Yamahammer485
TY 4 Stroke Guru
Hey all, got an rpm issue
Long story short, before my rpms were low, about 10500 and wideband was richening up all of a sudden at near peak speed and speed would actually drop, so put in a brand new pink secondary spring wrapped at 90 degrees and got 118mph in 2000ft on ice @ just shy of 11000. The wideband was reading 12.7, 12.8 and the PCIII is set at 0% for this rpm and throttle. This was all done on a day where it was about 0 degrees C and the ice was pretty glare but really chewed up.
The next day, went on a 250km trip to huntsville, lots of bumps, etc.. Got high test gas at the Shell in Sprucedale.
Then the day after that, slightly colder temps, went to the exact same drag strip with new gas and it ran 194kmh on the speedo where before was 202kmh and today, tried it again and it only did 190 and was again revving low at 10500. Wideband was overly rich again at 12.5, and its the same temp it was today as it was when doing 202kmh. Nothing was even touched between rides.
After coming home I checked:
- Its perfect, no wear, only 450kms on it
- Alignment, also perfect
- machined surfaces are clean and were cleaned with scotchbrite and a cleaner 450kms ago.
- Checked sliders and track tension and alignment, all good
- all bearings were re-packed 450km ago
- Made sure secondary buttons were still there
- New donuts all around 450km ago
I am running 10% timing through the midrange, except for up top where im on par with what Allen has with his kits.
Am I missing something why this isnt hitting the higher revs like 11000 or higher(which is where I want them) like it was 250km ago??
The only things I can think of are:
- Variations in the air and ice causing rpm differences?
- PCIII acting up?
- Pink Spring maybe breaking in and settling?
- (long shot) possible engine damage from running too much timing?
Any ideas guys?
Long story short, before my rpms were low, about 10500 and wideband was richening up all of a sudden at near peak speed and speed would actually drop, so put in a brand new pink secondary spring wrapped at 90 degrees and got 118mph in 2000ft on ice @ just shy of 11000. The wideband was reading 12.7, 12.8 and the PCIII is set at 0% for this rpm and throttle. This was all done on a day where it was about 0 degrees C and the ice was pretty glare but really chewed up.
The next day, went on a 250km trip to huntsville, lots of bumps, etc.. Got high test gas at the Shell in Sprucedale.
Then the day after that, slightly colder temps, went to the exact same drag strip with new gas and it ran 194kmh on the speedo where before was 202kmh and today, tried it again and it only did 190 and was again revving low at 10500. Wideband was overly rich again at 12.5, and its the same temp it was today as it was when doing 202kmh. Nothing was even touched between rides.
After coming home I checked:
- Its perfect, no wear, only 450kms on it
- Alignment, also perfect
- machined surfaces are clean and were cleaned with scotchbrite and a cleaner 450kms ago.
- Checked sliders and track tension and alignment, all good
- all bearings were re-packed 450km ago
- Made sure secondary buttons were still there
- New donuts all around 450km ago
I am running 10% timing through the midrange, except for up top where im on par with what Allen has with his kits.
Am I missing something why this isnt hitting the higher revs like 11000 or higher(which is where I want them) like it was 250km ago??
The only things I can think of are:
- Variations in the air and ice causing rpm differences?
- PCIII acting up?
- Pink Spring maybe breaking in and settling?
- (long shot) possible engine damage from running too much timing?
Any ideas guys?
- Joined
- Apr 17, 2003
- Messages
- 5,529
- Reaction score
- 1,393
- Points
- 2,003
- Location
- Menno, SD
- Website
- www.ulmerracing.com
- Country
- USA
- Snowmobile
- 2014 Yamaha SR Viper LTX, 2014 Yamaha SR Viper RTX SE, 2015 Yamaha SR Viper MTX SE 162 (turbo), 2015 Yamaha SR Viper MTX SE 153
- LOCATION
- Menno, SD
- WEBSITE
- www.ulmerracing.com
Variations in air and ice. Conditions play a huge role in top end numbers. Also high test pump fuel will hinder performance! The pink spring at 90 is too tight for that spring as well. I would not go over 80 degrees on that spring.
SledFreak
TY 4 Stroke God
- Joined
- Feb 7, 2005
- Messages
- 5,511
- Reaction score
- 466
- Points
- 1,733
- Location
- Ontario. Canada
- Country
- Canada
- Snowmobile
- Current 2020 ThunderCat. - SOLD!
