R400 Duratec: Spark plugs - NGK BR7EFS vs Ford TR6AP-13

[John Vine]

Those that know (such as Steve Greenald) say that the BR7EFS is a better choice in an R400D (and maybe other Duratecs as well) than the original Ford TR6AP-13 (also made by NGK).  The main reason appears to be that the former is a colder plug (by one grade).

I fitted a set yesterday.  Over a 40-mile run (mixed 30/40/60), I couldn't detect any difference.  But when starting from cold, the engine ran and then stalled.  With the Ford plugs, this never happens.  So, I'm wondering whether this has to do with the way the central insulator in the colder plug is more "shrouded":

Or could it be a function of the plug gap? The EFS is 0.65mm (25 thou) and the Ford plug is 1.3mm (51 thou):

I can see that the smaller gap will cause less coil stress and increase the coil voltage reserve, but would it be worse wrt ignition and propagation of the flame front?

Your thoughts appreciated.

JV

[colinchapman]

I think that the Ford TR6AP-13 is a platinum tipped plug with a set gap of 1.3 mm.

The NGK BR7EFS is a conventional spark plug.

NGK do an iridium plug for the Duratec- much better,but pricey!

[ScottR400D]

Duplicate

[ScottR400D]

Can't answer your questions but my R400D has the BR7EFS plugs. From new I believe though I did have RBTBs fitted last year by Luke Stevens; he may have fitted them but if so he never billed me for them. 

The gaps are about 1.0mm. The car starts and runs fine, no sign of stalling.  

[colindavies56]

Google the green plug company and throw the question at them. good luck. 

[John Vine]

Thanks, chaps.  Yes, the Ford plug is indeed Pt-tipped (and pricey too -- about £11 at a Ford dealer!).

IIRC from another post, Steve G recommended a 37 thou gap (just under 1.0mm) so I'm going to try that.

JV

[Jim 123]

John this is probably irrelevant.  From your photos it looks like both of the plugs are NGK.  Ford plugs have, to best of my knowledge, the logo FoMoCo printed on the shank of the plugs.

 

[John Vine]

green plug company

Thanks for the pointer.  I've just emailed them, so I'll post up what they say.

FoMoCo

Well spotted, Jim!  In fact, they came from a Ford main dealer about six years ago (and 20K miles), when I was trying to resolve a persistent misfire.  I guess Ford sell the FoMoCo-branded ones alongside the NGK ones?

JV

[colinchapman]

NGKITR6F13 - iridium spark plugs as listed by Burton for Ford Duratec.

£7.31 per plug .

[aerobod - near CYYC]

I've tried 6 different plugs in my R400D now, running each for at least 1,000km and come to the conclusion that there is no ideal plug, it depends whether you want the best start and pull from cold or the best high rev hard use plug. The following plugs start on the button in all temperatures above 0C, but tend to melt very slightly on the sharp edges during flat out track use and feel a bit sluggish at high revs, all are heat range 6 on the NGK scale:

NGK TR6AP-13, 1.3mm gap (double platinum tipped electrode and ground contact plug)

NGK TR6GP, 1.0mm gap (single platinum tipped electrode plug)

NGK TR6, 1.0mm gap (copper electrode plug)

These plugs all require a smidge of throttle for about 5 seconds when starting a cold engine below about 15C and a bit of nursing for the first 2 minutes of warm up, but feel much better on the track after continuous thrashing, they are all copper centre electrode plugs:

Champion RS9YC, 1.1mm gap (6.5 heat range on NGK scale)

Autolite AR103, 1.0mm gap (7 heat range on NGK scale)

NGK BR7EFS, 0.9mm gap (7 heat range on NGK scale)

I've currently gone back to the BR7EFS, as the quality of the Autolite and Champion plug construction seems to be lower than NGK and what I thought was a misfire at low loads with the BR7EFS plugs due to them being a bit "cold", turned out to be a failing coil pack.

From a price perspective, most of the plugs cost me CAD$4 to CAD$6 (£2.50 to £3.50) each from local sources such as Canadian Tire (the Halfords of Canada) but the AR103s were $10 (£6) each online and the TR6AP-13s are about CAD$9 (£5.50) each online.

[John Vine]

Very interesting, aerobod -- thanks.

How much do you think your altitude affects this?  Most of my use is under 250m. 

So far, I've found the TR6AP-13 (FoMoCo/NGK) to be excellent for starting from cold -- immediate regular tickover, with no throttle input required.  The BR7EFS led to stalling unless I applied a whiff of throttle.

I'm also beginning to think that the 1.3mm Ford gap puts a lot of stress on the coil-on-plug units.  I seem to recall that Ford now recommend a narrower gap (something like 1.0mm).  Having suffered one COP failure, I'm keen to avoid more.

JV

[Geoff Brown]

Always fitted NGK TR6AP-13 with 1.3mm gap. Cannot say I noticed any difference after changing from the original fit plugs.

Purchased from Halfords with L7C 10% off voucher NGK TR6AP-13s are about £7.50 each. Halfords stock number: 40859007000045. This number is for in store purchases & is ordered through the Euro Parts stock system.

The short number should work as well when ordering at the till: 408590070

[aerobod - near CYYC]

Hi John,

i don't think altitude affects my plug choice or starting ease to any significant degree since I installed a barometric sensor and swapped the ECU from the Caterham supplied MBE 992 (as it doesn't compensate for altitude with the locked map) to the 9A4 with my own modified map based on one supplied by SBD. 

- James.

[John Vine]

Halfords stock number: 408590070

Thanks, Geoff.  But when I search that number on halfords.com, I get "no results".   

JV

[ECR]

A google search for 408590070 directs me to an ebay offer at £5.45 .........

[John Vine]

Yes, you're right Roger!  That could be handy, given that Ford dealers charge £11+.

JV

[John Vine]

Well, I sent the Green Spark Plug Co my query:

...the standard Ford plugs are TR6AP-13 (NGK manufacture), with a 1.3mm (51 thou) gap setting. I find these a little on the hot side so I've replaced them with the slightly cooler NGK BR7EFS. These have a set gap of 0.65mm (25 thou). I'm now finding that the engine stalls from a cold start, although it runs fine when warm. Should I widen the gap, and if so, what gap would you recommend?

They replied:

The plug gap is set by what coil you use, so you will need a gap of 1.3mm. I doubt if you can widen BR7EFS to this width.

I'm not sure I understand the logic here.  Anyway, I widened the 0.65mm gaps to 0.9mm.  The engine no longer stalls from a cold start, and it runs beautifully, not missing a beat. So, perhaps that's a result.

JV