cd.thomson
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| posted on 23/12/08 at 10:56 AM |
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underslung exhaust systems
Just spitballing here, but I wanted to check with the guys in the know first.
You may have seen that I'm pressing for SVA, but this has two possible outcomes I think - high levels of expense or low levels of quality. I
imagine that the result will end up being a vehicle which is noticeably more expensive than intended and not the car I hold in my minds eye.
So..onwards.. lets say I bite the bullet and plod through into IVA. Aside from the extra costs of the test it is also possible that a sideslung
exhaust will make passing impossible.
I know some owners have come up with clever ways to undersling their exhaust systems and I was wondering if they could talk me through it? My car
seems low enough already without an exhaust pipe sitting proud underneath it..
[Edited on 23/12/08 by cd.thomson]
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Macbeast
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| posted on 23/12/08 at 11:12 AM |
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My first thought, which I haven't developed yet, was to make a protective cover for the whole external system, somewhat in the way some people
put perf jacket round the silencer box.
Unfortunately, I think it would probably fall off on the way home 
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cd.thomson
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| posted on 23/12/08 at 11:17 AM |
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quote:
Originally posted by Macbeast
My first thought, which I haven't developed yet, was to make a protective cover for the whole external system, somewhat in the way some people
put perf jacket round the silencer box.
Unfortunately, I think it would probably fall off on the way home
I had considered this, but a cage or box around the ENTIRE unit (including headers etc) would no doubt fail IVA due to its edges. Also, how could I
attach it without damaging my body panel, therefore need a replacement after it does fall off.
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nstrug
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| posted on 23/12/08 at 11:27 AM |
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Has anyone just considered wrapping the entire exhaust system?
Nick
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cd.thomson
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| posted on 23/12/08 at 11:30 AM |
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quote:
Originally posted by nstrug
Has anyone just considered wrapping the entire exhaust system?
Nick
the IVA section that deals with the problem states that the exhaust system must not be exposed and be able to burn pedestrians I believe. Wrapping it
will still leave the system exposed in the sense that if people touch it, even though they're not touching the metal, they will injure
themselves.
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jabbahutt
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| posted on 23/12/08 at 12:00 PM |
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I have an idea which would sort the problem, bear with me before laughing.
How about a cover which runs the entire length of the exhaust and is tapered at the top angling sown to a curve that goes under the exhaust.
It could be attached top and bottom using button head bolts into rivnuts that would already be thre for securing the side panel top and bottom instead
of sikalflex.
There are plenty of skillful people on here who work with fibreglass and it wouldn't have a single edge to pose a problem.
looking it at from the end it would look like a right angled triangle with the bottom corner opposite the 90 deg as a curve instead of a corner.
Once SVA's remove it and refit the button heads back to hold the side panel.
I hope that makes sense as it solves the problem without and problems of how to attach.
does anyone see a proble with the idea?
Nigel
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jabbahutt
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| posted on 23/12/08 at 12:08 PM |
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quick section sketch, forgive my drawing skills
 
exhasut cover
the ends could be rounded back towards the car with just a hole for the exhaust fumes edged with SVA trim
If that doesn't make sense post your questions and i'll attempt to explain better.
Nigel
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cd.thomson
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| posted on 23/12/08 at 12:13 PM |
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I like this Jabba, what would you make the rather odd shape from?
Do I understand it right that the second image is as seen if you were looking from the rear towards the front of the car?
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PAUL FISHER
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| posted on 23/12/08 at 12:16 PM |
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The best solution Ive seen is by "bigrich" on his Mac1,with the exhaust running down the transmission tunnel,then exiting out of the
rear,utilising the oringinal headers and twin bike silencers out of the rear
 
Rescued attachment 2exhausts BIG RICH.jpg
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Guinness
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| posted on 23/12/08 at 12:21 PM |
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As far as I can see it there are two possible solutions for 7's.
1. Option 1 for BEC's only, keep the headers inside the chassis rails, drop down and forwards, put the joints behind the rad, but in front of
the engine, 90 bend, then put the can in beneath the steering column, with a side exit just in front of the drivers footwell. I think the
"modern" styled 7 that toook aaaagggggeeeessss to come to production has a similar arrangement, but with the can mounted sideways behind
the rad, exiting just behind the front wheel.
