RWD and Global Warming.

[dwightlooi]

If you listen to Al Gore, we have a Global Warming problem. If you listen to the environmental activist lobby its because of companies like GM and people who buy SUVs. Now, GM is being pressured to reconsider its RWD plans because the yelpers and yanters have made Bush propose some rather ambitious CAFE goals -- of course being a Republican President and public enemy #1 to the Liberal media he'll get zero credits for it. Well, there are two issues here. One being Global Warming, the other being RWD and fuel economy. I'll cover them here and if you don't agree with my assessments please feel free to argue about it in this thread.

(1) Global Warming

First let me say that the Earth has been warming up a little since late 1970s. If by Global Warming you are referring to that, then thats fine. However, there is NO SCIENTIFIC EVIDENCE whatsoever, or even convincing lay person reasonings, to suggest that this is abnormal. The Earth goes through countless warming and cooling cycles -- some long, some short, some to a greater extent than others. There is no evidence to suggest that this period of warming is unusual or that we'll not see a reversal in the future to a cooling trend regardless of what man does or does not do. In fact, there are MANY periods in this planet's history that temperatures were much warmer than it is today and all of them have occurred prior to industrialization and/or urbanization. We do not need to go back to dinosaur times to find that. Based on glaciation extents, the temperature for AD1000~1400 was about 5~8 degrees (F) warmer than present day. About 1400~1800 the world rapidly cooled to about 1 degrees cooler than present day. There had also been a short period of cooling between 1940 and 1977 where global temperatures dropped overall despite rather brisk postwar industrialization and androgenic (human caused) CO2 emissions increase. This is also rather convenient for the Global Warming purveyors because one can often say "oh, Al Gore was growing up, winters were colder and summers were milder". Thats true! But thats not how it was during the great depression or when the Wright brothers flew, it was how it was in the 40s through the 70s. In fact, if you wind the clock back to the baby boom days, there were activists and tabloids prophetising the coming of the next "Ice Age"!

If we look at CO2 itself. There had been times when CO2 levels are 5 to 10 times current levels due to volcanic activities and other causes (eg. the Cretaceous) where the temperature is warmer than it is currently. There have also been periods where CO2 levels are higher, but temperature are cooler -- this is possible because the overwhelming majority of the green house effect is due to water vapor (50~70%) not CO2. Besides, androgenic CO2 is a small fraction of total CO2 production.

What I am trying to say is that the argument that we are in a period of ABNORMAL WARMING -- or that Androgenic CO2 production has anything tangible to do with it -- is at best an unproven theory or an article of faith. At worst, it is a convenient act of fraud and false propaganda used by environmental activists to advance their other causes. These causes range from genuine environmental concerns, to a desire to punish the affluent industrialized world and thereby aid the socialistic goals of material equalization, to the need to find big corporate scape goats for the plights of their favorite animals, to a desire for self atonement for the conveniences of modern life, to simply misconceptions about the problems of our times, to who knows what else.

(2) RWD and CO2 production.

The reason GM gave for suspending RWD expansion is that they do not know how to make RWD vehicles 30% more fuel efficient by 2017.

Firstly, let's make it clear that turning the rear wheels as opposed to the front wheels are not any more or less efficient. However, turning the rear wheels via a drive shaft and a differential axle from a front mounted engine incurs roughly a 5% additional drive train loss compared to a front-engined, FWD vehicle. The typical drive train loss of a FF (front-engine, front drive) vehicle is about 8~10%. The typical drive train loss for a FR (Front-engine, Rear-drive) vehicle is about 12~15%. Full-time AWD is typically 18~20%.

Secondly, the additional RWD drive train components -- namely the drive shaft, separate differential axle -- and the structural differences between a FWD and a RWD vehicle adds about 150 lbs to the weight of a vehicle in the 3000 lbs class.

Thats about it really for economy differences between a FF and an FR car -- 150 lbs more weight and wasting 5% of the horsepower and torque produced to additional mechanical losses. How much is that? Very roughly, its about 1 mpg in a 30 mpg car or about 3%. It sure doesn't help in getting to the 30% fuel economy improvement goals, but it is at best 1/10th of the problem.

