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Old 12-04-2017, 08:25 PM   #1
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Swedish dynamics apc help

Hello I just installed the stage 4 apc and fuel injectors today and didn't notice any increase in boost... the only thing I didn't install was the fuel chip because people on the forums say that the chip causes problems and to leave the stock one in. Any ideas?
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Old 12-05-2017, 05:25 AM   #2
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I remember the good old days of turning pots and soldering APC's for more boost... and then T5 came along.

Have you checked your base boost and looked around for any vacuum leaks? Those two things should always be done right off.
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Old 12-05-2017, 01:01 PM   #3
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i would bet there are some pretty real intake leaks start by doing a boost check
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Old 12-05-2017, 04:41 PM   #4
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How much boost were you making before? Is the boost needle nice and steady under acceleration, or does it flutter, or spike up and then drop, or anything like that?

What timing advance settings are you running?

^^^ what they said, start with the basics. Also, do you have good (new-ish) plug & coil wires and the plugs gapped correctly? Cap and rotor in good shape? I've had old plug wires cause me all kinds of headaches trying to track down what was pulling my boost back.

Under increased boost the electrical resistance across the spark gap increases. This means that if there is a lower resistance leakage path (like between two wires, or between a wire and the nearby cam cover) the spark will arc there rather than going across the plug, and that cylinder won't fire until the cylinder pressure drops enough that the new point of lowest electrical resistance is across the spark gap again.

And that, ladies and gentlemen, is why we have coil-on-plug ignition systems.
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Old 12-09-2017, 08:47 AM   #5
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I sell chip upgrades and they do not cause problems. If you installed bigger injectors then you must use the chip. Their stage 4 APC has knock sensing turned down a bit, I don't think it is safe. Why their APC box is not giving you more boost? It could be that their APC core is defective and they never tested it on a car, or it could be that some component in your APC system is faulty.

Rule of thumb is that stock C900 can't boost much safely on 91 octane, timing would have to be more retarded but then you are boosting more but not making more power.

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Originally Posted by 1993saab900t16 View Post
Hello I just installed the stage 4 apc and fuel injectors today and didn't notice any increase in boost... the only thing I didn't install was the fuel chip because people on the forums say that the chip causes problems and to leave the stock one in. Any ideas?
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