John Appel

I am using a G4 storm on my twin cylinder motorcycle engine. We have a throttle body on each cylinder and so we are using throttle position and revs for the axes on for fuel and ignition tables. Currently we are using a cam sensor and so we have one fuel pulse per engine cycle. On our fuel table we have a master value of 20 msec and at idle the no. in the fuel table is 14 so that the pulse width at idle is 20msec x 14% which is 2.8 msec. I want to try running the engine without the cam sensor and so I will have 2 fuel pulses per engine cycle ie. one pulse every engine turn. I then plan to halve the master value to 10msec to compensate. This means the pulse width will be down to 1.4 msec at idle.I may have to adjust the no. in the table to something a little greater than 14 to allow for the greater injector offset at short pulse widths. Do you think that the system will give good repeatability at 1.4 msec PW. What would you consider to be the minimum PW that would still give reliable operation. Regards, John

Thanks for that Adam. My crank trigger is 24 - 2 so you are saying that it does not really matter where the cam tooth occurs. I have been told that the Link only needs the cam tooth on the first rotation of the camshaft at startup. Once the cam tooth has gone past the sensor once the engine is synchronised and will stay that way. In other words it does not have to reset itself for every engine cycle and even if you disconnected the sensor wire the engine would keep running. Is this correct.

I have a Link G4 Storm. I believe that the signal from the crank reference tooth and the cam sync tooth must not coincide. What would be the minimum separation required in crank degrees.What would be the result if they were too close.

If I remove the vacuum hose from the ports to the Link should I block up the pipe on the Link or leave it open. John

In G4+frmware New Features you list : Added single point every TDC injection mode to activate all injectors on every TDC for throttle body injection kits. Can you elaborate on this please. Is this for engines with a single throttle body but with an injector in every port . Is this a way to make the engine operate without a cam sensor. Is the injection still sequentially timed as opposed to batch fire when all injectors fire at once. If the injectors fire every turn instead of every second turn does the Link automatically halve the pulse width to compensate. Regards, John Appel

On our twin cylinder motorcycle engine we have two throttle bodies.Engine has equally spaced firing intervals. Because of ITB we are using TPS for the load axis on our fuel and ignition tables. The EFI tuning books say using MAP for load axis on ITB engines does not work because there is no plenum chamber to smooth out the vacuum pulses from each port. In our inlet ports we have tappings for vacuum pipes. Currently we have these plugged up. I have been told that even though we are using TPS we should still connect the two vacuum tappings to the Link G4 Storm using a Y junction and rubber hose. This would smooth the pulsations to some extent but not much. Can the Link make sense of such a highly fluctuating signal. Does it have some form of electronic smoothing circuitry to deal with this problem. How does the Link make use of this vacuum signal when I am using a miilisecond base fuel table and TPS for load. Any advice. Regards, John

Hi Brad In your reply you show the best sync tooth position for multi tooth crank trigger. Can you also show us the diagram for the multi tooth/missing teeth crank trigger as I am also interested in this matter.I can't find this on the help file. Regards, John Appel

I am using the Link G4 Storm on my parallel twin cylinder motorcycle engine. Engine is 1200cc with 360 degree crankshaft to give evenly spaced firing intervals. I have one throttle body per cylinder. I am currently using only revs and throttle position for inputs. I would think that at small throttle openings just off idle there would be a big change in air flow for a small increase in throttle angle so that throttle angle alone would not give a very accurate measure of airflow. Can I use input from a MAP sensor as well as TPS so that MAP would be the main measure of airflow at small throttle openings and TPS would be the main measure at high throttle openings. Can I simply plug in the vacuum hose coming from the Link to one inlet port. This would give a very pulsating vacuum signal. Should I cross connect the hose to both ports, this would even out the signal somewhat. Or should I use some form of electrical sensor. What is the usual arrangement on a 4 cylinder engine with separate throttle bodies on each cylinder. Regards, John Appel

