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EFIE Experiences

41K views 63 replies 10 participants last post by  MrEvilpirate  
#1 ·
I'm looking for them. Found a couple posts here but no real information.

What I'm wondering is has anyone installed this and wide banded the bike before and after.

Can this compensate for intake and a pipe? The price is right at 30 bucks. I understand you need to use a wideband o2 to tune it. I have no problem with that for the cost savings.

Also I hear people talking about wiring it backwards. Is it not adjustable in both directions, or can it only richen or only lean depending on the installation? Can you adjust at different points or is it an overall AFR shift (standard map universally richened or leaned, depending on how it is wired).

Someone must be using one of these things.... Thanks.

Man, bike has been in dealer for tranny/clutch issues for a week, I can't stop thinking about tuning it lol.
 
#50 ·
Here it is long overdue, my findings after widebanding the Z and messing around with O2 signal voltage.

First some corrections to my first wideband readings post as I have spent a lot more time watching the gauge and know more about how the bike runs.
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Stock the bike cold idles at 13 and warms up to 14.6 +/- 0.3. So as the ECU adjusts the AFR based on O2 readings it oscillates between 14.3 to 14.9. One thing I noticed is after you blip the throttle or get off the gas AFR at idle drops to about 13.8, then slowly climbs up to 14.6 over about 15 seconds. I think they do this to keep the mix rich in case you start again quickly... richer mix can make up for no spark advance.

Cracked Throttle cruising is same as idle (both closed loop) around 14.6. "Dig in" a bit, maybe 3/4 throttle it drops to 13.3ish. Any revs, regardless of throttle position, over around 7k and AFR drops to 13.3ish. WOT gives you AFR of 12. So the bike runs rich stock, except at cracked cruising, where it can get a touch lean and in my experience cause some surging at mid RPMs.
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Enter EFIE. I ended up with a voltage offset around -0.195 v.

After learning some trims, cold idle is now 12.8. Warm idle does the same raise up over about 15 seconds. But with EFIE correction it is about 13.1 (right after a blip) and settles around 14.2. This eliminates the surging I was complaining about. Cruise/cracked thottle is in closed loop... O2 signal is offset, so AFR for this range is same as idle, about 14.2.

3/4 throttle and over 7k RPMs about 12.9 and WOT is 11.8-12.0. So EFIE's modulated signal caused fuel trims to be learned as richer than without EFIE, this translated into richer open loop settings after the ECU learned the trims. PS all these numbers I'm giving you are after starting and stopping the bike many times (cold starts) and running about 100 miles at each setting.
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With EFIE and Intake:

Cold idle back up to 13... intake leaned EFIE mix from 12.8 back up to 13 cold idle (open loop)

Warm idle (closed loop) the same as just EFIE at 14.2 (with 15 second dip to 13.1 after blipping throttle)... ECU can handle intake and richen mix to get to it's target AFR no problem... remember EFIE is RICHENING the mix, so if ECU can hit target with EFIE, stock ECU can handle intake in closed loop without it as well.

Cruise/cracked throttle is closed loop, so same as just EFIE 14.2.

3/4 throttle or above 7k 12.9 - 13.2. So even though ECU learned trims, when applied ECU does not get stock AFR with intake at this throttle position. But this is safe range. Remember... EFIE is used in this example and is making the ECU learn trims that are richer than would be without it. So even though this is open loop, by using the EFIE in closed loop more extreme fuel trims (richer) have been learned.

WOT 12.2 - 12.5. Again intake is shown to lean the mix.
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EFIE, intake, and pipe

Cold Idle - 13 (note pipe did not lean the mix more than just intake. These parts flow more air the higher the RPM... so at idle they flow a little more than stock, but when ripping hi RPMs they flow a lot more than stock... part of the reason why learned fuel trims can't accurately maintain stock AFRs at higher RPMs or more open throttle positions... because the trims are learned under closed loop conditions, where performance parts perform closer to stock, in terms of how much air they let flow through).

Warm idle - 13.1 (after blip) up to 14.2.
Cracked Thottle/Cruise - 14.2. This proves stock ECU can handle intake and exhaust and provide stock AFR levels during closed loop operation. Again EFIE is used in this example. Without it the ECU wouldn't need to send as much fuel, so stock is the same thing you will get stock AFRs in closed loop.

3/4 Throttle and over 7k rpm- about 13.3. Leaned out a touch more than with just intake. Still safe. Again with EFIE.

