I'm encouraged by Bosch to sell their product, but I still won't "+4" anything that didn't come with those from the factory.

 

Evidence -
Well,
The head gaskets were blown.
I am not exactly sure why they were blown. Blown via the previous owner.
But one thing I know..
Putting in HOTTER plugs does not help pre detonation problems.

Plus previous owner may have run regular gasoline in it.
Hard to tell.

Land Rover spent A LOT of money to test and qualify plugs which came OEM in the rover.
That is what I use.

Something as critical as detonation of gasoline in a cylinder should be taken seriously.

When they hype up - Bosch Plat plugs can deliver a hotter better spark - -yes,
I bet they do.

And that may be the problem partly - with head gasket failure.

I for one - will not be a test subject for these plugs..

Maybe running regular gas or Midgrade - cheaping out on the gas and running these plugs causes pre detionation. Who really knows...

Rover does not require premium gasoline "for the fun of it".
It is because - under the best of conditions "there is already a pre detonation problem"

The premium gasoline has a retardant in it to make it burn slower.

By putting in hotter plugs - you are messing with this careful balance - which Rover spent a lot of money to characterize and figure out in the first place.

I leave automotive engineering to the experts.

If someone can put a probe in the cylinder and watch the wall of fire burn
and qualify the Bosch Plat plugs are fine - then so be it.

I'll remain cautious and conservative.

 

First I don't completely understand why predestination would cause blown head gasket. I understand what your trying to say though. Second I highly doubt that's the reason these have head gasket problems. Bash plugs. Yes they should run premium but to say land rover spent a bunch is research of anything other than traction control is bull.. They tell me to put premium in my v6 lr3 the same engine the ford explorer uses. It's the exact engine..

I don't see what makes them any better but land rover + research = no

 

Jfall,

which ngk did you use? I tried bosch +4 and it f'd up my idle and predetonates, even with StI 8mm wires

 

The head gaskets fail around the crown due to higher than safe temperatures.
Once the crown is cracked, then the crack simply continues thru the gasket.
If this is on 1,2 or 7,8 you get the combustion gas in the coolant issue.

This article is rated "R" for please read it.


Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events.
The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieseling, when it causes the engine to carry on running after the ignition is shut off. This effect is more readily achieved on carbureted gasoline engines, because the fuel supply to the carburetor is typically regulated by a passive mechanical float valve and fuel delivery can feasibly continue until fuel line pressure has been relieved, provided the fuel can be somehow drawn past the throttle plate. The occurrence is rare in modern engines with throttle-body or electronic fuel injection, because the injectors will not be permitted to continue delivering fuel after the engine is shut off, and any occurrence may indicate the presence of a leaking (failed) injector.[3]
In the case of highly supercharged or high compression multi-cylinder engines particularly ones that use methanol (or other fuels prone to pre-ignition) pre-ignition can quickly melt or burn pistons since the power generated by other still functioning pistons will force the overheated ones along no matter how early the mix pre-ignites. Many engines have suffered such failure where improper fuel delivery is present. Often one injector may clog while the others carry on normally allowing mild detonation in one cylinder that leads to serious detonation , then pre-ignition.[4]
The challenges associated with pre-ignition have increased in recent years with the development of highly boosted and "downspeeded" spark ignition engines. The reduced engine speeds allow more time for autoignition chemistry to complete thus promoting the possibility of pre-ignition and so called "mega-knock". Under these circumstances, there is still significant debate as to the sources of the pre-ignition event.[5]
Pre-ignition and engine knock both sharply increase combustion chamber temperatures. Consequently, either effect increases the likelihood of the other effect occurring, and both can produce similar effects from the operator's perspective, such as rough engine operation or loss of performance due to operational intervention by a powertrain-management computer. For reasons like these, a person not familiarized with the distinction might describe one by the name of the other. Given proper combustion chamber design, pre-ignition can generally be eliminated by proper spark plug selection , proper fuel/air mixture adjustment, and periodic cleaning of the combustion chambers.[1]

 

