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Discussion Starter · #1 ·
This dymo chart, from the Norton website, shows what happens to the air fuel ratio (AFR) curve when a full Akrapovic exhaust (which replaces the OEM header and muffler, and removes the CAT) is installed:

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As you can see, the Norton notes on the graph says that "With the Akrapovic full system and no tune, the entire power band is above 13.5 AFR, that's bad".

WHY is that "bad"?

The implication is that it is bad because any AFR above 13.5 is "bad", but that is not so.

Yes, it is true that an AFR in the range of 13.5 is viewed by many professional tuners as perhaps "optimal", but any AFR between about 13.0 and 14.7 is considered pretty good, and of no danger to the engine. If you examine this graph carefully, you will see that the AFR with the Akrapovic system never gets above 13.8 even right at the 12,000 rpm rev limit. In fact, even at the rev limit, the AFR doesn't exceed 14.7, which is the theoretical "perfect" AFR (the so-called stoichiometric point) where the amount of air and the amount of fuel are in perfect balance.

Rather than being "bad", I would argue that what this AFR curve actually shows is that:

- The Kawasaki Ninja 400 / Z400 OEM tune is REMARKABLY ideal in its ability to tolerate exhaust system changes withOUT requiring an aftermarket ECU tune. In fact, I have never before seen a motorcycle OEM ECU that is better in its tolerance for an aftermarket exhaust

and

- The OEM exhaust, including especially its CAT, is SO restrictive that instead of an aftermarket system causing the engine to run "lean", it actually "uncorks" the overall exhaust airflow enough to actually make the engine run COOLER, as evidenced by the lower temperature gage reading (3 bars versus 4) that me, and other owners with full exhaust systems, are seeing. In fact, the OEM exhaust system is SO restrictive that even the large 6% peak power increase that this Akrapovic system (and others, including the Delkevic system that I and others on the forum have installed) are delivering, is staying within acceptable AFR limits AND is HELPING the engine stay COOLER than OEM while doing so, DESPITE making more power.

I know that others on the forum have tried to claim that owners who do not buy a $300 tune are endangering their engines, but there is nothing dangerous about a 13.8 PEAK AFR in a STREET motorcycle that is not running at 8 or 10 thousand rpm constantly.

Sure, an actual ECU tune can OPTIMIZE the AFR, and can also make other desirable changes (e.g. reduce closed throttle deceleration for those who WANT that). But, it is not "essential" for the safety or durability of your engine.

I have often purchased aftermarket ECU tunes for many of my project motorcycles, but only if they are really needed or add enough advantages to make them worth the cost. When I had any motorcycle where I made enough exhaust or intake mods to lean the AFR a bit too much, I spent the money on the tune because I wanted the enhanced power, throttle response, cooler running, specific features, or longterm reliability that a tune could add IN THOSE CIRCUMSTANCES. But I see no compelling need here - unless you are a racer. I view this specific OEM ECU tune as remarkably good and flexible as it comes from the factory! I think it is very hard to argue that an OEM tune that can accept mods that yield 6% more power without any problems, and that actually cools the engine better with an aftermarket exhaust, can be called "bad".

I hate to be a cynic, but perhaps the loudest and most persistent calls for "a proper ECU tune" might be coming from those who make money on selling such tunes, and for whom the racer market is not big enough. Those folks hurt their credibility in making such claims.

Jim G
 

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It’s only bad in the sense that’s it won’t perform optimally. The 400 makes its most power and runs its best at between 12.8 and 13.2.

I don’t see on what you posted where he says it’s unsafe. But you’re tight on that point. No afr on that plot should be considered “unsafe”.
 

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It’s only bad in the sense that’s it won’t perform optimally. The 400 makes its most power and runs its best at between 12.8 and 13.2.

I don’t see on what you posted where he says it’s unsafe. But you’re tight on that point. No afr on that plot should be considered “unsafe”.
Depends on how the bike is ridden. If it's a typical commuter street bike, then it's probably gonna be fine. But one that spends most its life above 9000 rpm, it's unsafe because it'll overheat. I keep mine around 12.7-12.8 Higher than that and it'll run too hot and overheat. These bikes already run really hot compared to 600s or 1000s as it is.
 

