Kawasaki Ninja 400 Exhaust Dyno Shootout!

***This is important, please don’t skip over this:

Before I just post a bunch of graphs of dyno runs, I want to explain a few things.  Dyno charts can be very misleading without some back story and more complete information.  First of all, dyno charts are generally only printed for the results at 100% throttle.  There are also different results for each throttle position, and these are all tuned separately, so the tune you are looking at on a dyno graph, is only a very small representation of how the bike is running, and really only useful for comparisons like this.  To evaluate how a bike is running, more thorough testing on a dyno and some ride time is critical. Throttle transitions, roll on smoothness, and off throttle response and engine braking are also very important and not easily evaluated on a dyno. Through all of my testing, I have tried to make the tests as scientifically fair as I could.  Tried to stick to apples to apples comparisons and remove as many variables as possible. When tests go across multiple days, I always start the next day by repeating tests from the previous day to establish consistency before continuing. If I can’t establish consistency, I figure out why or start over. But, there are a lot of variables with dyno tuning motorcycles. There can be big differences with tuners, fuel, even bikes of the same model, and dynos and O2 sensors can show significant variation from one to the next, and bikes and dynos can perform very differently at different operating temperatures to name a few. Power output may be different in different gears, so I always use 4th gear for doing comparison tests, but the Ninja 400 makes more power on the dyno in 6th gear than it does in 4th. Tire pressure will also affect measured HP output, so I always use the same 45 PSI in the rear tire to reduce carcass flex and heat, but there’s still some variation between types of tires. Because engines perform better as they heat up to their designed operating temp, it’s normal to take a series of pulls on a dyno and watch the numbers increase until they stabilize before using the pull as a reference. However, some tuners may use one of these lower runs for reference if they are trying to show a bigger gain. With the Ninja 400 on my dyno, this seems to be around a 1.5-2HP change as the bike and dyno warm up. I generally don’t even record this warmup process, but so you can see, here’s a series of pulls from my 2018 Ninja 400 as it warms up from the first pull to the 12th pull:

There is also something very important called Correction Factor, identified with a CF: at the top right of Dynojet charts. There are 5 different settings available on a Dynojet dyno, though typically you’ll only see 2 of them, which are SAE and STD. SAE is the current industry standard, but a lot of tuners will still print dyno charts in STD correction because the numbers are always higher, which is a bit misleading to customers. There are lots of good articles detailing the differences online, but here’s the quick and dirty explanation. Engines always make more power with cooler, denser, dryer air. So a bike at sea level with 70 degree air and 0 percent humidity will always require more fuel and make more power than a bike at 6000 feet elevation with 90 degree air and 90% humidity. Correction factor is a calculation applied to power numbers to “level the playing field” so engines can be compared from all over the world as if they were on the same dyno, in the same place, under the same conditions. SAE Correction assumes 77 degrees F, 29.23 inHg and dry, 0-percent humidity air, while STD Correction assumes 60 degrees F, 29.92 inHg and 0-percent humidity. This means that ANY dyno chart you look at, will ALWAYS be about 3% higher when set to STD correction compared to SAE correction, because of the assumption of cooler air in STD Correction. It’s rare that anyone will ever show an Uncorrected dyno chart because in most places in the world, conditions are less than optimal and numbers will be much lower and vary a lot from day to day. But the reality is that the Uncorrected number is what the engine is ACTUALLY making at that time, under those current conditions.

Here’s an example, below is the same 2 dyno runs from my Yamaha R3 Superbike with the only change being the Correction Factor calculation changed. You don’t have to change the correction factor and do another pull, it’s just a calculation applied to the data, so these are applied to the exact same 2 runs in each picture. See the increase in power in both runs when switched to STD correction? Free horsepower!

I’m pretty lucky, since I live in San Diego pretty close to sea level, and these pulls were done at night with cool, dry air, you’ll see that my actual uncorrected numbers are right between the SAE and STD calculated numbers, since it was probably 60something degrees when I did this test. Usually you’ll see the uncorrected numbers much lower than the calculated SAE or STD numbers:

To illustrate how dramatic this can actually be in different areas of the world with different elevation and temperature, here’s two charts from a close friend’s dyno while doing some of our Ninja 400 SBK testing showing the same two dyno pulls with SAE correction and then uncorrected at 7000 ft elevation where the air is much less dense than the corrected assumption of sea level, power is actually down 23% from 54.22 to 41.50, that’s a pretty dramatic difference:

Got it? Good.

