Hey glad to hear Scott!

 

dan i cant find the plugs on vivid
can you post a link as to what you think would be best with an Ultimate Motor Werks software car

 

Steve - Trying to keep this a technical thread. I will PM you seperately. Thanks.

 

Thanks for the Rep Points. PM me who ever left it so I can return the nice favor

 

Dan: Thank you for starting this thread. This is what I've been looking for when I was grousing in another forum about the difference between the Bosche and Beru plugs. I still would like to know why Porshe still recommends the Beru plugs and routinely installs them in cars they service....yet most of the tuners and indies are pro-Bosche.

Is there any sort of dyno info or other credible research that shows the advantage of the Bosche over the Beru as it specifically relates to the 996TT?

Wes did address some of the issues I had about the actual difference in heat ranges, and that helps me clarify whether there really is a need for a switch to a colder plug for us guys who usually get a flash, better exhausts, wastegate kit, DV's...and call it quit at that. (oh yeah...the inevitable clutch comes in to equation too)....at any rate....this thread helped me put the issue to rest.

 

I do not have that answer Chuck, sorry. Never had my cars serviced at a dealer. We went with the Denso as a recommendation and have been very happy with them to date. I am sure the Denso, NGK, Bosch of the same heat range and plug type all do about the same.

 

I didnt' have mine serviced at a dealer either...did it myself...but in checking before the plug change at 32K, I called the dealership and checked with a couple folks who said to go with what Porsche recommeded....hence I picked the Beru. Then after the hassle of installing them, was told....Oh NO...you should have installed the Bosche plugs with a colder heat range. I think for us guys who don't track but do a DE day here and there and basically use the car as a DD with some twisties thrown in, the Bosche vs Beru doesn't seem to be that much of a difference....

 

if changing the plugs was not such a *****, then we could do some dyno test

 

Thanks for sharing!

 

I see you're a fan of Denso....but my initial question still remains unanswered...what or why are some pretty knowledgeable folks...and quite a few of them...recommending the Bosche over the Beru. Is there something that much better, or has this become a trend that just developed....What does someone like me, and I've given you my personal driving habits above....why does someone who runs around like I do need the Bosche over the Beru? Again...basic flash and usual upgrades...probably running 500-525HP....don't race.....what will I gain from the Bosche?

 

I don't know were to start but a few points I would like to make.

1. The service interval for the 996TT is 30,000mi due to the use of Copper Electrode Spark Plugs.
2. Regardless of plug tip material on over the counter spark plugs the core material will be copper.
3. How a heat range is determined given to me from NGK website.
http://www.ngksparkplugs.com/tech_su...2.asp?mode=nml

• Surface area and/or length of the insulator nose
• Thermal conductivity of the insulator, center electrode, etc.
• Structure of the center electrode such as a copper core, etc.
• Relative position of the insulator tip to the end of the shell (projection)

4. Now, for some information.

There is a reason the factory decided to put you through the pain of reducing the service interval from 60,000mi on your standard model 911 to just 30,000mi on your turbo. The reason for the change is the factory decided it better to switch to a copper tipped spark plug for your turbo 911.

Why did they make this decision?
Copper has the best Electrical Performance and the best Thermal Performance.

What do I mean?
10-ga wire Resistance Ohms/ft

Copper = 0.000999
Iridium = 0.00306
Platinum = 0.00579

Obviously, this only effects the "Tip" as all cores are copper. However, there is another important factor to resistance and that is size.

Wire Gauge Resistance per foot of Copper (Same theory of larger is less resistance applies to all metals)
4 .000292
6 .000465
8 .000739
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
24 .0302
26 .0480
28 .0764

So, in a simple answer copper tips are the largest and just like in wire this means the least amount of electrical resistance and as a result more voltage at the tip to fire to ground. Also, with a copper plug there is no metal type transition that also hurts electrical conduction.

We know that there is going to be less voltage drop from resistance from tip to tip of a spark plug (not counting ground strap!) If we use copper and since we know this and then we know that the resistance goes up as we start to produce more power. This makes it harder for the plug voltage to overcome the air gap resistance and fire to the ground strap (Closing the circuit). So if we run non-copper tip plugs we have less voltage to make this jump. If the flow is not enough on these non-copper plugs to jump onto the ground strap you misfire. So that leaves us with 2 possible solutions. We make the air gap resistance less by reducing the plug gap allowing us to not misfire or you switch to copper plugs.

Now, You might be wondering why don't I just reduce my gap? Well, doing so will result in a power loss for a few reasons. A stronger spark will help start flame propagation meaning that the stronger it starts the less timing you need to put in to maximize the engines performance. Since timing is the only other way to maximize propagation. However, since flame front speed is linked to cylinder pressure (along with things like AFR) as you increase pressure you also increase flame speed. So a strong spark in a way acts like advancing the timing but without the drawbacks.

Now, that I covered the electrical aspect of the plug its time to talk about the more important thermal aspect.

As I had mentioned Copper has the best heat properties of all the metals in question.

Thermal Conductivity
Btu / (hr - ft -°F)

Copper = 231
Iridium = 85
Platinum = 41.36

This means that copper can conduct heat at much higher levels then Iridium or Platinum but more important for our spark plugs. As mentioned earlier type of tip is a factor in determining a spark plugs heat range but the largest factor is the insulator. However, not all things are equal in this case because heat ranges are not determined by dynamic testing but static testing. Sadly, engines are dynamic when it comes to thermal environment. Since you have the heat of combustion and the cooling of an intake charge etc.

This is another reason to use copper because copper is the best in a dynamic environment since it will be able to transfer heat away from the tip into the core faster. The problem is that sometimes a colder iridium or platinum spark plug cannot move heat away from the tip fast enough. Since it does not have the physical size or metal properties to allow for such a quick transfer to occur. Since the plug is unable to move the heat into the body of the plug quick enough The plug can become super heated at the tip can cause detonation (even colder plugs).

Now, for obvious reason you can understand why I wouldn't use one of these Iridium plugs or Platinum plugs in your high performance 911 turbo. Since you want a colder plug you should be using FR5LDC but if you want to go beyond 1 step colder your in for a problem. There really isn't a whole lot out there in copper to suit that need of 14mm Thread, 19mm (3/4") Reach, 5/8" (16mm)Hex Size, Gasket Seat, Interference Suppression Resistor.

-Your Pal
Fishey