So GM's problem really isn't RWD, but the big, powerful "muscle cars" that are supposed to receive RWD platforms. Drop these and you also lose much of the potential candidates for the Zeta and Sigma platforms. But IHMO, all of it is moot. They are not going to get to a 30% CAFE improvement regardless of whether they build RWD Impalas or FWD Impalas. The biggest determining factor of fuel economy is not engine size, power or drive train layout. The biggest determining factor is weight! A 3200 lbs Corvette is about 80% as efficient as a 3200 lbs Honda Accord V6 when driven at a similar speed or acceleration profile despite having twice the engine size and 160 more horsepower. So unless they decide to start making Carbon Fiber monocoques for family sedans or start transitioning wholesale to radical hybrids they are not going to get to the 30% target. So perhaps they have halted RWD to made a sudden and radical decision to put every ounce of their R&D dollars into plug in Hybrids or gasoline electric hybrids and radical chassis lightening?

If they are going hybrid, I suggest that they drop the piston engine altogether and start pioneering the use of recuperated gas turbines along with electric motor propulsions. If they do that then we may yet get RWD cars because the entire paradigm for car design will have changed. The gas turbine will only need to make about 1/4 the cars electric motor's maximum horsepower. The battery will provide the juice for 5 to 40 miles of driving on its own. A 50hp turbine for a 200hp car will fit in the glove box or occupy the space of a muffler. The permanent magnet electric motor(s) will go where the rear differential will go. The battery can be put in the central tunnel. In essence there will be nothing under the hood and no need for a big engine compartment in the front. there will also be no need for drive shafts, differentials or transmissions. If this is the future, then it is way beyond the RWD/FWD argument!

Edited April 16, 2007 by dwightlooi

[Intrepidation]

Dodge handled the RWD VS gas consumption issue well I thin...presenting...

I love how they throw the middle finger at liberal weenies and tree huggers.

[mustang84]

Excellent post, dwightlooi...I couldn't agree with you more!

[RichW5]

Excellent post Dwight.

My only question would be ....... gas turbine size (fit in a glove box?) and the cost of producing the turbines. I would probably go AWD and have electric motors for both the front and rear wheels.

Otherwise it sounds intelligent and the right thing to do. That's why it'll never happen.

[Oracle of Delphi]

Interesting post, I enjoyed reading it.

[Carguy]

Thanks Dwightlooi that was GREAT!!----The TRUTH is a BEAUTIFUL THING!!

[dwightlooi]

Excellent post Dwight.

My only question would be ....... gas turbine size (fit in a glove box?) and the cost of producing the turbines. I would probably go AWD and have electric motors for both the front and rear wheels.

Otherwise it sounds intelligent and the right thing to do. That's why it'll never happen.

The gas turbine is a much less complex animal than a piston engine. There are no valves, no timing chains, no crankshaft, no connecting rods, no pistons, no springs, no water pumps, no ignition coils, no spark plugs, no throttle bodies, no balance shafts, none of that. What you have is a housing in which one or two concentrically rotating parts turn -- depending on whether you have a one or two shaft design. Really, it is very much like a turbocharger with a combustor between the compressor output and the turbine inlet. A typical turbocharger is the size of a stack of CDs. A gas turbine that size is good for about 20~30 hp. So a good question is how much does a really advanced turbocharger cost to manufacture? Of course, some advancements will be needed to made to reach 35% thermal efficiency. But your typical gasoline engine is about 25~28% efficient so even that is competitive because of the size and weight reductions.

Let's do some real world examples...

This is a 60,000 lbs thrust General Electric CF6 turbofan engine. They make a marine gas turbine out of its core (without the big fat fan and roughly the diameter of the tail cone) called the LM2500. You'll find it in the majority of US warships and even some cruise ships (Celebrity's Infinity class comes to mind). This gas turbine currently makes 40,000 hp. Of course we do not need 40,000 hp in our cars.

