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For anyone who is interested, I sent a copy of the 94 aero timing map to SDS and asked them what they thought about me using those values to start with.
He thought that even though the 92 and the 94 were close enough stock... that the moficiations I made with intake, exhaust, intercooler, injectors, and turbo would make the 94 aero timing numbers obsolete for our tuning purposes, and he suggested his own methods for setting the timing, rather than using the stock saab values.
I figured i would post his most informative reply, for anyone who is interested in how he suggested running boost and timing...
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Hi Gavin,
I find way too many people run high boost and low timing and make fairly low power, the engine is much more efficient running more timing and less boost. Your old saab 2.0L engine running 20 psi with 34# injectors couldn't have made more than 250 flywheel hp because the injectors would have been running at 100% duty cycle.
A case in point about boost and timing- our 240SX turbo shop car runs only 5.5 psi but puts out around 230hp, I have no trouble keeping up or beating other 240s running double or triple the boost pressure because they have the timing pulled back near TDC under boost. At 10.5 psi, the car ran 115mph in the 1/4 mile with one tire smoking all the way through 3rd gear. Our 1.7L, 2 valve Toyota 2TC engines were reliably developing 360hp 20 years ago at only 15 psi. and my old clunky 20R Celica would run 13.3 at 102mph in the 1/4 mile with 205 tires, no LSD and no intercooler 25 years ago, my 4AG GTS Corolla would run 101 in the 1/4 also with 205s, no LSD and only 7 psi.
I'd like to help you more but the truth is guessing at timing and attempting to run even moderate boost is a bad idea, I've been building turbocharged race and performance engines for over 30 years and I've seen vastly different timing required and I've seen plenty of other people destroy engines in a couple minutes at the track because they don't understand things.
You probably have a better feel for what works on Saab engines due to your research, start there, tune at minimum possible boost and slowly work boost up listening for knock, keeping AFRs in the low 12s.
SDS timing is simple, run your rpm timing values generally like an atmo engine- about 10 degrees BTDC at 1000 rpm, working up about 3 degrees every 250 rpm increment until you reach max advance at around 2750-3000 rpm- usually around 25-35 degrees on most engines. 4 valve engine usually need less than 28 for max power. You can add advance under vacuum if you wish and start boost retard at 1-3 psi on most engines running pump gas. I have found as I said before, that trimming rpm timing approaching torque peak reduces knock considerably when working with low octane fuel. Generally on street engines, we never use less than 15 degrees total timing under boost as the EGT gets scary and the the engine simply lays down but your experiences may be different with the Saab.
I hope these general ideas are a bit helpful. I never hand out specific tuning information to people simply because I'm not there and if I tell you something that does not work out and you blow up your engine, I get blamed. Programmable systems require that the user verify AFRs and timing and keep these within the limitations of the engine.
Ross
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I will be taking his advice...
tuning with a wideband to keep my A/F in the low 12's should be no problem,
and I will start with base boost of 6-9 psi with the Compressor feeding the wastegate directly... using no boost controller at all at first...
setting timing the way he suggested and seeing what happens.
Eventually when I want to tune up the boost, I suppose i will just figure out where the engine will run the compressor most efficiently in the compressor map, and set the boost there...
AEM makes an interesting electronic wastegate controller, similar to the old APC system... and I may go to that, or just get a simple MBC and call it a day... setting my t3/t4 to run most efficiently at maybe 15 psi and have the timing more advanced than the stock saab ecu would run it...
the system has a knock sensor so, i'll put it to use and have it pull timing when knock is detected...
hopefully someday will post dyno results...
-gavin
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