Exhaust Droning - Help Please!

rob250 · March 30, 2020

Help, please! My IS250 (2006) has a terrible droning noise coming from the exhaust system at between 2,000 and 3,000RPM.

Last week I purchased a 2006 IS250 🙂

Coming from an 08 Mercedez C320 I have been very impressed and feel like I should have made the jump to Lexus much sooner!

The only issue is an awful droning from the exhaust system between 2,000 and 3,000RPM.

I took a look and can see the exhaust system has been replaced with an aftermarket unit. The exhaust tips and muffler unit are branded 'PowerFlow'.

Is this an issue with all stainless steel replacement exhaust units or can anyone recommend a solution?

Any ideas anyone?

Texas · March 30, 2020

Aftermarket stainless steel systems have a much thinner wall thickness than the mild steel OEM and will sound very different which will be noticeable in a luxurious car like this!

is200 Newbie · March 30, 2020

yes, its an aftermarket, stainless steel. They do create a drone as you are experiencing and its at motorway speeds around 70mph. Theres no easy work around for it

Had it on my last IS when i moved to a stainless one and it killed the car - my only work around reducing the noise was to drive it in manual mode using the gears (paddle shift operation - 4th and 5th seemed to work well but revs remained high so i did not like driving it like that)

Replacing the central resonator helps as i butchered it eventually and made my own. Replaced the central resonator with an IS200 resonator which fitted good but still needed a bit of fettling but it helped but not quiet enough to stock.

Best to source a mild steel one if you cant live with yours - sure someone on eBay will enjoy the noise yours creates. Cost would be in the region of £300 to £400 for a full system

NemesisUK · March 30, 2020

Can you change the resonant frequency of the exhaust by using worm drive hose clips around the pipe and/or silencer(s)?

Texas · March 30, 2020

Just having a brain fart, but would the woven cloth heat wrap I have seen sometimes on exhaust systems be an option?

rob250 · March 31, 2020

12 hours ago, is200 Newbie said:

yes, its an aftermarket, stainless steel. They do create a drone as you are experiencing and its at motorway speeds around 70mph. Theres no easy work around for it

Had it on my last IS when i moved to a stainless one and it killed the car - my only work around reducing the noise was to drive it in manual mode using the gears (paddle shift operation - 4th and 5th seemed to work well but revs remained high so i did not like driving it like that)

Replacing the central resonator helps as i butchered it eventually and made my own. Replaced the central resonator with an IS200 resonator which fitted good but still needed a bit of fettling but it helped but not quiet enough to stock.

Best to source a mild steel one if you cant live with yours - sure someone on ebay will enjoy the noise yours creates. Cost would be in the region of £300 to £400 for a full system

Yes it is exactly like you say - drone at 70mph on the motorway...

So basically no workaround or fix except a replace then.

Any idea where I can source a mild steel one? I've looked on eBay this morning and couldn't find one...

rob250 · March 31, 2020

11 hours ago, NemesisUK said:

Can you change the resonant frequency of the exhaust by using worm drive hose clips around the pipe and/or silencer(s)?

Any guides/videos on how to do this Nemesis?

is200 Newbie · March 31, 2020

2 hours ago, rob250 said:

Yes it is exactly like you say - drone at 70mph on the motorway...

So basically no workaround or fix except a replace then.

Any idea where I can source a mild steel one? I've looked on eBay this morning and couldn't find one...

eBay item numbers

172832886475 - this is the centre section

163085024957 - this is the rear section

Taking it back to stock you would need to replace these sections - chances are that the car has had a cat back system fitted which is from the centre resonator to the exhaust boxes - the company that fitted the ss exhaust may have chopped off the flange needed to connect the centre to the first part of the system so before doing any buying you will need to see if that is the case, if it is then you will need to buy a straight pipe adapter to fit centre to existing pipe. Fitting would best be done at an exhaust garage and best to take it there first to see what they can offer.

I would suggest replacing the boxes first to see if you could cope with that noise reduction then the centre section next but i would imagine the whole lot would need replacing.

OldTrout · March 31, 2020

12 hours ago, Texas said:

Just having a brain fart, but would the woven cloth heat wrap I have seen sometimes on exhaust systems be an option?

Texas could be right. This stuff has got to be worth a £10 punt to save an otherwise serviceable system.

