I have 450 miles on my viper I built this year and I love it, I put a boost it kit on it with the GSX turbo on it and an does it rock. I run at 12 pounds on 50/50 race gas and 91 with out a head shim. Me and a buddy switched last ride for a bit and I jumped back on a pro, I would rather ride my viper any day now that I have every thing dialled in. We do lots of steep and deep tree riding and I have no complaints. The boost it guys have been awesome to work with and are always happy to answer any questions, my sled started as a mtx 153 and I stretched it to a 174 3" with a racers edge t motion rear skid, it's a beast and I love it
New build advice
- Thread starter DSpot
- Start date
Try one if you can and take it in the trees.. If your set on boost and want reliability and put lots of miles on and keep your sleds for a few years I think theres only one choice.. Does the viper feel as light and nimble as the doos or pros no, but I'll tell ya the viper handles so much better than the nytro and apex.. My nytro worked awesome 18 lbs boost 7000km gas and go but took alot of cake to get it there though.. My viper is rockin at 8-10 lbs boost, 3" track , baker arm and some skis
FYI - MCX have had altitude compensation since 2006 on their kit's, strange you didn't know that.
Sent from my Sanwa M12
Pro-Am Chris
Supporting Vendors
Boost-It has altitude compensation on their kits too.
Rotax_Kid
Active VIP Member
I'm not sure if they do or not, but a few years ago a fella in our group rented a machine from these guys in Revy..
Snowmobiles - Full SpeedFull Speed
He was a very nice guy and at the time had a low boost Nytro that he also rented out that he didn't list. Maybe he has a Viper now? Might be worth a shot.
Good Luck
Snowmobiles - Full SpeedFull Speed
He was a very nice guy and at the time had a low boost Nytro that he also rented out that he didn't list. Maybe he has a Viper now? Might be worth a shot.
Good Luck
Lund
Active VIP Member
On my Nytro i have a head shim and i run straight 91 up to 14lbs boost. Then i mix 25% c12 up to 18lbs boost. Been that way since new and its a 2010, never had a problem.
90% of the time i have the boost set at 16lbs which yields about 245hp. 12lbs will yield about 220hp, nice ponies for regular 91oct. In the long run the head shim saves alot on fuel cost, c12 is not cheap.
Im around the 265hp at 12lbs without the head shim that's why I run 50/50
sheldon89g
Member
How do you know your at the 265hp mark at 12lbs? Also do you have head studs on your viper?
Lund
Active VIP Member
The Genesis 1049 combined with the Garret GT2860rs turbo's set up and the extra larger injector's and inner cooler will produce approx. 7hp/1lb of boost.
The Garrett GT2860 is the most commonly used turbo on the Nytro by most builder's and one of the most efficient out there.
A stock Nytro has 135hp......now do the basic math.
The Garrett GT2860 is the most commonly used turbo on the Nytro by most builder's and one of the most efficient out there.
A stock Nytro has 135hp......now do the basic math.
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Lund
Active VIP Member
I'm also wondering the same, how do you know??
The Genesis in the Viper is no more powerful then the one in the Nytro, so how do you get 265hp out of 12lbs boost??????
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no headshim, just ARP studs and stock headgasket
Lund
Active VIP Member
Yup, not using a head shim will give his engine more combustion pressures. Thus the reason he has to use a mix or she will blow up.
Now do you really believe the extra combustion pressure will increase the HP that much????
This means 10.8hp/1lb boost......i don't think so. It will be closer to 1hp 2max per lb. But with a limitation on boost.
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I have played with this in automotive applications and the added compression makes a big difference in power output per PSI of boost....I would still drop the compression just to get away from having to use race fuel.....I don't know if Boost-it plays with the cam timing, on my Nytro that made quite a difference also
sheldon89g
Member
Ya that only works out to 219hp at 12 lbs of boost...
sheldon89g
Member
that only works out to 219hp at 12 lbs of boost...
Lund
Active VIP Member
Having the higher compression will do very little to the overall HP output of the engine, what it will do though is improve the low and mid range throttle response, thus what certain setup like Boost-it and couple of others are known for. Great for tree riding and general sledding.
I doubt that the engine see's an extra 2hp/1lb from using no head shim. Maybe 1hp/1lb of boost extra. So max output would be closer to 230-240hp with a mix all the time. While a head shimmed unit with same 12lb boost would be closer to 220hp on just premium.
Correct
bigfish
Active VIP Member
its not all about simple numbers,its about the whole system & how it works together,i dont know what the hp of the boost it kit is.my guess is about 240-250hp at 12-14lbs boost,higher compression makes more power & tork lower in the boost range,but as boost climbs the power gap decreases, but the higher comp engine will still make more power.heres a little info on comp ratios & boost.
Running on the same turbo back to back)If you’re running a 9.0:1 compression ratio @ 1 bar you’ll achieve an effective compression ratio of 18:1
If you’re running a 7.5:1 static compression ratio and 1 bar of boost you achieve an effective compression ratio of 15:1.
For the 7.5:1 to reach the same effective compression ratio you need to run .4bar or 5psi more boost. Combined with the fact that you have less “grunt” outside the boost threshold. Less grunt/torque means your engine produces LESS of a bang when the combustion mixture ignites, along with a slower burn due to a less compressed cooler mixture.
So in a nutshell – if you’re running 2.0 bar of boost on a 7.5:1 static ratio your achieving an effective compression ratio of 22.5:1 if you run the same setup with 9.0:1 static ratio you get the same effective compression ratio but with only 1.5 bar of boost and much better drivability outside of the boost threshold and a better spool due as a result.
Of Course, if the compression ratio is too high then the adiabatic effect will cause the mixture to auto ignite – so there is a line to be drawn obviously.
When building turbo engines static compression ratio is actually a bit of a clumsy way of measuring what’s going on because your measuring the C/R at atmospheric pressure not the desired. With that said, a higher C/R engine will produce more power off boost and subsequently spool your turbo slightly faster. You need to aim for a power goal (whatever that is) and spec your turbo setup accordingly to produce the required air at a reasonable pressure & temperature.
if you want a good read on the subject & can understand it lots of good info.
Xcceleration
Running on the same turbo back to back)If you’re running a 9.0:1 compression ratio @ 1 bar you’ll achieve an effective compression ratio of 18:1
If you’re running a 7.5:1 static compression ratio and 1 bar of boost you achieve an effective compression ratio of 15:1.
For the 7.5:1 to reach the same effective compression ratio you need to run .4bar or 5psi more boost. Combined with the fact that you have less “grunt” outside the boost threshold. Less grunt/torque means your engine produces LESS of a bang when the combustion mixture ignites, along with a slower burn due to a less compressed cooler mixture.
So in a nutshell – if you’re running 2.0 bar of boost on a 7.5:1 static ratio your achieving an effective compression ratio of 22.5:1 if you run the same setup with 9.0:1 static ratio you get the same effective compression ratio but with only 1.5 bar of boost and much better drivability outside of the boost threshold and a better spool due as a result.
Of Course, if the compression ratio is too high then the adiabatic effect will cause the mixture to auto ignite – so there is a line to be drawn obviously.
When building turbo engines static compression ratio is actually a bit of a clumsy way of measuring what’s going on because your measuring the C/R at atmospheric pressure not the desired. With that said, a higher C/R engine will produce more power off boost and subsequently spool your turbo slightly faster. You need to aim for a power goal (whatever that is) and spec your turbo setup accordingly to produce the required air at a reasonable pressure & temperature.
if you want a good read on the subject & can understand it lots of good info.
Xcceleration
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