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Join Date: Mar 2002
Posts: 3,563
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Spark plug gaps with aftermarket ignitions?
Anyone have any first hand experience with setting spark plug gaps using aftermarket CDI units (MSD or Crane) in a forced induction application?
Please see: http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/326382-plug-gaps-aftermarket-cdis.html#post3200373
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition 
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04-05-2007, 12:35 AM
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Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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I'm not going to comment on my gap as it's not a turbo like yours. Greater combustion psi demands greater spark energy vs mine. The greater the load on our close dizzy cap contacts the greater the chance of a crossfire among them. I know nothing of turbos.
i'm only good for suggesting you have very good CD positive and negative with dielectric.
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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04-05-2007, 04:18 AM
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Thanks Ronin. In natural aspiration applications, plug gaps of 0.040-0.045" can be used, but in forced induction configurations, obviously the plug gaps have to be reduced to reduce the likelihood of flame blow-out.
The honda ricer guys who run 19+ psi boost, set their gaps to 0.029-0.030", so I guess that may be a good guide for me. The factory recommends 0.6mm to 0.7mm for stock 930 turbo's with stock boost and ignition. With aftermarket CDI, I should be able to open up the gap by up to 0.005", so that would take me to ~ 0.032". Hopefully even with higher boost. I was just hoping someone on this board would have first hand experience with these things 
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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04-05-2007, 02:51 PM
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I'm with Bill
Join Date: Jun 2005
Location: Scottsville Va
Posts: 24,186
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In your aplication I'm not sure, but with the NA stuff .45 is too much. With an MSD unit and the gap of .45 the rotor has a tendancy to burn out.
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Electrical problems on a pick-up will do that to a guy- 1990C4S |
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04-05-2007, 04:12 PM
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Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
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call the manufacture. they know their system best and what it can do.
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86 930 94kmiles [_  _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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04-06-2007, 06:17 AM
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