What boost levels do you run?

[Wheel House Motorsports]

motor and fuel are NOT an issue. again, Im just gonna start at 10..then turn it up.. Im clutched to around 14 #... so who knows where it will end up.

I realized that 10# this year is gonna be a LOT more powerful as last season with all my design inefficiencies last season. Who knows.. it might stick at 10.. might get jacked up even further.

 

[M5-]

Boost isn't the be all end all as far as power goes. The question IMO should read How many Lbs of air is your turbo pumping out at xx lbs boost? A larger turbo will make more power than a smaller one at the same boost level. You can run a GT25 at 18 lbs but its only efficient to about 12-14 lbs, so in theory running a GT2554 at 18 lbs you could get your a$$ handed to you by a guy running 14 lbs on a GT2871. When you get down to it the boost level is one of the last factors that decide overall performance and power yet its all anybody seems to talk about.

Just my $0.02 worth and some food for thought.


M5

 

[Wheel House Motorsports]

great post.. And That I am very aware of how it all comes together, last year, my poorly setup header with a non intercooled setup just wasnt that fast, even at 10#.. It smoked all the NA sleds I ride with, but wasnt that crazy fast. this year, its getting redesigned iwth the right components to make a LOT more power on the same boost, I would bet my new system will make 20% more power per # of boost just due to overall efficiency. as for turbo size I didnt go huge as I dont care for a huge HP monster, but a good flowing guy that can provide plenty of air at the boost levels I need.

I know there are millions of other variables that contribute to total HP.. again, more of a curiosity then anything. charge system design, intercooler efficeincy, airbox flow, header design, downpipe setup.. They all play a role, and I try and set mine up the best for optimal peak HP while still retaining solid mid/bottom end.

Im betting an impulse race kit at 17/18# would work over most anything else at similar boost levels due to the large components designed to make BIG power.

 

[mtn-doo]

Hey Nick, good to see you're about ready! I'm getting sooooo stoked! My tree rider is a different set-up, but will be loads of fun! I am also runnung a 2871, huge 3" charge tube, cooled, burning c-12. A super light, 418lb sled with 230hp, geared down for explosive responce in the trees will be a riot!
"Nuthin but Wood" !!!

 

[Thunderguy BOOSTED]

Hey Nick, good to see you're about ready! I'm getting sooooo stoked! My tree rider is a different set-up, but will be loads of fun! I am also runnung a 2871, huge 3" charge tube, cooled, burning c-12. A super light, 418lb sled with 230hp, geared down for explosive responce in the trees will be a riot!
"Nuthin but Wood" !!!

Hey bro that sounds like a sled and a half? got pics???????????

 

[acforlife]

14-17#'s is max usable climbing horsepower. I usually run 15#'s. The people that claim they run over 20#'s of boost are in and out of throttle so much that it only averages about 15#'s. You can climb anything you want as long as the front stays down on 15#'s of boost. Just my .02. Edit...This is on a properly setup sled with 12.0afr's, good clutching, and good all around tuning.

there is a apex in utah for sale for 13000$ runs 22lbs all day runs on propane everything custom bov is set at 30psi but its supposed to beable to run 30 but currently se at 22

 

[Wheel House Motorsports]

well, seeing as this got brought up, figured i would chim in what i have been running mine at lately...

Started workin it up... 15/16 is a LOT of fun.. at that point thought with the stock doo skid it becomes somewhat of a pain to control as it just rears up and over if you whack it without momentum. now in the spring snow i have been running 12-14 depending on how mushy the snow is.. really gets around like that, now if i could only seal up my header flanges and make real power.

 

[mattymac]

I run my impulse apex @ 12lbs

its plenty IMO, ran as much as 18 but it gets less responsive in and out of the throttle durring low speeds, seen as high as 85-90 mph track speeds with it.

@ 12 on pump its way more fun to ride due to the responsiveness of pump fuel and lighter clutching 65mph track speeds climbing under hard loads, better control, seems to work better for me day in and day out.

 

[spacehog21]

I run a Doo 1200 and started out with 20-22 psi
I currently have it at 15 #

smooth, even power at full throttle

at higher boost levels I tend to be in and out of the throttle

Big, long, open pulls is when high boost comes in handy

There is a time and place for both mid and high boost levels in every riding season. Overbuilding the boost system and engine is wise. Then all it takes is a few clicks on the knob.