WOT - 12.4 - 12.7. So check this out. Honestly I think it pulls harder closer to 13 than 12.
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FINALLY - NO EFIE, STOCK ECU, INTAKE and EXHAUST:

Cold Idle 13.3
Warm Idle (after 15 second rise) and cruise/cracked throttle 14.6
3/4 and above 7k - 13.9
WOT - 13.3
----------------------------------------------------------

Thoughts

For stock bike without fuel controller and adding intake and exhaust, it looks generally safe, with the following caveat:
Richer mixes run cooler. Kawi set this thing to run rich at WOT, partly I believe to control head temps. I don't know enough about AFRs to tell you if it is safe to run this type of motor for long periods of time WOT at an AFR of 13.3. It seems OK. 13.9 at 3/4 seems a touch high though.

EFIE seems like a good cheap add to the bike to get more fuel flowing if you want to run these mods.

Personally I would run it even on a stock bike, especially if the surging at mid RPMs when rolling on from cracked throttle bugs you.

For Kaw'ee and guys running O2 deletes, be advised that the "closed" loop without the O2 tends to run lean. I was seeing numbers over 15. This was on stock bike. I didn't take readings with mods. So at idle or cracked throttle/cruise, without O2, you are lean. It does richen at 3/4 and WOT compared to stock. I suppose that cracked throttle AFR being lean MAY be acceptable because there is minimal load on the engine. When you decelerate the mix leans out to the point where it can't be measured on the gauge... but I personally would not be comfortable. Kaw'ee... I think you mentioned your idle temps went up when you deleted the O2. This is why.

Personally If I were you guys with no O2 I'd just weld the bung on and call it a day.

It's late I couldn't sleep and have been wanting to get this out.. I didn't proof it and it is a wall of text. Hope you can get something from it. Happy to answer any questions to the best of my ability.

Think I'm ready to turn the page on this one and put the wideband away. Now we know.
 
#37 ·
OK boys we have proof of concept.

CEL was out today so I dialed up EFIE to a 0.125 V offset and went for a ride. This was without clearing any trims.

I noticed that cracked throttle cruising AFR dropped and I was seeing 13.7 and 13.8 for the first time. The AFRs swing around, stock is like 14.4 +/- 0.4. With this offset I got to maybe a 14.2 +/- 0.5. There are couple things coming into play here.

First, trims were not reset and the ECU most likely needs more time to re-learn. I only went for maybe a 6 mile ride.

Second, as narrow band O2s get farther away from an AFR of 14.7 accuracy drops of QUICKLY and a smaller change in voltage can correspond to a larger change in AFR. This doesn't worry me too much... AFR on carbs swings much wider than what I was seeing on my test ride today. The average AFR drops, but the "swing" could potentially grow with an aggressive offset.

So I went back to the garage, and with the bike still running, turned up the voltage offset while I watched the idle AFR drop. I got it down to around 13.3 and went for a ride. I needed an offset of 0.360 V to get there. Promptly threw code 33: bad O2 sensor. So I took it a bit too far. The offset must have sent voltage from the O2 out of range.

Rode home dialed the offset back to 0.250 and disconnected the battery. I'll take it out again tomorrow with no trims stored in ECU and see how it runs.

I will say this... even with just the 0.125 V offset... I was hunting around for lean surge on cracked throttle between 5-7 krpm and couldn't find it, so I'm optimistic. Still need to see how open loop is affected.

I have a zoom loop and a K&N filter for DIY intake coming, hoping to have both here by end of day Friday, and weather is looking good this weekend. So if the parts arrive on time the goal by Sunday night is to post up confirmation that stock ECU can handle exhaust and intake, and maybe even some tuning info on the EFIE.

One thing I think that may come into play, is that as we tune EFIE and get away from 14.7 AFR, because of the loss of accuracy, what may work on one bike may not work 100% on another, even with identical mods, due to accuracy tolerances of narrow band O2s. That's pure speculation on my part, but from what I read, and since we're pretty much asking the narrow band to shift lamda and almost act as a wideband, I think some variability between different O2 sensors can be expected.

Side note- apparently having the bike on (not running) with O2 disconnected will throw the O2 heater circuit code. Heater circuit is energized when key is turned on, and it is grounded through the ECU. I read that in some vehicles the ECU can "pulse" the ground to turn on or off the heater circuit. The code gets thrown if resistance (ohms) is out of spec, or if there is a short in the circuit, or if the circuit is open, which is the case when the O2 is disconnected.
 