2. For CEC's who aren't going to have the space, I think it's going to mean making the centre tunnel a bit bigger, and running the
pipe down the middle of the car. The silencer then goes across the back of the car. Will require some adjustment to the location of the fuel tank!
Some ventilation to the centre tunnel and stopping using plastic to form the internal panels.
I liked Bigrich's system on his MAC1.
Cheers
Mike
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jabbahutt
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| posted on 23/12/08 at 12:24 PM |
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Yep it's a very crude section through the cover from either front or rear.
If it's a temporary structure I thought make ribs from plywood similar to a model aircrafct fuselage and cover with thin ply secured top and
bottom with bolts and painted to at least make it look semi permenant.
alternatively someone like with the suitable fibreglassing skills or even the manufacturer could start making model specific covers.
I don't know how ply would stand up to the heat from the exhaust, fibreglass may be a better solution but it would cover the entire system with
no contactable edges.
Nigel
[Edited on 23/12/08 by jabbahutt]
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fesycresy
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| posted on 23/12/08 at 12:34 PM |
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Are we 100% sure that this is going to be passed ?
I'd wait until it's confirmed before doing anything.
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
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Miks15
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| posted on 23/12/08 at 12:35 PM |
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quote:
Originally posted by Guinness
1. Option 1 for BEC's only, keep the headers inside the chassis rails, drop down and forwards, put the joints behind the rad, but in front of
the engine, 90 bend, then put the can in beneath the steering column, with a side exit just in front of the drivers footwell. I think the
"modern" styled 7 that toook aaaagggggeeeessss to come to production has a similar arrangement, but with the can mounted sideways behind
the rad, exiting just behind the front wheel.
Im going to give this ago, ill have a bit more space because im not using conventional bodywork so im going to have my exhaust no further back than
the engine and it will exit just in front of the driver footwell
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Mr Whippy
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| posted on 23/12/08 at 12:37 PM |
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if you are struggling for space in the tunnel, how about that part of the exhaust being made from wide flat box section say 10mm thick by 150mm wide
or more. There'd be little restriction due to the large internal volume. You could easily fit such a pipe even to the underside and since its
area is so large it would keep cool even tight next to the floor. At the ends just make a flattend cone to go to and from the round section pipe.
Fame is when your old car is plastered all over the internet
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cd.thomson
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| posted on 23/12/08 at 12:41 PM |
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quote:
Originally posted by fesycresy
Are we 100% sure that this is going to be passed ?
I'd wait until it's confirmed before doing anything.
Its part of the IVA testing pilot manual. This means that during the current pilot period when cars will be inspected using IVA and SVA manuals but
only approved using standard SVA criteria exposed exhausts will lead to an IVA "fail" (although the cars will still be given their
SVA).
What this means to the builder yet to be tested is that it is very unlikely anything major will be changed between now and the introduction of IVA as
the consultation phase is being drawn to a close. If this requirement is to be withdrawn or adjusted it will be done at a later date, possibly leading
to a period when se7enesque cars will automatically fail.
This overview was provided over the phone by Peter from DJ sportscars (who produce the Dax Rush and other kit cars).
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bilbo
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| posted on 23/12/08 at 12:55 PM |
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All I can say is  
I didn't know about this new restriction. I'd recently decided not to bodge my car to get it ready in time before IVA. As a result,
I've missed a lot of potential build days doing other things. Now it looks like I have a lot of extra work to do before my test
I'll probably go for the boxed in approach as already muted on this thread as I'll never fit an exhaust down the t-tunnel
Presumably a side exit is still OK?
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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cd.thomson
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| posted on 23/12/08 at 01:01 PM |
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quote:
Originally posted by bilbo
All I can say is
I didn't know about this new restriction. I'd recently decided not to bodge my car to get it ready in time before IVA. As a result,
I've missed a lot of potential build days doing other things. Now it looks like I have a lot of extra work to do before my test
I'll probably go for the boxed in approach as already muted on this thread as I'll never fit an exhaust down the t-tunnel
Presumably a side exit is still OK?
