Honda and Acura Car Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
108 Posts
Discussion Starter #1
For the experienced and knowledgeable:

I got a 6th generation inline 4 and recently got a dual exhaust conversion (whole piping from the CAT) with a custom Y pipe. It sounds reallie deep and not too loud, just the way I like it.

However, I think that I am getting back pressure at high RPM's. As I accelerate, the exhaust gets louder and louder until about 4.3 RPM's, and then gets alot quieter, basically when the Vtec kicks in. I dont know anyone else who's exhaust system is quieter at 6 RPM than at 4 RPM.... The only mods that I have are 4.2.1 ss headers and an intake filter (w/ stock piping because my intake pipe got messed up). I have other mods, but its just like strut bar, etc that wouldnt effect this situation.

I've had so many different shops tell me different stories.... 1> One says that I am getting more "free" flow, thus getting less resonation.... umMMm thanks for nothing ...
2> another shop told me that it is because I'm getting back pressure in the High RPM's because my car is meant to be single mufflered and I put on dual..... ok.. but I thought dual exhaust would more likely cause back pressure in the low end....
3> another shop told me that I just need to get a real intake and that my throttle body isnt pulling in enough air with the stock, thin pipe........ is he just trying to sell me an intake???

Sorry about the long entry, but guys, what r your opinions?
 

·
Registered
Joined
·
10,424 Posts
You can buy and install a back pressure meter if you’re really that concerned about it.

Generally speaking in my theory going duel on any inline engine setup is going to add back pressure because adding the Y pipe and the bends needed to accommodate the extra piping.
 

·
Registered
Joined
·
1,428 Posts
you lose power with dual exhaust...and its "ricey"
 

·
Registered
Joined
·
271 Posts
What's the diameter of the piping before & after the split? What kind of mufflers do you have, and how many CFM do they flow? Stock or aftermarket cat?
 

·
Registered
Joined
·
1,428 Posts
basically what it sounds like is this.......when vtec kicks in the engine sucks in a whole lot more air........and with your setup how it is now you are already running lean (TOO MUCH AIR NOT ENOUGH GAS)....and then when that vtec kicks it wants to suck in that extra air....and well......you know how it goes from there
 

·
Registered
Joined
·
148 Posts
all interesting ideas at least. but what mufflers are you using? some mufflers dont sound well when the rpms get up, they just fade or hiss out sort of.

the system sound interesting at least to inspect, i havent seen 1 myself. that y pipe depending on design could be a big back up though. y pipes typically are for joining 2 exhuast pipes to dump into 1 not reversed.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #7
RE: What's the diameter of the piping before & after the split? What kind of mufflers do you have, and how many CFM do they flow? Stock or aftermarket cat?

I believe it goes from 2 3/4 from the stock cat until the Y pipe, and then the two pipes after the Y pipe goes into 2 1/2. The mufflers are just some OBX free flow mufflers. As for the CFM, I'm not too sure how much my current set up is outputting. Some one suggested to me to get a turbo and then I will eliminate this problem.... but thats a lil further down the line. wonder if theres some thing I can do more sooner....
 

·
Registered
Joined
·
271 Posts
no one said:
I believe it goes from 2 3/4 from the stock cat until the Y pipe, and then the two pipes after the Y pipe goes into 2 1/2. The mufflers are just some OBX free flow mufflers.
Well with that size piping (mandrel mends?), there's no way you've got too much backpressure. Even if they're crush bent, that's probably too much airflow for your application.

As to why it's quieter at high rpms, I don't know.

If it were my car, I'd do away with the 2nd exhaust pipe/muffler, go to 2.5" OD all the way through, enlarge the collector on the header to 2.25", and put a good high-flow cat in.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #9
RE: all interesting ideas at least. but what mufflers are you using? some mufflers dont sound well when the rpms get up, they just fade or hiss out sort of.

the system sound interesting at least to inspect, i havent seen 1 myself. that y pipe depending on design could be a big back up though. y pipes typically are for joining 2 exhuast pipes to dump into 1 not reversed.


