Henry964

I canīt find here the 3 electrodes spark plug for my 964 (FR5 DTC)
My only options are to buy Bosch Super 4 spark plugs (4 electrodes) here at a very good price or to buy the originals from the states and have them delivered here.
My only fear of trying the newer plugs is that they could possible not work right in my car. Some say they are better plugs, some say they are the same, some say they could be dangerous in an old engine.

I found the newer ones (Super 4) in european Bosch catalogs as the right plug for our cars but still Iīm not sure

Indycam

What # is on the bosch super 4 ?

"some say they could be dangerous in an old engine."
I've never seen / heard of a dangerous spark plug before .
So I wonder what they are talking about .

Check this thread out ,
https://rennlist.com/forums/showthre...&highlight=ngk

Henry964

the number of the new plug is FR 56 and my mechanic - who I trust a lot - says to never use other spark than what the factory ordered (in 1993) to avoid problems so he wants me to buy FR5 DTC from EEUU.

amr89c4

In the FWIW department, I think the only way a spark plug could be dangerous is if 1) someone put in too long a plug (reach) as it might kiss a piston or 2) the wrong heat range sparkplug, which could cause piston damage if the plug runs too hot from incorrect insulator properties or 3) if the plug is too cold, then the engine will likely run rough at idle and foul plugs as the plug isn't running warm enough to keep itself from wet fouling.

Either way, whoever chose and installed the plug is at fault for not installing the correct plug to begin with.

Having said that, todays ECU controlled engines diminish the risk of 2 and 3 as the O2 , temp and knock sensors do a pretty good job of managing screwups. Still, why risk it by tempting fate. Back in the days of carburetors, it was certainly a big issue. Today, I do not see the electrode count/pattern causing a problem unless there is poor fuel distribution into the cylinder. On a twin plug 3.6 it should not be an issue in my opinion, which is worth what you paid for it.

Disclaimer: All bets are off with any "Miracle Wonder Plugs" that show up in the market from time to time. Stick with the big boys on sparkplugs is my advice.

Indycam

"2) the wrong heat range sparkplug, which could cause piston damage if the plug runs too hot from incorrect insulator properties"
Have you ever seen this actually happen ?
The plug gets so hot that it causes preignition , the motor runs very badly , and damages a piston before the owner fixes the problem .

"1) someone put in too long a plug (reach) as it might kiss a piston "
Washer , nuts and bolts are "dangerous" if dropped down the intake .
Its not the plug thats dangerous , its the fool who puts in the wrong reach plug .

Blu RS

"What # is on the bosch super 4 ?"

The number on the side of the Bosch FR56 is: R6 782

amr89c4

Hi Indycam,

No, I have not seen it on a Porsche, but I am relatively sure it has happened or could as reference books mention it. I have however seen it on 4 stroke marine stern drive engin(Fords, Chevies etc) as well as 2 stroke outboards (Evinrude, Mercury, Yamaha etc) which is where my 35 year technical background is.

Many other things can contribute to piston damage beside incorrect spark plugs, such as overheating, overadvanced timing, poor fuel quality or any combination of contributors.

It is relevant to all engines including Porsches and I was really trying to offer insight to the question of "how can a sparkplug be dangerous to my engine". So the answer is accurate and not specifically aimed at Porsches. I also noted that with modern (big brother watching out for anomolies or stupidity) ECU controlled engines the issue is not as "Dangerous" as it was in the dumb carburetor days.

Hope that clears up what I was trying to say with my post.

amr89c4

Oh yeah, the most calculated last words an outboard engine jockey says right before the piston melts from a lean condition is "Man, this thing was running better than it ever had, right before it seized!"

Indycam

Are you doing outboards now ?
I've got lots of questions for an outboard tech that knows them inside out .
Do you sell parts , omc parts ?

amr89c4

Indy cam....pm sent

tbennett017

Or like in my first car ('62 VW Beetle 6 Volt..) with a brand new 12 volt battery in it...

Indycam

Its Smoken !
Thats the "Hot" set up !