2-STROKE SNOWBIKE PIPE TEMPS... DOES THIS MAKE A DIFFERENCE?

wwillf01 · Nov 7, 2018

I know for me a seat of the pants cold pipes move the power around in the rpm range...I ordered a pipe from Neil and they are coating it to avoid rusting... Even with the coating it will happen ...

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M5- · Nov 7, 2018

portgrinder said:
Last time I shared something on here that was figured out with good old hard work and testing, someone else stole the idea and said it was their own.

Learned my lesson

Ditto

M5

Norma Stitz · Nov 7, 2018

Anyone care to theorize what’s actually happening in the pipes at different temps? I’m guessing the pipe temp is actually irrelevant and it’s the gasses temps inside that matter more. So a cold gas will speed the shockwaves that are beneficial to reflect the lost fuels back into the engine and if the timing isn’t just right is it possible that it’s pushing the fuel all the way through the engine and forcing the fuel and oxygen out the intake, or stalling it temporarily? Likewise if the gasses are too hot the shockwaves will be less efficient and lose some fuel out the tail pipe but maybe it has less impact on power than too cold? However I’d imagine that a ceramic coating would allow the gasses to be even hotter than normal by insulating the pipe somewhat. Similarly to wrapping.

powdermuncher · Nov 8, 2018

Now someone correct me if I am wrong??

In my mind we have snowmobile engines with insulated pipes designed to run hot for proper wave action at sustained RPM and output.

On a bike the pipe is always in the breeze and output is seldom steady and sustained at high levels for extended periods--so it is designed to run on a cold pipe.

Now if you insulate that pipe and run a solid 30+ second pull the heat build up in the pipe will change the wave enough to drop it of the ideal timing for best power.

This would leave to reason that we should have an insulated pipe specifically designed to run hot with sustained high output tuned for snowbike use.
There is a reason sleds have gone that way.
Or make do with a top end pipe in bare metal that has a reasonable good tune on a cold pipe and try to keep the pipe as cold.

Norma Stitz · Nov 8, 2018

Well if we only run long wide open pulls in powder, then it stands to reason that the pipe will be cold through the whole run by being pummeled with powder.

Question, do the EFI smoker sleds monitor pipe temps and alter fueling using the data gained from downstream sensors?

Answ3r · Nov 9, 2018

Norma Stitz said:
Well if we only run long wide open pulls in powder, then it stands to reason that the pipe will be cold through the whole run by being pummeled with powder.

Question, do the EFI smoker sleds monitor pipe temps and alter fueling using the data gained from downstream sensors?

I would assume that they do judging by that patent.

https://patents.google.com/patent/US7258107

Answ3r · Nov 9, 2018

powdermuncher said:
Now someone correct me if I am wrong??

In my mind we have snowmobile engines with insulated pipes designed to run hot for proper wave action at sustained RPM and output.

On a bike the pipe is always in the breeze and output is seldom steady and sustained at high levels for extended periods--so it is designed to run on a cold pipe.

Now if you insulate that pipe and run a solid 30+ second pull the heat build up in the pipe will change the wave enough to drop it of the ideal timing for best power.

This would leave to reason that we should have an insulated pipe specifically designed to run hot with sustained high output tuned for snowbike use.
There is a reason sleds have gone that way.
Or make do with a top end pipe in bare metal that has a reasonable good tune on a cold pipe and try to keep the pipe as cold.

I would assume you are right.
To me the optimal solution would be a shielded/insulated pipe running higher temp and having the pipe design suited for that.

Second best option seems like having a raw, regular MX pipe, un shrouded and making do with the little lag when it's too cold, and the little loss when it's too hot from a sustained pull.

I wonder if certain pipe shapes/design are less sensitive than others ?

2smokin · Nov 9, 2018

So are we assuming that the extra load in our application will take a regular pipe up to the same temps we would have in the summer even when its buried in snow? It seems like it wouldn't to me, these pipes perform well in dune applications which is similar in terms of holding her wide. So unless the hot pipe is losing power in the dune scenario it seems that a bit of insulation would be proper to get to the same temps. The other part i dont get is it seems that a good amount of people argue that any sort of insulation is losing power on bikes, presumably this would mean that cold pipes make more power to some extent. It would be great to see some real data, the claim that the coated pipe loses 15% seems crazy, seems as though you would notice a huge power difference when the outside temperature changes which I cant say iv'e felt. It would be very interesting to know how many degrees difference the wrap or coating even makes, the one thing I would sure think it would help with is temperature consistency.

portgrinder · Nov 10, 2018

some things to ponder:

-pipes are based on resonance of the exhaust pulse. the pulse speed is the speed of sound. this changes with temp.