#48 ·
Ando I had a great post and lost it. So I've taken a couple days and I'll post complete findings soon. Long story short intake and exhaust lean out the mix in open loop. Still fairly safe but bike runs much better using EFIE mod, target voltage for me is 0.195 V but YMMV... EFIE is a good idea. Full results soon...

I have numbers stock, stock and EFIE, intake only, EFIE and intake, EFIE intake and exhaust.
 
#53 ·
TBS- you pretty much got it bud. Run that pipe and don't look back. Bike will be fine.

Next spring I'm going to put my stock airbox back on and try running with just the pipe. But I will personally keep EFIE.

Even in stock configuration, my experience is that EFIE improves the bike's fueling... but my results show you don't need it to keep AFR in safe range.

Keep the shiny side up brah!!! lol
 
#55 ·
Well I just want to say TY for all of your testing and analysis.
Although I did get lost on some of the technical parts back a few pages.

So in the end, some simple intake and exhaust mods, don't require any further fuel controller mods?
Also with some of these simple mods, performance gains are very little?

I get the point that going from 8hp to 10hp is a 25% increase, but in the end it is still JUST 10hp.

I really don't mind the look of the stock exhaust, and spending significant amounts of money
on aftermarket exhaust and intake, doesn't sit well with me.
I see myself with a drill and some different sized bits going the DIY way.:grin2:
 
#2 ·
I've answered some of my own questions.

The system adjusts voltage across the board. You set in mA how much you want to increase/decrease. That change is applied to the entire fuel map. A lot of grom guys run this to compensate for exhaust and intake. I'm going to do it. Need to weld a bung on my stock exhaust for my wide band, will log before and after installing the EFIE. This seems like a good option for guys who want to richen up the stock lean AFR and add a pipe and intake.

https://docs.google.com/document/d/1wX0fOAMqEmYk6jgRK37Qc4apUxoLQw5pchcSt5krOFA/edit


Check out post 88:
https://www.hondagrom.net/forums/13-grom-performance/3113-o2-sensor-grom-piggyback-tuners-9.html
 
#18 ·
My reservation, after a lot of googleing, is that in some vehicles closed loop trim seems to affect the open loop map, but in some vehicles it doesn't. Based on the forum post I linked to it looks like the Grom will adjust open loop fueling to long term closed loop trims. We don't know that the kawi ECU works the same way.

I'm going to swallow my pride and take stock exhaust to the muffler shop and have them weld on a full size bung and spacer so I can use my wideband and take some WOT AFRs, then install install EFIE and try to get general AFR around 13.4. Take the bike for a long ride then check WOT AFRs... if they change we know we're good... and no lean risk as my bike is still pretty much stock.

Kaw'ee I think your plugs look just a touch rich, but way better than mine with stock setup. I'll throw some pics up of mine later.

Greg I hope you are right about how the trims get added to baseline on open loop... will save people a lot of money if this works.
 
#52 ·
I've read through this a couple times and know more now than when I started reading but it's a lot of info for me. The general take away I got was the stock ecu can and will adjust to an aftermarket intake. The stock ecu can and will also adjust to and aftermarket intake and exhaust, but that's asking a lot of it and probably not the best thing to do. The stock ecu with no aftermarket parts is how Kawasaki intended but could be improved with installing EFIE but to really know what the EFIE is doing you have to install a wideband by welding a port onto the exhaust pipe.

I personally would like to put aftermarket exhaust on just for looks and sound. After reading this I feel I could do so without any additional items ie Bazzaz, EFIE, Hoedar ECU.
 
#59 ·
Just a heads up from the grom forum this week.
.
Quote Originally Posted by asume
Note to all EFIE installers.
You'll have to keep adjusting the device depending on how much you ride. The vibrations tend to readjust the device.

Quote Originally Posted by farkas
Good advice.. I noticed this too.
I ended up using velcro tape so that I can take it on and off of the battery tray under the seat for easy adjustments.
 
#5 ·
Subscribed !

I'm Putting on a custom made up-pipe exhaust next week, And only for ground clearance issues, not looking for any performance gains , but do not want to run lean . I Read the links so got a slight feel for what it is but I refuse to hook a laptop up to a motorcycle ..... following....
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Ya, Old School n ain't change'n :mad:
 
#6 · (Edited)
The EFIE came today. Shipping estimate was 6 weeks but it took 6 days.

