14 MPI Viper RPM and Top speed

[WootTootViper]

This might be a dead horse but I keep reading a lot of conflicting information. I have a 14 mpi Viper and I was wondering what my target rpms should be. It has machined clutches, adjustable screw in weights, taller gearing and the turbo. 0-80 is really quick but from 80-100 is slow rolling and I feel as if I should be closer to the 110 mark. RPM is maxed out at 8400 and that seems low. 9200 is a rev limiter which I couldn’t stay out of before the clutch kit. I paid a shop to set the clutch and I’m not happy. If I let off and coast and then blip the throttle (2 stroke habbit) it makes like a whirring/slipping sound from the clutch and the sled doesn’t really go. If I just hammer on it it doesn’t slip just grabs and goes. I don’t understand clutching honestly. If you have any help I’m trying to learn because local shops aren’t cutting it. Thanks.

 

[murdered141]

It would help if you specified who's clutch kit you have, what gram base weight and which springs in primary and secondary.
My assumption is too much weight in primary or too stiff of a spring is keeping your revs down, also too weak or not enough twist in secondary spring that's slipping your belt.
With out specifying details, we can just guess but it's definitely a clutching issue, I'm sure others with tons of clutching experience will chime in.

 

[WootTootViper]

1. It had the Allen Ulmer clutch kit. The secondary spring is red the primary’s spring is black and all I can find is one yellow dot on it. The spring wrap is at 1&6 and the shop I took it too said I got ripped off and it had stock weights and cam arm in it so they took those out and installed the dalton pro quick adjust cam arms I have no idea how to check the weights on them. I asked for the old cam arms and they do look like they are in fact part of Allen Ulmers kit. This forum won’t let me add picture for some reason.

 

[WootTootViper]

After a little more reading I think my issue may lie in my secondary spring being wrapped too tight/too stiff?

 

[murdered141]

On another note I would check all boots and clamps for boost leaks, even non turbo viper's are quick to 70-80.
6-1 is not tight at all but it my be depending on your spring.

 

[WootTootViper]

What’s a good way to check for leaks? Spray starter fluid and see if it revs? Iv checked the exhaust and header last year and put new gaskets on all of it so I know the exhaust is good.

 

[Yamadog]

Well if 8400 is Max then too much weight in the arms or you are down a bit in power. 1st off which viper rtx, ltx, xtx? Which MPI kit do you have? An original stage I from 2014 with intercooler or later kit supposedly 190 with electronic boost control? Next what muufler? The. Quiet trail MPI muffler on a 190 kit restricts so badly hp is really between 150 and 165. Only with the race can will you see anything close to 190 hp

Is the gearing stock?

Gearing is gearing adding the turbo will get you there faster but not add many more mph to top end it is all about the ratios of rpms to upper, lower hears and driver size.

 

[WootTootViper]

Viper Ltx supposedly dyno tuned by ulmers team to 200hp with the dealer installed mpi from “factory” quiet trail muffler. And I believe 21/41 gearing. Could hang with my dads stock sidewinder until I would bang the rev limiter last year with the old clutching setup. So until about 55 mph.

 

[Yamadog]

well my 14 xtx was built in late 13 with the MPI stage 1 with the intercooler and quiet muffler. with as much work as could be done stock it was never even close to 200 hp with 5#'s of boost. After the motor blew and I rebuilt it with low compression pistons and upgraded the fuel pump and added 4th injector and race muffler - at 9 #'s of boost it was 225 hp and at 14 #'s on race fuel it was about 275 hp. The clutching was dyno tuned by Ulmer for the 14 #'s at 8900 rpms and when I was running at 9 #'s on pump gas it would snap to 8800 then drop back to 8600.

That complete setup is now in my 15 on a stock compression motor with head studs and flash to retard timing and raise rev limiter I make the same hp as the old sled at 2.5 #'s of boost less for each setting.

the 21/41 gearing should give you 7 more mph top end if you have the muscle to turn it but it may be too much for the hp. The gearing chart speeds are a lie I am running 26/44 gears in the 15 and the chart says 134.3 mph with 8 tooth 3.0 drivers and the best ever on ice was about 119 and here is 114 on snow at 8950 rpms. The 14 has made passes in 1000 ft at well over 136 mph and still has a long way to go, needs more tuning.

Here is the 14 in race trim waiting till next season and 2 hips to be replaced so I can sit down on it again!

 

[WootTootViper]

21/41... 1.95 gear ratio 86 link chain. Matching option #3 , machine secondary for 8dn belt.

 

[WootTootViper]

Yeah I figured the 200 was a stretch just wish someone around where I live knew how to tune a clutch.

 

[Studroes144]

Best starting point will be to check and see what dalton weights you have. If you pull the primary clutch cover off along with the belt you’ll be able to push the primary clutch together and read on the side of the weights what model they are. That alone will tell you what your base weight is. If you’re only pulling 8400 rpm on one of the lower boost kits you’re only making 150 horse tops, these sleds need to run right around 9000 rpm to get peak performance. Next thing will be to find out what the primary spring is, Yamaha springs all have 3 colored dots on them are the colors are coded to the spring force both at preload and full shift. If your spring is too soft it will also cause low rpm. Maybe someone else will chime in that knows what that spring is. In the meantime, did you get the spring that originally came in the Ulmer kit? If the red secondary spring is at 6-1 that’s going to be where you want it or very close, what is on it for a helix? Still Ulmer helix? I believe his are branded with a K, if that’s the case than your secondary setup is just fine. Start by figuring out what the weights are that are in it and that will tell a lot.

 

[WootTootViper]

The secondary is all ulmer so I’ll leave that alone and play with the weights while I’m on the trail this week. Thanks for the input

 

[WootTootViper]

Also the primary spring is wore off on the outside so I can’t see the dots really.

 

[Mike P]

Well if 8400 is Max then too much weight in the arms or you are down a bit in power. 1st off which viper rtx, ltx, xtx? Which MPI kit do you have? An original stage I from 2014 with intercooler or later kit supposedly 190 with electronic boost control? Next what muufler? The. Quiet trail MPI muffler on a 190 kit restricts so badly hp is really between 150 and 165. Only with the race can will you see anything close to 190 hp

Is the gearing stock?

Gearing is gearing adding the turbo will get you there faster but not add many more mph to top end it is all about the ratios of rpms to upper, lower hears and driver size.

Very well said. I notice a big difference when I bolt on the Quiet Trail can vs the Race Can.