Product Evaluation . . .
Topic: WBBrian's Powervalve
TEST BIKES: a) 1992 1240 - WBB skis, Skat-Trak 11-13 SS impeller, stock engine, stock tall exhaust, airbox removed
b) 1987 Silverstreak - stock skis, Skat-Trak 11-13 SS impeller, stock engine, stock tall exhaust, stock airbox
c) 1986/91 Tomcat - stock skis, bronze impeller, 86mm slightly-ported motor, short diffuser, tall can, stock airbox
d) 1991 Tomcat - stock skis, stock impeller, stock motor, tall exhaust, stock airbox
Installation is a breeze. Takes about 4 of 5 minutes to change out the exhaust pipe. If you bike has the foam removed on the left side, then it's even quicker. When doing this operation with the bike in the water - be aware that when you lift the exhaust pipe out of the lower rubber fitting, there'll be a HUGE gush of water (since it's below the water line). So, have the new pipe (with powervalve at the bottom) in hand ready to put back in immediately. When you begin to tighten the clamp on the lower pipe, remember to tilt it slightly outward so that the pipe doesn't vibrate against the head bolts (this tip works on all wetbikes by the way). Tighten both clamps securely and you're done.
First thing I noticed is that the low end/mid-range seems to be improved slightly. This is a subjective thing, but the motor just seems to be more "crisp". This is both an audible thing and a seat-of-the-pants thing. Didn't notice any loss of power or speed, but the GPS unit saw exactly 1 mph loss across the board on the top end. Note: That loss is EXACTLY OPPOSITE of what the seat-of-the-pants feeling told me. I felt like it gave more power AND speed on all bikes I rode with it. However, the GPS unit we used was extremely accurate and consistant. Also, the tiny tach showed 100 rpm drop (not what we expected).
Is this powervalve a worthwhile upgrade? To answer that, you need an acid-test and I found one. I was pushing the scales to 273 the morning we went out testing (not including wetsuit or life vest). Here's something I noticed both on the Silverstreak and the 1992. When I had the bikes tilted over (just beginning to drag my left leg good) - they DIDN'T BOG and drag off speed like they used to. Both bikes were able to maintain their speed. This tells me that there was more power (torque) being made to keep me in such a tight turn - and at speed. Was most noticeable on the 1992.
I think this upgrade is excellent - and not just because Brian's a great guy and a good friend of mine. Rather, I think we saw noticeable power increases right where it's needed. The cost is 1 mph off of the top end. Just like a stainless Skat-Trak impeller, I believe this is an excellent trade-off.
If you want pure top end, run no powervalve. If you want more bottom-to-midrange power, then put on a powervalve.
Thumbs-up on this upgrade in my opinion. I'll take more usable power over top speed any day.
Copyright 2012 Capt'n Obveeus