Any Part 103 with >650 pound MTOW?
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Aesquire
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TFF
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I would be looking at the Legal Eagle XL and if it needs any real mods. I don’t think there is a difference between it and the two seat spar, so it should be plenty strong. If built to the T, there is a little weight left to change up. I doubt there is any strength problem, but you probably start getting into legal stall speed problems, not flying problems. If you are wanting to pack stuff around, you are just not going to be able to and be in the spirit of the law with any 103.
jedi
Well-Known Member
Stall speed specified in FAR 103 is for the FAA 170 pound standard pilot. A 275 pound pilot will stall at a higher speed and still be legal per FAR 103 and AC 103-7..
I would be looking at the Legal Eagle XL and if it needs any real mods. I don’t think there is a difference between it and the two seat spar, so it should be plenty strong. "
The spars on the Double Eagle are engineered for 900# gross weight, the XL for 575# Two different animals
The spars on the Double Eagle are engineered for 900# gross weight, the XL for 575# Two different animals
TFF
Well-Known Member
I helped build a XL and it’s about as strong as a full size Cub. The rib template for both 1 and 2 seat are superimposed together. Although different, pretty much shows the same spar cross section. Change the aluminum wing mount straps to 4130 would be an upgrade. We had Carlson struts. Tail in 4130 probably eats too much weight, but that’s really the only part that’s not as tough as a Cub.
Armilite
Well-Known Member
Wings of Freedom, Phoenix 103 has a 650 lb MTOW. A T-Bird I has a 660 lb MTOW and can make Part 103 with a Rotax 277UL(65 lbs) or a Hirth F33(45 lbs with Electric Start), or an MZ34 (44 lbs), or a Simionini Mini 3(42 lbs Pull Start).
An Aerolite 103 has a 600 lb MTOW and with a Hirth F33(45 lbs with Electric Start) comes in at 235 lbs. I believe it uses .058" Wall Tubing on the Spars. So you could probably ask for upgraded Spars .065" for a 650/660 lbs MTOW. You have 19 lbs to Beef up the Airframe. My T-Bird I, has .065" Wall Spars.
The Aerolite 103 at 235 lbs + 30 lbs(Gas) + 275 lbs(You) = 540 lbs as a Part 103.
Using a Good Power to Weight Ratio, like 1 kw for each 10 kg, 540 lbs needs 33hp if you want good Flight Numbers. It will Fly with less hp. The vast majority of USA Part 103 used a 26hp/28hp Rotax 277UL. At a 660 lb, MTOW needs 40.1hp.
An Aerolite 103 has a 600 lb MTOW and with a Hirth F33(45 lbs with Electric Start) comes in at 235 lbs. I believe it uses .058" Wall Tubing on the Spars. So you could probably ask for upgraded Spars .065" for a 650/660 lbs MTOW. You have 19 lbs to Beef up the Airframe. My T-Bird I, has .065" Wall Spars.
The Aerolite 103 at 235 lbs + 30 lbs(Gas) + 275 lbs(You) = 540 lbs as a Part 103.
Using a Good Power to Weight Ratio, like 1 kw for each 10 kg, 540 lbs needs 33hp if you want good Flight Numbers. It will Fly with less hp. The vast majority of USA Part 103 used a 26hp/28hp Rotax 277UL. At a 660 lb, MTOW needs 40.1hp.
Protech Racing
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Nice chart. Where is it from? Are the power values lift off ,cruise , at what V etc?.
Thanks,MM
Thanks,MM
Armilite
Well-Known Member
===================
You should really Power your Plane for its MTOW! Most fall between 450 lbs (27.4hp needed) and 660 lbs (40.1hp needed). The chart was made using Excel and using the 1kw for 10 kg rule of thumb Power to Weight Ratio if you want Good Performance. The same Plane but with different Weight Pilot & Bags, Performance will vary. USA Average Pilot Weights fall between 180 lbs and 235 lbs. Most Part 103's Empty Weights fall in the 235lbs to 254lbs range.
Probably 80% of the Worlds Part 103 Ultralights Flew with a Rotax 277UL rated 26hp@6250rpm! They Cruised at 5250rpm = 20.3hp!
Your Power to Weight Ratio used, effects your Take Off Distance, your Climb Rate, and your Speed. Lighter People under the norm can get by using less hp. But People above the Norm, need more hp!
