RPM and boost are low

[FLYBYU]

Phone never rang or received any texts

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[nytrozula]

i'll call you later....

 

[FLYBYU]

Alright

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[scuba_nytro]

Something going on I'm running 8FP (Apex stock) base weight 67.8 grams empty with 7 gram MPI rivet tip, 4.5 gram (17.2mm) Yamaha rivet mid and base for a total weight of 83.8 gram total weight per arm at 8 psi pulls to 8900 no problem.

 

[MNBlizzard]

Nytro- Dude, is the clutch kit new? The reason I say the clutch is your problem is because you referenced running last year in your original post. So, I believe that your nytro has the exact same clutching setup as last year before you torched the blower and it ran just fine then. If so, the problem is within the clutch and I would definitely be concerned with the mileage. Bushings, ramps, broken springs, etc.

If this is a new clutch kit, then I too think the 60Y weights are too heavy. You are running without much extra weight and that is not ideal. Per STM you should be installing at least an additional 14 grams to each arm. Remember, no more than 4 washers or one tungsten in each location on the arms. My clutching is 50Y weights, Heel 1 tungsten + 3 washers, Mid 2 washers, Tip 3 washers. O-P-O primary, White Secondary Spring 6-1, K helix.

Good luck. If you cannot get it, my XTX 1.75 is for sale...it has never let me down.

 

[FLYBYU]

The only things changed was pulleys and obviously the supercharger. Maybe if that sled had a turbo it could pull that weight but not with supercharger. He still has 3 washers to pull. The weights would be empty then.

 

[MNBlizzard]

The only things changed was pulleys and obviously the supercharger.

If true Nytrozula, you definitely have clutch issues. You should of had to add weight with more boost not reduce it. I guess you could eliminate the SC from the equation by pulling the SC belt off and unplugging the GEMs, might not breathe right though. See if you pull your RPM then in this "stock" form.

Although a turbo is equally as nice, boost is boost. I would give the upper hand to the SC when getting on and off the throttle is necessary; like tree riding in the UP.

 

[FLYBYU]

Agreed!! By him pulling the other 3 washers off he'll be close.

 

[nytrozula]

OK guys....I think I found the issue! When my SC blew last year, shavings from the SC housing got inside the engine and needed to be cleaned out. While it was cracked open we made a decision to shim it. Ulmer just got back to me and told me my issue was due to the head shim and retarded timing in the new ECU reprogram. The clutch was setup before the head shim was installed. This has greatly reduced the hp and would require that I remove all the weights from the arms and run them empty. That is the direction I was heading I just couldn't understand why since everyone else seemed to be running so much more weight than me. So I am happy that it is confirmed.

 

[MNBlizzard]

Glad you found the issue and now you can get out and ride. I still think you should buy my Nytro for boondocking days, use yours for trails and lake ripping!

 

[FLYBYU]

A headshim doesn't greatly reduce hp. It affects low end torque. You should've started at 50 grams and add from there

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[TBird]

Although a turbo is equally as nice, boost is boost. I would give the upper hand to the SC when getting on and off the throttle is necessary; like tree riding in the UP.

Not correct, an turbo is driven by exhaust and does not rob hp, an SC is driven by engine and rob hp, so @ same boost level turbo will have more hp so boost isn't boost comparing turbo and SC, and therefor clutching differ.

This can be said compairing diffrent turbos also, a tiny turbo reacts (spool) faster but isn't as efficient as an larger and produce less hp @ same boost, so even diffrent size turbo boost isn't boost.

 

[TBird]

A headshim doesn't greatly reduce hp. It affects low end torque. You should've started at 50 grams and add from there

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So true.
Have owned many diffrent turbo sleds, the current one was an stock compression last year, this year i installed low compression pistons and @ same boost level it's pretty much same power @ dyno and it pulls same weight in clutch, but when driving i maybe can feel it's a bit softer @ bottom end, i say maybe because on snow on a mountain sled it's hard to tell, especially when it's not in same conditions, so it's an non issue, it's plenty strong @ bottom end still.
And with lower compresstion i now raised boost so i have much more weight in clutch.

 

[TBird]

To OP, i agree with FLYBYU, you would have more tuning opportunity if you had 50g supertip, 60g is in my opinion made for 10+ lbs.
Having to run weights empty = no tuning.

 

[mbarryracing]

Not correct, an turbo is driven by exhaust and does not rob hp, an SC is driven by engine and rob hp, so @ same boost level turbo will have more hp so boost isn't boost comparing turbo and SC, and therefor clutching differ.

This can be said compairing diffrent turbos also, a tiny turbo reacts (spool) faster but isn't as efficient as an larger and produce less hp @ same boost, so even diffrent size turbo boost isn't boost.

X2

The fact you aren't pulling the same clutch weight is an indicator it's making less HP at the crankshaft.