MOUNTAIN VMAX4
Pro
I was told there was some runability problems with MBRP exhaust on Nytro, I am having some with mine not sure if it has to do with my mbrp or not. Anyone else noticed any problems? Or heard anything?
natedawgedog
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if you want to try out my exhaust it would take just a few min to swap them out... that could at least tell you if its the pipe or not...
with that said I think you just need to get the pc5 and be done with all the guessing! mine works great... well you know that
with that said I think you just need to get the pc5 and be done with all the guessing! mine works great... well you know that
tapex_07
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What are your issues your having?
ViperTurboPete
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Which MBRP do you have...the race can or the trail can? I have both, but with the race can on it now. I haven't tried it yet other than on the stand in the garage.
MOUNTAIN VMAX4
Pro
MBRP
The problem is a stutter at high rpm mostly I notice a little power loss the sled still runs great but I can tell something is not right!! When I was drag racing my buddy Travis could hear the noise I was describing while I ran down the track so its not just me. And that is why you won Nathan LOL 
I am not sure it is about a 4.5 inch round 14 inch long in the big part, I extended the exhaust and mounted the mbrp clear at the rear of the sled and the exhaust dump out through the part the snowflap hangs from. I bent it pretty bad and could be restricting flow now and I am replacing it this season any way but it did this problem for a long time before this happened.
Nathan, I have the Boondockers fuel system and I lean it out or richen it up it does not get rid of the sound. I would not mind trying that but I need some snow to run it hard in I wont notice it unless it is rapped out. And it is not hitting rev limiter one time I thought it was so I added a bunch of weight still did it way away from rev limiter.
Maybe I need and AFR guage then when it does it I can see what its doing!!
Does pipe length matter on a four stroke? I dont think so but maybe!
Someone mentioned reflash the ecu fixes a similar problem but I called a dealer and they said they do not do that!!
The problem is a stutter at high rpm mostly I notice a little power loss the sled still runs great but I can tell something is not right!! When I was drag racing my buddy Travis could hear the noise I was describing while I ran down the track so its not just me. And that is why you won Nathan LOL
I am not sure it is about a 4.5 inch round 14 inch long in the big part, I extended the exhaust and mounted the mbrp clear at the rear of the sled and the exhaust dump out through the part the snowflap hangs from. I bent it pretty bad and could be restricting flow now and I am replacing it this season any way but it did this problem for a long time before this happened.
Nathan, I have the Boondockers fuel system and I lean it out or richen it up it does not get rid of the sound. I would not mind trying that but I need some snow to run it hard in I wont notice it unless it is rapped out. And it is not hitting rev limiter one time I thought it was so I added a bunch of weight still did it way away from rev limiter.
Maybe I need and AFR guage then when it does it I can see what its doing!!
Does pipe length matter on a four stroke? I dont think so but maybe!
Someone mentioned reflash the ecu fixes a similar problem but I called a dealer and they said they do not do that!!
bholmlate
Expert
It sounds to me like it is the good old lean condition that all the nytro's have when you run aftermarket exhausts on them. It suppose to happen even with the stock exhaust but you can't hear it as good because of the muffler.
Does it happen with constant throttle or just when you jump on it???? It was explained to me that it is part of the engine braking system circuit of the injection system on the 4-strokes. When you jump on the throttle really hard it will open the braking circuit causing a slight lean condition for a very short period of time. I talked with Allen ulmer w/ Ulmer racing and he gave me another map for my PCV but it still did not clear it up completely. I am not sure if flashing the ECU would help this condition or not. good luck with it
Does it happen with constant throttle or just when you jump on it???? It was explained to me that it is part of the engine braking system circuit of the injection system on the 4-strokes. When you jump on the throttle really hard it will open the braking circuit causing a slight lean condition for a very short period of time. I talked with Allen ulmer w/ Ulmer racing and he gave me another map for my PCV but it still did not clear it up completely. I am not sure if flashing the ECU would help this condition or not. good luck with it
hugger70mtnmax
Expert
I noticed it even with the stock exhaust. When I upgraded And put the PCV on there didn't seem to have the problem after that. Mine seemed more like it was popping back through the intake when I was running it stock.
ViperTurboPete
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This so called "lean condition"...can it cause engine damage as it would on a two stroke?
HYFLYR
TY 4 Stroke Guru
Total pipe length isn't exactly important but header length, and collector diameter is crucial.
MOUNTAIN VMAX4
Pro
Collector diameter
HYFLYER,
One thing I did change when I modified this exhaust to under tunnel I used a 2 inch pipe from the collector back to the muffler, and I bent the part by the collector so it was oval and cut the collector back just enough so it would flow more freely would this have anything to do with it?
I am changing this exhaust to an exhaust with internal metal baffles rather than packing cause I bent this when I broke my suspension awhile back.
I am about to start working on this sled now got the wifes phazer going again and am looking for ideas where to start looking how to fix this problem. Short of buying a wrecked Apex and going Nypex, that sounds fun!!
I am not sure its lean cause I can richen this boondockers way up and it still does it.
HYFLYER,
One thing I did change when I modified this exhaust to under tunnel I used a 2 inch pipe from the collector back to the muffler, and I bent the part by the collector so it was oval and cut the collector back just enough so it would flow more freely would this have anything to do with it?
I am changing this exhaust to an exhaust with internal metal baffles rather than packing cause I bent this when I broke my suspension awhile back.
I am about to start working on this sled now got the wifes phazer going again and am looking for ideas where to start looking how to fix this problem. Short of buying a wrecked Apex and going Nypex, that sounds fun!!
I am not sure its lean cause I can richen this boondockers way up and it still does it.
