Thunder Alley CRF450 slip-on exhaust mini-review

[Rich Rohrich]

Originally posted by huffa
and wish he had an option that you could order it with it being plated or coated for x amount of $$.

If you read through my threads you'll see that he does offer a coating option. I think Bob Murray is aware that not everyone wants the raw steel look. I'll have the more details on Monday. The other option with this type of pipe is to send it to Jet-Hot for coating. They do great work and the prices are very reasonable.

 

[Swiss]

Rich,
Since I have been building custom 1-off meg systems for about 12 years now, I can appreciate that you have finally found Megaphones. The typical problem with most of the "production" megs from the So. CA companies in the past is that their tuning was often wrong. A GOOD meg system WILL provide a good general increase in performance in MOST areas of the powerband. A custom pipe/meg can increase power beyond that, and match the engine for tuning. Getting down to the last available hp is pretty hard to do, and would require adjustments for just about everything else that is tunable in the engine system. It CAN be done, but would require mega hours of Dyno/Track time and would stray from the "perfect" system with each additional mod that you made to the engine. IF you want to try it, a good meg system will allow you to use a LOT more carb than a straight system. In truth, most of the Tapered and stepped systems are just mimicking the tuning of a meg, but less effectively. Megs are sometimes difficult to fit correctly within the typical frame design, and doing so becomes a job for a good fabricator.
I will be looking forward to your testing results. Besides noise, will you be giving out the full dyno results? Looking forward to seeing your info.

Swiss

 

[Rich Rohrich]

Originally posted by Swiss
I can appreciate that you have finally found Megaphones.

Megaphone exhaust systems are far from a new discovery for me, but an off the shelf piece that works well for a reasonable price is a find though. :)

I don't currently have access to a proper engine dyno facility, and I have little faith in most chassis dyno setups and the numbers they produce so I won't be bothering with dyno results. Instead I'm putting together an acceleration test using an advanced data acquisition system. The idea is to produce real world, repeatable tests that focus on roll-on and transitional response of a product with matching fuel curves. Too many tests bolt on parts that modify the fuel curve and the testers get great increases or horrible results with no idea whether the it was the product or the changes to the fuel curve that caused the change. My hope is to control as many variables as possible to get an accurate guage of the functinality of the product under test.

 

[Swiss]

Rich,
It seems like even a chassis dyno would enable repeatable testing better than say a track condition where a few inches difference in a turn radius or a small weight shift during acceleration would influence the results. Good luck setting up a valid test without a dyno. I know that a lot of people will deride the dyno testing, but when used without dyno to dyno comparisons, a single unit could be valid enough to show good results that could be compared from run to run.
Swiss

 

[jescombe]

Swiss - there are a couple of Thunder Alley dyno graphs from my big-bore YZF at the end of this link -> dyno data. When I add the next runs, I'll put the rest of the TA details in.

The gain off the bottom was impressive, but I lost too much off the top end for Motard use. I'd like to experiment with some alternative pipe dimensions before giving up on the meg design, but every text book I read for inspiration has subtly different formula for pipe tuning.. :think:

 

[Swiss]

Thanks, I will look them over. Can you give me valve diameters, and you are running the stock carb right? You shouldn't really be losing anything off the top end. Needs some study of the info.
Swiss

 

[Shawn Mc]

IN my seat of the pants test, as unscientific as it is, I didnt notice any loss anywhere. Top bottom mid, all were much stronger. The biggest change I noted was the linearity, if that's a word, of the power, as opposed to the hit it had with the White Bros. T-4 or the stock pipe.

 

[jescombe]

Swiss, Yes - I'm using the stock 39mm carb, have run a stock (27mm inlet & 28mm exhaust) head, and a ported head with 1mm oversize inlet valves. The head configuration didn't seem to change the overall characteristics of the pipe.

Shawn, Maybe it's down to my engine configuration, I would certainly like to get it running stronger on top too. My Akrapovic pipe is gorgeous, but the silencer is long & vulnerable (like the Arrow pipe) - I gouged it at the weekend making an over agressive pass. :|

 

[Patman]

What a GREAT experience! I called and talked to Bob Murray last Friday about a pipe and then decided to buy it Monday. Well I left a message on his machine and Bob himself called me back, took the order, verified every detail and then said to send him a check or money order. No messing around with an order taker that can't hardly speak english let alone answer a technical question. :)

 

[sfc crash]

rich, i'll be interested in your db tests, as i understand it, you could have two pipes, both with the same tail pipe db level, but at a distance a greatly different level becuse of freq of the pipe. i'm thinking that a lower freq note, tho sounding/emitting lower dbs at the pipe, would carry over a larger distance than a higher freq at the same distance. maybe i'm splitting hairs here .

 

[Jaybird]

Lower frequencies do in fact carry farther than higher frequencies. Exactly the technology behind the Navy's new sonar.

 

[Shawn Mc]

Have you ever heard of Power news? Check out this link www.mototuneusa.com/success_stories.htm. Im dubious, but Im also curious. I understand velocity and how that can effect ultimate output, by simply carbureating better. Now a fuel injected engine, I dont get it. But smarted people than I are a foot!

