example ign advance table for 3.2SS

[trond]

I am more or less ready to start up my new built 3.2SS 930/07 (small port) engine. It has stock cams, SSI and Dansk Sport, 98mm 10.5CR CP pistons and Megasquirt w/double EDIS ignition. I would be interested in seeing an example ignition map. For now I have looked at the 3D maps for the 964, but hard to read. I have set my preliminary map at 0 degrees in the lower RPM columns, 20 degrees at 3500 rpm WOT and 16 degrees from 4000 to 6500 WOT. Cruise range is at around 30 degrees (10 down from when I ran single plug).

I would like to see som example maps for similar engines please ? May not be that many with stock cams....

[Raceboy]

Using 964 is pointless as it is totally different due to twin-plug ignition. Twin-plug requires much less advance.

At idle set the advance to around 5-7 degrees (what the engine likes best), at low load cruise at least 30-40 degrees and at full throttle around 30-35 degrees but in order to have WOT angle tuned properly you would need a dyno (at least of low-compression and regular fuel n/a engine).

[trond]

I have twin plug. Just want something reasonable to start up

[prschmn]

I agree with raceboy about some advance at idle-it'll be lousy to start and generally unhappy
with less that 6 or 8 at idle. But I'd also run less at WOT-maybe 25 or so should get you to peak torque without risking detonation.

[mysocal911]

Originally Posted by Raceboy

Twin-plug requires much less advance.

Yes, but greater timing that can be used without detonation than could used with a single plug.
Remember, the only purpose of twin plugging is to achieve the desired increased torque without
a significant reduction in ignition timing at higher CRs that would be required when using a single plug.

[Raceboy]

Tuning ignition is always about MBT and having twin plug moves MBT much closer. With good pump fuel (not talking about 87ish US fuel but 93 that equals 98 over here) you will be way past MBT on twin-plug engine before reaching detonation treshold. Unless you run very high engine temps or something.
On the dyno 964 engine required like 24-26 degrees maximum to have best power, over that and it started making less.

But if you have twin-plug, 0-2 degrees at idle is good and as a starting point you can use cruise maps from 964, it is just a bit too retarded at WOT.

[fred cook]

I have a 3.3SS engine in my SC, built about 4 years ago. I am using the Electromotive XDi twin plug system. I have the timing set at 5 degrees initial advance, 24 total degrees above 3,000 rpm and a 4 degree retard at top end. Compression is about 10.8:1, using 964 cams, big port CIS and Carerra heads with large ports. With this timing setting, it starts easily, idles well and pulls strong up to the 7500 rpm ignition cutout point. Runs good on premium pump gas. When I first put the engine together, I had the initial timing set at 10 degrees but could not get the idle below about 1100 rpms. Dropping the initial setting to 5-6 degrees fixed that. With twin ignition, you should not need 30+ degrees timing advance at the top end. Others may have a different setup, but this is what works for my engine. Good luck!

[trond]

very good inputs here. Much appreciated !

[fred cook]

Another thing that I did was to put a push contact switch on the throttle linkage and wired it so that the cold start injector (valve) would be activated at full throttle. It is only open at full throttle and adds enough extra fuel to drop the A/F ratio from a bit over 14:1 (14.0-14.5) down to slightly over 13:1. Hopefully, this will be rich enough to avoid burning a valve or piston at full chat! I also installed a permanent mount A/F gauge in my car to use while tuning. Makes things much easier!

[Raceboy]

Why you need extra cold start valve? Can't you just tune it richer at higher rpm? Air cooled 911 tend to like quite rich mixtures at high load (like 12.8-12.9:1) due to lower BFSC compared to more modern designs. It aids with cooling too of course.

[fred cook]

Originally Posted by Raceboy

Why you need extra cold start valve? Can't you just tune it richer at higher rpm? Air cooled 911 tend to like quite rich mixtures at high load (like 12.8-12.9:1) due to lower BFSC compared to more modern designs. It aids with cooling too of course.

I did not add another cold start valve, just wired the existing one to give a fuel delivery boost at wide open throttle. Now, my engine runs close to the stoichiometric range (ideal air/fuel ratio) during normal driving but can enrichen the mixture at full throttle. The end result is an engine that gets good fuel mileage during street driving but is protected from a lean setting valve or piston burn.

[safe]

Originally Posted by fred cook

I did not add another cold start valve, just wired the existing one to give a fuel delivery boost at wide open throttle. Now, my engine runs close to the stoichiometric range (ideal air/fuel ratio) during normal driving but can enrichen the mixture at full throttle. The end result is an engine that gets good fuel mileage during street driving but is protected from a lean setting valve or piston burn.

But you have a Megasquirt!! Add more fuel in the base map at and near full throttle instead of rednecking a coldstart valve... Thats the beauty of EFI, its just a few tapps away on the keyboard!

[fred cook]

Originally Posted by safe

But you have a Megasquirt!! Add more fuel in the base map at and near full throttle instead of rednecking a coldstart valve... Thats the beauty of EFI, its just a few tapps away on the keyboard!

Trond has megasquirt, I have modified CIS!

[safe]

Originally Posted by fred cook

Trond has megasquirt, I have modified CIS!

Ah, sorry!