I don't know where it would be best to apply it but as Nemesis says adding weight will alter the resonant frequency and this stuff might add damping as well.

John

KenMavor · March 31, 2020

51 minutes ago, is200 Newbie said:

Ebay item numbers

172832886475 - this is the centre section

163085024957 - this is the rear section

Taking it back to stock you would need to replace these sections - chances are that the car has had a cat back system fitted which is from the centre resonator to the exhaust boxes - the company that fitted the ss exhaust may have chopped off the flange needed to connect the centre to the first part of the system so before doing any buying you will need to see if that is the case, if it is then you will need to buy a straight pipe adapter to fit centre to existing pipe. Fitting would best be done at an exhaust garage and best to take it there first to see what they can offer.

I would suggest replacing the boxes first to see if you could cope with that noise reduction then the centre section next but i would imagine the whole lot would need replacing.

If it's Powerflow it has a lifetime guarantee and it maybe worth getting it checked out. You need to try and get in contact with the previous owner and see where it was done, or get the receipt, and take it into any powerflow franchise and get it checked. I have a powerflow and was aware that it could drone and told them so and that I would not accept a drone at 70mph. The guys played around with the pipe diameter, on the rear exhaust section, as well as the silencers and the exhaust is quiet with no drone at 70mph. It is throatier that the original but does show off the V6 engine better.

rob250 · March 31, 2020

2 hours ago, KenMavor said:

If it's Powerflow it has a lifetime guarantee and it maybe worth getting it checked out. You need to try and get in contact with the previous owner and see where it was done, or get the receipt, and take it into any powerflow franchise and get it checked. I have a powerflow and was aware that it could drone and told them so and that I would not accept a drone at 70mph. The guys played around with the pipe diameter, on the rear exhaust section, as well as the silencers and the exhaust is quiet with no drone at 70mph. It is throatier that the original but does show off the V6 engine better.

Did you manage to completely eliminate the drone Ken?

Or did the drone just must to a higher/lower RPM?

rob250 · March 31, 2020

3 hours ago, is200 Newbie said:

Ebay item numbers

172832886475 - this is the centre section

163085024957 - this is the rear section

Taking it back to stock you would need to replace these sections - chances are that the car has had a cat back system fitted which is from the centre resonator to the exhaust boxes - the company that fitted the ss exhaust may have chopped off the flange needed to connect the centre to the first part of the system so before doing any buying you will need to see if that is the case, if it is then you will need to buy a straight pipe adapter to fit centre to existing pipe. Fitting would best be done at an exhaust garage and best to take it there first to see what they can offer.

I would suggest replacing the boxes first to see if you could cope with that noise reduction then the centre section next but i would imagine the whole lot would need replacing.

Thank you for the ideas!

I checked the auction for the rear section and this too is stainless steel not mild- won't this drone as well?

rob250 · March 31, 2020

"chances are that the car has had a cat back system fitted which is from the centre resonator to the exhaust boxes"

So I managed to get under the car tonight to take a video... any ideas what is original and what has been replaced?

Has the centre section been replaced as well or just the rear section?

rob250 · March 31, 2020

8 minutes ago, rob250 said:

"chances are that the car has had a cat back system fitted which is from the centre resonator to the exhaust boxes"So

Video_31-03-2020,_20_10_52.mov

I managed to get under the car tonight to take a video... any ideas what is original and what has been replaced?

Has the centre section been replaced as well or just the rear section?

https://www.dropbox.com/s/p6vi8yr7eoo0wc7/Video 31-03-2020%2C 20 10 52.mov?dl=0

rob250 · March 31, 2020

In case the video doesn't work I've added a few pictures below 🙂

KenMavor · March 31, 2020

6 hours ago, rob250 said:

Did you manage to completely eliminate the drone Ken?

Or did the drone just must to a higher/lower RPM?

My hearing is pretty crap but my wife tells me that there is little to no drone.

Checking back in the invoice the Powerflow guys used wider bore connecting pipes and then scaled down as required. I am presuming that this was they way they eliminated the drone.

is200 Newbie · March 31, 2020

May be worth a go getting intouch with powerflo as mentioned above - think you may need a reciept unless they took the car detail to act as the guarantee but they may be able to resolve it cheaper than the replacement.

