# Arctic Cat 800 HO Twin! Approximately 131hp at 6500rpm!

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#### n3puppy

##### Well-Known Member
That engine was a kind of disappointment to the snowmobile crowd - less Hp than claimed and rapid fall off as RPM decreased. A lot of aftermarket pipes, porting, ECU power chips/reflashes as a result.

This dyno run shows less than 160hp @ 8000 and only 112ish @ 6500. (Blue line stock)

Piped with a nice wide band power curve for a prop, 100hp @6500 would be reasonable.

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#### n3puppy

##### Well-Known Member
Used the search function. - "Arctic 800". Seems it has already been talked about here.

Mosquito helicopter guys used it at just 85hp.

#### Armilite

##### Well-Known Member
That engine was a kind of disappointment to the snowmobile crowd - less Hp than claimed and rapid fall off as RPM decreased. A lot of aftermarket pipes, porting, ECU power chips/reflashes as a result.

This dyno run shows less than 160hp @ 8000 and only 112ish @ 6500. (Blue line stock)

Piped with a nice wide band power curve for a prop, 100hp @6500 would be reasonable.
View attachment 118004
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That happens, Dead Spots in the Power Band, when you try to stretch out the Power Band from 3500rpm to 8000rpm! The 800 is actually 794cc and if making 160hp dials in at 107% VE. 794cc/7cc= [email protected] Probably a little higher since it uses a Higher 13:1cr vs 11.5cr.

What rpm would this 800 be turned to make:
25mph
35mph
45mph
55mph
65mph
75mph
85mph
95mph
etc.
Snowmobile Speed Calc.

Using anything over 95hp on a Sled is just ridiculous! Average Trail Speed is 25mph. I usually run 25mph to 45mph Max. Many Trails have a Speed Limit today since to many Knuckle Heads have gotten Injured or Killed or Injured or Killed other People!

My 94/95 Yamaha Vmax 600's are 95hp and one of the Heaviest Trail Sleads ever made and will do a little over 105mph, and Nobody needs to be doing 100+mph on any Sled anywhere. 794cc/160hp= 4.9625cc to make 1hp!

794cc at 8000rpm at 107% VE = 160hp
794cc at 7500rpm at 107% VE = 150hp
794cc at 7000rpm at 107% VE = 140hp
794cc at 6500rpm at 107% VE = 130hp <---- 794cc/7cc= [email protected]
794cc at 6000rpm at 107% VE = 120hp
794cc at 5500rpm at 107% VE = 110hp <---- That's WHY most Sled Pipes don't make a Good Tuned Pipe for Airplane use!

Using 7cc to make 1hp = 93% VE is the Lowest I would go for Plane use.

R&D Aeros Mild Tuned Pipe 277UL 268.8cc/30.5hp= 8.8cc to make 1hp.

R&D Aeros Mild Tuned Pipe 503UL 496.9cc/62.3hp= 7.97cc to make 1hp.

Rotax Ricks Tuned Pipe 670 669.2cc/[email protected]= 7.27cc to make 1hp. 669.2cc/7cc= [email protected]

He has a New Tuned Pipe for the 582UL/583 making I think it's rated [email protected]
580.9cc/79hp= 7.35cc to make 1hp.

R&D Aero's 583 Tuned Pipe made [email protected] Made [email protected]! When you Graph the hp/rpm Numbers it wasn't the best Pipe.
580.9cc/76.9hp= 7.55cc to make 1hp.
580.9cc/87.5hp= 6.63cc to make 1hp.

#### n3puppy

##### Well-Known Member
Did a little more research - Mosquito Helicopters is now using the 800 engine at 90Hp @ 6000 rpm
They specifically say HP/rpm held to low numbers for reliability.
794cc @ 90hp @ 6000 = 8.82cc /hp = 122.8 bmep

That is in line with what other factory aviation folk do
Rotax 582 - 581cc [email protected] = 8.94cc/hp = 116.4 bemp
Rotax 618 - 617cc [email protected]= 8.34c/hp = 115.5 bmep
Hirth 3503 - 625cc. [email protected] rpm = 8.93cc/hp = 112 bmep
Simonini Victor 2 Super - 802cc [email protected] = 8.02c/hp = 130.7 bmep

As always - Making Aviation hp with any engine is a series of tradeoffs.
The real question - NOT how much horsepower CAN it make but how much SHOULD it make.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
... and how LONG will it make X horsepower before it has to be gone through (or removed from the farmer's field)?

