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Tata Motors Signs Agreement with MDI for Compressed Air Engine

The 4-cylinder compressed air engine. Click to enlarge.

Tata Motors, India’s largest automobile company, has signed an agreement with MDI (Moteur Developpment International) of France for the application in India of MDI’s compressed air engines. MDI has already applied its CAT (Compressed Air Technology) engine in a prototype city car, the MiniCAT.

The agreement between Tata Motors and MDI envisages Tata’s supporting further development and refinement of the technology, and its application and licensing for India.

MDI has for many years been engaged in developing environment-friendly engines. MDI is happy to conclude this agreement with Tata Motors and work together with this important and experienced industrial group to develop a new and cost-saving technology for various applications for the Indian market that meets with severe regulations for environmental protection. We are continuing the development with our own business concept of licensing car manufacturers in other parts of the world where the production is located close to the markets. We have also developed this new technology for other applications where cost competitiveness combined with respect for environmental questions has our priority.

—Guy Negre, founder MDI

The core of MDI’s work is a piston engine powered by the expansion of compressed air. MDI has developed two versions: a single fuel engine that relies solely upon compressed air, and a dual-fuel version that uses compressed air and a combustible fuel. When running under 50 kph (31 mph) in urban areas, the engine runs on air. At speeds greater than 50 kph, the engine switches to fuel mode. In this mode, the on-board compressor also refills the compressed air tanks.

The current production version of the compressed air engine applied in the MiniCat is a four-cylinder, 800cc unit that uses a boxer design. A proprietary connection rod allows the retention of the piston at top dead center during 70° of crankshaft rotation—providing enough time to establish the required pressure in the cylinder.

Tata Motors has more than 4 million Tata vehicles on the road in India, and is the leader in commercial vehicles and the second largest in passenger vehicles. It is also the world’s fifth largest medium and heavy truck manufacturer and the second largest heavy bus manufacturer.



When I told my wife she was quite enthusiastic, and asked if it'll come with attachments for making whipped cream and steamed milk.


my favorite thing about the MDI AirCar, is the claim that it has a negative pollution effect, because the air needs to be filtered to prevent damage to the tank and engine.

If they were used as service/business use vehicles(taxis and smaller) and 2+ car households replaced their short trip car with one of these, think of the reduction in pollution.

and you can compress the gas with wind, solar, and tidal power.

anyone got thoughts on the turbine generator described in "The Millennial Project: Colonizing the Galaxy in Eight Easy Steps"(chapter 1)


wel this is very inspiring technology but according to me it won't be possible to run an engine only on the basis of compressed air, there must be be somewhat content of charge also.

lets see where the technology reaches...!!1 All the best.


Bought 1000 shares at under $18/share of TTM today as Tata Motors stands to benefit from the investment of this technology, or possibly becomes a good acquisition target. Will see where it goes from here. Hoping for a small pop after the June Popular Mechanics article, but moreover holding it a year and watching for an emotional market response. Trying not to hype this stock, but I am somewhat exhuberent about this pseudo-green technology considering I don't like how gas/electric hybrids have been over-hyped in America as a real alternative. I guess baby steps...


I can just imagine where a motor like this can be in other applications especialy where a motor is stationary such as water pumps,and running air conditioners for homes.or even taking the place of a air conditioner . I as a consumer would really appreciate something in this nature. If a car like this would be illegal in the united states.


Sounds like a good solution for India which needs low cost clean vehicles in its highly congested urban settings. Its storage capacity should cover most commutes there. Its ultimate power source could be renewables or atomic or coal plants placed far from the cities which can far more easily handle pollution than ICE vehicles can and at a lot less expence to consumers. Air quality is a huge factor in India and china and such cars and EVs could go a long way in improving their economic and personal physical health. India and china are different markets from our own. They can live with some of the inconveniences these vehicles would provide as they wait for the technology to improve. If the fuel recharge cost and vehicle cost are low they should do well there.


