Please Comment of Speed Secret # 2

[jim_howard_pdx]

Speed Secret # 2:

Again everyone. I am not purporting that this is the "best" speed secret you will ever hear. Or that this speed secret will even be important to your contribution to motorsports. I am simply offering up some pieces of information to serve as discussion points. To make us all think, reflect, and absorb some options to make us all faster and safer as we blister the roads and highways across the world.

Yesterday I wrote about squish and quench and wedge and flame propogation. My feeling is that you have to start from where HORSEPOWER is made. That would be the preignition and flame propogation in the combustion chamber of your engine. NO SINGLE ITEM IN YOUR HOTROD BAG OF TRICKS CAN OVERCOME SHORTCOMINGS IN THE BURN CYCLE.

Several of you saw my points and hinted at oppositing opinions that are abundant in the racing world. Like how things have changed between pop-up domed pistons, flat top pistons, or dished pistons. One person mentioned that modern combustion chambers are made to swirl the air fuel mixture as it enters and as it compresses. That the idea was to get a good homologous fuel charge so that the flame propogation would be smooth and steady as it ran from the spark kernal all the way to the pistons edge.

Really good stuff and all absolutely correct.

HOWEVER, you all need to sit back and realize that whatever you do to whatever engine you build, that it is the preignition and flame propogation that makes or breaks the horsepower your engine delivers. The quench and combustion chamber is where the game is won or lost. PERIOD END OF STORY.

If we keep quench tight, reduce the amount of wedge area to what is optimal to the best burn, then we make more horsepower. If we have jagged ragged pop up pistons that have ridges hills and valleys for the flame to cross, you will loose power. So what we did to run a 9 bracket was to take the pop up, make it a 0.10 fit to the wedge (after reducing the wedge volume, then make it all smooth as a babys butt retaining the stock combustion chamber cc volume to satisfy tech inspection. We used stock heads, stock rods and stock pistons and massaged them to make better burn.

I will share one last point to speed secret number one that I was really hoping one of you would jump on. Swirl. Modern engine builders use flat tops, and let the new heads make the swirl. Back in my day, I not only modified the domed piston to get my quench, but I modified the dome, to swirl the compressing fuel back into the sweet spot for the preignition.

No one grabbed that point. I was counting on YOU TO THINK THIS THROUGH AND POINT IT OUT. All NASCAR builders worth a damn are using piston shape to effect swirl to compressed quench. So if you ever get the chance to see a world record engine tech inspected BE THERE. YOU WILL LEARN ALOT FOR YOUR EFFORT.

So now as you read speed secret # 2 remember that I WANT YOUR COMMENTS. I want you to think the topic through and say "what about this", "what about that", and "what about the other thing"......

So here is speed secret # 2. A Z06 Corvette makes 400 hp. 315 to 330 of it makes it to the rear wheels. The Corvette is making 70 horsepower per liter. Why is it that most Honda VTech engines are making 100 horsepower per liter, and can cross the quarter mile faster than the Z06 with just a 1.8 to 2.2 liter engine?

That's quite a question for you to digest.

A Z06 Corvette does the quarter mile in 12.7 to 13.3 seconds. Pretty d a m n quick if that is what you are used to. But a buddies stock Honda CRX with a 1.8 liter FACTORY ORIGINAL Acura Integra R engine, a set of headers, 2.5 open pipe, no muffler and a stock honda 5 speed with racing clutch quarters in 12.4 seconds. No gimmicks. No engine work, No NOS, No trick intakes, No modified injectors, No custom computer, Nothing that did not come stock on that ol Integra. So why did that Honda beat up on the Z06?

I want your comments. PLEASE

Here is my speed secret #2. Reduce your parasitic horsepower loss, and you will improve your ET's. When we were racing in the 10's we had almost 600 flywheel horsepower and almost 700 ft lbs of torque from our trustworthy 428 super cobra jet engine. We started our campaign at a 10.2 bracket. Within two months the same engine the same transmission ran a 9.2. Tuning was the same, compression was the same, intake and exhaust was the same. We did add 4" to the tunnel ram, but that only got us .05 ET. Basically only one thing changed. We reduced the parasitic horsepower loss.

What did we do.....

Parasitic horsepower losses are the torque and horsepower lost transferring the rotational energy at the flexplate or flywheel to the bite on your tires.

We could not reduce the weight of the C-6 internals without lowering its torque capacity. So eliminating parasitic loss in the rotating pieces of the transmission was determined to be foolish. We could have shaved the drums, tried custom light weight alloy drums, but this is a quarter mile car. So what works for us at Bonneville, does not work at the drag strip.
So we moved on in our quest for better ETs.

The drive shaft. We decided on using a graphite drive shaft. I knew a company making graphite tubes for missle bodies and had them send us some units. We had to sign non disclosure agreements, and underwent an FBI security check before they would release the tubes. Then they would only send us the rejects. Man we never did see any imperfections. They used sonic and x-rays energy to check these. Remember a missle body accelerates to about MACH 4, so these have to be right on the mark.