Thanks for that . I will check with the timing light. One more question on the trigger tooth topic. I can see how the Link gets crank position every time a tooth passes the sensor but how does it get position in the space between the teeth. With a small tooth count of say 12 these spaces would be quite large. John

Hi Scott I am currently running with a synch tooth but I want to try it without the synch and use waste spark but I don't think this will make any difference. Because either way there will still be only one spark pulse per crank turn coming from the Link ( but the pulse will go to both coils at the same time ). The crank position is set back to zero after every turn so there will be no difference in the timing between the two cylinders. They spark at the same time. Where the error comes in is the 1/2 degree per tooth lost as rounding error. The actual trigger offset is 160 degrees calculated from the position of the trigger relative to the reference tooth at TDC. Between 7 and 8 teeth go by the sensor from the reference tooth to the spark point.( at full advance ). This would give an accumulated rounding error of 3 1/2 to 4 degrees. Could I compensate for this simply by adding the 4 degrees to the trigger offset value entered into the Link so I would enter 164 instead of 160. This means that there would be no more than 1/2 degree error over the full range of spark advance but this would not matter. John

Thank you Scott for that clarification. I have not heard it explained that way before. I understand it better now. On my engine if I have 30 degrees spark advance it takes between 7 and 8 teeth (after the reference tooth) to pass the sensor to reach the spark point. The rounding error per tooth will be 1/2 degree so the accumulated error would be about 3 1/2 degrees. My expected advance at full power will be about 30 degrees. What if I put a degree wheel on the crank and use a timing light and set the timing correct at 30 degrees by adjusting the trigger offset value entered into the Link.The normal advance range would be no more than one tooth (22.5 degrees) either side of the 30 degree figure so the error would be no more than 1/2 degree. A consequence would be that the trigger offset value entered into the Link would not match the exact geometric position of the sensor in the crankcase but that would not matter Do you think this would work or am I missing something. John

TO Davidv Have you tried the mixture test at lower RPM, say from idle up to 4000. Also have you tried doing this test at smaller throttle openings, say half throttle. Would you get the same best injector timing. John

Can you please expand on this topic of the no. of trigger teeth. Why is it necessary for the tooth count to be a whole no. factor of 360. The fact that we have 360 degrees to a circle is just a convention. In Germany they used to (and maybe still do) divide a circle into 400 divisions and called them grads.What is likely to happen if the tooth count does not divide into 360. What would you notice. On my parallel twin cylinder motorcycle engine I have 16-2 trigger teeth. The teeth are milled on one of the crankshaft webs. The gap is opposite the crankpins. This was done to give clearance for the piston skirt when the piston is right down. At the time I drew this up I was not aware of the need to have the tooth count divide into 360. Now 360 divided by 16 = 22.5 , not a whole no. but the engine seems to run OK. Could this be because the engine has evenly spaced firing intervals, that is once every turn. Maybe I was just lucky. Suppose the engine was a V twin with uneven firing intervals, what would happen. John

Thanks Scott and Adam, That's exactly what I was aiming for. Retaining the ability to adjust injection timing but without the cam sensor. The only downside I can see is the short injector pulsewidth at idle compared with sequential. Now to put it to the test. Regards, John

Thanks Scott for that last screen shot. My injector impedance is 12 ohms so current draw would be 1 amp each giving a total of 2 amps if we use single cylinder 2 stroke mode. This would be well within the limit of 5 amps. Can you do one more simulation. This time in 2 stroke twin cylinder with cranks at 360 degrees or 0 degrees. This would give me separate drivers for spark and fuel for each cylinder. This way if I want to do quick comparison tests between one or two injection pulses per cycle (that is with or without the cam sensor) I don't have to alter the wiring to the coils and injectors. I have previously found the best injector timing to be at 270 degrees before TDC so can you set it to the following figures Twin cyl. 2stroke Cranks at 360 or 0 degrees sequential injection at 270 degrees before TDC Zero spark advance 24 - 2 trigger 164 degree trigger offset If this proves to be OK I think it would be the best setup Thanks for all your help, John