Exhaust grounding, what can be done?

Exhaust grounding, what can be done?

Author
Discussion

greenranger

Original Poster:

989 posts

105 months

Saturday 3rd June 2017
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This has been an ongoing problem.. exhaust grounding! Soon as there's a rounded speed bump there's just no chance my S will go over it without scraping. It seems to be the middle box that catches every time.

Im just considering removing the middle box completely running the pipes straight through an chucking two 3" diameter silencers on the back to compensate for the noise.. Has anybody done this or is it just something I have to endure?

I guess I could jack the suspension up abit but I dont want the car to sit too high an look odd, it's just about right now where it is now.

Cheers
Steve

GreenV8S

30,150 posts

283 months

Saturday 3rd June 2017
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Is it definitely the middle box? I seem to remember my S2 was always grounding the front of the exhaust. The clamps may be a low point. If so, replacing those hideous U bolt clamps with t-bolt clamps can gain you a crucial half inch or so of extra clearance.

If it's grounding in the middle, what's the ground clearance on flat level ground? Maybe you have just got the suspension a bit too low.

mentall

453 posts

129 months

Saturday 3rd June 2017
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When I bought it, my S3C had 26mm clearance under the ends of the U-bolts!

The engine mountings had collapsed: also, the sump was down on the ARB.

New mounts and stainless cups (Burton Power) cured it: now clearance is around 40mm.

The next problem was interference between the bonnet and the alternator fan and idle speed valve! Heightwise, there's not much room in there: TVR must have had some state-of-the-art modelling software to get it just right. Or perhaps..............

greenranger

Original Poster:

989 posts

105 months

Saturday 3rd June 2017
quotequote all
Thanks for the replys gents, I'm not 100% sure but its not the tail pipes thats for sure.. I'll have a look underneath an see if there's U-bolt clamps on I'm pretty sure there is to be honest, I bet you its them I can hear scraping.

v8s4me

7,234 posts

218 months

Saturday 3rd June 2017
quotequote all
mentall said:
....Heightwise, there's not much room in there: TVR must have had some state-of-the-art modelling software to get it just right. Or perhaps..............
Perhaps they used THIS Well it is a type of "soft-ware" laugh

AutoAndy

2,265 posts

214 months

Saturday 3rd June 2017
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V6 S's ground.

Mostly it is the clamp under the sump where the hockey sticks attach to the main exhaust.....it just is....

Best solution is to increase suspension hardness (new springs, and/or increase damper resistance)...also can changes from U bolts to single bolt clamps, like the ones from Mikalor.

Welcome to S ownership ....the rest is all just fun
wink

Niiige

640 posts

168 months

Saturday 3rd June 2017
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They all do that !!

And Treat the exhaust as a consumable item.

magpies

5,129 posts

181 months

Saturday 3rd June 2017
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mine grounds on speed bumps and has flattened the exhaust just before the centre box - I'm fitting sacrificial strips

my S is lower than most

glenrobbo

35,077 posts

149 months

Sunday 4th June 2017
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Steve,
Duncan Pittaway's trials S doesn't have any ground clearance issues...


I think he lowered his suspension setup to give just 10" ground clearance because originally he had set it a tad too high. smile

h271mbk

42 posts

98 months

Sunday 4th June 2017
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I have just that on my S3. Straightnthrough, with two 12" long 31/2" diameter cherry bomb type silencers at the rear. I also added a 2" H pipe at the end of the J pipes. Sounds awesome, burbles along at low revs, pops and bangs on over-run, ear splitting on full chat. However, it does drone around 50 to 60mph, but only with the roof on which I rarely do.
N

greenranger

Original Poster:

989 posts

105 months

Sunday 4th June 2017
quotequote all
I know its a common thing but just a little embarrassing scraping the exhaust at classic car shows/gatherings etc, its those speed bumps that run all the way across that get me.

Will have a look at the clamps & certainly consider removing the centre box running pipes straight through but definitely need to tone down the noise, ears ringing & headache on a long journey is not so great..

cheers
Steve
grey/greenhulk/greenranger biggrin

GreenV8S

30,150 posts

283 months

Sunday 4th June 2017
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Somebody recently posted a picture of a custom exhaust that seemed to go round the sump rather than under it - I wonder whether that helps the speed hump issue.

h271mbk

42 posts

98 months

Sunday 4th June 2017
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If you're going to have an exhaust made to fit, consider rectangular section tube; replace the J pipes and the run under the car with rectangular changing to round pipes at the back. This'll save at least an inch.
N

greenranger

Original Poster:

989 posts

105 months

Sunday 4th June 2017
quotequote all
Cheers gents, going to look into this more then, will speak to RJ performance exhausts to see if they can whip something up. It makes me pull a face like I'm chewing on a sour winegum when I hear the metal scrape

Spanish S2

340 posts

131 months

Sunday 4th June 2017
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Just had a full exhaust including manifold´s in stainless supplied and fitted by RT Racing in Sheffield and i don´t have any issue´s with speed bump´s, may´be it´s because i drive over them gently.biggrin

DamianS3

1,803 posts

181 months

Sunday 4th June 2017
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Are you still running the 60 profile tyres some change to 55 which reduces clearance a little bit..?

