First of all head is right, a predator has more potential to go fast. It has a better designed cylinder head, stronger crank, stronger clutch, better gear ratios at higher rpms, better ignition design, and if you want to talk about motocross i just looked at a guys yfz that he had for 3 days with a cracked swingarm. The yfz's and hondas are good machines, but they dont have anywhere close to the potential as a predator. The honda 450s max horsepower is under 60 , and yamaha yfz 450 is under 70. And for your information my dad ( doug nicholas') 500 predator revved to 11,700.

 

answer me this then.. why dont more of the best races ride preds/? thas what i though

 

Freez, for your information facts and figures on paper are a good starting place. The dyno is another place to start, but real world racing and ET times and speeds telll the truth. Thats the final test. All your equations are good but what about pulse waves? And we use custom ignitions that lets us rev to whatever rpms we need, and i can change the curves for different fuels. All the motors on these predators have been tested on gas fuels only, not NOS or alcohol. Do you build race engines yourself? If so, lets here some combinations you use? My dad has built more predator engines in different states of tune than anyone in the US. He knows what actually works and what doesnt by testing it, not by writing it on paper. We went to a regional 3 state drag race in wisconsin. I didnt see you there. The 727 raptors werent with in 3 tenths of a second of us in a 100yd drags. and the yfzs werent as close as that. The hondas arent as close as the yamahas. I dont have any hate torwards other brands, i appreciate anything that someone can make go fast, I'm just telling you what i know.

 

A piped turtle could probrably outrun my wife's Blazer. [/quote]



Thanks for the chuckle.

 

Predmatt24. I agree with you that one can make the Predator rev to 11 700 rpm. The point I made is that a stock off the showroom floor Predator will NOT make 60 HP stock. Some people claim they do, which is utter nonsense. Not only do I say that, all other people that had the stock predator on the dyno agree with me. The web is full of them, yet people like you say exhaust builders and other tuners are wrong. You always know some special tuner that is able to achieve miracles.

If you read my post correctly, I do mention that it will be possible for the predator to make 60HP, or more, but it will not do it in stock form. The only way it will be abel to do it in stock for is if it was able to produce max HP at 11 500 RPM. The stock CDI, compression ratio, bore and stroke, cams, just about everything inside the motor will not allow for this to happen. IT IS IMPOSSIBLE! Do not confuse max RPM and the RPM where a motor produces max HP. Even with your new CDI and rev limiter you will not get max power at 11 500 RPM. You have to upgrade the cams, run higher compression, bigger and lighter piston, race fuel, new rod and cranks and you still will be lucky to get max HP at 9 000 to 10 000 RPM. PS. I have seen lots of Predators blow the rods, due to bigger pistons, so much for the "strongest" motor around. They suffer form the same old problems as the rest of them.

Since your dad have tuned so many Predators, please supply these dyno runs of a 60HP stock predator and then some dyno runs after the mods he has done. It gets me that people shoot their mouths off about 60 HP this or that, but they have never seen a stock Predator do these figures on a dyno, nor can they provide the proof.

Changing ignition curves is one thing, but it does not mean you can change the motor to make HP at 8000 and after the CDI it will make max HP at 11 500. Any engine builder will tell you that you need some special new toys in the motor to get even close.

O buy the way. The more you tune the motor by adding more cams, pistons and all kinds of other toys, the more it losses volumetric efficiency. It becomes more and more difficult to produce the HP the more you add. The mods do add more power, but since you don't change the head design, change the carb, the ports and the valves, there is no way that they can deliver the air needed to make the motor breath properly and maintain efficiency at that RPM.

But as always, the teenagers around here will not believe me. They always seem to be able to defy the laws of physics.

Please help us all here and correct us once and for all. Bring the independent dyno runs that prove your point. Get us a web site with dyno runs that prove a 60 HP stock predator. It should not be difficult nice you all are so adamant and claim these figures are true.

