Lotus Elan

Muffler- Standard Bore 1-5/8" or Large Bore 2"?

PostPost by: Mhlaitner » Thu Mar 21, 2024 8:10 pm

Hello Everybody! First time posting here.

I am almost done with a resurrection of my 71 Elan Plus 2. It was my late father's that sat garaged for 25+ years. At the time it went into the garage because it needed new brake servos and water pump. I am a novice when it comes to wrenching on cars and l don't have a ton of free time, so opted to find a reputable shop in my area, Kansas City, to basically rebuild the car to road worthiness so I can enjoy as I wish my father had. I will likely post in the restoration section detailing everything I've had done shortly. I had the absolute joy of hearing the motor start and run yesterday and we are getting to the final stages of having it back on the road. I am looking at either getting the Standard bore muffler or the "High Performance" large bore muffler from r.d. I was hoping somebody out there has any experience with either of these mufflers on their plus 2? Does the large bore really produce much more power? Or is it really just a different sound? Any feedback is much appreciated and I can't wait to live out my childhood dream of getting to drive and enjoy the car.

Max
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PostPost by: seniorchristo » Thu Mar 21, 2024 10:05 pm

Hi Mhlaitner

I am facing a similar decision for my Plus 2. I don't think the large bore muffler will make much difference in power, especially if you have not modified the engine for more performance. It will however probably be louder. Unfortunately there is no easy way to compare :( .
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PostPost by: Mhlaitner » Thu Mar 21, 2024 10:18 pm

Honestly for the price on the large bore I don't think it's probably worth it. Plus it may cause the low end to suffer without as much back pressure. I'm leaning towards standard.
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PostPost by: StressCraxx » Thu Mar 21, 2024 10:37 pm

If the engine is stock, the standard bore muffler is completely adequate, particularly if it has the original stock cast manifold. Loud or droning exhaust get tiring after a while.

Enjoy your father's +2. They are wonderful GT cars. Best wishes and enjoy.
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PostPost by: h20hamelan » Thu Mar 21, 2024 11:09 pm

More free flow helps the exhaust gas out, I am not sure back-pressure is real?

Tubular headers/manifold will help.

My plans as of now are a cherry style front ‘Thrush 24200’ and at the very rear a ‘Magnaflow 11114’
These are 2” because there is nothing 1 3/4 available, and why I am using a ‘resonator’ first inline to keep it quiet.
I would prefer a 1 7/8 and just a muffler, but unless I make one

Food for thought

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PostPost by: seniorchristo » Fri Mar 22, 2024 12:24 am

James

How much ground clearance do you anticipate with the Thrush 24200? It is 3 1/2" OD.
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PostPost by: h20hamelan » Fri Mar 22, 2024 12:33 am

guess I am James?

the diameter is 3 5/8 for the Thrush 24200
I was planning on putting this right behind the collector.
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PostPost by: h20hamelan » Fri Mar 22, 2024 12:46 am

what I have done in the past, with a bit of heat, and a bit of a gentle persuader

flatten one side. I know, it's not great, but the things are made of steel, and it's fine. Maybe only lasts 10 years as opposed to 15

I have been using Dynomax as they are cheaper than Magna Flowmaster
Dynomax doesn't have much below 2.5 part # 24250 but they are cheap, worked good on one sons 1980 Volvo 242.
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PostPost by: prezoom » Fri Mar 22, 2024 2:13 am

When building a complete new replacement exhaust system for my Plus2, I discovered something interesting. With the new Zetec installation, I started at the cylinder head with a flange from Dunnell Enginering, I constructed a 4-2-1 primary that is of the stepped up design. The first sections match the exhaust port diameter, then expands in diameter from the first collectors, down to the the last collector. From there, the single pipe increases the diameter to the halfway point to the silencer, where the final section increases in diameter to the silencer. By the time I got there, the pipe diameter was significantly larger in diameter as compared to what appeared to be the input to a fairly new silencer that the PO had installed. Thinking I was going to have to purchase a new silencer to match the new system, I decided to cut the input pipe away from the silencer to see how large the internal piping was as compared to the input. What I found was the internals were the same diameter as the last section of the new system I was building. Being thrifty, I constructed a new slip fitting, which I welded to the existing silencer. The output portion was also removed and a chrome extension, matching the input was also welded in place. Pleasant sound, not intrusive while driving, yet quiet enough to allow easy conversation when a passenger in onboard. Based upon what I found, it would appear the the difference between a standard silencer and a big bore silencer is nothing more than a difference in input and output diameters. Another bonus is, the new system from the head to the last collector is constructed as a single unit and can be installed/removed without disassembly, passes behind the left side engine mount, is above the lowest point of the chassis, except where the final section passes beneath the gearbox to the center spine of the chassis.
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PostPost by: h20hamelan » Fri Mar 22, 2024 6:48 am

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PostPost by: The Veg » Sat Mar 23, 2024 12:20 am

Welcome Max!
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PostPost by: Mhlaitner » Tue Mar 26, 2024 8:13 pm

Really appreciate all the feedback. Haven't decided yet but leaning towards the standard. I am going to post the project details once I have it all done. Really excited to get this car back on the road.
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PostPost by: h20hamelan » Wed Mar 27, 2024 12:10 am

I have been using oval exhaust tubing, You can get it with round at either end or straight oval, difficult to bend of course.
So, make your corners with round from the downpipe to under chassis, then again round from exit of chassis to muffler?
so the 2" will be fine for me, while it may not offer more power, it should also not loose any.
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PostPost by: Lotus54 » Wed Mar 27, 2024 12:20 am

My S3 is S/E + spec. It had a ‘racing’ header and 2” exhaust, but stock rear muffler. It had some phony joints, so I trashed the whole thing.
I got a stainless header, ‘standard’ mid pipe (ok, I made it) and stainless muffler (the one at RD).

The car runs a LOT better, sounds great. Not too loud at all, but has a very nice sound.

Edit:
I forgot to mention. I went back to ‘standard’ size pipes (I used the SJ stainless ‘manifold’).
While I did not do any timing etc to measure performance, I did not notice peak losses (could have some), but it works so much better where I will use it 99% of the time I have pleased.
Last edited by Lotus54 on Wed Mar 27, 2024 5:41 pm, edited 1 time in total.
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PostPost by: nmauduit » Wed Mar 27, 2024 3:35 pm

One may also consider the actual intended use for the car: the difference coming from the large bore would only be felt at high revs when one wants to make the most of his car (typically during a track day trying to overtake), if that intended use does not apply or is not deemed essential then the benefit may not outweight the drawbacks (e.g. installation / maintenance ...).
Indeed as implied by above comments I would see a big bore mostly (only?) justified if the engine is intended to be suitably prepared/tuned eventually.
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