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Hi Folks,

About me: bookworm, minimalist, believe less in material than metaphysical.

About my car: Honda City EXI IDSI 2004. bought used @ 43k km. only major change is new tyres - michelin energy xm 1, pumped up to 50 PSI. the car was bought when it became impossible to accommodate safely wifey and two kids on a scooter. (oh, not because of wifey, but the kids keep growing and that's not bad)

Big mistake: heard about the new fad - hypermiling on CNN eco solutions (forum covered there was cleanmpg.com, by wayne gerdes) and fell in love with that concept called hypermiling (Mistake because it has wormed into my brain, and doesn't let go) my last tank was 18 kmpl.

Way ahead: want to creep up to 800 km/tank ( 23 kmpl / 55 mpg) in 2009 and maintain that level

Problem: Achieving this goal requires constant feedback about driving actions and their effect on milage. Not possible without something like scangauge-II

Query: is scangauge-II available in india? any reliable vendor?

But even more serious query: Is my honda city 2004 exi really compatible with OBD-2 protocol and hence compatible with scangauge?

otherwise it will be big money thrown away. i don't like myself, and I won't be able to reconcile with wifey who will throw me out of house, which will not be good in this season in Delhi :eek:

So please help me out.. I admit I am a milage junkie, but it is not really bad thing in these days. you HAVE to agree :)

Cheers, and Happy new year to all BHPians,
- Hummingbird

50psi in a road tyre?:Shockked:

Hypermiling is all very good, but this kind of tyre abuse is asking for trouble.
Loss of braking efficiency, risk of blow out, uneven wear, is it really worth it? just to increase the mileage by a few kilometers?
May I ask what the mileage when driven normally with normal tyre pressures?

Enough lecturing,:D
Welcome to team bhp!

Hi,

51 PSI is the max pressure listed on the sidewalls of the tyres, and there is a safety factor of at least 1.5 to 2 for them to be unsafe (they would not blow at less than 100 psi for sure) Hypermilers routinely set it to 5-10 PSI above sidewall max, but I am conservative - I stick to sidewall max.

What I have observed is handling, responsiveness braking has remarkably improved and wear reduced a lot.

braking performance would be an issue in non-radial cross-ply tyres, but I can show you my tyres do not bulge on the center line or anything.

Higher tyre pressure is one thing that is contributing greatly to my milage achievement (if I can call it so).

Any word on the OBD2 compatibility of honda city exi 2004 / scangauge availability?

Cheers,
Hummingbird

HB - Welcome to the forum! And I know some people are quite fond of Hypermiling but inflating a standard 175/65 R14 to 50 psi is asking for trouble. you're breaching the limits of inflation of the tyre by maintaining such a high pressure. Any incident (long distance drive) or high road/ambient tempratures etc. etc. can easily result in a situation which can cause tyre failure.

If I were you (in the interest of safety of you & your family) I would reduce the pressure by at least 10 psi. There are other & safer ways of increasing the car's FE & I would suggest you do some research on the forum regarding them.

P.S. Yes, your NHC is compatible with OBD II & you can use a compatible scan gauge to check it's parameters.

Hi iraghava,

Thanks for the confirmation about NHC OBD-II compatibility!
Where is the connector located?
Also where should I look for buying a scan gauge in India, preferably Delhi/NCR?

Also I will search for the safety aspects of inflating tyres to max sidewall. Is there already a thread that you can point to?

Thanks for the info in advance,

Regards,
HB

For starters, the contact patch that a tyre makes with the road is reduced.
You might have noticed a harsh ride.

Braking will be affected (increased braking distance and skidding due to reduced grip), which won't be very pleasant if you need to stop suddenly.

A smaller contact patch will also mean the tyre's going to aquaplane (float) over a wet road surface, reducing grip. Handling will be good on a dry uniformly surfaced road but bad, gravel and wet roads will be scary to drive on.

The manufacturer's recommended pressure is an optimized value providing a balance of sorts between handling, fuel economy and ride comfort. Try and stick to that. Inflating a tyre to it's maximum value just puts higher stress on the sidewalls.
Eg., if you bump a curb (footpath) while parking, the tyre might not flex and cracks might develop, which will weaken the sidewalls and chances of a blowout are higher, if you're doing high speeds on a highway on a hot day.


