A different formula, Taxable Horsepower

[Mike Kellner]

Way back in the dawn of automotive development, the Brits taxed automobiles on the basis of Taxable Horsepower, which they derived from the total area of the combined cylinder bores in a car's engine. The theory behind it is simple, an engine is an air pump and the larger the total valve area, the more air it can pump.

What if we take that concept and use it to regulate racecar motors? Rather than specifying displacement and/or cylinders, simply set the total bore area allowed. I am sure engineers can come up with the right size to put power in the ballpark required, and then everyone will be free to decide the configuration that squeezes the most power from that amount of valve area. They might find that relativly slow turning V6s or V8s will produce more power from a lighter package, once you take away the lotsa cylinders motor's advantage of increased valve area. You could lengthen the stroke, which would reduce max revs, but would produce the same power. Also fewer large cylinders would have the advantage of less friction and more air will flow through a smaller number of valves of equal total area. The difference between a garden hose and a bundle of cocktail straws.

I suspect such a formula would favor longer stroke, slower turning motors with fewer cylinders. I would also propose a requirement that steel, iron and aluminium be the only allowable materials other than for gaskets. I think this combination would cut the advantage of big money motor programs while still preserving a healthy competition among engine builders and allow for a diverse set of motors to compete on a more or less equal footing.

[DaveL]

Originally posted by Mike Kellner
I think this combination would cut the advantage of big money motor programs while still preserving a healthy competition among engine builders and allow for a diverse set of motors to compete on a more or less equal footing.

I don't see any diversity coming from it. Engineeers who are all working to try to solve the same problem will end up with the same answers. Once the best possible configuration is confirmed, that's what everyone will build. And once everyone is building the same thing, whoever has the most money to come up with best variations on the theme will win.

If the history of racing has taught us anything, it's that everyone will copy what is winning, and whoever has the most money to make the best copies will win.

[Mike Kellner]

Yes, but if an 8000 RPM 5 liter long stroke V8 is the optimum motor, wouldn't that reduce the cost of poker by eleminating the race to 20,000 RPM? I'm using the theory that a Moon race is less expensive than a Mars race. Eleminating fancy new materials would hold everyone to configuration, valve timing and combustion chamber shape as the main arena of competition. I think you are right that diversity would disappear as the optimum layout was found. It might end up with motors closer to what car companies build, so they might be more interested.

[DaveL]

I now see your point Mike and do not disagree.

[Peter Olivola]

Why repeat history? Metalurgy has advanced far beyond the point where building race engines to such a formula made sense. Not all the advances carry a cost penalty. This would have the effect of putting race engines behind street engines in virtually every way. You'd see SCCA Club Racing Improved Touring engines that were more effecient, delivering more power per cubic inch and better fuel economy. Not a recipe for a tier one racing series.

[chop456]

What equivalency formula was used in the IMSA GTP days?

[Napoleon]

Originally posted by Mike Kellner
It might end up with motors closer to what car companies build, so they might be more interested.

I understand all the points you are making, but why not simply mandate displacement and cylinders to get you to an engine that is closer to what they car companies build to get them interested. It seems a little "Rube Goldbergish" to mandate total bore knowing that ultimately some basic design will be optimal, without quit knowing what that will be and whether it maybe of an interest to manufacturers.

[ChrisB]

This is essentially an "open engine spec vs tight engine spec" debate.

As we saw in the "why is F1 using a V10" thread, once the "sweet spot" is found, everyone uses it... so you might as well pick one config that's close to what you want and mandate it. CanAm and IMSA GTP are good examples of what happens with open specs with equivalency rules.

I say just do a tight engine spec, but one that has so much friggin' power beyond what the tires can put down that working to find a few more ponies would hardly matter.

[DaveL]

Originally posted by chop456
What equivalency formula was used in the IMSA GTP days?

Most had to do with overall car weight and restrictions on the size of the air inlet.

[Mike Kellner]

All formula attempt to control power by limiting the amount of air that flows through the motor. This is just another way to do the same thing. I am just speculating that it might produce a lower cost optimum motor. If the ultimate motor for that spec would be a 5 or 6 liter V8 developed with a CART budget, you would end up with a 750 HP 250 Lb DOHC 4 Valve aluminum motor of about 250 Lbs. Not exactly a passenger car motor. It would be a lot less costly to buy into that spec than one where the standard motor is a 19,000 RPM 850 HP DHOC 4 Valve V10 that weighs 210 lb. I was figuring 600 cm^2 for a bore area which gives a 9.77 Cm bore for a V8. If you could run any stroke you want in that motor, why not run a 9.77 stroke too. That gives 5.8 liters. I bet you'd have a great street and road racing motor with a wide bandwidth and a 8000 - 9000 RPM redline. The lower revs would allow a simpler, lighter valve gear.

Anyway, it's just a diversion for a cold winter's day with not much racing to talk about.

[formulaben]

Why not just keep what we have now? I see absolutely nothing wrong with it, except that maybe Ford isn't completely flipping the bill, whereas before, there were Toyota, Honda, and Ford teams getting engines for free while the lesser teams were paying for them, further complicating their rise in the ranks. Given the state of the racing series right now, and the state of the economy, it makes perfect sense to think about keeping things the way they are. Maybe I'll be proven wrong in a few months, but I think we'll be pleasantly surprised by the relliability of the new Ford powerplant, and the parity of the racing. Sure, it's gravitated a little more towards F3000, but I've been watching it, and I like it. It certainly beats some of the "shows" that F1 has been putting on.

[Napoleon]

Originally posted by formulaben
Why not just keep what we have now?

The current formula has outlived (by several years) as viable as a formula in which you could allow open competition. Afterall they were to the point were they were using almost no real boast. It may work fine as a spec motor but if CART is to have more then one manufacturer in the future it will have to revise the formula.

[Peter Venkman]

I'm not sure that just limiting the inlet area would do the same thing.

Stuff in... efficiency of combustion... power out.

It works pretty good in ALMS, and it still allows degrees of freedom in engine design and configuration.

PV

[formulaben]

When I said "now" I meant for 2003, which is somewhere around 12K RPM or so and much higher boost than 2002. My point is I really don't see how attracting engine manufacturers is so important until they start flipping the bill for race engines and/or sponsoring races. Given that developing engines is very expensive, then why not have a "spec" engine or engine partner and save the teams money, just as a tire company might be a partner when a series does not want a tire war. I'm not so sure an engine war is always a good thing...witness Fontana 2000. I'm looking at what is coming with the new CART and I really think it should be good.