HIGH PITCHED SCREECH AT 0.5 BAR BOOST

[TomE]

Phil, is circumcising the standard tailpipe a DIY job or are PECO recommending returning it to them for the work?

Jimbo, thanks for the encouragement! I guess I'm still a bit cautious into the corners and so don't carry as much speed into the straights as you experts. Think I need more practice, more instruction or some sort of fear bypass operation. Saturday's high speed experiments were of course purely for the greater good of all PECO screechers out there, to determine if it happened in 5th as well:
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[GeoffSmith]

Kept out of this as most original posts said the noise came from the front. If from the tailpipe I suspect it is more of a 'Jet' noise than a screetch, coming from the tailpipe itself, a common problem - I have a bolt on tailpipe on my muffler which I can make a 'Jet' noise with at circa 4k RPM if it is not in the correct place
Can someone with a private test track try packing the gap between tailpipe and finisher with Glass wool? You will need to keep it in place with some tape - don't leave it there for more than one quick run

Thanks for the informative post Mr. Itch, better late than never! Let's hope some one can try it out.

My screech has been cured by removing the inner round pipe from the standard Peco tailpipe design, so that only the outer oval pipe remains.

Less than six hours - nice one Philip.


Did Dave offer any long term solution and did he make mention of the turbulence in the tail?

[philip_sloper]

Firstly let me confirm that removing the inner pipe immediately solved the screech problem on my car. Extending the inner pipe also solved the screech, which is why I think it is a dimensional problem and explains why not everyone with the inner pipe gets a screech.

No one who has bought the Peco system without the inner pipe (for aesthetic reasons) has reported the screech problem on this thread, which further supports the theory.

Phil, is circumcising the standard tailpipe a DIY job or are PECO recommending returning it to them for the work?

I think it is possible to remove the inner pipe yourself, but in my case Peco sent me a replacement as I had already modified the pipe arrangement whilst experimenting to find a solution.

[philip_sloper]

Did Dave offer any long term solution and did he make mention of the turbulence in the tail?

I think Peco want to keep the inner pipe as their standard design, and are checking the dimensional relationship so that they avoid the screech problem in future. But I think they will also supply the silencer without the inner pipe if asked at the time of ordering.

I am happy with mine without the inner pipe; there appear to be no adverse effects from turbulence on my car.

[paulwatkins]

Phil, is circumcising the standard tailpipe a DIY job or are PECO recommending returning it to them for the work?

I think it is possible to remove the inner pipe yourself, but in my case Peco sent me a replacement as I had already modified the pipe arrangement whilst experimenting to find a solution.

Guys, when the welds on my inner pipe gave in, I couldn't get it out past the outer oval pipe to remove it.

Peco wanted me to remove the rear section of exhaust and send it back to them for repair.

Paul

[DeeAitch]

Thanks for the informative post Mr. Itch, better late than never! Let's hope some one can try it out.

What do you expect when you lot took so long making your mind up if it was from the front, middle or rear

I did start to get involved when Luca was set on getting his own made up, but backed off when It started getting heavy

Jury's still out on this I fear - for me you will not get a 'screetch' from the tailpipe. Terminology maybe, but a screetch to my lugs is something like the noise you get from a loose fan belt, or maybe 'er indoors when she finds out how much those nice 'rare as hens teeth' - that you simply must have - Lotus bits cost you

This is just an idea for now and easy to test - far be it for me to cast nasturtiums when I haven't even heard the concern yet. As i've said before, Peco have a fine reputation and I'm sure they will be able to get it sorted.
Lets just hope the concern is rare and easy to remedy

[GeoffSmith]

Sorry Dave, couldn't resist it! Now if you'd said w=v(A/VL)½........

To be honest, the source of the tone was difficult to pinpoint - I did ask a mate to hang over the back of the car while I floored it but he refused. Thinking about what you said though, I guess a wrap or two of duck tap between the inner and outer is worth a try.

Geoff

[Monty]

Firstly let me confirm that removing the inner pipe immediately solved the screech problem on my car. Extending the inner pipe also solved the screech

No one who has bought the Peco system without the inner pipe (for aesthetic reasons) has reported the screech problem on this thread, which further supports the theory.

Well think taht explains why i don`t get the screech then

But supprised the inner pipe could cause it, at least it seems as though it`s now been solved

[algirdas]

Dear Phil:

Am I reading this right? Cut out the inner pipe in the picture shown below and no more screech?



