AFTERMARKET PIPES FOR TURBOS

[mountainhorse]

Anthony... didn't you work out octane (too high) levels After you installed the OVS/SLP pipe? ....didn't you add the wrap and run Jacks new "turbo flash" after the install as well?

Did you try it again after the wrap/octane-adjustment on the stock pipe?

Just trying to figure out if we have a base-line comparison OVS-to-Stock pipes?

 

[Anthony Oberti]

Well.....yes, I did change my octane levels and that improved it significantly. I also did have some others goodies on it as well. However, I know for a fact the bottom end was much improved this year......who knows exactly from what as I changed alot....including the head. I can say this; last spring I rode back to back pump gass 800's, one with the stock pipe and one with the OVS/SLP pipe. The one with the pipe pulled much ahrder on the bottom and mid range than the stock pipe. Everyone that rode the two agreed on that.

 

[mngoat]

Have to agree with Oberti about the ovs/slp pipe. Much better low/midrange pull after swap. No other changes where made at the time. Just the swapping of the y-pipe and pipe from stock to OVS/SLP and pull the rope. Rode the sled stock for a bit then swapped out stuff and did the same pulls with new pipe setup, same pulls same riding place just the time that it takes to swap it out was the only difference. There was a definite seat of the pants difference. This was an 2008 dragon 800 with OVS garrett setup.

 

[mountainhorse]

AO and MnGoat..

Thanks for the feedback on your installs...

Kind of reinforces my belief that an exhaust, specifically designed with a turbo in mind can make a difference... And this is the "first stab" at a turbo pipe... wait till the engineering and testing have more time to come around.

Vohk has been working with speedworks on the AC Turbo exhausts for a while... In a couple of more years, I expect that the Turbos on the 2-stroke sleds will be much more evolved as a system than they are currently.... Pipes designed to do the job will be a big part of that evolution IMO.

 

[whittaker727]

Which is exactly the reason why, often a free flowing muffler will actually reduce power of a naturally aspirated 2 stroke if the muffler does not work with the design of the exhaust pipe as a "system".)

Not exactly true. How the pipe flows and reacts to back pressure is all part of the pipe design not mufflers/silencers. This is why a two stroke turbo runs fine straight piped just as a mx bike runs no different with blown out packing in the silencer. The only function of that silencer is exactly that, quiet or silence the exhaust. Two stroke pipes are all about volume (area that is) and tuned length.

 

[PMSPOLARIS]

BIG BOOST TURBO by MTNTK

I'm getting ready to start my new build this summer and had a question I can't seem to find an answer to. Has anyone used an SLP or any other brand single pipe for their turbo build, and if so any positve gains or other issues? I have seen for the cats that there are turbo pipes available, just haven't seen anything for the Poo.

You guys should really look into the new kit from Mountain Tek (MTNTK) the big boost turbo is clean and you can take the turbo off your sledd no welding or cutting and return it back to stock for under $125 in parts.
check them out on our website www.pmspolaris.com

 

[Pure Logic Tuning]

OVS does have a turbo pipe and y-pipe for the 800. This pipe is a SLP blank that has been modified in length and stinger size to optimize the torque and hp by changing the operating rpm and torque curve to match the turbo and turbine housing that OVS uses on there turbo kits. If you run the same size turbo and turbine housing you also can benifit from this pipe. This pipe also utilizes compression springs instead of exhaust spring that break constantly.
The pipe is thinner and recommended to be wraped to stop engine harmonics from causing pipe breakage. This pipe will not last like the thicker stock pipe but does perform alot better so it is up to the customer if he wants the extra performance. The pipe on Brad Story's sled is a OVS pipe that is wrapped.

 

[mountainhorse]

whittaker727: Not exactly true. How the pipe flows and reacts to back pressure is all part of the pipe design not mufflers/silencers.

Jason...I know where you are coming from and I used to have the same impression. Until the pressure in the pipe goes to atmospheric... the muffler or turbo is still part of the exhaust pipe and affects the back-pressure and effective design of the stinger and pipe overall. The 2010 Polaris factory 800 updates show that 2 stroke exhausts ARE sensitive to back-pressure.

If you burn out the packing in a MX bike... it still has the same pipe size... just no way to absorb the resonant "noise" in the exhaust.... Look at any good slip on... they come with different "chokes" for the muffler... that Definitely changes the way the engine runs... just like changing stinger size does.

I see many of the turbo designers going to a very large short pipe directly out the side of the sled... this brings the exhaust pressure very close to atmospheric directly after the turbine. This makes it easier to tune the turbo package as you are removing one variable in the system... Will this run better than a muffler in the system... not necessarily... but as presented above, there really has not been much research/design/testing/refining of tuned exhausts for the 2 stroke turbos. When there is, IMO, there will be improvements in flexibility, reliably, throttle response, lower octane requirements for a given boost level and probably better fuel economy.

