Racer189
November 1st, 2006, 22:11
Can anyone give me some feedback on how well the Electromotive XDI ignition works in a Severe Duty Endurance application. How well does the MSD crank trigger system work under the same application? I've been told that Electromotive works very well and can sometimes even increase hp? We are having problems with our MSD ignition.
FYI for Racers who run MSD ignitions. We run an MSD distributor and an MSD 7 box and have seen it retard up to 6 degrees over 5000 rpm. We tested the distributor on a distributor machine and it confirmed that it was advancing all by itself after 5000 rpm(FYI - our distributor was locked out). Our mechanic said that he had seen this before. We went and bought a brand new dual pick up MSD distributor and tested it on the distributor machine, it lost 5 degrees on one pick up and 4 degrees on the other. We were thinking/hoping that a crank trigger system may stop this but we've been told that isn't necessarily true.
The following are what we've been told on another forum
The term hysteresis is often used to discribe the effect. What this means is the circuit operation in one direction won't be the same going in the oppisite direction. In this case you see a distortion resulting in a curve instead of a linear function with time and rpm.
I have also saw it in simple magneto systems.
The cause is the parts and circuit inability to do the same function in respect to time interval where magnetics and rise time are involved.
Indeed a parts selection and testing can minimize this effect.
There are some engine combinations that can use some retard at high rpm, for various reasons but that gets into advance curve as opposed to the ignition it'self retarding as an unintended action..
Also:
at higher rpms you will see a retard condition even with a crank trigger. some of the newer digital msd boxes have a mag compensation circuit where an adjustment can be made to allow for the retard. it was explained to me that it was an inherent thing with manet triggered devices. the amount of retard is rpm dependant and gets worse the higher the rpm. the 7531 digital 7 box has a automatic mag-comp circuit and cannot be adjusted
This is why we are looking to switch ignition systems. This 6 degree retard condition was costing us 25 hp.
FYI for Racers who run MSD ignitions. We run an MSD distributor and an MSD 7 box and have seen it retard up to 6 degrees over 5000 rpm. We tested the distributor on a distributor machine and it confirmed that it was advancing all by itself after 5000 rpm(FYI - our distributor was locked out). Our mechanic said that he had seen this before. We went and bought a brand new dual pick up MSD distributor and tested it on the distributor machine, it lost 5 degrees on one pick up and 4 degrees on the other. We were thinking/hoping that a crank trigger system may stop this but we've been told that isn't necessarily true.
The following are what we've been told on another forum
The term hysteresis is often used to discribe the effect. What this means is the circuit operation in one direction won't be the same going in the oppisite direction. In this case you see a distortion resulting in a curve instead of a linear function with time and rpm.
I have also saw it in simple magneto systems.
The cause is the parts and circuit inability to do the same function in respect to time interval where magnetics and rise time are involved.
Indeed a parts selection and testing can minimize this effect.
There are some engine combinations that can use some retard at high rpm, for various reasons but that gets into advance curve as opposed to the ignition it'self retarding as an unintended action..
Also:
at higher rpms you will see a retard condition even with a crank trigger. some of the newer digital msd boxes have a mag compensation circuit where an adjustment can be made to allow for the retard. it was explained to me that it was an inherent thing with manet triggered devices. the amount of retard is rpm dependant and gets worse the higher the rpm. the 7531 digital 7 box has a automatic mag-comp circuit and cannot be adjusted
This is why we are looking to switch ignition systems. This 6 degree retard condition was costing us 25 hp.