900/1000 dogs compared to 650/750?

andy9802gt wrote:

PLUMMEN wrote:

turboguzzi wrote:

back to a bit of science.... shooting this at Larry
C as he stated elsewhere that he has seen Rainey in action on the GPZ750, but if anyone has answer to the next question he's welcome to shed some light:

What was the difference in lap times in AMA superbike racing when the switch was made from 1000cc to 750cc in 1983? Kawasaki won back to back in 82' with eddy on the KZ1000 based bike and in 83' with Wayne on the GPZ750 based bike, so which one was faster on pure lap times, (on same circuits of course)?

TG

and to make it really fair,how much faster was was eddie lawson on a 750 than a 1000 of the same year?

So I'm starting to get confused. I spent about $3000 on my big motor to make it faster and I could have just bought a 650? I guess the entire racing world has had it wrong for 50 years, there IS a replacement for displacement.

Written by David Reher

Looking back at the 2004 season, I can attribute much of the performance improvement in Pro Stock to faster engine speeds. It’s difficult to believe that 500cid Pro Stock engines now routinely turn 10,000 rpm, but the truth is plain to see on the data recorders and on the time slips.

The trend toward higher and higher engine speeds was also evident in NASCAR stock car racing until the rulemakers applied the brakes with new restrictions on rearend and transmission gear ratios. Now the growing interest in fast bracket racing, Top Sportsman, and Top Comp eliminators is bringing this same high-rpm technology to sportsman drag racers.

Why does turning an engine higher make a race car run faster? This is my final column of the year, so I’ll offer my ideas and hope that they give racers something to think about over the winter break.

The simple explanation is that raising rpm effectively increases an engine’s displacement. This might seem nonsensical because the volume displaced by the pistons doesn’t change, but consider the effects of filling and emptying the cylinders faster in real time. An internal combustion engine is an air pump, and if we turn that pump faster, we can theoretically burn more fuel in a given amount of time and consequently produce more power. For example, an eight-cylinder engine running at 6,000 rpm fires its cylinders 24,000 times in one minute (assuming perfect combustion). Increase the engine’s speed to 8,000 rpm and it will fire 32,000 times per minute, a 33 percent increase. The volume of air and fuel that moves through the engine is now equivalent to an engine with a much larger displacement. There are also 8,000 additional power pulses per minute transmitted to the crankshaft that can be harnessed to turn the wheels and accelerate the car.

Raising engine speed is analogous to supercharging or turbocharging a motor; the goal is to increase the volume of air and fuel that moves through the engine. The airflow is increased with a forced induction system by pressurizing the intake system; in a naturally aspirated engine, the airflow is increased by raising rpm. If done correctly, both approaches will increase power.

A higher revving engine also permits the use of a numerically higher gear ratio to multiply the engine’s torque all the way down the drag strip. Let’s say an engine that produces 1,000 horsepower at 7,000 rpm is paired with a 4.56:1 rearend gear ratio. If this engine is then modified to produce 1,000 horsepower at 8,000 rpm, it can now pull a 4.88:1 or 5:14:1 rearend gear without running out of rpm before reaching the finish line. The numerically higher gear ratio gives the engine a mechanical advantage by multiplying its torque by a greater number to accelerate the car faster – in effect, it has a longer lever to move the mass.

I learned this lesson many years ago when I started drag racing. I raced my little 302cid Camaro against 426 Hemis and 440cid Max Wedge Mopars. The big-inch engines had thunderous low-end power, but my high-revving 302 with a 4.88:1 rear gear would just kill them because they were all done at 5,800 rpm. My small-block had much less torque and horsepower, but I could multiply the power it had with a steeper gear ratio. The same principle applies to racing a Pro Stock or a Top Sportsman dragster. By turning more rpm, we can use a greater gear ratio to produce more mechanical advantage to accelerate the car.

There are limits to engine speed, of course. Higher rpm increases parasitic losses from friction and windage. The stability of the valvetrain also restricts engine rpm. However, with the technology developed in NASCAR and in Pro Stock, racers are learning how to build engines that operate reliably at high rpm. Research and development on valve materials, springs, rocker arms, and pushrods are now being applied to serious sportsman drag racing engines. In fact, I wish that I had some of the parts that we now install in our high-horsepower sportsman engines for our Pro Stock program a few years ago!

While increasing rpm is generally a good thing for a racing engine, it also puts more responsibility on the owner. A high-rpm combination requires more vigilance and more maintenance than a low-rpm motor. It’s important to check the valve lash frequently and to look for early warning signs such as weak or broken valve springs. Neglecting these parts in a high-rpm racing engine can produce some very expensive problems.

Raising an engine’s operating range also requires complementary changes in the drivetrain and chassis. A high-rpm sportsman engine really needs a high-stall torque converter to realize its potential. With an automatic transmission, the engine speed should ideally drop 1,000 to 1,300 rpm after a gear change. For example, if the converter stalls at 6,700 rpm, the engine should be shifted at around 8,000 rpm. Shifting this engine at 7,000 rpm would simply put the engine back on the converter, causing the converter to operate inefficiently and wasting horsepower by heating the transmission fluid.

I’m excited about the emerging trend toward fast sportsman drag racing. I enjoy working with customers who want to go fast because it gives me an opportunity to deliver the benefits of our Pro Stock R&D to other racers. Not every racer wants or needs a high-rpm engine, but if the goal is to have a fast car, raising the redline is a proven approach

PLUMMEN wrote:

how about we settle it this way,i spend $5000.00 building a 900/1000 and you spend $5000.00 building a 650 and we compare notes at track midway for both of us?
we can do just like the magazines do compare them on the road,on the drag strip and roadcourse track

If I had $5,000 I could build a bike or buy a bike in any class that would be a winner. The point was dollars per horse power or performance. Throwing money at a bike was NOT the point. Do you throw money at every thing to make up for lack of skill and ability or are you just lazy and want an easy but costly answer?

Plummen if I had looked and seen your a licensed master plumber, the skill and ablity thing would never have come up. I can port heads and D port also. I can't weld well and I messed up my last frame cut and had to build a jig to fix it. I have built small blocks and one big block. It was a 427 with the same crank and rods as your 396. I shifted at 7200 with it, cast pistons and all. I am not a licensed master plumber yet, never took the test because I don't want to pull permits. I have built alot of bikes and cars but never a crank up 1000 or 650. My 1000b3( my dad got the bike from the first owner so I have riden or fixed it for over 20 years) has a welded crank because all the pipefitter/welders I grew up around and my whole family but me(even my little brother) are licensed master plumbers. So you have more money than time to work and play with all your toys. So to avoid the I am a craftsman and you need to do it right the first time and use good stuff to cut down on call backs and Incidental Damage speech. I should have look before I typed on that one.