#### Armilite

##### Well-Known Member
... and how LONG will it make X horsepower before it has to be gone through (or removed from the farmer's field)?
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The same as most Engines that aren't Built right or maintained right. 99.9% of all Engine Failures are linked to a Human! Every Type of Engine has it's Failure Points!

For 2 Strokes it's:
1. Detonation #1 Problem, 85% of most 2 Stroke Failures! <-- Easy to Fix, burn 93+/100LL!

2. 2 Stroke Oil used! <---- Easy to Fix, Buy Oils with High Flash Points!

3. Fuel System ( Fuel line, Fuel Pumps, Fuel Filters)! <----- Easy to Fix. Use Tygon Fuel Line and change out the other parts more often.

4. Carb Boots & Case Seals! <--- Easy Fix. Use JBM Carb Boots & Case Seals! Like Rotax has a 300hr or 5 Year TBO whichever comes first. If you're Burning the Full Synthetic High Flash Point Oil or Hirths Bluemax Oil at 100:1 Ratio, with Ceramic Top & Moly Coated Pistons, you should be able to go to 700hrs or 10 Years whichever comes first.

5. You can't Fix Stupid people, who don't rebuild the Engine right, Bore & Hone the Cylinders right, don't Install things like Oil Injection right, don't Jet the Engine properly, don't Bleed an Engine properly, Clearance the Engine properly, etc!

Even 4 stroke Certified Engines Fail!

#### Victor Bravo

##### Well-Known Member
HBA Supporter
You are 100% correct on all of the above, however the historical fact remains that a lot of people always use the max HP "brochure" number to decide what engine to put in a particular airframe. So the amount of time that the engine can make 60 or 75 or 90% of it's max horsepower does become a major consideration, whether anyone likes it or not.

Most of the classic old-school dinosaur airplane engines mounted in old-school dinosaur airplanes can fly around at full throttle for 1000 hours without a catastrophic failure. I am not aware of any 2-stroke engines that were designed to do that, but I am far from an expert on 2-strokes.

YES, certified 4 stroke engines can and do fail. At what rate compared to other types of engines?

The modern 2-stroke engine makes a huge increase in power-to-weight ratio compared to the 4-stroke, no argument from me. But where do you suppose the "no free lunch" comes into balance?

#### rv7charlie

##### Well-Known Member
I can't make myself fly a 2stroke, so I'm not defending the current subject engine. But there's a reason that
old-school dinosaur airplane engines mounted in old-school dinosaur airplanes can fly around at full throttle for 1000 hours without a catastrophic failure
The reason is that at full throttle they're operating at 40-50% of actual full power. They can easily run at at least 50% higher rpm than their rated max, with the obvious increase in power, and the obvious decreases in life & reliability. That's how they last so long; they're spec'd to operate at about the same power level as a lot of automotive engines operating in cars.

#### Armilite

##### Well-Known Member
You are 100% correct on all of the above, however the historical fact remains that a lot of people always use the max HP "brochure" number to decide what engine to put in a particular airframe. So the amount of time that the engine can make 60 or 75 or 90% of it's max horsepower does become a major consideration, whether anyone likes it or not.

Most of the classic old-school dinosaur airplane engines mounted in old-school dinosaur airplanes can fly around at full throttle for 1000 hours without a catastrophic failure. I am not aware of any 2-stroke engines that were designed to do that, but I am far from an expert on 2-strokes.

YES, certified 4 stroke engines can and do fail. At what rate compared to other types of engines?

