ngk iridium heat grade 7 HELP!
13 September 2009, 07:46 AM
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ngk iridium heat grade 7 HELP!
just got a set of these for my 99 sport, however I have read that heat grade 6 are for non tuned cars, and heat grade 7 are for slightly modified cars, I would say my car is running standard would these plugs still be ok or would I get pre ignition problems?
14 September 2009, 09:50 PM
#5
I don't think they will cause any problems per sa. You are more likely to suffer pre ignition if you run 6's in a modded engine than if you run 7's in a non modded engine, this is due to the fact that the 6's (a softer plug) in a modded engine will get too hot and therefore stay hot enough to ignite fuel left in the combustion chamber after you swich off.
15 September 2009, 08:40 AM
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Would 6's run better though? I do have an apexi induction and will be running the plugs with 8.5m magencor ignition leads and I am looking to uprate my fuel pump to a walbro 255 very soon along with a s/s decat exhaust system...
Last edited by Chrissy S; 15 September 2009 at 08:45 AM.
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15 September 2009, 09:17 AM
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lol nah not quite in my ears. Thanks, I will give them a try and see what happens then. I just didn't want to use them, for them to cause problems when I could just sell them as brand new and get a set of 6's. But if you reckon they are gonna give a cleaner/sharper spark then they should be alright 
22 September 2009, 09:22 PM
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off topic a little but what ignition leads should I get? Iv been looking at the magnecor sets, its either 8mm with 1.7mm conductor or (kv85) 8.5mm with 2.5mm conductor ? From what I have read they are both for road use however the kv85 leads tend to be used for tuned cars....
22 September 2009, 10:45 PM
#13
It's possible that a 7 will not run at the best temperature to keep the plug free of deposit build-up. whilst they may well be fine in your engine, they certainly won't give a sharper/cleaner spark! Until you start to get a lot more power from the engine, you would be wise to stick to the recommended heat grade.
JohnD
Last edited by JohnD; 22 September 2009 at 10:49 PM.
23 September 2009, 05:50 AM
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The OP says he's running a 99 sport, I imagine this is the naturally aspirated Impreza. I think 7s would foulup on this and you'd better stick to the 6 heat range. The non turbo plugs also have a bigger gap than the turbo plugs (11mm instead of 8mm), the NGK plugs for non turbo have -11 at the end of the spark plug model code as well.
23 September 2009, 07:23 PM
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grade 7 plugs are only for slightly modified cars anyway so I don't understand why they wouldn't work fine, perhaps if not better ? they sell these plugs for the 1.6/1/8 NA impreza's too so if they are made and work in these models surely they would be fine in mine? My car will be running with a 2.5" decat centre pipe, free flowing backbox, apexi induction, walbro 255 fuel pump and either 8.5 or 8mm magnecor ignition leads, dont know which ones to get yet....
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