Question....

[hyyyper]

....what is the minimum speed a coaster has to stay above the making a good speed b&m twister, is it like 30kph or more like 50kph?

Depends on the inital speed. Take for example you are driving a car of a straight bit of road for 10 minutes at 80 mph (180kph?) and then you turn into a village with a speed limit of 35 mph (78kph). Although you are still going quite fast through the village, it actualy feels that you are going painfully slow in relativity to driving 80mph in the first place.

Remember that coaster design is not much about absolute speed values, but more about changes of g-forces. You might also want to provide tight support structures and near tree- / ground-hits to create a 'speedy' impression (while actualy going quite 'slow').

[hyyyper]

you both aren't helping me either, so i'll put it this way, for my current coaster i made the trackword so that the speed doens't go under the 30 kph, is that fast enough or you i highten the limit to 40 or 50 kph?

There isn't any defined speed that a coaster shouldn't go under. It is track specific. As long as the ride is still delivering thrill at whatever speed it is traveling at (use the methods Red described for slower coasters) then its good.

[Dirk_Ermen]

when i drive on my scooter and drive a part 55km/u, i'd love it, but when i'd have to slow down to 30 again in the cities. I'd feel very uncomfertable. I'd really feel then like i go WAY too slow. But before i rode 55km/u, 30 seemed pretty fast to me. Same effect on a coaster. If you go first very fast and then suddenly slow down WAY too much it feels like your going really slow, but if you let it slowly build down, so 55, 53, 51. It keeps the fast speed feeling better.
But what i should do is just connect some time the track and ride it. If you think a part goes way too slow, speed it up by lowering the area a bit, you could add objects (supports, trees, 3ds) To give a speed feeling. So going though a mess off supports with 50km/u feels faster then going 50km/u on a straith piece of track without anything around you.

[Oscar]

it should go 500 mph, that'll make it seem fast [:D]

[hyyyper]

"...make it SEEM fast..." <-- i don't think that is possible to acieve in NL, but the lowest speed for now is 40 kph, and the pacing is little hard to check cos it's one blank ocean for now...