If it was timing it would miss bad like it had water in the gas. You would feel it.... The PCIII I believe would either work or not... Sounds like clutching issue to me.... But, I would check with Allen on what the AFR should be for each range of the Throttle position. Where is the sweet sport and adjust from there..
grader
TY 4 Stroke Master
remove ciols, remove rubber pieces from coils and clean with brake clean or solvent. also wipe out valve cover where coils sit to remove carbon trace.you wont even notice if the engine missfires but the performance drops off. also reduce the wrap on the secondary to 70. you were pulling good speeds before and nothing changed with the clutching. missfireing plug will give higher af reading.
Yamahammer485
TY 4 Stroke Guru
grader said:
If the coils are arcing on the motor, would that likely be because of dirt?
Because if thats the case, I just put in new plugs this season and the motor was squeaky clean, as well as the coils, but I wiped them down anyways.
That rubber peice that should be removed, is that the long sledner tube itself?, I never knew that came apart.
One more thing on the behavior of the sled. On the day it was running 202kmh, Id pin it and itd rev to like 11200 like nothing and hold it, now it barely goes past 11000 on initial shot. Also, currently it gets to about 190 then stays there and even starts slowing down, while at the same time the wideband keeps getting richer and richer, sometimes going to 12.3
My sliders arent sticking either. Before the pink spring, it was also doing this, and it felt like overshifting, kinda like bogging
My PCIII also has the over rev feature.
Thanks for the help so far guys!
Turk
Tech Advisor
Air density. It was a day with lower barometric pressure. A day like that will drop rpm,s & you will lose hp. The fuel injection system does not compensate for it.
grader
TY 4 Stroke Master
the coils have 2 pieces that can be removed, one at the bottom, one at the top that seals the hole. any black residue is carbon and will give the spark an easy way out, instead of through the plug.
Yamahammer485
TY 4 Stroke Guru
grader said:
I will check the coils and clean them for sure.
Also, it seemed to me that the day I seen 202 on the speedo and rpms at 11 100, was exactly the same (warm and rainy) as the day I seen 10 500 rpm and 190 on speedo. Could air pressure alone really account for this incredible drop in rpm?
Len Todd
TY 4 Stroke God
Turk said:
I thought the "atmospheric pressure sensor" was the input to the FI system to adjust for barometric pressure changes. Did I miss something here? I know the Carbs don't adjust for BP changes. But the FIs do. That is one of their "claims to fame."
Turk
Tech Advisor
Closed loop system...they don,t adjust for anything.
Last weekend barometric pressure was 86.9 on our gauges & nytro rpm,s were 8800 rpm.
Today we had huge air at 104 & rpm,s were at 9300 rpm with no clutching changes.
Last weekend barometric pressure was 86.9 on our gauges & nytro rpm,s were 8800 rpm.
Today we had huge air at 104 & rpm,s were at 9300 rpm with no clutching changes.
Len Todd
TY 4 Stroke God
Good Discussion. I learn something new every time we get into one of these. So, ... as I understand it:
Yes, the Atmospheric Pressure Sensor (APS) is in a closed loop system. The return signal is one of the inputs that allows our FI systems’ to make automatic fuel adjustments. The ECU feeds the APS 5 VDC. The resulting voltage from the APS is monitored by the ECU. Depending on the Atmospheric Pressure, the voltage returned from the APS and monitored by the ECU will change. That signal comes back to the ECU on the Pink Wire, in most cases. Spec is 5.25 to 4.75 VDC. But the return signal is typically < 5 VDC to > 4.75 VDC. The theory of operations is: The APS's return signal will vary with changes in atmospheric pressure. The Fuel is then adjusted by the ECU according to the signal returned from the APS, along with other input signals. There are a couple programming variables to directly vary the fuel. (i.e. number of pulses and duration of pulses.)
By definition, feeding a signal to a component and monitoring the return signal makes it closed loop. Feeding a signal and not monitoring the result is an open loop. Can't imagine any manufacturer bearing the added cost of a closed looped circuit and then not using it.
The use of the APS is the aspect of FI that allows a user to make altitude changes w/o manually adjusting the fuel. It also works for atmospheric pressure changes at the same elevation. I used to reprogram our own fuel maps for my Cats. Except for the added diagnostics capability that Yamaha provides, the theory of operations for these two fuel control systems are pretty much the same.
IMHO, if someone with our FI type fuel system is seeing more Rs on a higher pressure day, it was partially because the APS adjustment was allowing the engine to take advantage of that pressure change and the added air it provides the engine. Otherwise, the engine would have had more air and the same ole amount of fuel resulting in a more lean condition. Unless the mixture was fat to start with, that would be a problem.
