HIGH PITCHED SCREECH AT 0.5 BAR BOOST

[nitroman]

Can anyone give me the measurements of the wide oval outlet on the Peco muffler? I want to replace my tip with something similar & will stop by Copeland Welding when I get back.

[Paul.P]

Can anyone give me the measurements of the wide oval outlet on the Peco muffler? I want to replace my tip with something similar & will stop by Copeland Welding when I get back.

Matt, externally its 4 7/8" x 3", & internally its approx 4 1/4" x 2 1/4, hope this helps.

[DeeAitch]

Can anyone give me the measurements of the wide oval outlet on the Peco muffler? I want to replace my tip with something similar & will stop by Copeland Welding when I get back.

Matt, I think that pic is the one from my own design muffler (see last post on page8), not the Peco.
It is 3.85" (98mm) x 2.4" (61mm)

[Rambo]

Matt - this is the PECO design with inner tailpipe.

See PaulP's post above for the dimensions

[TomE]

A quick update for those with a screeching/whistling PECO exhaust: I'm sending my rear section back to PECO either next week or week after for some mods and will then refit and see if it's fixed. I gather from Dave Jones at PECO that no one else with a screecher has returned it yet, but that Geoff might be planning to?

I'll let you know the outcome.
Tom

[GeoffSmith]

Snap!

[TomE]

My exhaust is back from PECO and the screeching/whistling has completely gone - thanks Dave and the folks at PECO

You'll see from the before and after pics below that the mod looks to be simply circumcising the inner pipe in the final section. If any other screechers have the inner pipe, returning the rear section to PECO should sort you out. Anyone ordering a PECO in future is probably best going with the circumcised design, particularly if you have increased boost levels.

[paulwatkins]

Did Peco give you an explanation as to why it was screeching with the inner pipe in place?

[philip_sloper]

Tom E.

If you read my post of 9th October it already tells you that the solution is to remove the inner pipe from the tail section. That was the mod that they made to mine at the time.

[TomE]

If you read my post of 9th October it already tells you that the solution is to remove the inner pipe from the tail section.

I'd read that at the time - you'd also said Dave was still investigating the impact of pipe length variations and said on 10th Oct that PECO wanted to keep the inner pipe as the standard design. Dave told me he was still waiting for someone to send back a screecher so that he could test out a mod, hence my volunteering.

In my conversations with Dave he hadn't been specific about the mod they were intending to do, so I didn't know what I was going to get back. Just thought it might be useful for people to know that the PECO solution is complete circumcision and not a smaller scale dimensional adjustment. Otherwise, if you'd specifically chosen the oval+inner design you might be disappointed to have it back from PECO as an oval only.

Paul - I haven't had an explanation from PECO but I'll ask Dave if he could post something here.

[GeoffSmith]

It's like the resonance you get when you blow over the top of a wine bottle.

Thanks for the information Tom.

[RichyP]

if you'd specifically chosen the oval+inner design you might be disappointed to have it back from PECO as an oval only.

I think I would be disappointed with this mod, having chosen the inner + oval. Can't quite see, but is the cut tidy or hacked off inside? Did they remove the oval and re-weld it (welds look a little rusty)? I was hoping that the mod might be something like a mass damper attached to one or other pipe and hiden from view.

I'd prefere to keep the inner pipe as originally this was described as being the technically superior design for gas flow.

Mine's been screeching away for 18 months since installed - I quite like it - gives me options for scaring people at bus stops - screech past or lift off backfire

Finally interesting to note that the inner pipe on Tom's car seems 10 to 15mm recessed - mine is almost touching the oval more like the yellow cars' above. Clearly small dimensional changes have no bearing on screech

[GeoffSmith]

Has anyone tried pushing some roof insulation in the cavity? Having seen Tom's circumcision, I'm considering leaving mine as it is, as it is nicely coked up and can hardly be seen.

[TomE]

Can't quite see, but is the cut tidy or hacked off inside? Did they remove the oval and re-weld it (welds look a little rusty)?

The inner pipe has been cut off at the base, where it exits the rear box into the oval tailpipe. Think you can see that in the end-on pics below (as well as the sorry state of my paintwork!). I'm not sure if they removed the oval and re-welded or did it some other way. I've only got the photos to go on at the moment but will take another look at the car tomorrow.

I'd prefere to keep the inner pipe as originally this was described as being the technically superior design for gas flow.

I'd read this too. I've suggested to Dave that he provide an update on the problem and solution. Like Geoff, I think it's the blowing over a bottle effect - see right side of first pic for my own experiments!

[DeeAitch]

I think it is "Jet" noise, quite a common problem on OE and not so easy to design out.
In this case it is probably caused by the gas hitting the inward curl on the oval finisher. Geoff's raid on the loft trial was to prevent this and seemed to prove the point.
You will notice the inner round pipe curls outwards, a common fix if you don't want the expense of a 2 piece design as shown on my earlier photo (beer still unclaimed!)
With the revised shape, i.e outer finisher only, you might still get a noise due to the inward curl being exposed to gas flow. However it will occur at a higher engine speed as the gas will slow down due to the sudden expansion it now sees. Probably not noticable in real life driving unless you are on the limiter with 250 BHP .

Worth checking the temps back there after a hot run, especially on track use, as it looks very close to the bumper.

[JIMBO]

Hi and thanks to every one who has helped or contributed to resoving this problem. I'll get mine back to Peco in the spring, it's too cold to mess about under a car at the moment.
Now, any suggestions about how to get rid of the Mother-in-Law ?
Best regards
Jim

[GeoffSmith]

Hi and thanks to every one who has helped or contributed to resoving this problem. I'll get mine back to Peco in the spring, it's too cold to mess about under a car at the moment.
Now, any suggestions about how to get rid of the Mother-in-Law ?
Best regards
Jim

Get a bigger box, and sent them both to Dave!

[Monty]

Would it not be easyer to remove the inner pipe with a dremal or similar save taking the silencer off

[GeoffSmith]

Mine's off anyway, but it's going back on!

[Rambo]

Pleased to hear that your screech has been cured Tom but IMO the end result doesn't look so good