I'm using ktorrent-2.0.2-3.fc5.i386.rpm

it seems like ktorrent could only achieve up 5 concurrent chunks download...

This has causes my download speed to fluctuated a lot and slow

how does ktorrent decide how many concurrent chunks to download?
OR
Can i increase the number of concurrent chunks download?

UPDATE

After i've increased the number of upload slot, now the concurrent chunks download shot up to 20

any relation of changing the upload slot number and download chunks number?

But still even with 20 concurrent chunks download my speed still fluctuate
e.g (in KB) 16, 10, 18, 5, 2, 6, 0, 15, 0, 5, 13, 12, 16, 15, 3, 2, 1, 0

I'm sure i've done a correct port forward on my smoothwall router and open port in my linux firewall. Both azureus and emule works fine using the opened port

Initially the number is limited until you have 4 chunks, this is used to start sharing quickly.

But for the rest of the download, the number mostly depends on the number of peers who have unchoked you. Increasing the upload slots can cause more peers to unchoke you.

It is also limited by the memory usage parameter, you can try setting that to high.