Not entirely related but here's something I experienced last year -> My M-I-L's car had a worn rear tire, due to under-inflation. The sidewall was worn to the extent that the inner structure was visible. I tried inflating this tire to 32psi (the recommended pressure. 44psi, I think, was the max). The tire exploded (BOOM), when the pressure reached 23psi. Imagine this happening when you're doing 120km/h on the highway. :)

Hi aah78,

Sorry, I did not mean to whip up a storm on this matter here in my very first posts. The reference to 50 PSI was there to say that it was almost the only change in addition to some neutral coasting that took me from 13-15 kmpl to 18. But a healthy discourse is a good thing for these fora, and such a discourse should be nurtured, rather than brow-beaten or suppressed. As a moderator, I hope you will agree.

I myself was a non-believer in hyperinflation, till I researched and came across excellent threads like these below, that led me to change my views. However, the topic IS debatable, and there are people on both sides of the arguments.

Hyperinflating tires - Page 7 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
http://www.officer.com/web/online/Editorial-and-Features/Driving-Under-Pressure/19$27281

What interests me at this point though, is the location of OBD-II connector on my new Honda city 2004 Exi, and a local (Delhi/NCR) vendor who can sell me a ScanGauge-II.

Any clues on these two points anyone?

Regards,
HB

Hi & Welcome to the forum hummingbird. Please go through the announcements section before you start posting

You are right. The word 'healthy' is the key here. :)

Welcome to TBHP. Me too a hypermiler here. I have my tires at 38psi and been hypermiling for about one year now. Constantly getting a mileage of 17 kmpl for my Santro in city driving. Verna also used to give me about 15 kmpl in city. My techniques include coasting in neutral to stop, using gas pedal in the most optimum manner so that there is minimal use of other pedals, windows rolled up etc.

Welcome to the forum, HB.

Since the tyre gurus have already touched on the overinflation part, I am skirting that. Have some related queries though :

1) You mention getting 18kmpl with hypermiling. What was your car's FE in similar conditions, pre-hypermiling ?

2) What are your driving conditions like ? I mean daily average running, type of road/traffic, a/c usage, speeds you drive at etc. Just trying to get an idea of what kind of FE this 18kmpl is - especially because your profile says location as Noida, which I assume is good highway-ish roads (might be wrong).

Not a bad thing at all. Infact many of us here are obsessive about mileage, even if we dont hypermile. And having a FE car is a good thing in any times, not just these days of high fuel prices.

Hi Folks! Thanks for the welcome!!

SupremeBaleno:
I was 13-15 kmpl depending on my luck before hypermiling.
average running just ~ 20 km/weekday, ~75-100 km/d on weekends. I took the entire December to exhaust my tank that took 18 kmpl. The downside for FE was small distances between stops and small overall stretches.

Road/traffic - Yeah ppl have already guessed it - Greater Noida is dreamland for vehicles - very good roads, less traffic. Lucky me :D
speeds : I am ever a good friend of the engine - I lothe going beyond 2500 on the RPM and 70 on the speedo.

I employ all the techniques being used by appuchan - they are the basics of hypermiling of course!

Yeah, when you drill down, you may feel this 18 I got is no big deal. But please don't water down my sense of achievement. PLEEESE!

Anybody please tell me who in Delhi/NCR can sell me a scangauge please!

BTW did anybody read through those links? Any comments?

Cheers,
- HB

@HB- I hope I didnt give you the idea that I was trying to browbeat you, definitely not my intention!
Just that 50Psi whether it is sidewall max or not, is substantially higher than the manufacturer recommended number. The rubber will be stressed more than it would be at stock inflation pressure, also, tyres heat up further as they are used, leading to a further rise in pressure- more stress.

I did read the links in that forum- no one there was able to prove or disprove that overinflating is dangerous, atleast , not in that particular page.

Another doubt- coasting in neutral consumes more fuel than idling the engine and moving the car while still in gear right?

I dont have the patience to be a hypermiler, but some of those tricks I do use. Its easier for me because I drive a 4 cylinder turbodiesel-dont have to try very hard to get good FE.

Hey Ripper,

Looks like TBHP is fun! I didn't say you were overbearing. (or anyone else for that matter :D ) But the flames with the 50 PSI figures were something unexpected for me.