 

[christopher]

Now that I have a supercharger on the sled, I can't imagine ever going back to NO boost.

And it won't surprise me at all that I begin Boosting the Boost as time goes by.

Pushing 8lbs now, on my way to 10lbs.

 

[hotmail]

I run 17 most of the time. When I race or it's really deep it's up to 20. There are certainly some chutes I have a hard time climbimg in deep snow at 17 and that's when I turn it up. I wouldn't run more then 16 or so if I didn't have a suspension to keep the front end down regardless of snow condiitons. "Useable" power or boost has everything to do with suspension, not some arbitrary boost number.

are you using 9:1 pistons

 

[Matte Murder]

I am trying to buy a T Nytro now. On an MCXpress 270 kit does it have adjustable boost? How much boost does it take on that kit with a basically stock engine to make what they call 270hp?

 

[up-high]

I think 16/17 # should be around 270hp. I don't think MCX comes with a boost controller(my 310 kit didn't), but you can install a Hallman ProX for about $100..

 

[roughrider99]

My dads mcx 270 runs 16lbs

 

[smwizzz]

150 #

Good reading guys.. I definately appreciate the info.

I am a firm beleiver in the slightly less boost, but being able to stay WOT all the time is a lot more rideable then huge power just on/off the throttle all the time. I will admit im not a HUGE hillclimber, I like my steep and deep hills, but I prefer shorter and super steep, so more techincal keeping the sled from flipping stuff, maybe some trees in the top to dance with. This is also nice, so if you wreck, you dont cartwheel all the way down the mountain!!

as far as skid and track, Methinks thats gonna be my limiting factor, althought I am upgrading tracks its not that much, gonna be running a 162x16x2ish paddles, it was a 2.25 or a 2.5 cut down (not sure, im getting it for free) this should be a decent amount of track for the sled, but im only running the stock DOO skid, and I like to have it setup to boondock nicely, which isnt necasarily the best for big steep stuff. I am working on building some little coupling blocks for it to help keep it from being out of control...

I also know my turbo system being a homebrew setup is nearly as efficient as the big name systems, BUT, my setup this year with the midmount header and 16g turbo should spool like a SOB at those levels, it already came on real quick with my crap header I built last time, so this one should be a lot nice for on/off power delivery. also tuning propane is pretty simple and should be less finickey on angles the the gas carb setup. either way. thanks all for the input. My wastegate starts at 10#.. so i guess just get a boost controller and start having fun!!

Now I guess its time to start looking at better clutching!!
My fuel system will be able to handle whatever I want to throw at it.. got good drivetrain drievers, big enought turbo. I can turn it up beyond IMO I would be able to ride. I kinda forgot to mention Im a little smaller then most gents I see on t-yami's... Im 150# in street clothes, that definately makes a big difference in what it takes ot push me around.

Ya, hear ya on the weight thing. I hated my Nytro for the first season. I have learned to ride it since then and now am a very large fan. I'm a shade lighter than you at 135 lbs. I run an M-10 so the hills don't bother the front as much as some suspensions. I have been running a 162 x 16 x 2 1/2 track. I am going to run a 3 inch lug this year instead and am going to try a skinz front end. Last year I ran 15 - 16 lbs boost and found that when I was running 10 -12 the biggest difference was acceleration. I won't say that I could climb everything I could climb at 15 lbs when I was running 12 but the difference was not crazy. The big difference is when I mash the throttle the front end comes up and the sled launches which attributes to fewer stick jobs. I have always been a power hound and find the power is my saviour. In tight spots (technical) Power has been known to pull my sorry arse around a big tree well or through it on occasion... sometimes it has blasted me back up when the down side was a very poor option and has carried me to the nosebleed seats when no one else could get there. I have some buds running the 18's and 20's. Once you reach these levels you need some serious traction and suspension and are looking at chutes and hills that only mountain goats and mountain climbers climb. Personally I can't afford to wreck sleds for something to do so I keep it on the insane side.... not the stupid side!!! Most mountain guys have some $$$ but even the guys with the big $$$ don't go places they will probably wreck a sled. They will push it to the areas one may wreck it but keep it within their limitations. Pow is cool but 15 lbs is lots for the most riders.

