Mitsubishi dealer :D

I wonder if it's not something as simple as carbon fouled plugs after having the mixture in the 10s.

Many years ago when I ran a hot turbo'd nissan race motor I frequently would carbon foul plugs from running too fat. Symptoms were similar to yours.

Did your motor ever pull clean to 7000 with boost since installing your efi?

Hmmm, why didn't I think of that! :)

Cheers

Hi Jim,

No, she had never run clean to 7000 with boost. I'm going to pull the plugs and will take a look (probably by the weekend) and try to play with different gaps and see what it will do.

I am lost in so far as I know a few who had succesfully ran similar set up (engine/EFI/twin plug/wasted spark) without issues - variable being SDDS coils (I think they are GM one?) and the actual ECU. But then if the ECU is controlling dwell & its inductive, I can't see a logical reason why things are that different :(

Yes, I believe that the SDS coils are GM or equivalent.

Regarding carbon fouled plugs, I think you may have to replace them. I don't think the gap resolved anything from what I recall, but that was lots of years ago - mid 80's.

I'm really clued-out by your discussion about your coils. I understand what's going on, but I had no idea that MS offered you the ability to mess with such variables.

Does your engine run clean to 7000 at very light load without any boost?

I would start with pulling the plugs, checking them for fouling and replacing them with appropriate heat range accordingly. If it doesn't work, pick two EDIS-6 coilpack on nearest junkyard. They are cheap and give good spark. Also, use MUX-ed ignition wire setup.

P.S. Did you check your ignition map vs. boost/RPM? It might be software problem?

I had the same problem , installed MSD 6AL and fixed the problem

Jim, I'll try to see if I can pull cleanly to 7000rpm without boost - not so easy when 2nd gear tops out at ~135km/h :D The MS is actually quite flexible considering the price, though lots of DIY work. With the datalog capability, it pushed me over compared to SDDS which I thought was great value.

Goran, re:ignition map - yes, I was thinking about that too. I'm running 18 deg @ .9 bar (195kpa) and 17deg @ 1 bar (215kpa) in the 5000-6500 rpm range. Plug-wise, I'm running NGK BR8ES. It works for me before EFI, but maybe I need to try 7 heat range? (Even though the engine now flows way more air, it is twin plug. Having to go hotter seems strange).

Was it on your 930 or 911RSR? And you were using MS too?
thanks...

On the 930 , using the CIS

Is that total advance? Isn't that about 6-7 degrees too low?

I think factory is 29deg @ 4000 with vacuum hose disconnected, but there's boost retard built into the distrbutor.

I'm not sure what the factory curve looks like exactly so rather run more conservative timing to start.

How are the oil temps when you do runs like this??
Your timing sounds like it's off, You can't really base your ign off the stock dist curve well you can but your twin plug now, probably with different cams, intake, everything. If i were you i would pull some more timing and make a run and see if it runs better, if not start by adding a degree at a time and working your way up. I would also fatten up your afr to give you a little more wiggle room. Then after you get the car to run clean , then you can go back clean up the air fuel. After it runs clean i would really hit a dyno beause wht power the engine is making will tell you everything. I've tuned two exact same engines, i built them, everything was the same, one engine took more 10 degrees to get to MBT. Also don't forget to read your plugs WB meters are great but the plugs and tell all if read correctly.
Good luck

An update...
Changed to new wires and re-connect back to "multiplex" mode (proper wasted spark configuration) and richen up the fuel a little. Now I can pull cleanly to 6500 RPM :D

However, in trying different things, I am quite sure I have blown one (or more) of my ignition drivers :( Probably because of the super long dwell (4ms) that I experimented with - heat probably killed the drivers as I'm now having occasional ignition drop out. Will have to replace them then test again.

Re:timing - as everyone suggests, I'm going to get her on the dyno to tune that. I have been waiting till I can at least run clean to redline before doing that. I picked 18 deg (@ >.6 bar & >4000 rpm) as one of my buddy with similar build (different ECU though) is running that for a few years without issue. Hence I used that as my starting point.

Actually, you would need less ignition advance with twin plugs to achieve optimal BMEP as mixture combust quicker "when lightened from two sides", so your conservative advance map isn't so bad idea after all ;)

You should do few dyno-runs to find your optimal timing but I wouldn't be surprized if it's in the ballpark of what you chose.