I have a single pipe (about 2 3/4in) from the cat and it hit the Y pipe. The two pipes after the Y pipe are about 2 1/2 in diameter and go into the high flow mufflers. They're just some free flow OBX mufflers, but they sound great. Nice, smooth, and really deep without all that raspy or ricey sound. And its not annoyingly too loud either. I even think it looks nice. I have had so many people compliment on the sound and looks, but performance wise....... guess I cant have it all. Some one suggested to get a turbo, which would boost my performance and increase enough air into my exhaust pipe, eliminating my problem. But turbo is a lil further down the line.... wonder if theres anything else I can do to get more air....
 

·
Registered
Joined
·
148 Posts
heres an easy test, cap off 1 muffler and see how it sounds then. if its the same (roughly) then its the mufflers design most likely.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #11
Daemione said:
Well with that size piping (mandrel mends?), there's no way you've got too much backpressure. Even if they're crush bent, that's probably too much airflow for your application.

As to why it's quieter at high rpms, I don't know.

If it were my car, I'd do away with the 2nd exhaust pipe/muffler, go to 2.5" OD all the way through, enlarge the collector on the header to 2.25", and put a good high-flow cat in.
I've gotten nothing but compliments on the looks and the sound on my new exhaust system.... the only issue is the performance, which makes me grimace every time I think about it. I know its alot more practical to just go single catback exhaust, but I'd hate to have to get rid of my custom setup. About enlarging the collector on my header to 2 1/4, how do I go about doing that? Is it a procedure that I can do? I do have a high flow cat converter but it doesnt have a place to put in my O2 sensor. And the shop said they didnt have a drill that could drill the right hole into it because it is stainless steel. Needless to say, it is not installed..... if only there was a way to get more air into my exhaust......
 

·
Registered
Joined
·
108 Posts
Discussion Starter #12
89 IROC Z said:
heres an easy test, cap off 1 muffler and see how it sounds then. if its the same (roughly) then its the mufflers design most likely.
cap off 1 muffler as in physically just covering the open it? and should I rev my engine while performing this test? or let it run at idle?
 

·
Registered
Joined
·
148 Posts
cap 1 muffler in some way good enough that you can drive the car and see if it still sounds the same. your not going far so it wont have to be incredible and the pressure shouldnt blow out something like a rag, towel or T-shirt to easy. just reving the engine will not work since the motor sounds totally different under load.

you started off not liking the sound above 4K but now you say you are worried about performance. have you noticed a lose in performance or just a sound change? and do you have any numbers to make you think there has been any lose? i would doubt there is a performance lose at all but a change in tone i can understand.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #14
89 IROC Z said:
cap 1 muffler in some way good enough that you can drive the car and see if it still sounds the same. your not going far so it wont have to be incredible and the pressure shouldnt blow out something like a rag, towel or T-shirt to easy. just reving the engine will not work since the motor sounds totally different under load.

you started off not liking the sound above 4K but now you say you are worried about performance. have you noticed a lose in performance or just a sound change? and do you have any numbers to make you think there has been any lose? i would doubt there is a performance lose at all but a change in tone i can understand.
ok, i'll try that. I really cant tell if I lost any HP or not because I added the headers and the exhaust at the same time. I feel a little more boost, but that might be because of the headers. But from what everyone is telling me, I am assuming I am loosing HP from my Y pipe setup. I just dont understand why the Vtec kicking in would actually make my exhaust quieter.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #15
CRXtc said:
basically what it sounds like is this.......when vtec kicks in the engine sucks in a whole lot more air........and with your setup how it is now you are already running lean (TOO MUCH AIR NOT ENOUGH GAS)....and then when that vtec kicks it wants to suck in that extra air....and well......you know how it goes from there
I see your point.... any quick fix for this that doesnt require to me spend several thousands (i'm talking about turbo)?
 
1 - 15 of 15 Posts
Top