrate cat still smell like gas? Would the SMB MID Pipe cause my car to shoot flames? Just want to know what to expect if I change out my cat.

arghx

iTrader: (3)

You can't just switch to a midpipe. You need a retune. If you are on stock turbos you need to remove the turbos and port the wastegate.

SpeedCrazie

iTrader: (23)

I run an adaptronic.

arghx

iTrader: (3)

Ok. So are you going to retune it or pay someone? Are you sure your wastegate is sized appropriately to run with a catless exhaust?

just because you have an adaptronic, and adaptronic has some self learning capabilities, doesnt mean you can go catless on a whim.

SpeedCrazie

iTrader: (23)

Hey Brother, appreciate you looking out for me as I can see how the question could come off as somewhat of a newbie type. But I still haven’t got any information regarding my questions. I can definetly have have the car retuned and this particular FD is running a set of BMR’s so all should be well. Just looking to do a couple changes is all.

arghx

iTrader: (3)

Catless will make you shoot flames.
a working active cat will not smell like gas when it is warmed up and functioning. When you say substrate cat, what exactly did you have in mind? Please be more specific.
resonated will be quieter than non resonated but the larger the exhaust the louder it will be.

contact BNR and ask them if the wastegate can support your specific combination of exhaust parts.

TomU

iTrader: (11)

If you are not a newbie, that only leaves jerk and/or ignoramus. If it were me, i would go with newbie

Questions about what is better is meaningless w/o a little context (i.e. what you are running) and what your goals are. For example, if your goal is to have a loud smelly exhaust and blow your engine, than that helps steer people to recommending a mid-pipe

BTW, arghx is probably one of the best tuners on this site. I'm surprised he responded

arghx

iTrader: (3)

Thanks for the kind words. There are certain engine related mods that cause a big step up in complexity and concern from the perspective of safety and driveability.

Taking a good running setup and going catless is one of them. This basically requires you to scrap the boost control tune and can greatly affect the engine in cold weather especially. It pushes the wastegate to the limit as well, even a big external wastegate or a ported wastegate. It's one of the biggest things people do that blow their engines up.

Changing primary injectors is another one. This basically requires you to scrap the entire fuel tune. It throws everything off--idle, tip in fuel, WOT fuel, cruising fuel, everything. It's one of the biggest things people do that messes up their driveability and potentially the engine safety.


There are mods that can be considered less drastic of a change. Changing from one kind of air filter to another is less drastic, or same with one catback to another, unless it's something drastic (straight pipe to stock muffler maybe). Putting larger secondary fuel injectors messes up the tune under high load but it's not going to risk blowing your motor.

So keep in mind what your goals are and what you are changing and what has to be checked and verified. In the case of going catless, all boost control has to be checked over and retuned. Overboost safety needs to be assessed (fuel cut or boost solenoid cut or ignition cut). WOT fueling needs to be adjusted, spark timing might need to be changed, air temperature compensation needs to be considered. You may not even have enough wastegate to safely support it, no matter how well it's tuned. So then you overboost and blow up, or you hit overboost fuel cut every time it's cold out and your performance actually goes down.

How loud it's going to be (Louder.) and how smelly it's going to be (Smelly.) are lesser concerns in the short term. Fall is a dangerous time. People blow a lot of motors when the weather gets colder and the boost climbs.

billyboy

All the SMBs I've seen here have a cat, a metallic one, so should suppress flames - until it stuffs up, something with a resonator only, won't do crap and it will probably burn out the muffler contents pretty quick too. I'm not sure of bolt centres, but the mid-pipe works with the exxy 3.5" downpipe, you might want to check that, if running the usual 75 or 80mm pipe off the turbos!

SpeedCrazie

iTrader: (23)

So I suppose my post may have been a little generalized. However I never asked which is “better” nor what will make my car the fastest or loudest. Nor did I ask how to make my car shoot flames etc etc. Rather I asked a couple simple questions about an item I am unaware about.

Typcailally a a car with a cat would tend to be quieter then one running a resonated mid pipe. However since the 3.5 is larger in diameter and is a metallic substrate I wasn’t sure if that would still be the case. Same goes for other questions regarding smell and flames.

I respect members such as arghx for their knowledge and know how and wanting to help members from making costly mistakes as read above in his previous post.

Narfle

iTrader: (16)

Can you explain your setup? I would not generally recommend removing the cat. If you car is running well, don't change anything.