So, now that you’re a little more informed, I’ll proceed. I’ll use SAE correction in all of my charts for standardization, but any time you look at a dyno chart from here forward, be sure to check the Correction Factor used, usually in the top right, to see if someone’s trying to pull a fast one on you.

Before we had officially partnered up, Jeremy Toye and Ninja400R.com gathered some good data already testing a number of exhausts for the Ninja 400 and reviewed them in this video below. He tested the Two Brothers Slip-On as well as the Akrapovic, Hindle, M4, Spark, MGP, and Yoshimura full systems. This video is also a great reference for some of the sound differences of various exhausts. The Hindle system for example, isn’t the best performer, but has a really unique and awesome growl of a sound when used without the quiet insert:

But, this exhaust shootout was only done on a MotoAmerica Junior Cup spec bike with rev limit in place. Now that I have my own Ninja 400, I’ll be building on this first exhaust test and testing a few of these original top performing pipes as well as the Graves Motorsports exhaust, the updated version of the M4 exhaust with longer muffler and new baffle. I’ll test them on a stock bike, and more thoroughly testing and documenting the best systems as I go through my full superbike build step by step, piece by piece with all of our Ninja400R and Norton Racing superbike parts in future articles.

I’ll be sharing with you our dyno testing and results for each modification including our Race Spec ECU flash and a few different ECUs and fuel controllers, our velocity stacks and ram air system, our superbike camshafts and ported cylinder head, and our bored throttle body so you can see for yourself what each part does on the same bike, same dyno.

Bone Stock Baseline

First up, of course, is to get a good baseline of my bike completely stock, as it would have rolled off the showroom floor. Stock exhaust, stock air filter, stock airbox with stock snorkels in place, untouched engine, stock chain and sprockets, you get the idea:

My bike is a 2018 model Ninja 400 non-ABS with about 1500 miles on the odometer and it made just over 45hp with the best run being 45.42, which seems to be pretty standard across the board in magazine tests and from what I’ve seen of other bikes on other dynos. So that’s good.

How much difference does the air filter make?

Ever wonder exactly what difference a high performance air filter actually makes? Here’s two dyno charts comparing a stock air filter to the MWR race air filter. The first test was done with just a Two Brothers slip-on exhaust and everything else stock with the OEM snorkels still installed in the airbox:

You can see, there’s really no performance difference between the MWR filter and the stock paper filter with the stock airbox and a slip-on exhaust. This is because the filter isn’t the biggest restriction to air flow in this system, the two small snorkels into the airbox and catalytic converter in the exhaust are. Not to say that paper filters are awesome, because they do break down faster and aftermarket filters typically are more reliable over time and can be cleaned and reused, rather than replaced as they get dirty. But for performance with an otherwise stock bike, your money can be better spent elseware.

Now look what happens when you compare the stock paper filter to the MWR race filter on a bike with a full exhaust and our Ninja400R velocity stacks in a modified airbox with the snorkels removed and additional holes cut to increase to increase air flow into the airbox:

You can see that the the bike starts to breathe a little better where torque is the highest and it’s requiring the most air. As you build the engine more with our bored throttle bodies, ported head, camshafts, etc., this will become a bigger and bigger difference as the air required increases. This test was also done with the aRacer RC2 race ECU installed. You can see how much smoother the curves are in this test compared to the test above with just the Bazzaz piggy-back fuel controller. Pretty cool stuff.

dB Killer Insert or No dB Killer Insert?

Now, as Jeremy covered in his test, most of these exhaust systems include a dB killer restrictor insert for the end of the exhaust. And most of them actually make more power when this restrictor baffle is installed in the pipe. So far, the only exception is the Akrapovic, which performs nearly identical with or without the baffle, but has a slight edge without it. Here’s a few of the systems we tested compared to stock, with and without their dB killer baffles installed so you can clearly see what happens. In each case, the fuel tune was corrected with and without the baffle installed for a fair comparison:

So what’s the best exhaust for the Ninja 400?

