I have a set of bike throttle that im going to get sorted to fit my 2.1 8v, Few questions 1, what is the angle of dangle of the carb manifolds compared to the head? 2, How long is the inlet system, from trumpet to head? 3, how long is your intake trumpet?
there was a great thread on vortex about this, cap'ndub i think did it all had the throttles in a downdraught position, and had figured out the harmonics etc
i had a look earlier, but couldn't see it either, in the rev ranges you will be looking at they thought the typical throttle body manifolds would be too short his was a J bend type thing with the bodies vertical was in a mk1 8v, and originally posted in the mk1 forum but must have been 2 years ago now
im going to try and keep it something like the weber manifolds and weber setup. just wanted a few measurements doing.
The general rule of thumb on a competition engine is to have the inlet tract length at around 320-330mm, measured from the end of the trumpet to the valve seat. The generally available manifolds (Mangoletsi) for the 8v are around 3 inches (75mm ish) long. Measure the length from the valve seat to the manifold face of the head with a bit of welding wire (I've got it written down somewhere from when I measured mine but it's easy enough to do), add the length of the throttle bodies into the mix and subtract the total from 330mm to get the required trumpet length. You could have a manifold custom made from tubular steel in a more downdraught format in conjunction with a commercially available trumpet length to achieve the same result. The main problem is the clearance between the head and the bulkhead, you wont get much more than 330mm in there, and thats without filters.
The Weber type manifold's work fine, even with the bends in them (I use one at over 190hp so it should suit yr road type engine without any problems). In the case of the Mangoletsi manifold (the most common one available in the UK), it can be made to work fine when ported out, it just need's a fair bit of work. Rowlands manifolds in South Africa make one for the 8v, maybe better to start with.
im not sure on the spacing of the bodies, However to recreate something similar would be nice, I dont really want to start buying a manifold just to cut it up, its not like they are cheap! where as a pb manifold is!!
I'd imagine having the trumpets pointing into the cabin must make for a pretty loud time in the cabin? How impractical would this be for long distance travel?
It does... and very !... especially in a striped to the bone MK1 Would'nt be as bad in a road trimmed MK2, but I'd still say it would get tiresom after a while. I'd certainly run an air box as a minimum with carbs or t/b's for regular road use, or stick to a plenum with the metering head removed and mapped on a throttle pot... I'd still expect to see 160-170hp plus strong torque from a 2ltr based engine with all the right bits.
