Question Involving Exhaust,Intake and BOV

[ByrdMan23]

I have a 07 speed 3 currently running a reallllllyy free flowing exhuast. I took out the resonators and muffler and also replaced the stock cat with a racing cat by magnaflow. I also am running the cpe nano intake and before a injen CAI.I have had a HKS SSQV 2(recirc.) and the forge bypass valve.
My problem is that i have had backfiring issues with both valves.
I really want to buy a hks again but i fear that i will just have the same problem. I have a thought that if i replace the racing cat back with my stock one that it will balance out the valve.

Does anyone know if the stock cat makes a big difference to the air to fuel ratio, and could it possibly be the difference in my car backfiring or not?

Any input would be apprecited

 

[johns]

you running those valves recirculated?
i backfire, i don't even care anymore

 

[blackdragon0731]

have you gone through your ECU to re tune your car after those mods? thats probably your problem.

my car, just with a COBB SRI and HKS SSQV recirc. has issues starting up when i fill it up with gas. its a small inconvenience i just have to give it a little gas so it doesnt die, but its still annoying.

invest in an accessport

 

[AutoEuphoria]

AP won't help that issue...I was backfiring all the time with the AP, switched to stock and it's less now. I have no cats, though...it just comes with the territory. It's the exhaust more than anything...I think all cars pop/backfire to an extent, but the exhaust muffles the sound. Same thing happens with a V8 with straight exhaust...popping/backfires/etc, especially during off-throttle decel or quick shifts

 

[ByrdMan23]

Wow I can't believe you have problems with just intake and valve black dragon .. It's funny you mention start up trouble when you fill up cuz I had the same issue with my forge bypass.. It doesn't make sense to me
But as far as combating backfire it's gonna be more exhaust controlled? Or I could pay alot to tune it and I'm assuming that would void the warranty
How big of a deal is backfiring for a car.. Am I really hurting all that much?

 

[AutoEuphoria]

It depends on what you mean by "backfire"...are we talking a little popping or giant BANGs?

Popping is normal with a more open exhaust and won't do any harm. Giant BANGs might be a bit different. I used to get those every once in a while if I shifted hard/fast while accelerating, but that was when I was running the Cobb AP...now that I'm back to the stock tune I don't get that anymore.

Also, I currently have an intake, catless DP and catless TP...I used to have a Forge BPV, but right now I'm using the stock one. I have never had an issue with start-ups...it's fired right away every time.

 

[ByrdMan23]

I know what your saying.. I get popping when decelerating and recently a pretty loud pop when cpmming down from 3rd .. Occasionaly when fast shiftingi get a pretty loud pop.. But I've seen some of the backfireson YouTube where they are extremly loud.. It's not like that but it definitley let's you know it's there..
I reallywant the hks but I'm just wandering how it will respond with my exhaust from past experience
I am considering throwing on some of the old stuff(stock cat and maybe the muffler) to help keep it from backfiring with the valve

 

[mazdaspeed32007]

you running those valves recirculated?
i backfire, i don't even care anymore

hahaha. i want my stock cat-back....back. im going to cut out 1 resinator and put a custom test pipe in, pull the stock cat and add my pypes mini cat and use the muffler i have in place of the stock one and use the stock pipe over the suspension. sounds complicated but im going to have the whole thing chopped up and pulled out so im going to mix and match for a bitchen sound no one has. i side with you though....i really dont even care anymore.

 

[ByrdMan23]

So would everyone say that most backfire issues are caused from altering the exhaust?

 

[mazdaspeed32007]

for the most part. youll get that with any vehicle though. a non turbo V-8 pops and backfires like a mofo. its just the unburnt fuel making its way through an unrestricted exhaust. your cats and mufflers stop close to all of them when running stock. you lose the parts, you lose the quiet.

