I understand that long trumpets give good torque figures and short trumpets tend to give more HP. can the two be combined? the reason i ask is that i have a set of bike throttles which you can buy trumpet kits for but the picture seems to show two longer than the other two or is this a deceptive picture.
in pvw this month theres a car with an r32 engine with three long trumpets and three short, could work or might just be for show.
the way the ports are close together i think is the reason as the trumpets flair is in the way of the next ports trumpet. does that make any sense
Think you are right, he would have to cut away sides of the flaired fronts if he wanted to keep em same length Do not underestimate the importance of trumpets length Just today i'v been extending mine because my engine really likes it Did a test drive back to back with short trumpets and than with long ones as in pic and difference is unreall! Engine feels allot more torquey across the rev range especially low down and throttle response is instant Next week i will do rolling road runs to see exactly how much difference it makes Few pics
Heres something that might shed some light on what happens when trumpet /runner length is altered Affect of intake runner length - Short intake runners (the trumpets in your case) [shown in pink] Basically give you relatively flat torque curve and high hp at high rpm you don't want to make the lengths to short otherwise ure engine might not rev high enough to make the high hp on offer by lengthening the runners / trumpets, the peak torque value is brought further down the rpm range, the torque band is made narrower, and the peak value is higher [see yellow line] you can make the runners/ trumpets too long of course (which the turquoise line is heading towards)
As you can see power starts droping off at around 8400 rpm which is quite high, most vw engines people use here dont rev that high so nothing to worry about Gain accross the rev range bellow that is well worth it
oh yes sorry that isn't for a VW engine it was just to demonstrate short and long thats from a 4cyl motorbike engine on a test bed
Thats why when using bike itb-s on a car engine you shouldnt use original trumpets unless your engine revs to 14k rpm
yup thats exactly it matey probably a lot of dissapointed folk who have done that have you got a pic that looks down one of the trumpets by any chance?
when i did my test work on different lengths i found that you needed to change the map in terms of fueling and ignition timing every time you used a different length this was on a motec m400 ecu so you might have an easier time looks nice all the way to the valves mr. smudge, no steps in diameter and such
my brother did that on one of his motorbikes (took the throttles off, trimmed and odd edges and knife edged the the plates)... he said it worked well. nothing to loose i suppose
well even tho its only a small area... it is currently a flat face which will cause air to go around ... possibly creating a teeny deadzone either side of the plate knife edge should allow air to flow close to the plate surface i haven't put this through CFD or anything I'm purely going off what people have found and put on tech papers
another issue could be the turbulence as it appears to have a pretty large cross section area. can you get spare plates so you can test? might be weoth trying that on the dyno test too