This is a J402 mini turbojet engine. You'll find it in the Harpoon missile. It has been around for 30 years. It makes about 660 lbs of thrust using one shafts and with one turbine stage. The low pressure compressor is axial, whereas the high pressure one is centrifugal. If you use it to drive a generator, that is about 440hp worth of horsepower. This engine is 13" wide at its fattest point so that kind of gives you an idea how small it is. We also do not need 440hp for a series hybrid's generator drive... 40hp would have be enough to support a 160hp motor by charging a battery capable of handling the motor's current draw. Remember, how often do you use 100% of the horsepower in your car even when you are driving aggressively? I mean what percentage of the time do you spend at 6000 rpm with the pedal to the floor? Less than 10% of the time I hope! Probably less than 1% in normal driving. The turbine always runs at full capacity or not at all.

This is a single shaft, recuperated microturbine. A recuperated turbine passes the compressed air output from the compressor through a heat exchanger fed with the exhaust flow to capture most of the heat from the exhaust. This increases efficiency significantly and reduces exhaust temperatures. A 40~60hp unit is probably the size of a waste paper basket with the core itself the size of a stack of CDs. No radiator or coolant loop is needed to support it. You need to bolt a generator/starter to it to get electricity out of it and to spin it up to working speeds, but the same applies to a piston engine.

BTW, this is an off-the-shelf FB1-4001 permament magnet motor rated for 100hp @ 144 volts. It is 9.1" in diameter and 15.6" long. You can buy one for ~$900. I am sure it won't cost $900 for GM to get one.

This is an FB1-4001 which an Aussie dude installed in his small pickup truck.

Edited April 16, 2007 by dwightlooi

[Sixty8panther]

I do not have the time and energy to invest in this thread, but you all know where I stand.

f@#k Global Warming. Give us RWD now!

[dwightlooi]

I do not have the time and energy to invest in this thread, but you all know where I stand.

f@#k Global Warming. Give us RWD now!

I sympathize with your passion... but you may want to tone down the language a little bit... it may get you into trouble with the mods.

[the_yellow_dart]

I'm glad I live in Ontario.

We're not going to flood for a loooong time.

Have fun living in Massachusetts though.

[SuperSport623]

hell i live on long island... so i think if those ice caps start melting, im screwed... but hell, im on the highest point on the island, so if i may quote sixty8;

f@#k Global Warming. Give us RWD now!

[Dragon]

I'm glad I live in Ontario.

We're not going to flood for a loooong time.

Have fun living in Massachusetts though.

we're right on the water, if water levels rise, we're the first to get hit

[FAPTurbo]

I was reading the Global Warming projections, and my country will come out pretty awesome.

We'll be getting an increased growing season, longer summers, milder winters, an increase in crop selection, etc.

However there is one big downside for us Canadians... we'll be getting Ticks.

And who says you cannot make an efficient RWD machine? BMW is pretty damn efficient.

[loki]

there was a projected map on google maps / earth if the sea levels rose maybe 5, 10, 15, 20 feet i think

[aaaantoine]

My solution to environmentalism is to ban dihydrogen monoxide.

The sooner we get rid of that mess, the better off we'll all be.

[Intrepidation]

I may have missed this in the posts dwightlooi, but if the the turbine pushes air out the back for propulsion how would it go in reverse? Or is it able to turn a drive shaft as opposed to just using thrust for power?

Great posts by the way, they are very interesting to read!

[dwightlooi]

I may have missed this in the posts dwightlooi, but if the the turbine pushes air out the back for propulsion how would it go in reverse? Or is it able to turn a drive shaft as opposed to just using thrust for power?

Great posts by the way, they are very interesting to read!

The gas turbine generator does not rely on thrust at all. Basically the turbine is used to mechanically turn a generator the car is moved solely by electric motor(s). The gas turbine recharges the battery as you drive so it never runs out of juice.

This can be done in two ways... the first is the so called direct drive coupling. Basically, the compressor, turbine and generator's input shaft is the same. In 2-shaft designs it is usually the low pressure spool that is connected to the generator. The large 57,600 hp LM6000 gas turbine generators used in marine applications for instance is a direct drive setup. Most gas turbines however rely on a power turbine. That is the gas turbine produces thrust which is used to spin a power turbine. Either a generator or direct mechanical drive is connected to the power turbine. This arrangement is more complex and in most ways no more efficient. However, it has the advantage that drive line shocks are isolated from the high speed turbine core itself. Hence most applications that drives wheels, propellers, tracks or whatever else directly with a gas turbine uses a power turbine. The AGT1500 and LV100 gas turbines used in the M1 Abrams tank uses a power turbine.

