Exhaust resonance when lifting throttle – cure?
Discussion
I had the ACT big bore full exhaust system fitted not long back, as I wanted a slightly quieter sound for normal cruising.
It is quieter, but once the exhaust gets hot, I still get terrible resonance in the cabin, usually when lifting off.
I have a feeling that the larger diameter is now touching the underside of the car in certain circumstances, causing the drone.
Has anyone had similar, and if yes, what can be done to cure it?
Cheers
It is quieter, but once the exhaust gets hot, I still get terrible resonance in the cabin, usually when lifting off.
I have a feeling that the larger diameter is now touching the underside of the car in certain circumstances, causing the drone.
Has anyone had similar, and if yes, what can be done to cure it?
Cheers
starlight225 said:
Another thought, how are your engine mounts?
They are fine, they were sorted when I had the 4.3 upgrade.I think I'll ask Dom to have a look when it goes in for its service next week.
I did think about wrapping all of the exhaust in exhaust wrap - but I can't get to the underside of my car, and I'd probably mess it up anyway...
steveT350C said:
Hi Chris,
So lifting off throttle causes problem?
Sounds similar to a problem I had:
An analogy is an issue I had re plumbing in my house....
Every time I hit the main pipe up in the loft with a heavy book, the boiler cut out. I spent ages on the internet trying to find out what was going on. I might as well have trained up to be a plumber myself with the amount of research I did.
Then I suddenly worked it out;
Don't lift off the throttle
So lifting off throttle causes problem?
Sounds similar to a problem I had:
An analogy is an issue I had re plumbing in my house....
Every time I hit the main pipe up in the loft with a heavy book, the boiler cut out. I spent ages on the internet trying to find out what was going on. I might as well have trained up to be a plumber myself with the amount of research I did.
Then I suddenly worked it out;
Don't lift off the throttle
Edited by steveT350C on Thursday 21st May 21:45
Thanks!
shep1001 said:
Check the cans/back box is not touching the diffuser and/or the body in the recess where the exhaust sits
The back box is pretty close to both the diffuser and exhaust/number plate heat shield.I may buy some self adhesive thick heat shield to put onto the back of the of number plate shield and diffuser. Of course I never had this problem with the small separate bean cans.
Edited by chris watton on Friday 22 May 19:22
mr lock pick said:
Chris
Have a chat with Mr Clive Ford, he may be able to offer you a few solutions. Many of us have experience droning, including myself.
By the way I love all your post as we all get to learn a lot, however I thought I could moan, I have officialy voted you No. 1 EXPERT PH moaner 2014-2015.
Keep all the mods coming and the post fella.
Moaner! Do I? Gulp - didn't realise - am I turning into Alf Garnet in my old age, and too senile to even know it! Have a chat with Mr Clive Ford, he may be able to offer you a few solutions. Many of us have experience droning, including myself.
By the way I love all your post as we all get to learn a lot, however I thought I could moan, I have officialy voted you No. 1 EXPERT PH moaner 2014-2015.
Keep all the mods coming and the post fella.
starlight225 said:
Hi Chris, by some strange quirk of fate I currently have my complete system off the car. Just refitting cats after the car came decatted. Have found that my system was a big bore system having bought a pair of standard cats, but that's a whole different story. With it off I noticed that the system was rubbing on the rear diffuser and on the chassis under plate in front of the diff. There are some adjustable L shaped hanger brackets that were effectively set too low causing all the contact. Also you could put a few washers between the chassis and the cross plate to give a bit more clearance
Cheers I too had the larger bore Tuscan S/Sagaris OEM cats fitted.I am taking the car to Powers on Tuesday for its post run in service, I shall ask Dom if he can sort the underside for me. I am pretty sure I can sort out the back box by fixing thick heat shield on the top of the rear diffuser and number plate shield.
Shouldn't have to though - just having the new system fitted cost me £360 in labour! They must see me coming...
Took the Tam out for a good run yesterday - and I still get the horrible droning resonance when lifting off (when up to temp)- making the whole car seemingly vibrate, ruining an otherwise fantastic experience.
I will buy new hangers and perhaps wadding to see if that helps, and self adhesive heat shield for the inside of the rear exhaust shield and diffuser, as the large ACT back box it very close to both.
On an unrelated topic, my wife had her first go in the Tam since the upgrades last night - too afraid to put her foot down, so everything was overtaking, even old Rovers ...