The turbo pipes that are out there now are a step in the right direction, but as VOHK suggests above, there is a lot more to learn and a whole different set of requirements for 2 stroke turbo exhausts. The WAY we think of 2 stroke turbo tuned exhausts is changing, but, IMO, with the direction of the EPA, I doubt that there will be any big money poured onto this engineering challenge. In fact, I don't know of many applications of turbos to 2 strokes outside of the sledding world... You just wont find FMF/Pro-Circuit kind of money poured onto the issue, so development is going to be slow, IMO.

 

[whittaker727]

If you burn out the packing in a MX bike... it still has the same pipe size... just no way to absorb the resonant "noise" in the exhaust.... Look at any good slip on... they come with different "chokes" for the muffler... that Definitely changes the way the engine runs... just like changing stinger size does.

"Slip on" silencers are usually for street bike (4 stroke) application and yes, in that case, back pressure and tuned length are a huge part of the equation unless you are talking monster hp like in a top fuel car. But, we're not. Like you said, the silencer or muffler on a two stroke is a way to make a tuned two stroke pipe quieter, but if it were part of the whole system tuned for performance, why doesn't FMF or ProCircut require a whole system purchase instead of just offering pipes or silencers? I agree about the EPA and other govt. agencies restricting noise and air emissions enough that a big dollar company like FMF will not get involved.

 

[mountainhorse]

Pure Logic Tuning: The pipe is thinner and recommended to be wraped to stop engine harmonics from causing pipe breakage.

Travis,

Is the pipe breakage issue caused, in your opinion, by simple resonant harmonics or the huge pressure spike created by the reversion wave ramming into the boost pushing out of the exhaust before the piston actually closes of the transfer & exhast ports??

My understanding is that the reversion wave is trying to stuff the exhaust/fuel back into the cylinder (port closing) but hitting the charge pressure generated by the turbo.

The Description that I hear from most people is that the pipes are splitting or "blowing out" not simply cracking. Although I have seen plenty of turbo pipes that have simply cracked at a weld... much of which could have been helped by normalizing the weld line. Radical, rapid temp changes in the pipe mixed with water/snow spray splashed thru venting on the hoods and hitting the pipes places huge stress loads on the pipes.

I have seen signs of precip. hardening of a weld boundary in much of the custom pipe fabrication...not much of an issue in the pressure levels in a Nat Aspirated pipe...but the turbo systems have higher pressure levels and larger pressure spikes. A bit more work after the welding is done can go a long way, IMO.

From my understanding, the primary function of wrapping a 2 stroke pipe is to retain heat IN the pipe for more effective exhaust operation. Is this true?

 

[mountainhorse]

Jason,

Good discussion here...

Good catch on the slip ons/chokes... you are correct... 4 stroke...my bad... dirt season and all .

"Slip on" silencers are usually for street bike (4 stroke) application and yes, in that case, back pressure and tuned length are a huge part of the equation unless you are talking monster hp like in a top fuel car. But, we're not. Like you said, the silencer or muffler on a two stroke is a way to make a tuned two stroke pipe quieter, but if it were part of the whole system tuned for performance, why doesn't FMF or ProCircut require a whole system purchase instead of just offering pipes or silencers? I agree about the EPA and other govt. agencies restricting noise and air emissions enough that a big dollar company like FMF will not get involved.

Aftermarket silencers on 2-stroke mx bikes are NOT part of a whole system... Most are made to reduce weight, add bling, or give the bike a different exhaust note. When the MX aftermarket offers a pipe, they are working within the back-pressures of the existing silencers OR they do make full race exhausts that are sold only as a whole pipe/silencer combo.

From FMF's website:

Taking the proven success of the Powercore 2, FMF created the Powercore 2 Shorty, with a shorter inner core length and aluminum canister. This design results in a finely tuned bolt on performance silencer that maximizes bottom and mid rpm power. An excellent choice for tight tracks and supercross track applications.

Here they talk about the tuning effects on powerband by using/changing the character of the silencer.

I wasn't saying that the reason for lack of money being put into TURBO pipe development was the EPA or other Govt agency being involved in aftermarket exhausts... they are not in regulating aftermarket 2-stroke snowmobile exhausts.... yet.... if they were, CPI, SLP, BMP, Speedwerx and others would have a huge hole in their incomes.

My point with the EPA is that 2 stroke turbo systems will not be developed by "BIG" mfgs with large R&D budgests, IMO, because there is no way for Production, Consumer offerings from OEM's (that DO need to meet pollution standards from the EPA & MOE and others)to meet global pollution requirements...

The noise is not a problem that can't be dealt with... but that is a WHOLE DIFFERENT discussion that has been beaten to death in the other forums here.

Large 2 stroke tuned-pipe mfgs, won't be researching/designing/making "turbo pipes" because this is not at all part of their customer base... and will not be.

SLP has been conspicuously out of developing any kind of turbo exhaust to date... this may change as they probably cant afford to pass up the profit.