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Norton's tune is the cat's tiddies. So smooth and powerful. Rich is gud.
 

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Discussion Starter · #5 ·
Depends on how the bike is ridden. If it's a typical commuter street bike, then it's probably gonna be fine. But one that spends most its life above 9000 rpm, it's unsafe because it'll overheat. I keep mine around 12.7-12.8 Higher than that and it'll run too hot and overheat. These bikes already run really hot compared to 600s or 1000s as it is.
sbk1198: You really run a 1.27 - 12.8 AFR on a naturally aspirated engine? Back in 2005, before vehicle ECU tunes were far less sophisticated than today, I ran that ballpark of ratio on a supercharged 5 liter Chevy engine that produced 575 crank hp. What causes the 400 to run so hot in racetrack mode to require THAT rich an AFR? Is it simply the sustained high rpm, or is the radiator too small, or ??

Jim G
 

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Discussion Starter · #6 ·
Norton's tune is the cat's tiddies. So smooth and powerful. Rich is gud.
HOW rich does Norton run that tune? What AFR does his tune produce on a dyno run?

I'm asking because I didn't see a dyno chart on his websote last time I looked that showed what his "optimized" AFR was? Did I simply miss it?

Jim G
 

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sbk1198: You really run a 1.27 - 12.8 AFR on a naturally aspirated engine? Back in 2005, before vehicle ECU tunes were far less sophisticated than today, I ran that ballpark of ratio on a supercharged 5 liter Chevy engine that produced 575 crank hp. What causes the 400 to run so hot in racetrack mode to require THAT rich an AFR? Is it simply the sustained high rpm, or is the radiator too small, or ??

Jim G
Yeah, most people that have flashed ECU's on 400s do. 12.8 is about the sweet spot for most tuners I've talked to for this bike. Not really sure why the 400 runs hotter than other bikes I've used. Maybe because of the radiator? Even normal riding on a hot day, it's common to see 4 bars on your temp gage. I don't remember what the low end is for 4 bars, I think somewhere around 90 degrees C, but on the high end it's 102. 5 bars starts at 103 degrees and goes to 112 or 113 if I remember correctly at which point you get 6 bars and the red light turns on. I have a dash that shows the actual temp in degrees C and often times I see it between 100 and 110. Meanwhile my ZX6R and any other bike I've in the past with an actual temp gage runs around 77-90 degrees with the same type of riding and ambient conditions.
 

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Discussion Starter · #8 ·
I just found a graph that I did not see last time on the Norton websote. It shows the Akrapovic full system with OEM and then Bazzaz tune. It too is very interesting:

19671


The OEM tune is just the same as in the first dyno chart I showed in this thread, peaking at 13.8 around the rev limit. The Bazazz tune peaks at 12.9 to 13.0. However, the Bazzaz tune goes as "lean" (AFR = 13.8) at midrange RPM (see the purple Bazzaz line in the rpm range around 6000 to 8000) as the OEM tune does at high rpm!

This tune might be "better" for racers running at high rpm most of the time, but since most STREET riders spend WAY more of their time in the 6000 to 8000 rpm range, I would not view the Bazzaz tune shown here as better for a street rider.

Does Norton offer a tune that is more favorable in the midrange as well as in the upper rpm range?

Jim G
 

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With my full exhaust, musarri header and coffman slip-on, the AFR was over 18:1 before tune. So I had absolutely no choice and would have definitely melted a piston if I hadn't gotten a proper tune. That is why I advocate for getting a proper tune.
19672
 

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Discussion Starter · #10 ·
Yeah, most people that have flashed ECU's on 400s do. 12.8 is about the sweet spot for most tuners I've talked to for this bike. Not really sure why the 400 runs hotter than other bikes I've used. Maybe because of the radiator? Even normal riding on a hot day, it's common to see 4 bars on your temp gage. I don't remember what the low end is for 4 bars, I think somewhere around 90 degrees C, but on the high end it's 102. 5 bars starts at 103 degrees and goes to 112 or 113 if I remember correctly at which point you get 6 bars and the red light turns on. I have a dash that shows the actual temp in degrees C and often times I see it between 100 and 110. Meanwhile my ZX6R and any other bike I've in the past with an actual temp gage runs around 77-90 degrees with the same type of riding and ambient conditions.
Yes, I USED to see 4 bars normally in my typical street riding. But after I installed the full Delkevic exhaust, it changed to 3 bars most of the time. Consistently.

