Bosch's 4-ground electrode spark plug vs stock?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Sep 8, 2003
19Nov2003 (UTC -8)

Anybody has good/bad experience with Bosch Platinum+4 spark plugs? I wanna put it on the TRD S/C'ed FZJ-80, with the goal of having better performance and fuel economy. It's got four electrodes, so that's supposed to give bigger spark and more complete fuel burn (see FAQ).


I currently am happy with the colder-than-FZJ80-stock Denso IK20 (which is stock for UZJ-100), and I guess the factory-spec Denso spark plug with Iridium tip will outlast the Bosch Platinum+4, but what are your opinions about it?
I prefer the ND plugs. Currently, I run a PQR20 (90919-01180) intended for the turbo MR2 in mine. It is Platinum and one range colder than stock, just like Toyota's factory forced induction motors.
I run the same plug as Cdan on my S/C 80. Monkey see, Monkey Do :D
I had the Bosch +4 plug in my 92 BMW 525iT, they worked fine, I didn't notice any difference from the stock plugs, until it started to run real rough a couple of months after putting 'em in. First thing I checked was the plugs, I found one of the +4 plugs had all four electrodes missing :eek: , kind of turned me off from Bosch plugs anymore. :mad:
19Nov2003 (UTC -8)

Hmmm, when compared to Denso (IK20) spark plugs as per Toyota specs, the platinum counterpart (i.e. FR8DPX) for the UZJ-100 has the wrong heat range (it's one step hotter) ! It's the same, but correct for the FZJ-80 though...

I wonder what Toyota spec does Bosch miss? But you gotta admit, that four-electrode feature is very attractive.
I have been running them in my Pathfinder for 3 years, and the Cruiser for six months. No problems. BTW, the difference in plugs is not in performance, but how well they work over the life of the plug (I am not talking about heat range, indexing etc, but performance between types and design). The 4 electrode plug should give more stable performance over its life.

My students and I have been discussing this subject this week as we are doing ignition systems. The coil makes one spark. There is no way the spark is going to change electrodes mid-spark. therefore multiple electrodes are worthless. In the case of split-fires, the quality of the plug itself is low, so you are worse off than you were before.
When the students ask about Bosch I have waffled. What I have said is I trust Bosch as a reputable company until I have evidence to the contrary. The only thing I could see is longer life with a stable gap, BUT anybodies platinum plug gives a stable gap for 100,000 miles. Will Bosch allow you to exceed that? Why would you want to? Will the plug come out of the head after 150,000 miles?
I promised to do some research this weekend to give them some answers.

Here's another rumor I heard today. There is talk of eliminating seperate coils and plugs. The next step might be a coil with electrodes that screw into the head.
20Nov2003 (UTC -8)

[quote author=Gumby link=board=2;threadid=7789;start=msg65876#msg65876 date=1069374059]
I promised to do some research this weekend to give them some answers.

Me too, me too!!! :D

The Denso IK20 are iridium tipped, therefore would resist fouling longer than any of Bosch's platinum spark plugs. The IK20 is factory spec'ed for the 2UZ-FE, and in the UZJ-100 maintenance manual, there is no mention of changing them ever! I guess it's become one of those new and fancy "if it ain't broke, don't fix" things.
Simple Physics rule: electricity takes only one path. The best of the 4 electrodes is going to take the spark - thus rotating electrodes' usage over life of the plug - which as a result yields longer replacement intervals.

I've been running on ND iridium tips in my truck for almost a year now - couldn't be better.

Aside from the longer/more stable life offered by the 4 tip plug, there is another advantage. Having the four tips located in close proximity to each other lowers the required kickoff voltage for the spark (I believe it is called a hall effect). In marginal ignition systems, this can help eliminate misfires (and is the reason that splitfires seemed to help some older cars with point systems and old plug wires).

BTW, multi-tip plugs are becoming increasingly common, newer BMW's use a three tip plug.

I have the +4 Bosch in the rig for 41K miles so far and the last time I checked (2 months ago) they looked fine and still perform the way they should. I have seen them on MB's., BMW's and others for will over 50K miles without giving the owners any problems or issues.

My $0.02


As mentioned above, there is only one spark. So having 4 tips doens't mean there are 4 sparks. I don't believe that there is any more longevity to having 4 tips to rotate the spark. I have used both the Bosch 4 and 1 tip plugs and have found that they both last the same. I now run the Denso Iridium plugs. THey were expensive(like $13 a piece :doh:) but i have noticed a difference, though only slightly.
Anectdotal data of no problems for 40-50K doesn't help much, although I do appreciate the input. I would expect any reputable platinum spark plug to last problem-free for 90-100K. The question is the Bosch +4 better than the others and for what reason. I just pulled a set of 80K mile motorcrafts from a F-150 and they looked fine.
cary - I could see there being some hocus pocus type reason like lower spark voltage for reasons I don't understand. I just haven't seen any data. I'm also not sure why a modern 100KV system would require it. Maybe better spark duration?

I'm thinking Hall efeect is something else just based on Hall effect pick up coils and how they work, but again, I don't know for sure.

Users who are viewing this thread

Top Bottom