Technical Tips from Powermac Products
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FLEX SPACERS
THE EXHAUST PIPE. (here we use examples of our two most popular pipes)
Which pipe will give the better result?? ( Phase III or XL5)
Over the last twelve months we have had repeated requests for information on the best clubman pipe for a given situation. It is impossible to answer this correctly over the phone without us having a good knowledge of the track.
Our two current pipes both have very different characteristics and the best pipe for one track is not necessarily the best pipe for the next.
Similarly running at less than optimum length will result in poorer engine performance.
The on power histogram from a data logger is the easiest and quickest way to determine characteristics the pipe should have for the best performance for the particular track. Of course not everybody has a data logger at their disposal so we will try to explain as best we can.
In order to help you decide on the best pipe to use on each track it is important to know what your minimum and maximum revs will be on a good lap, and how much of the time you spend on power at those revs.
Please click image to open it full size in a new window.
On some tracks on any given lap you will spend more of your time (on power) in the upper and lower rev ranges and less of your time (on power) in the middle of the rev range. See PI chart above.
Please click image to open it full size in a new window.
On other tracks on any given lap you will spend more of your lap (on power) in the middle of the range.
Again see above.
As the rules stand with the Clubman engine, the exhaust pipe will always be a compromise.
i.e. maximum power will only be obtained over a limited rev range. Therefore to get the best result possible it is necessary to have more than one exhaust.
Two exhausts, with the right characteristics should be sufficient to cover most situations.
The first Graph above comes from a Data Logger, used in Clubman light at Todd road in Victoria. It shows maximum power is needed for the longest time between 7,000rpm & 9,200rpm. And again at 11,300 & 14000rpm
Also evident is the need to develop power right up to 15,500rpm.
The best pipe at this track is definitely a pipe like our new XL5 pipe because of its better bottom end and good top end characteristics. The mid range performance is not nearly as important here because you are not “on power” in the mid range for as long as you would be at some other tracks.
The second Graph comes from a Clubman Light Kart at the Cobden track also in Victoria, where the Victorian Titles were held just recently.
Here a pipe with completely different characteristics will give a better result.
Our Phase III pipe has more mid range Horse Power than any other pipe we have tested and this is obviously what is required here. Bottom end is not important because as can be seen by the graph, the engine does not even get below 9,200 rpm’s
There is still a need to develop power right up to 15,500rpm. And both the Eagle & the Phase III are about equal in that regard.
Looking at an “on power” Graph from a data logger is not always as clear cut on some tracks as the two examples above however, and testing back to back of both exhausts on the track is the only way to be sure which one will be the best suited.
Looking at the graphs above it should be clear that trying to shift the power by altering the flex length wont give the you advantage that changing to the correct exhaust will. The recommended exhaust length should be used with only a small variation depending on your engine setup.
What is the difference between the Phase III & the new XL5 ??
Please click image to open it full size in a new window.
The above Graph from our Dyno shows the better bottom end of the new XL5 pipe, and the better mid range of the Phase III. Top end remains about the same.
It is worthwhile repacking your Silencer
It is certainly worthwhile repacking your silencer periodically. Our testing has shown that a silencer which has the holes in the inner tube blocked with carbon will not perform as well as a new clean silencer. Sometimes 1-2 tenths of a second slower. So you can see that for a little effort and negligable expense you can gain some free horsepower.
NOTE; See news section for info on recommended exhaust lengths.
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