VFR VTEC 2008 - Throttle issue! (another one)

yeah i heard the pair valve removal is a necessity for accurate air fuel ratio readings. Definitely needs to be done before dynoing. But, I think with the o2's deleted, disabling the pair valve isn't going to do anything drivability wise. As there are not any sensors to pick up that extra oxygen in the exhaust.

 

Right on all counts, the Gen 5 Mk1 is catless and has no O2 sensors and was also based on the WSB RC45 engine which also had fuel injection.

What is interesting is going from a '03 build Gen 6 to the '99 Gen 5 in '05 I have found the Gen 5 throttle is much smoother and even though I still run above 4k from choice. Also unlike my previous Gen 6 the Gen 5 has no problems or stumbling cruising around from 3k mind that may also partly be do to change to a VFR trained mechanic who syncs my SV's every service.

Like others say know Gen 6 owners who have dialed out their throttle issues with PC3 O2 sensors removed and a custom map.

 

:amen:I just did it this morning and it's amazing what a difference it makes. Making U turns is so easy now that I don't have to feather the throttle just to keep the bike from bucking. Man, I wish I'dve had it like this when I took my license test.

 

FWIW, I did only the PAIR valve 'mod' to my '07 and that alone smoothed out the throttle response a bit, and the VTEC xsition considerably ...

 

Is there an advantage to using resistors to eliminate the o2 sensors, while not having a PCiii?

 

Well I decided to do the mod this morning anyway, and wow, its so smooth now!

 

I rarely run my bike, an 07, under 4000, and I find it very smooth. It took me a while to get use to keeping the rpms after I made the switch from my cruiser to the vfr, but now it is second nature. That's not to say that pc mods wouldn't make it even smoother, but I would get in the habit of keeping it closer to 5000 at the low end and see how it behaves.

 

I usually keep it above 4k, but the 99cent resistors have definetly made a difference. Its like the bike finally has what its been missing.

 

you keep track of your milage right? it will be interesting to see how its affected with the o2s eliminated. extra fuel injected at steady throttle vs. being able to run the bike at lower rpms.

i have seen that the harley guys do this to most of their bikes as a cure for overheating, bad fueling, etc. but they complain of bad gas milage afterwards. i guess getting 30ish mpg sucks when your no faster than your average fart can civic lol.ound:

 

Yeah I keep track of my mileage. Ill keep you posted on if there is a drop or not.

 

+1 for PAIR valve mod. Got rid of most of the RPM flat spot. Its still there but manageable. Also tighten my throttle cables..

 

Until those mods are done(or instead of) feathering the clutch allows one to run at higher RPMs and still go at a slower speed. I do this for tight turns and slower starts. The VFR clutch feathers very well.

 

Do have have motorcycle emissions test in AZ? California doesn't yet, knock on wood. If you mean inspection, I would probably remove the PC, they wont see the o2 elems.

 

there's always the power commander ex... that and the pair mod without touching the o2's would be your best bet if you need to pass emissions. the power commander EX works with stock o2 sensors. and i dont think anyone in the emissions department will have any clue about the pair mod hehe

 

Arizona Emissions is a rather simple process...

Got_Wings,

I've lived here (AZ) for 9 years and have had my bike tested nearly every year. It's a simple tailpipe sample test (kind of stupid in my opinion for m/c's), so the question really is, how does the mod effect the h/c percentage? I really don't know, but I would suspect the bike would run a bit richer, causing higher amounts. I have the same issue with throttle surge on my 02, and was just dealing with it on the ride home tonight. I too am a new convert from the Harley crowd, so I'm getting used to keeping the rpms up above 4500-5000 w/o feeling like I'm hurting the motor.

Since the mod is so cheap, and easily reversed, I think I'll give it a shot. I'm running a BMC filter, and Scorpion pipes, so hopefully the bike will run somewhat smoother. :thumbsup:

 

Thanks Olddude,

Let me know how it goes. Putting on my 2 bros exhaust this weekend and will see how things go after that...if they dont improve (dont expect them to) I'm going to try the resistor mod.

