We’ve been noting the importance of using properly baffled mufflers for many years, and with the Milwaukee-8 engines we’ve found they are even more exhaust sensitive than the Twin Cam design. We spend a large amount of the day going over these differences so we wanted to put an easy to understand test together that may help choose the proper components for your application. Muffler choice can make or break the entire combination and the current trend of large, open baffles is unfortunately the opposite of what these motors want with most configurations, especially when you go to an aftermarket cam. We’ve seen as much as 30+ Tq loss in the lower RPM’s and these excessively large baffles contribute to poor response and tunability. If you have mufflers with these excessively large baffles, big tapered, or stepped cores they are costing you considerable performance, you cannot bend the laws of physics. Reversion is effectively reducing velocity that is essential to low-mid RPM performance & response. For info on exhaust theory & design some of the best written resources are the tech articles from Burns Stainless.

The following testing is going to document the specific differences in performance between a muffler with an overly large baffled muffler (were calling it muffler “ABC”) versus a properly baffled muffler for this application (conventional core with removable secondary inserts in place). The test vehicle in these tests is a 2018 H-D FLHTK Ultra Limited. All testing was done on the same day in the Fuel Moto Dynojet test cell and each combination was fully tuned with Dynojet Power Vision. We tested the following combinations:

• Stock headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune
• Stock headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune
• Jackpot 2/1/2 headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune
• Jackpot 2/1/2 headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune
• Wood WM8-22x cam, Jackpot 2/1/2 headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune
• Wood WM8-22x cam, Jackpot 2/1/2 headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune

Test 1) Stock headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune



Test 2) Stock headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune





Note the difference below comparing the two mufflers with the stock head pipe. The larger baffled mufflers are making measurably less torque than the conventional baffled mufflers but performance could be considered reasonable in this application.





Test 3) Jackpot 2/1/2 headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune





Test 4) Jackpot 2/1/2 headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune



Note the difference below between the two mufflers when you replace the head pipe with the non catalyst pipe. Numbers increase slightly but there is a more defined dip with the larger baffles. The merge collector in the 2/1/2 head pipe is helping the deficiencies. Throttle response is noticeably different between the two setups as well, the larger baffles combination feels lack response.





Test 5) Wood WM8-22x cam, Jackpot 2/1/2 headpipe, Muffler “ABC”, Stage 1 air cleaner, Dynojet Power Vision tune



Test 6) Wood WM8-22x cam, Jackpot 2/1/2 headpipe, Muffler “123”, Stage 1 air cleaner, Dynojet Power Vision tune



They made the same torque! but wait a minute this is where the testing gets really interesting. When you add the aftermarket Wood WM8-22x cam to the mix it really separates the two mufflers. There is now a huge defined loss in low RPM power; the motor is simply not happy and does not respond with the large baffled mufflers in the lower RPM’s. Your looking at a difference as much as 20Tq in the lower RPM’s, throttle response is also poor. Riding the bike seat of the pants difference is night and day; mufflers are the only difference.

Consider the WM8-22x is one of the strongest low-mid RPM cams on the market. If you were using another cam that is not quite as strong on the bottom or a different pipe without a properly designed merge collector; the results of the larger baffles would be even worse. The mufflers we tested were not even the worst offenders we’ve seen, (yes we’ve seen even worse). Also consider each of these combinations were properly dyno tuned and properly tested.



Below you will find an overlay of each of the runs from this test. Most interesting to note is the WM8-22x test with the large “ABC” mufflers made less power below 2600 RPM than with the stock cam, head pipe and the same mufflers!

 

While I agree some cams are more sensitive than others the following link to cam testing clearly shows the 22X in this test comes in 5th of the 6 cams tested for HP and Torque, not what I would call the top of the list. The exhaust used was the same for all testing and has been tested by others as well, to be a top performer for Low RPM Torque production. That said, a more accurate statement is the the Woods 22X cam is very sensitive to exhaust while others are not so much so.


https://www.hdforums.com/forum/milwa...l#post18015218

 

I would like to know what mufflers were tested

 

Fuel Moto, I think the underlying message here is....Congrats on your continued success and the exponential growth of your business. You must be doing something right to be the industry leader. One could only sell BS components for so long without being called out. This is obviously not the case with Fuel Moto. You guys have been rocking performance for a decade, top in customer service as well. Again, Congrats!

