Base advance for the NS

The bit everyone hates, electrical problems. Hope you find your fix here. Posting restricted to registered users.
Post Reply
Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Base advance for the NS

Post by Luciano »

Hi All.
Do someone know what "base advance" the ns400 has?

I have a IgniTech ignition module that is set to default 10 degree. But is this a accurate number?
Have anyone spotted any difference in degree between pick-up 1 and pick-up 2?

Base advance = cylinder 1 at TDC we need to also establish accurately the “base timing” of the trigger in relation to the lobe's trailing edge. At TDC the lobe will have travelled a certain number of degrees past the trigger, and the angle formed from the crank axis thru the trigger pole center and the trailing edge of the lobe tells the ECU where the timing event is in relation to piston position.
Source and More details here:
http://twostrokeshop.com/ignitech.htm
Best regards, Luciano
Torque over the whole register.

Channel Hopper
Posts: 1329
Joined: Thu Sep 23, 2004 5:26 pm

Re: Base advance for the NS

Post by Channel Hopper »

The NS400 ignition is static wrt the pulse coils and flywheel. Firing on both cylinders is set to 21 degrees before TDC.

Ignition advance is 0-14 degrees depending on engine speed so maximum advance is 7 degrees before TDC.


I'm a little rusty, as I dealt with ignition system design before I went to college (early 80's) but the pulse coil sends a(n almost) square pulse, the ramp being at around 0.2 mS after the flywheel notch passes the coil, and the black box(es) take this delay into account when turning the pulse into a spike to the ignition coils. Again, there is a delay of about 0.2/0.3mS in the charging of the ignition coils, but again this is compensated for in the advance curve.

Everything else in the transfer of data from the pulse coil occurs much faster, at about a thirtieth of the speed of light, so can be ignored. Since you are retaining pulse coils there is no need to mention hall-effect /optocoupling engine sensors that have a much better square wave output, and also work at near light speed transfer.

In slightly more modern units to the early 80's systems, the advance system also includes energy sensor variables, which detects differences in the pulse coil pulse voltage, and so compensate for low battery voltage, wear and tear in the engine bearing nearest the alternator (which can show up as flywheel to pulse coil irregularity).
Other forum posters have had success using Suzuki electronics on the NS400, which may include a couple of these within the mapped ignition curve. Certainly a newer system if set up correctly is likely to offer a better reliability, as components of old black box designs, and the wiring looms they are fitted to still rely on the spade connections between them, which often miss pulses due to vehicle/engine vibration. They are also inherently prone to outside interference, especially as older bike looms are not grounded/earthed at points for the best positions for the electronics to do their job.

The last ignition mappings I worked on had curve variables to compensate for engine (oil) temperature, the mileage of the vehicle, and time after the last service intervals, but modern injection systems combine much of this into the fuel delivery. Modern systems also work with the gear selection/vehicle speed to compensate for air box pressurising or 'ram-air' effect, and sometimes driver/riding characteristics.


What has always surprised me, is the need to include two (or more) flywheel sensors on electronic ignition for multi-cylinder, as the fixed mechanics of the engine dictate the exact distances between the required firing pulses. The need to provide the second or third spark in engine rotation could be provided by a timed counter and multiplier in the electronics. Additionally the flywheel was never the optimum position for accurate ignition on a two stroke engine, but that's another story.

Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Base advance for the NS

Post by Luciano »

Hi.
Now i have found the "base advance" it is 16 degree on the NS 400.
You do not have the required permissions to view the files attached to this post.
Torque over the whole register.

Post Reply