Single elektrode spark plugs for M50?

[Morgenster]

Hi guys,

I've been looking all over the web and I just can't find a partnr. for single electrode plugs for my M50 (at least not chez Bosch or NGK).
Does anyone have a reference?
The LPG specialists I went to explained to me that the single electrode plugs are way better for avoiding powerloss and backfires.
TIA

[Ross]

Bosch F8LDCR is recommended for my 2.5 M50

[Morgenster]

Yeah I know those are recommended, but I'm pretty sure those are two-pronged. I need single prong that can be gapped.

[BMWCCA1]

I've run across plenty of M50TU (US) engines running the Autolite 3923 plug (about $2 each, USD) and I can honestly say the cars ran great and got superior fuel economy before I changed them out to BMW OE NGK or Bosch plugs with multiple tips. I'm not saying I endorse or use them myself and I did change them just so my customers wouldn't think me a hack, but I was impressed driving cars that had been using the cheap Autolites for quite some time with no problem. YMMV

[Morgenster]

I've run across plenty of M50TU (US) engines running the Autolite 3923 plug (about $2 each, USD) and I can honestly say the cars ran great and got superior fuel economy before I changed them out to BMW OE NGK or Bosch plugs with multiple tips. I'm not saying I endorse or use them myself and I did change them just so my customers wouldn't think me a hack, but I was impressed driving cars that had been using the cheap Autolites for quite some time with no problem. YMMV

Can I obtain those autolites in Belgium?
Am I to conclude that there are no single electrode plugs for the M50 manufactured by Bosch or NGK?

[Tiger]

http://www.ibmwr.org/r-tech/oilheads/non_oem_spark_plug_options.shtml

Denso 5304 (according to autozone.com)

Denso Cross Reference on Autolite 3923 below
Denso K20PR-ZU11
Denso PK20-PR11
Denso IK20

NGK (According to their cross reference)
BPR8ES

NGK BKR6EVS11 (from a good source of crossreference to Denso K20PR-ZU11)

Can't find Bosch number that easy... but with above info... you should be able to find one.

[Morgenster]

Very helpful indeed! Thank you very much!

[Jon K]

NGK BKR6E $1.77 ea at Advanced Auto (part number 6097 there)

I have a few...

http://www.blowneuroz.com/mygallery/Miscellaneous/boxoplugs.jpg


They work great, its just that tuning my engine in the winter was a pain on them ;)

[Morgenster]

Why was this a pain?

[Jon K]

I tuned my car in 5 degree weather....

[Tiger]

His car is fully modified M50 with monster turbo

[Morgenster]

I got the part about the monster turbo long ago ;). I was thinking they were hard to gap right for the engine. Kudos to Jon for the green monster. I am envious.

Jon, in the picture I see heat rating 7 on those plugs. Do I get 6 or 7? Some say this matters a lot some say it doesn't.

[Morgenster]

bump.

[Jon K]

I got the part about the monster turbo long ago ;). I was thinking they were hard to gap right for the engine. Kudos to Jon for the green monster. I am envious.

Jon, in the picture I see heat rating 7 on those plugs. Do I get 6 or 7? Some say this matters a lot some say it doesn't.


Sorry - you get 6's, I tried 6's but I use 7's.

[Morgenster]

I figured something like that with you using the turbo and all but I wasn't sure and now I am! Thank you very much!

[Morgenster]

OK, now I have the plugs and I've been told to gap the to 0.7mm (0.028inch) instead of the stock 0.8mm (0.032inch). That's to avoid backfires I've been told. Any idea what effect shortening the gap will have on petrol performance? The gap is supposedly more suitable for LPG.

[Tiger]

Minimal effect for petrol use. Don't worry about it.

Normally, if you have strong ignition system and wants more power, you would increase the gap... forcing the coil to put out more voltage to spark the plug. More power to the spark means stronger ignition of fuel and that means more power.

The problem with alot of cars is that they had weak ignition system... the single coil type. The OEM were good for sweet powerband section only and drops off rapidly toward high RPM. To correct this, aftermarket coil had to be installed... add an aftermarket ignition computer to force max voltage trigger along with much wider gap.

In your case with individual coils, don't worry about it... just gap according to your LPG use.

[Morgenster]

I get it better now. How much of a difference would 0.1mm make anyway?

[Tiger]

From fuel mileage point of view... nothing. From Horsepower point of view? Can't tell a difference... Now if you were racing along the track... maybe a few seconds.

Really... you can't tell.

[Jon K]

I run 0.025" gap in my car with the turbo, because at WOT and boost I can blow the stock gap out, meaning misfire and then fire out the back. So, with 0.025" (lower than it need be honestly) I don't have that issue. I can run anywhere from 0.025" - 0.027" but I rather just go on the smaller side.

[Tiger]

Whoa... fire out back!? I know turbo, super or LPG is different... probably because of the pressure. That makes sense... what I discussed above is for standard normally aspirated engines. I learned all this stuff from Jacob Electronics... maker of those aftermarket ignition products. Their book is very very informative.

I learned their stuff back in 93 and applied it to my MB... it really does work.

[Morgenster]

Well I just finished some reading and it seems the LPG raises the spark requirements somewhat. Meaning that required voltage is higher and combustion is harder to achieve. Closing the gap somewhat would make it easier to ignite and I'm thinking also keep the plug from heating up too quickly (causing backfires through the intake).
On a sidenote regarding other plugs and multi-grounds: even NGK is now saying multigrounds do nothing for performance or idle stability and the advantage of a single electrode is better spark propagation. Although I guess now they're saying it to sell Iridium plugs.
I'm going to put them in this afternoon and then I'll report back on performance. Idle at running temp had the annoying habit of missing once or twice or being slightly rumbly (whilst running on petrol, not LPG). The current plugs are dualground Bosch plugs.

[Jon K]

NGK is a long time believer of single ground plugs - their race plugs (what I run) are single ground as are their v-grove and standards. The gap has very little to do with the heating of the plug. And a hotter than ideal plug does not backfire through the intake, it cause pre-ignition/detonation.

Run a set of BKR6E you wouldn't be disappointed.

[attack eagle]

Interesting thread as I want to change my plugs soon to a single electrode NGK.
NGKs were the best plugs I ever tried on my MGB and toyota 20R.
The BPR6es and BPR7es are the absolute proven plug on DSMs.

[Morgenster]

Well from watching the MPG indicator on the trip home: slight improvement over the dual electrode bosch plugs and those were just 1000k miles old.
Will see what happens when when the first effect of the DME reset wears off.

[Morgenster]

Oh and slightly smoother idle.
I guess there's only so much you can hope for when your engine has 288k kms on the clock.

[Chris'91'525i]

NGK is a long time believer of single ground plugs - their race plugs (what I run) are single ground as are their v-grove and standards. The gap has very little to do with the heating of the plug. And a hotter than ideal plug does not backfire through the intake, it cause pre-ignition/detonation.

Run a set of BKR6E you wouldn't be disappointed.


Are the NGK BKR6EK 's twin electrode plugs ? I was going to use these to replace the Bosch plugs I now have.

[Tiger]

These are single electrodes... check beginning of my post for some article about it.

[attack eagle]

Are the NGK BKR6EK 's twin electrode plugs ? I was going to use these to replace the Bosch plugs I now have.
according to NGKs website they are.

[Morgenster]

They're the same specs as BKR6E and the extra 'K' indicates dual electrodes.