One more thing to do before getting to the dyno results, we need to weigh each system to see if any of them are significantly lighter or heavier than the others. And I’m sorry, I forgot to weigh the Hindle and Yoshimura full systems. The Hindle is one of the lightest weight systems, advertised at only 5 lbs (probably 5.5-6 lbs with hardware and hanger bracket). The Yoshimura doesn’t list an advertised weight, but I remember it being a little on the heavier side compared to the others.

Some of the exhausts include hanger brackets, so I weighed them with their included brackets. For the Akrapovic and Graves systems, I weighed them with the stock bracket as well as the M4 bracket, which is the strongest and lightest hanger bracket available:

So there isn’t a huge difference in weights except for the Akrapovic with the homologated (CA legal) titanium muffler, which weighs an extra pound, and the Akrapovic with carbon muffler, which is about a pound less. All of the rest save around 5 lbs from the full stock system, which is great. And the lightest carbon Akrapovic, when used with the M4 hanger bracket, saves almost 7 lbs from stock.

So let’s get to it already!!! Here’s the comparison of all the exhaust systems I have tested on my bike with the stock motor, stock airbox, MWR air filter, and tuned with a Bazzaz Z-Fi for equal comparison:

As you can see, the Akrapovic and Spark systems definitely have the edge over the rest of the pack. Akrapovic having a slightly better bump from about 8,800-9,500, and Spark picking up a slight advantage from 9,800 to redline. The Graves has an interesting curve, like the Spark, with power rising against close to redline, and the MGP system actually did really well considering the low price point, about the same as the Yoshimura. The Hindle system is down a little on power in the 8,000-9,500 RPM range, but is also probably the lightest weight system in the test.

If you look closely, you can see that Akrapovic also has considerably better performance down low under 6600, so it will feel stronger pulling off the bottom from a complete stop. Here’s another pic of just the Akrapovic and Spark so you can see the two more clearly. Akrapovic performing better below 6,700, Spark performing better above 10,500, and both pretty even on average between 6,700-10,500:

The two systems are both very good. I would probably choose the Akrapovic for best performance on the street because of the extra low end and bump from 8,800-9,500, plus the carbon pipe is lighter and looks awesome. I would also recommend the Akrapovic for MotoAmerica Junior cup spec bikes where revs are limited by the reduced redline. Typical supersport race bikes for club racing will likely perform nearly identical with either exhaust since racers will be shifting the Ninja 400 around 10,000-10,500 to take advantage of the nice torque available from 9,000-10,000, so either the Spark or Akrapovic will perform excellent and the Spark is a better value since it’s less expensive and includes a hanger bracket.

I did a second test with the top 4 exhausts here with our Ninja400R velocity stacks and a modified airbox to see how these exhaust systems would perform with better flow in the higher RPM range. Based on the first test, I expected the Spark would do well since it performed the best at the higher RPM range with the stock airbox, but I don’t like to guess.

So here’s the Akrapovic, Spark, Graves, and M4 systems with our Ninja400R velocity stacks installed and airbox modified for more air flow. This was an interesting test. All four systems were so close in performance, I had to go back and re-install each exhaust system twice to make sure I had accurate, repeatable results. I wanted to make sure I gave a fair representation of the 4 systems since they were so close and the variation between each run with the same system was often as big as the variation between different exhausts. This graph is not necessarily the highest peak number, but shows the best, smoothest, average representation of all four systems from all of the pulls done with each to show how they really performed overall against each other:

The Akrapovic system consistently made a tiny bit more power in the 8,800-9,500 range and the Graves consistently made a tiny bit more power across the top of the power band above 9,500. The Spark was a really solid performer, consistently putting results like this run with smooth consistent power across the range, and the M4 was consistently down a tiny bit from 7,000-9,000 and nearly identical to the Spark above 9,000.

So which is best? That’s up to you! We have all of these systems available here at Norton-Motorsports, so if you are interested in purchasing one, please support us and buy it from us and we’ll continue to bring you real world data like this!

Thanks for reading! That’s just the beginning, look for more articles coming soon as we keep installing more electronics and superbike parts and really start making some power!