D&D Performance

[Legend]

1 hour ago, Legend said:

No, the piston at BDC is unsupported. 

Take a piston and put it in a cylinder on a work bench. At BDC, the piston is at its lowest point in the cylinder. This is also the point at which the intake and boost ports are fully uncovered. So therefore we know exactly the lowest point of the piston in the cylinder. 

If you set the cylinder top up on the bench, the cylinder skirts are what is touching the bench. Drop a piston in from the top. The piston skirts will touch the bench when it drops down. So now the piston skirts and cylinder skirts are even and down the exact same length. But look into the cylinder. You will see the intake and boost ports are not fully uncovered. 

So you pick up the cylinder until the ports are fully uncovered. You will have to pick up the cylinder 5/8 of an inch. So now the ports are uncovered, but the bottom 5/8" of the piston is outside of the cylinder, and unsupported. 

This causes the piston to be loose. On the upstroke of the piston, the piston skirt on the intake side is forced against the cylinder skirt. Here is where Indy Dan says its a rod ratio problem. But is it? No, because the rod ratio is the same as the Suzuki 800, probably the best 800 twin ever built. Indy Dan also does some serious welding of supports on the intake cylinder skirt to strengthen it.

But companies that use the spacer at the bottom also change the wrist pin location so the piston isn't dropping even further down past the cylinder skirts. But what they are doing is lessening the rod ratio, which helps the force against the intake cylinder skirt. They cannot make the piston shorter because at TDC the ports will become uncovered at the bottom of the piston. So this is a bandaid. But it helps. And as a side effect is also creates more case volume which forces more air and psi into the cylinder. More power. Not a ton, but some. 

 

The best and 100% proper fool proof way to fix it is to make the engine taller, by lengthening the cylinder skirts. But that cannot be done easily because the cylinder skirts cannot be lengthened any lower. Any lower and they would contact the crankshaft.

So polaris would have to totally redesign the engine. Polaris went all in in the mid 2000s on this design for compactness, and light weight. Yeah, the poo engines are significantly smaller and lighter that doo or cat. And at first, the poo design worked out good, because they only used the 600 and 700 cfi. The 6 and 7 cfi suffer the same flaw. But the thing that saves those engines is the smaller pistons. Less weight, less force against the intake cylinder skirt. My brother has a IQ 600 that had severely collapsed piston skirts, and the piston rocked so much, it knife edged the top of the piston. But it made it to 6500 miles before it lost so much compression it got really slow. 

 

To be continued.....

I will finish this later, I gotta go now.

But at 6500 miles most people will accept the fact that the engine is just flat wore out. And thats fine, I won't ever let a 2s sled go 6500 miles on stock pistons. Some people do get lucky and get more miles out of them. Its luck of the draw. Some people do everything perfect and stuff breaks, some people fire up and go WOT and shit lasts forever. But as a whole, its clear to see poo cfi engines fail more and sooner than Cat or Doo. 

 

So why hasn't Poo fixed this yet? Many reasons. First, cost of retooling. It would be huge. How often do manufacturers completely retool for new engines? Etec is basically the same design as as the Ptec. No Im not talking about bolt ons like EFI, Im talking castings. The Etec and Ptec are almost the same. Im not an expert on Rotax, but I believe they had some sort of casting change with the cooling system in the 07-10 range? But other than that they are largely unchanged. 

The Cat 800 has been the exact same for how long? Im not sure buts its been a LONG time. 

So they don't retool all the time. 

Another reason, the design of the engine, makes for a very fast revving engine. Im sure people can argue this, but IMO the Poo engines are by far faster revving than doo or cat. I didn't say more power, I said faster revving. Why is that so important? In the 2000s, mtn riding and tree riding exploded in popularity. We you are going slow and cutting super tight corners in the trees what do you need? HP or throttle response? Definately not HP. Throttle response is king in trees. HP is good for chute climbing. But the big chute climbing guys are on turbo 4s sleds. After the Pro RMK came out in 2011, it was the number 1 selling sled in the world. More than any trail sled. Poo caters to the mtn guys because thats where the money is. They buy new sleds every year. Im not dogging trail guys, Im just saying the sport has changed and everybody knows it. 

