[TNTRower]

Hi guys!

Here is a question that is sure to start some spirited discussion.

What effect will gapping the plugs to .39 have?

Here is the background...

I changed the plugs about 4 months ago. I used the NGK's that OhLord :bowdown: suggested. (By the way they work great). When I got them I was checking the gap on them and they were all .39. Well the specification is .32 so I dutifully regapped all 12 to the specification. I have noticed that my mileage seems a little low compared to others around the site (22mpg for a highway trip of 640 miles). I attributed that mostly to the fact that I had the cruise set between 75 and 83 most of the way. I have been wondering though if the bigger gap might not produce a considerably cleaner burn and thus an increase in mileage.

What are everyone's thoughts?

Drew

 

[ohlord]

OEM

gap is .39-.40(1mm) where did you come up with .32?
never gap plat plugs leave them as gapped out of the box.it is a high energy ignition system and closing down the gap will stuff the spark. Also to anyone else never use the multi tip plugs.
ohlord:bowdown:
buy 12 more and install them

 

[TNTRower]

The Owners Manual

My owners manual says on page 150

"Electrode Gap 0.032 in (0.8mm)"

That is where I got the number from. Does 0.032 mean 0.039?

Drew

P.S. See Spec Sheet from Manual attached

 

[techyiam]

Hi guys!

Here is a question that is sure to start some spirited discussion.

What effect will gapping the plugs to .39 have?

Here is the background...

I changed the plugs about 4 months ago. I used the NGK's that OhLord :bowdown: suggested. (By the way they work great). When I got them I was checking the gap on them and they were all .39. Well the specification is .32 so I dutifully regapped all 12 to the specification. I have noticed that my mileage seems a little low compared to others around the site (22mpg for a highway trip of 640 miles). I attributed that mostly to the fact that I had the cruise set between 75 and 83 most of the way. I have been wondering though if the bigger gap might not produce a considerably cleaner burn and thus an increase in mileage.

What are everyone's thoughts?

Drew

Over the decades, many enthusiasts have tried larger gaps. Some with more success than others. MSD has a website with some good info to glean from. There are some posters there who have shared their experiences with larger gaps. NGK is also another website for info. Ditto Bosch, Denso, and etc.

NGK Spark Plugs USA

Welcome to MSD Ignition

Some ignition systems are not compatible with larger gaps. Even though other ignition systems will work with larger gaps, it isn't always better since after a short while, the performance gain will be lost.

I believe the ignition system equipped in your 1998 E320 uses high tension leads. I would suspect the resistance would range in the hundreds to thousands of ohms. Usually for ignition systems that use high tension leads, bigger gaps can be used.

For coil-per-plug ignition systems (no high tension leads), the recommended gaps are usually smaller. ie. 0.032" for a 97 E420.

Incidentally, NGK recommends 0.039" gap for your vehicle. You can go to their website and verify it for yourself.

Another good website is Spark plug, Spark plug wire, spark plug gap, spark plug cross reference and ignition wires at Sparkplugs.com

You can re-gap your spark plugs with no lost in performance or life.

Usually the benefits that accompany a stronger ignition system performance is better throttle response, better small throttle opening acceleration, and better fuel economy.

Are you using the NGK G-Power series spark plugs (fine platinum center electrode, single-sided)? Also, if you don't mind, can you post a photograph of the tip end of one of your plugs, should you decide to take them out?

 

[ohlord]

I

have never seem an m112 or m113 with that gap.every manual is .039-.040 1mm they come out of the box gapped at .039
Bosch : Error
and from the ngk site
NGK Spark Plugs USA
BKR5EGP #7090 .039
ohlord:bowdown:
The part was eliminated or changed to FR8DPP33 bosch #7422 ngk 7090
http://www.boschautoparts.com/RB.NA...+GAS&Model=E320_&Year=1998&Make=MERCEDES-BENZ

1998 MERCEDES-BENZ E320 Spark Plug
so there in lies the problem
you could try gapping to spec,however platinum plugs should not be regapped unless you have the special turn tool.Like this
European Car: Jacobs Electronics Spark Plug Gapping Pliers
or be very careful the old school way.
ohlord:bowdown:
even the C32 AMG is .039

 

[TNTRower]

Very Interesting

Well I thought it was odd that NGK would come for my car at .039. I am just wondering why the manual says that. Maybe my vehicle is an early production run and MB changed the gap part way through. All-Data says .039 as well. Well it looks like I will be changing them out! Could be the problem with lower mileage.

 

[ohlord]

The

flame path would be shut down before it ever got a good start.I bet the correct gap does improve it.
ohlord:bowdown: