>I have a Phoenix on a GT6 mk2. It looks and works great.
YES I designed that back in 1982.
(though a fat lot of people ever give me credit for it!!) Ever since I proved it worked, instead of that dreadful thing sold at the time by SAH, there has been a rush of people ready to take credit for it, from exhaust makers who don't know anything about anything, to unscrupulous traders trying to live off other people's brains!
I get them every day!
It all smacks of the usual money over brains argument.
I spent the money and time working around the many Triumph engined problems....eg. the truly dreadful exhaust port breathing and the inlet temperature optimisations needed, and got a fat lot of thanks for that too! But there again, I didn't sell the head work I did, and power is in the head!
I'm not at all happy about the "abortions" sold in the name of my nice design.
This system works by primary resonance, but in an interference (ie wave front addition) mode.
The primary resonance is ideally placed when the primary is about 19" long and about 42mm pipe diameter but a 38mm pipe will raise the frequency by about 10% so a change of about 250rpm.
However because the copies sold of this manifold are so dreadful and the primary pipes so unequal, the majority of these conversions end up with really significant flat spots all up the range....s you have to compensate by making a real trick engine usually.
(resonance becomes a factor at 2500rpm, a large increase in breathing efficiency takes place at this frequency, but if the pipes are made like that, this effect will be spread out all over the place between 2200-2800rpm which is MOST undesirable! It can be shown that as the pipe enters 1st harmonic (around 5000rpm) this will usually be the place where the system is at peak efficiency so you get peak power (in practice with a TR6 about 5500rpm)
Of course people will get out their pocket calculator and say this is all wrong, but you have to take into account the extra length added by the exhaust tract in the head too, as well as the fact it's a non crossflow design and each individual car has huge cooling problems....below....
Pipe resonance is enormously affected by temperature, so the ideal manifold will be so configured as to be cooled by the speed coefficient (cooling air from driving) as to "come on song" as it gets hot. The resonance of an exhaust system rises VERY substantially as temperature rises.....this is critical to engine performance.
It's called the "virtuous curve".
Lastly but not least this design of manifold is NOT AT ALL like anything done before for these cars, the majority of realisations I have seen have dreadful secondary lengths, the manifold can be said to run into back pressure between 6800-7500rpm, WELL BEYOND the rev range of most Triumph road engines, and inaccessible for a TR6...
So that puts paid to the argument about "it's only for cars with wild cams or race engines", this is simply a total failure to understand what is going on..
My manifold is OK in it's original design for those engines, but some optimisations were made on the racing engine (which was after all doing 100bhp/L@7900rpm), so much as to junk it altogether for a full race engine and develop a much better model.
This model was never shown or put in print for the reasons above....I didn't want other people taking credit for my hard work, by copying it....heck they even illegally copied my Tuning Book!!!!!