World's Fastest Diesel 1

[Fabrico]

Anyone notice the new Diesel Land Speed Record of 350 mph (563 kph) just set by a Andy Green from England? There's some amazing numbers, including 10.5:1 compression.

http://www.jcbdieselmax.com/html/home.php

 

[ivymike]

That does seem like amazingly low compression (haven't read the whole site). They must not worry much about cold starts or smoke.

 

[TheBlacksmith]

It also says "Twin compound turbochargers with twin compound intercoolers", so it sounds like they have an large amount of boost, making a relatively low compression ratio necessary.

 

[SomptingGuy]

Ricardo calculated that for the speed record attempt, the two engines would require an intake airflow of almost 5 tonnes per hour. Moreover, this would need to be delivered at the 1300m altitude of the Bonneville salt flats, where ambient air pressure is 85% of that at sea level. While the production engine requires a boost pressure of 1bar, the two engines installed in the JCB DIESELMAX require 5.2bar absolute at full power. The scale of this challenge can be appreciated in comparison with around 3 bar absolute for a diesel Le Mans racer, and around 4 bar for the turbo-era Formula One cars.

Hmm, 5.2 Bar, that must give a prety high Pmax!

 

[ivymike]

They don't mention Pmax, eh? Who thinks it's higher than 3000psi (20.7 bar)?

 

[ivymike]

excuse me, 20.7 MPa or 207 bar

 

[sbmar]

Pretty impressive, but keep in mind this is a "one off" situation with loads of R&D and advertising bucks in the budget..Also, life expectency is measurered seconds and not hours.................If you really want to see where #2 is going and where technology has taken diesel, look at the marine pleasure boat diesel market where you will find "in production" diesels pushing 80+ HP per liter and 3 bar (85++" HG, 40+++ PSI) turbo boost.....To me, that's trully impressive..............

Tony

Tony Athens

http://www.sbmar.com

 

[patdaly]

Why didnt they use some boost? I have friends shoving more boost than that to a cummins.

 

[crysta1c1ear]

400 MPH is about 180 m/s.

With a CdA of 0.15 m2 and assuming air density of 1.2 kg/m3, they will be effectively hitting about 0.18 kg of air for every metre travelled.

So every second the JCB hits 0.18*180 = 32.4 kg of air with a kinetic energy of 1/2*m*v*v of (1/2) * 32.4 * 180 * 180 = 524880 Joules.
That is 524 kW required to overcome air resistance.

They are using a 560 kW engine.

So what is holding the thing back from getting to 400 MPH?

 

[globi5]

^ friction is not just caused by air (drivetrain, wheels).
Besides air density at this altitude is probably less than 1.08 kg/m^3 (since it is pretty hot up there it might even reach 1 kg/m^3) and RAM air is already significant at these speeds (over 10% intake pressure increase), so according to your calculation it should even be faster.

 

[kenre]

I would say that wheelspin could enter into that as well.

Very impressive!

Ken

 

[RobWard]

Skin friction, apparently.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[SomptingGuy]

They are using a 560 kW engine.

Nope. They used two of them!

So what is holding the thing back from getting to 400 MPH?

The limiting factor is tyres. They were only rated to 350 mph. The car is faster than its tyres.

For those who want some insight into the engine, try this:

http://www.444-lsr.com/downloads/444-LSR_presentation.pdf

 

[globi5]

Why don't they use the same wheels/tires that they use on the turbine and rocket powered cars? Or is wheel friction not sufficient to drive them? What about all wheel drive then? (After all they have 2 engines.)

 

[Fabrico]

It looks sleek, but it's way on the heavy side. There are 400+ MPH tires around, but perhaps not for that load.

 

[levil]

Most of this vehicles don't use tires at all
just a strong steel wheels
the driver is Andi Green who drove the SSC breaking the sound speed few years ago , he is a pilot in UK army & was chosen for the better training in controlling vehicles with LIFT
. just a tenth of degree of nose going up could
be disaster.

 

[SomptingGuy]

globi5,

You are right about the friction thing - it needs proper tyres. And even so there's apparently some kind of "wheel-spin-ometer" in the cab too to monitor what's going on.

w.r.t. all-wheel drive, it already is. One engine for the front; one for the back.

 

[SomptingGuy]

level,

SSC was an upside-down plane with forward force coming from those jet engines. Dieselmax needed force through it's wheels. Hence the requirement for good tyres.

 

[levil]

The type of the engine isn't relevant to the tyres issue
tyres are limited in their spin velocity .
spin it over the limit and it'll expand by the heat to much and eventually will explode

 

[patprimmer]

levil

Are you seriously suggesting that traction is irrelevant to drive line types where one transmits power through the wheels and one does not, or are you suggesting that there is no difference in the traction of rubber vs steel, or are you suggesting that on a traction limited performance, that traction can be further reduced.

Regards

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