From what my elders (in hypermiling) have told me, it is the constant flexing from under inflation that is the bane of tyre life that is what causes heat-up of tyres, not overinflation. Uneven tread wear was a problem in the days of cross-ply tyres, radials hold up their shape quite well at sidewall max. And anyways, who hypermiler worth his fuel would drive at insane speeds of 120 kmph and worry about hydroplaning, braking distances, skidding etc etc? I toot around at granny speeds of 35-50 kmph. Having got rid of all junk in the boot including spare tyre, my acceleration and braking has improved tremendously and the vehicle feels so much powerful and fun to use.

What is on the positive side of overinflation is one big hypermiling advantage - the rolling resistance reduces dramatically on inflating to sidewall max. The car rolls smooth, braking performance improves, and all good things start happening. Only one has to have faith. I have believed, and reaped benefits. I now spread the good word. Amen! :)

I do coast in neutral, but with engine off (so all that coasting is totally free) Many, who are too lazy to shut off engines do coast in neutral with engine ON, and it consumes some fuel (scangauge would tell me how much exactly). Most modern engines shut off all fuel supply to engine when coasting in gear with foot off the gas pedal, but there is the engine slowing down the vehicle by loading it (pistons, flywheel and entire engine acting as damper). Overall, it is better to coast in neutral than in gear - kmpl-wise.

You are one lucky guy to have picked up the correct vehicle milage-wise. On the bargain these beasts are also good at raw HP power, as I have heard. So as they say in hindi - sone-pe-suhaga !

Great to be coasting smoothly in TBHP,

cheers:
HB

Someone I know has bought one last year. Will find the seller's details & let you know.

What your elders might not have told you (by any chance are they mostly from Europe/US etc?) is that there are two unique conditions on our roads that most people abroad cannot warn you about. They are:

1. Hitting a pothole at speed. Under normal inflation pressure, the tyre has enough leeway to squeeze & absorb part of the impact & avoid a tyre failure as they are normally inflated between 28-33psi with an upper limit of 51 psi. But in your case, the tyre under cold pressures is already on the limit of tolerance so any reasonably strong impact will mean instant sidewall failure. And you don't even carry a spare with you any more so the problem could be doubled apart from the obvious risk of you losing control of the vehicle & crashing it.

A lot of users have already had cases of sidewall failure while travelling at decent speeds just by having their tyres hit pot holes/stones lying on the road. And do remember, outside Greater Noida, road conditions are much worse.

2. Unlike most European countries & a lot of areas in the US we have a good 6 months or more of quite high ambient temperatures. What happens in this case is the road surface absorbs the heat & becomes quite hot so as a result any sustained amount of travel on such road conditions automatically heats up the tyres substantially & increases the air pressure inside the tyre (gas expands when heated & all that) which means that an extended journey on a hot highway could result in a failed tyre even without hitting anything.

One important fact you're ignoring is that in modern cars when the engine is off, there is no assistance to the brakes & steering. So if you're coasting with the engine off, in a panic stop most probably your car will not stop within it's normal distance & you won't be able to steer the car away from the obstacle either.

And AFAIK no engine stops complete fuel supply to the engine under coasting conditions (Possible exception being Hybrids & cars equipped with stop & go systems). Doing so would result in the engine sputtering due to lack of fuel (below a certain rpm based on the gear etc.) to complete the combustion cycle & coming to a halt.

One pays for higher milage through higher awareness... I know and avoid all potholes on my daily 20 km routine. There are ZERO potholes on the expressway between G Noida and Delhi. And you know my speeds...:)

Of course, I avoid climate specific mods like radiator grill block (to raise engine temp for efficiency boost, radiator fan delete and potentially dangerous ones like alternator belt off (could starve my batt of charge and make me a sitting duck on the highway)

about the ECU behavior, I can recall the discussion was about even non-hybrids cutting off all fuel supply while coasting in gear at good speeds (> 55 kmph / 35mph). At lower speeds injectors may continue firing for maintaining idling speeds.

I am aware of steering and brake assist loss... It is assist loss, not ability loss... I just remrmber I drive two vehicles in one - a feather touch car when engine ON, and a TATA truck ( that's how it feels and handles) while engine OFF. Any ways, while coasting speeds are low, so the truck is NOT a problem.

Eagerly waiting for those Delhi scangauge vendor details.