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

Thanks for those images Scott.Hope you are not getting tired of me.Here is what I am aiming for. Ignition: A spark to both cylinders at the same time and every turn. Fuel: One half size squirt to both inlet ports at the same time and every turn, with the ability to time the injection. This way you get the full measure of fuel in a complete engine cycle.(2 turns). When you alter the timing both fuel pulses will shift together and always remain one turn apart. This setup requires no cam sensor because all events occur every turn. What if I was to call the engine a single cylinder two stroke. This injects and sparks every turn.For ignition I currently have two separate coils with their own built in igniters. What if I divide ignition 1 output into two and put one wire to each coil. They will then both spark every turn. I know this works because I have already tried this setup in 4 stroke mode. Can I similarly divide injector 1 output into two and put one wire to each injector. Would there be enough current. Can a single cylinder 2 stroke be put into sequential mode. If so then I would have injection timing adjustability. There may be another alternative. Rotax make a twin cylinder two stroke race engine. This has two crankshafts geared together for balance reasons. The pistons rise and fall together so there is zero crankpin offset. Both pistons fire at the same time so it sounds like a single. It is really two single cylinder engines doing everything together. Does the Link G4 Storm have provision for adjusting crankpin offset, or does it just assume that a twin cylinder two stroke would have crankpins at 180 degrees which is the normal arrangement. Can I call my engine a twin cylinder two stroke with zero crankpin offset and running in sequential mode I would then have a separate ignition output for each cylinder and a separate injector output for each cylinder. John

Thanks for your new graph Scott. That's getting closer to what I want. I have taken oscilloscope traces of the trigger pulses and they look nearly the same as yours. The ignition looks right (once per turn) Can you put the injection pulses for injector drives 1 and 4 to 1/2 engine cycle,(once per turn). I think the two will then be the same.I want to see where it injects relative to TDC ( the ignition point with zero spark advance). Can you then do another graph with a longer pulse width, say 10 msec. This will show me if it times by end of injection or start of injection. I understand what you mean when you say that the only way I can shift the injector timing in group fire mode is to shift the trigger wheel relative to the crank and then reset the trigger offset to compensate to bring the spark back to the right point. To Adamw My engine runs well in sequential mode. This requires the use of a cam sensor to tell the Link if piston 1 is at the top of the compression stroke or the top of the exhaust stroke. I have found that the transient throttle response does change when I change the injector timing. According to the help section on injector timing it is only possible to alter the timing if you are in sequential mode. I am looking for a way to make my engine run just as well without a cam sensor. The only way I can see of doing this is to run in group fire mode,( sparking and injecting every turn instead of every second turn). This way the Link does not need to know what TDC the piston is on and so the cam sensor is not necessary. It may turn out that the engine will not run as well as it does in sequential mode but the Triumph Bonneville engine is a 360 degree parallel twin same as mine and it has no cam sensor. It uses a single twin lead coil for ignition and so it must spark every turn (waste spark system) I can only assume that the injection also fires once per turn. I have ridden this bike and it has nice smooth throttle response. John

Thanks for that Scott.It would appear that the injection occurs at the time of the tooth gap because when you shift the offset only the ignition point seems to change. I assume that the pink line that you call cyl 2 is actually cyl 2 of a 4cyl engine because it is displaced by half a revolution from cyl 1. My second cylinder would be the same as cyl 4 on a 4 cylinder engine which would be one whole turn displaced. Ignition will be by waste spark so will be the same for both my cylinders. My trigger offset is 164 degrees. Can you show me another graph with the following figures Trigger offset 164 degrees Toothed wheel 24 - 3 ( this will give the same angular gap as my 16 - 2) Pulse width 2 msec ( which is about what I expect at idle) Ignition timing zero degrees. (this will show me where TDC is) Can you show cylinders ! and 4 of a 4cyl engine. (they should be the same) Does it time by end of injection or start of injection ( this will tell me in which direction the pulse width will increase at higher throttle openings) My aim is draw a chart showing injection pulse relative to valve movement. Thanks for your help , Regards, John

Hi Scott Crank trigger is 16 teeth with 2 teeth missing so there are actually 14 teeth present. Inductive sensor from a Harley Davidson John