Keep smiling!!! Winter is coming!!!!

 

[smwizzz]

Boost

I am trying to buy a T Nytro now. On an MCXpress 270 kit does it have adjustable boost? How much boost does it take on that kit with a basically stock engine to make what they call 270hp?

One can use a simple number to achieve a close guestimation of HP. 10 Hp for one lb boost. This is just a number to get close. It will depend on engine size and what is done to the engine and fuel systems etc. Some kit claim 250 hp at 10 lbs, some claim 225 hp. An Apex 4 cyl will be slightly different than a 3 cyl Nytro. What is done to the engine is important as to what boost can be run. A stocker should be cautious about over 10 lbs. A head shim makes a big difference and some kits claim up to 17 or 18 lbs with the shim. Aftermarket engine work will definitely effect the boost levels. Compression ratio is the biggest factor, hence a head shim. I personally like the ability to adjust the boost levels. This may be simply due to fuel availability. If I run out and someone has some premium I can turn the dial down untill I can get some of the good stuff. Trail riding at 10 lbs on premium is a nice option. On systems that don't compensate for elevation (Atmospheric/barometric pressure) it is nice to be able to fine tune the preasures to what you want to run.

Just some random info. Hope it helps.

 

[smwizzz]

Agreed

Boost isn't the be all end all as far as power goes. The question IMO should read How many Lbs of air is your turbo pumping out at xx lbs boost? A larger turbo will make more power than a smaller one at the same boost level. You can run a GT25 at 18 lbs but its only efficient to about 12-14 lbs, so in theory running a GT2554 at 18 lbs you could get your a$$ handed to you by a guy running 14 lbs on a GT2871. When you get down to it the boost level is one of the last factors that decide overall performance and power yet its all anybody seems to talk about.

Just my $0.02 worth and some food for thought.


M5

You got it bud. One other thing to consider is if you are not going to run big boost and HP, the smaller turbo spools faster and is more responsive than the bigger one.


You also need fuel system upgrades for big power. The smaller systems need fewer fuel system mods. ie.: cheaper set up

 

[gunnerthesnowman]

You got it bud. One other thing to consider is if you are not going to run big boost and HP, the smaller turbo spools faster and is more responsive than the bigger one.


You also need fuel system upgrades for big power. The smaller systems need fewer fuel system mods. ie.: cheaper set up

This is not necessarily true , i run a 3076 turbo on my current apex set up and let me tell you it is a lot faster spooling and has way more throttle responce then my GT2871 turbo did on my old Alpine kit and yes 18lbs of boost with the 2871 is no comparision to 18lbs with the 3076.
You can run a big turbo , low boost and still have throttle responce ,all you need is a engine , turbo system and fuel system build to work together.

 

[Duke]

This is not necessarily true , i run a 3076 turbo on my current apex set up and let me tell you it is a lot faster spooling and has way more throttle responce then my GT2871 turbo did on my old Alpine kit and yes 18lbs of boost with the 2871 is no comparision to 18lbs with the 3076.
You can run a big turbo , low boost and still have throttle responce ,all you need is a engine , turbo system and fuel system build to work together.

Faster spooling because your running stock compression...
Mine is faster spooling because it is well fueled thanks to Boost-It.

IMO, proper fueling has the most to do with throttle response no matter what your compression ratio and turbo size is. Tuning on our Alpine set ups is 100X better than when you had one. Your sled never did run to its full potential IMO, my old one either. If your old set up had Boost-It, it would rip your arms off too.

 

[gunnerthesnowman]

Faster spooling because your running stock compression...
Mine is faster spooling because it is well fueled thanks to Boost-It.

IMO, proper fueling has the most to do with throttle response no matter what your compression ratio and turbo size is. Tuning on our Alpine set ups is 100X better than when you had one. Your sled never did run to its full potential IMO, my old one either. If your old set up had Boost-It, it would rip your arms off too.

Compression ratio has alot to do with the engine torque curve

IMO,you get the best of both worlds with running a high compression ratio , you can run a bigger turbo with less engine back pressure and still have throttle response like its a stock sled with huge amounts of torque

The torque curve of a properly fueled and timed motor with a high compression ratio at 15lbs of boost will look a lot different then the torque curve of a properly fueled motor with low compression ratio at 15lbs of boost.