In our hypothetical 40~60hp mini gas turbine generator for a plug in hybrid, the direct drive arrangement will be preferrable for three reasons. (1) It is more compact, lighter and just as efficient. (2) Since the turbine only turns the generator there won't be any shock loads that it needs to be isolated from. (3) Because the generator is also easily a motor, the direct drive setup eliminates the need for a separate starter motor to spin up the turbine to ignition speeds.

This is the M1A1's AGT1500 gas turbine engine. In this application the AGT1500 puts 1500hp onto the power turbine (left hand side shaft in picture) which is connected to the tank's transmission.

[gm4life]

Dodge handled the RWD VS gas consumption issue well I thin...presenting...

I love how they throw the middle finger at liberal weenies and tree huggers.

I like what Dodge did too. f@#k 'em let Kerry hump hybrids, also let Gore do the same. I don't know why Bush is bothering he will get no credit either way. I agree about the liberal weenies and tree huggers. My sons christian religon teacher is so proud of his 2002 Prius he just got from his friends. That f@#k-head. Pardon my French.

RWD IS COMING. AND f@#k EVERYONE WHO WANTS OTHERWISE.

The only midsize-large FWD cars products they need are the following, Saab 9-3/9-5, Buick LaX/Lucerne, Cadillac DTS, Chevrolet Malibu, Pontiac G6 and Saturn Aura.

Edited April 17, 2007 by gm4life

[Sixty8panther]

Sorry about the foul language.... of the thousands of strong opinions I hold

the topic of RWD is THE biggest one, followed by the lack of manual trans.

in today's cars & the pathetic absence of pillarless hardtops in today's cars.

That's it right there... if I had three wishes from a Genie:

1. 75% RWD (only V8 & I6 powered) cars in GM's lineup.

2. Every car except for full size Buicks & Caddys AVAILABLE with manual trans.

3. At least ONE four door hardtop (SIXTEEN) & at least four 2-door hardtops.

[knightfan26917]

of the thousands of strong opinions I hold the topic of RWD is THE biggest one

Just about right there with ya .

Heh ... sure wish I could've purchased a Dodge Charger...........

*sighs*

Cort:33swm."Mr Monte Carlo.Mr Road Trip".pig valve.pacemaker

PICS:lego.HO.model.MCinfo.RT.CHD = http://www.chevyasylum.com/cort

my radio show:CD SHOWCASE.7:30p central.Friday/April 20 = www.wrmn1410.com

[Intrepidation]

Just about right there with ya .

Heh ... sure wish I could've purchased a Dodge Charger...........

*sighs*

Cort:33swm."Mr Monte Carlo.Mr Road Trip".pig valve.pacemaker

PICS:lego.HO.model.MCinfo.RT.CHD = http://www.chevyasylum.com/cort

my radio show:CD SHOWCASE.7:30p central.Friday/April 20 = www.wrmn1410.com

Why can't you?

[Sixty8panther]

For me the biggest reason is $$$.

That's the way of the world. Otherwise my rainy day daily driver

would be a 1959 Invicta flattop & my daily driver for sunny days would

be a 1931 Cadillac Dual Cowl Phaeton ohv V16. Then my weekend car

would be a Duesenberg SJ roadster with a rumble seat.

[Drew Dowdell]

For me the biggest reason is $$$.

That's the way of the world. Otherwise my rainy day daily driver

would be a 1959 Invicta flattop & my daily driver for sunny days would

be a 1931 Cadillac Dual Cowl Phaeton ohv V16. Then my weekend car

would be a Duesenberg SJ roadster with a rumble seat.

No they wouldn't because Marcia would kill you after the second one.

[A Horse With No Name]

....gotta say it...it's a car worth dieing for.

Chris

[knightfan26917]

For me the biggest reason is $$$.

*chuckles*

Sixty8 answered for me the question you asked me Dodgefan .

'Tis true ... not enough money. When I was looking a few months ago, I started adding up payments for the loan, payments for insurance (_almost_ double for that one car than I'm currently paying for all 5 MCs during the summer months), etc. ... and I quickly began to realize I just couldn't justify the added, big expense, especially when you add medical bills into the mix.