I don't think that the Delkevik exhaust does anything "trick". All full exhausts eliminate the CAT and all generally have low restriction mufflers. And yet the Delkevic makes the gage run at 3 bars versus 4 , whereas at least some other systems do not let the engien run cooler. I think the Delkevic system simply has very low restriction HEADERS. If you look at the shape of the Delkevic header pipes, they are fairly unique. I think maybe the eliminate a "hot spot" in the headers and collector. I noticed when I examined my OEM headers, there is evidence of very high heat right where the headers join at the collector. Perhaps this is a problem with the OEM system?

Here's what the Delkevik headers look like:

19673


See how far forward towards the front wheel the headers come? And how straight a shot they are coming out of the engine and then how gently they curve back towards the collector?

Jim G
 

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Discussion Starter · #11 ·
With my full exhaust, musarri header and coffman slip-on, the AFR was over 18:1 before tune. So I had absolutely no choice and would have definitely melted a piston if I hadn't gotten a proper tune. That is why I advocate for getting a proper tune. View attachment 19672
I think I might blame that exhaust system versus blaming the OEM tune. Your dyno operator is claiming an almost 14% power increase. If that's legit, that suggests that a lot more than simply exhaust was done. I've never seen an exhaust alone give that kind of improvement on a Japanese motorcycle (Harley, yes I have for good technical reasons). No OEM tune that I know of could handle THAT much of a change without running into problems. What else was done beyond the exhaust?

I'm guessing that that exhaust system is also pretty loud. Am I right?

I notice that your AFR after tuning is in the low 13s. What temperature range (number of bars) are you seeing on your temperature gage? And, are you primarily a street rider or racer?

Jim G
 

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Yes, I USED to see 4 bars normally in my typical street riding. But after I installed the full Delkevic exhaust, it changed to 3 bars most of the time. Consistently.

I don't think that the Delkevik exhaust does anything "trick". All full exhausts eliminate the CAT and all generally have low restriction mufflers. And yet the Delkevic makes the gage run at 3 bars versus 4 , whereas at least some other systems do not let the engien run cooler. I think the Delkevic system simply has very low restriction HEADERS. If you look at the shape of the Delkevic header pipes, they are fairly unique. I think maybe the eliminate a "hot spot" in the headers and collector. I noticed when I examined my OEM headers, there is evidence of very high heat right where the headers join at the collector. Perhaps this is a problem with the OEM system?

Here's what the Delkevik headers look like:

View attachment 19673

See how far forward towards the front wheel the headers come? And how straight a shot they are coming out of the engine and then how gently they curve back towards the collector?

Jim G
Is there no bung hole in the headers on that exhaust?? I don't see one in the picture unless it's on the other side. Usually they're on the right side though. If it doesn't, then you can even put an O2 sensor on it to measure the AFR on a dyno.
 

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Discussion Starter · #13 ·
Is there no bung hole in the headers on that exhaust?? I don't see one in the picture unless it's on the other side. Usually they're on the right side though. If it doesn't, then you can even put an O2 sensor on it to measure the AFR on a dyno.
yes, there IS a bung hole on the Delkevic, and I do have the O2 sensor installed. You just can't see it in that photo. Here is a photo from Delkevic that shows the bung hole - it is just barely in font of the engine crankcase and below it:

19674


As for getting an actual AFR on a dyno: I can't. There simply is no dyno anywhere on Vancouver Island, and the closest ones are in The U,.S. (Washington State). The logistics of making a trip to even the nearest Dynojet dyno make it totally cost prohibitive and impractical for me (and legally impossible too during COVID restrictions). This is one serious DISadvanatge of living on Vancouver Island. In every other way, life here is pretty good: fantastic mountain scenery, ocean seashore on BOTH the west and east coasts, winding and hilly roads because of the mountainous topography, weather moederate enought to enable all-year riding, etc. :)

