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Engine is "sputtery" at lower rpms


ChickenStrip
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My new 2015 FJ09 is great when I roll on, but sometimes when I'm puttering along at lower rpms, the engine 'putters' or sputters when it shouldn't - making it jerky while I'm holding throttle steady. I know I'm going to get the ECU flashed by @2wheeldynoworks in the next week or so. I was thinking about waiting until I got a full exhaust system, but I've seen where some peeps say to get it flashed before dropping bucks for a full exhaust system, because getting the tuning done opens up the FJ's potential (especially the US, choked up version of it). I know a lot of y'all know these bikes quite well and have come across this issue. Will getting the ECU flashed (not at a dealership, because they don't get rid of the 115mph cap)  smooth out the engine and get it performing closer to stock optimum? Thanks in advance for the help!
 
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The general consensus is that an ECU flash is one of the better mods for the money available for the FJ.
 
Having said that, my FJ is not flashed, and although the fueling/throttle is touchy and jumpy at low RPMs I have never experienced anything I would refer to as sputtering. When I think sputtering, I think misfire or something along those lines. You might want to get that checked out at the dealer before flashing to make sure everything is good to go first.
 
 

'15 FJ-09 w/ lots of extras...

Fayetteville, GA, USA

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I've got an appointment at the dealership first thing Thursday morning. As I held the throttle steady at around 3k - 4k rpms the bike would jerk a little, similar to how it feels when running out of gas, and then suddenly had gas. I will definitely have the dealership check this out.
 
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Mine is flashed for the Arrow by 2wheeldynoworks, and is still slowly exhibiting this hesitation/surging as I drive it more. I never did the throttle body sync, maybe I'll do that this fall during off season maintenance.
'15 FJ-09 with an aftermarket parts addiction
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I have 3,000 miles on my 2015 FJ 09, 2WDW ECU reflash is the only engine mod. Engine runs so good at all rpms, including low rpm, that I have not attempted to synch the throttle plates. I have installed G2 throttle tamer which improves roll on from idle. So add my name to the list that this engine can be silky smooth.
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From what I understand, and I'm not an expert on this by any means...
 
The emissions controls on this bike, and all CP3 engines, are trying to get 14.7:1 air fuel ratio while at part throttle. This uses the 02 sensor in the exhaust to "monitor" how lean or rich the bike is fueled by the ECU. This version of the 02 sensor is like a switch, or "narrowband" style, and only tells the ECU when it's rich or lean. Not the ratio.
 
Thus, the ECU "flips" from rich to lean constantly, and this signal is then returned back to the ECU by the 02 sensor. Rich/lean/rich/lean/rich/lean all the time you putt putt around at small throttle amounts.
 
At WOT, or higher throttle settings, it defaults to a performance fuel map, and timing, that provides for richer than 14.7:1 ratios, and that make more power, and make the engine run smoother.
 
Low RPM, or off throttle fuel cut is another issue. It is to improve emissions, so the fuel is cut and the engine nearly dies when you are off throttle, and slowing down, which you do around slow speed parking lots for example.. Making the bike feel very unstable and eratic.
 
A flash that turns off the 02 sensor can fix this. But you have to create a fuel map that will run the bike, since the stock one has a map, but it has the 02 sensor, and others, trim the fuel to the conditions of the day.
 
Air intake temp. Pressure sensors and throttle position are all parameters the ECU looks at before it decides how long to pulse the injector open every time it fires. And when to fire the spark plug. SO the timing is constantly up for change too.
 
This is a good thing for the most part. Our bikes are smooth, and can run from sea level to high altitude without any changes on the riders part. It deals with hot days or cold ones. Changes in barometric pressure as well. Even grades of fuel are accommodated without any issue from the rider.
 
The only way to have or keep the 02 sensor in play, and have all that ability helping the bike run it's best is to fool the ECU into thinking it sees 14.7:1 when the bike is slightly richer. Say 13.2:1 for example. (Best for power and mileage.)
 
How can it be better for mileage? Well, at "stoichiometric or 14.7:1 it's low on power, so you need more throttle to maintain the same power, and more fuel in reality, since you are asking for more throttle.
 
While at slightly richer, and more powerful ratio's, you need less throttle. But still go as fast as you would with more. And the fuel economy also is better when you want/need more power, such as off the line, or passing a vehicle, or just enjoying the bike's throttle/power. You always use less throttle for the same power, so you in reality use less fuel even at the slightly higher/richer fuel ratio.
 
I have a "KEVTEX" unit that plugs into the stock 02 wires, and "fools" the stock, and flashed ECU's into thinking that 13.2:1 is really 14.7:1.
 
This makes the bike smooth at all speeds, from idle to redline. But also makes any part throttle use such as just tooling along in traffic, 25mph in 4th gear very very smooth. No surges. Nothing like that, and power is much better when you roll on to go, it goes. No hesitation like it does stock.
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From what I understand, and I'm not an expert on this by any means...  
The emissions controls on this bike, and all CP3 engines, are trying to get 14.7:1 air fuel ratio while at part throttle. This uses the 02 sensor in the exhaust to "monitor" how lean or rich the bike is fueled by the ECU. This version of the 02 sensor is like a switch, or "narrowband" style, and only tells the ECU when it's rich or lean. Not the ratio.
 
Thus, the ECU "flips" from rich to lean constantly, and this signal is then returned back to the ECU by the 02 sensor. Rich/lean/rich/lean/rich/lean all the time you putt putt around at small throttle amounts.
 
