Let's get back to booming V6 exhausts.

Lord of Hog · 1st April 2020, 09:28

This is rapidly becoming the bane of my life entailing many hours underneath my X-plate 2.5 cursing the exhaust, the car and life in general.

The factory fitted rear box disintegrated at around 90k and I've spent the last 12000 miles fitting and removing a succession of replacement boxes all of which produced a loud resonating boom between 1200 and 2400 revs, louder than the engine in many cases which is a shame when the engine sounds so nice.

I've tried fitting additional soundproofing to the boot and that has improved things a little but I'd love to have some suggestions as to how to fix it.

Is it resonance in the boot/rear bumper area?
Is it the result of the pipes being too short and the bumper magnifying the sound?
Are the hangers too short (and if so how to fit longer ones while avoiding the pipe-knocking-on-the-crossmember sound)?

To be quite honest I'm running out of ideas so any suggestions would be gratefully accepted.

75 tinkerer · 1st April 2020, 20:04

I hate that resonance, it's low frequency so the usual sound proofing probably won't help much, it might be transmitted through the body shell.

My V6 has an 'after market cat' and Dave in Fencehouses suggested an original might be quieter. When he reset the engine warning light he suggested it might be caused by the cat or dodgy fuel. But thinking about it I did fill up in Liverpool.

Pete

stocktake · 1st April 2020, 21:25

How about trying something like this?

https://www.ebay.co.uk/itm/4-x-14-CL...cAAOSwvT5dW6sv

KWIL · 2nd April 2020, 08:41

Simple really, the aftermarket boxes are just that, something that fits but does not really MATCH the original design requirements, i.e. size of internal pipes and exactly the same construction.

Had a similar problem a few years ago when the company car leasing company insisted (for £ reasons) that an aftermarket final box had to be fitted. It was awful, after a bit of argy bargy they agreed to have the MGR parts fitted, all was returned to normal silence.

SD1too · 2nd April 2020, 09:51

Quote:

Originally Posted by KWIL

Simple really, the aftermarket boxes are just that, something that fits but does not really MATCH the original design requirements, i.e. size of internal pipes and exactly the same construction.

A forum member was in the process, last year I think, of commissioning a replica of the original MGR clamshell KV6 rear silencer/tailpipe. An excellent initiative but as is so often the case, it's all gone very quiet.

Simon

Lord of Hog · 3rd April 2020, 06:04

Thanks for the replies so far. Purely from a cost point of view, if the answer is to fit a factory-spec rear box or some sort of resonator to the existing ageing system then I may as well wait until the world returns to some sort of normality and have the stainless cat-back that I was quoted around £300 for. When I had one from the same people for the Outlander I was able to specify what sort of exhaust note I wanted and they removed/moved resonators and changed tailpipes accordingly.

However, now I'm obliged to work from home half the time I hope to have the opportunity to continue playing with it. So if I stumble across any undiscovered answers I shall let everyone know.

rab60bit · 6th April 2020, 13:21

Quote:

Originally Posted by SD1too

A forum member was in the process, last year I think, of commissioning a replica of the original MGR clamshell KV6 rear silencer/tailpipe. An excellent initiative but as is so often the case, it's all gone very quiet.

Simon

I think that was Saga Lout (Wigan)

marinabrian · 6th April 2020, 21:55

Quote:

Originally Posted by SD1too

A forum member was in the process, last year I think, of commissioning a replica of the original MGR clamshell KV6 rear silencer/tailpipe. An excellent initiative but as is so often the case, it's all gone very quiet.

Simon

And that very exhaust is fitted to my wife's car as we speak, and it it superb

I took no notice of the people who thought £185 was an expensive price to pay to be a "guinea pig"

Here is the write up, read it and weep gents, this exhaust is the exhaust to end exhausts in terms of quality and quietness

LINK

Brian

P.S. it is of course a V6 pipe, I just chose to fit it to a diesel, and if you fancy one, then take a look HERE

edwardmk · 3rd April 2020, 22:43

Quote:

Originally Posted by Lord of Hog

This is rapidly becoming the bane of my life entailing many hours underneath my X-plate 2.5 cursing the exhaust, the car and life in general.

The factory fitted rear box disintegrated at around 90k and I've spent the last 12000 miles fitting and removing a succession of replacement boxes all of which produced a loud resonating boom between 1200 and 2400 revs, louder than the engine in many cases which is a shame when the engine sounds so nice.

I've tried fitting additional soundproofing to the boot and that has improved things a little but I'd love to have some suggestions as to how to fix it.

Is it resonance in the boot/rear bumper area?
Is it the result of the pipes being too short and the bumper magnifying the sound?
Are the hangers too short (and if so how to fit longer ones while avoiding the pipe-knocking-on-the-crossmember sound)?

To be quite honest I'm running out of ideas so any suggestions would be gratefully accepted.

