Let's get this straight (from the designer)TR_6000 hat geschrieben:Trotzdem bleibe ich dabei, dass ein Phoenix 6-3-1 Krümmer etwas bringt, wenn der Motor ordentlich gemacht ist, z.B. PI-Verdichtung, mehr Ventilhub bzw. etwas schärfere Nocke etc.
Das beste Beispiel war aktuell Alex (HDTR661): sauber gemachter Motor mit PI-Verdichtung, 260er Newman, Rollenkipphebel mit größerer Übersetzung usw.
The 6-3-1 exhaust is SPECIFICALLY designed to be run with a camshaft of minimum 280 degrees.
This is how I designed it in 1982.
As you detune the engine more and more,you will get less and less benefit from the 6-3-1.
What I find unacceptable is totally anarchic and crap primary lengths that phoenix put in their system. This will never work properly and gives flat spots all over the place.
Between my properly manufactured manifold and a fake or bad copy we measured as much as 25bhp difference (in Australia), just swopping manifolds.
That's a HECK of a lotof difference between one manifold and another!
However:-
Using a 260 degree with almost no overlap would be completely pointless, on a 6-3-1, just like it would be with a compressor or turbo camshaft..
If you look at the timing order of a 6 cylinder at 240 degree intervals (per bank of 3) it's absolutely obvious why.
Such distribution problems result in centre cylinder robbing and exhaust cylinder fouling at overlap as soon as you start approaching 270-280 degrees.
I mean somewhere there has to be some design philosophy although of course Phoenix know ABSOLUTELY ZILCH about design...
They wouldn't know, because they stole the design and tried to cobble together a system exactly based on my old Mike Randall system prototype, -
I know this is the case because they took one of these from Cargraphic when I was working there, and also some stuff off Limos which CW was selling in the UK.
The result is EXACTLY the same problems of leaks and bad fitting that there were with MTP.
Mike Randall had a nice big back door, anyone could pop in and buy one of my old proto exhausts, isn't that so Mike?.....hey no need to pay anyone for IP is there??
It's how we choose to remember you RIP.
That is why the Phoenix 6-3-1 has EXACTLY the same design flaws & the same nasty leaky slip joints and the wrong primary and secondary lengths! Because it's obviously a bad copy.
WTF! Takes skill that does!
They copy it badly in STAINLESS STEEL of all things, just to make sure it's LOUD and NOISY and doesn't work properly, and then tell people to wrap it in exhaust tape....WTF!! (so it gets even louder!!).
Hasn't anyone heard you get MORE POWER from a mild steel exhaust and HAS to be force air cooled not wrapped in
tape!!!One would have expected these oddities to have been ironed out years ago, but of course not, because PHOENIX didn't copy the improved version...and people can complain as loud as they like for years, about nothing fitting, hitting the chassis and all, and impossible to seal but do they really give a damn! They got your money, and that is what mattered!
Now:-
In fact if you use an ORIGINAL cast exhaust manifold with the original dual downpipes but a less constrictive silencer & a 260 degree cam, you WILL get a much better result than with the 6-3-1.
This is a FACT.
The original manifold like on the spitfire 1500 is really quite good and gives excellent torque low down.
This will work all the way up using the 308778 Limo/GT6 cam to as far as the TR5 cam, which of course where it becomes "limit", giving that characteristic smelly lumpy idle again.
Of course these good bits are the first part people throw away!
A 6 cylinder with relatively small valves HAS to have a long duration camshaft, or it won't produce torque.
This ends up being a balancing act between wanting to get nice bright top end sports car power on a long stroke engine, and still keeping a nice idle.
Triumph got it pretty much right.
The small valves & larger engine cams the hot cam down as is well known, so that the 280 "feels" like 260,but with that nice shove in the back at 4000rpm.
Add a good head and you get 170bhp quite easily, as I have managed to do with 2 SU carbs instead of the Lucas Pi.
We have proved 280-298 degree camshafts on the 2.5L DO NOT result in any loss of low speed flexibility on a 2.5L road car, which is why the TR5 uses 280.
Of course on a small engine half the size, like the Spitfire 1300 this is a different matter.
As the engine size falls, the point of peak power rises, but I STILL manage to get superb torque at 3000rpm from one of those.
(95ftlb on just 2 SU carbs)
On my 43 cam, which is quite wild, we had peak power on a 1300 with Dellortos at 7200 (130bhp), 6800 on a GT6 2L pi (180bhp) and 5500 on a 2.5L (!)
This is a rule of motor tuning science.
A 260 degree camshaft even with the best head and TR6 engine in the world will NEVER give peak power beyond 4500rpm, no matter what lift you get...in fact short duration is the enemy of lift because you CANNOT get the inlet ramp sharp enough, or you get really bad wear.
This is why Newman cams are lousy designs, simply because they don't understand lift velocity and ramp angle.
Their ramps are sluggish, because they can't be otherwise.
As for the GT6 turbo engine above it was running a blow thru carb (like a Lotus) and 1.0-1.2 BAR boost. (280bhp from 2.2L)
The nitrous added an extra 100bhp.
I supplied the pistons & the camshaft.
