[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?

[1self]

There should not be a problem with the plugs per se. One heat range hotter is also OK. Just reduce the plug electrode gap to the recommended because it's is 40% more than recommended. You will have misfire at higher RPM's if you keep this gap.

So, re-gap the plugs & you're good to go!

[VeyronSuperSprt]

Originally Posted by fighterace

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?

It's called playing with fire. Pun Intended. As the results would very much be the same.

You have selected a plug with a hotter heat range than that recommended. The effect of this in the long run would be burnt out valves and erratic working of the engine. Continual use would cause permanent damage to the engine.

If you like your car, get the original spec spark plug. Immediately.

[fighterace]

Originally Posted by VeyronSuperSprt

It's called playing with fire. Pun Intended. As the results would very much be the same.

You have selected a plug with a hotter heat range than that recommended. The effect of this in the long run would be burnt out valves and erratic working of the engine. Continual use would cause permanent damage to the engine.

If you like your car, get the original spec spark plug. Immediately.

OK. I'll err on the side of caution and replace them tomorrow itself. Hope that 50 odd kms will not do much harm. Two questions:

1. Is there an equivalent spark plug for the NGK BKR6E from Bosch (for the MPFI Zen)?

2. Which cars use the BKR5E-11 as i am straddled with a brand new set?

[VeyronSuperSprt]

Originally Posted by fighterace

OK. I'll err on the side of caution and replace them tomorrow itself. Hope that 50 odd kms will not do much harm. Two questions:

1. Is there an equivalent spark plug for the NGK BKR6E from Bosch (for the MPFI Zen)?

2. Which cars use the BKR5E-11 as i am straddled with a brand new set?

50 kms would not be an issue.

Is the plug BPR5E-11 or BKR5E-11 ?

[fighterace]

BKR6E is the recommended plug (for Zen Mpfi), I was given BKR5E-11. It must be a popular plug to be available so easily, or export rejects. Do Hyundai vehicles use them?

[Sutripta]

Originally Posted by 1self

One heat range hotter is also OK.

Agree. But with a few qualifiers.

Originally Posted by VeyronSuperSprt

The effect of this in the long run would be burnt out valves and erratic working of the engine. Continual use would cause permanent damage to the engine.

Theoretically correct. But don't really agree with such a doomsday scenario.

If the vehicle is driven the way most Indian vehicles are, (ie not in pedal to metal mode for any length of time), one range up should not cause any problems.

The manufacturers recommendation is a normally a safe compromise between the coldest which will not foul, and the hottest which will not cause preignition, under expected usage patterns.

Regards
Sutripta

[VeyronSuperSprt]

Originally Posted by fighterace

BKR6E is the recommended plug (for Zen Mpfi), I was given BKR5E-11. It must be a popular plug to be available so easily, or export rejects. Do Hyundai vehicles use them?

Yes, BKR5E-11 is used in Hyundai Verna, Accent and Santro. It is also used in the Mitsubishi Cedia and Lancer.

[1self]

Vehicles with a carburetor are much more sensitive to heat ranges of spark plugs than MPFI vehicles. In MPFI vehicles you can go 1 range up or down from the recommended without having ANY adverse effects on a healthy engine.

If the engine was already having other problems like overfuelling or overheating, then the engine becomes sensitive to plug heat range.

Also turbocharged & supercharged engines are much more sensitive to plug heat range than N/A engines.

In the Indian context, we already have cars which are de-tuned to the fuel we have available so spark plug heat range within 1 segment up or down does not matter.

[SS-Traveller]

Originally Posted by 1self

Vehicles with a carburetor are much more sensitive to heat ranges of spark plugs than MPFI vehicles.
If the engine was already having other problems like overfuelling or overheating, then the engine becomes sensitive to plug heat range.
Also turbocharged & supercharged engines are much more sensitive to plug heat range than N/A engines.

Why would MPFi / TC / supercharged engines be more 'sensitive' to changes in spark plug heat range? Would be glad if you can elaborate further on the reason(s).

[fighterace]

From my limited understanding of engines, a MPFI engine will be less susceptible to detonation if it has a knock sensor, an addition which is most important given the quality of fuel in our country, but it was an addition that most manufacturers made after getting back a few fried engines. So the question is whether the 2002 Zen has a knock sensor or not.

