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Drag racing

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Joined: 13 Jul 2003
Posts: 96
Location: Canberra, Australia

PostPosted: Thu Nov 24, 2005 22:10    Post subject: Drag racing Reply with quote

Some people have questioned the engineering validity of drag racing. Here is an interesting e-mail I received ages ago.
And, yes, I did reply to it with the "one second in the life of a reno racer" article.

Sorry I can't verify the source, but most of the numbers add up for me.
Just thought I'd slip it in since drag racing had come up....


One Top Fuel dragster 500 cubic inch Hemi engine makes more horsepower than the first 4 rows at the Daytona 500.
Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro methane per second; a fully loaded 747 consumes jet fuel at the same rate with 25% less energy being produced.
A stock Dodge Hemi V8 engine cannot produce enough power to drive the dragster supercharger.
With 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into a near-solid form before ignition. Cylinders run on the verge of hydraulic lock at full throttle.
At the stoichiometric (stoichiometry: methodology and technology by which quantities of reactants and products in chemical reactions are determined) 1.7:1 air/fuel mixture for nitro methane the flame front temperature measures 7050 degrees F.
Nitro methane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapour by the searing exhaust gases.
Dual magnetos supply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

Spark plug electrodes are totally consumed during a pass. After Ĺ way, the engine is dieseling from compression plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting the fuel flow.
If spark momentarily fails early in the run, unburned nitro builds up in the affected cylinders and then explodes with sufficient force to blow cylinder heads off the block in pieces or split the block in half.
In order to exceed 300 mph in 4.5 seconds dragsters must accelerate an average of over 4G's. In order to reach 200 mph well before half-track, the launch acceleration approaches 8G's.
Dragsters reach over 300 miles per hour before you have completed reading this sentence.
Top Fuel Engines turn approximately 540 revolutions from light to light!
Including the burnout the engine must only survive 900 revolutions under load.
The redline is actually quite high at 9500rpm.

The Bottom Line; Assuming all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs an estimated $1,000.00 per second.
The current Top Fuel dragster elapsed time record is 4.441 seconds for the quarter mile (10/05/03, Tony Schumacher). The top speed record is 333.00 mph. (533 km/h) as measured over the last 66' of the run (09/28/03 Doug Kalitta).

Putting all of this into perspective: You are driving the average $140,000 Lingenfelter "twin-turbo" powered Corvette Z06. Over a mile up the road, a Top Fuel dragster is staged and ready to launch down a quarter mile strip as you pass. You have the advantage of a flying start. You run the 'Vette hard up through the gears and blast across the starting line and past the dragster at an honest 200 mph.
The 'tree' goes green for both of you at that moment. The dragster launches and starts after you. You keep your foot down hard, but you hear an incredibly brutal whine that sears your eardrums and within 3 seconds the dragster catches and passes you. He beats you to the finish line, a quarter mile away from where you just passed him.
Think about it, from a standing start, the dragster had spotted you 200 mph and not only caught, but nearly blasted you off the road when he passed you within a mere 1320 foot long race course.
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Joined: 26 May 2004
Posts: 56
Location: Portland, Oregon

PostPosted: Sat Nov 26, 2005 00:55    Post subject: Reply with quote

Sums up what is like to be around a Fuel motor;) The redline rpm seems high, though. I always figured we topped out at around 7000rpm. Fuel motors seem to run more like a diesel, than a gas engine, they don't like excessively high rpm. Maybe the modern engines are different, but the ones I worked on back in the late 70's seemed to not respond well when guys would try to use an intentionaly higher rpm than normal. You have to remember that you are pushing a 2-1/4 inch stainless steel intake valve, using 850 lb/in springs. Valve harmonics were not too well controlled anyway, so at higher than normal rpm the valve train would destroy itself in a hurry. The scariest thing that would happen, is when the engine would pull fuel past the shutoff, and you could'nt shut it down. A runaway fuel motor is a fearsome thing indeed, especially on a Funny Car, where it has a centrifugally operated clutch. One interesting experiement I was told about was to determine how much power a 8-71 roots blower spinning at 30% over crank rpm took. The guys took an 1100hp Offy engine, and used it to drive the blower. It could'nt drive the blower to the equivelent of 6500 crankshaft rpm! This is what sold me on the concept of replacing the blower with nitrous oxide, and running methanol. But I couldn't get anyone to fund the idea - it wasn't how they had done it for the last 300 years.
It runs best just before it blows!
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Joined: 13 Jul 2003
Posts: 96
Location: Canberra, Australia