Has PECO Dave chimed in on this recently?

Sincerely,

Algirdas

[philip_sloper]

Dear Phil:

Am I reading this right? Cut out the inner pipe in the picture shown below and no more screech?

Yes. That cured it for me.

[David]

Hi all,

I don't think any of you have read the message I posted on 04/09/2007.

Regards

Dave Jones

Head of R & D
A & I (Peco) Acoustics Limited
Sandford Street
Birkenhead
Wirral
CH47 1AZ

Tel. 0151 647 6041
Fax.0151 666 1805

[DeeAitch]

w=v(A/VL)½........ in fact w=v(A/VL)½ x v(A/VL)½ might do it

From the pic it's not easy to see for sure but does the 'curl' on the end of the inner pipe turn towards the inside of the pipe?

I can send someone a bag of glass wool to stuff in the gap if they want to try it. Careful with Duck tape, the pipe gets a tad hot and it will stick like 5hit to a blanket before starting to go up in flames so please, only for a very short try.

[GeoffSmith]

Point taken Mr. Itch but I'll only try it for one short WOT run.

I've just spoken to Dave and I had thought that Philip had returned a screecher to Peco, but that's not the case. I've agreed to take mine off this weekend and return it to Peco for some mods.

Watch this space.

Geoff

[GeoffSmith]

I raided the loft and stuffed the tailpipe between the outer oval inner circular pipe with glass wool.



Nice one Mr. Itch. One more to cross off the list!

Although I had the hood up, there appears to be a certain harshness missing from the exhaust tone as well (not sure whether that's good or bad) so there was obviously a lot going on in that little section. It would be good if someone else could do the same to confirm (although I'm 100% convinced). At the moment, I'd prefer to leave the exhaust on the car to see how it goes. When I get a chance (it won't be tomorrow) I'll ring Dave, if he hasn't looked in, to discuss the way forward. If he still wants a play with a screecher, is anyone else interested in loaning a tail section?

Geoff

[JIMBO]

I would be happy to send my rear box to David When I get back from holiday, but will he be able to modify the mother in law as well.

This sounds like good news. Thanks very much to all who have been involved.

[DeeAitch]

Nice one Mr. Itch. One more to cross off the list!
Geoff

Geoff, You just had to ask nicely

Don't forget to remove the gaffer tape

is anyone else interested in loaning a tail section?

I'll post a pic of my tailpipe later. Might be able to 'arrange" a lend of one if you get desperate

[GeoffSmith]

Don't forget to remove the gaffer tape

I didn't use it in the end as it's jammed in there pretty firm (not like filling transmission line loaded speakers). As long as it doesn't need a Brazilian too often, I can live with it for now.

I don't know if either of the Dave's can fathom this out. I have suffered from boost creep and fuel cutoff for some time since fitting the Peco (port the wastegate is still on the list). There is one stretch of uphill on the way home that I regularly get cutoff, usually when overtaking someone and a car is coming in the opposite direction. I floored it this afternoon and no cutoff even up to the red line (which is something I haven't done for some time). I will keep trying to repeat it, even if I've got to re-introduce the screech temporarily Is it possible that something about the resonance, maybe standing waves in the exhaust, were affecting the wastegate? If any other screechers suffer from fuel cutoff, could you see if you can confirm or disprove?

Geoff

[DeeAitch]

Geoff, it's meant to be a way of identifying the cause, not a solution Don't blame me if you end up with a furry Muff in need of a trim

As for boost creep it baffles me. Could we be killing two birds etc? What level of boost are you running?
Can't see the tailpipe making a big diff tho'
I had a similar issue way back in March / April time but it turned out to be a sticky wastegate after the Winter lay up - put it down to lack of use.

Here is my tailpipe - a free beer to the first person to identify which car I designed it for (ESM you are barred from entering this comp )
Clue : It is not for a Lotus

[GeoffSmith]

Geoff, it's meant to be a way of identifying the cause, not a solution

Well it's a bloody good temporary solution for me Dave as the Polo's just sprung a water leak and the Pug's fuel pump doesn't - just been towed back by the AA.

[dekano]

I now have a VERY high pitched whisle/screech (yes even worse than the mother-in-law) at aprox, 6000 rpm with about 0.5 bar of boost.


Dekano
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