Exhaust design.

Technical Area for all the problems you have in the garage
Post Reply
User avatar
peterc
T289R Member
T289R Member
Posts: 2041
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Exhaust design.

Post by peterc »

Out of interest does anyone have a compensator or flexible in the early part of their exhaust system to allow for engine movement. When I rerouted my exhaust to run alongside the door cills I worked on the basis of Gerry’s original system and just had a fair length of pipe before the first support.
I am just about to change the two bottom bends for St Stl versions due to the inevitable Sheffield worm and wondered whether I should be trying to incorporate something to protect the manifold. It crossed my mind that the movement would be increased being further away from the centreline of the car.
Does anyone bother?
Peter C
Last edited by peterc on Sat Jul 18, 2020 8:04 am, edited 1 time in total.
User avatar
StewbieC
T289R Committee
T289R Committee
Posts: 1356
Joined: Mon Oct 13, 2008 12:50 pm
Location: out in the sticks, Shropshire

Re: Exhaust design.

Post by StewbieC »

Hi Peter,
StSt, in particular 304, will be slightly more brittle than Mild Steel but nothing to worry about.
There's no need in my mind to fit a flexible compensator. I've never heard of one being fitted to a Hawk and I've never heard of an exhaust failing owing to material fatigue. You'd also need to consider a fixed mount of the exhaust to the chassis at that end if you fit a flexible compensator.
The cheapest solution would be to get some replacement Mild steel bends and use some high heat black paint on them. It can always be touched up before its Winter Slumber. I had mine Ceramic Coated (waste of money) as they have been blasted to death by stone chips and have plenty of surface rust pits.
________________________________________________
Stu
Hawk 289, 66 Mustang Fastback with a 289 maximum smiles per mile..
User avatar
peterc
T289R Member
T289R Member
Posts: 2041
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Re: Exhaust design.

Post by peterc »

Thanks Stuart. At present I have two St Stl bends on order which are cheaper than Gerry’s CS versions. I take your point on the more brittle nature of the 304. If I were to add the flexibles they have to be in a straight run and that would be nearer to the first box which is well supported from the chassis outrigger.
I think for now I will continue without. It’s worked well enough for years.
Peter C
SiJackson
Posts: 116
Joined: Thu Sep 15, 2016 3:08 pm
Location: Northumberland, UK

Re: Exhaust design.

Post by SiJackson »

I have slip joints on mine, with springs to hold the pipes to the down pipes, rather than clamps. This allows a little movement and expansion. Although I'm yet to get any serious use out of the car (cheers DVLA) i did the same on my series Land Rover V8 and thats worked out fine over the years
monster7
Posts: 79
Joined: Fri Jul 01, 2016 5:11 pm

Re: Exhaust design.

Post by monster7 »

SS Compensator...worth every cent
Image
User avatar
peterc
T289R Member
T289R Member
Posts: 2041
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Re: Exhaust design.

Post by peterc »

Yes, I think having a flex is a good idea but there is just one problem with your installation. The flex is too close to the bend. Turbulence from the bend will affect the longevity of the flex. It should be positioned on a longer straight section. Wasn’t there any info with the flex reference the positioning of the flex.
Peter C
monster7
Posts: 79
Joined: Fri Jul 01, 2016 5:11 pm

Re: Exhaust design.

Post by monster7 »

peterc wrote: Wed Jul 29, 2020 9:05 pm Yes, I think having a flex is a good idea but there is just one problem with your installation. The flex is too close to the bend. Turbulence from the bend will affect the longevity of the flex. It should be positioned on a longer straight section. Wasn’t there any info with the flex reference the positioning of the flex.
Peter C
Hy Peter, not sure which turbulences you are refering to? From the exhaust gas stream?
However, the flex is welded to the part where the "bend" is already straight (may hard to see in the pic). It is additionally the only place found to work as i had to include the extension piece to move from 2.5'' to 3''.
Basically, the compensator is of high quality and have mainly to deal with the engine movement. No positioning info was provided.
User avatar
peterc
T289R Member
T289R Member
Posts: 2041
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Re: Exhaust design.

Post by peterc »

Hi Monster, profuse apologies for not posting a reply to your query earlier. Not sure why I missed it.
In my design years I always remember falling foul of the lack of space around compressor set ups and where to put the flexible. I was thinking in terms of the pressure wave coming from the engine and affecting the bellows of the flex.
I appreciate that you don’t have much of an option as space is so limited so I guess it will be a case of just keeping an eye on it when you service the car. Depending on how hard you use the car it may well last for years.
Peter C
monster7
Posts: 79
Joined: Fri Jul 01, 2016 5:11 pm

Re: Exhaust design.

Post by monster7 »

No worries and thanks for your reply!
Best
Ronald
Post Reply