I have exactly the same resonance issue. My ZT-T was fitted with a very nice s/s Cybox cat back exhaust by the previous owner which resonated too much for us, so I had a local garage which specialises in S/S exhausts look at it. They recommended to remove it and go back to standard, which I did. The reduction was unfortunately not that significant. (I don't know what they fitted to be fair, but it was nice and shiny). Their comment was it was the correct system and should quieten down after a few hundred miles lol.
I still have the as new s/s Cybox system, but am now actively looking for the source of the resonance. I think the problem is the wheel well, which is resonating badly at 1400-2200 revs under load. The exhaust bracket on mine is welded to the passenger side of the wheel well, and even with a new rubber support, I feel it's not decoupling the exhaust enough from the side of the wheel well. With everything out of the wheel bay, tapping it really does boom like a steel drum. Play from engine mountings may also be another factor. but I haven't properly checked them yet. I'm going to clean up and paint the wheel well properly and then strategically supplement the existing sound deadener strips with Noico 2mm butyl sound deadener. I've a load of other stuff ongoing, so won't be able to report on results for a while until the car is back on the road.

Blink · 4th April 2020, 09:45

I've got a new Bosal 278-967 which didn't produce any resonation when I tested it on the original factory system (minus its original back box). I enlarged the Bosal inlet pipe a bit so that it fitted the MGR centre pipe, which I'd cut off at the bend.

In the end I didn't use the Bosal because I decided to replace the original centre section as well and the (now enlarged) Bosal doesn't fit the new Klarius centre.

Btw, the Bosal is oval with twin outlets. It has a separate mounting bracket similar to the MGR original.

1st April 2020, 09:28	#1
Lord of Hog Gets stuck in Rover 75 2.5 V6 in Wedgwood Blue Join Date: Dec 2015 Location: Felbridge, East Grinstead Posts: 982 Thanks: 250 Thanked 294 Times in 206 Posts	Let's get back to booming V6 exhausts. This is rapidly becoming the bane of my life entailing many hours underneath my X-plate 2.5 cursing the exhaust, the car and life in general. The factory fitted rear box disintegrated at around 90k and I've spent the last 12000 miles fitting and removing a succession of replacement boxes all of which produced a loud resonating boom between 1200 and 2400 revs, louder than the engine in many cases which is a shame when the engine sounds so nice. I've tried fitting additional soundproofing to the boot and that has improved things a little but I'd love to have some suggestions as to how to fix it. Is it resonance in the boot/rear bumper area? Is it the result of the pipes being too short and the bumper magnifying the sound? Are the hangers too short (and if so how to fit longer ones while avoiding the pipe-knocking-on-the-crossmember sound)? To be quite honest I'm running out of ideas so any suggestions would be gratefully accepted. __________________ Conformity is not morality. Consensus is not truth.

1st April 2020, 21:25	#3
stocktake Vis Whiz Rover 75 2.5 auto Saloon Join Date: Jun 2007 Location: LEEDS Posts: 20,591 Thanks: 2,057 Thanked 3,056 Times in 1,621 Posts	How about trying something like this? https://www.ebay.co.uk/itm/4-x-14-CL...cAAOSwvT5dW6sv __________________ Dave... Lost a few stones and a Gall Bladder and part of a bile duct and all of my dignity in the suppository incident

3rd April 2020, 06:04	#6
Lord of Hog Gets stuck in Rover 75 2.5 V6 in Wedgwood Blue Join Date: Dec 2015 Location: Felbridge, East Grinstead Posts: 982 Thanks: 250 Thanked 294 Times in 206 Posts	Thanks for the replies so far. Purely from a cost point of view, if the answer is to fit a factory-spec rear box or some sort of resonator to the existing ageing system then I may as well wait until the world returns to some sort of normality and have the stainless cat-back that I was quoted around £300 for. When I had one from the same people for the Outlander I was able to specify what sort of exhaust note I wanted and they removed/moved resonators and changed tailpipes accordingly. However, now I'm obliged to work from home half the time I hope to have the opportunity to continue playing with it. So if I stumble across any undiscovered answers I shall let everyone know. __________________ Conformity is not morality. Consensus is not truth.

1st April 2020, 20:04	#2
75 tinkerer Regular poster Rover 75 Tourer Join Date: Mar 2013 Location: Darlington Posts: 95 Thanks: 12 Thanked 10 Times in 9 Posts	I hate that resonance, it's low frequency so the usual sound proofing probably won't help much, it might be transmitted through the body shell. My V6 has an 'after market cat' and Dave in Fencehouses suggested an original might be quieter. When he reset the engine warning light he suggested it might be caused by the cat or dodgy fuel. But thinking about it I did fill up in Liverpool. Pete

2nd April 2020, 08:41	#4
KWIL Precise Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013 Location: Fleet Posts: 2,954 Thanks: 630 Thanked 617 Times in 480 Posts	Simple really, the aftermarket boxes are just that, something that fits but does not really MATCH the original design requirements, i.e. size of internal pipes and exactly the same construction. Had a similar problem a few years ago when the company car leasing company insisted (for £ reasons) that an aftermarket final box had to be fitted. It was awful, after a bit of argy bargy they agreed to have the MGR parts fitted, all was returned to normal silence.

4th April 2020, 09:45	#10
Blink Posted a thing or two Rover 75 Saloon Join Date: Apr 2019 Location: Under the car Posts: 1,840 Thanks: 210 Thanked 244 Times in 221 Posts	I've got a new Bosal 278-967 which didn't produce any resonation when I tested it on the original factory system (minus its original back box). I enlarged the Bosal inlet pipe a bit so that it fitted the MGR centre pipe, which I'd cut off at the bend. In the end I didn't use the Bosal because I decided to replace the original centre section as well and the (now enlarged) Bosal doesn't fit the new Klarius centre. Btw, the Bosal is oval with twin outlets. It has a separate mounting bracket similar to the MGR original.