Just about any 2 Stroke 250+cc, can be upgraded to meet your hp needs with a Good Tuned Pipe. A Good Rule of thumb for 2 Strokes turning 6500rpm and using 11.5cr with a Proper Size Carb with a Good Designed Tuned Pipe it takes on Avg 7cc to make 1hp.
Some Common CC 2 Strokes:
250cc/7cc = 35.7hp@6500rpm.
268cc/7cc = 38.2hp@6500rpm.
368cc/7cc = 52.5hp@6500rpm.
436cc/7cc = 62.2hp@6500rpm.
496cc/7cc = 70.8hp@6500rpm.
A Simionini Victor 1 Super, a single-cylinder is 400cc using 9.5cr and is rated 54hp@6500rpm! 400cc/7cc= 57.1hp - 2hp for the lower 9.5CR = 55.1hp@6500rpm. Should have used the next bigger carb. About a Perfect Engine.
Tim Newport
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Armilite, where could I get a tuned pipe for a rotax 277? Thank you Tim
Armilite
Well-Known Member
==========================
As far as I know, Nobody today is making a Tuned Pipe for the Fan Cooled 277UL, 377UL, 447UL, 503UL, or the Water Cooled 462UL, 532UL, 582UL, 618UL. Rotax Rick makes one for his 670's. There is JAWS, SLP, The Crank Shop, FMF, etc., that make Tuned Pipes. There is a guy in Canada that makes Tuned Pipes for anything, but I forget his name at the moment. I know he makes them for Sled 277F.
There are at least 5-7 Tuned Pipe Builders that make Sled Tuned Pipes, but even they don't make any for these Older Sled Engines like the 277F, 377F, 440F. You might find one for the 503F, and the 521 LC, 580 LC, 617 LC, 670 LC, but most of them don't want anything to do with Airplanes. If you contact them, say it's for an Air Boat or Hover Craft. Custom made Tuned Pipes can Cost $450 to $700.
Material to make your own $25 or less from a Scrap Yard.
Tuned Pipe & Cone Software to make your own anywhere from Free to $40.
Tools needed: Basic Measuring Tool to Measure your Cylinder Exhaust Port, a Tig or Mig Welder, Construction Paper & Tape, Scissors. Once you have your desired Shape laid out in Paper you want, you take them DXF CAD Files to a Shop that has a CNC Laser or Water Jet to cut them out of Metal. A CNC Plasma Cutter will probably work also or a CNC Hobby Router. People have Hand Cut them out also. The same Machine Shop can Roll them pieces also, or Harbor Freight sells a cheap Metal Roller.
You also have the Option to Cut, Turn, Weld, a Sled Tuned Pipe. But you need to know what Engine and it hp@rpm and Exhaust Duration it was Designed for, and your desired Engines original hp@rpm and its Exhaust Duration. There is a Formula to use that you can make up a Chart of the common rpm used.
Like my Skidoo/Rotax 335 Single is rated 20hp@5500rpm with a 155 Duration. A Stock Skidoo 670 is rated 115.7@7750rpm and has a 180 Exhaust Duration. In the Chart I made, you go to Exhaust port Timing 180 and over to 7750rpm and you get a Number 39.5", then go to 155 and Pick what rpm you want to turn it, like say 6500rpm and you get a Number 40.5". So that Info Tells you to Add on 1.0" to the Lenght. The 335 used a Can Muffler that Bolted directly to the Cylinder. Ideally Exhaust should be Mounted with Springs. So make a 1.0" Wye Pipe with Loops for attaching with Springs.
You can choose to use whatever Max rpm you want, Rotax used 26hp@6250rpm, and 28hp@6400rpm, I would use 6500rpm!
You got (3) ways to estimate your Engines hp at rpm.
#1 The PLAN Formula and using BMEP.
Reciprocating Engine Formula Equations 4-Stroke | Engineers Edge
The following tables define equations for four stroke reciprocating engines.
www.engineersedge.com
#2 You have the Simple 7cc to make 1hp Rule. That's using 6500rpm, the proper Size Carb, using 11.5cr, with a Good Tuned Pipe. 268cc/7cc = 38.3hp!
#3 You have the Peak Flow/HP Calc. Most Sled Stock Tuned Pipes fall into the 93-95% VE range. The Calc only works with Whole Numbers.
