[Sutripta]

^^^
Where do we stand if we look at each (MPFI, TC, SC) individually and not lumped together?

Regards
Sutripta

[SS-Traveller]

Originally Posted by 1self

Accurate fuel metering is in steady state conditions, not when the turbo is going from almost stand still to full song.

Isn't fuel metering a function governed by the ECM, rather than the rpm of the turbocharger?

And isn't turbo boost pressure also governed by the ECM to an extent?

Also, isn't a turbo always on (i.e. never at standstill while the engine is running), and would it not go to 'full song' in a gradual manner linked to engine rpm building up, rather than when the throttle is floored?

[fighterace]

Hello everyone!

Just bought a set of Denso KP20R-U spark plugs for my car, will get them fitted in a coupe of days. The plugs are made in Japan, while the NGKs are made in India. So hoping for the best.

[fighterace]

Update:

Installed the Densos (K20PR-U). I feel the engine has become smoother, and is pulling better.

[Sankar]

Good choice, i too am using Denso spark plugs (iridium Power) in my car.

[Arch-Angel]

Isn't pre-detonation of the air/fuel mixture more dependent on the temperature of the cylinder itself(since it is sprayed inside through the injectors) rather that being more dependent on the surface temperature of the spark plug?

Also, from what little i can understand, a turbo only introduces more air(compressed,dense) and its spooling up is in correlation to the exhaust gas pressure which is again dependent on the engine rpm which again depends on the throttle position. I don't exactly understand how that would mean that a hotter plug would cause pre-detonation but what is with the correlation of this to a turbo? Has this got something to do with the EGT(i recall that turbo compresses air and is driven by the exhaust gases and exhaust gas is recirculated if the vehicle has an EGR)?

[headers]

Originally Posted by SS-Traveller

Isn't fuel metering a function governed by the ECM, rather than the rpm of the turbocharger?

And isn't turbo boost pressure also governed by the ECM to an extent?

Also, isn't a turbo always on (i.e. never at standstill while the engine is running), and would it not go to 'full song' in a gradual manner linked to engine rpm building up, rather than when the throttle is floored?

1. Fuel metering is governed by the fuel pump which gets its input from the ECM [in mpfi]

2. Turbo boost pressure is related to the a-pedal input indirectly. But most of todays TC diesel cars in india are mild turbos in the interest of the environment [BS4 BS5 etc]. Their placement, plumbing and performance depends on the engine design and TC design which by itself is a HUGE topic.

3. And TC base rpms are around 40000 and on full song around 160000 rpm [again depends on the TC type, model, vehicle engine etc]

Originally Posted by Arch-Angel

Also, from what little i can understand, a turbo only introduces more air(compressed,dense) and its spooling up is in correlation to the exhaust gas pressure which is again dependent on the engine rpm which again depends on the throttle position. I don't exactly understand how that would mean that a hotter plug would cause pre-detonation but what is with the correlation of this to a turbo? Has this got something to do with the EGT(i recall that turbo compresses air and is driven by the exhaust gases and exhaust gas is recirculated if the vehicle has an EGR)?

Sir, EGR can be there even in non TC cars - My X 2002 Indica DLX was a non TC car with EGR

There is no correlation between EGR and TC but please re-read that post as to why a hotter plug COULD cause pre detonation.

[Aroy]

Originally Posted by fighterace

Hello everyone!

This is my first post in this forum, though i have been a regular visitor for a long time. Recently i changed the spark plugs of my Zen MPFI. The Champion plugs were replaced by NGK BKR5E-11 plugs with grooved centre electrodes. The manual recommends NGK BKR6E plugs. The new plugs are hotter (5 instead of 6) and have a larger electrode gap (1.1 mm instead of 0.7-0.8 mm). My mechanic says that the plugs are fine, but wikipedia says that they might cause detonation. Can the experts please comment on this? Can I keep using these plugs or it is advisable to change them? Also, I can't find any vehicles which use this particular plug. Am I being straddled with export reject stuff?

The heat rating of a plug denotes the heat transfer between the electrode tip and the body.

If a colder plug is used, it will cool faster, hence the spark may be weaker, till the engine heats up properly

If a hotter plug is used, it will give better ignition in a cold/warm engine, but once the engine heats up it may not cool enough. In extreme cases it will start glowing, which will result in pre ignition - detonation.

Thus if you are only doing short runs, a hot plug may be more appropriate.

If most of the journeys are longer and at higher speed, a colder plug will be better. If you are in a habit of ripping your engine (running the car at high RPM consistently), then a colder plug is definitely required if pre ignition is to be avoided.

