This is the first of what hopefully will be a series of in-depth product tests using data acquistion equipment to test with some semblance of scientific method. I'm still in the process of getting all the bikes wired for sensors but I thought I would share the initial impressions from me and another CRF450 owner on a comparison between the
Thunder Alley and the OEM
Honda canister. This is a real world test where I bought the product with my own hard earned cash.
Thunder Alley pipes are designed and built in the US by Bob Murray. Bob is a well known and highly respected pipe builder in drag race circles. Anyone who knows me is aware that I think many dirt bike pipe builders are complete posers selling shiny crap that is usually marketed with dubious "dyno data". Bob Murray is a rare exception to that rule and I for one am thrilled that he has turned his efforts towards pipes for our bikes.
Unlike most current designs the
Thunder Alley (TA) secondary pipe is a megaphone design leading into the silencer (see picture). I won't go into the specific pros and cons of megaphones at this point other than to say done correctly a megaphone design has the potential to produce excellent power characteristics at the expense of a pipe that is more difficult to produce.
Knowing how good Bob's work was in the drag race world I was to say the least curious as to how his design methodology would translate to the dirt bike world. I am really happy with the power characteristics of my stock CRF running Phillips B35 oxygenated race fuel and I had a hard time imagining any huge differences that could be found in a slip on exhaust canister. Eventually curiosity got the better of me and I placed a call to
Thunder Alley. My first pleasant surprise was I got to talk to Bob Murray directly. It's nice to talk to the person who designs the parts you buy. My second surprise was Bob's willingness to discuss his products without being pushy about buying something. I've never talked to anyone who was so confident in his product's ability to sell itself. I explained to Bob how I wanted to do a real world test on a bike fitted with data acquisition equipment to get a better idea of how the pipe effects the fuel curve and to more accurately measure performance changes. I needed an oxygen sensor fitting welded to the pipe and Bob was nice enough to make up a very slick fitting for me no charge. Outstanding customer service right from the start.
Each of the TA pipes is hand made by Bob. The welding is a work of art and the fit is dead on perfect. The funny part is the TA canister fits better than the
Honda OEM piece. I haven't weighed the TA pipe yet but my feel-o-meter says its a bit lighter than stock, but nothing major. The megaphone is made from mild steel with no paint, and the silencer section is aluminum. It has a cool works bike look to it.
I bolted the TA pipe up and noticed it was somewhat louder than stock, but it was quieter and had a much more pleasing tone than the White Bros R4 and the BBR pipes that OT and Okie run on there YZF250s. I felt the TA pipe had a proper race bike sound rather than the shrill bark that tends to come from most aftermarket four-stroke pipes. Far from a scientific observation just a preference on my part. I’ll be sound testing all these pipes versus the OEMs in the near future to quantify the real differences. .
Earlier in the season I had added two teeth to the rear sprocket in an effort to work around the somewhat flat low end on the CRF. It proved to be an excellent solution on our tight SX style practice track. I am in the process of readying my bike for a Motard race so I switched back to stock gearing.
My initial impression of the TA pipe was HOLY S what the hell happened to my bike. Even with the taller gearing it would pull cleanly from a much lower rpm, and would even pull a gear higher in a number of places. Clearing our big table top that has a short approach was easy from a roll-on where in the past it was iffy unless I had the engine revving high enough to get just the right drive. I did a bunch of laps and was thrilled, but the real test would be to cool the bike off and bolt the OEM pipe back on to test with. With the OEM pipe on it was back to lots of clutching and and lower gears. The difference reminded me of going from a stock YZF 400 to a high compression 420 engine. It's that dramatic.
After about 10 laps I couldn't get the OEM pipe off
fast enough.
I'll admit I really wanted this pipe to work well. I have a soft spot for real craftsmen like Bob Murray who buck convention and build the
right stuff rather than the shiny junk that is easy to sell. So just to make sure I wasn't overstating the positive points of the TA pipe I wanted another opinion. OT's buddy Eric showed up with his stone stock CRF450. Eric runs pump gas in his CRF and hasn't even touched the idle screw on his engine. He had never heard of Bob Murray or TA so he seemed like a good control for my mini-test. After he did a bunch of laps he came in to rest and I offered to bolt the TA pipe on and let him try it. Initially he was reluctant because he likes the way his CRF runs and he has enough experience from previous four-stroke ownership to have little faith in aftermarket exhausts. He relented and I bolted it up and didn’t change anything else. After a bunch of laps he came back in shaking his head and said “it’s like a different motorcycle”. He felt it totally transformed the low end and mid-range behavior of the bike, which echoed my feelings. Our track is tight enough that it’s difficult to really ring out the top end but neither of us felt it lacked top end drive with the TA. This will be tested more completely in the near future.
I didn’t change the jetting on either bike but I felt like my bike was a tad lean on the pilot circuit so I think there may be a bit more top be had down low. As I look at the jetting more critically I'll update this thread. Bob suggests that the main jet may need to bumped up a step richer on some bikes.
Basic test conditions:
Day 1 :
Corrected Density Altitude : 3990ft
Barometric pressure : 29.10
Temperature : 91f
Humidity : 54%
Day 2 :
Corrected Density Altitude : 3010ft
Barometric pressure : 29.20
Temperature : 80f
Humidity : 52%
Bike #1 - Phillips B35 oxygenated fuel (2.5% O2 by vol) , stock jetting with fuel screw at 2.5 turns out.
Bike #2 - No name pump gas, stock jetting with fuel screw at factory setting.
I’ll have a much more complete review with some super trick fuel curve, and acceleration data in the near future but hopefully this mini-review will answer a few questions for you.
Misc Likes:
- Allen head cap screws instead of pop rivets used to secure the exhaust can.
- Two minute installation so it's easy to switch back to OEM if need be.
- Like it or not megaphone exhausts sound SWEET
Misc Dislikes :
-
Thunder Alley sticker on silencer is easy to tear up.
- No
Thunder Alley sticker for my tool box.
- Now I want to spend $350 and buy a pipe for my YZF444
BUY IT IF
You want tons of low end and mid range performance for a bargain price and you don’t need a big name on your pipe to impress your buddies.
FORGET IT IF
You need a shiny pipe from a big name company to sleep well at night and don’t care about how your bike performs.
You ride in an area where any increase in sound would be a problem.
8 words about this product
Wicked acceleration, trick looks, pleasing sound, real value.
Thunder Alley
1010 East Lacey Boulevard
Hanford, California 93230
(559) 584-8109
http://taliaferro.net/thunderalley/
HONDA - CRF450 megaphone/silencer only - $250.00 (plus shipping charges)
Option: U.S.F.S. approved spark arrestor $45.00
YAMAHA - YZ426F (head pipe and megaphone) - $350.00 (Plus shipping charges)
Option: U.S.F.S. approved spark arrestor add $45.00
Thunder Alley manufactures exhaust systems for most brands of motorcycles. Please call Bob Murray at (559) 584-8109 to discuss your specific needs.