I have a Link G4 Storm. I am using it on a 1200cc twin cylinder 4 stroke motorcycle engine of our own construction.This engine has evenly spaced firing intervals (360 degrees apart) which is commonly called an opposite pair. It is like No.1 and No. 4 cylinders of an inlne 4 cylinder engine. So far we have been running it with sequential injection using a cam sensor. We have experimented with injection timing. I have been judging the results by comparing the response to blipping the throttle off the idle. I have found the best pick up from a closed throttle to be at about 270 degrees BTDC for end of injection timing. This is when the piston is about halfway down the induction stroke and so the air stream thru the port would be getting close to its maximum velocity. It seems to like injection into the moving airstream rather than injecting into static air with the valve closed. I have read different and conflicting opinions about this. I would like to try running the engine without the cam sensor.(It gets in the way) This would mean running in multi point group mode. With this set up it would squirt twice in a 720 degree engine cycle, in other words once every crank turn. In your section on injector timing it says that it is only possible to vary the timing in sequential mode. When using two squirts per engine cycle is it possible to set the second squirt at the same 270 degree figure I am currently using and then the first squirt would necessarily be one turn prior (630 degrees BTDC). This way the first pulse would go into the port full of static air (valve closed) and the second pulse would go into the moving airstream with the valve almost fully open.With a 360 degree twin the timing would be identical on both cylinders. If it is not possible to vary the timing in multi point group mode how does the Link set the timing. Is there a default timing that it reverts to. Regards, John

We are now at the stage of testing our 1200cc twin cylinder motorcycle engine. We have the use of a computer controlled load bearing dyno, chain driven from the gearbox sprocket. At this point we have achieved a reasonably good fuel map.We are using a single spark advance curve set for full throttle at this early stage of tuning. Spark advance is at 32 degrees from 3500rpm upward. As a next step we are thinking of using just three advance curves for different throttle settings. Can anyone suggest suitable throttle setting points to choose. I had in mind about 10% and 30% and 100% but I have no previous experience of this and so would welcome any suggestions. Also how much extra advance should I use at the lower throttle settings.Does anyone have a spark map for a similar engine. Details are 600cc per cylinder, 4 valves per cylinder, compression ratio 9.5 to 1, air cooled. A BMW boxer would be a good example. Regards, John

I am test running my motorcycle engine on a dyno. I am using Link G4 storm for ignition and fuel. We have a car battery to supply current running total loss. We charge the battery when the engine is not running. If we leave the charger connected while the engine is running could this damage the Link.

I have a Link G4 Storm on a twin cylinder motorcycle engine. I want to fit a tacho driven by the tacho function . What is the difference between a high level and a low level tacho. I am looking at a Prosport 80mm tacho which has a stepper motor movement. The model I am looking at comes in either a petrol or diesel application. The petrol one goes up to 10,000 rpm and the diesel one goes up to 8,000 rpm. The two look identical apart from speed range. I prefer the diesel one because of the lower full scale reading. I have copies of the data sheets for both these tachos and the wiring terminals on both are the same. The input is marked "connector for sensor wire". For the petrol model it is shown going to the ECU. For the diesel model it is shown going to the alternator. Would the Link ECU drive the diesel model. Any ideas anyone. Regards, John

 Thanks for that Adam. As I understand it all timing comes from the crankshaft teeth and in particular the reference tooth which is the first one after the gap.When you fill in the details on the cam sensor it asks whether it is inductive type or Hall effect but it does not ask for a degree position of the sensor relative to TDC.  With an even firing 360 degree twin there is one ignition pulse and one injection pulse every turn of the crank. The purpose of the cam sensor is only to direct the pulse to the right cylinder and the left cylinder alternately. when we first tried to start our engine running sequential and using the cam sensor it would not start. We then swapped over the plug leads and injection wires and it started immediately.  Simon says that it only needs the sync pulse on start up. As soon as the engine starts it does not need the sync pulse any more. I think that if I used a pulse from a MAP sensor on one port it also would not matter exactly when the pulse occurred.  As you say the exact timing of this pulse may vary slightly and may cross over one of the crank teeth. My feeling is that it would not matter as long as it does not cross from one side of the reference tooth to the other side.  If it did cross the reference tooth I think that the degree timing figure would be the same but everything would be displaced one turn and in effect the right cylinder would become the left and vice versa.  I have looked at the Modern Triumph Bonneville twin and there is no cam sensor. One of the wires going to the injectors has a tag on it labeled Cyl one. This would indicate that the engine is running sequential because if it was batch fire it would not matter if you swapped the injector wires. The ignition is waste spark using one twin lead coil and so this cannot go wrong. The only way I can think of how to differentiate one cylinder from the other is from a MAP pulse.  The W800 Kawasaki is also a 360 twin and does not have a cam sensor. Does anyone have any further detailed information on how they do this.

I am using a Link G4 storm on a twin cylinder motorcycle engine of our own construction. It is a parallel twin with 360 degree crankshaft and therefore has equally spaced firing intervals. I am running sequential injection using a Hall effect sensor on the overhead exhaust camshaft. I believe these sensors can be sensitive to heat and can fail. If the sensor were to fail and give no signal at all can the Link be set so that it reverts to batch fire and injects and sparks every revolution . The engine would probably run just as well under normal operating conditions but maybe would not idle so well due to the very short pulse width when using the batch fire system. Â John