That's not evidence.
What's your evidence that the Bosch Platinum+4 plugs in your engine were a hotter heat range spark plug than recommended by the factory? For those who don't know, a "hotter" than required plug is not isolated to the P+4 - the use of any plug in an OEM stock engine which is hotter than called for can cause preignition.
If regular gas was run in it (what year engine are you referring to?), then the computer (depending on year) would have been real busy retarding the timing. The proper P+4 plugs wouldn't care about the gasoline octane rating.
What proof do you have of this? Sounds like an assumption. If this mindset is used, then one could say Bosch spent A LOT of money to test and qualify plugs to meet or exceed OEM specifications for Land Rover engines.
This just strikes me as funny. As if people don't take it seriously. And you're incorrect - it's the air/fuel mixture that's being ignited.
P+4 plugs have a different style of spark. Your ignition system is sending the same amount of energy regardless of the plugs. That different style/type of spark and materials is what makes the difference. It's not a hotter spark - it's a differently orientated spark which may have slightly more energy due to less resistance of the materials used (platinum versus copper, etc.)
We're all entitled to assume what we want. Assumptions are not evidence, though.
These plugs have been on the market for years. There's no need for test subjects.
There are many known reasons for preignition. Why are you so convinced your engine blew a head gasket due to preignition?
There is already a preignition problem? What??? There's no problem. Depending on the year, your computer has an ignition curve/mapping that is designed to get as much safe power from the engine as possible - the combustion ratio and ignition curve require the premium fuel. If the ignition curve were scaled back (resulting in a loss of power), these engines would be able to get by on regular gas (that's what's going on when the computer is retarding the timing when knocking is detected due to running lower octane gas).
Are you talking about a hotter heat range plug here? If so, same question as before - why do you think the plugs you had were of a hotter heat range than specified by Land Rover? If you think the spark created by the P+4 was magically "hotter" when your ignition system is sending the same amount of energy, it would be only be a matter of materials used to construct the plug which may contribute to a stronger spark (less resistance in the plug allowing more of the ignition system's energy to reach the tip of the plug) and/or a design difference (which the P+4 has in comparison to a standard plug). My humble opinion is that any increase in the strength of the spark due to the P+4 design and materials is not going to cause dramatic, negative effects. However, there are many folks who report issues when switching to these plugs, which is curious.
The technology exists for this. Check out E3 spark plugs - they're pimping the high speed imaging used to capture the flame kernel propagation. It's really clear from the pictures that the E3 contributes to faster propagation than a standard plug. I've never seen, nor sought out, if there's photos for the P+4 - it'd be neat to see, given all the drama on LR boards over the P+4 plugs.

Good times!

 

my 04 runs quite well with the bosch plat +4's.

 

Okay I put my +4 Bosch Plat Fusions in today and took here on a 60 mile drive. She ran like new for about 45 miles and then It sounded like I had a exhaust leak. The box says to torque each plug with 20 lbs. I only did as I always have done and did it till tight. Do I really need torque these plugs? Noise is from drivers side. Any advice?

 

According to the Bosch website, the recommended plug for a 4.0L Discovery II is the model 6702 or 9652 which both have the same heat range (8) as the 4418 +4. In addition, they state that they have tested the recommended plugs on the actual vehicles with internal thermocouples.

By the way 'heat range' for spark plugs refers to the ability of the plug to dissipate heat, not the heat that it creates.

In any case, the heat range for the +4 should not be an issue. Since the engine management system on the DII was designed for Bosch sensors I would tend to trust them on this.

 

Just to set the record straight, Plus 4's don't predetenate nor do they cause our head gaskets to fail.
Our head gasket have always fail, most usually when running the standard Champion plug from the factory.
Some people love to hit on Plus 4's with no first hand real substanical proff just because they read somewhere where someone else decided they didn't like them.
If they were a bad plug they wouldn't be one of the world largest plug manufactures in vehicle like the BMW and Mercedes.
I have run them in 3 different vehicles over the last 20 years with great success and no misfires.
Buy and install a set, if you don't like them Bosch will replace or refund your money the first year.