268cc at 6500rpm at 93% VE = 38hp
268cc at 6500rpm at 94% VE = 39hp
268cc at 6500rpm at 93% VE = 39hp
Most people only know what hp the manufacture decided to use, not it's Max hp capability! Skidoo made some Engines in (3) different classes, like the Standard 335(20hp@5500rpm), 340 TNT(26hp@6500rpm), and 340 Blizzard(36hp), same basic Bore & Stroke they just used different rpm to rate them with different Carb Size used and different CR used. The Blizzards used a Tuned Pipe!
Free Tuned Pipe Ap. Exhaust Calc. The bottom Box is 2.0 for Wide Band. That is all the Info you need to Design a Tuned Pipe for your Engine. You need a Cone program to make Bends in the Tuned Pipe.
2 Stroke exhaust calculator - Apps on Google Play
A simple 3 stage two stroke exhaust calculator based on formulas of G.P. Blair from the book: The Design & Simulation of Two Strokes. You can also save and load the data by using the provided functions. Note: This coefficient Kh is called the horn coefficient, with typical values between one...
For Paid Software, I like this guy's Program, Pipe Designer. His Cone program is Free.
Pipe Designer | Ezin Hobeki
Armilite
Well-Known Member
The Tuned Pipe he makes for the Sled 277F. Neil, at info@npowerperformance.com makes them for the Sled 277F.
If Stock was 28hp@6400rpm and I would bet it was lower, companies like to round up hp numbers. For a Good Wide Band Tuned Pipe, I wouldn't go more than 40%. With Rotax's Exhaust, the 277UL Avg 2.8hp per +250rpm. 2.8/5= 0.56 hp per +50rpm. So going from 6400rpm to 6500rpm Gains you 1.12hp! 28hp + 1.12hp = 29.12hp at 6500rpm.
29hp + 40% = 40.6hp@6500rpm! The 7cc Rule says for 268.8cc@6500rpm = 38.4hp!
28hp + 40% = 39.2hp@6400rpm!
28hp + 35% = 37.8hp@6400rpm!
28hp + 30% = 36.4hp@6400rpm!
28hp + 25% = 35.0hp@6400rpm!
If Stock was 28hp@6400rpm and I would bet it was lower, companies like to round up hp numbers. For a Good Wide Band Tuned Pipe, I wouldn't go more than 40%. With Rotax's Exhaust, the 277UL Avg 2.8hp per +250rpm. 2.8/5= 0.56 hp per +50rpm. So going from 6400rpm to 6500rpm Gains you 1.12hp! 28hp + 1.12hp = 29.12hp at 6500rpm.
29hp + 40% = 40.6hp@6500rpm! The 7cc Rule says for 268.8cc@6500rpm = 38.4hp!
28hp + 40% = 39.2hp@6400rpm!
28hp + 35% = 37.8hp@6400rpm!
28hp + 30% = 36.4hp@6400rpm!
28hp + 25% = 35.0hp@6400rpm!
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n3puppy
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TIM,
You need to be careful what you ask for in getting a pipe.
Snowmobiles use a constant velocity transmission that allow the engine rpm to remain in a very narrow range while producing max hp.
The aviation equivalent is a fully in flight adjustable Prop.
Unfortunately very few ultralights fly with in flight adjustable props.
That makes any pipe designed to increase power for a snowmobile a rather poor choice.
Especially if chasing some arbitrary number like - I want a 40% pipe!! You will get a peaky un-flyable pipe for your aircraft.
Back in the day there was a group of guys that built aviation pipes for aviation motors in actual aircraft. Their company name says it all R&D Aerosports.
These guys understood the complete flight envelope from ground roll, full power takeoff, cruise, descent, and potential go around power on landing.
They produced what they thought was the most suitable 277 pipe for aviation use.
At peak - its output was 20% over factory (25.5 vs 30.5)
AND USED STOCK PORTING
Two things stand out about the pipe -
1) After a small initial jump around 5000 rpm, it maintained a very similar slope of power gain/rpm of the stock Rotax tuned exhaust system.
2) it also maintained the peak output of 30hp over a wide 250 rpm range before dropping.
While you can't tell them you need an aircraft pipe, you would be a lot better off handing them the desired numbers of the pipe you want. (R&D numbers)
You need to be careful what you ask for in getting a pipe.
