Engine hp

Taft Racing said:
Hmmm. I don't know jerry . Ed Schriefels sat outside pole at the big. O and he ran a 131. Now Ed is a pretty big boy. I know his kart and he weighs in at 415 lbs. Now I don't know what weight Robbie weighs in at but you are allowed to get down to the 430lb mark. So I'm not sure what chris is saying . I'm not good at guessing but I know the recovery rate for making a mistake on the little purpose built engines kills them against the big engines.
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If he weighed in at 415# then we gave him 72# and you should realize that at the Big O race it was our very first time on the Umax and we had alot of speed left that we didn't get out of it at the time we qualified as for the race I told Robbie to take it as easy as he could while leading if he could because I didn't know how the tire wear going to hold up with everything being new to us, This statement is backed up by our fastest lap was on lap 17 when McDonald hit us in the rear bumper the lap before letting Robbie know he had to run it a little harder and we pulled awat from him five or six karts in the closing laps. I know we could run alot faster than we did now verses when we ran that race but at the time we didn't need to run any faster than we did.
 
SeayHiPerformance said:
There are principles in establishing acceleration rates that gives some motors advantages over others, even though one may have more torque. One is inherit to the motor, the other is to mechanical setup.
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Chris,
I am familiar with one of the not common knowledge assets of the BRC engine design. The particular mechanical advantage
is a design that could be incorporated in any piston engine.....big or small, high displacement or low.

Is there another advantage you speak of, which is dependent upon the engine size and weight being relatively low??
 
Forget HP/Torque. What your really looking for is "FORCE" at the rear wheels through the efficiency of the drivetrain, and rpm ability of the motor. Naaa, forget what I just wrote......Its all about who wins the most races! :)
 
JawaMaster09 said:
If he weighed in at 415# then we gave him 72# and you should realize that at the Big O race it was our very first time on the Umax and we had alot of speed left that we didn't get out of it at the time we qualified as for the race I told Robbie to take it as easy as he could while leading if he could because I didn't know how the tire wear going to hold up with everything being new to us, This statement is backed up by our fastest lap was on lap 17 when McDonald hit us in the rear bumper the lap before letting Robbie know he had to run it a little harder and we pulled awat from him five or six karts in the closing laps. I know we could run alot faster than we did now verses when we ran that race but at the time we didn't need to run any faster than we did.
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Jerry I wasn't comparing your days performance against eds only that he regularly weighs in at a weight close to the 430lb required for the big engines. I also have no idea what the jawa forces you guys to do weight wise to get it balanced. My problem with my 450 was mikes rate of acceleration it was massive , fighting lack of forward bite then having to throw out a anker to slow it down and not over run the corner. It boggles my mind to see how you guys can hook that jawa up. I'm saying to mike that there's a speed Thats optimum for a given track and conditions and the weights are karts run at. Using a measurement system to try and find that perfect blend of power. To me hp/torque/force/work these are all just measurements we use to find what works best. I have no idea what he's trying to say. But that's not anything new lol.
 
SeayHiPerformance said:
Forget HP/Torque. What your really looking for is "FORCE" at the rear wheels through the efficiency of the drivetrain, and rpm ability of the motor. Naaa, forget what I just wrote......Its all about who wins the most races! :)
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Forget it ? Now how are we supposed to figure out how to win more races? Ok let me try and figure this out. From now on I'll just think win more win more win more lol. Is "force" related to "work". Just wondering
 
Taft Racing said:
Mike on the start we accelerate. Once up to speed we do all we can to maintain that speed. The big engines can recover from mistakes much easier than the little high rpm engines. As for weight and NASCAR why do they look for more down force? Thats more weight to the tire which equals more bite. More bite more grip more speed. And before you say it. No I do not think its possible to lock down a jawa 450 or 250. I'm not real sure you could lock down a 131 or brc either.
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Again, Physics.....downforce is very different than mass. Adding mass to the kart means that mass has to be accelerated. Downforce is less at slower velocities so the "weight" as you like to call it is also less. Where do you want to accelerate? Off the corner, obviously.

All things considered, downforce is better than mass and an engine that is more apt to accelerate is better than one that doesn't. Gyroscopic forces can also have an effect on handling. That is why we balance our tires....well, at least I do.

Mike
 
azrcr said:
I'll have to agree to disagree Mike, karts don't have suspension, I'd say you just didn't tune your 250 kart to the track.. it takes a quite a bit different setup.. i'm guessing you had a trans 250, alot more weight on the right rear..

I'd take a 30# weight break, as we have run it light, it's just not as well handling.. with the big engine it's kinda mote anyway, as there's more power than any sane person can handle.

