Had the Nytro out again today for some more tuning, and testing. I have had some issues with the Nytro not wanting to idle (extreme lean) and occasionally dying. It would then be tough to start. MPI suggested turning the idle/pilot setting higher from .5 to as high as 2. I tried this and in the shop and at the parking lot and that seemed to fix the issue.
We were riding in some good powder at a little over 7,000 feet. The idle issue started coming back. Anytime I would stop it would go lean and sometimes die. As the day went on it got to the point where it would not idle at all. Restarting the sled was tough. I turned the idle/pilot as high as 7 and it would mostly idle, but then was extremely rich at low speeds. I played with the altitude compensator setting and most other settings as well with no luck. I then noticed that when I would start the sled it would idle fine while the MPI fuel controller was going through it's start up procedure, but as soon as the controller went into normal mode the sled would immediately go lean and die. This lead me to believe the controller was faulty.
We decided to call it a day and hit the trail to head to the truck. We traveled probably 5+ miles on the trail and dropped to 5800 feet and all the while I was turning the idle/pilot setting steadily lower until I finally reached #2 while at 5800 feet in elevation. The sled idled perfectly with no hint of dying. I turned it off and restarted it with no issues. This REALLY threw me since the poor idle and dying where showing lean and reacting to controller changes as lean, yet dropping in elevation (leaning) had somehow cured the problem. The sled continued to run great to the truck and when I unloaded at home.
After talking to a friend about it and giving it more thought, I am starting to wonder if the issue is NOT the controller but the air temperature sensor that was originally in the stock airbox? MPI has you simply zip-tie the sensor to the wiring harness it comes out of. This conveniently locates the sensor right below one of the open holes in the hood of the Nytro. This would allow cold snow (I was in powder when this issue came up) to dump right on the sensor. The other thing is that when in powder I notice a LOT of steam from the motor. It comes from all the snow going in those holes and hitting the motor. This steam is undoubtedly hitting the air sensor. I am not sure what the air temperature sensor does in reaction to hot or cold temperatures, however, I am thinking that either the cold snow or the hot steam is throwing the sensor, and therefore the EFI system, for a loop. Why else would the idle mixture get richer by dropping in elevation and getting out of the powder?
Does anyone know what the air temperature sensor actually does and/or have other input on this issue?
We were riding in some good powder at a little over 7,000 feet. The idle issue started coming back. Anytime I would stop it would go lean and sometimes die. As the day went on it got to the point where it would not idle at all. Restarting the sled was tough. I turned the idle/pilot as high as 7 and it would mostly idle, but then was extremely rich at low speeds. I played with the altitude compensator setting and most other settings as well with no luck. I then noticed that when I would start the sled it would idle fine while the MPI fuel controller was going through it's start up procedure, but as soon as the controller went into normal mode the sled would immediately go lean and die. This lead me to believe the controller was faulty.
We decided to call it a day and hit the trail to head to the truck. We traveled probably 5+ miles on the trail and dropped to 5800 feet and all the while I was turning the idle/pilot setting steadily lower until I finally reached #2 while at 5800 feet in elevation. The sled idled perfectly with no hint of dying. I turned it off and restarted it with no issues. This REALLY threw me since the poor idle and dying where showing lean and reacting to controller changes as lean, yet dropping in elevation (leaning) had somehow cured the problem. The sled continued to run great to the truck and when I unloaded at home.
After talking to a friend about it and giving it more thought, I am starting to wonder if the issue is NOT the controller but the air temperature sensor that was originally in the stock airbox? MPI has you simply zip-tie the sensor to the wiring harness it comes out of. This conveniently locates the sensor right below one of the open holes in the hood of the Nytro. This would allow cold snow (I was in powder when this issue came up) to dump right on the sensor. The other thing is that when in powder I notice a LOT of steam from the motor. It comes from all the snow going in those holes and hitting the motor. This steam is undoubtedly hitting the air sensor. I am not sure what the air temperature sensor does in reaction to hot or cold temperatures, however, I am thinking that either the cold snow or the hot steam is throwing the sensor, and therefore the EFI system, for a loop. Why else would the idle mixture get richer by dropping in elevation and getting out of the powder?
Does anyone know what the air temperature sensor actually does and/or have other input on this issue?
I wondered about that too Hammer. I'm not sure going out the hood with an intake is possible on the Nytro because of the lack of room. I'm also not sure I wnat a filter sticking out.
One of the first things I thought of was snow restricing my flow, but that would cause a rich condition not a lean one. I thought about the intake sucking in hot air, but that too would likely cause it to be rich. Also, the rise in elevation would cause rich not lean. I seem to be having the opposite problem of what you would think I would have under these conditions. That is what has us wondering about the air temp sensor, or even some other sensor.
I am certainly open to all possibilities, but something to do with the powder snow seems most likely since that and elevation are the only two variables that I can identify.
Where does your air temp sensor reside? Is it near those to big hood vents I see in your pic?
One of the first things I thought of was snow restricing my flow, but that would cause a rich condition not a lean one. I thought about the intake sucking in hot air, but that too would likely cause it to be rich. Also, the rise in elevation would cause rich not lean. I seem to be having the opposite problem of what you would think I would have under these conditions. That is what has us wondering about the air temp sensor, or even some other sensor.
I am certainly open to all possibilities, but something to do with the powder snow seems most likely since that and elevation are the only two variables that I can identify.
Where does your air temp sensor reside? Is it near those to big hood vents I see in your pic?
