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Turbo Viper Clutching - RPM's

mdkuni

TY 4 Stroke Guru
Joined
Nov 18, 2004
Messages
996
Location
Houghton Lake, MI
Have a 2014 Viper RTX and need help getting the RPM's under control. I have the MPI trail turbo without EABC. This is my setup:

Stock weights modified
Heel: 6.4
Mid: 6.4
Toe 6.2
Total weight: 69.7
Low rpm engagement spring from Schmidt bros

Stock gearing
Secondary helix: 46/38
Sidewinder secondary spring 2-6

When i hit the throttle at 40-50mph it jumps to 8550 rpm's and climbs to 9270 rpm's.

I want to bring the rpm's down on top end but am worried they will be too low when the throttle is first opened. What range should I be shooting for?
 

Unwrap the winder secondary spring to 3-3 it is a very stiff spring, are you runing a button secondary?
That’s really to big of a helix spread for the stock weights IMO. Modified in what way?
 
Last edited:
Did you grind different ramps on them?
 
With the MPI trail turbo, you really don't want to run any higher than 8600. As I understand it, above 8600 the stock fuel system (fuel pump, injectors, etc) have trouble keeping up. Which can put you into a lean situation. For average trail conditions, I'd shoot for a target rpm of 8400. With that, the rpm will run a bit lower in sticky condition, and maybe a bit higher in perfect conditions.
 
If it’s a button clutch I would think a straight 46 helix would be better suited to those weights based on the rpm’s you have now.
 


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