Snowmobiles use a constant velocity transmission that allow the engine rpm to remain in a very narrow range while producing max hp.
The aviation equivalent is a fully in flight adjustable Prop.
Unfortunately very few ultralights fly with in flight adjustable props.
That makes any pipe designed to increase power for a snowmobile a rather poor choice.
Especially if chasing some arbitrary number like - I want a 40% pipe!! You will get a peaky un-flyable pipe for your aircraft.
Back in the day there was a group of guys that built aviation pipes for aviation motors in actual aircraft. Their company name says it all R&D Aerosports.
These guys understood the complete flight envelope from ground roll, full power takeoff, cruise, descent, and potential go around power on landing.
They produced what they thought was the most suitable 277 pipe for aviation use.
At peak - its output was 20% over factory (25.5 vs 30.5)
AND USED STOCK PORTING
Two things stand out about the pipe -
1) After a small initial jump around 5000 rpm, it maintained a very similar slope of power gain/rpm of the stock Rotax tuned exhaust system.
2) it also maintained the peak output of 30hp over a wide 250 rpm range before dropping.
While you can't tell them you need an aircraft pipe, you would be a lot better off handing them the desired numbers of the pipe you want. (R&D numbers)
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n3puppy
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- Jun 25, 2019
- Messages
- 192
By the way, anytime you see somebody quote 28hp at 6400 remember that it is already a 10% improvement over the original factory HP rating of 25.5 hp @ 6100 rpm. Rotax factory tuned exhausts got better over the years.
40hp is a 57% increase over original factory hp.
Be extremely cautious with any pipe builder who claims he can get these numbers without major porting changes. Its up to you if you want also pay for someone to port for a 57% increase.
29hp + 40% = 40.6hp@6500rpm!
28hp + 40% = 39.2hp@6400rpm!
28hp + 35% = 37.8hp@6400rpm
28hp + 30% = 36.4hp@6400rpm
Walk away from any pipe builder who will not put it in writing that you have a money back guarantee if your 277 engine will not dyno over 36hp on an INDEPENDENT dyno.
It is not hard to "Sway" dyno numbers high or low depending on who is paying for the work.
40hp is a 57% increase over original factory hp.
Be extremely cautious with any pipe builder who claims he can get these numbers without major porting changes. Its up to you if you want also pay for someone to port for a 57% increase.
29hp + 40% = 40.6hp@6500rpm!
28hp + 40% = 39.2hp@6400rpm!
28hp + 35% = 37.8hp@6400rpm
28hp + 30% = 36.4hp@6400rpm
Walk away from any pipe builder who will not put it in writing that you have a money back guarantee if your 277 engine will not dyno over 36hp on an INDEPENDENT dyno.
It is not hard to "Sway" dyno numbers high or low depending on who is paying for the work.
Tim Newport
New Member
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- Oct 3, 2019
- Messages
- 2
Armilite
Well-Known Member
Tim
READ, 2 Stroke Tuners Book by Gordon Jennings. One of two people who wrote the Formulas for Designing a 2 Stroke Tuned Pipe. Learn for yourself.
Some of these people clearly don't understand when they say stuff like "Snowmobiles use a constant velocity transmission that allows the engine rpm to remain in a very narrow range while producing max hp." has nothing to do with hp made at these different rpms. That's a Mechanical Connection between the Engine and the Track and controlled by the Throttle. The Clutch can be set up to engage at different rpm.
Just as making a statement "The aviation equivalent is a fully in-flight adjustable Prop. Unfortunately, very few ultralights fly with in-flight adjustable prop." Once again, has nothing to do with Engine hp made at different rpm. It does allow you to change the Pitch to get more Pulling or Pushing Force by changing the Pitch. 99.9% of all Ultralights and most Kitplanes, Homebuilts don't use an In-Flight Adjustable Prop either!
The only things that affect your Engines hp made, is the Bore & Stroke used & Carb CFM used & the CR used & rpm used, and a Tuned Pipe if you use one! Using any Muffler on any Engine Restricts hp made, but they do lower the Sound Signature it makes. If you look at the Stock 277UL it's rated 26hp@6250rpm but actually Dynoed by R&D at 25.4hp@6000rpm. So a good indication the Muffler is too Restrictive. The other one was rated 28hp@6400rpm. Nobody has posted a Dyno Print of one actually making that 28hp. Like I showed, there are (3) ways to figure your approximate hp made for our 6500rpm. These same armchair mechanics have no problem with a Polni 250 DS 244cc making 36hp, or any of these other Small CC Engines that use a tuned Pipe, but when it comes to these Rotax's and Hirth's that do not use a Tuned Pipe, it's suddenly unbelievable!
