Aero on Drag racing cars

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VARIANT | one
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Re: Aero on Drag racing cars

Post by VARIANT | one » Sat Feb 18, 2017 3:58 am

roon wrote:If they were any longer they would begin to resemble F1 cars.
Top Fuel is pretty much a technologically stunted form of motorsport... for safety reasons. What they should do it ditch the nitromethane nonsense, mandate pump gas, and open up the rulebook on just about everything, and let them work their way back up to the current speeds through different tech. Vacuum traction would be awesome to see in drag racing, maybe six drive wheels. It's just --- boring the way it is right now.

biker_ev
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Re: Aero on Drag racing cars

Post by biker_ev » Sun Feb 19, 2017 5:24 pm

Yeah, 3.x seconds at 300+ mph is boring as hell!

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Re: Aero on Drag racing cars

Post by biker_ev » Sun Feb 19, 2017 5:26 pm

I do think restricting the nitro is a good idea though. When they did that back in the day a lot of excitement went away but technology has advanced a lot since then and it would be very interesting to see what would happen. That would also cut costs by a huge amount.

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SteveRacer
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Re: Aero on Drag racing cars

Post by SteveRacer » Sun Feb 19, 2017 11:45 pm

I think they could keep the nitro but take off the superchargers. The "alcohol" version of the nitro cars have run low fives and over 280mph with limited nitro percentage. They could allow a bigger percentage if they think the class would lose its appeal by not being fast enough.

Another option would be to lower the 500 cubic inch rule. It would be interesting to see the teams work hard to make power again.

roon
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Re: Aero on Drag racing cars

Post by roon » Mon Feb 20, 2017 12:54 am

How many RPMs are non-supercharged drag engines pulling these days?

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Re: Aero on Drag racing cars

Post by hpras » Mon Feb 20, 2017 5:28 am

At the start of 2016, the NHRA limited prostock engines to 10500 rpm. In the year before they were in excess of 11000 rpm. Lots of rpms for a 500ci engine.

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Re: Aero on Drag racing cars

Post by SteveRacer » Mon Feb 20, 2017 10:21 pm

I've talked to blown alcohol funny car teams and have heard they can go as high as 11,000 rpm. I don't know about the A Fuel cars.

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Re: Aero on Drag racing cars

Post by J.A.W. » Tue Feb 21, 2017 12:11 am

Bear in mind with this RPM discussion, none of those top fuel beasts actually runs for anywhere near a minute at those rotational speeds...

Its more of a 'flash' reading, or ( semi-controlled) 'runaway' - in engine function terms.
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Re: Aero on Drag racing cars

Post by SteveRacer » Tue Feb 21, 2017 2:53 am

Not sure what you mean by flash, but I think you'd be surprised how little the motor accelerates late into a run. You coming up against some big drag numbers near 300mph.

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Re: Aero on Drag racing cars

Post by biker_ev » Tue Feb 21, 2017 5:20 am

I think he means that total engine rpm is only several hundred, perhaps 700 doing the burnout.

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Re: Aero on Drag racing cars

Post by biker_ev » Tue Feb 21, 2017 5:21 am

That should be "including" the burnout...

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Re: Aero on Drag racing cars

Post by roon » Tue Feb 21, 2017 6:00 am

I started wondering how fast Top Fuel engines would have to spin sans pressure charging. I see numbers in the 3k - 4k CFM range for their SCs, although I haven't validated those claims. A 500ci NA 4-stroke would need to operate in the 21k - 28k RPM range to move similar amounts of air. Which would probably sound amazing. 8) I wonder if there is any precedent for reciprocating parts of this size range operating at such speeds. Such figures are more familiar to F1, 2-strokes & tiny RC model engines. The pistons would be lighter by nature of coping with lower cylinder pressures. It seems TF currently operate at around 8k RPM & 4.5 Bars, for comparison.

Brian Coat
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Re: Aero on Drag racing cars

Post by Brian Coat » Tue Feb 21, 2017 6:59 am

Unfortunately we cannot rev a big bore nitro motor like that, the combustion is too slow, especially unblown.

E.g. A 430 cu in unblown nitro engine (TAD) makes about 4000 hp at only circa 6200 rpm.

The nitro percentage is slightly higher than in TF (94% vs 90%).

Pity: I agree it would sound great!

Following the rpm limits in pro stock, TAFC and Comp Eliminator have highest revs, both in 10,500 to 11,000 range.

It's true that duration at these RPMs is very limited but this is sensible given the race format and regulations.

The piston speeds in TAFC are way above anything F1 has ever used.

This year, I'm pretty sure the fastest blown cars will hit 300 mph in 2.x seconds.

But that does not mean the engines are high tech :lol:

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Re: Aero on Drag racing cars

Post by roon » Tue Feb 21, 2017 3:05 pm

Would the workaround not be: multiple ignition points spanning the combustion chamber? Seemingly F1's 3.0L V10 bore & stroke was small enough to still work with combustion rates. Which would tell us something about minimum distances between ignition areas. I'd call this series TF-1.

Another workaround for a non-SC Top Fuel may be onboard oxidizer, in addition to the fuel. Depending on oxygen content, or just use LOX, you could even eliminate the intake system. No intake valves. Only exhaust valves & injectors. Sixteen fat fire breathing headers coming out of the engine, with eight of them in the vee. Call them Rocket Fuelers.

Such an engine could operate as a two-stroke, which might help with reducing required engine speeds. A four-stroke might still be desirable for cooling the cylinder. If LH & LOx are used, perhaps resultant water vapor combustion products are sufficient to keep the cylinder cool.

When all atmospheric inert gases are removed from the combustion chamber, as found in air-breathing ICEs, how would this alter cylinder design? Fuel & oxidizer only. Detonation will be a major concern, so staged injection into cylinder might be a requirement—direct injection systems. A portion of inert combustion products would be retained per cycle—how much would be a question of design.

I would also recommend to point all the headers backwards, combined into a common plenum with a flameholder installed to flow a portion of the fuel & oxidizer, for increasing the thrust of the exhaust with an afterburner effect. An aircraft carrier type jet blast deflector may need to be installed before hosting Rocket Fueler events. 8)

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Re: Aero on Drag racing cars

Post by Brian Coat » Tue Feb 21, 2017 6:54 pm

Well, Mr. Roon, as on the F1 engines you have some creative good ideas.

Interestingly, "them good ole drag racing boys" already did some of them.

Multiple ignition points: 2 plugs/cyl are standard, for this very reason. And the twin magnetos resemble rotating arc welders.

More oxygen :mrgreen: : CH3NO2, contains a heck of a lot this, which is why they use it. It is actually a monopropellant (a.k.a. rocket fuel). Adding something like LOX or NOx to this would probably get banned on safety grounds (as was hydrazine [ulp!!]) The unblown fuel engines are already very hairy and cannot be started on nitro because they run a high (for nitro) compression ratio. I once saw someone attempt to start an unblown fueler on nitro. There was a loud explosion and it split the engine in halflike a walnut.

Exhaust thrust: This is a very live topic in fuel racing at the moment, the key is to get the right balance between thrust off the line and downforce, which is influence by the header 'lay down' angle.

Keep that creativity coming!