From what I gather... the "SLP/OVS" offering is their customization of unfinished SLP non-turbo pipe sheet-metal stampings, modifying them to their standards and welding them up... Not really an SLP pipe anymore and certainly not something that SLP put any money into designing.

Big thanks to OVS and the crew for opening the door and pushing the limits a bit though!!

A couple of examples on the muffler/stinger/pipe relationship...

Try to get a NON race SLP twin set to run with "stinger mufflers"
Try to get a RACE SLP twin set to run well with the non-race muffler.

Try to get the 2010 Dragon to run well with the stock 2008/09 muffler. (if you could get it to fit the new bracket)

You always see 2 stroke muffler companies claiming HP increase with their muffler or the HP loss from using a competitors...most is BS... but some of it is not..

My point is, that if ANY back-pressure (or lack thereof) is created by the muffler (aka "can") it WILL affect the performance characteristics of the system.

I guess this is where we will need to agree to disagree...

I hope to meet up with you next season with EricW or Allen and do some riding... I got "skunked" for snow in N. Idaho this Feb/March/April...looking fwd to next season.

 

[Spaarky]

I am a bit of a negative nelly when it comes to specialty turbo pipes.... I dont want to distract from what is a good discussion. I have not seen anyone give any good reasons as to why it would work... a principal or theory... just that it works. But, why?

Do I think it is possible to make gains? Yes, I just dont think it has been explored enough yet.

Airflow is what helps a T-sled the most...

The guys with the OVS pipe... is it possible that the aftermarket pipe fits better and with the added spring/connections, it is just sealing up better. You would be amazed how much difference the smallest air leak plays in spool up.

I have a feeling the Y-pipe is playing into it, alot more than the pipe. I have seen some interesting theories in Y-pipe design on 2-stroke motors w/turbos.

I have seen pipes put on a sled w/turbo that have no reason to be there(except for fit)... run just as good as the pipe that is meant for the motor. I am talking a pipe from a different brand/size motor put on a sled and tested due to the fit. Then the pipe meant for the motor put on and tested.

 

[Anthony Oberti]

Here she is......OVS/SLP turbo pipe.

 

[mountainhorse]

Airflow ...yes..

Wave mangement in both directions, yes... but not explored much and when it is, it seems to be evaluted in terms of Naturally aspirated pipe properties... As Erik (Vohk) said... this is where a shift in the way we look at tuned exhausts makes a difference. Plain and simple, the turbo 2-strokes have different needs and properties inside of the pipe.

As I said earlier... I'd like to see some experimentation with a twin-scroll/twin pipe install... not having conflicting pressure signals in the pipe Might help in this rapid evolution of turbo 2-stroke snowmobiles...(might not too )

Do I think it is possible to make gains? Yes, I just dont think it has been explored enough yet.

Agreed... outside of Vohks work, I have not seen any real R&D in this aspect of turbo design... not just making a pipe that can withstand the pressure spikes...but maybe one that does not have them in the first place.

I have not seen anyone give any good reasons as to why it would work... a principal or theory... just that it works. But, why?

Hopefully this gets explored/explained as builders and users learn more about turbo engine/exhaust dynamics & design.

 

[RMK935VA]

MH, I am running Jack's custom single ring pistons. I don't know anything about a "custom map" but those guys at Carl's don't tell me everything that they do to my sled so maybe I have it. I let them worry about the highly technical stuff.

I have a hard time believing that an aftermarket pipe could make enough of a difference that you would see a discernible difference in power and/or would be able to use a different amount of race fuel at a certain boost. If it can be proven to me that I am wrong, I might purchase an aftermarket pipe but I am pretty damn sure that it can't be done.

 

[Anthony Oberti]

Call up OVS and call up Jack. They both agree that the SLP/OVS pipe is faster than the stock pipe as they have both compared the two. I have heard the difference of about 1-2lbs of boost.....ie-14lbs stock pipe=12lbs with OVS pipe. It was a good investment as far as I am concerned. The thing about running less race fuel had nothing to do with the pipe.

 

[Anthony Oberti]

For what it is worth, I may have my pipe for sale. I wrecked the whole sled and may part it out. Pipe is still fine....

 

[whittaker727]

For what it is worth, I may have my pipe for sale. I wrecked the whole sled and may part it out. Pipe is still fine....

Bummer. Let me know. At least now, you don't have to be on the fence about buying a new sled or not.

 

[jayjay]

Outlaw,

I have run the ovs/slp pipe for two years. First year no problems but the second year it would crack every third ride or so. So I kept the slp y pipe and the spring bolt type clamps with the stock pipe. I could not tell a diffence. I do remember a noticeable difference when I put the ovs/slp pipe on. So I do believe you are correct about the y pipe and connections.

 

[Bikeman Performance Plus]

Just because it hasnt been brought up I figured I would chime in. We do make and have sold numerous turbo pipes for the dragon 800's. Our pipe stampings are actually a tiny bit thicker than stock, so no worrying about blowing them out!