Rotax Ricks 670 Dynoed (92hp@6350rpm) using 669cc, and makes 138cfm/92hp = 1.5 Constant and Dials in at 92% VE. 669cc at 92% VE turned 6500rpm = 94hp! 669cc at 93% VE turned 6500rpm = 95hp!
669cc/7cc= 95.5hp@6500rpm. So that's a pretty darn close estimate I would say. A Stock 1993 670 Dynoned 115.7hp@7750rpm which Dials in at 94% VE. So a 277UL 268cc turned 6500rpm using 94% VE = 39hp.
268cc turned 6500rpm using 93% VE = 38hp. 268cc/7cc= 38.2hp@6500rpm! Going from 28hp to 38hp = 36%. So is under the +40% I suggested.
Engines whether 2 or 4 Stroke expels a % of Raw Fuel right out of the Exhaust. By using a Tuned Pipe, you are pushing back a % of that Raw Fuel back into the engine with Sound Waves from the Tuned Pipe, which makes more hp!
On Tuned Pipes, you can have Narrowband and Wide Band Tuned Pipes. As I said, for Plane use you want a Wideband use 2.0 in the bottom box. Improperly Design Tuned Pipes can have a Dead Spot in the Power Band. On a Good Designed Tuned Pipe, you should be able to draw a straight line from shortly after Idle to the Max rpm it was designed for.
Tuned Pipes are just that, TUNED for a Specific Engines Exhaust Port Spec's & Duration and rpm used. People have Cut, Turned, and Rewelded them and made them longer or shorter by that Chart to work on other Engines.
R&D made Tuned Pipes for both Sleds and Airplanes. Some were Good, some were Bad.
READ, 2 Stroke Tuners Book by Gordon Jennings. One of two people who wrote the Formulas for Designing a 2 Stroke Tuned Pipe. Learn for yourself.
Some of these people clearly don't understand when they say stuff like "Snowmobiles use a constant velocity transmission that allows the engine rpm to remain in a very narrow range while producing max hp." has nothing to do with hp made at these different rpms. That's a Mechanical Connection between the Engine and the Track and controlled by the Throttle. The Clutch can be set up to engage at different rpm.
Just as making a statement "The aviation equivalent is a fully in-flight adjustable Prop. Unfortunately, very few ultralights fly with in-flight adjustable prop." Once again, has nothing to do with Engine hp made at different rpm. It does allow you to change the Pitch to get more Pulling or Pushing Force by changing the Pitch. 99.9% of all Ultralights and most Kitplanes, Homebuilts don't use an In-Flight Adjustable Prop either!
The only things that affect your Engines hp made, is the Bore & Stroke used & Carb CFM used & the CR used & rpm used, and a Tuned Pipe if you use one! Using any Muffler on any Engine Restricts hp made, but they do lower the Sound Signature it makes. If you look at the Stock 277UL it's rated 26hp@6250rpm but actually Dynoed by R&D at 25.4hp@6000rpm. So a good indication the Muffler is too Restrictive. The other one was rated 28hp@6400rpm. Nobody has posted a Dyno Print of one actually making that 28hp. Like I showed, there are (3) ways to figure your approximate hp made for our 6500rpm. These same armchair mechanics have no problem with a Polni 250 DS 244cc making 36hp, or any of these other Small CC Engines that use a tuned Pipe, but when it comes to these Rotax's and Hirth's that do not use a Tuned Pipe, it's suddenly unbelievable!
Rotax Ricks 670 Dynoed (92hp@6350rpm) using 669cc, and makes 138cfm/92hp = 1.5 Constant and Dials in at 92% VE. 669cc at 92% VE turned 6500rpm = 94hp! 669cc at 93% VE turned 6500rpm = 95hp!
669cc/7cc= 95.5hp@6500rpm. So that's a pretty darn close estimate I would say. A Stock 1993 670 Dynoned 115.7hp@7750rpm which Dials in at 94% VE. So a 277UL 268cc turned 6500rpm using 94% VE = 39hp.