PostPosted: Sun Nov 27, 2005 23:30    Post subject: Reply with quote

My understanding is that some teams have made up their own 4 valve heads with OHC. Perhaps they're the engines the author gets the 9500 figure from.
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Joined: 26 May 2004
Posts: 56
Location: Portland, Oregon

PostPosted: Mon Nov 28, 2005 01:39    Post subject: Reply with quote

My sense was that it was not a valve train limited phenomenom, where a OHC multi valve setup would help. The valve train had serious issues without a doubt, but it seemed more like a consequence of the extremely slow burning of nitromethane. Remember, with a manifold pressure of 45 psi ( absolute) we were running ignition advance of 70 btdc. One of the fastest guys around at that time, experimented with running a 3.73 rear end ratio, when 3.9 to 4.1 was considered the norm. The car gained 3mph, seemed to launch harder, and definately "cleaned up" faster out of the hole. It definatly seemed to like the lower rpm, and this was on an engine that did not lack from having the best parts, unlike the engines I was tuning.It seemed to be a fundamental characteristic of the combustion process with nitro.
It runs best just before it blows!
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PostPosted: Wed Dec 07, 2005 14:49    Post subject: McGee Engine Reply with quote

There is a company here in Sydney called McGee Engineering. They built four valve per cylinder dohc fuel engines for power boats and later drag boats. They reduced the valve count to three per cylinder for their definative engine design. They did this to avoid an erosion problem they encountered. The bridge area between the exhaust valves in the four valve engine would overheat and the aluminium in this area of the combustion chamber would be burnt away. By running a single exhaust valve instead of a pair the trouble was avoided. Two spark plugs per cylinder were utilised.

Benefits of both designs included revised valve timing (less duration and lift) and the ability to attain higher rpm. This was an advantage (or would have been) in allowing higher trap speed with the same final gearing as being used previously (in Top Fuel there is no "gearbox"' only a clutch pack and a "diff" with a fixed reduction ratio and no differential action). Data capture from McGee engined dragsters shows strong acceleration continuing throughout the back half of the quater mile. This characteristic of the McGee was markedly superior to conventional Top Fuel engines.

As can be readily appreciated the McGee engines could be configured for land based applications. It wasn't long before they turned up in drag racing. Eventually they appeared in Top Fuel. It was a big deal for this modest family company to put a team together and head for the USA to demonstrate their engine in the heat of competition. They raised much interest. Eventually the McGee engines were tested by the Bernstein Organisation and other leading teams in US Top Fuel scene. The idea was for the McGees to supply engines and components to the teams, not to race cars themselves. The engine showed much early promise (cheaper to operate, less component breakage, many components were cheaper) but after about three years they were banned by the rule makers. This was back in the late 1990s.

Rules were revised to specify that Top Fuel engines must be sourced from US suppliers exclusively (there is a list of approved suppliers). Later revisions require Top Fuel engines to conform to the traditional "hemi" archictecture (two valves per cylinder, single cam in block). The McGees were disappointed. Their engine was originally eliminated in a move to keep the "sport" American and of course the McGees are Australian. They have since found their efforts to compete in the US completely frustrated (they have several other clever improvements available to them, including some for two valve single cam in block engines). Who said racing improves the breed?

