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Old 18th August 2007, 01:32   #31
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Chetan, Agreed with you - my car runs better @ cold too... possibly bcoz it is in open loop till 02 gets heated up as well...
VAG has measuring blocks - one group shows retard for cylinders - none shown.
6-8 degress not % - sorry typo.
Flipsyde, my car drives great otherwise - you should ride in it to feel the mid range.

Thanks,
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Old 20th August 2007, 01:20   #32
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Default Stoichiometric ratios are rarely achieved.

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Originally Posted by v1p3r View Post
On which car, on which fuel, on which planet?
On cars with a piston and cylinder( hence wankels are out since they always tend to run rich).

Running on a mixture of Gasoline, adultration and 5 to 10 % ethanol blend.

On any planet with an atmospheric content similar to ours

When warm 11:1 and when it is hot about 12.5:1. The piston cylinder engines rarely achieve the stoichiometric ratio of 14.7:1.. Thats only a dream/goal to achieve with pollution norms geting stricter.

AutoSpeed - Real World Air/Fuel Ratio Tuning

K&N Air/Fuel Ratio Monitors

Air-fuel ratio - Wikipedia, the free encyclopedia


Air-Fuel Ratio Meter Tuning- Car Craft Magazine

NGK Powerdex AFX Wideband Air-Fuel Ratio Monitor Kit

Last edited by drpullockaran : 20th August 2007 at 01:37.
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Old 20th August 2007, 01:49   #33
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Default With Indian blends the ratio is not what it seems.

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Originally Posted by chetanhanda View Post



This is not the issue , he is reporting perfect lambda readings @ idle ...
Target Air/Fuel Ratio Table

Read the previous URL's I posted inthe preceding post.
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Old 20th August 2007, 02:04   #34
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Originally Posted by drpullockaran View Post
At idle you should have a 11:1 OR 12:1 ratio when the car is warm and if not a ratio of 11:1 is the norm. The other thing you mentioned is that the O2 sensor shows a reading of less than .6 to .7volt and if thats the case you are running rich because I believe that higher the readings more is the oxygen level and leaner the fuel mixture. It could also be that if you have the 4 lead O2 sensor the heater coil of your sensor has gone dead. If the 2 lead version is used in your car then a rich mixture is the resultant and possibly your flame front from the spark plug is being quenched partially resulting in hestitation from revving.

Oxygen Sensor Information


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Factual error noticed and hence correcting. When Oxygen sensor voltage increases above 0.45millivolt then the engine is running rich and when less than 0.45 volt then engine is running lean. Its better to err on the richer side than on the lean side with fuels sold in India and Brazil. 0.6 to 0.7 is what most sensors need to output with our fuels. Lower may be good for CO emmisions but at the expense of NO emissions and longevity of the engine.

Read the first URL to understand about faulty sensor and its diagnosis. The OBD connector isnot the sure fire way to diagnose a faulty sensor.

Last edited by drpullockaran : 20th August 2007 at 02:12.
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Old 20th August 2007, 22:26   #35
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Originally Posted by Octavia2 View Post
Chetan, Agreed with you - my car runs better @ cold too... possibly bcoz it is in open loop till 02 gets heated up as well...
VAG has measuring blocks - one group shows retard for cylinders - none shown.
6-8 degress not % - sorry typo.
Flipsyde, my car drives great otherwise - you should ride in it to feel the mid range.

Thanks,
with that monstrous 2L engine + mods under the hood i have no doubts about the mid range!!!

i've had issues similar to yours on a optra 1.8 upon cold start.... just as soon as the engine reaches normal operating temperatures its as responsive as usual.

@chetanhanda - when your trying to spin your wheels i'm sure you don't let the clutch go at cold start RPM's (1200-1500). what i mean is in a cold engine when you punch the throttle it takes .5 sec before it gives you the revvs unlike a hot engine.

its always been this way for me.

@octy2 - nevertheless i'd like a ride it it sometime.

Last edited by flipsyde : 20th August 2007 at 22:28. Reason: almost missed a chance to ride in a fellow t-bhp members car
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Old 21st August 2007, 21:44   #36
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Quote:
Originally Posted by drpullockaran View Post
Target Air/Fuel Ratio Table

Read the previous URL's I posted inthe preceding post.
dude !! first of all relax !! u are mixing up 2 things we are dscussing his AFR at idle, please read the 1st post.

Quote:
Originally Posted by drpullockaran View Post
At idle you should have a 11:1 OR 12:1 ratio when the car is warm and if not a ratio of 11:1 is the norm.
why would anyone want to idle at <14.7 ?at idle u want min emissions without stalling the engine
It makes sense to have 11 to 13 when u want power or under hard accelaration.

1st of all u should understand that 12:1 or 13:1 etc etc is good for power when the engine is loaded or accelarating. everyone knows that optimal bhp is not @ 14.7:1...
But at idle when the air is being supplied by the secondary IAC/EAC etc u dont need 11/12/13:1 ratio ..u dont need BHP u just need sufficient air to keep the engine alive with minimum emissons..
I hope u are aware of the secondary air control system and Tp sensor at idle ..u get an entrely diff set of readings for AFR and also consider what happens when u have a cold engine and a hot engine..

so 14.7:1 is OK at idle and 11,12,13:1 is great at engine loads under part throttle or WOT condition under load

take a wideband o2 sensor, plug it in if it says ideal or 14.7 let it be... when u are accelarating or simply going wide open then go for <14...

dont point us guys to another set of "basic" Urls on AFR and please no "Wikipedia stuff" .. we have seen enough of these ... and I think you should read your own URLs more carefully before asking people to tune their idle for AFR, also there is a big diff in practically seeing a tuner prepare a drag car and just reading URls...