It looks like from the last picture, on the left side of the image of the exhaust, that they have kept the original centre resonator .... looks like the ss exhaust has been joined onto the system after the resonator? There is what looks like a black sooty mark also on the join unless that is a shadow?

I can remember wire wool being used in the past to quieten exhausts down (bunging the boxes up with it but it does not last and this may create a lot of back pressure and interfere with the exhaust sensors

rob250 · April 1, 2020

Just got off the phone with powerflow and they were less than helpful. Mentioned that they could run a diagnostic and fit add an additional silencer starting at £120.00, but likely will be more...

I think for that much money I would be more comfortable just replacing it with an original (new/used) OEM unit.

From the video can anyone tell me has the centre section been replaced as well or just the rear section?

https://www.dropbox.com/s/p6vi8yr7eoo0wc7/Video 31-03-2020%2C 20 10 52.mov?dl=0

Baldguy · April 1, 2020

When i bought the 430 it had huge 4" tail pipes and a stainless Powerflow exhaust that gave it a nice V8 burble but too loud for me and droned under acceleration and motorway allot. My exhaust shop said it was due to them using round back boxes (not sure why) but i guess its how the gases circulate.

What he did was cut the back surface out of both of the exhaust boxs where the tailpipe goes in, insert a length of pipe (not sure of length) into the box and re-weld up putting 3" tailpipes on. This quitened it down enough and stopped the droning. I have no idea why this works but it does and its cured the droning and just has lovely V8 burble to go with the Lexus prestige looks

is200 Newbie · April 1, 2020

2 hours ago, rob250 said:

Just got off the phone with powerflow and they were less than helpful. Mentioned that they could run a diagnostic and fit add an additional silencer starting at £120.00, but likely will be more...

I think for that much money I would be more comfortable just replacing it with an original (new/used) OEM unit.

From the video can anyone tell me has the centre section been replaced as well or just the rear section?

https://www.dropbox.com/s/p6vi8yr7eoo0wc7/Video 31-03-2020%2C 20 10 52.mov?dl=0

Can see it better now - it looks like the centre box has actually been replaced as part of the ss system you can see where this has been joined by a pipe adapter at point 0:29 in the video. Reason why these manufacturers/fitters of the ss systems do this is because they would need to replace the two cats on the centre section (car has 4 cats in total with two on the exhaust that you can see in the video) but as you can see in the video at the same point 0:29 the manufacturer has kept the spring expansion joint which is good if it is as per the original spec. The shop that done mine years ago just cut that off and welded it together so there was no expansion joint.

In that case, if the jointt is fitted to the exhaust as per spec, then, if it was me, i would replace the back boxes as the first step to see how that helps.

It may also be good for you to keep the centre box if you can as thats the point where a lot of original exhausts rot, just there the gasses escape from the box so if it is an ss box then it will last a lot longer than stock.

KenMavor · April 1, 2020

6 hours ago, rob250 said:

Just got off the phone with powerflow and they were less than helpful. Mentioned that they could run a diagnostic and fit add an additional silencer starting at £120.00, but likely will be more...

I think for that much money I would be more comfortable just replacing it with an original (new/used) OEM unit.

From the video can anyone tell me has the centre section been replaced as well or just the rear section?

https://www.dropbox.com/s/p6vi8yr7eoo0wc7/Video 31-03-2020%2C 20 10 52.mov?dl=0

The cost of replacing the middle and rear sections will be a lot. When I had my problems to replace the full exhaust from engine backwards was £3200. IT is Lexus after all.

If you are interested I do have a second hand centre section that I bought but did not use. It was off a 2007 IS250 with 54k miles. Having said that I suspect the rear section will impact the noise more that the middle section.

rob250 · April 1, 2020

I've managed to find a rear section OEM.

Is your center section OEM Ken?

Vintagesixtysix · April 1, 2020

Just a quick question from the pics...

Is that wire cradle standard on an original exhaust set up?

rob250 · April 12, 2020

No idea - does anyone else know?

rich1068 · April 12, 2020

Can I just point out that SS systems don't have to drone. The cat back system I had fitted by Tony Banks is lovely and quiet. That's what I asked for and that's what I got. I think it's down to the expertise of the fitter/fabricator.