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WydRyd's Avatar
 
Join Date: Mar 2002
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Question Plug gaps with aftermarket CDI's?

I'd like to get a feel for what type of plug gaps you guys with aftermarket CDI's are running?

I'm going to install a Crane HI-6 & Coil tonight and I want to open up my plug gaps for obvious reasons.

I've heard of people running up to 0.045" gaps with these high power CDI's.

What are you guys running them at? Are you experiencing improved fuel economy, responsiveness and idle quality?

Discuss please
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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
Old 01-22-2007, 06:52 PM
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UPDATE: I installed a Crane HI-6 CDI and LX-92 coil last night and set my new W4CS plugs to 0.040". Haven't had a chance to take her out for a run as yet, but I'll do it this weekend and see how that gap performs in the upper rpm band @ 1.1bar. I think it should be OK, but any higher boost, and I may have to drop the gap down to 0.037" or so.

Again, I welcome input from some of you other guys running CDI systems.
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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
Old 01-24-2007, 06:37 PM
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Bump! No-one ever replied to this one

Does anyone here run an aftermarket CDI like a MSD or Crane?

I'm running 0.035" gaps on my plugs, but may drop it down further to between 0.028" - 0.032" so the plugs fire reliably at higher boost levels (~1.25bar).

Anyone got any experience with these CDI's in forced induction applications?

I know the factory manual says to gap the plugs at 0.6mm or 0.7mm (0.024" or 0.028" respectively), but that's for the stock ignition. For high powered CDI ignitions, I presume I can open up the gap bigger due to the hotter, more powerful spark?

The million dollar question IS, how much larger can I go? I don't really want to go TOO BIG and risk misfiring under heavy loads

If the factory recommends 0.7mm with stock ignition, I presume I should be able to go 0.032" without any dramas.
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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
Old 04-05-2007, 12:30 AM
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sudo apt-get purge 930
 
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I have an MSD that I still have yet to get running properly for a test. Bad idle, backingfiring, bucking at around 2K rpm. Plug in the Bosch and purrs like a kitten.
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Last edited by equality72521; 04-09-2007 at 09:02 AM..
Old 04-05-2007, 02:58 AM
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Must be bad wiring, or poor grounding or something. Have you double checked all your wiring cnnections etc?
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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
Old 04-05-2007, 04:19 AM
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Hello,
Interesting thread, I would like to hear if anyone have opened their gaps p also.

Les
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---Les Garten---85 930, Andial IC, GHL Headers, Fabspeed Dual, K-27 HF2, 3.4 JE Full Finned 7.5:1 CR, 964 CAM'd, Carerra 3.2 Manifold Cut/Flipped, Tec3r, Siemans 55#, GSF Fuel Rails, Clewett Crank Trigger, Clewett Cam Trigger,Dual Plugged, ARP Head Studs/Rod Bolts, Clewett Wires.Tial 46mm WG, Tial 50mm BOV, WEVO Shifter,934 Boost Gauge, Wideband EGO Sensor/Gauge, C2T Head Gaskets, '88 MB 300TE,BMW R100RT
Old 04-05-2007, 04:41 PM
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Hi Les. I think we're on our own here. All I can suggest is regapping it as large as you can without any misfiring under heavy/max load at your max boost setting. So, if you're spark output is reliable and consistent at max boost of Xpsi, then try opening it up a little until it misfires, and then drop it down a notch until it's firing reliably again. That's all I can suggest. At this stage, it's really just trial and error, since no-one here has really gone down this path it seems

As usual, each motor is different, so what may work in mine, may not work in yours.

I'm currently running 0.035" in mine and at ~1.15bar, I think I have misfiring/missing under heavy load in the higher gears. I'll try dropping this down to 0.032" and try it out for a week or so. If that fails, then 0.030", then 0.029", etc...

The idea is to run the largest gap you can whilst maintaining reliable ignition at max load. This will ensure optimum ignition of the A/F mixture and best economy etc...

Then again, the word "economy" goes out the window in heavily modified cars like ours

P.S: The gap will also depend on the type of plugs you're running. e.g: platinum plugs are easier to fire than silver plugs, so you may be able to run a larger gap with those. Lots of factors come into play here, even the type of ignition system you use, such as CDI, or wasted spark etc...
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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

Last edited by WydRyd; 04-05-2007 at 06:39 PM..
Old 04-05-2007, 06:35 PM
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