Lotus Elan

Exhaust System for a Gas Flowed Head

PostPost by: alan.barker » Thu Jul 23, 2020 5:01 pm

That's true and take the Engine Mount off the Carb side so you can push it to one side.
Alan
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PostPost by: 1owner69Elan » Thu Jul 23, 2020 6:07 pm

pharriso wrote:
I bought one of the PMS SS exhaust manifolds (headers in the US) last year & am just about to fit it, it is an amazing work of art:
IMG_0815.jpg
IMG_0814.jpg

According to Paul Matty they are manufactured by the same company that make BMW's motorbike exhaust manifolds.

The ID of the Y piece (exit) is actually 42.5mm with an OD of 45.7mm, the pipe(s) that go into the Y piece have an OD of 38.2mm & ID of 35.1mm.


For reference, the TTR Race system:

Y-piece exit ID: 50.8mm (2")
Down pipes (Y-piece inlets) ID: 41.7 mm (1.64")
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PostPost by: Mazzini » Thu Jul 23, 2020 6:39 pm

I just fitted a Lotus mild steel manifold to my S2. I had to remove the exhaust manifold studs to do it, previously I had refitted the original Lotus cast iron manifold, but I couldn't get the clamp to the expansion chamber to seal properly. The cast manifold requires longer studs, studs so long that they have to be replaced to fit a fabricated system.

The fabricated system just touches the edge of the Gartrac built and modified chassis. The cut out in the chassis is an inch too far forward.

I have a PMS manifold. It fitted my S3 original unmodified chassis without issue. I wrapped it, but with hindsight I'm not sure if that was necessary. I've done about 6,000 miles with it and it's turned a lovely shade of gold/blue. The wrap fell off like autumn leaves.
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PostPost by: vstibbard » Fri Jul 24, 2020 12:43 am

I had a series of these extractors made in two sizes, this is the last set which will be sued on a 1760CC TC I'm using in S1 Shapecraft. As Graeme pointed out, being able to remove each outlet individually simplifies removal and refitting with everything in place, all radiuses curves with space between footwell and firewall as well.

We copied the FIA Appendix K design, but used the Burns system calculator that Rohan referred to.

IMG_7190.jpg and


IMG_7189.jpg and


Cheers

V
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PostPost by: el-saturn » Sat Jul 25, 2020 5:33 am

i got to a lathe and made two bits, incl. some 50mm (id) tube. the stainless muffler was opened, all of the 40mm tubing removed and replaced with 50mil stuff. it made everything much louder AND maybe the jump from 40 to 50 mm (excludíng the collector/header) to the rear tubing is not very scientific ...... BUT IT WORKS very well and much more lovely NOISE! sandy
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PostPost by: Mazzini » Sat Jul 25, 2020 6:08 am

vstibbard wrote:I had a series of these extractors made in two sizes, this is the last set which will be sued on a 1760CC TC I'm using in S1 Shapecraft. As Graeme pointed out, being able to remove each outlet individually simplifies removal and refitting with everything in place, all radiuses curves with space between footwell and firewall as well.

We copied the FIA Appendix K design, but used the Burns system calculator that Rohan referred to.

IMG_7190.jpg


IMG_7189.jpg


Cheers

V


Looks good. Will you wrap the system?
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PostPost by: 661 » Sat Jul 25, 2020 11:23 am

vstibbard wrote:I had a series of these extractors made in two sizes, this is the last set which will be sued on a 1760CC TC I'm using in S1 Shapecraft. As Graeme pointed out, being able to remove each outlet individually simplifies removal and refitting with everything in place, all radiuses curves with space between footwell and firewall as well.

We copied the FIA Appendix K design, but used the Burns system calculator that Rohan referred to.

IMG_7190.jpg


IMG_7189.jpg


Cheers

V


Very sexy
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PostPost by: alan.barker » Sat Jul 25, 2020 1:03 pm

Looks nice but you have 6 joints to seal just to the "Y" instead of 2 joints.
What Exhaust Clips will you use.
Alan
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PostPost by: Frogelan » Sat Jul 25, 2020 1:44 pm

Alan

You could possibly use double-slip connectors and/or V-bands. There are quite a few new tricks to try out, but I'm not sure Form 127 will allow all of them...

Rohan / Vaughan

A relevant part of Mazzini's question is not just the sizing of the primary / secondary elements but also the relationship between the exhaust port size say 34mm (?) and these dimensions (primary of say 41mm I/D).

Does anyone have any views on this question (for racing)?

[PS: I did look for the Burns calculator but could not see it]

Andrew
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PostPost by: rgh0 » Sun Jul 26, 2020 8:50 am

Frogelan wrote:Alan

You could possibly use double-slip connectors and/or V-bands. There are quite a few new tricks to try out, but I'm not sure Form 127 will allow all of them...

Rohan / Vaughan

A relevant part of Mazzini's question is not just the sizing of the primary / secondary elements but also the relationship between the exhaust port size say 34mm (?) and these dimensions (primary of say 41mm I/D).

Does anyone have any views on this question (for racing)?

[PS: I did look for the Burns calculator but could not see it]

Andrew


form at this link - not an online calculator but you send in the details and they send back a design

https://burnsstainless.com/pages/race-engine-spec-form

I prefer a small step up from the port diameter where it leaves the head to the primary pipe inner diameter. A small step up has no effect but a small step down can be detrimental so this allows for any small misalignment between pipe and head port.

i.e. The ports in the McCoy conversion stage 4 racing heads I use are 32 mm diameter

cheers
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PostPost by: pharriso » Sun Jul 26, 2020 1:38 pm

Fitted my Paul Matty large bore SS exhaust Manifolds yesterday, thankfully there's plenty of clearance to the chassis:
IMG_0923.JPG and


Took it slow & steady, removing both engine mounts so I could move the engine over to install them... :roll:
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PostPost by: Quart Meg Miles » Sun Jul 26, 2020 11:06 pm

alan.barker wrote:The problem is once the Engine is in place the access is difficult to redesign the Chassis Flange.
Unless you feel super Zen and simply remove the Engine a second time.
Alan

It is possible to bend the edge of the flange without removing the engine if you have adjustable short wrenches (known as King Dicks in UK). It is tough but I'm not a big chap. Or cut with a Dremel, as mentioned above.
Meg

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PostPost by: alan.barker » Mon Jul 27, 2020 5:28 am

On my Sprint i bent the flange.
I cut a slot into a steel bar with 2 hackblades fitted at same time. So the width of the cut was 2 blade widths. This just slide over the Chassis Flange, then pulled on end of steel bar like a lever.
The "King Dick" adjustable from my Apprentice days in the Dockyard is too bulky.
A few years later i removed the Engine to change the Clutch and tidied it up then with a File.
Alan
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PostPost by: vstibbard » Thu Jul 30, 2020 4:39 am

I made two versions, one for warmed up std 1558cc engine capacity and another for designed for race engines which with different length secondaries work well with a larger capacity (1860cc in my case) road/track days spec engine. I'll have to find out the dimensions and post them. the ones pictured are the race spec, my last small diameter set was used on the last S1 which made good torque and power.

Re Alan's 6 joints observation, the extra joints are worth dealing with for the ease of fitting and removal, they have been with pipe to slip joint tolerances which are very close, being high grade thin wall stainless they respond quickly to heat, I warm the slip joint when assembling them and they drop in cleanly and end up with firm inference fit when cool.

Cheers

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