Also, I'd like to know whether Bosch has a plug which is compatible with the NGK BKR6E, and whether it is better or worse. Also, between Denso, NGK and Bosch, who makes the best mainstream, plain vanilla plugs? I don't want platinum/iridium plugs.

[Sankar]

@fighterace The 2002 Zen doesn't have a knock sensor. Is there any knocking in he engine after you've installed these plugs? Hotter plug can induce preignition, but only if its outside the tolerance limit of the engine.

Since you have run some with these plugs open one and check how it is. If the ceramic tips aren't scared pale white and if there is no knocking then there shouldn't be a problem. If the engine is experiencing knocking after the plug change i suggest you change back otherwise leave it as it is after a visual inspection of the plugs.

Reading spark plugs, suggest you do this once to clear the doubts.
http://www.ngksparkplugs.com/tech_su...qs/faqread.asp
http://suzukitu250x.blogspot.in/2011...our-plugs.html

Regarding mainstream plugs i would prefer Denso or NGK first and Bosch or Champion only if these aren't available.

[1self]

Originally Posted by SS-Traveller

Why would MPFi / TC / supercharged engines be more 'sensitive' to changes in spark plug heat range? Would be glad if you can elaborate further on the reason(s).

F/I engines in general & turbocharged engines in particular are VERY sensitive to the heat range of spark plugs. The main reason is that when the turbo spools up, it is pretty much uncontrolled, i.e. it goes from say 7000 rpm to 150,000 rpm in just a few seconds. To control detonation, manufacturers throw in a LOT of fuel to keep things cool in the cylinder.

Because turbo engines run hotter than their supercharged counterparts, this results in the spark timing is also retarded, to prevent detonation. This means that plugs are soaking wet in fuel, before firing. If the plugs are in a heat range too cold, they will foul up VERY fast. So, plugs need to be 'HOT' enough to prevent fouling & that the fuel evaporates from the sparking surfaces fast.

Because F/I engines run more air & fuel every intake stroke, their combustion produces a LOT more heat. This heat tends to be soaked up by the valves, plugs, piston & cylinder walls. The plugs have sharp edges along their earth electrods due to the spiral shaped threads. These sharp edges become glowing hot. At higher rpm's, there is not enough time for the plug to cool down before the next intake stroke. When the next air/ fuel charge comes in, it ignites on these hot surfaces, resulting in pre-ignition. To avoid this scenario, plugs have to be 'COLD' enough.

Hence it is VERY important to have correct heat range in F/I engines. In N/A engines, the temperatures of the combustion chamber is nowhere near what it is in an F/I engine, so it is much less sensitive to plug heat range.

[SS-Traveller]

Originally Posted by 1self

...To control detonation, manufacturers throw in a LOT of fuel to keep things cool in the cylinder.
...the spark timing is also retarded, to prevent detonation. This means that plugs are soaking wet in fuel, before firing.
...plugs need to be 'HOT' enough to prevent fouling & that the fuel evaporates from the sparking surfaces fast.
...To avoid this scenario, plugs have to be 'COLD' enough.
...In N/A engines, the temperatures of the combustion chamber is nowhere near what it is in an F/I engine, so it is much less sensitive to plug heat range.

Utterly here - I thought FI engines have a lot more accurate fuel metering, knock sensors to prevent pre-ignition etc. OTOH a carb engine will suck in loads of fuel and not be able to burn it too well when driving on wide open throttle. Also, carb engines can also be turbo- / super-charged, can't they?

Also, with FI, how does one get a soaking wet plug, when the fuel-air charge being sucked in by the cylinder is expected to be highly atomised? I thought that's a more likely scenario in a carburetted engine.

[1self]

Accurate fuel metering is in steady state conditions, not when the turbo is going from almost stand still to full song. Also, not all the fuel is atomised as it enters chamber..otherwise there would'nt be any wall-wetting of the cylinder bore, will there? Unfortunately wall-wetting with fuel does occur at higher rpm's. This is not limited to F/I, but is present even in N/A engines at high rpm. This is done to keep engine temps reasonable.

In a carby F/I engine, all the symptomes of MPFI F/I are present... only worse.