I will buy new hangers and perhaps wadding to see if that helps, and self adhesive heat shield for the inside of the rear exhaust shield and diffuser, as the large ACT back box it very close to both.
On an unrelated topic, my wife had her first go in the Tam since the upgrades last night - too afraid to put her foot down, so everything was overtaking, even old Rovers ...
gacksen said:
can you get the car on ramps ?
if yes second picture check the clearances of the exhaust between the chassis rails.
in case it drops on the protector plate you have some sort of metallish sound that is
very unique. easiest way would be get it up the ramp rev it till it drones while another person
takes a look from below.
I have no access to ramps if yes second picture check the clearances of the exhaust between the chassis rails.
in case it drops on the protector plate you have some sort of metallish sound that is
very unique. easiest way would be get it up the ramp rev it till it drones while another person
takes a look from below.
Would it help if I wrapped parts of the exhaust close to the chassis rails, and perhaps add spacers to the protector tray, or wrap that area of the exhaust too?
OK, I bought 30 metres of exhaust wrap and have now wrapped as much as the two exhausts as I can (I never want to do that again!). I have also stuck self adhesive heat shield to the top surface of the under-car exhaust guard and the rear diffuser and rear exhaust guard.
I bought this:
https://www.merlinmotorsport.co.uk/p/exhaust-wrap-...
This:
https://www.merlinmotorsport.co.uk/p/thermo-tec-hi...
These:
https://www.merlinmotorsport.co.uk/p/stainless-ste...
And this:
https://www.merlinmotorsport.co.uk/p/zircoflex-ii-...
The only part of the exhaust I couldn't do is near the front, just past the cats where the pipes are on top of one another, rather than side by side. What are the chances it's the part I can't get to that's causing the problem!
Will try it out tomorrow morning, I really hope I've cured it..
I bought this:
https://www.merlinmotorsport.co.uk/p/exhaust-wrap-...
This:
https://www.merlinmotorsport.co.uk/p/thermo-tec-hi...
These:
https://www.merlinmotorsport.co.uk/p/stainless-ste...
And this:
https://www.merlinmotorsport.co.uk/p/zircoflex-ii-...
The only part of the exhaust I couldn't do is near the front, just past the cats where the pipes are on top of one another, rather than side by side. What are the chances it's the part I can't get to that's causing the problem!
Will try it out tomorrow morning, I really hope I've cured it..
Fish said:
It does look close to the under shield, I just had an ACT fitted and the under shield was packed off the chassis rails a little more than yours. All you have to do is unbolt and add washers to increase clearance...
Hope that helps..
Cheers James. I did that, added a couple more washers to bring the tray down a little more. The exhaust is also wrapped quite well in that area.Hope that helps..
knowing what I know now, I should have wrapped the whole system before it was fitted - I ache like hell now, trying to contort myself under the car!
m4tti said:
Resonance, if it is that rather than drone, is usually set up by vibration. It's probably tricky now you've wrapped it, but tapping along the length of the exhaust may show you where that vibration is originating from.
I did actually try that, but nothing. It only happens when the exhaust is hot, when it expands.OK, just got back from a 40 minute drive, and it's worked, no more horrible vibrations coming through the cabin! Phew!
Although I think I made a mistake in adding more Zircoflex self adhesive heat shield on the bulkhead, next to the manifolds - the glue was smoking like hell when I got back! Should I take it off?
Although I think I made a mistake in adding more Zircoflex self adhesive heat shield on the bulkhead, next to the manifolds - the glue was smoking like hell when I got back! Should I take it off?
BuzzBillsberry said:
Just be aware Chris that wrapping the exhausts moves the heat down the system so that'll be the rear boxes so you might find your boot rather warm so don't put any perishables in there or cold drinks. When I was running the standard silencer . The heat melted/distorted the rear number plate.... Even when I pulled the rear exhaust shield out it was still pretty hot
Buzz
I remember seeing a pic of that Buzz - it was with that in mind I bought some more Zircotec heat shield and added it to the inside of the rear exhaust shield and the top of the diffuser, where the rear box sits pretty darn close.Buzz
My rear number plate is stuck on, not screwed, so I'll have to watch that. It was Ok with the separate bean cans, but the ACT rear box is pretty substantial...
Just took a couple of pics of some of the wrap - it definitely works and is now a lot quitter in the cabin. As I mentioned, I couldn't wrap it all, most notably the pipe that is located above the lower one near the front, but I managed to get most of it. As also mentioned, not the best job to do when the exhausts are in situ!
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