 

[AutoEuphoria]

Amazing how, when you remove a muffler, the exhaust noise becomes less muffled lol

 

[ByrdMan23]

yea alright.. the only thing is i talked to a guy with stock oem exhaust and has a CAI, 3 inch turbo inlet pipe and hks recirc. and its popping.. so i dunno..
i'm thinking that any time you have to much air flow the computer tries to adjust and sends to much fuel..
im thinking about the turbosmart valve since you can somewhat "tune" it

 

[ByrdMan23]

so since my car only pops with a aftermarket bypass valve wouldnt a turbosmart valve solve my problem.. cuz i could just adjust it to however much airflow is needed in recirculation?

 

[MSMS3]

Sorry to point this out, but taking out the resos and stock muffler does not make the exhaust more free flowing. They are all straight through components. It will make things louder and change the tone. The stock CBE is capable of flowing well over 300 whp from the factory. The restriction is upstream -- the sharply bent inlet on the DP and the factory cats, both of which are not very free flowing.

It is helpful to go with the free flowing second cat. That's a good move, IMHO, but it is only part of getting any real improvement in flow. If you have an O2 bung on that second cat, you can delete the very restrictive factory DP and first cat, go to a 3 inch aftermarket DP into a high flow second cat and still meet emissions control standards and not throw CEL's.

Now to the issue of the backfire/popping. Personally I think that is mostly a product of the BOV. I'm running the factory BPV (yes, even with uncatted DP/RP) and get little or no backfire or popping, whether during WOT shifting or when decelerating. It will happen occasionally because we run so rich.

If I were wagering a bet, I'd put my money on stopping your complaint by going back to the factory BPV or getting a good BOV that operates only in full recirc mode. Otherwise your MAF reading is not matching the actual true fuel/air ratio, you are running even richer and further contributing to the problem.

Just one opinion.

 

[ByrdMan23]

I agree with pretty much everything you said.
however i do feel that there is a noticeable difference in gutting the stock exhaust than just sound.. the way that the resonators and muffler quite the sound is by making the air travel around longer and somewhat linger in those pipes which causes back pressure..
i have ran 2 different valves in recirc. and still had problems
@ I have heard that the stock bypass valve is designed to leak.. which in a way makes it a hybrid somewhat.. Im thinking the only valve that will help backfiring issues is one that operates somewhat like the stock valve(turbosmart)

 

[RichB]

The poping is just a result of better airflow. If you have air passing through the combustion champer faster than normal, the fuel simply doesn't have time to burn completely.

When I just had a CAI I would pop after doing a WOT pull.

 

[MSMS3]

I agree with pretty much everything you said.
however i do feel that there is a noticeable difference in gutting the stock exhaust than just sound.. the way that the resonators and muffler quite the sound is by making the air travel around longer and somewhat linger in those pipes which causes back pressure..
i have ran 2 different valves in recirc. and still had problems
@ I have heard that the stock bypass valve is designed to leak.. which in a way makes it a hybrid somewhat.. Im thinking the only valve that will help backfiring issues is one that operates somewhat like the stock valve(turbosmart)

Byrdman23, I think we both have the same view that the BPV is the likely culprit.

But, I have examined our resos carefully. They are the straight through bottle type. There are no internal baffles. The 2.8 inch center pipe just shoots straight through. That pipe is surrounded with a solid sound absorbing material that fills the outer shell. So, I don't see how they could produce any backpressure. I can't speak for the muffler, you may be right about it. If it does have baffles, it still flows more CFM than our K04 turbo can produce on the intake side.

Interesting theory about our stock BPV. Maybe that is a "safety" design by Mazda's nanny patrol to keep us from holding boost at high rpm? LOL. But mine does not seem to leak -- so far!

All I can say is that I'm running a 2nd gen MSCAI intake and on the exhaust side a 3 inch full catless downpipe and race pipe into the stock CBE. I retained the stock BPV and have NO, I repeat NO backfires or pops. The closest to a "backfire" I can come is a mild "gurgle" when decelerating in gear. Free flow exhausts do that whether running forced induction or normally aspirated.

So, I lean toward the BOV as the producer of the OP's backfire. One easy and quick way to tell: OP can test this theory by reinstalling the original BPV (takes what - two minutes?), and take a test run. I'd be interested in knowing the outcome.