Damian S3

greenranger

Original Poster:

989 posts

105 months

Thursday 13th July 2017
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Well after the peak district nightmare with exhaust grounding & the exhaust clamp from hockey sticks to exhaust denting the pipe inwards on the one side after the low bolts caught the speed bump.. Ive had a go at trying to spin the exhaust clamps round abit so the bolts arent hanging low & tightening up the exhaust mounts.

Got the 55 profile tyres on damian, regarding my suspension.. i can get my fist in the gap between the wheel arch to tyre with ease & looks about right on the eye. Hopefully maybe another 1/2 inch up on suspension should do the job now, feel like i have to preplan my rout anywhere now with these speed bumps..




Edited by greenranger on Thursday 13th July 18:06

greymrj

3,316 posts

203 months

Thursday 13th July 2017
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Did a bit of work on this issue myself.
It is worst on the S1.
I have a picture of the complete system in a TVR S parts book. The rectangular box inside the chassis is not the primary silencing, it is the oval section in front of that which does the main absorbtion. If the car exhaust is very noisy it is more likely to be the loss of sound absorbant material from that section.
If it is 'buzzing' a lot then it could be that contact between the road and that oval has pushed the oval up more than about 5mm, in which case it will come in contact with the two perforated pipes which carry the exhaust through that section. Made a really enoying buzz on mine, worst at 30mph!

Different places to catch dependent on whether it is something like a speed bump of more dynamic like a small 'yump'!

First place is downpipe to front of exhaust. That needs to be as tight as possible under the sump, (yours looked to be a good bit below?) if the coupling hasnt dented the sump it isnt close enough! There is 1mm space on mine, just enough (and I have checked) to stop the exhaust rubbing through the sump!. You need to use Mikelor clamps or similar with a flat section at the bottom, exhaust clamps are a no-no. Put the mikelor clamp bolts at the sides. I even changed the Mikelor bolt to a stainless allen bolt to save 2mm. The old fashioned exhaust clamps are not only several mm thicker, they tend to catch and cause quite a linear force down the exhaust and do cause other damage.
It is of course no point in getting close to the sump if that is too low. Old soggy engine mounts will probably drop the sump 5-10mm. Several people have not only changed the rubbers but fitted lifting spacers from Burtons. Think Glen went up 10mm but I hope he can confirm that. I believe clearance above the top front of the bellhousing is the issue. I seem to remember someone saying they had clearance issues with the bonnet if they went too high (I dont as I have the V8 bonnet)

Second place is the very front of the oval section, obviously the higher the front connection the higher this is. I did however weld sacrificial strips on mine, doesnt help the clearance but it has stopped the front corner 'catching'.
Third place seems to involve a hit mid way along that oval section between the down pipe and the rectangular box, and is more likely when bouncing on a hump. That causes internal damage to the silencer.
The square box shouldnt be the problem in most circumstances. However it does need to be up into the chassis as far as possible and if the mountings are incorrect it wont be. The pipes at front and back of the box should only just clear the chassis cross rail. Those mountings should be a very dense rubber and not the squashy rubber like that used on Mini exhaust mounts. If it is right there will be very little play in the square box.

If the S1 has lower profile tyres, unless the wheel itself compensates correctly, it will just touch more.
If the suspension is lowered at all, or soft, it will touch more. I tend to run mine a little soft, better for the back most of the time but it does bounce a bit more so the sacrificial strips get sacrificed!!

greymrj

3,316 posts

203 months

Thursday 13th July 2017
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Forgot something!
Banging the front of the pipe hard down isnt good for the manifolds either! The original cast manifolds are getting hard to find now. The pipe to manifold flange isnt that robust and people have had them crack. I took the studs out and drilled to thread depth, fitted one size down stainless allen bolt with washers and double nuts* to give just that little bit of give if there is a big impact. One impact (hump back bridge on a minor road in the yorkshire dales!) actually bent a bolt but didnt damage the casting or break the exhaust seal.

(*Dont be a silly boy like me and use a nylock, the melted nylock was a pain to get off the pipe)

phillpot

17,105 posts

182 months

Thursday 13th July 2017
quotequote all
greymrj said:
I have a picture of the complete system in a TVR S parts book.
I had a quick look under Steven's car at Barn Farm, it's not a standard exhaust.

His photo's are a bit dark but there is a normal silencer under there, i.e. the pipes enter and exit along is centre line whereas on a genuine system the pipes all attach off centre, lower down to the silencers, so nothing hangs lower than the pipes, make sense?