*sighs*

If only I were rich and didn't have to work............

Cort:33swm."Mr Monte Carlo.Mr Road Trip".pig valve.pacemaker

PICS:lego.HO.model.MCinfo.RT.CHD = http://www.chevyasylum.com/cort

my radio show:CD SHOWCASE.7:30p central.Friday/April 20 = www.wrmn1410.com

[RichW5]

Back in the stone age, I had a chance to talk to one of the "Owners" of a Chrysler turbine car and ride in the car. It was great! However, the program was cancelled and the cars recalled by Chrysler. Here's the details of the Chrysler experiments:

http://www.allpar.com/mopar/turbine.html

It seems that engine noise and exhaust temperature, along with poor mileage and the government, killed the experiment. It'd be interesting to know if todays technology and/or the switch to electric motors ( with a smaller turbine used for electrical generation) could resolve those problems.

Thanks again Dwight. This thread pulled me away from the drudgery of doing income taxes for the family and "honey do" projects for the wife. It's a break I really needed. Next year I'll let them do their taxes on their own.

[dwightlooi]

Back in the stone age, I had a chance to talk to one of the "Owners" of a Chrysler turbine car and ride in the car. It was great! However, the program was cancelled and the cars recalled by Chrysler. Here's the details of the Chrysler experiments:

http://www.allpar.com/mopar/turbine.html

It seems that engine noise and exhaust temperature, along with poor mileage and the government, killed the experiment. It'd be interesting to know if todays technology and/or the switch to electric motors ( with a smaller turbine used for electrical generation) could resolve those problems.

Thanks again Dwight. This thread pulled me away from the drudgery of doing income taxes for the family and "honey do" projects for the wife. It's a break I really needed. Next year I'll let them do their taxes on their own.

Hey, at least you got until April 17 this year... TWO FULL DAYS later than usual to cough up your tax return.

The main problems with the gas turbine as an automobile engine are as follows:-

(1) The gas turbine is extremely laggy. That is you can floor the throttle now and it may take the turbine 5 seconds to reach full power. Think turbo lag, but 100 times worse. However, this is completely irrelevant in when you use the turbine solely as a electric generator since it is completely isolated from the task of putting torque to the tires. The electric motor will respond immediately using juice from the battery, hence there is zero lag.

(2) The gas turbine has a very narrow efficiency band. That is something designed to operate optimally at say 100,000 rpms may not run at all under 30,000 rpm. Hence, idle efficiency is always horrible. And, the turbine isn't all that efficient across most of its operable range either. Unlike a piston engine where the compression ratio is (barring partial filling due to flow restrictions at very high rpms) more or less constant and driven up the piston displacement and chamber volume, the gas turbine's compression ratio is a function of its rotating speed. Imagine an engine whose compression ratio is 2:1 at 2000 rpm bu 12:1 at 6000 rpm and you get a rough idea of the issue. This is why gas turbines are very efficient in power stations for making electricity where they stay more or less at a constant speed, but not that efficient as an engine driving a vehicle where it has to idle and go up and down in the rev range. Again, this is irrelevant if the way you operate the turbine is to run it at its optimal speed or shut it down completely.

(3) The exhaust temperature can be very high if the turbine is not recuperated (that is the exhaust heat is not transferred to the compressed air coming out of the compressor). With recuperation it is not much if at all higher than a piston engine's exhaust. Recuperation also makes the turbine 4~8% more efficient than it otherwise will be by capturing otherwise wasted heat energy in the exhaust and transferring it to the intake charge after it has been compressed but before it reaches the combustor.The other alternative to recuperation is combined cycle operation. Here the exhaust heat is not passed on to the compressed intake air, but is used to boil water in a heat exchanger. The steam produced is used to drive a separate steam turbine. The combined efficiency of both turbines can exceed 50% (~15% better), beating out even the best piston diesels. This is popular with power stations and has been used in cruise ships. But it may be more complex and bulky than is feasible for a car especially when the goal is to make the turbine generator so compact that it practically disappears from the engine bay.

Edited April 18, 2007 by dwightlooi