Author Topic: thinking of changing the plugs on my 1.8t  (Read 1715 times)

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bog4rt

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thinking of changing the plugs on my 1.8t
« on: January 27, 2007, 09:33:29 PM »
i am at 45,000 miles and i got a 2000 a4 1.8t with apr's stage 3 turbo kit.  i have taken the plastic case off and know about the coils.  however my question was what should i gap my plugs at? .30? i have also heard that if you are producing >20 psi there could possibly be a bigger gap then normal? i would say my audi produces anywhere from 18-21 psi depending on how much i want to drop that pedal.  also wondering if i should stick with platnium plugs or get iridium? the diod on the iridiums is awfully small which concerns me, i drive my car on alot of short drives and only wait long enough for my turbo to relax before shutting it off. if i never get to "self cleaning temp" for the plugs the carbon build might affect the plug more. also i dont want to go iridium if there really are no noticible differences in pickup

jfrahm

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Re: thinking of changing the plugs on my 1.8t
« Reply #1 on: January 27, 2007, 11:00:44 PM »
Generally with more boost it gets harder to strike a spark.  Think of the Fuel/air as an insualtor, the greater the pressure the thicker the insulation.   Just to test a stock system you have to make the spark jump about 10mm outside of the cylinder head to see if it's strong enough to jump a .75mm gap in your head.  [This makes sense as the pressure in the head might be 200-240 psi under boost so there icould be 15 times as many air molecules between the electrodes under compression as there are with the plug on your workbench.]

If your ignition system is up to snuff you might be OK with the stock gap but I'd tend to the smaller end of the range or even a few hundreths of an inch less.

Platinum plugs are for long life, not performance.  I would go with copper.  Generally I think plugs should come out of a modded turbo motor pretty often so you can see what's up, so you toss a lot of plugs... or clean them and reinstall them I guess.

-Joel.
2001 Audi A8 Quattro 4.2l

Rocky Mountain Club B5

Re: thinking of changing the plugs on my 1.8t
« Reply #1 on: January 27, 2007, 11:00:44 PM »

kraut-sled

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Re: thinking of changing the plugs on my 1.8t
« Reply #2 on: January 28, 2007, 03:14:16 PM »
I would run the Bosch Plugs that were OEM in the UrS4 and other 20 valve turbo cars.  We put them in all the turbo cars we work on.

They are not cheap, but they last 2X as long as other plugs we have tested.

HTH Randy
Autobahn Premier Service
2105 South Kalamath Street
Denver CO 80223
303-935-9065

Denvernoob

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Re: thinking of changing the plugs on my 1.8t
« Reply #3 on: January 29, 2007, 05:54:34 PM »
randy installed those plugs on my car...they are the side-firing Bosch F5DP0R plug, and do not need to be gapped.  I spike 22+lbs of boost and hold 20ish on my k04, and they have worked flawlessly in both heat and cold...well worth the expense!
004.5 QMT6 Ultrasport Loaded
GIAC FX K04 w/ Injectors, K04-15
and about a million other big and little mods!

DenverPat

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Re: thinking of changing the plugs on my 1.8t
« Reply #4 on: January 29, 2007, 07:35:29 PM »
I've used the F5DP0Rs for years and love 'em.  BUT, why wouldn't you just use the plugs APR specs for their kit?  Wouldn't they know better than anyone what works best?  Hell, they designed and built it, and probably have more experience than anyone else with it.
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