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Two hard timing questions

Posted by bcjjones, Nov 4, 2013

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  1. bcjjones

    bcjjones Proven Member

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    I have two timing questions

    Firsy one is, isn't it possible to have timing 180 out? Not 180 out like the dow pins are at 12 oclock and the notch on the dampner is opposite of the T on the timing cover. I mean the number one cylinder is at TDC on the exhaust stroke instead of the compression stroke? All the valves are closed at TDC on the exhaust stroke just like the compression stroke correct? And if this is possible, will the car still start at all?

    Now for my "second" question. I have a 91 gvr4. I am runnimg an evo 8 ecu. The firing order is completely opposite of a stock 1g ignition timing. So again leads back to my first question. If in fact it is possible to set mechanical timing 180 off, and I do in fact set the timing CORRECTLY FOR A STOCK 1G ECU it wouldn't be correct for the evo 8 ecu that has the opposite firing order? So I would need to set the mechanical timing with the number four cylinder at TDC on the compression stroke instead of number one?
     
  2. boost97gst

    boost97gst Proven Member

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    Ill let someone with more knowledge help, but is there any chance someone installed the cams either A: 180 out(dont know if thats even possible) or B: Installed the cams swapped. As in, intake and exhaust cams being swapped LOL. Sounds crazy but ive heard of it.
     
  3. delta448

    delta448 DSM Wiseman

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    Turbo DSMs have a waste spark ignition from the factory, meaning a single coil fires two cylinders at the same time. One cylinder is on compression while the other is "wasted" on a cylinder that is on it's exhaust stroke. On a 4G63, cylinders 1 and 4 are on coil A and cylinders 2 and 3 are on coil B.

    The spark voltage in this type of system is generated between the two poles of the coil and the current actually crosses through both plug gaps to reach the other pole on the coil. The energy that gets used by the cylinder on it's exhaust stroke is always much less than the energy needed for the cylinder with a compressed and dense air-fuel charge between the strap and center electrode, no matter which of the two cylinders is on compression.

    If you run your copper plugs long enough without changing them, you will see the erosion on paired plugs will be complementary, where one plug on the coil erodes the strap and the other plug on that same coil erodes the center electrode, -this occurs because of their coil polarity and the direction that current always flows through those 2 paired plugs.

    Nope. There is valve overlap occurring unless you've jumped timing or screwed up your t-belt install. The exhaust valves are always going to be approaching closed at the same time the intake valves are beginning to open.

    Sure will.

    The firing order for all 4G63s is 1-3-4-2, with cylinder 1 always being closest to the timing belt. The only thing to screw up is which coil is firing which two plugs.

    Nope. Mechanical timing does not need to change.
     

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  4. steve

    steve DSM Wiseman

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    Remember that the cams run at half the speed that the crank does, so 360* at the crank is 180* at the cams.

    The crankshaft puts pistons 1 and 4 at TDC when the timing mark is aligned with the cover mark and 2 and 3 are at BDC. The difference between 1 and 4 is due to the cams. When the dowels are up cylinder 1 is at TDC Compression and cylinder 4 is at TDC Exhaust. When the cam dowels are down, 1 is TDC exhaust and 4 is TDC Compression.

    As mentioned the valves are closed at TDC Compression but not at TDC Exhaust. The exhaust valve remains open past TDC on the exhaust/intake stroke transition when the intake valve opens. (overlap)

    As Delta448 points out the DSM ignition fires twice in each cylinder once in the compression stroke and once in the exhaust stroke so even if you have the CAS installed 180 out the car will run.
     

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  5. bcjjones

    bcjjones Proven Member

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    But the injector only fires on TDC for the compression stroke correct? It does not fire on the exhaust stroke. So I would still need to find TDC on the compression stroke?

    So correct me if I'm wrong again, but the evo 8 ecu is going to fire the number four injector as the number one injector. So if I time it as if I was using a stock ecu and use the number one cylinder to do so...wouldmt the evo 8 ecu be firing the injector on the number four cylinder instead of the number one?
     