 
 
Low RPM, or off throttle fuel cut is another issue. It is to improve emissions, so the fuel is cut and the engine nearly dies when you are off throttle, and slowing down, which you do around slow speed parking lots for example.. Making the bike feel very unstable and eratic.
 
A flash that turns off the 02 sensor can fix this. But you have to create a fuel map that will run the bike, since the stock one has a map, but it has the 02 sensor, and others, trim the fuel to the conditions of the day.
 
Air intake temp. Pressure sensors and throttle position are all parameters the ECU looks at before it decides how long to pulse the injector open every time it fires. And when to fire the spark plug. SO the timing is constantly up for change too.
 
This is a good thing for the most part. Our bikes are smooth, and can run from sea level to high altitude without any changes on the riders part. It deals with hot days or cold ones. Changes in barometric pressure as well. Even grades of fuel are accommodated without any issue from the rider.
 
The only way to have or keep the 02 sensor in play, and have all that ability helping the bike run it's best is to fool the ECU into thinking it sees 14.7:1 when the bike is slightly richer. Say 13.2:1 for example. (Best for power and mileage.)
 
How can it be better for mileage? Well, at "stoichiometric or 14.7:1 it's low on power, so you need more throttle to maintain the same power, and more fuel in reality, since you are asking for more throttle.

 
Ok I've edited some of what you said with the intent of clearing up some of what you have typed out, but I'm on a mobile and it would be too complicated to insert my comments into your post piece by piece. So here goes...
 
A lot of what you said is correct.
But it's easier to think of in terms of "closed loop" and "open loop". O2 feedback is only looked at by the ECM in closed loop mode.
 
This bike is closed loop at idle after the coolant is over 140 degrees (IIRC) and at steady throttle cruise and part throttle acceleration. What is part throttle accel? It will vary between close loop and open loop depending on how fast the throttle is opened.
 
This can also vary by what gear you select.
 
Based on my data from the dyno, Yamahas are usually between 14.2-14.0 (which is richer than 14.7) - in closed loop mode. Harley D bikes will run between 15.0-14.6 in closed loop by comparison. This will vary from bike to bike and manufacturer...
 
Saying the ECM "flips from lean to rich" is sort of true but it happens an un-countable number of times PER SECOND. The ECM is constantly adjusting (mostly) fuel injector duration to achieve what it has been programmed to achieve - which is different in closed loop vs open loop. Yes it also adjusts timing and (on our bikes) the throttle plate position.
 
 
The ECM has many different maps, and will use whichever one it is programmed to -based on whether it is supposed to be in closed loop or open loop.
 
Losing the o2 sensor or the feedback from the sensor, simply makes the ECM consult a different set of tables.
 
The Optimizer which is included with the PC V fools the ECM when it is in closed loop mode. In the case of the FJ, dyno jet says 13.6-13.7 based on the info in the box of the one I just installed on my bike.
 
Hope this makes sense. As a caveat, I am not a programmer nor do I have access to the code or software (flash tune). I have been trained in how it works, however.
 
Btw, the only reason for all this is performance AND cat efficiency.
 
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That's the guy, Kevtex. He's in AU, and does nice work. It works great. And he has much more details than I wrote up, but pretty much the same thing.
 
I was off slightly in my AF numbers, but not by much, and the idea is richer about 13 and change v/s 14.7 at Lambda for emissions makes more power, runs smoother, and you can feel the smoother engine and bike.
 
A side benefit to the power is better fuel economy too.
 
Too bad I can't do this to my car, or have not found someone who's got a simple fix like this for my car.. Wonder if Kevtex could build one? That's not a bad idea. Slightly richer operation on your car, smoother running engine/car, and slightly more power and better fuel economy. ;)
 
On my 2006 FZ1, I had Ivan's pressure sensor dongle.. that pretty much did the same thing, richened up the closed loop fuel ratio, and smoothed out the fuel cut effect on that bike. And I cut the secondary throttles in half for more flow at all times, opened up the air box, and put on an Akrapovic slip on.. It was way more powerful than stock setup like that, and while everyone said I should have the ECU fuel map changed, it was running rich enough at that mod level, that raw gas was spit out, would fly around, and all my riding clothes smelled of fuel.
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"That's the guy, Kevtex. He's in AU, and does nice work. It works great. And he has much more details than I wrote up, but pretty much the same thing. 
A side benefit to the power is better fuel economy too."
 
Kev's kit's function does richen the AFR on closed-loop but it is the reduction in the variation between the AFR on Closed-Loop and Open-Loop that cause the hunting back and forth that is commonly referred to as "surging" and this thread titles "sputtering".  I just installed Kev's O2 Controller yesterday and unexpectedly   found time for a 2 hour test ride today.  The surging on constant throttle, particularly in the lower gears, is very much improved if not altogether eliminated; although temperatures were cooler today (under 80 degrees F).  More test rides are needed but my fuel efficiency was down a bit; although I was enjoying the new found smoothness and consistency.
 
http://www.ebay.com/itm/142053155148?rmvSB=true
 
http://fj-09.org/thread/3953/fitting-kev-mod-o2-controller
 
 
 
 
 
 
 
 
 
 

 
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  • 1 year later...
Ok. I wondered if syncing the throttle bodies would help/alleviate this. Actually, my first thought was perhaps the throttle bodies being wonky. I know after I had the throttle bodies synced on my FJR1300, it was indeed smooth as silk.
 
Old thread but curious did TB sync or ECU flash helped your FJ? I have the exact same issue, seems to have developed slowly. I'm at 12k miles and tried tightening then replacing chain, but my rpms and travel are still jerky in the 2-3k range at constant speed. 3rd gear around 22 mph is the worst.
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