Engine likes more advance with iridium sparkplugs...?

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BigBlockMopar
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Engine likes more advance with iridium sparkplugs...?

Post by BigBlockMopar » Tue Aug 07, 2018 5:51 am

I have noticed my 318ci and also my current 360ci engines seem to like more advance when NGK iridium sparkplugs are used.
Talking about upto 5-7° more advance.
Anyone else noticed something like this in their setup?
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.


BigBlockMopar
Posts: 338
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
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Re: Engine likes more advance with iridium sparkplugs...?

Post by BigBlockMopar » Sat Aug 18, 2018 4:42 pm

Since my last post I've been quickening up the ignition curve which has woken up low-rpm range of the motor nicely.
(Also with my 318ci engine) I always had based the max. advance of 32° at around 2800rpm based on Steptoe's experience, but I've now been lowering that point from 2800, to 2500 to 2250rpm already, everytime with improvements found.
This curve comes much closer to what Jay Storer once wrote in his book.
I will try to limit my total advance to what Jay said to about 28-30° as a test. I'm currently at 34° max adv.

I will visit the chassisdyno again on the 3rd of Sept where I would like to try some ignition curves I've saved, to see which one the 11.3:1cr engine likes best.
Last edited by BigBlockMopar on Sun Aug 19, 2018 5:47 pm, edited 1 time in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

Tom68
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Joined: Mon Jun 18, 2018 2:46 am
Location: Australia

Re: Engine likes more advance with iridium sparkplugs...?

Post by Tom68 » Sat Aug 18, 2018 10:30 pm

I run fixed mechanical advance on my 327, last time I looked it would have been around 30 degrees, also running an additional 14 degrees of vacuum tapped below the butterflies.
Dual fuel (at the same time when the secondaries are open) so I use 98 octane petrol.

I'd run more timing but don't have a start retard option.

Don't know about different plugs, I used surface discharge once, just coz I had them, was running them with points triggered MSD, the MSD played up so I ran them with points kettering ignition. Never optimzed timing with the plugs in mind though.

BigBlockMopar
Posts: 338
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
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Re: Engine likes more advance with iridium sparkplugs...?

Post by BigBlockMopar » Sun Aug 19, 2018 5:38 am

I've personally always seen 'increased ignition advance' as a negative thing, as it means the combustion chamber appears less efficient and needs to start the fire earlier to provide max. burn at the right spot. But if it makes more power, then it must be good for something at least.
Newer engines with better designed cylinderheads get away with much less timing.

But if baffles me a bit why something simple as a different sparkplug could alter the engines 'like' for timing that much. Especially in a high compression engine.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

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