Here are some pics, it is wrapped up in something that feels like large format electrical tape. It came with a note. When you buy it you get an account. There are portions of their website that you can only view with an account and the note said there are updated instructions there. Haven't checked it out yet, it is 8:22 my time and haven't made dinner yet.

Now I only need a bike to install it in. Welder is supposed to show up tomorrow.

Edit sorry for potato quality not sure what happened there.

https://www.z125owners.com/forum/attachment.php?attachmentid=20015&thumb=1
https://www.z125owners.com/forum/attachment.php?attachmentid=20013&thumb=1
 

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#9 ·
Some info from TOCE Performance who offers to re-flash stock ECUs (my initial email to them in BOLD):

Some confusion here as to closed vs open loop and I did not get all the info I was looking for... I plan to visit and ask some more questions. Info on stock AFR is interesting... 13.0 AFR is what I thought target should be looks like I was pretty close, at least according to these guys.

Still not clear when the bike is in open or closed loop. This is the biggest concern with running EFIE device. If stock ECU reverts to an open loop map at WOT then you are going to be running super lean cruising at high revs which is probably worst case scenario in terms of engine life.


1. What is the target AFR you set the computer for?

The target AFR changes slightly thought the RPM band. But this bike in particular runs about a 13.2-13.4 from idle most the way up then richens up to around 13-13.2 AFR at WOT just for the added "insurance" of keeping everything nice and cool. These Bikes being such a small single cylinder motor perform better in this range, where as a R1 for example likes it a bit richer at 100% throttle at high rpm like 12.8-12.9

2. You have options to delete or keep the O2 sensor. If kept, is the system running in a closed loop for AFR detection? If so is the system ALWAYS in a closed loop or are there spots (idle? WOT?) where the system reverts to Open loop? I don’t think the O2 sensor is a wideband so I am not clear how your ECU flash would work while retaining a narrow band O2.

We do have an option to delete the o2 sensor, and do recommend it especially if you are local to us, because we have created the map to run at our sea level so it will be spot on. The system is always in a closed loop, because the o2 sensor really dosen't exist to the bike anymore so it would have nothing to read off of. The ECU in the bike has different maps it runs off of for different instances, an example would be a cold start at idle it measures the intake temps vs engine temp and knows its cold so it has an enrichment map that it would use until operating temp is achieved. The o2 sensor is in fact a narrow band, so it uses voltage to calculate the "afr" and does not have nearly the capabilities that we are used to seeing with wideband o2 sensors. If you chose to leave the o2 sensor on, the factory sensor would work just the same as it did while it was stock, because we are re calibrating the binary in the ecu, the bike has no idea that its actually been flashed and just makes its "corrections" as it normally would on any other factory map. There is no harm leaving it on there, but we have noticed better gains with it off because stock the z125 runs extremely lean in the higher up rpms and will always be trying to correct its self back to that.

3. Along the same lines, would the reflash work on an otherwise stock bike without causing it to run overly rich?

Yes, the flash will work fine on an otherwise stock bike. We do at least recommend the exhaust, being that the map was created with the intention of using our exhaust. As previously stated the z125 runs shockingly lean especially at higher up rpms (14.3-14.6ish) so we felt as though it is a better option all the way around to richen it up quite a bit, not only for the gains that are achieved, but mostly because these bikes operate generally at wot or close to it and we don't want to see anyone melting down their pistons from really working these little motors, which i have read a lot about on the forums.

4. Do you bring back some of the advance that Kawi removed with their ECU update?

As i am not aware of what "advance" you are referring to, we did give it some more timing at wot to help get a little more horsepower out of these bikes. Our flashes are based off of the newest Kawasaki Binary, so with that we are putting the latest ecu "updated" maps into the bike, but with our fuel and ignition calibration. Our maps do have the cold start and idle fix that plagued the earlier model z125s so that would be a great feature for someone who dosen't have a brand new bike.

I work down the street from you guys and could stop in if that would be better.

Feel free to stop in anytime. Let us know if you wish to purchase anything from us before hand, so we can make sure we have it available for you when you get here.

I’m considering using an EFIE device that will intercept the signal from the O2 sensor and modulate it… this will allow me to shift Kawi’s stock map, but would only seem to work when the bike is running in a closed loop, and I cannot find any information as to when the bike is running in closed loop vs open loop.

You are welcome to use whatever device you wish to with our exhaust, i would not recommend this coupled with an ECU flash as it really wont net you anything. It would make sense that it will only work in closed loop otherwise its just going to endlessly keep trying to correct its self back to a factory setting while the device is trying to correct it back to your chosen value.