SMB makes resonated and non-resonated midpipes in varying diameters. 3.5" will generally be louder than 3", and non-resonated will generally be louder than non-resonated. I'd guess 3.5" resonated would be louder than 3" non-resonated. But, there are a lot of other factors.

I don't see many people having much luck with aftermarket cats on rx7's. But, any cat will help with the smell for as long as it survives.

Yes

Smells, noises, and boost creep.

SpeedCrazie

iTrader: (23)

Thank you! Perhaps I’ll just settle for the 3” version and call it a day.

Mods for for this one rebuilt, stock port, BNR’s, intercooler, DP, High Flow Cat,Exhaust and adaptronic, Twin Power nothing too crazy the cat is an older unit, and I have started to smell more fuel during idle which prompted me to look at possiably upgrading it.

DaveW

Where do you smell the fuel? Out the exhaust, or in the engine area? If it's in the engine area, it might be a leaking FPR or injector seal, either of which can lead to a fire if the fuel gets onto the turbos or exhaust.

SpeedCrazie

iTrader: (23)

That was my first thoughts too but all is good shape there.

photoresistor

iTrader: (5)

I have a similar mod-list as you minus the BNR's and actually have had a similar experience over the past couple months with the fuel smell. I have not taken the high-flow cat off but my suspicion is that it is clogged--I've been running this since I bought the car a couple years ago and it has not had a working air pump feeding it (hence my suspicion its clogged). I've recently double checked for fuel leaks in the engine bay and no problems there so not sure what else it could be.

I just put in the newer adaptronic and need to do some tuning on it first (unfortunate how you have to basically start over), but I plan to throw on a mid-pipe from a buddy at some point (with restrictor plate to ease creep) just to see how she does. I've also been looking at the SMB cats as I'd love the increased flow without the fuel smell, however, I need to pass emissions where I'm at so that's probably a no go.. :/ If you end up going with the mid-pipe or SMB cat, keep us updated, would love to hear about it.

DaveW

I've had that occasionally from the gas cap area (even though the cap checks OK when emission checked) when the car is in a hot environment or has been driven hard. And I'm still using the original catalytic converter.

BLUE TII

iTrader: (9)

I bought a used (burnt out) 3" Magnaflow mid pipe first and didn't like the gas smells (though the flames were nice).

So I bought a used SMB 3" catted, resonated mid pipe when one popped up here. No more smells, but no more flames either. It was obviously quieter than the burnt out resonated mid pipe, but a bit louder than the stock cat section which I had used before the burnt out mid pipe.

SMB is very nice quality materials, welds, design and fitment- definitely recommend their exhaust.

Rx7aholic

iTrader: (22)

I have the SMB midpipe/ with the subrate cat on it and compare to rx7 store resontaed midpipe it's about the same noise level with the RB catback, Only problem with the rx7store midpipe car stinks like carzy and you will smell like exhaust at all times, also the SMB ain't cheap.

Montego

iTrader: (1)

A resonated MP is world's away from an unresonated one. I had a regular MP for like a week. Not kidding either, it was so loud that my GF (now my wife) could hear me when I was getting off the freeway ( about 1500 ft as the crow flies). Took that **** off, slapped a resonated one and returned my car back to civility.

Moe Greene

iTrader: (2)

Hey SpeedCrazie,

Make sure you upgrade your fuel system, better to be safe than sorry, wouldn't want to run out of fuel and lean out

Moe Greene

iTrader: (2)

I'm running pretty much the same setup. I have an adaptronic ECU, BNR stage 3 turbos, downpipe, midpipe, TE catback. I'm having boost creep with that setup, I would honestly upgrade your fuel system first before going with a midpipe. From what BLUE TII once said "I would not run a turbo/turbos that I cannot match its output with fuel"

Montego

iTrader: (1)

I'm not sure how to take that...

In one frame of mind maybe he means to have sufficient fuel mods to support the turbo for a particular psi. Which yes the entire forum agrees
or
does he mean upgrade the fuel setup arbitrarily because the new turbo has a much higher capability? If that the case, then the same can be said about the stock turbos then. But come on, let's not go over board here...

Most importantly, if you are experiencing creep and don't have the fuel capacity to support the higher levels of psi then you either port the wastegate or upgrade fuel setup. The first is fixing the problem, the second is a band-aid fix. But they will both work in terms of not having your engine detonate because of lack of fuel scenario.