Yes side exit is fine, its the exposed steel thats the issue for the test.
Peter was as frustrated as me, he told me to forge onwards with the build and to hope visciously for the best!
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Mr Whippy
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| posted on 23/12/08 at 01:07 PM |
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ok so like here's my idea for a flat exhaust that could fit down the tunnel or under the car. sorry for the rubbish sketch but all I have is MS
paint at work
 
Rescued attachment flat exhaust.JPG
Fame is when your old car is plastered all over the internet
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bilbo
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| posted on 23/12/08 at 01:10 PM |
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Thinking about it, Whippy's idea of flat box section under the car sounds another good possibility. Looking on the bright side, either way, it
means I wont nessesarily have to fork out for expensive Stainless components either
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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dinosaurjuice
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| posted on 23/12/08 at 01:17 PM |
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off topic slightly. but for mid engined cars does the IVA not allow you to have a silencer at the back of the car but outside the bodywork?
whippys flat exhaust idea looks the best option for front engined cars. i think it will look really neat having the tailpipe at the rear
will
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smart51
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| posted on 23/12/08 at 02:03 PM |
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quote:
Originally posted by Mr Whippy
ok so like here's my idea for a flat exhaust that could fit down the tunnel or under the car. sorry for the rubbish sketch but all I have is MS
paint at work
The problem with this is gas flow. Gas flow in a rectangular tube takes on the shape of an oval. The gas flow is almost stagnant in the corners of
the tube. A very flat rectangle will have very poor gas flow. You could overcome this with sheer size, though.
If you could find a new location for the fuel tank, you could put the silencer across the car at the rear. A single pipe along the side of the car
and under the rear somehow wouldn't be hard to cover nicely.
There was a picture on here a while ago of a futuristic Caterham, in green, that had an enclosed side exhaust. It looked really good.
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A1
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| posted on 23/12/08 at 02:09 PM |
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jeeso! i didnt know about this restriction...i like jabbas idea, i did a similar idea of sharing bolts for the silencer bracket, so when its off you
dont see anything...
what about having a double skinned system? dont most bikes use this currently? (ive not read much of the iva, so maybe im missing something)
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gavin174
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| posted on 23/12/08 at 02:10 PM |
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another option is to fit a zetec or xflow and run the exhaust through the passenger seating area...
you could then completly cover this area and then after iva remove the exhaust and cover and fit through the side as usual..
would mean a q plate for me thou i think as using sierra hubs and column etc
http://www.essexkitcarclub.com
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Mr Whippy
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| posted on 23/12/08 at 02:15 PM |
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quote:
Originally posted by smart51
quote:
Originally posted by Mr Whippy
ok so like here's my idea for a flat exhaust that could fit down the tunnel or under the car. sorry for the rubbish sketch but all I have is MS
paint at work
The problem with this is gas flow. Gas flow in a rectangular tube takes on the shape of an oval. The gas flow is almost stagnant in the corners of
the tube. A very flat rectangle will have very poor gas flow. You could overcome this with sheer size, though.
If you could find a new location for the fuel tank, you could put the silencer across the car at the rear. A single pipe along the side of the car
and under the rear somehow wouldn't be hard to cover nicely.
There was a picture on here a while ago of a futuristic Caterham, in green, that had an enclosed side exhaust. It looked really good.
True but the area is so large that the gas flow would be quite slow
a simple calc and the area of a 2 inch pipe is about 19.5 cm sq compared to almost 8 times as much for just a 150mm wide 10mm thick flat pipe meaning
the gas is travelling around only 1/8th the speed inside so little in the way of drag…
[Edited on 23/12/08 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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907
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| posted on 23/12/08 at 04:04 PM |
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quote:
Originally posted by Mr Whippy
True but the area is so large that the gas flow would be quite slow
a simple calc and the area of a 2 inch pipe is about 19.5 cm sq compared to almost 8 times as much for just a 150mm wide 10mm thick flat pipe meaning
the gas is travelling around only 1/8th the speed inside so little in the way of drag…
[Edited on 23/12/08 by Mr Whippy]
I'm having trouble following your maths
Paul G
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