  6. delta448

    delta448 DSM Wiseman

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    The Evo ECU still calls cylinder 1, cylinder 1. Match the pinouts up and wire injector 1 on your car to the Evo ECU's pin for injector 1.

    The Evo uses the same firing order as any turbo DSM and actually has the same CAS sensor as a 97+ turbo 2G. 1G and 97+ CAS sensors output the same signal pattern for the injectors, the 1G CAS just adds a second reluctor pattern for the ignition signal. The only oddball is the 95-96 DSM CAS, which outputs an inverted signal pattern compared to all other years.

    I don't understand why this has you so confused.

    It's basically the same engine, just because it's mounted on the opposite side of the bay doesn't make the ECU outputs reversed.
     

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  7. steve

    steve DSM Wiseman

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    Depending on how much fuel is required and the change in throttle position the injectors can fire the whole cycle. In sequential mode the injector is fired at the intake valves starting at 5* before the beginning of the exhaust stroke. In simultaneous mode all the injectors are fired at the same time starting at 5* BTDC of each cylinder.

    What do you mean "find" TDC on the compression stroke.

    Where did you get the idea that the EVO VIII has a different firing order?
    delta448 addressed in his post.

    "The firing order for all 4G63s is 1-3-4-2, with cylinder 1 always being closest to the timing belt."
     

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  8. Tyeler18

    Tyeler18 Proven Member

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    Seeing as how I'm running an evo 8 ecu in both my galant and my 1g- if you followed the wiring diagram posted use the DSM firing order. The injectors are wired up just like stock, so you're not changing anything.
     

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  9. s14boy

    s14boy Proven Member

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    it makes no difference to do any re wiring at all. even if cylinder 1 is now cylinder 4 they are each at the same position at the same time so it will do nothing to swap them.

    -Mike
     
  10. bcjjones

    bcjjones Proven Member

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    Well I guess what confused me was, now that I did a little more reading, is the 4g63 has a batch type injection/ignition system as opposed to a sequential type system.

    I believe this is why I was so confused. I was thinking the injector only fired one time per crankshaft revolution, on the intake stroke of the cylinder. The injector in fact fires on both the intake and exhaust stroke correct?
     
  11. steve

    steve DSM Wiseman

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    I don't know what you were reading.

    The DSM ECU supports sequential and batch (simultaneous) modes depending on what is required.

    When your cruising along the ECU is firing the injectors in sequential mode starting at 5* BTDC of the cylinder exhaust stroke and holds the injector open until the required IPW is met. It starts at the exhaust stroke to cool the intake valves and vaporize the fuel so when the intake valves open the fuel is atomized. If the IPW is short and the RPMs low the injector may stop before the intake valve opens. If the IPW requested is long and the RPMs high the injector may never close (IDC =>100%)

    Normal and hot starts are a little confusing at the beginning so the ECU fires all the injectors in batch mode until it figures out where cyl 1 is and then switches to sequential.

    Cold starts require more fuel so the ECU stays in batch mode longer.

    Acceleration enrichment causes additional injector firings.

    You can read about how it works in the 1G technical manual.
     

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  12. DSM1G90

    DSM1G90 Proven Member

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    I like to ask a question on this topic: I was experiencing hard and no starts after hot and it was recommended to me to change out my temp sensor since I was having occasional CEL light display with the code pointing to the temp sensor.

    Changed out the temp sensor and all systems returned to a normal closed loop condition.

    What happened here - how did the faulty temp sensor caused a short or open in the system to prevent either forms of ignition procedures to fail?

    thx - DSM
     

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  13. delta448

    delta448 DSM Wiseman

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    It caused mis-fueling.

    A hot re-start requires additional fuel, since a hot intake port wall will evaporate all of the normal fuel film puddle that is present while the engine is running. When a hot-restart is needed on a 2G, the FPR solenoid cuts off the vacuum to the FPR, thereby increasing fuel pressure at the rail. I think the 1G system is the same, but I won't guess. I'd also imagine this system is active in cooperation with a fatter injection routine that decays over time. The cold start routine is also based on temp and is fat so that it can ensure there is enough fuel to ignite, since gas tends to want to not vaporize but fall out of suspension when at a really low temp.
     

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