 

And then you have the compact size and lightweight of the poo engine. Its smaller and lighter than either doo or cat. This allows the sled to be narrower and they can put the CoG (center of gravity) where they want. A narrow sled in the mtns is way way better than a wide sled. It allows for extreme sidehilling with out paneling out, side panels hitting the snow and you slide downhill because of it. 

And lightweight is probably the most desired trait in a mtn sled. Not only is a lighter sled easier to dig out, its easier do manhandle. You can make a lighter sled do whatever you want, easier than a heavy sled. And you are not as wore out at the end of the day. The RMK has been the lightest sled since 2011, including trail sleds. 2016 155" track Axys RMK is 408lbs dry. Thats insane, a sled with 2.6" paddles on a track 155" long is 408lbs.... 

 

So while poo took a beating on these engines, especially from high mile trail guys, they still had the number 1 selling sled for like 3 years or so, Im not positive on the numbers. And it was by a lot. 

So Poo came out with the Axys with the 800ho. Yeah its a little different, a little better chassis, especially the trail skids, but its not a complete redesign from a chassis or engine standpoint. The engine is basically the same. Its certainly the same design, just with more bandaids on it. 

 

Im not saying its junk, if they don't come out with a complete redesign in the next 2 years, I will buy a AXYS 800ho RMK. But I will buy it with the complete understanding that while, IMO, I am getting the best mtn chassis, I am also getting the engine that needs the most maintenance. And I consider Pistons to be a maintenance item on any 2s engine.

[Legend]

BTW I also have a 800 XCR triple engine that my bud built. Its heavily modified, Around the 210-220hp range on pump gas. Those things are tough as nails. I had it out in Cooke City MT about 5-6 years back and got a hole in a coolant hose 27 miles from town at the Top of the World area. I didn't know I was loosing coolant until the engine lost power, like 60% of its power. I though i had a bad plug or something. Change plugs, drive it for awhile until it over heated again. Had a lexan hood with only a tachometer. I had a water temp gauge but the gauge took a shit and I never replaced it because the sled never ran hot. That was a mistake.

Anyway long story short. I overheated that modified engine until it cut timing, countless times that day. I replaced the hose once we got back to town and the engine runs great to this day. I didn't take it apart to check it, because it was a backup sled and it just ran to good with all of its power still. I haven't ridden it in 2 years now, but someday Im going tear into it and make it a lake racer/river rat sled. 

Edited October 20, 2016 by Legend

[snatchslayer]

22 hours ago, f7ben said:

yup ...

mohawk helmet...check

gopro for christmas - check

mbrp can on 2001 mxz 700 - check

backpack - check

8" riser so they can stand all the time - check

 

Pure fucking faggotry

Too fuckin funny lol. 

[f7ben]

Good posts Legend

[Mileage Psycho]

20 hours ago, f7ben said:

Funny you claim to have had a stock turbo achieve speeds that guys with 100 hp more cant run ...I ran my sleds on a trail...and had fun...and never lied about how fast they went

My sled consistently hit 115 GPS, and the best I saw on GPS was 128 on a fast surface with probably a very good tailwind, and my only mods were a Sandale muffler and some clutching. Anler rode my sled and he will tell you that the sled was flat out fast  

 

Oh and the two 800's to the left both clocked over 6,000 miles for the 2012 season.

[GGNHL]

48 minutes ago, Mileage Psycho said:

My sled consistently hit 115 GPS, and the best I saw on GPS was 128 on a fast surface with probably a very good tailwind, and my only mods were a Sandale muffler and some clutching. Anler rode my sled and he will tell you that the sled was flat out fast  

 

Oh and the two 800's to the left both clocked over 6,000 miles for the 2012 season.

128 on GPS on a stock sled? They barely hit that on asphalt.

[SVT MXZ XRS]

55 minutes ago, Mileage Psycho said:

My sled consistently hit 115 GPS, and the best I saw on GPS was 128 on a fast surface with probably a very good tailwind, and my only mods were a Sandale muffler and some clutching. Anler rode my sled and he will tell you that the sled was flat out fast  

 

Oh and the two 800's to the left both clocked over 6,000 miles for the 2012 season.

6 minutes ago, GGNHL said:

128 on GPS on a stock sled? They barely hit that on asphalt.