But you can't use a normal O2 sensor to measure AFR accurately anyway. A normal ("Narrowband") sensor is too much like a "lightswitch" - the output voltage varies from approximately 0.1 to 1.0 volt, and the transition through the 14.7 AFR point is VERY dynamic and steep. That's why a proper dyno run instead involves inserting a flexible sniffer rod into the exhaust. It's also crucial to disable the O2 sensor when doing a dyno tune or doing a dyno run just to get the actual AFR, as otherwise the O2 sensor's feedback to the ECU will undo much of the tuning you are doing. That's why most tunes disable the O2 sensor feedback to the engine.

Jim G
 

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HOW rich does Norton run that tune? What AFR does his tune produce on a dyno run?

I'm asking because I didn't see a dyno chart on his websote last time I looked that showed what his "optimized" AFR was? Did I simply miss it?

Jim G
One of these days, I'll get the bike on a dyno. All I can tell is it's definitely rich. Smells rich and looks rich judging by the spark plug colour and piston crown carbon buildup. I really want to get a digital temperature gauge, just can't find any. So going by the cluster temperature bars:
Idle: 4 bars
street cruising: 3 bars
top speeds/highway: 2 bars

Never seen 5 or 6 bars with the tune.
 
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Hey guys,
Somewhat related to this, I was considering a boosterplug to fix the lean issues at low RPM, especially in conjunction with a slip-on which may lean me out even more.
Boosterplug advertises a 6% reduction in AFR, which I've illustrated in the chart below in purple line.. the AFR allegedly would sit between 12.5-13.0 through most of the RPM range, with as low as 12.2AFR at around 7k rpm. Would this create more issues than it would fix? According to their literature, the boosterplug will only modify AFR values low in the RPM range during low speed, and during acceleration/deceleration (basically only when the bike is in open loop mode). This is how they remedy the choppy lean throttle at low RPM, while allowing a bike to run lean/economically during cruise speeds using the o2 sensor in closed loop mode. For someone only interested in preventing lean conditions and limiting mods to a slip on.. is a boosterplug a good idea to richen the AFR?
boostplug tune.jpg
 

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yes, there IS a bung hole on the Delkevic, and I do have the O2 sensor installed. You just can't see it in that photo. Here is a photo from Delkevic that shows the bung hole - it is just barely in font of the engine crankcase and below it:
Ah I see. That's good.

But you can't use a normal O2 sensor to measure AFR accurately anyway. A normal ("Narrowband") sensor is too much like a "lightswitch" - the output voltage varies from approximately 0.1 to 1.0 volt, and the transition through the 14.7 AFR point is VERY dynamic and steep. That's why a proper dyno run instead involves inserting a flexible sniffer rod into the exhaust. It's also crucial to disable the O2 sensor when doing a dyno tune or doing a dyno run just to get the actual AFR, as otherwise the O2 sensor's feedback to the ECU will undo much of the tuning you are doing. That's why most tunes disable the O2 sensor feedback to the engine.

Jim G
You can use a wideband O2 sensor. That's how the dyno I use is setup. We don't have a "sniffer". The wideband sensors works great. My bike has one permanently on it which works with the aRacer AF1 autotune I use. The advantage of using wideband sensors is that you can also tune individual cylinders if you weld a bung hole on each header and put a sensor in each one. I plan on doing that with my 400 soon because there is a Spark exhaust that's already setup for that so I just need to swap out the headers and put it on the dyno to see the difference in AFR between the two cylinders.

The signal from the wideband O2 sensor gets disabled in the sense that you unplug it from the bike and plug it into the dyno (so you can read the AFR on the screen obviously), hence it's not on a loop anymore and isn't undoing what you're tuning.
 

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Discussion Starter · #17 ·
Ah I see. That's good.



You can use a wideband O2 sensor. That's how the dyno I use is setup. We don't have a "sniffer". The wideband sensors works great. My bike has one permanently on it which works with the aRacer AF1 autotune I use. The advantage of using wideband sensors is that you can also tune individual cylinders if you weld a bung hole on each header and put a sensor in each one. I plan on doing that with my 400 soon because there is a Spark exhaust that's already setup for that so I just need to swap out the headers and put it on the dyno to see the difference in AFR between the two cylinders.

