Exhaust Baffles
Discussion
I'm having a bit of a problem with noise on my Dax Rush.
It's a v6 with two side exhausts. Each has a cat and straight through silencer (perforated tube surrounded by wadding).
As is, noise is about 104 dB on the static test. I got it down to 99.2 for my IVA test (failed by 0.2dB!) by putting large penny washers in the ends:
It was still a bit loud if I'm honest though, so I wouldn't mind getting it down a bit more. Rather than just make the hole in the washer a bit smaller, I'm wondering about these things as a more permanent reduction:
I'm going to try putting one up inside the perforated section (as it's the only straight bit of pipe I have). Now I understand that this will cause some restriction and hence lower power, a bit. But what I don't know is, are there any other effects? Can it affect fueling for example, or require any changes to my engine map?
Or does anyone have a better idea of how to reduce the noise? A perforated cone with pointy end into the exhaust is the idea which keeps comming into my mind, but it'd be hard to make, and I've no idea if it would actually be any better than the one above.
It's a v6 with two side exhausts. Each has a cat and straight through silencer (perforated tube surrounded by wadding).
As is, noise is about 104 dB on the static test. I got it down to 99.2 for my IVA test (failed by 0.2dB!) by putting large penny washers in the ends:
It was still a bit loud if I'm honest though, so I wouldn't mind getting it down a bit more. Rather than just make the hole in the washer a bit smaller, I'm wondering about these things as a more permanent reduction:
I'm going to try putting one up inside the perforated section (as it's the only straight bit of pipe I have). Now I understand that this will cause some restriction and hence lower power, a bit. But what I don't know is, are there any other effects? Can it affect fueling for example, or require any changes to my engine map?
Or does anyone have a better idea of how to reduce the noise? A perforated cone with pointy end into the exhaust is the idea which keeps comming into my mind, but it'd be hard to make, and I've no idea if it would actually be any better than the one above.
Well first goal is to get through IVA, but I want to track it as well and don't really want to be adding/removing baffles all the time. So I'd rather have something permanent if possible. The curved end pipes make it a bit more of a faff as I have to dismantle them to get at a straight bit. I guess for track work I could make something to go in the curved section, but for IVA they need to be able to stick the emissions probe in there. I just got away with the previous washers but the hole was only just big enough.
I've no doubt I can get the sound down, it's the knock on effects I'm worried about.
In answer to Steve's question, yes, n/a 3.0 V6, one exhaust per side. It's a 47mm perforated tube, wrapped with stainless steel wire, then acoustic padding around that. Quite tightly packed, I don't think you could squeeze much more in. I'm afraid I don't know what sort it is:
Pipe with steel wool, also shows how short it is:
Naked pipe (I'm trial fitting the baffle here)
The wadding - it's kind of stringy stuff, a bit like wool.
View down into the Cat
I've no doubt I can get the sound down, it's the knock on effects I'm worried about.
In answer to Steve's question, yes, n/a 3.0 V6, one exhaust per side. It's a 47mm perforated tube, wrapped with stainless steel wire, then acoustic padding around that. Quite tightly packed, I don't think you could squeeze much more in. I'm afraid I don't know what sort it is:
Pipe with steel wool, also shows how short it is:
Naked pipe (I'm trial fitting the baffle here)
The wadding - it's kind of stringy stuff, a bit like wool.
View down into the Cat
Hmmm ok I can try and repack them differently. I'd be surprised if I can lose 6 or 7 dB just by playing with the wadding though?
The wire wool is to prevent the wadding burning through isn't it?
I have stuck the baffles in and will be testing how much reduction they make as well.
Pain in the arse, this car building lark!
The wire wool is to prevent the wadding burning through isn't it?
I have stuck the baffles in and will be testing how much reduction they make as well.
Pain in the arse, this car building lark!
Sorry, should have updated.
Well I've had it all apart and repacked - probably made it worse tbh as it was very neatly done before! It doesn't seem too tight from what people have said above, there's no spare space but it's not hard pressed in.
Anyway, I've stuck the baffles in the straight section for now, which has certainly reduced the noise. I'm going to get the emissions looked at as well, so it'll be interesting to see how much effect they have.
Plan then is to take the baffles out, and shorten them /open them up some so that they fit into the curved end; then I will have something neat and easily removable for trackdays etc.
Well I've had it all apart and repacked - probably made it worse tbh as it was very neatly done before! It doesn't seem too tight from what people have said above, there's no spare space but it's not hard pressed in.
Anyway, I've stuck the baffles in the straight section for now, which has certainly reduced the noise. I'm going to get the emissions looked at as well, so it'll be interesting to see how much effect they have.
Plan then is to take the baffles out, and shorten them /open them up some so that they fit into the curved end; then I will have something neat and easily removable for trackdays etc.
Mr2Mike said:
Those cheap DB killers are horribly restrictive, they really should be sold as BHP killers. A much better solution is to make something like the baffles used in aftermarket bike cans, effectively just a narrower bore pipe about 6 inches or so long that have a shroud on the inside end and a larger diameter part on the outer end that's a snug fit into the tailpipe. Obviously a bike one won't fit as you have a much larger bend, but you could easily make one from e.g. 22mm copper pipe and some plumbing fittings to test the theory. You could then get something nicer fabricated in stainless if it works.
This is the thing - I couldn't find any actual data to show if one type sapped power more than the other.I can actually easily modify the ones I've got to be like the one in your link if it's going to be better. But short of paying for a RR session I expect I'm never going to know for sure. If anyone's got any hard evidence one way or t'other I'd love to see it!
one eyed mick said:
Its common sense[?]realy you are limiting the amount of gas coming out so it will be quiter but will loose power , possibly rpm and may cause over heating ! do you want that ?
Well, both types of baffles will cause a restriction, because both have a smaller pipe; what's not clear to me is if one design is better than another. Which is why I was asking if anyone knew for sure.I can't have a longer can, because it's a side pipe and the wheel arch is in the way. And as for diameter...they are huge already (6 inches), it'd be ridiculous to have them any larger, you'd never be able to step over them! Having the cats in there is taking up a fair bit of the length, but I'm stuck with that.
Short of remanufacturing the exhausts, which is going to be very expensive and time consuming (again), all I can do is bung them up really. I'd rather get it on the road than spend another 3 months and a thousand quid playing with the silencers. So bungs it'll have to be, they can come out after, and I'll make / modify some smaller ones for track days.
stevieturbo said:
how is it common sense ?
You're assuming that the system in place is actually restrictive for the engine in question.
Which when it is a relatively small capacity V6...so only 1/2 overall airflow going out each exhaust. Which if say 250hp is only 125hp, It isnt going to need a 6" drainpipe out the side of each car to be free flowing.
It seems to be sized about right according to the rules of thumb I've seen. 280bhp, so 140 per side, seems to require about a 2 inch pipe, so 47mm should be about there.You're assuming that the system in place is actually restrictive for the engine in question.
Which when it is a relatively small capacity V6...so only 1/2 overall airflow going out each exhaust. Which if say 250hp is only 125hp, It isnt going to need a 6" drainpipe out the side of each car to be free flowing.
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