Here's the newest update on my technical development (hopefully improvement):
As I'm sure you've all realised, the engine compartment of my Lotus Europa S2 is heavily modified, and some mods are pretty wild. In particular, the exhaust manifold welded by a previous owner is a visual disaster, eventhough it works quite well.
Over the last few years, I've already made a few efforts to tidy up the tangle of cables and not forget the looks as well as the function. Unfortunately, my resources are limited and in many areas I don't have the capacity to remodel functional components in such a way that the appearance is enhanced. The resources of time and, above all, money were mostly tied up by problems that repeatedly made the vehicle stationary for months.
Now I''m in the process of making a major visual improvement, namely a new exhaust manifold. I ordered the Renault x-flow manifold from Lotus Supplies (formerly Banks) in England, which has been tried and tested for many years and, according to various reports, works very well for sporty road use. I have even seen a few racing cars with this exhaust, for example our former member Valerio Leone. His car was sold to a city near where I live. I'm going to meet the new owner next month.
Right now, I don't have the budget to have a manifold custom-built by an expert, so this cheap alternative will have to suffice for the time being. Fortunately, as I work in a mechanical engineering company as Technical Manager, I have very easy access to stainless steel pipes and an excellent TIG welder. This is where it gets interesting.
In my opinion, the Banks manifold is a very good basis in terms of its design. The primary pipes are exactly the same length and the 4-1 collector is very well made. Four Ø42 mm primary pipes come together into a Ø48 mm pipe and this is where I have a few concerns. For a racing engine with very large valves and peak power at around 7000 rpm, the diameter of the single pipe behind the collector seems quite small to me. The cross-section of the single pipe is just 33% larger than that of each primary pipe. In the literature, 30% is the absolute lowest number I've ever read anywhere, and that was about 2-1 collectors, if I've got it right in my head. So I phoned my engine tuner Renault Schäfer, which is located very near to the Nürburgring. He said that a 48 mm pipe would be the absolute lower limit that they use, depending on the silencer behind that. For the Alpine 1800 and 2000 cc engines, they mainly use Ø55 and Ø63.5 mm, depending on the desired exhaust sound volume, among other things. For a 1600 cc racing engine, it would make sense to increase the cross-section of the single pipe to at least Ø55 mm. All mentioned diameters refer to the outer dimension with a wall thickness of 1.5 mm.
In addition, the connecting flange of the manifold is not suitable for the shape of my exhaust ports. I have already tried milling it out, but unfortunately the narrow Banks flange does not provide enough material. I therefore have to cut it off and replace it with a flange with more diamond-shaped ports. A laser-cut flange is quite easy to obtain from the company I work for. My hope is that this will give me the best of both worlds: Good performance at an affordable price. In terms of weight alone, the Banks manifold already has a 6 kg advantage over the old one. If it at least doesn't mean a step backwards in terms of performance, I'll be happy. Of course, a few more horsepower would be even better. According to my research, the slightly shorter primary pipes could possibly mean a little more peak power or shift the maximum of the power curve slightly into the higher rev range. In the best case scenario, I would compare the new and the old exhaust on the roller dynamometer before the next race. But that will be very tight in terms of time.
So far, the exhaust has cost me around €770 including customs. Once everything has been modified (hopefully upgraded), it will probably be just under €1000, which is peanuts compared to a customised exhaust.