 

[TMÒÓ]

I put a TA pipe on my son's '01 XR50. It added a little power, for being a 50cc engine with my fat a$$ on the back. What I did notice is that it smoothed out the power making it easier for him to ride. Now, the sound is great. His bike sounds like a baby thumper. We take it to the track and everyone can't believe their ears. Everyone just stares at the bike with huge smiles on their face.

I am in Fresno, CA and most of my friends, who race, swear by these pipes. I hate when they pass me because I eat a roost like you cant believe. The bikes shake the ground as they go by. He has worked real hard in getting the noise down, close to OEM db's. Bob is a great guy and will work with you to get it right. We also put one of these on a '02 <a href="http://www.dirtrider.net/cgi-bin/clickpro/click.cgi?id=10" target="_blank"></b>Honda</b></a> 400EX. WOW, what a difference. The quad pulls from the time you roll on the throttle, all the way up. It is still pulling even know you feel the quad is going to explode.

Hopefully, I will build them a new website as soon as we can get all the updated info on which bikes he makes pipes for. I have a working model but am waiting for the go ahead from Bob. It will make it easier for customers to get in touch with him.

 

[Smitty]

Rich,

Have you done any further testing of your Thunder Alley vs. Stock? Namely how loud is it? Are you still convinced by the performance? I think a wider powerband and hefty low end could only improve this thing.

By the way, had 5 lap, 40 mile battle with a guy Sunday in wide open grass track and tight trees all covered by freshly moistened and perfectly bermed soil. Is there a better feeling than stretching the throttle cable on one of these babies while it blows out of a perfectly carved arc and launches down a 50 yard straightaway. Need bigger brakes!!

 

[Rich Rohrich]

Originally posted by Smitty
Rich,

Have you done any further testing of your Thunder Alley vs. Stock? Namely how loud is it? Are you still convinced by the performance? I think a wider powerband and hefty low end could only improve this thing.

Between and injury and crappy weather I haven't done much riding in the last 6 weeks. The only testing has been riding the bike with the TA can and tweaking the jetting. The more I ride it the more I like it :)

If my batteries arrive in time I'll have some DAQ data on the fuel curve this weekend. Okie has a sound meter now so we'll do that testing and compare to OEM this weekend as well.

 

[Smitty]

Sounds good. Thanks.

 

[techman]

If you want to get fancy with your sound testing, set up the SAE1287 rigging and tap the sound meter output into your data acquisition system so you can get not only dBA vs rpm, but the throttle opening as well for a bit more eye opening data. It would be neat to see the SAE spec rev dB as compared to the highest values when the throttle is blipped to peak out the revs, i.e. like juicing it out of a corner, off a jump etc. The less fancy way is just take multiple manual readings all the way from idle up to high revs, perhaps at 1000 rpm increments.

gratuitis dancing banana :yeehaw: just had to, it's so entertaining

 

[Rich Rohrich]

Originally posted by techman
If you want to get fancy with your sound testing, set up the SAE1287 rigging and tap the sound meter output into your data acquisition system so you can get not only dBA vs rpm, but the throttle opening as well for a bit more eye opening data.

The sound test equipment that will output to my DAQ system has already been ordered. It should prove interesting.

Smitty - we didn't get the opportunity to do any static sound tests over the weekend but we should be able to this coming weekend.

 

[MoGwai]

Hi,

I am riding a 400EXC, looking into the TA full system with ceremic coating. Email Bob about the header, he noted that it is not a tapered header but a straight thru one.I like riding with minimum gear change thus my bike is always revved out.

I would like to ask, wether the TA pipe helps with the over-rev of my bike or its just improving the low-end with a drop in the top and over-rev? The straight thru header pros and cons against a tapered header pipe. :think:

Thanks for all comments.

MoGwai

 

[Shawn Mc]

Mogwai, Id be surprized to say the least if you lost any top end with a Thunder Alley pipe. Ive heard guys say that they run out of top end only to see that they are painfully lean on the main jet. They go up a size or two and its "how cow" this and "I almost flipped it" that. You'll get more out of a reverse cone meg with a straight pipe, than a tapered head pipe with a regular straight through glass pack muffler.

 

[Rich Rohrich]

Thunder Alley has a new website www.thunder-alley.net

Now that DW02 has come and gone we'll try and get back to the business of pipe testing. Sounds and some performance testing info should be coming up soon (weather permitting :) )

 

[wy4tt]

rich, have you been able to record any data on the TA pipe yet? i talked to bob a few days ago, and he's a great guy. i was really impressed with how much info he was able to give me over the phone. didn't seemed rushed at all. when i asked him about sound levels and the new 96 db limit being imposed in CA in '03, he said he's working hard to come up with a fix. he said retrofitting units should not be a problem either. he said with the spark arrestor in, the sound is down to 97-98 db. i ordered one with the SA. anyway, just curious if you'd had time for further testing. by the way, i really respect the scientific design of your testing. much appreciated.

 

[Rich Rohrich]

Sorry I must have missed this when you originally posted it.
The weather didn't cooperate in the late fall so testing will resume this spring.

 

[tchamberlain]

Does this company make anything for 2 strokes?

 

[Rich Rohrich]

Nope. Thunder Alley builds four-stroke singles pipes exclusively. But they will build pipes for ANY four-stroke single. ;)