Spark Plug problem (newbie question)

[garymb]

I just changed the plugs for the first time on my recently acquired Elan. As far as I know I followed the procedure to the letter:

engine cold
gap 0.8mm
torque 18-21.5 lb-ft ( I went for 19)
a smear of copper grease on the thread of each

The engine now idles smoothly, and runs smoothly most of the time. Also seems to have a bit more power. However when accelerating hard it seems to miss over a rev range of 3.5k to 4k (seems to be when the boost really kicks in.) It comes out the other side ok but every time does the same thing.

I'm wondering what I could have done wrong. The connections all seem fine. Could it be that as I seem to get a bit of extra boost as a result of a non-stock drop-in K&N filter and sports exhaust I need to change from the standard gap? Maybe a bit wider?

Or has changing the plugs exposed another problem?

[ailwyn]

I thought the turbo was supposed to be gapped to 1.1mm?

Ailwyn

[ailwyn]

Which plugs exactly did you use? I was under the impression that all plugs are properly gapped at the factory?

A.

[garymb]

I thought the turbo was supposed to be gapped to 1.1mm?

Ailwyn

I have a turbo. I think the manual says the gap for NGK BKR6E plugs for turbo (which I have) should be 0.8mm?

plugs with suffix 11 or U11, 1.1mm. Or did I mis-read it?

[garymb]

Which plugs exactly did you use? I was under the impression that all plugs are properly gapped at the factory?

A.

I used NGK BKR6E.

the section on this site says it is a mis-conception that all plugs are pre-gapped at the factory. I narrowed mine to 0.8mm

What gap is everyone else using in their turbos?

[GeoffSmith]

Recommended plugs and correct gap. WikiLEC!

[garymb]

Recommended plugs and correct gap. WikiLEC!

Cheers Geoff

Assuming I did everything ok then, any ideas what the problem might be?

[GeoffSmith]

Personally, I'd chuck the old ones back in and see if the symptoms persist.

[tigerdog]

What gap is everyone else using in their turbos?

Smaug has a set of NGK iridium-tipped BKR6EIX-11. These plugs pre-gapped at 1.1 mm and specifically say not to regap because of the very fine centre electrode. Fires increased boost without missing even with this gap. Performance may also be attributable to the MSD coils and Kingsborne wires.

[Monty]

What gap is everyone else using in their turbos?

Smaug has a set of NGK iridium-tipped BKR6EIX-11. These plugs pre-gapped at 1.1 mm and specifically say not to regap because of the very fine centre electrode. Fires increased boost without missing even with this gap. Performance may also be attributable to the MSD coils and Kingsborne wires.

Thats strange i fitted BKR6EIX last month and they were already pre gapped to 0.8mm if any thing the 0.8 feeler gauge was tight

[tigerdog]

Thats strange i fitted BKR6EIX last month and they were already pre gapped to 0.8mm if any thing the 0.8 feeler gauge was tight

Not too strange. The BKR6EIX-11 suffix indicates the 1.1mm factory gap. Double check your part number; if it had a -08 at the end, that explains the difference. If it had no suffix, then we've just discovered NGK's default for this part.

[Doug]

this topic has come up before

my Elan had a plaque in the engine bay telling the recommended gap which is what I went with.

[paulwatkins]

From the holy grail......

[garymb]

I thought the turbo was supposed to be gapped to 1.1mm?

Ailwyn

This from the NGK website:

"While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need."


[/code]

[garymb]

From the holy grail......

thanks Paul. I'll have another fiddle today. I'm wondering if there's something about my set-up which means that I need to deviate from the standard gap for these plugs.

I'll try 1.1mm. If that doesn't work I'll put the old plugs back in (I checked them when I removed them, they were NGK BKR6E but the gap they were set to was considerably wider than 0.8mm) and see if the problem goes away-- and then have a ciggy and scratch my head for a bit

[Doug]

the gap widens on old plugs so the new ones should be tighter than the old ones if set right

never trust a plug gap -- test and set them all yourself!

[GeoffSmith]

never trust a plug gap -- test and set them all yourself!

Sound advice.

[Monty]

From the holy grail......

What does suffix mean?

Isn`t the 1.1 gap for the NA and 0.8mm for the turbo

[Enright]

That's how I read it too.

Perhaps Gary's leads are starting to get a bit marginal and disturbing them has pushed them a bit closer to failure.

Like Geoff says, I'd try the old plugs again just to rule the new ones out.

And I'd never trust that they're correctly gapped from the factory - all it takes is some monkey of a shelf-stacker to drop the pack in Halfords and you're knackered. Also, who says that the plugs aren't also standard for another car with a completely different gap?

[garymb]

Mystery solved: one of the plugs was cracked, so someone may have dropped one. I don't think I cracked it while installing it as I was ultra careful.

Plugs came form sparkplugsRus.com so may have been dropped while in transit I suppose, although they were well packed.

Oh, well, sorted now and a nice performance boost too.

thanks for your help all-- plenty of info for future reference.