Lynn E. Hanover

This is carried on into other drive line parts. I seldom see a steel drive shaft anymore. Spun aluminum wheels are the norm. The largest rotating mass that fits

in this is the wheel/tire combination.



When Goodyear moved race tire production to South America, we started running Hoosiers. They last twice as long as Goodyears. Maybe 4 weekends instead of 1 or 2.



However, the Hoosiers are way heavier than the Goodyears. So you cannot go as fast on Hoosiers on a tight track. The disparity is not as obvious on an open faster track.



Goodyear lost market share and got a well deserved black eye over this. They are back in the USA again, and we are back on Goodyears. The fast guys are dropping a grand or two every weekend on tires. We have to worrie about how many weekends we can get out of each set. We do have tire gifted to us from competitors who have tire deals (sponsorships).



Anything that the engine has to spin up should be looked at.





Lynn E. Hanover

heretic

I cannot tell if you are for or against the views i am expressing, but think about spools versus differentials, or Currie's lineup of super-light-weight internals for Ford 9" rearends, or gun-drilled axles, or carbon fiber driveshafts, or expensive steel wheels that meet the letter of the rules that say they must weigh 19 pounds (for safety reasons) but most of that mass is concentrated as close to the hub as possible, or ungodly expensive mini-clutches that are so small they need to have splines in order to keep from slipping (i think the smallest is 4.5")...

89 Rag

I agree to the extent that weight reduction, from the rotating mass aspect, should not be limited simply to the engine. It seemed your view was solely directed at the engine alone which leaves the job only half done. Granted, the cost factor does come into play when applying this to the entire running gear, so, imo these mods are hardly necessary for a daily driver or street/strip type application, from the more bang for your buck point of view.

heretic

Just think. In the transmission, the speed of the countershaft (and the speeds of the outpur gears!) is always in direct relation to engine speed when the clutch is engaged, since the actual gear changing happens on the output shaft.



What if the sliders and everything else were on the countershaft instead? It would mean much less rotating inertia tied to engine speed. Would make a fairly significant difference in the lower gears, little difference in the upper gears where the shaft speed differences are small to nonexistent.

Lynn E. Hanover

The quick change comes with an aluminum spool. We installed a clutch type limited slip on a steel carrier. Its faster because it eliminates understeer in slow corners.



The speedway comes with gun drilled axles. For wheels we have aluminum Centerlines.



Our aluminum drive shaft is so short that the weight advantage for carbon is minimal and the price of the corbon shaft is not in our future.



No minimum weight on wheels so long as steel or aluminum.



We have the 5 1/4" double disc Tilton clutch setup. The flywheel is the same size as the clutch cover.



If we had no engine or drive line mass we could still not be as fast as we need to be. We have about 250HP and the pole sitting RX-7 had about 280HP Thats about 10 MPH at the end of the long straights. We are very much off the pace. We would need light rotors bigger runners, fuel injection, ceramic apex seals, a driver that is not paying for the parts, and shift at 10,400 to have that much power. We can afford none of that. On the other hand we race all year on one engine not one weekend.



Many newer dynos use a time to accelerate a big flywheel as a method to calculate HP. In that case the engine rotating mass counts against you. It acts like a bigger flywheel.



That same engine on a conventional water brake dyno in a steady state measurement would show more power. (By a microscopic amount). The water brake cannot evaluate rotating mass other than the tiny additional bearing drag of the heavier assembly. So, in a race on the steady state dyno, rotating mass matters not. In a race on the track, its a big deal.



I am agreeing with you.





Lynn E. Hanover

j9fd3s

the sliders are pressed onto the countershaft. i'm building 2 transmissions soon, i'll take pics

mike_rudy

Ok well what i should be asking then is will a 12a with MFR PP housings carbon apex seals lightened flywheel , ceramic coated rotors, hardend stationary gears and 3 window bearings be able to rev up past 10 grand for longer periods of time(autocross and a bit of road racing) also is there any other major oil mods to do as in making oil passages bigger ?? i was tod i will need 100 psi oil pressure all the time, Thanks<mike

Lynn E. Hanover

While the countershaft runs at some percentage of the inputshaft speed, it is in the recurrent column and is reaccelerated after each shift. So reducing the countershaft weight pays a bigger dividend than reducing the mainshaft weight.



The main shaft operates at some percentage of ground speed based on rear end ratio, and while it is important to keep it as light as possible, it would not pay as big a dividend as lightening anything in the recurrent column.



A less obvious advantage of lightening all of the driveline parts is that the driveline

then becomes a smaller percentage of the braking load. So the brakes start working better.



You may have a 240HP engine but you also have 1,500 hp brakes. Learn to use them.



Here is my naked race car.



Lynn E. Hanover

Node

Thats awesome.

What is that class called? I've heard of it, Full Tube Chassis'd FDs w/ PPort 12as. insane

Any more info on the class or any other cool bits?

heretic

Very true. Many people never really learn how to brake effectively.



Of course, with less rotating mass attached to the wheels, the brakes can work that much better, if the driver knows how to use them.