McGee still compete in Australia. They remain active supplying drag boats. As for supplying engines for race cars down under, there are issues (US generated!).
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Joined: 26 May 2004
Posts: 56
Location: Portland, Oregon

PostPosted: Thu Dec 08, 2005 17:11    Post subject: Reply with quote

This most unfortunate information does not suprise me. There is a small group of people who wield power in the NHRA and their aim is to benefit themselves, not the sport. In general, these are the guys who are the equipment manufacturers - want to guess which equipment is on the approved list? Drag racing used to be where the little guy could come up with engineering advances, and surprise the big money guys. It was the reason I quit, when it became apparent that NHRA was going to decide who won before the race occured. As a result, I haven't been near a race track since 1980 and couldn't care less. I did love the Australian spectators, though, to come that far to see a race - their enthusiasm was contagious!
It runs best just before it blows!
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Joined: 23 Sep 2011
Posts: 14
Location: Central New York

PostPosted: Mon Oct 03, 2011 00:57    Post subject: Reply with quote

I have always loved this too, My pal Billl sent me it again, recently. However, there are some inaccuracies. Here is [about] what I sent back. I'm no expert so let me know if I have made any mistakes.

1.) "a fully loaded 747 consumes jet fuel at the same rate with 25% less energy"?? Using the figure provided a top fuel car using 1-1/2 gal/sec, the race being, say, 4.5sec long, and 4 races to make 1 mile, the fuel economy works out to 27gals/mile.

The wiki says the 747-100, can carry 48,445 gal and range is 5,300nm (~6,090miles). That works out to 7.95 gal/mile.

It is hard to say if the wiki plane has a reserve or if that is loaded or empty. The latter is worth about +/-20%. Gas and kero have about the same BTU (114k/gal vs 128k/gal). Nitro lower, more than 50% lower (47k/gal), but has a 1:1.7 A/F so there is more fuel (with O2) and less added air. It all works out to nitro has about 2.3x more heat for a given amount of air. Anyways, the car is a gas hog, much more so when you figure fuel/passenger miles.

As for power output the current top fuel cars make about 8,000hp. The figures for the jet engines vary, and can be misleading because shaft HP is different than thrust, Two articles grabbed from Google (links below), have the four 747-200ís engines at 87,325hp during cruise, The second claims 120,000hp takeoff and 60,000hp cruise.

So the point here is the 747 uses a lot less fuel and makes a lot more power.

2.) The redline may be 9,500 but engines do not run that fast after the burnout. Current top fuel cars max out at about 8,200 thru the traps, 1,000 rpm lower at mid track as the clutch comes in. Granted this article is 5y old ,The race today is 1000ft, and the gearing is restricted. I canít say if that has changed over the years.

3.) "Then explodes with sufficient force to blow cylinder heads off..."?? Wrong. If the spark plug fails to ignite the cylinder hydraulic locks and breaks block/head/gasket... Massive fuel is released -afterwards-. This is what does the 'exploding'. In other words the engine grenades mechanically, then there is a big fireball.

4.) Nitroís flame front is only about 4,350 įF (there is also some serious evaporative cooling).

5.) Fuel mix near solid? I think not. It is a liquid and air, neither come close to becoming a solid. It is "almost at hydro-static lock" by nature because the the A/F ratio is 1:1.7. The words 'almost and near are rather vague/ misleading here, BTW liquid air freezes at approximately -355*F. If you confined it and warmed it to room temp the pressure would be astronomical (many millions of atmospheres??)


Photos below are a top fuel piston I found in Kenny Bernstein's trash can (after the race) about 10y ago. Some observations-

-Teflon coatings
-gap-less ring
-huge intake valve diameter
-huge wrist pin diameter
-tiny exhaust valve
-crushed crown, probably due to too much fuel in the chamber
-pin retainers are buttons, like some areo engines
-massive pin boss area making for a very heavy piston
-Alcoa/JE markings
-almost no skirt wear
-pin bore cuts into 2nd ring land
-piston makes about 1,000 hp

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