Lotus Elan

Exhaust setups

PostPost by: benymazz » Tue May 21, 2019 2:02 pm

Hey all,

Not really looking for help but rather trying to gain some knowledge. What are people using for their exhaust setups on their Elans these days?

My father did a custom job for his Elan many years ago using a 4-2-1 header (actually two headers, one takes cylinders 1 and 4 and the other takes cyl 2 + 3 and then they feed to a Y) which is then straightpiped to the back with a glasspack/cherry bomb tucked under the trunk. The glasspack is modified by having a correct diameter pipe welded on to the inlet (and at a slight upwards angle to match the contour of the body near the trunk) and a threaded rod and nut welded on to the top that goes through a hole in the trunk as a mounting hole. Gives a great sound—not too loud, "purrs" up to about 3000rpm or until you open up the throttle and then it's a nice throaty sound. Despite a CR gearbox and 3.9 diff I think I could live with it if doing an extended road trip, which seems to be the benchmark for loudness on this forum :lol:
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PostPost by: Elan45 » Wed May 22, 2019 3:20 pm

Sounds like the exact same set up I did many years ago and is still on one of my Elans, except I didn't have to adapt the diameter. I bought the cherry bomb from NAPA and they had different diameters of pipe sizes and I was able to buy one just the right size. Then, to keep from getting the back of the car colored from exhaust, I used a plated pipe from a sink drain to extend the exhaust out the back of the car. IIRC, I also used part of a hanger from an MGB to hang the muffler. I also did a drawing of the pipe bend which got me 2 intermediate pipes from a stock 10ft length of pipe. I'll have to do this again since I should have 2 Elans running later this year.

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PostPost by: nigelrbfurness » Thu May 23, 2019 1:19 pm

Probably a stupid question but what's wrong with the standard factory setup? All the parts are easily available and no extra work needed...
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PostPost by: JonB » Thu May 23, 2019 3:28 pm

Funnily enough I was reading the Miles Wilkins engine book this morning and there is a bit about exhausts; specifically after market models. He claims that very few of them will outperform the standard setup (but there's an observation that a properly designed branch manifold 4-2-1 is much better than the old cast iron manifold - so I'm glad I have a Lotus branch manifold, centre pipe and back box on my +2..). Sobering thought: "The wrong system can rob the engine of anything up to 15 BHP - this has been proved by dynamometer power tests."

He also says Lotus went to great effort to get pipe diameter and silencer baffles right and owners should not alter them (he's quite unequivocal on this point: "Do not alter them." other than to fit the later 4-2-1 Lotus manifold to earlier models).
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PostPost by: prezoom » Thu May 23, 2019 3:33 pm

When I constructed the exhaust system for the Zetec in my Plus2, I didn't follow the "normal" 4 into 1 pattern that is used by others. Mine is a 4-2-1 system using larger diameter tubes that expand in diameter from the manifold flange clear back to the silencer. Since I retained the original clutch housing and gearbox, I needed more room for the larger diameter tubes where the system passed between the clutch housing and the chassis. I cut the ring off of the clutch housing and moved the clutch release hydraulics into the housing, utilizing a Mondaeo/Contour release mechanism. This allowed me to keep all of the exhaust system above the bottom of the chassis until it makes its path down the center of the chassis. Support for the header and Y pipe is done at the bottom bolt securing the tail housing to the gearbox main case. A threaded sleeve was welded to the hex end of the bolt, and the support bracket is bolted to the sleeve.
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PostPost by: Chrispy » Fri May 24, 2019 12:46 am

JonB wrote:Funnily enough I was reading the Miles Wilkins engine book this morning and there is a bit about exhausts; specifically after market models. He claims that very few of them will outperform the standard setup (but there's an observation that a properly designed branch manifold 4-2-1 is much better than the old cast iron manifold - so I'm glad I have a Lotus branch manifold, centre pipe and back box on my +2..). Sobering thought: "The wrong system can rob the engine of anything up to 15 BHP - this has been proved by dynamometer power tests."

He also says Lotus went to great effort to get pipe diameter and silencer baffles right and owners should not alter them (he's quite unequivocal on this point: "Do not alter them." other than to fit the later 4-2-1 Lotus manifold to earlier models).