Love your undertail I want to pick one up, how do you mount the license plate? I assume you need to run an integrated tail light as well with that pipe?

The exhaust has a little threaded bracket welded onto the bottom of the muffler that our tag bracket screws right into. If you have seen a GROM or even a CBR600rr, it is the exact same setup on the z125. You do not NEED an integrated taillight, however if you wish to run rear turn signals, it would obviously be mandatory. Plenty of people in the motorcycle world ditch their signals and just use hand signals for turning. That is a matter of your preference and budget.

Does your intake include provisions to support the fairing (side fairings attach to stock air box which gets deleted with intake install)?

Unlike the GROM where the fairings are directly supported by the airbox, the z125 actually has its own mounts for the fairings to be held firmly and therefore the rod that is included in our GROM kits as well as many other brands simply isn't necessary for this bike.

If you have any other questions, you are more then welcome to email Ryan@toceperformance.com, or call and ask for Ryan and i will do my best to answer any other questions you may have. Thank you for your interest i hope to speak with you in the future. -Ryan
 
#12 ·
Still not clear when the bike is in open or closed loop. This is the biggest concern with running EFIE device. If stock ECU reverts to an open loop map at WOT then you are going to be running super lean cruising at high revs which is probably worst case scenario in terms of engine life.



2. You have options to delete or keep the O2 sensor. If kept, is the system running in a closed loop for AFR detection? If so is the system ALWAYS in a closed loop or are there spots (idle? WOT?) where the system reverts to Open loop? I don’t think the O2 sensor is a wideband so I am not clear how your ECU flash would work while retaining a narrow band O2.
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My understanding so far is ....
https://www.z125owners.com/forum/wh...-did-you-do-your-kawasaki-z125-today/15471-klx110-exhaust-mod-3.html#post118309
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i'm running a pipe and slightly better intake with NO- 02 sensor (unplugged) and its running better than it ever has using only the stock ECU
https://www.z125owners.com/forum/wh...-did-you-do-your-kawasaki-z125-today/15471-klx110-exhaust-mod-2.html#post118241
.
but still wondering if i can use the EFIE to richen across the board ?
Right now i dont think so because without the heat sensor from the 02' saying it is at 600 degrees it will stay in open loop .
 
#10 ·
Ummm... Narrow band running at 13.x:1 will not read any variation. At 14.7-ish it will oscillate between less than 1 volt and more than 1 volt output as the mixture varies SLIGHTLY. https://www.a-i-e.com.au/tech_stuff/view/6974/narrow_band_oxygen_sensors

This make me doubt everything they just said since a narrow band can't really do anything once it gets that rich, you will just be producing 1.xx volts and the computer can't know what is happening.

Also closed loop is running through control, open loop has no control from the o2 input, again refer to the link above.
 
#11 ·
Yeah... I think he typed it out quick and messed up a bit... this Ryan guy is their welder. I'm going to head in and talk to someone. Not ready to give up on the ECU reflash just yet need some more info.

I think deleting the 02 is the only way to make it work correctly and have the system run in OPEN loop the whole time.
 
#13 ·
According to this guy at Toce the bikes run a separate richer map (ie choke mode) until engine is up to temp then switches to normal map. without the O2 present the bike is obviously in open loop... maybe it runs the richer map by default to prevent damage? I have no idea. Guess it doesn't matter in any event because it seems the bike richens up without the O2 sensor in.

But my understanding of how open loop works is that it just runs whatever settings are flashed to the ECU and it doesn't matter at all what the O2 sensor reads. If the bike is running closed loop the EFIE device will be able to shift stock AFR richer or leaner by intercepting and modulating voltage received from the O2 sensor and sent to the ECU. But in cases where the system switches to open loop you are stuck with what kawi gives you because in open loop the modulated signal from the O2 sensor is irrelevant... and if you have the O2 sensor in, which you would need in order to use the EFIE device, it means you aren't getting the richer "choke" or "crap there is no O2 sensor" map, and you get the factory setting, which according to Toce is north of 14.6 AFR. Combine that with an intake and a pipe and you lean it out even more.

So... to me this argues for full ECU flash or piggy back system... but... I gotta ask... what do your plugs look like?

Mine are grey. Grey and clean and lookin' lean. If you tell me you have a nice toasted marshmallow brown that's a good argument for skipping the EFIE and just removing the O2... although I'm too anal to have CEL lit up all the time. Maybe Fox's black wire trick.

