Exhaust Manifolds for Twin Cam

[Certified Lotus]

I'm starting a new thread on the subject of custom exhaust manifolds for the Europa Twin Cam engine. In my rebuild thread of 2358R the subject came up and I've started to research the different types available as my engine will be coming back from Quicksilver Racing soon.

For those of you that don't know me. I'm not a "keep it OEM" type of guy. I like taking a well designed sports car and enhancing it a bit for performance. In my mind, most car manufactures had to either conform to some silly law or use readily available parts to keep cost down (or both). The areas I focus on the Lotus cars I have owned are increased engine performance (HP & torque) and suspension (better coil over shocks).

How many different types of exhaust manifolds (headers) are available for the TC engine that will work in a TC Europa? Please post examples with manufacturer cost and a photo. Any personal experience would be greatly appreciated.

RD Enterprises sells a nice mild steel header that is great for a stock engine. It is fairly inexpensive and they have the entire exhaust system to bolt in. ($295 for the header and connecting pipe). Pipe diameter of primary pipes 1-3/8"; outlet pipe is standard 1-3/4".  Headers include elbow pipe for attachment to muffler.

TTR (Tony Thompson Racing) in the U.K. Has a big bore header available that is designed for the performance of a 26R engine. ($562 plus shipping to US) I have this on my Elan and it is well built. I wonder if I can use this and custom make the balance of the exhaust pipe?

Kampena Motorsports used to carry a custom manifold for Elan's and Europa's but the builder stopped making them. Too bad, they looked well designed ($850 for the headers).

[Roger]

As I  said in the earlier thread, I have Ray's system on my TC. This has the advantage of my being able to keep the luggage box without change. This is because it turns through 90 degree and passes under the engine to the intake side where there's more room. No gear change,  clutch cable, speedo cable etc. It looks like you might be able to cut the third one you show, and turn it around. I can't  really tell, but it looks like it might be more challenging with the others.
I have seen systems where people have moved the battery and anything else that got in the way, and installed high-level exhausts that come out above the engine mounts and go rearwards from there, but they don't have the luggage box.

It'll  be interesting to see what people come up with!

[BDA]

There was a tubular header from Lotus as an option - it's shown in the parts manual. I wonder if any have survived?

[EuropaTC]

Hi,
As you know already, this topic is of interest to me as well and I'm currently awaiting the arrival of several bends and straight lengths of stainless with an aim of gluing one together.

I'm like Roger in that keeping the luggage tray is paramount so mine will follow the path of the original, ie down between the engine mount, gearchange and clutch cable, underneath the engine and meet up with the exhaust in it's OEM position.

One thing that strikes me about the first image is how long the primaries are, from the angle of the shot it gives the impression of being almost a 4-1 system.  The following 2 shots look similar to Elan systems so at the moment I can't envisage how they'd work on the car.

Dave Vizard quotes 2 systems in his "Tuning Twin Cam Fords" booklet, the first a 4-2-1 for tuning above standard and then a 4-1 system for what he calls radical cam timing.

a) 1.625" (41mm) primaries at 13" (330mm) long, secondaries in 1.75" (44.5mm) again 13" long followed by a 2" tailpipe at 28" long.
b) 1.375" (35mm) primaries at 29.5" (750) long  then a 5" long collector feeding a 2" x 22" long tailpipe.

Whatever you end up with I can't see it being worse than the OEM cast iron manifold. I've got one set up at the moment and it looks more like something designed to fit rather than something to produce power. 1-4 are very mis-matched lengths for example. I'll take some photos and measurements tomorrow, if nothing else it shows where the start points are.

Brian

[Certified Lotus]

Banks Europa has one listed on it's website (Full system - hand formed headers - with Repackable muffler for $721. Anyone have one of these that can show us photos?

[Grumblebuns]

My JPS came with a Dave Bean header. It's a multi piece system held together with clamps. I don't remember if it was a 4-2-1 or a 4-1 system. I didn't do a trial fit before I got it ceramic coated and had to oval out a couple of the holes to make a decent fit over the studs other wise, a good fit.