The modern 2-stroke engine makes a huge increase in power-to-weight ratio compared to the 4-stroke, no argument from me. But where do you suppose the "no free lunch" comes into balance?
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YOU, should always Power your Plane for its MTOW! The Industry Standard for a 2 Stroke is 6500rpm! IF, you're lighter, nothing says you can't use a lower rpm. Most Part 103 Ultralights have an MTOW between 450 lbs (27hp) and 660 lbs (40.1hp)! If you want it to Fly Well, I would use the Simple Rule of 1kw for every 10kg! The Lazair Ultralight is a very good example since it was made using (3) different sets of Engines. First (2) 5.5hp = 11 hp that Flew Marginally, was soon upgraded to (2) Rotax 185UL's making 9.4hp = 18.8 hp, that flew better, but many People were still not happy so they put (2) Solo 210's at 15hp each = 30hp. MTOW is 450lbs = 204.1166 kg / 10 kg = 20.41166 kw needed = 27.37249 hp to Fly Well! 27.37249/2 = 13.686 hp per Engine needed. Today, these Honda/Clone GX200/Predator 212 Engines have been used upgraded to each making around 15hp! The Lazair is a Motor Glider Ultralight and they used very POOR SIZE PROPS! WIKI says 185UL Power Output: 9 hp (7 kW) at 5000 rpm. 7kw = 9.387155, rounded up is 9.4hp. Skidoo's website put's the ROTAX 185 at 6kw or 8.046133 [email protected] x 2 = 16hp! You can over power just about any Aircraft if you want.

Hmmm, are we really going to compare CERTIFIED 4 Stroke Engines turning only 1900rpm to 2750rpm ranging from the: A50: 50 hp (37 kW), Compression ratio 5.4:1, max rpm 1,900. Displacement: 2.8 L (171 cu in) Bore and Stroke: 98 mm (3.9 in.) x 92 mm (3.6 in.) Weight: 72.6 kg (160 lb)
2,800cc, to the O-200A $25,000 Specifications! Most of these had a 1800hr to 2400hr TBO! General characteristics • Type: Four-cylinder air-cooled horizontally opposed piston engine • Bore: 4.06 in (103.1 mm) • Stroke: 3.88 in (98.6 mm) • Displacement: 201 in³ (3.29 L) 3,290cc • Length: 28.53 in (724.7 mm) • Width: 31.56 in (801.6 mm) • Height: 23.18 in (588.8 mm) • Dry weight: 170.18 lb (77.19 kg) dry, without accessories Which 90% of them Old Dinosaur 4 Strokes aren't made today and haven't been for many Years! None were ever used on any Part 103 Ultralight, and most were not used on even Small Kitplanes either, an account of Weight to hp ratio & their High Cost. There are 503UL's and 582UL's out there with 1300+hrs and still Flying! The Accident Ratio between Small Commercial Made Planes to kit planes was 50/50 account you have the same people who don't maintain their A50 to O-0200 either! Build a 1000cc to 2000cc, 2 Stroke and turn it much lower rpm for say 100hp and it will last a long time too if you maintain it right. KEYWORD "Maintain" it right! Run a Good 93/100LL Octane Gas with a Good 2 Stroke Oil with a High Flashpoint! Just a 1000cc 2 Stroke Engine: 1000cc/7cc= 142.8hp@6500rpm! [email protected], [email protected], [email protected], 99hp@4500rpm! A 1500cc/7cc= [email protected]! A 2000cc/7cc= [email protected]! That 800cc/7cc= [email protected]! 800cc at 6000rpm = 105hp 800cc at 5500rpm = 96hp 800cc at 5000rpm = 88hp 800cc at 4500rpm = 79hp Rotax 912 80hp@5800rpm$17,258.00 = 1,211.2cc!

O-200 Displacement: 201 in³ (3.29 L) = 3,290cc making [email protected]

Even the Pegasus O-100 a 1/2, O-200 so 1,645cc, he rates it at 58hp using a higher 9.0cr. Power to Weight Ratio is just too low. The Same reason for those other Old Dinosaurs that fell by the wayside. Nice concept, but I would have done more mods to get 75-80hp to make it more useful.

4 Strokes Weakest Link is the Valve Train.

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