Hydro Thunder (Frames and Fields per second)

I have a question about Hydro Thunder. Most NTSC games I am getting about 30 frames per second as measured by FRAPS (60 fields per second as measured by PJ64). However Hydro Thunder displays varying framerate. The framerate often reaches 30 frames per second, but also in complex scenes dips to around 20 frames per second. I sometimes have seen in games frames dip below 30 when the field dips below 60; this is the case in CPU limited situations. However, what I am seeing in hydro thunder is the fields per second constant at 60, but the framerate fluctuating between 20 and 30 frames per second, which I have not seen before. I have tried all kinds of video and audio plugins; makes no difference. My CPU/graphics card combo is pretty good and if I unlock the frame limit in PJ64, I can get up to 100 frames per second, but with the frame limiter on I only get between 20 and 30. That raises the big question. Why the framerate dips to 20, especially if the fields per second is always at 60? My computer has pleny of horsepower as I can see when I unlock. Is this how the computer is emulating the N64 which also had this problem. Are the dips because the computer is emulating the N64 cpu speed and at this emulated CPU speed the "N64" cannot keep up? If so is there a way to overclock the N64 cpu, like you can do in chankast? Any tips or suggestions on how you can keep hydro thunder at 30 frames per second without the dips? Also, I noticed that wave race only runs at a constant 20 frames per second (FRAPS). Any way to increase?

Solution Found:

Change counter factor in PJ64 from 2 to 1 under game options menu.

After doing that the framerate stays at a constant 30.

Also, there is Midway Arcade Treasures for $9.99, which contains hydro thunder (DC version), SF Rush, SF Rush 2049 (DC Version) and 25 more games.

But only runs at 640x480 and without analog controller support.

http://www.gamestop.com/product.asp?product_id=646294