-density of air also changes with temp. denser air, all else being equal, makes more power as you are processing more of it every cycle.

-sleds have a cvt. so they only see full load at one rpm. bikes very different

-a bike with a tire can break it loose very easy. a bike with a track has much more load at all rpms. peak power doesnt mean much if you cant get to it. diesel vs a hemi.

ceramic vs uncoated isnt going to make any difference in my opinion. both will be ice cold once you have stopped for a minute and both will burn your pants when hot.

notwaitinginlines · Nov 15, 2018

I use my EGT to monitor best burn. Location of sensor is critical. 1250 plus and pay attention to avoid a meltdown. Riding a modified 330 with a Scalvini painted pipe. Built to over rev, Electron Mule and race gas..deep powder typical temps range around 1050 to 1100.

CATSLEDMAN1 · Nov 15, 2018

pipe temp

notwaitinginlines said:
I use my EGT to monitor best burn. Location of sensor is critical. 1250 plus and pay attention to avoid a meltdown. Riding a modified 330 with a Scalvini painted pipe. Built to over rev, Electron Mule and race gas..deep powder typical temps range around 1050 to 1100.

These are very realistic temps, over 1200 you are headed for trouble.
While riding at 1/3 throttle 850-900 creeping into 1000 maybe, low mid you don't want to see 1100.

Hard to judge low gears and low throttle, on my yz250 snow bike the first three gears I just shot by shifting no pipe temp, then took load on 4 th gear to find climbing pipe temps.

Enclosed engine and wrapped pipe always seem to run the best especially in early season fluff and cold. Another thread has been knocking this around. I like the wrapped pipe 2 or 4 stroke WITH LOTS OF SILICONE SPRAY, other wise you are operating a steam engine with freezing steam everywhere, dripping water building on the pegs etc etc. Our first bikes, no wrap, 6 years later, no bare pipes.

cbc76am · Nov 15, 2018

I always wrapped my header on the four stoke and soaked a can of silicone on it, it worked awesome and held up for 2 seasons no problem. I preferred the heat not transfer back to the engine or my pants with the 450.

I love the discussion here, I was pretty stunned when CPI told me the ceramic coating was a waste of HP and not to do so with my pipe for the CR500. I'm still a tad skeptical, but I don't have a dyno and Mike does....

I also ran the question by Neil of NPP, I'll post his reply if he gives me a clear one on hot or cold pipes. I think from a mid to upper range torque prospective it makes sense that the cold pipe will have a slower sound wave and have a bit more grunt if you are jetting perfectly. If you are a tad rich or too retarded on timing, i'd think everything would fall off as unburned fuel would then get in the pipe. Without a CVT and a pinned RPM for peak HP - i'm starting to think it doesn't matter as much.

I'm likely going to insulate the stinger and tail of the chamber to keep heat of my reed block, cylinder, and pants. I'll leave the front raw with silicone clear coat and toss a carbon guard on it.

M5- · Nov 15, 2018

All interesting points and for seeking out every last tiny bit of HP its all likely valid, but in my years of living with the 500 I would suggest don't over think this. If the bike makes more torque with the pipe cold and unwrapped then that's a bonus. Once you are on the pipe hard, snow is instantly vaporized. You cant tell. To me not exceeding a safe operating temp ie 1100-1200 degrees or so, is more important than fine tuning to the nth degree for a couple of peek HP. I'm all about motor longevity, and prefer keep it safe rather than burning it down. This IMO is more related to jetting than pipe wrap. I've had the pipe wrap and didn't think it made one bit of difference except for saving your pants.

M5

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2-STROKE SNOWBIKE PIPE TEMPS... DOES THIS MAKE A DIFFERENCE?

wwillf01

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M5-

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Norma Stitz

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powdermuncher

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Norma Stitz

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portgrinder

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