New build advice

[Clode]

my Nytro is a good example of HP per Psi,

I changed the turbo and nothing else, at the same 12PSI I gained 3-350 RPM, turbo is now much more efficient and the heat and back pressure the engine sees is less yet I am making more power,

I added weight to get the RPM back in line and then added a WTA on its own closed loop system

I gained another 200 RPM at 12 psi, and the AFR stays rock solid now since the charge air temp is very constant, added more weight to clutch to keep RPM under control,

I thurned the boost to 14PSI (running 91 pump gas) and now I run my Dalton Dat/1 almost fully loaded, 47 helix, purple secondary, I can't remeber the primary spring color off hand.....this is at 2400ft....you don't need big boost to make good power, just an efficient system

 

[bigfish]

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

no cam timing just stock motor,neil designed this system for the best all around performace,not just to make a high hp # this kit does everything well from throttle responce to climbing.it will climb every chute in revy at 14lbs & is more power than most will ever want.

 

[Lund]

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

I agree 100% with this post....good post.

 

[Remmy]

You can do all the math you like, but clutching doesn't lie. As explained above at 12 lbs these sleds pull same clutching as an mcx 310 kit.

It's not an apples to apples comparison since the Vipers are geared lower than the Nytros, My 240 OFT kit also needs heavier weights on my viper relative to the same setup in the Nytro.

 

[sheldon89g]

no cam timing just stock motor,neil designed this system for the best all around performace,not just to make a high hp # this kit does everything well from throttle responce to climbing.it will climb every chute in revy at 14lbs & is more power than most will ever want.

what kind of fuel mixture are you running at 14 psi of boost out of your viper and do you have head studs on your sled to run that high of boost?

 

[bigfish]

what kind of fuel mixture are you running at 14 psi of boost out of your viper and do you have head studs on your sled to run that high of boost?

i run about 60-40 race to 91 at 14lbs 50-50 at 12lbs i dont go any higher & wouldnt without head studs.boost it guys put thousands of km on the vipers last year & they only lost 2 headgaskets both sleds running around 16lbs.
i run 12lbs most of the time & it even runs great at 6lbs on strait 91.

 

[sheldon89g]

i run about 60-40 race to 91 at 14lbs 50-50 at 12lbs i dont go any higher & wouldnt without head studs.boost it guys put thousands of km on the vipers last year & they only lost 2 headgaskets both sleds running around 16lbs.
i run 12lbs most of the time & it even runs great at 6lbs on strait 91.

what kind of race fuel do you use (c111)? what kind of boost can you run at lower elevations, say (2000-3000 ft)?

 

[bigfish]

what kind of race fuel do you use (c111)? what kind of boost can you run at lower elevations, say (2000-3000 ft)?

i run vp 110 think it replaced c111,i wouldnt run over 10lbs at that elevation with 50/50 race 91oct,give neil or tj a call at the shop,they are great to talk to & can give you a better idea.pretty sure they run vp 110 as well + the sell it too.if you plan on lots of miles at 2-3000 elev i would recommend a head shim though just on cost of race,if you are doing lots of miles.