When will these air compressed engines be in production? I understand that there are still some bugs to get rid of but i would also like to play around with it.


Neat idea for the World Can a heater work in one?



The report you cite actually gives the efficiency of a multi-stage air motor as 83%. That's really not bad at all.

For a Battery EV a realistic figure is about 70% for the most advanced equipment available.

The report has the compressor efficiency at 51%. Combined efficiency would then be 43%. That's still very good compared with other alternatives, if the analysis is true.

anoop pb

dear sir
i creat a idia in air engine
my addreses
anoop pb
pp purayil


I have being checking on air engine and looks like a good idea to me. But why do you say the air eingine is not eficient if the measurements have been done and it takes 2.00 USD to travel like 200 km ( Tell me which gasoline vehicle does that??? A 50cc scooter? Maybe. Driving on hydrogen fuel cell car it gives 100km per kg of hydrogen, the hydrogen today costs around 2.00 USD per kg at the factory when produced from natural gas. Should we verify this cost of $1.00 per 100 km of air car is really true? I would not invest on Tata unless I have proved this. People will not buy a different car if they will not obtain personal benefit, and poor indian or chinese worker isn't really worried about air polution, it is the government who have to force use of air cars in that countries.
The MDI engine looks to me very complicated, I would not invest a cent on that company, I would better invest on Engineair, Di Pietro's engine looks more promising.

Steve M

Beg to differ with the naysayers, espciially the calculator named Erick who makes some very large errors in his work coming up with costs of $4,000 for a tank of compressed air. He needs to spend more time researching this on the web. The tank of compressed air would cost $2 worth of electricity. He seems to be an H2 advocate, not sure. H2 is not a solution because getting the H2 requires energy. It's simply a pollution displacer as in, we run our electric cars so we don't pollute in LA, but we get our electricity from coal plants in Wyoming.

Now switching back to the air compressed engine. They've been testing in India, and they plan to roll out cars in India in 2008. There is no logic to Erick's calculations, with all due respect, as to the masses and distances he speaks of. Does he not think that gasoline tanks in internal combustion engine cars is heavy? Actually, gasoline weighs more than compressed air, and ironically, a compressed air tank weighs only as much as the air that's in it. Just because it's compressed does not make it weigh more. Supposedly, the MDI solution can travel 200 Km on one tank of air. That doesn't seem too bad to me. As for the cars needing to be light weight...all cars need to be light weight, but with miniature explosions going on in your engine and super amounts of heat, an all aluminum engine is only possible with a compressed air engine. This is an engineer's dream come true since 90% of the energy produced in the burning of gasoline is used to heat up the engine not to move the car. So, the efficiencies of an air car are multi-pronged.

I understand the disbelief people have in not wanting to realize a way to actually run cars effectively without a reliance on oil, but guess what...this is the future.

Steven L.

Great comments on MDI engine and fuel system. MDI has captured a hurricane in his engine. MDI and Tata Motors
agreement to improve MDI engine and fuel system will be a big plus. We will have to wait on what Tata Motors has planned for the MDI.


Why would a car like this be illegal in the United States?

Robert Bell

We have seen a lot these "signing agreements" for nearly a decade now, but no cars. Videos touted on the internet as being the prototype "ready for production next year" are nearly 10 years old. What is going on?

MDI is financing itself by selling "licenses" all over the world to different buyers for approximately $350,000 USD. This is an unusual way to raise money. The licensee has to agree to a number of payments later on, and MDI says they will build a "turnkey factory" in the licensee's "territory" for about 1 milions dollars US.

In each instance, such as the Mexican and South African signing ceremonies, we are shown the same photos and videos and told the car will be on the market "next year". But next year keeps getting put off. To date, no factories have been built, and no cars have reached the market. The website for the South African company no longer exists down and I can find no trace of the "licensee" on the Internet (she used to work for a mega-car dealer, apparently).

