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Palephase

The Efi Rodeo Aka Surging At Constant, Low- To Mid-Range Throttle

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Here's a question for the experts on FI systems: What predisposes some EFI systems to cause stalling and surging at constant throttle settings? Do they they default to throttle position sensor readings in the absence of exhaust mixture data?

 

For background, I have an '02 VFR which I dearly love 95-99% of the time The remainder of that time is a period of frustration mixed with vary degrees of apprehension when the engine will lose power, and then suddenly come back to life with a violence that leaves me wondering when it will break the drive chain. It can be so severe that I have actually looked back to see if a cage driver had caught me napping and hit me. The bike exhibited this behavior in stock form shortly after I bought it about 3 1/2 years ago with 7400 miles on it. I took it to a local shop which specializes in building much sough-after race engines and in which I have high confidence. They installed and tuned a Power Commander III, removed the lambda sensors and replace with 02 Sensor Eliminators, disabled the flapper, and blocked the PAIR valves, all of which are typical mods by VFR owners to address such issues. It worked fine for about two tank fulls and returned to its insidious behavior. Initially, the shop owner and I thought it was due to the vagaries of the VTEC system, but I began to pay more attention and noticed the issue was well below the VTEC transition range (6800-7000 rpm) at a much lower 4750-5250 indicated RPM, and even though it is more likely on ride home in the late afternoon when the outdoor temps are in the 90s, I've had it happen on mornings with temps in the low 50s, and correspondingly with coolant temps as high as 220° and as low as 168° indicated. The bike is throwing no fault codes and the Dynojet read-out shows the VTEC transition is just about ironed out and a little bit of a flat spot from about 4000 to 5000 rpm in the torque curve (typical for VFRs).

 

By installing the PCIII and removing the lambda sensors, in theory we have broken the control loop, yet it seems to me that the ECU is trying to assert control anyway, and by going up or down 1500-2000 rpm several times over the course of about a minute, I can usually tame the bucking bronco.

 

A little Google searching tells me VFRs are not the only bikes known for this behavior even though it does not seem universal, and the problem usually occur at constant throttle inputs at about 5000 rpm for four-cylinder engines. There are many how-I-finally-healed my-bike testimonials, but for every person for whom the technqiues work, you can find at least one more for whom the same "fixes" were ineffective, which tells me that few if any understand the root cause(s) and that most are simply putting bandages on symptoms.

 

I would greatly appreciate a response from anybody who understands the inner workings of the typical ECUs and who can comment on how the electronic governance within the black box, because it seems like the popular wisdom is actually misinformed.

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Unless the ECU of the VFR becomes open sourced (both hard AND software -wise), I doubt you can actually know how it works inside, legally that is...

 

Technically , from a (very noob) programmer POV, the ECU has a built in "self learning" part (which is like RAM , parameters keeps changing depending on other paramemters)

 

its sort of like the butterfly effect ... if i can actually make out how every VFR ECU work AND CONSISTENTLY , I'd be headhunted for one of their departments...

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My trusted mechanic loves Honda bikes but is quick to point out their shortcomings as well which is electricals.

 

Have you gone through the bike's wiring and cleaned all the contacts? As well an 02 model year bike is likely to have some sensors that might be going bad and it might be worth replacing questionable sensors if for anything for future peace of mind and reliability.

 

If you give up in your quest Kevin at Caylormade motorsports (my trusted mechanic) also rides a VFR himself. Give them a call. They might be able to help out. Tell him that Robert Chase sent you. And if you end up in the shop say hi to my two R6's that I am desperately missing right now. :)

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My trusted mechanic loves Honda bikes but is quick to point out their shortcomings as well which is electricals.

 

Have you gone through the bike's wiring and cleaned all the contacts? As well an 02 model year bike is likely to have some sensors that might be going bad and it might be worth replacing questionable sensors if for anything for future peace of mind and reliability.

