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Many others know MUCH more than I do, but while you wait for their help, please consider a fundamental question: How are you going to use the Dawes Device? There are two ways.
The way recommended in the instructions effectively ELIMINATES the APC and knock sensor (at least, on my C900 SPG... I'm not sure what vehicle you are driving). The "Dawes-default" installation probably works great (unless you blow the motor) but I and others fear driving at high boost without the antiknock protection circuitry.
There is another intriguing option which many feel is superior in Saabs. Briefly stated, this alternative "APC-friendly" install allows for a much quicker intitial boost rise while retaining the APC circuitry and knock protection at higher boost levels. It does this by hiding the initial boost rise from the APC until you hit a preset boost; once you hit this point, the pressure forces the valve open and the APC takes active control of boost parameters.
The reason why this works is that Saab designed the system with lots of safety features. One of them starts bleeding off boost almost as soon as it starts building, to avoid too-rapid boost spikes and sudden acceleration that would unnerve an unsuspecting driver and possibly put him/her into the ditch (at least). (Whether it's the APC or the BCV that does this initial bleeding, I'm not sure, but the install blocks the boost signal that triggers whichever device actually does the initial bleeding.)
On this or the classic 900 board, Beaudreau posted very detailed instructions a couple of years ago on installing the Dawes device in this fashion. I followed those instructions as one of the last steps in a lengthy mod process (all courtesy of the people on this BBS) and have had great results. You choose a boost level below which you are pretty sure you won't have knock even with cruddy gas (mine's set somewhere around 8 or 9 psi, no higher). The difference in my car was quite perceptible. The Stealthbomber spools up pretty quickly and she'll peg the boost gauge (23 psi).
Anyway, I sincerely recommend that you consider the possible adverse consequences of the default Dawes installation before proceeding. With Beaudreau's APC-friendly mod, there is no apparent downside and lots of upside. While you consider, search the performance and classic 900 boards and see if you can find his original posts on the topic. If not, repost a message to me and I'll try to find them. But, as I said, there are lots of people here on the board who have lots of good info, so balance and consider.
Good luck. And please forgive me if you knew this already and had made your choice.
Jim Watts
The Stealthbomber: 87 SPG, Modestly Modified
Modified APC, open K&N, sport exhaust,
24 lb injectors, 3.0 fpr, SPG9 AID, Dawes device
(inline to “C” port on BCV), poly motor mounts,
upgraded BPV, upgraded pads, stainless brake lines.
With visions of an upgraded turbo and mistletoe dancing in my head...
posted by 32.103.141...
, Tue, 9 Dec 2003 12:16:22
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