I don't give a whole lot of credence to this. I cut open my standard +2 transverse muffler to empty all the rattly bits until I replace it and there's practically nothing in it. One baffler about 2" in from the inlet and then a straight perforated pipe and a little bit of wadding (most of which was gone). I think I'll replace mine with a generic oval straight through and maybe a hotdog and see how it goes. The headers have a much larger influence over scavenging than the mufflers.
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PostPost by: JonB » Fri May 24, 2019 7:26 am

No worries Chris - I was going to add to that post depending on how much credence you give to the author or some such, as we've recently discussed timing and there are people who challenge what Miles wrote on that subject. I agree re: scavenging but after the header, what effect can the silencer and centre pipe have other than to move the gasses to the rear of the car with as little resistance and noise as possible? In which case you'd be looking for as fat a pipe as possible and a free flowing silencer, no?
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PostPost by: Certified Lotus » Fri May 24, 2019 9:39 am

I installed a complete TTR 2” system from headers to muffler (I won’t call it a silencer because it certainly isn’t). Now I have a “built” engine with 147HP at the crank so the better free flowing exhaust is needed. It’s a bit loud when you push the pedal hard but it goes like stink so all part of the sensory experience.

Here is a short video:

https://youtu.be/dgrl1NBuaWc
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PostPost by: JonB » Fri May 24, 2019 12:49 pm

That looks like great fun!
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PostPost by: groucho » Fri May 24, 2019 8:10 pm

I've given this a little thought since I'm getting close to putting my engine back in my S2. What I have now is how I got it 20 years ago - tubular headers going straight back into some kind of glasspack muffler. I did drive one with a completely stock exhaust once and was surprised at how great it sounded on the road, though. It looks like a little straw coming out the back though. :lol: I'll probably put the existing setup back on for now but would like to update it sometime. I doubt I'll go completely stock, most likely a stock-sized pipe with some appropriate muffler at the back.

I have had a thought of doing a side exhaust in front of the rear tire, like a '60s-style racer, with a plain non-chrome exhaust. I'm not sure if I'd actually do it (not least because of heat concerns! but I think they could be alleviated, but ground clearance is a big concern) but I think it might be interesting.
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PostPost by: el-saturn » Fri May 24, 2019 8:36 pm

i kept my lovely welded ex manifold (2 in 1 and 2 in 1) BUT right after the 42mm (is that correct?) Y-piece i moved to 2inch and opened up the orig elan muffler which has a perforated inside and all the rest in 2" stainless steel - she don't this way BUT a bit loud for some sandy
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PostPost by: JonB » Sat May 25, 2019 10:22 am

I have a S/S silencer which I swapped for a NOS "stock" unit a while ago. Just too noisy on a long run.. The standard exhaust sounds great to me.
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PostPost by: Bigbaldybloke » Sat May 25, 2019 9:39 pm

Have a look for threads on ceramic coating of exhaust manifolds if you are going for a new system, it’s reported to improve performance and reduce heat build up in the engine compartment.
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PostPost by: StressCraxx » Sat May 25, 2019 11:39 pm

I replaced my original cast iron manifold with resonator in the downpipe std exhaust. One of my friends sold me his Dave Bean 4-2-1 manifold. Primaries are 1-3/8". It has a very long flat collector that tapers to a 2" outlet. It worked really well for more than 30 years until I found some cracks in it. The muffler was a 2" aftermarket turbo muffler that was more noisy than desired, but worked well. Replacing the header made the twincam come alive at 4000 RPM along with the sprint cams and 32mm chokes I had installed 3 years before.

I replaced it with an identical set in 304 stainless coated inside and out with ceramic. The header is really well made with beautiful bends and tig welds.

The important thing to understand is the airbox, carbs, head, cams and exhaust all need to flow properly and work together as a unit, preferably tuning and jetting on an engine dyno or a rolling road chassis dyno.

Yes, the engine bay stays cooler and so does my right foot. YMMV
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PostPost by: groucho » Sun May 26, 2019 2:20 am

Interesting talk of coatings. I've considered coating my header while it's out but figured the fairly open engine compartment may make it unnecessary. I drive past Swain Tech, one of the top coating places, every day on my way to work so it would be easy to have them do it! I had pretty much decided to skip it but could be talked into it; do those who have done it feel that it was worth it?

I need a little more work done beforehand, though - just today, I was out working on the car and noticed a crack in one pipe - see picture - so I'll be needing some welding first!
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