I agree with you with sticking with the 660 .I am sticking with my 660 also. But as far as it being an overall better bike It has the 660 beat stock for stock. But I still don't get it Yamaha must be sleeping when it comes to building raptors. because a polaris 500 should not be even coming close to beating the raptor.

I heard because the predtior has more compresion then the raptor.

If you ask me the worrior is the only good quality quad that they made. I think if they put more time and craft into their engines they would be even faster then what they are.

 

Hey ShadyRascal not to be smart or to start anything but why did you get your son a z400 when he had a lt240r that is a much faster bike then a z400 what the 250 was to fast or something like that.

 

If enough of us email Maier, they will do a run of pink plastics.[img]i/expressions/face-icon-small-wink.gif[/img]

In the tight woods and hills around here, I will take low end torque over peaky high rpm power ANY time.

 

Actually, you are in the 700Rs prime habitat. I consider one if I lived there.

 

Pressure is somewhat true but, not entirely. Again, the more pressure (lower altitude) the more molecules per cc of oxygen. I have to come back to this. . . combustion occurs on a molecular level.

NOW, if you have a 12:1 compression pistion in your engine, you will (in most cases) need race-gas at sea level. As you go up in altitude, you won't build as much pressure in your bike due to the air molecules being spread out. This will result in a loss of pressure. The higher pressure you create in your cylinder, the more chance you have for pre-detonation (knocking) due to heat build-up (as you compress air it builds heat). Excessive compression (such as you see in a turbo diesel) can actually ignite without a spark-plug due to the heat you are building.

But, back to tuning. . . the reason you need to jet-down for altitude is due to a decrease in oxygen in your cylinder not pressure. True though. . . they are linked.

 

There is less oxygen because there is less pressure at high altitude, right? There isn't a less percentage of oxygen. If you have a turbo, you will not feel a difference in power if your boost is maintained.

 

I have an '04 Dodge with the Cummins Diesel. When I pull my toy hauler to St. A's I notice power loss at 5000 ft compared to sea level. I don't have a boost guage but I assume I am running equal maximum boost regardless of elevation.


Ron

 

Correct. . . there is less oxygen because the pressure isn't pushing the molecules closer together.

Think of it this way. At sea level it is like having 20 people in a room that is 10'X10' . . . pretty tight fit. As you go up in altitude the room get's larger and the people (molecules) spread out.

I'm not 100% on how a turbo responds at altitude. I'm sure it keeps things more consistant but, at altitude it needs to move more CFM of air to get the same # of molecules of oxygen into the engine.

Air does NOT equal Oxygen. Oxygen is a small percentage of what is in our air (I want to say about 15% but, don't quote me). That's why altitude has a such a large impact on tuning.

 

Hey, I agree with you, as I have a 2004 toyota tacoma with the trd supercharger running at 7psi. It doesnt matter where I go, its always getting approx 7psi, but there is a notable difference in power at altitude, compared to sea level. It makes perfect sence though, because your motor is just like you at elevation. Its breathing just as hard, but with less and less oxygen due to pressure like I was talking about.
7psi of boost is the same at sea level as 10k ft, but with less oxygen, meaning less power.
I always think of it as our jet engines. If you "goose" the throttles below 10,000ft, you have a TON of thrust, due to the thicker air, and the turbines grabbing more of it. It sets you back in your seat big time. BUT, at 40,000 ft, you do the same, and its not NEARLY as violent, as the air is thinner. This is why at altitude we have to watch our true air speed, as its very easy to over speed the airframe at altitude. You could easily go over "mach" at 40k ft.
Its interesting stuff.

 

It just seems to me that if you have 7 psi manifold pressure at sea level and at altitude, how would your engine know any difference? It is seeing the same intake charge. I could see it taking longer to get to 7 psi. Maybe you just have more turbo lag at high alt.