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I have been using SDS for way over a year now and have tuned it successfully on 5 or 6 different SAAB engines. I have made a quick change harness that lets me put it any LH 900 in about an hour. I've had it on a stock N/A, 2 N/A's with turbo, stock turbo, hipo built turbo and the rebuilt turbo I drive most every day. Everyday drivabilty was as good or better than stock, performance was significantly improved over the stock LH system and what I know they are capable of with the usual upgrades, but not having what I need to do proper WOT tuning, I am sure none were near their full potential.
In the beginning, I did report slight drivabilty problems, mostly it was with trailing throttle below 2K rpm. What made this difficult with my system, is that the MAP, (load), values fell into the same range as the idle values. I now know how to make that go away. The newer SDS systems, like VinceT. has, use a hybrid TPS program, that separates idle from the main program. Any system that has a separte idle circuit should be much easier to tune.
I live in a fairly warm climate, but we do get winter days into the teens (F degrees), occasionally. I've never had any difficulty tuning startup or warmup, tuning these values is very straight forward.
In the begining I had problems tuning WOT. It didn't take long for me to figure out that the 42lb/hr injectors that I was using, were not up to the task, I was using a 2.5bar fpr, this may have been solved with a 3bar fpr. My other problem was the stock T3 internal wastegate, Brad S. figured this out for me and based on one of his posts, I have worked my way around that problem. When I made this modification, I found another reason WOT tuning had been difficult. The elbow off the wastegate housing did not mate up well, there was a significant step where they came together. I believe this caused high velocity gases to miss the O2 sensor, causing me to think I was rich, when I was really lean. This may also have caused me to fault the 42lb/hr injectors too early in the tuning process.
The injector problem was solved by going to 85lb/hr injectors, I wanted something in the 55-65 range, but another SDS user gave me a deal I couldn't pass up. Using injectors this large brought on another tuning problem because I couldn't get it running well all around with the default SDS load values. Basically the load values should rise on a fairly even slope, except idle and cruise ranges, where the line may fall well below the basic load slope. The load slope for extra large injectors has to be about twice as steep to make proper tuning of the RPM (VE) values possible. Once the proper load slope is found, the RPM values are easy.
WOT tuning is by far the hardest and scariest part. It's almost impossible to do this on the street, I wasn't able to get my first WOT tuning done sucessfully until I took it to the drag strip. Dyno tuning is the safest and most efficient way to accomplish proper WOT tuning. The one session I did was cut short because of what turned out to be a bad plug wire, but the experience and confidence I got still made the trip worthwhile.
So, where am I at now? The engine always starts right up and can driven off as soon as you want. Warm-up is quick and once warm, it idles at a steady 750 rpm, pulls 18-19 in/hg vacuum and is way lean on the autometer
A/F gauge, usually off the scale. The tranny seldom sees the almost useless first gear. I cruise around residental areas that have speed bumps in third gear at 1000-1500 rpm with no glitchs. Most around town cruising is in fifth gear at 1500-2000 rpm with A/F ratio way lean. A/F ratio for hi-way cruising up to 3500 rpm, is on the lean side of stoich or way lean. Throttle tip-in is clean, no bog or hesitation. Fuel milege is better than stock, the engine puts out a dyno proven 200 hp and 189 ft/lbs of torque at the wheels with 6 psi of boost and that run was done with a completely stock exhaust, including cat, except for the open wastegate mod, turbo was stock with a .63 AR turbine housing. By the way, all the above is done with 87 octane pump gas, I do get better milege with 93 octane, but it is't enough to off set the 20 cent price difference and at the low boost levels I run, 6-12 psi, I feel no discernable difference in performance.
Just getting rid of the AMM really opens the door to performance and I attribute that to the gains I felt in otherwise stock engines. The last thing I'll say about stand alones, is that, timing is everything. There are many people out there that use SDS just for the timing control that the system offers. Few here would believe how much timing I run and there is no retard put in, till above 6 psi of boost.
I can't praise the SDS system enough, it's not the best or most versatile system, but it is very simple and the install is easy also. The value for the money spent makes it a contender for people like me, thanks, KevinK. for steering me in that direction.
posted by 165.121.22...
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