[ananth_iy]

Friends, while we jump to the conclusion that Coimbatore to Avinashi has to be on NH-47, there is an alternate route off Sathyamangalam Road with a road that leads to Avinashi after Annur. I took that road in May as well to avoid the road work on NH-47 and it was a nice empty road in quite good shape. The photo also seems to have been taken on that road. Now, even on that road, you will get to Avinashi in 40kms or less so I am still not sure where was the other 32 kms driven on. Also, 10-15 kms of the 40 kms is still within the city with moderate traffic.

Tons of holes in the claim is all that I would say.

[Latheesh]

^^
CBE-ANNUR-AVINASHI is a decent 2 lane road with less traffic, just like any other decent 2 lane road. Love to know his driving style!

[Tarun]

I somehow never use to believe these high claimed efficiency figures, however a personal experience changed it.

Me and my friend were driving a 2001 Zen from Noida to Hamirpur ( H.P.). It was in the month of Dec 2009 , the car still in prime condition with engine compression as good as new. Tanked up at the delhi border , with no mindset of attaining any high mileage figures, but just enjoying the ride. Drove @ constant 80km/ hr, windows rolled up, side mirrors folded, blower (circulation), music on and a stop at Karnal for dinner. Refueled at Chandigarh, just before Ropar @ Indian oil pump. The car consumed just a notch above 7 liters and we traveled 225 kms with an incredible ~32km/ ltr mileage. The majority part of drive went by on discussing how is this possible in real situation and may be some Juice is there in claims !

[sam_sant2005]

Originally Posted by Johnny_

I got your point Lucifer, and am aware how engine braking works. It helps one save fuel by letting the car stop by itself due to the friction and rolling resistance instead of applying the brakes. Thanks for restating it in detail. It will enlighten the novices.
And in technical terms, it is described as work being done on the system (i.e. mechanical power is given back to engine) instead of work being done by the system (i.e. mechanical power from engine to the wheels).
This is leveraged in the form of Regenerative Braking in Hybrids. Explained it again as you said you weren't aware of it.

One more point I would like to add wrt engine braking vs normal braking is that while descending down a long hill (say Ooty downhill) if one keeps on using the normal brakes, due to overheating you may loose the brakes temporarily. I have seen this in Fiat 1100, Maruti Esteem and M800. I escaped in such an instance by just a whisker. Don't know if it happens in others. So again it re-emphasizes the need for using engine braking.

Or in simple terms if I can put it - "You should drive down the hill the same way that you drove up (read gears)".

Additionally in some mini vans like Swaraj Mazda I have seen a small button on the floor near the drivers seat which gives another kind of engine braking. Just press on that using the feet and vehicle speed reduces (giving a typical Mazda engine braking sound). That is another kind of engine braking though not to be confused with 'engine braking' we are talking here by putting the vehicle going downhill into a lower gear thereby reducing its speed.

[Johnny_]

Originally Posted by sam_sant2005

One more point I would like to add wrt engine braking vs normal braking is that while descending down a long hill (say Ooty downhill) if one keeps on using the normal brakes, due to overheating you may loose the brakes temporarily. I have seen this in Fiat 1100, Maruti Esteem and M800. I escaped in such an instance by just a whisker. Don't know if it happens in others. So again it re-emphasizes the need for using engine braking.

Or in simple terms if I can put it - "You should drive down the hill the same way that you drove up (read gears)".

Additionally in some mini vans like Swaraj Mazda I have seen a small button on the floor near the drivers seat which gives another kind of engine braking. Just press on that using the feet and vehicle speed reduces (giving a typical Mazda engine braking sound). That is another kind of engine braking though not to be confused with 'engine braking' we are talking here by putting the vehicle going downhill into a lower gear thereby reducing its speed.

Yup Sam agree with you.Coming down in the same gears as the one used for going up. And that temporary loss of braking feel is something that should be kept in mind.

[Klub Class]

Originally Posted by Johnny_

That would have required you to switch off your engine.

Johnny, you got it wrong there.

For the record, the engine was NOT switched off and we're letting the car roll on it's own, mainly in the 2nd & 3rd gears.

Didn't you just miss my last post in this thread, where I had shared additional details? Well. Here is the link to the post : http://www.team-bhp.com/forum/indian...ml#post2382112

Would the power steering function when the engine is switched off? I have seen the hydraulic ones don't function when the engine is switched off.

A small correction : Even when the engine is switched off, you'll be able to steer until the steering gets locked. But, the steering will become very much stiffer and it'll be very hard to steer.

PS: Switching OFF the engine while driving is a strict NO NO!

[typeOnegative]

Originally Posted by lucifer1881

The engine is still running. It does not matter whether it is combustion running it or the drive wheels. As long as the engine runs, the fan belt runs, the alternator runs, the hydraulic system runs, the brake vacuum is maintained, etc.

Hmm that is interesting indeed. Will take your word for it. I am a Mechanical Engineer of 1998 vintage. Technology has moved on ...

[lucifer1881]

Originally Posted by typeOnegative

...Technology has moved on ...

Umm, not really. The internal combustion engine today is not all that different from the one Karl Benz designed. The electronics have just made its management that much easier. Whether you take today's car engines or yesteryears, as long as you have a mechanism to control fuel intake then during engine braking no fuel needs to be supplied to the engine.

