RPM Drop at WOT Hot?

[Crossfire12]

I have stock sled, stock clutching ,no tune, was running 8800 rpm at wot, then drops to 8300-8400, belt is not slipping . This is happening mostly in the afternoon while riding, in morning sled runs great then as it warms up rpms drop. Temperature 40 degrees F, I believe hot intake temperatures. I did not monitor air intake temp Is there a way to stop this? I have a F1100,2012 it doesn't make a difference if it's warm or cold it will hold rpms, maybe drop 100. I never had this problem, I read a thread about hot intake temperatures here and mine is doing the samething but the thread never finished. Any ideas? Thanks

 

[1nc 2000]

Following. Same issue here.

 

[Crossfire12]

Anybody solve this?

 

[Big_Phil]

The intercooler can’t seem to keep up at higher boost levels when the temperature is just above freezing. When the temperatures are warmer, my intercooler seems to get clogged with snow easier as well. My sled is tuned, but I would imagine a stock sled would have similar results.

When it’s -10c, with a clear intercooler my intake temps are usually 0c or colder. I was riding last week, high speed running, temperature right around 0c, and my intake temps were 40c at Least when pushing it. That’s a difference of about 70 degrees F. Engines make about 1% more hp for every 10*f colder. That being said, my 270 tune is theoretically down 7% power with intake temps that high. That brings the power level down to 232ish hp. A stock machine running a similar iAT differential would be down about 15 hp or so, so you’re down to like 175 or so hp.

The 1100t that was riding with me seemed to run more consistent in the warmer weather, probably due to a larger intercooler.

Basically the sidewinder intercooler is not big enough, and all the plastic in front of it doesn’t help airflow either I would imagine. If it’s clogged even a little bit with ice, the intercooler stands no chance of being able to cool the air temps properly.

 

[1nc 2000]

I have had times when rpm's have been down 500 rpm's and my intake temp is 60f.

What is the reason they changed the fuel line return fitting for 2018?

 

[Crossfire12]

What about the fuel return, make it bigger? I believe what Big Phil concludes about the temp and intercooler. Is there a fix has anybody tried a bigger intercooler and made this better?

 

[Big_Phil]

What about the fuel return, make it bigger? I believe what Big Phil concludes about the temp and intercooler. Is there a fix has anybody tried a bigger intercooler and made this better?

Hurricane makes a bigger intercooler. I spoke with him about it briefly, he said you need to trim the plastics to make it fit. I'm sure it would help, but you would still have to ensure that the intercoler opening does not get clogged with ice and snow for it to work properly.

I have a few ideas about intercooler solutions on this sled, but I have to keep reminding myself I bought this to be a reliable and fast trail sled, and don't really want to be tinkering with it too much.

The cheapest and easiest way might be to add a second small intercooler just before the throttle bodies. The stock intake manifold design is not ideal anyways, the middle cylinder gets more boost than the outside 2. So tuners would be killing 2 birds with 1 stone with a part like that.

 

[1nc 2000]

Ttt

 

[snowbeast]

Hurricane makes a bigger intercooler. I spoke with him about it briefly, he said you need to trim the plastics to make it fit. I'm sure it would help, but you would still have to ensure that the intercoler opening does not get clogged with ice and snow for it to work properly.

I have a few ideas about intercooler solutions on this sled, but I have to keep reminding myself I bought this to be a reliable and fast trail sled, and don't really want to be tinkering with it too much.

The cheapest and easiest way might be to add a second small intercooler just before the throttle bodies. The stock intake manifold design is not ideal anyways, the middle cylinder gets more boost than the outside 2. So tuners would be killing 2 birds with 1 stone with a part like that.

How about some MO-FLO hood vents,would that help cool things down enough.

 

[Big_Phil]

How about some MO-FLO hood vents,would that help cool things down enough.

Its the intake air charge that is getting hot, so that wouldnt do much because the intercooler is out of the engine bay infront of the sled already. At stock psi, with a clear intercooler, not really an issue. This is more for the boosted sleds running 16+psi.

 

[snowbeast]

Its the intake air charge that is getting hot, so that wouldnt do much because the intercooler is out of the engine bay infront of the sled already. At stock psi, with a clear intercooler, not really an issue. This is more for the boosted sleds running 16+psi.

Ya,that will be me. I would of thought the CAI would of helped bring down temps some,as I have that to,its not thru the top,or even the bottom in the A-arm area where the t-1100 used to run it. I know mike Knapp did his CAI right thru the hood,but he said A/F went lean,so he aborted it,and went back to stock airbox and had better IAT numbers. When it around 30-40 degrees above zero,and I run hard,my IAT numbers go 80 and above,and it seems to lower my WO rpms by 400 or 500 rpms.

 

[Big_Phil]

Ya,that will be me. I would of thought the CAI would of helped bring down temps some,as I have that to,its not thru the top,or even the bottom in the A-arm area where the t-1100 used to run it. I know mike Knapp did his CAI right thru the hood,but he said A/F went lean,so he aborted it,and went back to stock airbox and had better IAT numbers. When it around 30-40 degrees above zero,and I run hard,my IAT numbers go 80 and above,and it seems to lower my WO rpms by 400 or 500 rpms.

Ya, its not the cold air intake thats the issue, its when you compress air, its raises the temp 10* or so for every psi. So if ambient temp is 40f, at 16 psi that air is prob close to 200* before the intercooler, and the intercooler should bring the temp back down. Once the intercooler gets a little clogged with snow, and gets heat soaked, it has no chance of cooling that air back down to where it should be.

The rpm drop is because for every 10* = 1% hp or so. So running 80* IAT instead of 30*, down 5% or 10-15 hp depending on the tune, some even more power loss as the ecu will pull back timing and add fuel.

 

[1nc 2000]

My sled lost rpm's (400-500) in stock form. Intake temps were the same as when I still had my rpm's.

Sled acts the same with a tune. It does not show any knock or any codes when this happens.

Big_Phil,
Do you have any information from Yamaha explaining on how the ecu pulls timing and fuel and at what temperature does this occur at? I would like to see that publication.

 

[Crossfire12]

Its the intake air charge that is getting hot, so that wouldnt do much because the intercooler is out of the engine bay infront of the sled already. At stock psi, with a clear intercooler, not really an issue. This is more for the boosted sleds running 16+psi.

When I ride the same day with the 1100 on 21 psi my rpms do not drop only if the snow is mealy and it would be by 100 rpms not 4-500. Why is it different how about the guys with the Apex turbos ? Do they drop rpm when it's warm out? Just like to compare.

 

[Big_Phil]

When I ride the same day with the 1100 on 21 psi my rpms do not drop only if the snow is mealy and it would be by 100 rpms not 4-500. Why is it different how about the guys with the Apex turbos ? Do they drop rpm when it's warm out? Just like to compare.

Apex turbos have intercoolers that are generally much larger than the sidewinders intercooler. Most of the Apex turbos are rear mount as well, so the turbo and charge pipes are cooled by snow.

The 1100 turbo intercooler is larger than the sidewinder cooler, it is also in a spot where it does not get clogged with snow.