There is also the custom route as my spare engine has.

[4129R]

Banks Europa has one listed on it's website (Full system - hand formed headers - with Repackable muffler for $721. Anyone have one of these that can show us photos?

Richard at Banks tells me the systems don't fit.

I am sourcing a local manufacturer in Norfolk as I need at least 3 complete systems.

[Lou Drozdowski]

Since I wanted to keep the luggage tray, I opted for Ray's mild steel system. After having JET coating applied, I installed a single flexible pipe w/wrap to Monza exhaust tip. No muffler... clean, loud and within budget! 


Brother Vic has the Banks system on 3522R, which he got some years back...a few more $$$...but sounds great!

 

[brucelotus26r]

The Banks system look like the one on my TC

[EuropaTC]

Some real works of art on this thread, lovely workmanship.

And in complete contrast, this is what we started with, or at least what the UK TC cars came with.  3 shots taken today of my old one and as you can see although it's a compact casting there isn't a great attempt to equalise the primary tube lengths. The manifold joints are matched to the exhaust ports but it goes a bit strange as the secondary joint comes into play with  rectangular openings. Is this better ? No idea but it looks strange to me.

In other news, my DIY kit of parts arrived today. Unfortunately we have a fireplace to build which the project manager claims has priority.....    never mind, it's just more thinking time !

Brian

[jbcollier]

It's not bad really.  Not equal length but the 1 & 4 are separate from 2 & 3.  Nice double downpipes and it would perform quite nicely.  It also has the benfit of being much quieter.

[EuropaTC]

As a mass production casting I'd agree, but I'm confused by the square ports. I get they're trying to maximise surface area within the available casting but I always thought that square holes don't have uniform gas flows,  the corners create dead spots and lower flow rate. On this design it's going from round -> rectangular -> round (in the downpipes) which I don't understand.

Incidentally, as this is a thread on exhaust headers, some more trivia I've read recently which may be of interest to anyone else who's also trying to understand these things. In the book "four stroke performance tuning" the author overturns something I'd always thought essential, that of matching headers to port openings. Basically the claim is that matched bores lose power and that you should aim for a step into a larger bore (which slows the gas ?). He gives an example of a 1600cc engine which shows gains both mid range and top end by having larger header bores than exhaust ports.  Apparently it's all about impeding backflow, page 19 on google books if anyone else is intrigued by the idea.

Brian

[jbcollier]

Exhaust design is complicated.  Tuning an exhaust with specific length primary pipes and total length can have a significant affect in a certain rpm range.  However, it often results in negative effects in other rpm ranges.  Back in the day with single cylinder motorcycles, this was referred to as "megaphone-itus".  Basically the reflected pressure wave is now arriving at an inauspicious time and messing up the engine's gas flow.  Fitting a step in not technically an improvement as it doesn't improve anything.  It makes everything a wee bit worse.  So you loose a bit of the flow improvement during the happy rpm period but you also do not loose as much power during the unhappy rpm periods.  This results in less peak power but can give a broader, more-useable, power range.  In the old days striking this balance was a matter of extensive experimentation -- imagine literally piles of trial exhaust systems.  Nowadays computers can reduce significantly the amount of experimentation required.

How relevant is this to a tractable street-prepared engine?  Not much really.

[2483R]

Grumblebuns

Is the Bean header system you have equal length tubes? Hard for me to tell from the pictures.

It has been a while, but last time I checked Bean no longer sells their headers. They may still sell the stainless double S system, I believe a copy of the factory headers, also not equal length.

Ray’s headers are a great price, but judging from the pictures are not equal length.

For someone looking for a bargain Paeco offered me a set of headers for $180, similar to what Ray sells. But it has been a while so they no longer sell them.

It may just be, that to get equal length headers for a TC you will have to make them yourself. So far I have been unable to find equal length headers at a reasonable price.

[FranV8]

When I spoke to Richard before ordering just a stainless replacement downpipe on system, he said the cast one doesn't perform that badly, you could build a 150nap engine on it.  At least that's what I remember, I could be wrong...