[Skidooski]

Must have been an Arctic cat GPS too  

[SVT MXZ XRS]

28 minutes ago, Skidooski said:

Must have been an Arctic cat GPS too  

KPH

[Wildcat]

[f7ben]

[SVT MXZ XRS]

Pour Wince

Edited October 20, 2016 by SVT Renegade XRS

[f7ben]

There are 2 scenarios that lead to Wince sleds achieving a top speed of 128 mph. 

A. It was tuned to the limit on pump gas and the setup was near perfect

B. It was in free fall from a B2 bomber

[Zambroski]

Just now, f7ben said:

There are 2 scenarios that lead to Wince sleds achieving a top speed of 128 mph. 

A. It was tuned to the limit on pump gas and the setup was near perfect

B. It was in free fall from a B2 bomber

LOL!  

Holy shit.....

[SVT MXZ XRS]

20 minutes ago, f7ben said:

There are 2 scenarios that lead to Wince sleds achieving a top speed of 128 mph. 

A. It was tuned to the limit on pump gas and the setup was near perfect

B. It was in free fall from a B2 bomber

[Edmo]

22 minutes ago, SVT Renegade XRS said:

My buddy got 125 out of his, and that's with about 4K in mods. And he knows what he's doing, he builds boat motors for a living, and has been modding sleds for years.

[f7ben]

4 minutes ago, Edmo said:

My buddy got 125 out of his, and that's with about 4K in mods. And he knows what he's doing, he builds boat motors for a living, and has been modding sleds for years.

It takes 250+ HP and a perfect setup to approach 130 on snow at trail height......ballsacks sleds to it easily with a $200 muffler and a tailwind though

[GGNHL]

14 minutes ago, f7ben said:

It takes 250+ HP and a perfect setup to approach 130 on snow at trail height......ballsacks sleds to it easily with a $200 muffler and a tailwind though

 

Drinking too much Artco Kool-aid must cause degenerative brain disease. Momo has to have been drinking it since 1962.

 

Edited October 21, 2016 by GGNHL

[SVT MXZ XRS]

37 minutes ago, Edmo said:

My buddy got 125 out of his, and that's with about 4K in mods. And he knows what he's doing, he builds boat motors for a living, and has been modding sleds for years.

32 minutes ago, f7ben said:

It takes 250+ HP and a perfect setup to approach 130 on snow at trail height......ballsacks sleds to it easily with a $200 muffler and a tailwind though

18 minutes ago, GGNHL said:

 

Drinking too much Artco Kool-aid must cause degenerative brain disease. Momo has to have been drinking it since 1962.

 

[Mowhawkcat]

On 10/19/2016 at 8:39 PM, Zambroski said:

I think Northstar is a pretty good tuner though.  But he sure digs himself a nice hole over on HCS at times....Ofda!  Gluten for punishment.  I think Jim "fastsledder" knows his way around that Poo pretty well too.  Hell, HSR...you're no slouch either.

All you retards on hcs are just that

retards 

you guys can't tune shit , especially red head fucktards from atta coconuts ontario 

[Highmark]

A famous dyno company has a good breakdown of the D&D setup.   I won't post up all the numbers but I don't see any false claims on there.  Muffler and fuel get it to 224 from 204.  Up the boost without reprogramming the ECU gets it to 245 (12.5 PSI of boost).   Need ECU changes to get higher.  

Edited April 18, 2017 by Highmark

[Anler]

On 10/20/2016 at 3:42 PM, Mileage Psycho said:

My sled consistently hit 115 GPS, and the best I saw on GPS was 128 on a fast surface with probably a very good tailwind, and my only mods were a Sandale muffler and some clutching. Anler rode my sled and he will tell you that the sled was flat out fast  

 

Oh and the two 800's to the left both clocked over 6,000 miles for the 2012 season.

Who's the faggot on your right? 

[Highmark]

They all go to the dealership together to make sure they got the same graphics?   

[racinfarmer]

56 minutes ago, Highmark said:

A famous dyno company has a good breakdown of the D&D setup.   I won't post up all the numbers but I don't see any false claims on there.  Muffler and fuel get it to 224 from 204.  Up the boost without reprogramming the ECU gets it to 245 (12.5 PSI of boost).   Need ECU changes to get higher.  

That is on the Sidewinder, eh?

[Highmark]

54 minutes ago, racinfarmer said:

That is on the Sidewinder, eh?

They say both TCat/Sidewinder.