I decided to have an exhaust manifold and system made, unfortunately your recommended manufacturer was too expensive, so I choose another supplier whose price was more affordable. When the car was finished, the exhaust system looked fantastic and the welding was excellent, unfortunately when it was put on the rolling road the performance did not match what I was expecting. The guys running the rolling road said the engine was performing unusually and believed it was something to do with the exhaust manifold. What can I do?
I would check your exhaust manifold dimensions very carefully to ensure all the pipes are equal and the correct length, if they are not, which is quite likely then the contact the manufacturer and see what they are prepared to do for you. Hopefully they will sort the issues out for you, unfortunately the difference between a cheap exhaust manifold and a manifold made to the correct dimensions can take 4 or 5 times longer to manufacture and it is only when you come to measure the manifold itself after an issue has arisen, that this problem is discovered. We have investigated in the past, cheaper alternatives but have always been let down and as the old saying goes you only get what you pay for.
Please can you tell me what the decibel level your exhaust systems have?
As far as decibel levels are concerned, it is impossible to give a decibel level that you are likely to see. We have done extensive testing over several years. We have even got to the point where we have tested two identical cars, with identical exhaust systems and boxes and have both read 5 db different. We have then swapped the exhaust box over and found the decibel level has still remained the same (i.e. car A produced 100db, car B produced 105db with exhaust boxes swapped, car A still produced 100db and car B still produced 105db). More often than not the decibel level recorded is produced by the intake system. Also the body panels and components on the car vibrate. We have supplied air intake systems to some customers and they have found a dramatic decibel drop, even though the decibel level is checked by the exhaust pipe.
There are numerous other reasons the decibel level can vary, even down to atmospheric levels, where the car has been measured on concrete, grass, near other cars etc. The more highly tuned the engine the louder the engine gets as well. We also find that when the exhaust boxes are new, they are usually slightly louder than after they have been run for a while when the packaging has had time to settle down.
We normally reckon that it is possible with a standard engine on throttle bodies (carbs are usually slightly louder), to achieve almost under every condition under 105db. We have in the past seen as low as 94db, but this was when the engines used to be revved to 3-4,000 rpm. Unfortunately the track days are now asking for decibel levels of such ridiculously low levels, that it will be soon impossible to get through noise without physically restricting your exhaust system with baffles to achieve the required limits but this will mean losing BHP. To give you an idea, a few years ago when I took my ARDS test, I was driving a Volvo V70. I was told by the instructor that on certain days, it failed to get below 100db. This car was completely standard.
What is the difference between type A exhaust manifold and type C exhaust manifold. Also is Type C exhaust manifold for C20XE the same as X16XE? I understand that you can buy a specification from you and fabricate at manufacturer of your choice, I would like to know how much is the for the design specification and how to order.
Due to the high level of performance and the large range of vehicles that our engines are fitted to, we have now stopped producing a range of exhaust manifolds. When we originally started, there were exhaust manifold that could simply be purchased from various manufacturers that would simply fit a model of car, these were quite often manufactured at a price to be affordable. But over time, as we developed our engines, the exhaust manifolds became more advanced to produce optimum performance. Each time a new design was produced, it was given a new letter but because it became impossible to manufacture and hold quantities of exhaust manifolds and the designs became ever more complex and kit specific on many occasions, this has now stopped. There are still many road based affordable exhaust manifolds manufactured by various companies and many of these are well made, but not suitable for high end performance.
The dimensions for the 1.6L engine and the 2.0L engine are different due to its capacity, effectively any exhaust manifold design that we would sell are for maximum overall performance. The pdf download shows the kind of information you receive, which you would then present to your exhaust manufacturer. When requesting an exhaust manifold design, please give as much detail as possible about your engine e.g. cam profiles, compression ratio, cylinder head port work spec, valve size, throttle body design, etc.