 

If you give up in your quest Kevin at Caylormade motorsports (my trusted mechanic) also rides a VFR himself. Give them a call. They might be able to help out. Tell him that Robert Chase sent you. And if you end up in the shop say hi to my two R6's that I am desperately missing right now. :)

 

 

Hi,Robert, no, in fact I have not yet sorted through the connectors, and considering the relatively low amplitude of the signals, a noisy, high-impedance connection here or there could explain a lot. If that does not work and the recent trip to Livengood Motorsports does not turn up a significant finding in a bad sensor, I may just give Kevin a shout on the phone. Thanks much for the tip!!!

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My trusted mechanic loves Honda bikes but is quick to point out their shortcomings as well which is electricals.

 

Have you gone through the bike's wiring and cleaned all the contacts? As well an 02 model year bike is likely to have some sensors that might be going bad and it might be worth replacing questionable sensors if for anything for future peace of mind and reliability.

 

If you give up in your quest Kevin at Caylormade motorsports (my trusted mechanic) also rides a VFR himself. Give them a call. They might be able to help out. Tell him that Robert Chase sent you. And if you end up in the shop say hi to my two R6's that I am desperately missing right now. :)

 

 

Hi,Robert, no, in fact I have not yet sorted through the connectors, and considering the relatively low amplitude of the signals, a noisy, high-impedance connection here or there could explain a lot. If that does not work and the recent trip to Livengood Motorsports does not turn up a significant finding in a bad sensor, I may just give Kevin a shout on the phone. Thanks much for the tip!!!

 

 

No problem. And you would be AMAZED at the magic you can do just by re-seating connectors. I had a bike that was blowing it's main charging fuse after a ride at the track. Someone on a forum suggested I re-seat all the connectors and I did it and the problem went away. Something that simple made a huge difference.

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Hey Palephase,

 

I agree with Robert. This sounds like you may have a bad or mis-calibrated sensor, or some loose connections in the wiring. You might also check to make sure that none of the ECU wiring is worn through and shorted to the frame somehow.

 

In answer to your tuning question...All ECU's have a "map" in the background that runs the fueling(and ignition). The O2 sensor just supplements this to make sure that the fueling is very well controlled for emissions. On most bikes the O2 sensor isn't even used by the ECU in the higher throttle and RPM ranges. If an O2 sensor goes bad, the ECU is usually able to detect this. If the ECU detects a faulty sensor it will usually throw an FI light on the dash and revert to using the background "map" only.

 

All O2 sensors must be heated in order for them to work properly. Some sensors have a heater built into them, while others use the hot exhaust gas for there heating. Your VFR has the heater built in. When you install the Dynojet O2 Eliminators, it fools the ECU into thinking that the O2 sensors have not heated up yet. The ECU's response to this is to use its fueling map in the background only. This is what allows the Power Commander to change the fueling throughout the entire operating range of the bike.

 

I hope this sheds a little more light.

 

Best,

Timmer

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I agree with Robert. This sounds like you may have a bad or mis-calibrated sensor, or some loose connections in the wiring. You might also check to make sure that none of the ECU wiring is worn through and shorted to the frame somehow.

 

Thanks for your ideas, Timmer. The O2 sensors were replaced with 02 Eliminators when I had the PC III put on. I was still inclined to think electrical gremlins, but I just got the bike back from Livengood's, and Brian seems to have fixed it by seriously leaning out the 5K +/- 750 rpm range. The engine really seems to like the new map because it accelerates much more strongly than it ever had before, and the 5K bog down is imperceptible now. i can still feel it but only because I am looking for it, and then it only seems to happen with very high ambient temps, say around 95° and higher. To my surprise, leaning out the sub-VTEC range has actually dropped the operating temperature by 5-10°. I'm still scratching my head over that, but I'll take it.

 

However, Brian also echoed yours and Robert's point about cleaning, lubing, and reseating connectors. I'll be doing that when I change the oil in the next couple of weeks.

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