The signal from the wideband O2 sensor gets disabled in the sense that you unplug it from the bike and plug it into the dyno (so you can read the AFR on the screen obviously), hence it's not on a loop anymore and isn't undoing what you're tuning.
Yes, wideband sensors are nice. Someday when they, and the ECU systems needed to use them properly, are lower in cost, we might see them, and the constant optimal tuning they can cause, on production vehicles. But, with The World turning to electric vehicles so strongly (with many countries forbidding the sale of internal combustion vehicles by 1935), we may simply find ourselves riding electric motorcycles instead before any more money is spent on trying to optimize IC engines.

The case for electric cars is compelling. Our family car used to be a Kia Soul Turbo, whose 1.6L turbocharged engine was pretty much state of the IC engine art (205 hp from 1.6L and really impressive low end torque). But 16 months ago we bought a Kia Soul EV (true all-electric, NOT a hybrid) to replace it. We did it as a cost saving measure!

My wife's healthcare job requires her to run a route of approximately 125 - 135 kilometers per daily shift. We put on a total of 3300 km = 2050 miles per month.

At Canadian gas prices, our gasoline bill used to be $425 per month. The Kia EV charger reports its charging power consumption every day to us via Internet, separated from the overall electricity bill. Our electricity bill to charge the car for the 2050 miles per month is $65 per month. There's a HUGE difference between $425 per month and $65 per month.

And, EV vehicles have none of the parts or systems that commonly need maintenance and/or regular replacement , like engine oil changes, coolant changes, automatic transmissions, timing belts, alternators, brake pads (because you hardly use brakes on an EV because deceleration uses the decelerating motor to feed the battery instead as a generator), etc. We have had ZERO maintenance cost in the 16 months so far.

We are in the twilight of the internal combustion engine for passenger vehicles. Enjoy it while it lasts. :)

Jim G
 

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Well this thread took an interesting turn towards electric vehicles all of a sudden lol But yeah I'm afraid you're right. We are heading that way. I'm not opposed to having an EV as a daily driver. But I'm hoping I can still enjoy gas motorcycles for many more years to come. There is no electric motorcycle right now on the market that interests me even a bit. Not saying I will never get one, but technology will need to improve a lot more and someone will need to make something cooler before I'll entertain the idea of getting one. Cars though...I'd buy a Tesla tomorrow if I had the money.
 

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Discussion Starter · #19 ·
. . .
Cars though...I'd buy a Tesla tomorrow if I had the money.
Wev took a loan to buy the EV Kia. BUT, the monthly gasoline cost saving = $425 gas - $65 electricity = $360 pays most of the monthly payment on the EV. Plus, we started again with a brand new car with zero kilometers on it. :)

We are fortunate to not need a major public infrastructure of charging stations for our work and personal usage though. We only use about 1/4 of the EV's battery range each workshift, and simply plug it in for the night in our garage.

But people who want or need to ravel far from home base need to know there are charging stations whenver and wherever you need one. Our province in Canada has a public EV infrastructure (one of our small-plane commuter airlines is even going electric!), but most of the other provinces do not, and the only place I am aware of The US that has any EV infrastructure is Calirfornia. So, you're good loving IC engines at least for the next few years!

Jim G
 

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I think I might blame that exhaust system versus blaming the OEM tune. Your dyno operator is claiming an almost 14% power increase. If that's legit, that suggests that a lot more than simply exhaust was done. I've never seen an exhaust alone give that kind of improvement on a Japanese motorcycle (Harley, yes I have for good technical reasons). No OEM tune that I know of could handle THAT much of a change without running into problems. What else was done beyond the exhaust?

I'm guessing that that exhaust system is also pretty loud. Am I right?

I notice that your AFR after tuning is in the low 13s. What temperature range (number of bars) are you seeing on your temperature gage? And, are you primarily a street rider or racer?

Jim G
MWR race air filter and exhaust, Running FTECU. It is a race bike, sits at 4 bars unless ambient is over 105F and then it'll go to 5 at race pace. Usually measures around 104Db on the meter.
 
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