268cc turned 6500rpm using 93% VE = 38hp. 268cc/7cc= 38.2hp@6500rpm! Going from 28hp to 38hp = 36%. So is under the +40% I suggested.
Engines whether 2 or 4 Stroke expels a % of Raw Fuel right out of the Exhaust. By using a Tuned Pipe, you are pushing back a % of that Raw Fuel back into the engine with Sound Waves from the Tuned Pipe, which makes more hp!
On Tuned Pipes, you can have Narrowband and Wide Band Tuned Pipes. As I said, for Plane use you want a Wideband use 2.0 in the bottom box. Improperly Design Tuned Pipes can have a Dead Spot in the Power Band. On a Good Designed Tuned Pipe, you should be able to draw a straight line from shortly after Idle to the Max rpm it was designed for.
Tuned Pipes are just that, TUNED for a Specific Engines Exhaust Port Spec's & Duration and rpm used. People have Cut, Turned, and Rewelded them and made them longer or shorter by that Chart to work on other Engines.
R&D made Tuned Pipes for both Sleds and Airplanes. Some were Good, some were Bad.
n3puppy
Well-Known Member
- Joined
- Jun 25, 2019
- Messages
- 192
Tim
Sorry if I caused some confusion
The goal of the CVT in a Snowmobile is to maintain a constant engine RPM regardless of load/mph/throttle setting. The graph below shows how a good snowmobile transmission can be tuned to maintain the same maximum output rpm at any speed.
I also should have been more clear by saying constant speed propellors. With a constant-speed propeller as power requirements vary, the pitch automatically changes, keeping the engine and the propeller operating at a constant rpm If the rpm rate decreases, as in a climb, the blade pitch is lowered and the crankshaft rpm can increase to optimum RPM. The constant-speed propeller thus ensures that the pitch is always set at the most efficient angle so that the engine can run at good constant rpm regardless of altitude or forward speed.
In either case- Snowmobile or propellor -the goal is the same - Keep the engine at its optimum rpm.
Snowmobile Pipe manufacturers understand how that CVT works and design pipes counting on the help it gives them when they produce peaky pipes with high outputs over a very small rpm range.
Motocross race pipes are what are called "Wide Band" Because motorcycles don't have the advantage of CVT - they need a pipe that produces good power over a wide RPM range dictated by the manual transmission
The trade-off is a wide rpm range pipe produces less hp than a peaky Snowmobile pipe tuned for a narrow range.
Rotax has been making Snowmobile engines for years - They know how to make High output snowmobile expansion chambers. Yet they CHOSE wide range tuned exhausts tailored to aircraft use.
Since Fixed pitch props don't give the advantages of a CVT or constant speed prop they need the wide range lower power output characteristics of a Motocross pipe not a Snowmobile pipe
.
Sorry if I caused some confusion
The goal of the CVT in a Snowmobile is to maintain a constant engine RPM regardless of load/mph/throttle setting. The graph below shows how a good snowmobile transmission can be tuned to maintain the same maximum output rpm at any speed.
I also should have been more clear by saying constant speed propellors. With a constant-speed propeller as power requirements vary, the pitch automatically changes, keeping the engine and the propeller operating at a constant rpm If the rpm rate decreases, as in a climb, the blade pitch is lowered and the crankshaft rpm can increase to optimum RPM. The constant-speed propeller thus ensures that the pitch is always set at the most efficient angle so that the engine can run at good constant rpm regardless of altitude or forward speed.
In either case- Snowmobile or propellor -the goal is the same - Keep the engine at its optimum rpm.
Snowmobile Pipe manufacturers understand how that CVT works and design pipes counting on the help it gives them when they produce peaky pipes with high outputs over a very small rpm range.
Motocross race pipes are what are called "Wide Band" Because motorcycles don't have the advantage of CVT - they need a pipe that produces good power over a wide RPM range dictated by the manual transmission
The trade-off is a wide rpm range pipe produces less hp than a peaky Snowmobile pipe tuned for a narrow range.
Rotax has been making Snowmobile engines for years - They know how to make High output snowmobile expansion chambers. Yet they CHOSE wide range tuned exhausts tailored to aircraft use.
Since Fixed pitch props don't give the advantages of a CVT or constant speed prop they need the wide range lower power output characteristics of a Motocross pipe not a Snowmobile pipe
.
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