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I've just recently got around to installing and hooking up the knock sensor for my SDS system. Like you, I felt and know it's pretty easy to program to where you really don't have to worry about detonation. Two things prompted me to get it operational, the increase in fuel cost and I've modified the stock wastegate to open to the atmosphere, thus increasing noise levels making it harder for me to detect detonation.
You'll find there is much that you can do with timing to improve performance, fuel economy and general drivability, but for now, just use a basic map for ignition, until you get the fuel issues sorted out.
There is much information on the net concerning ignition mapping, the page Ubipa posted recently is consistant with most of the info available. I'm saying that timing should generally increase with RPM and should decrease with load. Basically as RPM's increase there is less time for combustion to take place. So, up to a point you add advance as RPM increases to correct for the decrease in the time available. The total advance necessary based on RPM is mostly determined by the design of the combustion chamber and spark plug location. The further the flame front has to travel to complete combustion, the more advance needed. Our cumbustion chambers are relatively compact with a centrally located spark plug. 30-32 degrees total RPM based advance is relatively mild as timing goes and is appropriate for our compact combustion chambers with a centrally located spark plug.
Honestly, I suggest that you take turbo completely out of the picture for initial tuning. The best thing to do is to put a K&N style filter directly off the throttle body, letting the boost go to atmosphere. The next best option is to unhook the wastegate. Make WOT runs, you are looking to have zero manifold pressure or at least something in that area that remains steady through out the RPM range, this will allow you to set your RRM fuel values properly, which are a direct reflection of the engine's VE in N/A mode. After this you can evenly slope the curve between idle load and WOT load at zero boost.
In a perfect world you could continue this same slope for load the rest of the way through your MAP, but I doubt you live in one either. Up to this point A/F ratios around stoich are probably best, probably even up to 4-6 psi of boost, above that, thaings start getting difficult. Above base boost levels you really need to be on the dyno, with the wideband hooked up.
By trailing throttle, I'm really talking about a sudden closing of the throttle and the car pretty much coasting in gear. Things you'll run into are exhaust popping which is usually caused by unburned fuel getting burned in the exhaust, this is pretty easy to program out. The main thing I had trouble with was little surges, sometimes even lurches below 2K or as the engine drops below 2K. SDS has a fuel cut function below a programmable throttle position which only works at and above 2K, so once you drop below 2K, you are back on the program. This is caused by places in the load MAP below the idle ranges that dump just enough fuel to make the engine lurch. Cutting fuel right below the idle load settings isn't the answer, because manifold pressure will still flutuate into and back out of the idle load ranges. Retarding timing in the load ranges below idle makes these go away and still allows for a good transition back to idle or back on the throttle.
The throttle response problem you mention is probably just something you need to work out with whatever the Wolf system uses for it's accelerator pump function. Too much fuel here can bog you down just as easily as too little fuel. You may also try bumping up the load values just off idle. Later when you can really mess the ignition map, this will probably sharpen up some more.
posted by 216.128.129...
, Sat, 4 May 2002 18:53:44
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