The licensee thing is interesting, as it avoids scrutiny from investment authorities such as the Securities and Exchange Commission here in the USA. There is a group of "investors" in California trying to form a company to buy a "license", but they have not successfully raised the capital yet. There are no licenses sold yet in the USA, but apparently a lot in other countries including an alarming number in Mexico.

To certify a car for use in the USA (other than as an NEV) would require millions and millions of dollars in crash testing and EPA certification. So the idea of becoming the next Preston Tucker for a million dollars does not seem feasible, at least in the USA.

Tata motors appears to be one of the few "real" car companies to sign a license agreement with MDI. Tata, as you may know, is one of the prospective bidders on the Jaguar/Range Rover line and has an established track record in India.

So perhaps Tata sees something in this technology or perhaps they figure for $350,000 they have nothing to lose, or perhaps maybe Indians are not as smart as we thought they were.

They are bidding on Jaguar, after all....

Oddly enough, the Official Tata Motors website makes no mention of the MDI partnership or anything else relating to compressed air vehicles.

The proof is in the pudding. There have been a lot of folks out there claiming to have the next big thing, only to fizzle out. The unusual financing arrangment of MDI does make one scratch their heads. They are selling licenses, for the most part, to unsophisiticated

Time will tell. But thermodynamics and basic physics is stacked against compressed air technology. 4000 psi tanks will take considerable energy to refill, and the range issue makes flooded-cell electric cars look like long-range vehicles.

And if the idea was truly great, there would be legions of copiers already rushing competing vehicles to market. That is the real kicker.

Oh yes, I forgot, the same old saw - the oil companies and GM are "suppressing the technology"

If you believe that, I have a license in a compressed air car to sell you....

Tahir Mukhtar

I think some pepople are being too tough on MDI, and their compressed air engines. I thin thats how the world's soon going to figure out the best in alternative fuels technology, as this is something the world needs in very near future.(or otherwise world will be damaged beyond repair. Algore does give all of us sleepless nights)

Ben Brown

Both the air car and engineair sound like potential technologies that should actually work and be beneficial if the R&D continues. I would guess it needs many more minds than its founders to reach its potential. Though I would prefer to use the engineair motor, if Tata offered the air car in the US I'd seriously consider buying even this 1st generation of air vehicles. More importantly, if there were air car clubs. (like the ev clubs) I'd be there in a minute. I believe that's where the genius of development will start from.

Odilon De Moura

I believe the DMM would be a good choice for the air engine, if used together, my new compressed air generator
Details about how the actual engine will be are not published, on DMM Site.
I will provide details on how the engine should be.

Ian Houston

A Good move by TATA.

There obligation on CO2 Emissions passed onto the Energy Companies.

Everytime the compressed air needs refilled the generators spike the power stations, inturn their emissions go up.

Wonder who will pay for the energy increase!!!!

Smart move for TATA, just a headache for power boys.


For more information on the Air Car, check out or

David Guerin

Good Morning. . . I am so very interested in this new technology of cars, however I'm don't understand why no one is using the energy from the wheels in motion to reproduce the air with on-board compressors or on-board generators. I'd like your feedback on this, as I am very interested in owning a car like this and/or becoming a dealer of this outstanding cars! Keep up the good work.

We have an improved version of several Air Related components such as a more efficient engine, and auxillaries such as auxilliary multifuel on-board hi efficiency engine, for a air/combustion hybrid, and finally more efficient compressors. Sannerprojects, Inc (USA) Works well with geothermal and solar concentrator systems.

Stan Wellaway

I can see the advert..

"Buy our air-powered car - it'll blow you away!"


Geoffrey McClelland

Hello i am wondering if you export the air compressed car? I would like to import them to australia if this is possible could you forward your contact details so i can get intouch with you please? Thank you

Best Regards

Geoffrey McClelland


very wonderfull article very power different article

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