Spark plug gap

[8bit]

Have done some searches but not found anything really concrete so here goes. I've got Revo stage 1 (mapped in December 2011 so pretty recent software) with linear throttle map. I've got new coilpacks (latest 1.8T revision, red-top items) and NGK Iridium BKR7EIX plugs.

Had the car logged with Vagcom when on a dyno recently, zero CFs on all cylinders. On the road though I get a little bit of CFs and can feel a small flat spot about 3krpm. Had been running boost = 6 timing = 4, pulled boost back to 5 and timing to 3, which helped a bit but still there.

What gap should I set the plugs to?

 

[Deleted member 35798]

Hey dude, sorry I didn't reply to your text, been a busy day and just back onshore.

Check out this thread. http://uk-mkivs.net/forums/p/472890/3266009.aspx#3266009

I ordered the same as yours (one range colder), but haven't fitted them or checked the gap on them yet.

 

[8bit]

Hey dude, sorry I didn't reply to your text, been a busy day and just back onshore.

Check out this thread. http://uk-mkivs.net/forums/p/472890/3266009.aspx#3266009

I ordered the same as yours (one range colder), but haven't fitted them or checked the gap on them yet.

No worries mate, if you have a feeler gauge then would you mind checking the gap on yours before you fit em?

Had a quick scan through that thread yesterday, can't say I'm any the wiser for it, looks like folk have varying opinions on plug gaps!

 

[ibizacupra]

0.7mm is what I use here

 

[8bit]

Thanks Bill. I haven't verified the gap on mine yet but according to what I see online it looks like they're gapped at 0.762mm as standard - is that enough of a difference to cause problems?

 

[Deleted member 35798]

I don't have a feeler gauge but they won't be getting fitted any time soon so if you can get hold of one you're welcome to measure.

 

[8bit]

OK cool, cheers

 

[Deleted member 35798]

I'll be fitting mine this week and gapping them to 0.7mm as Bill suggests.

What do you think 8bit?

 

[8bit]

I'd totally forgotten about this thread

Did you check the gap on yours as delivered? AFAIK Iridium plugs are pregapped so in theory yours should be the same as mine. If yours are much away from 0.7mm then I might take them out and gap them. Be careful tho, not sure if you read the same but I gather that the Iridium is fragile.

Just re-read the above a bit more thoroughly and I can't see 0.062mm making that much of a difference but if it keeps det down a bit then it's not a bad thing!

 

[Deleted member 35798]

Not yet, but Clark will check them before fitting.

PSI Tuning advice a gap of 0.03" (0.76mm) on standard coils.

Bill advises 0.028" (0.7mm).

I guess there can't be much difference between the 2x settings? (0.06mm is not a valid answer )

 

[jonathanp]

I'm thinking of ordering some BKR8EIX's and 2.0T coils (mainly because they are cheaper)

In two minds as to keep them pre gapped at 0.028" or increase to 0.040"

Can anyone explain in basic terms why you would increase the gap and what benefit it gives you?

 

[8bit]

My understanding was larger gap means less pre-det, can't remember the physics behind it though. I certainly got less timing pull just by changing to BKR7EIXs on whatever gap they're set to as standard. Your car is heavily modified isn't it? I'd have thought you'd benefit from the 7 grade plugs rather than 8s.

As for coils, I got a set of 4 red-top ones for 1.8Ts from Awesome GTI, they were a fair bit cheaper than from Seat and no need for adaptors like the 2.0T coils.

 

[ibizacupra]

I'm thinking of ordering some BKR8EIX's and 2.0T coils (mainly because they are cheaper)

In two minds as to keep them pre gapped at 0.028" or increase to 0.040"

Can anyone explain in basic terms why you would increase the gap and what benefit it gives you?

i use them 7 and 8 eix at 0.7mm gap
I did'nt find any difference in running a larger gap.
tfsi coils

 

[Deleted member 35798]

What about for standard 1.8T coils Bill?

 

[Nautilus]

1. The factory gap on stock 1.8Ts is 0.8mm (0.032"). Factory plugs, PFR6Qs, are good for stock boost only, they are very hot for any chipped engine.

2. Usually the larger the gap, the better the burn (which should mean a small advantage in hp, less carbon deposits, less or no misfires, better fuel economy).

3. Normal or large gaps may result in extinguishing of the spark under high boost. The crappy quality of early, pre-2004 1.8T coils (part no. ended in L) made this obvious in normal driving, so common wisdom dictated the gap should be closed to 0.7mm (0.028") for reliability.

4. 1.8T coils from newer generation (part no. ended in R) on BKR7E plugs can and will hold spark at 0.8mm gap, and if everything is in top-notch condition to provide best burn (injectors clean like a medical syringe, no oil in the cylinder, perfectly clean fuel over 98 octane, no carbon on cylinder head), they will hold spark over 0.9mm of gap. I know this from the 2009-2010 winter, when I've pulled the sparkplugs to check, 2 of them were in the 0.8mm range, other 2 almost 1.0mm and the car did not misfire a bit and ran well.

5. Found out the story of the 2.0TFSI coils just after I've ordered a set of brand new 1.8T coils to replace my burnt older set. Apparently the people who experimented with them found no advantage in power at usual gaps, 0.7-0.8mm, just smoother burn, but earned a bit over 3% hp (15hp on a big turbo ~400hp car) by running large gaps, over 1.0mm, with 2.0TFSI coils.

The BKR7E plugs went into the engine gapped at ~0.85mm (too large for 0.8mm feeler gauge, too narrow for 0.9mm), and after painfully and costly solving the issues with my throttle body they ran perfectly, misfire counter to zero, even during 1.5bar WOT runs.

~Nautilus