Esprit Stainless Steel Manifold

My car is a 1990 Esprit Turbo SE which I have owed for 11 years and carried out all work myself including full engine rebuild, full re-spray e.t.c.

As most esprit owners know the manifolds are prone to cracks and warping. The SE model seams to warp in the same place the 4th port as the weight of the turbo must apply force here and when heated bends the casting. Cracks occur due the expansion and contraction in stressed areas.

I replaced the exhaust manifold the first time with the South West lotus cast item costing about £550. After 2 years it warped at the 4th port as described. It was taken off machined and re fitted with new gaskets solving the problem. A further 2 years on it warps again.
At this point I decided to pursue a tubular equivalent.

A local company to me called Alunox Exhausts took on the job as they have a lot experience in the design and manufacturing of specialist manifolds and complete systems for high end sports cars and professional race teams. They have produced some very high spec systems for a number of race teams including the March DFE Cosworth F1 series (1976) which can be seen on their website.

The Esprit Turbo exhaust will run at high temperatures so Stainless 321 was chosen as the material which can handle up to 900C . This will prevent any cracks at extreme temperatures and give good longevity lasting the life of the car. Some stainless manifolds on the market are made of Stainless 304 which is cheaper and can crack.

The design of the exhaust is based on the original, in that cylinders 1 and 4 collect together and 2 and 3 ,but this time running equal lengths in a 4 into 2 into 1 configuration, meaning the gases will arrive at the turbo in a more synchronised manner . This can be heard in the exhaust note. The stainless steel also provides better gas flow in the manifold unlike the rough service of the cast one, which also degrades and flacks into the exhaust.

  

The manifold is welded using a fully purged TIG process to an aircraft grade standard. The flange plate that meets the head and turbo are precision cut by laser and again are stainless.

There is also a weight saving to be gained the old cast item weighing about 15kg as to the new stainless 321 weighing about 6kg which makes it easier to position during fitting. The manifold should fit all 4 cylinder Peter Stevens Esprit Turbos from 1988.

Leon at Alunox Exhausts is going to supply the manifold as a kit including nuts ,new stainless studs and gaskets. He will also make the manifold with the option of changing the turbo mounting flange for customers who want to upgrade the turbo to a more modern equivalent which may include optional waste gate pipe work for use with turbo’s using an external waste gate.

  

Leon also replaced the CAT bypass pipe with his own build to a higher grade stainless steel than my old one. He again offers an option on silencers in this pipe if required or even a High Flow CAT unit for those cars registered after 1993.

I have to give a verdict as I have been running the car now for about a week now. The first thing you notice is that the power is delivery is more instant than before with less lag and better response due to the better Gas flow.. Second you notice that the exhaust note seams to buzz more like that of a race engine. And third you notice the car pulling harder for longer in the revs.

We think there has been a power increase of about 15 – 20 BHP which is only an estimation, we would need a rolling road to be more accurate. However there does seem to be better torque especially at the low end.

I have to say this is a very high end piece of kit made to a very high standard that won’t be beaten. It takes a lot time and skill to manufacture this so it is a bit more expensive than the standard item, but if you are like me on your second time around having spent £130 on gaskets to remove the cast manifold ,re-machine and refit ,then there is no option to this fit and forget solution.
Leon may be able to manufacture this more efficiently in terms of cost if a group buy was set up, may be on the forum or through Pete Musgrove from PNM.

I am further demonstrating this on the Club Lotus Festival at Donington Park on the evening Track Day session for all to see on Friday 12th Augus 2011t. Pete Musgrove from PNM engineering will be displaying the manifold on his stand over the weekend. If you are interested talk to Pete as he is going to try and organise a group buy.

In addition to this Alunox also produce Cat Bypass pipes with options such as high flow silencers or race CAT’s and even rear box’s made to order. There is also a bigger charge cooler and electric pump on its way.

For further information contact Pete Musgrove at PNM Engineering on 0151 6306101 Or Leon at Alunox Race Exhausts on 01978 851100 or visit their website at www.alunox.co.uk

An update to the manifolds performance and longevity (Feb 2012)
The car performed well on the track at castle Donington last year and for the first time I was able to give the Elises and Exiges a run for their money with better throttle response and quicker turbo spool up gained by the gas flow characteristics of the new manifold.
I have pushed it as hard as I can on the track taking the thermal dynamics of the exhaust to the limits. I have also have ran the car for many sustained periods on motorways (Whilst visiting customers) e.g Wrexham to Kent which takes about 5 hours.

I have now covered about 4000 miles on the manifold and another tracked day. I am also looking to do another one this year.
The manifold was also braced for extra support and piece of mind. The style of brace used allows the manifold to expand horizontally whilst supporting vertically. The elbow or down pipe section feeding the turbo flange is where the greatest concentration of heat occurs and there for great expansion horizontally.

The brace pivots on heat resistant ball joints and comes as part of the manifold.  This concept of bracing is quite standard on other track cars such as Nobel and TVR

 

The manifold has shown no signs of distortion, sagging or cracks.  Alunox Exhausts have also just completed a set of manifolds for the Lotus 72.

Trackday update (Apr 2012)
Another follow up, I've just done the lotus track day Tuesday 24th at Oulton park , the manifold is proving to be reliable as it was again driven as hard as possible taking it through its heat cycle many times through the day. below is another shot of the parts that come with the Kit now available.

LEW's Verdict

This piece of manifold work looks great and is something to behold. We'll see how it performs over time, which is the real indication of the value of this upgrade.

This mod was performed & supplied by Mark Kassim.

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If you try this, feel free to e-mail us with your Verdict at admin@lotusespritworld.com

October 2012
Just to let you know the Alunox Exhausts are going to offer a warrantee on the manifolds , mine has been on for over a year now and is fine. The cost of the manifold is about £1200 including studs , nuts and gaskets as shown.

November 2012
The price of the manifold has now been reduced to £990 from £1200 for the full kit .

November 2012
There has been further manifold design released from Alunox Race Exhausts for the Esprit which uses Slip Joints, which can be used for cars with very high power outputs,