If the pressure goes down, the engine output power will change, if nothing else is changed. There is just no real easy automatic way around that effect. However, the fuel system can be adjusted to allow the fuel to somewhat match the effect to allow it to run more efficiently, given the conditions. But with less air (e.g. resulting from a lower barometric pressure) and fuel, you still are NOT going to see the same power level. Thus, a change in RPM may be seen.
At least that was the way I was taught, back when they first came out with this flavor of FI system.
Yes, the Atmospheric Pressure Sensor (APS) is in a closed loop system. The return signal is one of the inputs that allows our FI systems’ to make automatic fuel adjustments. The ECU feeds the APS 5 VDC. The resulting voltage from the APS is monitored by the ECU. Depending on the Atmospheric Pressure, the voltage returned from the APS and monitored by the ECU will change. That signal comes back to the ECU on the Pink Wire, in most cases. Spec is 5.25 to 4.75 VDC. But the return signal is typically < 5 VDC to > 4.75 VDC. The theory of operations is: The APS's return signal will vary with changes in atmospheric pressure. The Fuel is then adjusted by the ECU according to the signal returned from the APS, along with other input signals. There are a couple programming variables to directly vary the fuel. (i.e. number of pulses and duration of pulses.)
By definition, feeding a signal to a component and monitoring the return signal makes it closed loop. Feeding a signal and not monitoring the result is an open loop. Can't imagine any manufacturer bearing the added cost of a closed looped circuit and then not using it.
The use of the APS is the aspect of FI that allows a user to make altitude changes w/o manually adjusting the fuel. It also works for atmospheric pressure changes at the same elevation. I used to reprogram our own fuel maps for my Cats. Except for the added diagnostics capability that Yamaha provides, the theory of operations for these two fuel control systems are pretty much the same.
IMHO, if someone with our FI type fuel system is seeing more Rs on a higher pressure day, it was partially because the APS adjustment was allowing the engine to take advantage of that pressure change and the added air it provides the engine. Otherwise, the engine would have had more air and the same ole amount of fuel resulting in a more lean condition. Unless the mixture was fat to start with, that would be a problem.
If the pressure goes down, the engine output power will change, if nothing else is changed. There is just no real easy automatic way around that effect. However, the fuel system can be adjusted to allow the fuel to somewhat match the effect to allow it to run more efficiently, given the conditions. But with less air (e.g. resulting from a lower barometric pressure) and fuel, you still are NOT going to see the same power level. Thus, a change in RPM may be seen.
At least that was the way I was taught, back when they first came out with this flavor of FI system.
Yamahammer485
TY 4 Stroke Guru
Some real good reading there, itd be news to me if the aps really did adjust fuel, which would be great!
So anyways, just an update, ran today, pressure on the guage was 977Kba and it was a cold (-10C) and sunny with some clouds.
On almost glare ice, its not revving as high as before when the pink spring was first put in, but much better than any attempt since my trip. Its revving 10800-10900 and did 199 on the speedo, still slower than before...
Then I decided to drop my wrap to 80 instead of 90 and could only get 194 and at like 10600rpm. The funny thing about this is that the day I had my good runs, I wrapped both 80 and 90 and seen absolutely no differences in rpm or top end speed, both at 202 @11 100.
This was a near perfect day, cold, crisp, fresh track and the day with my best run was a low pressure, warm rainy day. Im thinking my rpm problem is in the spring and how it might have retained an extra stiffness since it was brand new, then once it got broke in, dropped the revs some.
Going to try my white spring and see how it does....
So anyways, just an update, ran today, pressure on the guage was 977Kba and it was a cold (-10C) and sunny with some clouds.
On almost glare ice, its not revving as high as before when the pink spring was first put in, but much better than any attempt since my trip. Its revving 10800-10900 and did 199 on the speedo, still slower than before...
Then I decided to drop my wrap to 80 instead of 90 and could only get 194 and at like 10600rpm. The funny thing about this is that the day I had my good runs, I wrapped both 80 and 90 and seen absolutely no differences in rpm or top end speed, both at 202 @11 100.
This was a near perfect day, cold, crisp, fresh track and the day with my best run was a low pressure, warm rainy day. Im thinking my rpm problem is in the spring and how it might have retained an extra stiffness since it was brand new, then once it got broke in, dropped the revs some.
Going to try my white spring and see how it does....
grader
TY 4 Stroke Master
you are tuning the rpm with the wrong clutch. the secondary should be fine at 60 or 70. adjust primary weights for desired rpm. rpm will vary from day to day and with changing conditions.