I have read accounts of people with carb engines using solenoids (the fuel injectors are solenoid valves, after all) to control fuel intake (especially during engine braking). In fact, engine braking is much easier on the engine too. The reason is that there is no fuel-air mixture exploding. It is the power stroke that places greatest stress on the engine. The intake, compression and exhaust strokes are quite benign in comparison.

[R.D.P.]

Mr Narayanan R Menon mentioned exact conditions in his blog
A Road to Fuel Efficiency

Key thing is to keep rpm somewhere around 1440

He is practical when he suggests that "Fuel, Traffic rules & regulations and road - condition" are important contributors in achieving good fuel economy.
Practicality of keeping rpm around 1440 is different story and its effect of engine life is questionable.

Effectively I think what matters is ability to drive at constant rpm as long as possible to get good fuel efficiency. It is easy to check, switch DIS to inst avg mode in manza and see 25kmpl is getting displayed at speed traffic allows you to drive keeping constant speed . Avoid rash overtakes, and you should get maximum possible fuel efficiency under given traffic condition while doing safe driving. If there are lot many signals/traffic jams obviously, one should be happy with lower fuel efficiency. Its not possible to achieve dramatically high efficiency which one can get on plain road which allows long stretches drive at constant speed/rpm.

But I do not think we should question fuel efficiency claims, these are achieved under certain conditions with careful driving .

[typeOnegative]

Originally Posted by lucifer1881

Umm, not really. The internal combustion engine today is not all that different from the one Karl Benz designed. .... The intake, compression and exhaust strokes are quite benign in comparison.

Was not talking about the four cycles or the legacy of Mssrs Daimler and Benz. It is just the fact that the ECU cuts off fuel supply to the engine totally during engine braking that surprised me. But yeah, what you have highlighted makes sense. Thanks for helping me learn something new.

[Johnny_]

Originally Posted by Klub Class

Johnny, you got it wrong there.

For the record, the engine was NOT switched off and we're letting the car roll on it's own, mainly in the 2nd & 3rd gears.

Didn't you just miss my last post in this thread, where I had shared additional details? Well. Here is the link to the post : http://www.team-bhp.com/forum/indian...ml#post2382112



A small correction : Even when the engine is switched off, you'll be able to steer until the steering gets locked. But, the steering will become very much stiffer and it'll be very hard to steer.

PS: Switching OFF the engine while driving is a strict NO NO!

yup, the correction came later on
And yea that is what I was referring to, the steering becoming very stiffer (even more stiffer than non-PS car).

[raj_srini]

@rdp - I just read Menon's blog. I agree and do not think we can question the integrity of the data point, especially when it has been certified by Limca Book of World Records.
The point being made on constant rpm is something I can relate to as well. My Corsa gives me an average of 11kmpl with A/c if I drive safely vs. 9kmpl if I drive like normal Delhiites.
I'm actively considering purchasing a Manza and this is definitely positive. The potential niggles that I may face is the only cause of concern.

[centaur]

Guys, Mr. Narayanan Menon is active on one another car portal in which he has given a link to his blog and also mentioned how he has achieved this feat. He has also mentioned that this is not the first time he has got such a big figure and the figure of 46.33 became publicly known because that is what his Manza returned when Limca people came in for making this a record. He seems to have achieved 30kmpl from a linea, 45.xx from an indica and 30+kmpl from a honda city (I dont remember the exact figures as I had read it sometime back). He says he has got this by driving his car in the RPM of around 1440 -1500 and claims that at 1440 the car returns best FE. Going too below this range or too much above this range would be detrimental for FE figures. He has also posted many certificates and proofs for his claims because of which saying this is a marketing gimmick is hard to believe. Moreover he seems to have achieved similar figures in other cars as well. Finally it is for us to believe it or not. Between all the info that I have posted here is just a recall of whatever I read there. So dont blame me for anything.

[TURBOSAM]

Note from the Team-BHP Support : Please avoid typing with excessive dots.........like................this. Thanks

hi,
fundamentally, diesel works with excess air coefficient.
petrol(spark ignition) engines are designed to work around 14.7:1 air fuel ratio.
in diesels it can be as rich as 20:1(still lean than the chemically correct ratio )to whooping 120:1 .that too in to stratified charge combustion pattern.
amount of diesel injected determines the power output (in generic terms)
so if the diesel engine is of highly refined design,(giving up to 6 injections each,from 5 holes of each injector per cylinders.,, is small,(mass wise) thoroughly warmed-up including all the coolent and lube oil (lesser thermal losses in heating the components)plus driven just at the rpm where the intake manifold vacuum value is trying to change in to boost value...
topped with tall gear ratio, fitted in a good, lightweight aerodynamically good body shell the vehicle can give really great mileage..
i know many 1.3 75 P.S. palio stile cars which regularly give 28-30 kmpl on long roads like pune to goa via sankeshwar....
linea diesel(1.3 90P.S.) has given 29+kmpl on such roads,
i personally have achieved 31 kmpl in such a vehicle...with 3people on board, partial a/c on ,tinted glasses, v cooled front wind shield ...
diesels can do wonders...
all that matters is light weight ,aerodynamic bodies, tires with low rolling resistances, good under body designs,,, zero down force,and the premium diesel technology can give u astonishingly unbelievable numbers on regular basis.
additionally manzas are @200 kga lighter than lineas powered with the same engines... plus were equiped with taller gear ratios

[prasadnair]

just a marketing gimmick you cant do that in normal daily driving
the trident iceni with a 550 bhp@3800rpm 1288nm@1800rpm 6.6l v8 duramax turbo diesel
can do 28 km/l impressive i think