Making DIY ignition cut / REV limiter?

[forcefed86]

Instead of cutting fuel like the OEM ECU does, I’d like to actually cut the ignition/spark.

I have an antilag system setup that drops timing to -10 deg when the VSS is less than 1mph and the rpms are above 4K. I’d like to limit the RPM (stutter box) with an ignition cut instead of a fuel cut. This way I can pump fuel into my anti-lag setup instead of cutting fuel.

I had planned to use a SPDT relay, an adjustable RPM switch, and the VSS sensor.

Using these items I would cut the ground to the coils if the rpm went above 4500 and the VSS was less than 1 mph. This should pulse the ground signal going to the coils allowing me to go WOT when the anti-lag is active.

I’m concerned that dropping the ground may set off engine codes? Or the relay may not be fast enough. Anyone know of a “fast-acting” 12v SPDT relay?

Any help appreciated.

 

[Kyle_T]

If you want ignition cut you could just get the Bee*R power builder.

 

[forcefed86]

If you want ignition cut you could just get the Bee*R power builder.

I think I'd rather try it myself.

thanks though!

 

[polarmoment]

The problem is that if you cut off the power to the coils while they're charging, you get a spark.

You need a method that waits for the charge period to end, for the spark to occur and then kills the next charge event. The method you're proposing could cause serious detonation.

 

[forcefed86]

The problem is that if you cut off the power to the coils while they're charging, you get a spark.

You need a method that waits for the charge period to end, for the spark to occur and then kills the next charge event. The method you're proposing could cause serious detonation.

I hear what your saying... But we're talking about milliseconds here. When I pull the power to the coil and it fires why would this be a problem? Even a fast cycling relay only cycles at 1.5 times a second.

Would firing at low load situations really cause major detonation issues? Esp. since I'll have the ignition firing at -10 degrees at this time? I can't see an ignition event fired off a MS off causing major detonation?

Maybe I'm just not seeing it...

Thanks for the input!

 

[Arthris]

the only thing fast enought to interup the charge would be a transistor. Not a relay. If you interup the the ECU side its a low current signal. But you have the issue that polarmoment has stated. you would need to cut the charge side of the signal the right time to prevent the coil premature discharging and cause catastrophic failure. Only way I could see doing this would be a piggy back of some sort. Such as a Mega Squirt.

 

[Blurred Talon]

I think I'd rather spend the $15 on a relay and do it my self. Than spend $350+ on someone elses relay in a fancy box.

thanks though!

These fancy boxes are not relays but rather more complex digital electronics like microcontrollers. A relay is analog and it cannot react fast enough.

If you want cheaper then I suggest looking at the N2MB WOT Box. I had one before I changed to ECMLink.

 

[silvreclips]

I dont believe that building a system like you are describing will give you the results you desire. If you look into how antilag/studder boxes are configured you will see that they are not just cutting off spark to the coils to limit the rpms. They are set up to cut x sparks out of y events. So they are not cutting all spark off but only removing enough to keep the engine from accelerating past the limit you want.

 

[92mitsubishi]

I don't see this ending well for you detonation is a very bad thing. Im no techy guy but if you cut the spark it will still put fuel in the cylinders. So the next time it fires there would be to much fuel in the cylinders. I could be wrong but I would rather spend the money on an already made up system to know my engine will be safe.

 

[silvreclips]

I don't see this ending well for you detonation is a very bad thing. Im no techy guy but if you cut the spark it will still put fuel in the cylinders. So the next time it fires there would be to much fuel in the cylinders. I could be wrong but I would rather spend the money on an already made up system to know my engine will be safe.

If fuel enters the cylinders but does not ignite it was exit when the exhaust valve opens. Now you have an exhaust manifold full of fuel which will ignite from the other cylinders and create a lot of energy in the exhaust manifold to go through the turbo causing it to spool up. This is how antilag works. This can be bad because of all the heat generated in the exhaust manifold and in the turbo which can lead to melting the tips off the turbine wheel if your not careful.

 

[92mitsubishi]

If fuel enters the cylinders but does not ignite it was exit when the exhaust valve opens. Now you have an exhaust manifold full of fuel which will ignite from the other cylinders and create a lot of energy in the exhaust manifold to go through the turbo causing it to spool up. This is how antilag works. This can be bad because of all the heat generated in the exhaust manifold and in the turbo which can lead to melting the tips off the turbine wheel if your not careful.

that makes sense thanks for clearing that up. thats good info i dont own a turbo so the do's and donts are still unclear to me but im learning.