Apeiron

That's almost what you're doing with a cutting torch.

spurgeon76

The limitng factors in Top fuel classes is going to eventally be the drivers themselves. The force put on the body for 4.5 sec run is bad enough but if/when they break into the 3's there is a good chance of the drivere passing out on launch.

Batass

I actually heard its more force caused by the parachute. Some guy had eyeball problems.

Might not have been more G's but worse for your body.

383backinblack

its called "eyeballs out" as as opposed to the launch which is "eyeballs in"

and the human body is more tolerant of "eyeballs in"......eyeballs out can cause all sorts of problems like detached retinas etc

spurgeon76

It's also called negative G's, I think.

383backinblack

technically no, negative g's are in the "up" direction, as g-force by definition is going down.....

whether it be forward, backward, etc......its all just a directional force.....just depends which way your nose is pointing.

i know what you mean though

spurgeon76

Nope they do pull negatice G's

http://www.goarmy.com/racing/nhra_top_fuel_dragster.jsp

check it out.

Apeiron

The "negative" just indicates a direction in a particular context. You could just as correctly say it pulls negative Gs off the start line and positive Gs while braking, but that's not the convention. In the context of aircraft, a positive G is a force away from the pilot's head and a negative G is a force towards it.

bl85c

iTrader: (2)

In layman's terms it's the force of acceleration (or deceleration). The 'gravity' term is just a way of equating it to something we're accustomed to.

Most people see diesels as the smoke belching trucks you see driven by a-holes that get a kick out of stabbing the throttle on the highway to cover you in soot. The soot's the result of an overly rich tune, diesels are actually cleaner than gasoline engines.

Diesel engines are heavily overbuilt nowadays, most outlast the vehicle they're made for. Get rid of the extra heft and you've got a serious performer on your hands. No detonation = no limit on boost or c/r (except the strength of the engine itself). The main limit for diesels is fuel control. Injector technology just isn't advanced enough to give diesels the precise fuel control they need at 6k+ rpm.

383backinblack

what apeiron said.....

in conventional terms a "negative" g force is up........

sort of like how there really is NO SUCH THING as deceleration in physics terminology, just acceleration in the opposite direction.

Shagwell

methanol and turbos vs methanol and a blower is a battle that's still waging. believe me, I'm part of it.....

There are blown alcohol classes running in the NHRA, dragster and funny car. Thats where this discussion has a solid example - injected(non-blown) nitro motors are commonly running faster than the blown methanol cars.

Theres a diesel truck that has been covered by many magazines and websites. - IIRC - 96 Ford 4wd F350 crewcab(not dualie), lifted on 38" mud tires, cummins powered, runs 10.80's on 160psi of boost. - Anyone read the caption in the new hot rod about the diesel drag races held recently? Duramax pickup on 35" all terrains towing a trailer with a skid steer and running considerably faster than our cars did stock.....wow. Basically he could pull 4 of our cars on a trailer and run faster than any of them(stock anyway).


For now, nitro can't be beat, but it's hard to say what the future will hold. - BTW they used-to regularily go beyond "almost" hydrolocking. Look into some older drag racing.

Uglybronco

iTrader: (2)

I love your wording for that... Just plain awesome... Oh & 383backinblack 10 points for your use of the older Car Craft logo for your avatar thingy...

& yea, yea, diesels are doing this & doing that lately but they still sound & smell like poo. I'll stick with using that for equipment fuel & just go throw a couple turbos on my gas motors.

But anyway, YAY for going fast no matter how you do it!!!

Batass

Why does methanol require less oxygen to burn than gas? I was trying to find the stoich ratio of diesel, but apparently its constantly changing in the engine depending on load. Very confusing. But its much higher than gas, more air to fuel.

Lets say you had two engines, one on methanol, and one on gas. If you threw equal amounts of the fuel into each and could adjust the oxygen entered to create the optimal stoich ratio, wouldnt the gasoline engine make more power? If all things were equal, and ignoring the cooling and octane of methanol.
BTUs are heat energy right? If Im right in my thinking here, you could make more power from gasoline than nitromethane adding equal amounts of the fuel to the cylinder, if you could get the oxygen content high enough for the gasoline to be at stoich.

Apeiron

Methanol is a small molecule with few atoms, so it doesn't take many oxygen molecules to react with them.

2 CH3OH + 3 O2 → 2 CO2 + 4 H2O

Gasoline is a collection of different sorts of molecules, all of them much larger, which need more oxygen molecules to fully decompose them. Isooctane, for instance:

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
----------
More or less, but engines don't run on fuel, they run on air. Having enough fuel is never a problem, having enough air always is.

a/fool

gale banks had a turbo top fuel car in the late '80's
it didn't sound like your normal top fuel car.