Last edited by chetanhanda : 21st August 2007 at 21:47.
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Old 21st August 2007, 21:55   #37
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Originally Posted by flipsyde View Post
@chetanhanda - when your trying to spin your wheels i'm sure you don't let the clutch go at cold start RPM's (1200-1500). what i mean is in a cold engine when you punch the throttle it takes .5 sec before it gives you the revvs unlike a hot engine.
its always been this way for me.
I dont do wheelspins at cold start
But even If I did my engine would be more "peppy/responsive" to slight throttle inputs becoz its already running at higher RPM already due to open loop .. even "Octavia2" feels the same on his skoda ..

plz explain how ur engine(when cold) would be less responsive ? in cold engine the engine is already revving higher for a TP reading as compared to when the the engine is hot(or o2 sensor is warm) for the same TP reading ...
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Old 21st August 2007, 21:59   #38
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Originally Posted by Octavia2 View Post
Chetan, Agreed with you - my car runs better @ cold too... possibly bcoz it is in open loop till 02 gets heated up as well...
VAG has measuring blocks - one group shows retard for cylinders - none shown.
6-8 degress not % - sorry typo.
Flipsyde, my car drives great otherwise - you should ride in it to feel the mid range.

Thanks,
dude so u think we can rule out ECU cutting u off under accelaration ?
knock sensor , ignition retard.. nothing cutting u off ?
do you get the same feel when u r in any other gear+with AC+load and try to floor the throttle ?
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Old 24th August 2007, 00:13   #39
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Default We are talking of blended fuels in India with kerosene too.

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Originally Posted by chetanhanda View Post
dude !! first of all relax !! u are mixing up 2 things we are dscussing his AFR at idle, please read the 1st post.


why would anyone want to idle at <14.7 ?at idle u want min emissions without stalling the engine
It makes sense to have 11 to 13 when u want power or under hard accelaration.
I thought it was near impossible to idle without stalling with a mixture set at ideal stoichiometric ratio in engines which are not designed for leanburn. To prevent stalling the ratio of petrol is usually increased at idle and more over we are talking of E10 fuels in India.

Engine Modification

A Literature Review Based Assessment on the Impacts of a 10% and 20% Ethanol Gasoline Fuel Blend on Non-Automotive Engines: 5. Fuel System and Control System Definitions
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Old 24th August 2007, 20:26   #40
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Originally Posted by drpullockaran View Post
I thought it was near impossible to idle without stalling with a mixture set at ideal stoichiometric ratio in engines which are not designed for leanburn. To prevent stalling the ratio of petrol is usually increased at idle and more over we are talking of E10 fuels in India.

Engine Modification

A Literature Review Based Assessment on the Impacts of a 10% and 20% Ethanol Gasoline Fuel Blend on Non-Automotive Engines: 5. Fuel System and Control System Definitions
if the wideband shows green or says its ideal we accept that as perfect ... now if u go and burn the same fuel in a lab under near perfect conditions it may be diff.. but we follow what the wideband says its the benchmark for us.
e.g If I use regular pump gas 97 octane I will look for green zone on my AFR = normal during idle, again if I were to tune with a crazy higher octane race gas I would again look at my AFR and make changes.. to fuelling and timing...i would have diff maps for diff octane
so at a given AFR the race gas is going to give me more power...

BTW the second article is on open loop non automotive systems so I wouln't use that as a reference.
the minute the o2 sensor gets warmed up the car goes into closed loop..

are we on same page.. or r u still saying u should idle at 11:1 as per lab report when ur foot is of the throttle using pump gas?
if u were running a high compression high octane race gas with crazy high lift hi duration cams i would keep my AFR more rich in order to keep it from stalling or run more smoother maybe something like 13.5 etc etc ....
but on a stock car with pump gas I would follow the AFR and say idle according what the AFR says is perfect "14.xyz"
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Old 25th August 2007, 00:37   #41
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Quote:
Originally Posted by chetanhanda View Post
if the wideband shows green or says its ideal we accept that as perfect ... now if u go and burn the same fuel in a lab under near perfect conditions it may be diff.. but we follow what the wideband says its the benchmark for us.
e.g If I use regular pump gas 97 octane I will look for green zone on my AFR = normal during idle, again if I were to tune with a crazy higher octane race gas I would again look at my AFR and make changes.. to fuelling and timing...i would have diff maps for diff octane
so at a given AFR the race gas is going to give me more power...

BTW the second article is on open loop non automotive systems so I wouln't use that as a reference.
the minute the o2 sensor gets warmed up the car goes into closed loop..

are we on same page.. or r u still saying u should idle at 11:1 as per lab report when ur foot is of the throttle using pump gas?
if u were running a high compression high octane race gas with crazy high lift hi duration cams i would keep my AFR more rich in order to keep it from stalling or run more smoother maybe something like 13.5 etc etc ....
but on a stock car with pump gas I would follow the AFR and say idle according what the AFR says is perfect "14.xyz"
I just noticed you are based in Minneapolis and me in Ernakulam, India. Here pump gas is more like 87 Octane rather than 97 Octane that you mentioned.
Please note that our engines in India are fed on a diet of E10petrol mixed with adulterants too and do remember that E10 absorbs moisture from the atmosphere too. I still maintain that at idle the mixture has to be far richer than when coasting along at 1500 to 2000rpm and even then we India can only dream to achieve to run with a smooth engine with ratios leaner than13.5:1. I will try and get further articles before putting up my case any further and that has to be after the Onam festival in Kerala which will be over after the 27th of August. Bye till then.
Bye and wear your seat belts.

Last edited by drpullockaran : 25th August 2007 at 00:39.
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