My buddy at Rockwell supplied some epoxy (the stuff they use on the Space Shuttle). We glued the yoke ends to the graphite shaft on one end and balanced it with just the front yoke pressed on. Then we slathered silicone RTV on to a thin wall aluminum tube and pressed it into the graphite tube to provide laminate torsional energy strength. We were counting on the balancer to spin our epoxy and silicone into balance and it worked. Then we did the other end and balanced again. Now when a shop balances a drive shaft, ask then what rpm they balance at. Most shops balance at the RPM your engine turns at say 70 mph. We balanced ours at the highest RPM we could achieve. It really makes a difference.

We put the new driveshaft in and turned a 9.94 ET .26 et from a driveshaft? It is not just the weight that kills your horsepower. It is also the harmonics, vibration, and any imbalance. All those things translate to LOST power. Reduce the vibration and the harmonics and you gain horsepower. We used graphite not because it was lighter than aluminum. We could have used titanium and it would have been just as light as graphite. We chose graphite because it ABSORBS harmonic energy better than aluminum or titanium. The expanded foam material was to dampen the torsional energy stored by the silicone between the carbon and the aluminum. We had to show the tech guys the balance records to run the shaft at some brackets.

Next came the pumpkin. We wanted to use an aluminum Strange 3rd member to reduce weight. But the great guys at Hoopers rear end exchange told us it would be really hard on the wear patterns of the gears. Now having a gear wear out a little early was not our concern. Why did we stay nodular? Because if the case flexes and the gears run off line, then the missaligned gears scrub horsepower and inject harmonics and vibration back to the shaft and out to the axles. Do not sacrafice HORSPOWER for weight. Only lose weight if it improves ET's.

Still, our goal was to reduce the weight in the rotating assembly of the rear end. We refused to run smaller bearings to save weight, The gears had to be drag quality soft steel in order to take the launches (did you know drag gears are soft, and street gears are hardened????). At that point the differential was an open iron case with a mini spool. Worked ok at 10.8 but it was really heavy. So we chose an ultra lightweight aluminum spool designed for circle track racing. We used it oun our Bonneville cars. I cannot remember the grams, but this was about one third the weight of a posi unit, and one third less weight than a lightweight steel racing spool. We never broke the thing, so we were lucky. Luck is a subject for some other time.

Now we have axles. Everyone told us to run 35 spline forged axles. 31 was ok 35 was better. Ever weigh a 35 spline forged axle? Ever weigh a 31 spline forged axle?
We took a 28 spline forged axle before it was heat treated and turned it to make the outer circumference smooth and balanced. Then we drilled out the center section of the axle from the spool side only. We drilled in as far as our bits would allow us. We filled this cavity with our famous epoxy that had saturated random length fiberglass strands. We put the mixture into the hole and pressed it to 4 tons of pressure. When it dried we had the unit heat treated not by an oven but with some special equipment at Rockwell that hardens just the surface of the material. I think Currie Rear Ends uses one of these critters in their plant. Then we coated the surface of the smoothed 28 spline axle with an elastomeric covering used to absorb harmonics and provide just a smidgen of laminate strength to the weakened and lightened axle.

We did break a couple of these axles in testing, but never lost one at a race. No huge deal, we used disk brakes to retain the wheel to the axle. The spool and axles got the car to 9.39 ETs. Then we took the lightest rims we could find, lightened them more, and coated the interior surface with the same proprietary elastomer material. We ran MT crinkle wall slicks.

So a light weight drive shaft, light weight spool, lightened axles, and lightened rims and smaller LIGHTER slicks, turned a 10.2 car to a 9.2 car. You should have seen the difference in the dyno numbers. At 10.2 the rear wheel horsepower was 462. We lost 138 hp through the C-6, Steel drive shaft, heavy differential, heavy axles, and heavy rims. At 9.2 the rear wheel horsepower was 541. Just the reciprocating weight was reduced and we gained back 79 horsepower. Our top speed increased from 126 to 139. ET's went down to 9.2 - 9.3 with excellent consistency.

With NOS we had to run a light steel spool, and we highly modified the 35 spline axles, and used a stronger rim.

So there is my speed secret number two.

If you are at a wall and cannot get faster, get lighter with everything that delivers the crankshaft energy to the slicks. LIGHT IS RIGHT!

My buddies CRX shows 162 horsepower on the rear wheels and the engine shows 189 horsepower on the engine dyno. He loses just 27 horsepower. This is why that CRX can take a Z06. You might say NO ITS THE WEIGHT. But the CRX with autocross racing braces and cage weighs in at 2495 and then add my buddies weights 195 lbs. 15 pounds per horse. The Corvett is running 10 pounds per horse. So vehicle weight / horsepower is less determinate of ET's than power / parasitic loss.

Just to make everyone out there think even more, a 1.7 liter twin turbo RX7 is campaigning as we speak at the 9 second bracket. Do you still think what you were taught, more horsepower and less vehicle weight is really what makes low ET's. YES AND NO. It is a factor, but not the only factor, and it is not the determinant factor that will get you to the winners circle.

Think about it, challenge it, but by all means I WANT TO HEAR YOUR COMMENTS.
Then go home, and start lightening your reciprocating parts in your engine, your transmission, your drive shaft, your rear end, your rims, and your tires. You will be rewarded with faster times. Remember not to sacrafice safety for weight. When we tested NOS, the track tech would not let us race with the lightened rims. They had to be original NHRA approved rims and tires. SAFETY FIRST!