SDTRAILGER, seems you have the knowledge to make progress with this problem,,

With the CVK, that area of lean-out would indicate additional performance if it was mitigated. With the CVK, any leaning like I saw would be caused by an increase in volumetric efficiency and not a "carb issue". So I was determined to get that area below 13:1... A fact that most don't catch is that I settled on the first main jet that did that, without further testing even larger jets. Therefore, my lidless CVK recipes are actually the leanest possible for max power production. The midrange fueling control problem is the reason I stopped. I did not want to push midrange fueling any richer than absolutely neccessary.

If you are not familiar with "injector duty cycle, you should probably become so. There is no guarantee that the stock injector is capable of properly fueling (12.5 - 12.8) a 351 at wide open throttle (WOT) without running very high duty cycles. This is a measurement that may become extremely important as 351 fueling tuning progresses. It's where you keep adding fuel with the EJK buttons but not actually getting any more fuel in the combustion chamber..

 

You should keep the O2 sensor fully functional for many reasons. Firstly, a gentle Break-in will require the relative safely of closed loop fueling.
The OEM fueling scheme may not be optimized for using open loop fueling in the closed loop area of operation. In which case, defeating closed loop with O2 deactivation could cause unstable/erroneous fueling in the lower rpm, lower throttle operations.

The EJK will have to play nice with your O2 (and closed loop fueling) in place and functional..

 

. thanks man... an understanding where the current knowledge is set, levels off and begs progress is the important first step only .. So far I’ve gained from the data, your data, the forum data... I’ve yet to add... It is mod week though !! Lol..

So, I’m assuming the leanest for max power production also leads to best MPG and max power at WOT. Sounds like your determination paid off in a close to maximal reduction in lean spike, improving as far as possible given the parameter.. Will be nice if we can get a tune as close.. ... Ok, had read a little about injector max duty cycle and it will be keep in mind the potential to need a more robust injector.. One that will be able to continue increase as the 351 would need..

Starting with the O2 sensor and mod install this week. Have an awesome moto mechanic, a descent dyno butt but no Dyno guy yet..

Hopefully reports to follow!!

 

Yep, you got what it take to get this done..

There is (IMO) a prevailing "disconnect" between actual riding preferences and performance tuning preferences. When we are riding, we want great MPG when traveling, say, to and from work - and we want max performance whenever we snap and hold WOT. Getting both is NEVER a problem and they are NOT mutually exclusive to each other.

There is no such thing as "MPG @ WOT" . WOT should be tuned to produce the maximum power possible - because that is what is expected when a peep grabs WOT on a ride. Any idea that WOT can/should be tuned for best "gas mileage" is flawed logic and would only lead to improper fueling and a loss of WOT power levels.

Best WOT power levels are produced with a proper AFR that is ignited at the proper time, in a give combustion chamber to produce max pressure at approx 17 degrees ATDC. End of story. Where to start take serious knowledge (burn rates of various AFR's, flame propagation speeds, general characteristics of typical combustion chambers, camshaft design, etc) BUT you don't need to gather all that competence - you've got me - so just start by achieving 12.8:1 across the board @ WOT and you'll be close to optimum if not optimum. If wanting to go for more, lower AFR to 12.7 and retest, based on the results, a new AFR can be calculated to try next.

This is the technique we have to use because we are bound by the stock ignition scheme. Operating with a WOT AFR that is outside the envelope of the stock ignition scheme is counterproductive to power production.

E.G. A fast burning AFR that is ignited too early will result in max pressure too early, a loss of power, and could create pinging. A slow burning AFR that is ignited too late will create max pressure too late for max power and overheat the exhaust valve and header.. If the stock ignition point @ WOT is at an advance of 25 degrees, we must use AFR's that will "play well" with that ignition point.

 

Yep, didn’t necessarily mean it was high MPG at WOT so good clarification, assume I made the confusion. Was kinda just thinking that tuning the full range near ideal would be good for MPG and you seemed to additionally gain great top end.
Honestly, unless I’m able to somehow continue to tune without undue inconvenience, I’ll likely stop somewhere around reliable and improved with better torque/horsepower assuming that is even possible..
btw; heard using the O2 sensor may cause a too lean situation at start, low rpm etc.. may have to override and eliminate immediately after all..

 

There is no way closed loop fueling can create a "too lean situation". Constant streaming telemetry from the O2 is used to precisely control AFR - all in real time. Where ever you got this rumor, it would have to be proven with dyno charts and would be a malfunction. Idle AFR is NOT controlled by closed loop (O2) but is controlled by "idle tables".

BTW, closed loop operations are "in place" on all EFI bikes because it is used to control fueling in the operational envelope that the EPA tests for emissions certification. Any alteration to the closed loop operational envelope is technically illegal - which is why EJK had to stop selling the O2 terminators with their device.

If the O2 is eliminated, something will have to take control of fueling the closed loop area of operation in order to insure proper fueling. The EJK is simply an injector pulse width modifier - increasing or decreasing the signalling from the ECM before sending it to the injector. It therefore imparts its' own fueling scheme, based on its' programming and user settings, onto the engine. Apparently, it will require significant adjustments to fuel a 351 @ WOT and may not be able to fuel the various other operational envelopes - point being, without AFR sensing, there is no way to know what your fueling is..

Once WOT is tuned for max power, all part throttle and the throttle response can be tuned to whatever criterion an owner may want. These areas are responsible for MPG, and the "qualities" of the power band when not at WOT..

We have shown that the KLX engine will run "perfectly fine" with horrible fueling - from dangerously lean all the way down to AFR's in the 10's ! There is no way to know where you are and what you are sacrificing without AFR sensing and logging.( a dyno or bike mounted system)..

 

This is extremely encouraging and I do appreciate the full response. The O2 sensor will also help with altitude and other environmental changes as well.. I’m getting help on the build from an excellent moto mechanic who is good with tuning.. he immediately said we should work with the O2 sensor as well.. My other source is very well intentioned and simply trying to help out..
Ok, we need this build up and running and tuned via dyno .. my only main issue is I do not currently have a dyno guy... yet..

 

Sounds great, I'd be happy to be a member of "your team" ..
When/if you like, "Private Message" me for my contact info..

 

Cool, man really appreciate it.. we ‘are’ the team now ! Hopefully contributing some cool stuff, will definitely be in contact... Credibility demands that the mods commence.. I’ll try to get some pics up of the build.. while we are on lockdown here in Kalifornia (lifetime member) apparently my actual occupation is an essential service.. should be basically ready by next weekend.. with luck..

 

Interesting reading guys. I look forward to seeing how this turns out. I do have a quick question. I have the EJK on my 2018 250 and the instructions said to bypass the O2 sensor. This goes directly against what was stated above. Ive been running it for about a year now. Should I hook it back up?

Toph