danST Engineering are pleased to offer this high quality lightweight aluminum spun trumpet kit for fitment to Yamaha 4XV R1 Carburettors. Complete with universal Cuff and clip fitting kit. Features:
40mm Bore x 90mm Overall Length (50mm also available, see our other items) Aluminium Trumpets (x4)
25mm Long Discrete single-ply silicone joining cuff (x4)
9mm wide stainless mikalor clamps (x8)
(carburettors are NOT included, shown for illustration only)
danST Engineering began manufacturing these trumpets due to a shortage of available and reasonably priced trumpets for fitment on our specialist carb and throttle body conversions. These trumpets are suitable for a wide range of applications with cylindrical carburettor or throttle body inlet to allow the silicone to be clamped around. Note that the silicone will stretch 3-4mm to fit larger diameters.
Why fit velocity stacks or 'trumpets'? A radius at the inlet of an inlet tract serves to smooth and even out the flow into each intake runner. You will note that any manufacturers standard equipment will feature such a radius for this reason. Without this radius power and torque can both be negatively affected. Additionally when tuning for power increases a longer inlet tract (the distance from inlet to back of valve being the important length) has been found to be extremely beneficial, especially on a lower revving car engine.
Below are links to two different engines fitted with two popular bike carb kits (one 1800 zetec with R1 Mikuni carbs, one Ford 2.3 Duratec fitted with ZX9R carbs). The lower lines are both carb sets without trumpets and the higher lines are when fitted with our 50mm trumpets. In both cases significant performance increases (typically 5-9bhp) are seen between 3500-6000rpm when the carburettors are fitted with our trumpet kit. Additionally the torque curve is seen to be much smoother. Note that the Duratec is making peak power very low in the RPM range due to a very restrictive exhaust (soon to be replaced!), but the effect of the trumpets on engine performance is clear. We see so many bike carb conversions running without any trumpets (bike breakers often remove them along with the original bike airbox) - ALL of which would see the benefits highlighted below, probably the cheapest power you can find!