 

If the mufflers have 2.5" or larger baffles, excessively large stepped or tapered cores chances are performance is being affected one way or another. We diddnt name the mufflers specifically in this test as we have long standing relationships throughout the industry with many of these manufacturers, some of our own mufflers will even do this if you remove the inserts and run them open in various applications. In the end it comes down to what the user wants for sound, looks, and performance; it's our aim to help them get their bike to run its best.

 

Strictly in the spirit of discussion, not tryng to be a d1ck, but...

I would give up a bit of peak TQ to have more TQ at the lower end. The charts in your thread have less of a plateau and less TQ at lower RPMs (If this observation is incorrect, by all means correct me). Not sure what exhaust/mufflers you used, but Jamie's test did show that choice of muffler dramatically affects low end torque, at least for the 222-X

 

I chose the WM8-22x cam for this test as its Fuel Moto's most popular bolt in cam, we work with the 22x extensively and know precisely what it does with most exhaust systems on the market so it was a good fit for this test. There are no doubt a lot of great cams; we've done hundreds of M8 cam swaps of many shapes, sizes and colors firsthand at our shop; when we have a bike in our hands we make it job #1 to ensure when we roll the bike out the customer is completely happy with the results. We've been on HDForums since 2007 posting info, testing, & dyno charts to give the the straight scoop how things are done at FM and we hope it's helped the community here for the better, we've met a lot of very cool people (and some bitter ones too). End of the day our customers and what goes on at Fuel Moto is what matters, not what someone else has tested or their claims.

 

Excellent work and findings here Jamie. You guys have given me the confidence in my recent purchase from Fuel Moto. When we spend this kind of money we always look for the most bang for the buck. These kind of post are great for this! Thank you!! Looking forward to my Stage 2 w/ Jackpot 2-1-2 Stainless Steel Headers, S&S MK45's, Zipper's Redshift 468 cam,, S$S Pushrod's, tappets, tappet guides.

 

Just for discussion if you look the charts over and compare them point by point you will find that they compare to many other dyno's done across the country. One must be careful in looking at pictures, as the way they get shown effects the way they look. Just the same as looking at a print in Landscape versus Portrait. The same data looks different when you use a Wide Screen Monitor versus a Normal Monitor. Now if you go beyond just the dyno and go to real world testing as was done in the noted test, it also showed the 22x was not as quick on the street in the real world and finish in the lower half of the testing. That supports just what the dyno showed as well as what the rider felt. Its all reported right in the thread and the mufflers and exhaust are also stated in the noted test data for all to see.

One thing to note is where the dyno pulls start as you are seeing one set of test where all the pulls started at ~ 1500 RPM and the other at ~ 2000 RPM. We have been here doing HD EFI testing and tuning since 1995, so you might say were the oldest and most experienced ones around at doing this and we've seen plenty over all these years. The thing that always shows in the long run is how they run when tested on the street and track where they really get ridden. The dyno is a very good tool when used correctly and shows where your at as long as you use it as a tool correctly. My point here is not to say the 22x is junk, it's just not near the top of the pile either, and it appears that its possibly more sensitive to changes than other camshaft offering that are out there. I've seen plenty of other camshafts in the M8 applications make near the same dyno runs across the country when using Fullsac, D&D, Bassani and Maganaflow exhaust too. So why is it that they can but the 22x cannot?

 

Fuel moto,

Will cvo muffler heat shields fit on your street outlaws? I saw one of your recent pics of a customers cvo and it had heat shields on the header but not on the street outlaws (black), looked pretty weird. They are 4 inch so I assume they would fit or am I incorrect? Thanks.