Batass

So really, on the same sized engine, a diesel engine on nitrous should make more power than a gasoline engine. All things the same, I was reading about turbo diesels and nitrous. It seems a diesel revolution is in effect....if they could just get the weight down. I havent quite found why they are hard to rev yet...

bl85c

iTrader: (2)

I believe stoich for diesel is pretty close to gasoline. 14.5 maybe? The reason diesels are constantly changing the AFR is because they "throttle" off fuel. They don't have a mechanical throttle to limit airflow, they're wot all the time. They only take in as much air as the engine can at that rpm. Another reason rpm range is limited on so many.

Not trying to get off subject, I just find diesels facinating.

Batass

I dont really think theres a set subject anymore. This thread started talking about turbo top fuel cars. lol.
I dont think it is the same stoich as gas. It has to be higher than that. I read its around 60-100:1 at idle, but thats lean. I dont think gas will even run higher than 25. If I had to guess Id stay stoich was between 20-30. Figuring with the higher mpg plus the higher weight of trucks.

I need more money and more garages so I can start playing with diesel.

Sonix

iTrader: (1)

Diesels (CI engines for that matter) operate totally different. Excess air, all the time. So it's EASY to get a lot more power, just get closer to stoich. The problem is you're PUKING out massive amounts of exhaust. That's why the diesels engines are so far overengineered, they have to meet emissions standards. So they boost it like crazy and keep fuel usage low. That's fine and dandy, but it doesn't take a genius to note that if you simply dump in more fuel the power is going to skyrocket. Whoo, 200 extra HP with a chip, all it does is bump up the fuel. You can do a smokeshow and not even know if it's from your tires or your exhaust.
Anyway, we WERE talking about spark ignited engines and turbo's, not diesel....

You can have ultra lean spark ignited engines (32:1 for example) using non-homogenous ie. stratified combustion. Pre-chamber, etc. Granted this isn't gasoline, but natural gas industrial engines (example, Waukesha AT model) runs ultra lean at 2.0-lambda, 32:1 AFR. With a ton of boost and 5,000 HP.

Apeiron

A diesel's mixture isn't stoichiometric, they work on a different principle.

a/fool

a nitro engine works a lot like a diesel also. i know. 1.7...but thats not always true. nitro works off of compression, and it needs a load. and it works quite well with turbos, there are plenty of LSR that use nitro/turbo, and gale banks used that combo in the late 80's, too bad it was shelved before the combo reached it's potential. now it is not legal in nhra top fuel.

Shagwell

if it could be proven to maintain atleast the same level of safety, they'd let 'em play. - That leaves it up the experimental guys to make enough power at it to try to introduce it. - Look at it this way, blown alcohol used-to ony be allowed blown alcohol, now they're allowed injected nitro and they run faster doing it.

Yes, diesel is throttled by fuel, not air, therefore it does not use the same principals as stoichiometric. Diesel is a very slow burning fuel, which is why it takes less of it to maintain a certain powerlevel. Lets see a gas motor stay together with 17:1 compression and 100+ psi of boost....not as big of boom as those air force guys, but still fun to watch(if it's not your own). - Diesels don't rev overly high because the injector technology still isn't advanced enough for much(if any) over 6k.

"stoich" for methanol is around 6:1 - we burn about 4 gallons between a short burn-out and one 1/8 mile pass. If we need a little more power, we add a little water to the fuel - makes more power right up till the point it goes boom. It's been long said that in an ideal run the motor would melt all 8 pistons as it goes through the traps. If it did, it was making as much hp as possible.

Batass

Do top fuel cars use aluminum pistons and steel sleeves? Why not use titanium?

a/fool

yes, the pistons are coated from J&E, i don't know what it is, they just come that way. titanium would melt quicker unless you can treat it. the exhaust valves are titanium, but they are filled with inconhal.

Batass

Melt quicker? I thought they had a high heat resistance. When I was in the Air Force the jets used a lot of titanium in the afterburners and for the exhaust nozzle. They may have had a coating on them, but I dont remember. We used a lot of strange things and chemicals, that I've heard are illegal or impossible to get outside the military. Lots of cancerous stuff......

Apeiron

Titanium doesn't melt until 3000+F, but it's highly reactive and burns easily, even in a pure nitrogen atmostphere.

bl85c

iTrader: (2)

And there's the problem of it galling against other metals. Titanium's a strange substance, it likes to 'stick' to other metals unless it's coated with something. Infact it fuses with bone, which is why it's common in the medical field.

Shagwell

it's also very brittle. - that's why I've stayed away from it for valves.
blowers and nitro bang - the threshold of disaster would be much smaller than it is now.