 

You do realize that once the bike is at operating temperature the PAIR valve is closed and doing nothing whatsoever so the mod really doesn't help anything right? PAIR valve function is grossly misunderstood from what I have read on here. Basically when the engine is cold it provides additional air into the exhaust to burn the post combustion hydrocarbons (from the richened mixture) to create additional heat to warm up the O2 sensors and light off the catalytic converter. Once the motor reaches operating temperature the PAIR valve closes and doesn't do anything else. I suppose blocking it off may provide you a placebo effect.

 

I did the resistor mod on my bike but immediately took it off after taking one ride down the interstate. If the bike was held at a steady rpm the bike would start to lag and then when I would add more throttle it would surge forward and smooth out. I had done this mod to smooth out the throttle at low rpms but that problem isn't nearly as annoying as the lag and surging. Has anyone else had this problem with this mod? My concern is that if I do an exhaust and power commander and O2 eliminators the problem will return and make the bike unliveable on the highway.

 

Ruf, I have been noticing this problem as well lately. You will be cruising at a constant speed and then the bike just seems to lose speed on its own, so you give it a hint on throttle and it gets its power back and off you go. It is so annoying but I don't know if it has anything to do with the o2 mod. Most of the time the bike is ok and it only lags every once in a while. Last time it happened, I actually turned the bike off and back on and contined on my way, and the lagging was gone.

As far as MPG, my personal observations are that I gained a few miles out of every gallon after the o2 mod. Check out the link in my sig to see my mileage from Nov - Current. I did the o2 mod in late March and since then the avg MPG has been a bit higher.

 

A typical fuel injected motorcycle of five or ten years ago did not have O2 sensors. They use what is called an open-loop speed density system in which the fuel requirement (injector pulse width) is determined primarily by engine RPM and manifold vacuum. The ECU uses RPM and MAP values at any given time to look up the required injector pulse width from a table stored in permanent memory (ROM). Throttle position, coolant temp, air temp and sometimes a few other things are also used to fine-tune the pulse width. These systems are simple and low cost, and they work great when tuned properly.

Along came tightening emissions standards. To meet new emissions standards they went to a closed loop system. The closed-loop systems work in the same way as the early open loop system, but now they also utilize feedback from O2 sensors to fine tune the injector pulse width even more. They use narrow band O2 sensors that are only accurate at 14.7:1 air/fuel ratio which is what is required for the most complete combustion of gasoline. This is the desired AFR to achieve low emissions for cruising and light load. Most engines don't produce maximum power at 14.7:1, and in fact most would melt down at wide open throttle. Many engines will also not idle correctly at 14.7:1. For this reason, the O2 sensors are only used under certain conditions, and the system constantly goes in and out of closed-loop as these conditions change. In closed-loop mode the ECU is commanding a precise amount of fuel to achieve a 14.7:1 AFR, and when it switches to open-loop it reverts to the base fuel table which is calling for a significantly different amount of fuel, and there is a surge or lag of power. The surging we are all feeling is either caused by this transition or just by poor closed-loop programming. Automobiles do not have this problem because they have a more complex ECU with long term fuel trim memory as well as much higher processing power, and in some cases wide-band O2 sensors that are accurate throughout the entire operating range of the engine. In any case, it's the closed loop operation that is causing the surging.

The ECU monitors the voltage of the O2 sensors, and will not go closed-loop until they are warmed up. The ECU detects that the sensors are ready by looking for a voltage swing on the O2 inputs. When we disconnect the sensors, the ECU detects a sensor not ready, and it stays in open-loop mode, and no more surging. In open-loop it just runs off the base fuel table like the old days, no harm done other than increased emissions and fuel consumption. Luckily for us, these are simple ECUs and they do not set a code for a long term O2 sensor malfunction, they have a much simpler diagnostic that checks the sensor's heater coil circuit and if it is open (disconnected) it sets a code. This is why a resistor across the heater circuit prevents the FI error. In fact, the resistance value is not critical other than selecting one that will not get too hot. 330 ohm 1/2 watt or 820 ohm 1/4 watt are the lowest common values that should be used. Below those values the resistors will be operating above their capacity and may generate excessive heat. A 1k ohm 1/4 watt is a very common resistor and works fine. There is really no need for a resistor at all if you are not removing the sensors from the pipes. You can pull the two sensor wires out of the plug and just leave the white heater wires connected.