If not stop wasting your time. All you do is change the subject once we prove you wrong.

 

True, very true. Let's talk about pulse waves.

Every engine has them. Every good engine designer/builder tries to use them to the best of his or her ability. The way we do that is to tune intake and exhaust lengths to take advantage of them. The unfortunate thing is that these lengths are not variable. They will only work to your advantage in a VERY narrow rpm range.

Now... if everything else is tuned correctly... porting that is matched to where you want to make power, camshafts to match the porting and the above mentioned pulse (tuned intake and exhaust) hit all at the same time, you will have the absolute most power you can possibly make given the combination. This could be low in the rpm range, in the middle or up high, depending on how everything is set up.
This is true, real world, volumetric efficiency. It's not only a mathematical equation... it is, in fact, an actual occurrence.

The other thing that I believe was mis-stated is that 100% VE is if you can fill up a cylinder with air fuel mixture fully, and then completely burn it all, it will make the maximum potential for that amount of space. Of course we don't actually get to this number generally because of design necessities of camshafts, cylinder heads and combustion chambers. The only way we can normally and easily achieve 100% VE or better is to Turbo or super charge an engine. Basically cram more air into that cylinder than it would ever think of being naturally aspirated.

This is where testing pipes, intakes, port jobs, and so on makes things all come together. One pipe may not work as well with a particular port job but may work awesome with one that is more radical. The list goes on and on and on and on..........................

Matt, If your dad has one of these sweet perfectly tuned setups then awesome. But I concur with Freez. Don't get too bent on the math because we aren't waist deep in Predator parts. I guarantee you that top fuel racers didn't and don't just slap things together to see what works... they work it out on paper first to see if it's a possibility. If it is... then they design a part to function at the absolute peak and then tweak it to make it work perfectly.

I just LOVE physics!!!!!!!!!!! [img]i/expressions/face-icon-small-wink.gif[/img]

 

I used 100% VE to prove that even with a well tuned motor the predator will not make 60HP. BlackWidow is correct. To achieve 100% VE is difficult, although not impossible. Most ATV motors will be around 90% maybe a little more. On the Dyno I manage to get stock Raptors to deliver 98% VE. Stock DS650's run close to 90%, but they need extra work to get them flowing better. The Ds can also be made to have a VE of just over 100%. I had a raptor once, then gave me a lucky break. I managed to get 102% VE. It produced 49.5 HP at 7000 RPM at the rear wheels.

Superbikes is a different story. They usually have a 100% plus VE as standard. The reason for this is that they are designed to do it from the factory. They also have much more technology inside the motor to achieve this.

To get an ATV motor to have a VE of 100% plus takes lots of time and special parts. VE is purely achieved with a better exhaust, and intake system. Changing the compression ratio, bore or stroke change things for more HP, but it will most of the time reduce the VE value, as the rest of the head design is not designed for it.

Most 686 Raptors are perfect examples. They have the HP, but their VE is much lower than a stock 660 with a good pipe and intake system. Again, it is because the head, ports, carbs and exhaust pipes where not designed for the bigger capacity and to get the VE up you have to change carbs, bigger valves and so on.

 

Everyone just smile and get along.
I didn't start this post to bash the predator or to have all the polaris boys get testy about how much HP there machines could make.
I just wanted you guys to get a laugh out of a moron that doesn't know anything but can bs like the best jr high kid out there.

Freez your posts are awesome i've learned a lot from them.
brain hurts now but i learned something.

Maybe if i see him out there i'll just line up with him for the heck of it to see if his motor is really tuned that tell. With my CR250 that is. hehe

 

E-mail me and I'll share some tuning secrets with you on the raptor. You might just get the power to beat the big mouth next time, even riding a stock raptor. [img]i/expressions/face-icon-small-wink.gif[/img]

 

My head starting to hurt trying to understand this all...I need to go back to sleep.

*never read this post as soon as you get up*