You think I wanted that fuggen thing sticking out of my hood ... been-there-done-this ... open-loop fuel injection system (MAP instead of MAF) ... first half of season one it was so inconsistent I was playing that fuel controller like a Nintendo game controller ... I actually wore the color off the buttons ... installed cold air intake and bypass valves... I've been running the same settings ever since (+-1) ... I've moved my temp sensor a few different places with no real effect ... sensor is currently ny-tied to a throttle body clamp.
Called to MPI to get their input..... He said they have had some minor idle issues, but nothing like what I experienced yesterday. I asked if it could be the air sensor and he said it could be. The only thing he suggested to try was the alt comp setting, which I have already tried.
I told them with no other input I would try heating and cooling the temp sensor to see if I could recreate the problem. He thought it was a good idea and asked me to let him know the results. He said he would tell his "engineers" about it.
Not exactly the tech support I was hoping for. I guess it is now my job to figure it out for them!!
I told them with no other input I would try heating and cooling the temp sensor to see if I could recreate the problem. He thought it was a good idea and asked me to let him know the results. He said he would tell his "engineers" about it.
Not exactly the tech support I was hoping for. I guess it is now my job to figure it out for them!!
Need for Speed 2
TY 4 Stroke Junkie
these fuel controllers are a joke.
MPIs system integration with the EBRS/ISC may also be a factor.
http://snowmobiles.yamahablogs.ca/2007/04/23/gimme-a-brake/#more-65
"The engine braking control is actually only part of a new system called ISC (Idle Speed Control). The heart of which is an electronically controlled air-valve in the intake tract, which has the ability to override the throttle setting to control idle speed as determined and executed by the ECU (digital ignition /engine control module). Okay so what the heck does this all mean? Simply put the computer analyzes engine RPM, coolant temperature and throttle (buterfly) position information taken from dedicated sensors. It then operates the intake air (ISC) valve to add or reduce air to the cylinder. This is a multi-function system. When the engine is cold, the valve opens to advance (raises) the RPM until the coolant warms at which time it adjusts air flow (closes) to hold a constant 1500rpm idle speed. When engine RPM is high and the throttle valve is shut, the ISC valve is rapidly cycled, allowing precisely measured amounts of air in, relieving the vacuum or ‘pumping’ action created by the intake pulling against the closed throttle valves"
http://snowmobiles.yamahablogs.ca/2007/04/23/gimme-a-brake/#more-65
"The engine braking control is actually only part of a new system called ISC (Idle Speed Control). The heart of which is an electronically controlled air-valve in the intake tract, which has the ability to override the throttle setting to control idle speed as determined and executed by the ECU (digital ignition /engine control module). Okay so what the heck does this all mean? Simply put the computer analyzes engine RPM, coolant temperature and throttle (buterfly) position information taken from dedicated sensors. It then operates the intake air (ISC) valve to add or reduce air to the cylinder. This is a multi-function system. When the engine is cold, the valve opens to advance (raises) the RPM until the coolant warms at which time it adjusts air flow (closes) to hold a constant 1500rpm idle speed. When engine RPM is high and the throttle valve is shut, the ISC valve is rapidly cycled, allowing precisely measured amounts of air in, relieving the vacuum or ‘pumping’ action created by the intake pulling against the closed throttle valves"
MPI is currently thinking along the same lines as you Hammer. They are looking at the EBS.... Hopefully they come up with something soon.
The other thing I'm wondering about on the Nytro is ... how much vacuum does the EBRS/ISC "relieve" ... because a Bypass-Valve is vacuum actuated ... no vacuum signal ... no worky.
gsxr
TY 4 Stroke Master
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iac freezing , may be a possibility
IAC? At the risk of sounding dumb, I don't know what that is.
I tried heating and cooling the air temp sensor last night but it did not seem to make any diferrence.
I rode again today. We got some nice new fresh powder last night. I went back to the same areas we hit the other day and some new even deeper snow spots. I had SOME idle problems but nothing like the other day. I did have several hard starts again, but still not like the other day. The only thing diferrent on the sled was that I had just enough filter fabric to cover the one vent on the left side of the sled that is just above the clutch. It seems that if I stay out of the powder for a while it will idle and start fine. Either this is a freakish coincidence or it has to do with something getting wet, or freezing.
I tried heating and cooling the air temp sensor last night but it did not seem to make any diferrence.
I rode again today. We got some nice new fresh powder last night. I went back to the same areas we hit the other day and some new even deeper snow spots. I had SOME idle problems but nothing like the other day. I did have several hard starts again, but still not like the other day. The only thing diferrent on the sled was that I had just enough filter fabric to cover the one vent on the left side of the sled that is just above the clutch. It seems that if I stay out of the powder for a while it will idle and start fine. Either this is a freakish coincidence or it has to do with something getting wet, or freezing.
The Apex has an IAC (idle air controller) so you won't see full vacuum on an Apex with a cold engine. Once the engine coolant gets to full operating temperature you should see 8"of vacuum at idle. You won't see full vacuum on a cold engine because the IAC bypasses air around the closed throttle bodies. The IAC is actuated by a thermal gel. When the gel heats and expands it closes a plunger and intake air is re-routed back to the throttle bodies.
Colorado Yamaha
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HAMMER ~ ok, I'll be ready for a new project sled in 1-2 years, so hurry up and retire so we ... I mean you ... can build it! Thanks for the continued great information. 
... October 2010 ...