This used to be so much cheaper and easier with jets and needle clips.
 
#16 · (Edited)
The Grom forum link suggested that ?
.

1. "closed loop" refers to when the ecu does active adjustment based on the o2 sensor, this range is typically between 0-80% throttle on our lil bikes
2. "open loop" refers to when the ecu does NOT do active adjustment based on the o2 sensor but rather the map that it has calculated, this is 80+% throttle. Open loop fuel mapping IS BASED ON CLOSED LOOP AUTO TUNING. That is to say, if the ecu is being tricked into feeding the motor more fuel during closed loop (as it does with the EFIE reducing the voltage output of the o2 sensor), then Open loop fueling will also get a bump in extra fuel. The ECU has a formula to extrapolate out what the o2 sensor has done to fuel trims in closed loop and applies that out into the open loop fueling area of the map.
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Another Member...
it looks like the ecu is adjusting to the EFIE settings even during WOT. i thought it was going to run a set mapping for 80-100% WOT and not get richer.

.
Before installing the EFIE my temps on the way home were around 220*F - 230*F with 80* - 90* ambient temps. I ride my GROM pretty hard and I'm full throttle 1st - 3rd.
After the EFIE I instantly noticed an increase in power in the mid range and my temps now are 205*F - 215*F with the same ambient temps.
.......................................................................................
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but... I gotta ask... what do your plugs look like?

Mine are grey. Grey and clean and lookin' lean. If you tell me you have a nice toasted marshmallow brown that's a good argument for skipping the EFIE and just removing the O2... although I'm too anal to have CEL lit up all the time. Maybe Fox's black wire trick.
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I just pulled the plug (see pics) what do you guys think ?
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I wanted to ride my bike for a while before i made the Statement That ...
My bike is defiantly running cooler ! and the EFIE does that !
My bike is defiantly running stronger I instantly noticed an increase in power in the mid range and the EFIE does that !
If anything i notice a very slight blubber at around 4000rpm steady throttle . not always and VERY SLIGHT !
My bike has absolutely zero Decel Pop , even after long WOT and chop the throttle / But right after pipe install and 02 unplugged my first 10-20 miles or so it had Crazy amount of Decel Pop , but then i think the ECU corrected itself even with the 02' unplugged because theres NO/ZERO decel pop now at all
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Also, there is NO black soot what so ever in my tail pipe, cant even get any on my finger from inside .
 

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#15 ·
Yes Greg agree... the problem is that the fuel trims flashed to stock ECU are set too lean so with EFIE and O2 sensor you would end up richer across the board with the exception of WOT.

The exception to this would be if the stock ECU's "open loop" fuel trims were set dynamically... learned from 02 sensor and subject to change as the ECU learns the settings of your individual bike. I doubt this is the case and tend to believe that they are static... set from the factory and never change. This is admittedly just conjecture on my part. But it would seem that in the case of a malfunctioning O2 sensor they would want a static baseline to fall back on to prevent damage.
 
#17 ·
With modern fuels, reading plugs gets harder. All the additives make the insulator cleaner on average.

I can't decide if I see some shrouding on that plug from the ground strap or not. I'm tempted to index mine when it comes out.

Closed loop is where the trims are set as well as added to the programmed value, open loop the trims are added to the programmed value. These fuel foolers can often screw up your trims which causes the full throttle (open loop) to go way lean. Had a Dobeck what'samacallit on my Buell and it really screwed it over. Not sure how the EFIE works but I've seen plenty of people suggest they work pretty well, even on bikes that still have closed loop functional.

Why they work might be down to the limits set for the trim function. If you change intake and exhaust, then the trims may not be allowed to go far enough to fully cover the changes. Since the EFEI adds duration to the pulses driving the injector, it may add that little extra needed to let the fuel trims stay in their allowed range. Fuel trims on some vehicles are limited to 85-90% through 125% which generally covers their intended working conditions through elevation changes to about 10,000 feet (maybe slightly more) and atmospheric changes in pressure. Generally.

I hope someone cracks the factory ECM programming and gives us a cheap application to allow tuning, otherwise if I ever get where I'm modding for performance it will be a Hoedar ECM so I have full control over timing and fuel.
 
#19 ·
What a guy!

Your wideband will probably still read correctly even if you botch it and create an exhaust leak... just sayin. Only way to learn is to practice, sometimes that results in failure, no big deal. I believe in you!