A longer gap in plugs will require a higher voltage from the coils else it will fire later (similar to a retarded engine timing), and shorter gap may fire earlier. This is most apparent where the distributor is mechanical. Electronic ignition timing is controlled more precisely, but the above phenomenon will still hold. Hence you have to reset your engine timings to suit both the plug ratings and your style of driving.

[SS-Traveller]

Originally Posted by Aroy

If a colder plug is used, it will cool faster, hence the spark may be weaker, till the engine heats up properly

If a hotter plug is used, it will give better ignition in a cold/warm engine, but once the engine heats up it may not cool enough. In extreme cases it will start glowing, which will result in pre ignition - detonation.

If the electrode tip dissipates heat more rapidly, why would the spark be weaker? Spark intensity is certainly not dependent on temperature of electrode tips.

[Aroy]

Originally Posted by SS-Traveller

If the electrode tip dissipates heat more rapidly, why would the spark be weaker? Spark intensity is certainly not dependent on temperature of electrode tips.

"Carbon fouling occurs when the spark plug firing end does not reach the self-cleaning temperature of approximately 450°C (842°F). Carbon deposits will begin to burn off from the insulator nose when the self-cleaning temperature is reached. When the heat range is too cold for the engine speed, the firing end temperature will stay below 450°C and carbon deposits will accumulate on the insulator nose. This is called carbon fouling. When enough carbon accumulates, the spark will travel the path of least resistance over the insulator nose to the metal shell instead of jumping across the gap. This usually results in a misfire and further fouling.

If the selected spark plug heat range is too cold, the spark plug may begin to foul when the engine speed is low or when operating in cold conditions with rich air-fuel mixtures. In some cases, the insulator nose can usually be cleaned by operating the engine at higher speeds in order to reach the self-cleaning temperature. If the spark plug has completely fouled, and the engine will not operate correctly, the spark plug may need to be cleaned / replaced and the fouling cause identified. "
Extracted from http://www.ngksparkplugs.com/tech_su...k_plugs/p2.asp

[SS-Traveller]

Originally Posted by Aroy

"Carbon fouling...the spark will travel the path of least resistance over the insulator nose to the metal shell instead of jumping across the gap.

Ajoy-da, I would think spark plug 'shorting' is entirely different from having a 'weaker spark'. In practice the net effect of either on the running characteristics of the engine may be the same, but rectifying either issue would require addressing different parts and components.

[Aroy]

Originally Posted by SS-Traveller

Ajoy-da, I would think spark plug 'shorting' is entirely different from having a 'weaker spark'. In practice the net effect of either on the running characteristics of the engine may be the same, but rectifying either issue would require addressing different parts and components.

The nett effect is a weaker spark

[Sutripta]

Lots of questions about quite a few (diverse) posts in this thread. But lets start with something simple.

Originally Posted by Aroy

The nett effect is a weaker spark

What exactly is the difference between a 'normal', 'weak' and 'strong' sparks? How will we make out/ measure the difference? And what will be the effect on the running of the engine?

Regards
Sutripta

[Aroy]

Originally Posted by Sutripta

Lots of questions about quite a few (diverse) posts in this thread. But lets start with something simple.

What exactly is the difference between a 'normal', 'weak' and 'strong' sparks? How will we make out/ measure the difference? And what will be the effect on the running of the engine?

Regards
Sutripta

A normal spark will spark across the electrodes, with the designed current. This will ensure that the fuel is ignited at the correct time and combustion is complete.

A weak spark will have less current, hence may ignite later resulting in both incomplete combustion as well as a retarded timing - result is less power

A strong spark, as long as it is not premature will not affect combustion.

http://query.nytimes.com/gst/abstrac...D0405B878DF1D3

http://smallengineinformation.com/?page_id=411

http://www.clubcivic.com/board/showthread.php?t=201999

[Sutripta]

^^^
Hi,
Understanding from this and your previous posts, it seems that
a) a 'weaker' spark will result in retarded ignition.
b) the quality of combustion is 'poorer' if started by a 'weak' spark.
Have I understood correctly?

Originally Posted by Aroy

A normal spark will spark across the electrodes, with the designed current. This will ensure that the fuel is ignited at the correct time and combustion is complete.

Could we have some ballpark figures for designed current.

A weak spark will have less current, hence may ignite later resulting in both incomplete combustion as well as a retarded timing - result is less power

Once again, could we have some quantitative values? In terms of time, from which we can work out the phase angle.

http://query.nytimes.com/gst/abstrac...D0405B878DF1D3

I think our understanding of the combustion process has progressed a bit since then! (How did you even find this article!)

http://smallengineinformation.com/?page_id=411

Nothing really relevant to our discussion here. Essentially some observation on (really) small engines.

http://www.clubcivic.com/board/showthread.php?t=201999

Talks of a DIY method of checking for a spark. Once again, fail to see the relevance to our discussion.

Regards
Sutripta