I can think of only one reason a laydown jawa is perferred, is to lower cg, the upright and laydown engines weigh the same.. same reason I don't want the extra 25-30#'s of a trans and clutch hanging on my right rear.. not conducive to a good handling kart..
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Well, explain the same kart, the same day, with the same tires, no weight and 32lbs of weight added. .2 seconds a lap difference. The MyChron Gold had near same corner speed. The acceleration, top speed and braking were the areas lacking.

Just "guessing" is a waste of time. The gauge doesn't lie when you use the track mapping option. This is a small dirt track. "Hooking" up the kart isn't an issue. I was applying the fuel well before the apex of the corner. Corner entry is the big weak point of this track. Slowing down a kart that weighed 30+ extra lbs had a huge negative effect on the kart.

I have added ballast to a kart to help it before. It is a crutch. Chassis school taught me something. Don't take away from something to help something else unless it is a last resort. Figure out the real problem and find a solution to that problem.

As for a laydown engine vs an upright engine, consider the effect a large piston going up and down has on the chassis vs that same piston going forward and backward. There are engineers at more than 3 different race bike companies that believe it makes enough difference to spend millions of dollars on development.

Mike
 
Downforce adds weight, no matter how weight is added, it is still weight.. so with more downforce nascar has to build more hp to overcome it or take weight off the car..

Theres a point of diminishing returns, I don't think 430#'s hurt the big engines, I think it helps, you could probably add weight, without seeing a speed/handling issue..

Downforce and mass, totally different.. but you need both... take the same kart with a wedge, and run a straight body and the same weight and see what happens..
 
Taft Racing said:
Forget it ? Now how are we supposed to figure out how to win more races? Ok let me try and figure this out. From now on I'll just think win more win more win more lol. Is "force" related to "work". Just wondering
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Without force, work isn't possible.

Mike
 
Tim and Mike,
Javafoil......Google it. It's a really great tool for people that really don't understand air. (That is me). There is another site in AJ Designs. It is a calculator for many things "physics" related and a whole bunch of it applies to racing.....anything. Physics doesn't care if it is a car, a boat, a plane, a bicycle, a dog, or a kart.

Mike
 
Mike, Bernoulli law, taught in high school science, air is not that hard to understand.. just sayin..

There are also alot of f1 sites, evolution of the body designs that are pretty cool..
 
One more thing for you guys having issues "hooking up". Buller sells a digital ignition that is a direct replacement for what many of us use. There are 2 curves available....totally programmable. Anyway, if you can't hook up, go from curve 1 to curve 2. You can turn it on and off as needed. You can even have it done automatically. All you have to do is figure a way to tell when you are spinning the tires. It isn't hard or expensive.

Mike
 
azrcr said:
Mike, Bernoulli law, taught in high school science, air is not that hard to understand.. just sayin..

There are also alot of f1 sites, evolution of the body designs that are pretty cool..
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Well, if you "think" you understand what air does, F1 and NASCAR are always hiring. I promise you, they pay much better than you and I make put together.....

Mike
 
I don't understand why you would say torque is irrelevant. My weed eater revs up pretty quick but it has no torque and I would not expect it to accelerate my kart. You can multiply your torque with gearing but you better have some torque to work with. Any top notch engine builder should know what RPM he is trying to achieve peak torque and peak hp. He should also know how broad of a power band needed to get around a track. I try to build power to cover at least 3000 RPM. If you can accomplish that you will be competitive. I have some experience in calculating acceleration, mass, aero with different amounts of hp. There were slide rules that would do this 30 years ago. And the money we spent reducing rotating weight, reciprocating weight to help out motors accelerate faster was considerable. If you are trying to accelerate mass at a fast rate without torque, then you are quite simply defying the laws of physics.
 
MikeGrady said:
Without force, work isn't possible.

Mike
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As a matter of fact; if I remember right, “work = force over distance.”
There is a joke about a guy holding up a piano to keep it from falling off a truck; how much work is being exerted? Answer; none, nothing is moving.
Comments, compliments, criticisms and questions always welcome.
 
I'm going to the wind tunnel tomorrow morning for a six hour shift then back Wednesday down force car. Then Friday with speedway car busy week
 
If y'all advocate getting a kart "down into" the track via more weight, why not stay light and use a skinnier tire? P = F/A......if you want more P, reduce the A.... I've wondered about going to 7.10's on 5" rims at the rear....would also get me some more adjustability on the RF. If I try this season, I'll post back here. Plus I keep hearing that the reason the stockers went to the 6" tires was that it freed the kart up... I want more "bind" (= grip), so should I go back to 5" rims? Can you give a science-based answer why or why not? It seems to me that the 6" tire has a more optimum forward bite contact patch, and the 5" tires may have a more optimum lateral grip contact patch -- I'll take the latter if I have to make a choice.
 
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