LS1 Boost OS - Development

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bubba2533
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Re: LS1 Boost OS - Development

Post by bubba2533 »

The current code simply cuts spark above the rev limiter rpm that is set in the tune. I wasn't really planning on this application when creating this code. I would guess that the code is performing just fine, but I would have to see your tune file to make sure it's patched correctly.

In my opinion this application is an extremely severe application at fairly high RPM at WOT for extended periods of time and I put this in place as a simple safety. The engine is accelerating quickly all the way to the limiter rpm since there is little load holding the engine back. So there is likely a significant amount of overshoot, where none of the cylinders are firing yet still getting fuel injected. If this happens for long enough I imagine the cylinders get flooded and will no longer fire.

I think there are a few ways to try and fix this:
  1. Remove timing in the tune right below the spark cut limiter to reduce torque (aka. acceleration) of the engine to lower the amount of overshoot. This is the easiest thing to test and see if it improves the situation.
  2. Program a timing adder to the code to do the same thing as above. There are likely many ways to implement something like this, but one I can thing of would have the user enter a timing modifier amount (eg. -5 Degrees) and an engine rpm before the limiter (eg. 100 rpm) to start applying that timing modifier. This would be possible, but still require a significant amount of work.
  3. Program a PID function to the spark cut to try and limit the amount of time all cylinders are being cut. I would also try to rotate through the cylinders being cut to try and limit the same cylinders being cut in a row for many times. This could still cause the same problem if most of the cylinders are being cut to hold the desired rpm. This would be quite complex and I'm not confident I could even do it.
  4. Program both option 2 & 3 to have a smoother cut and still be able to reduce torque. Obviously the most complex to implement, but also it would likely be the best working solution.
  5. Program some sort of staged injector cut to reduce the engine torque. I'm not a big fan of this as there will still be a small amount of fuel that would cause a lean burn
I would recommend trying option 1 because even if I wanted to code up one of the other solutions it would likely take me a while as this is purely done in my spare time.

I actually started a thread a while ago about trying to make Launch Control smoother, but it could also be applied to the Engine Speed Limiter. It wasn't a priority to fix at the time because it was working for me fine as is. Creating a Smoother Launch Control
LS1 Boost OS V3 Here. For feature suggestions post in here Development Thread. Support future development ->Patreon.
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antus
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Re: LS1 Boost OS - Development

Post by antus »

With the spark cut cylinders wont get flooded, the unburnt fuel will go in to the exhaust and you'll get huge backfires. Unless your doing it for show you generally want fuel cut.
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bubba2533
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Re: LS1 Boost OS - Development

Post by bubba2533 »

Yes, some of the fuel will go out the exhaust, but some will also likely coat the spark plug. I'm not saying it's a sure thing, but I think it's a reasonable theory based on the video. It sounds like it attempted to fire as the rpm was falling. Then it was re-started after the engine died and it was missing on some cylinders. To me that sounded like it had fouled spark plugs from unburnt fuel (flooded), but I don't really know.

If the code is working just fine, then I'm not sure what else could be causing it. Have any theories?
LS1 Boost OS V3 Here. For feature suggestions post in here Development Thread. Support future development ->Patreon.
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hsv08
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Re: LS1 Boost OS - Development

Post by hsv08 »

bubba2533 wrote:The current code simply cuts spark above the rev limiter rpm that is set in the tune. I wasn't really planning on this application when creating this code. I would guess that the code is performing just fine, but I would have to see your tune file to make sure it's patched correctly.

In my opinion this application is an extremely severe application at fairly high RPM at WOT for extended periods of time and I put this in place as a simple safety. The engine is accelerating quickly all the way to the limiter rpm since there is little load holding the engine back. So there is likely a significant amount of overshoot, where none of the cylinders are firing yet still getting fuel injected. If this happens for long enough I imagine the cylinders get flooded and will no longer fire.

I think there are a few ways to try and fix this:
  1. Remove timing in the tune right below the spark cut limiter to reduce torque (aka. acceleration) of the engine to lower the amount of overshoot. This is the easiest thing to test and see if it improves the situation.
  2. Program a timing adder to the code to do the same thing as above. There are likely many ways to implement something like this, but one I can thing of would have the user enter a timing modifier amount (eg. -5 Degrees) and an engine rpm before the limiter (eg. 100 rpm) to start applying that timing modifier. This would be possible, but still require a significant amount of work.
  3. Program a PID function to the spark cut to try and limit the amount of time all cylinders are being cut. I would also try to rotate through the cylinders being cut to try and limit the same cylinders being cut in a row for many times. This could still cause the same problem if most of the cylinders are being cut to hold the desired rpm. This would be quite complex and I'm not confident I could even do it.
  4. Program both option 2 & 3 to have a smoother cut and still be able to reduce torque. Obviously the most complex to implement, but also it would likely be the best working solution.
  5. Program some sort of staged injector cut to reduce the engine torque. I'm not a big fan of this as there will still be a small amount of fuel that would cause a lean burn
I would recommend trying option 1 because even if I wanted to code up one of the other solutions it would likely take me a while as this is purely done in my spare time.

I actually started a thread a while ago about trying to make Launch Control smoother, but it could also be applied to the Engine Speed Limiter. It wasn't a priority to fix at the time because it was working for me fine as is. Creating a Smoother Launch Control
Thanks Bubba, Ill give those things a try. Just with how it acts I don't think it will change the fact it completely cuts the ignition completely when it happens but I will test the theory.
We have toyed with the likes of the MSD spark cut systems, and while they work fantastic and the exact same way by cutting all spark until the rpm drops below set speed then reenabling the system, its not a factory setup run by the factory ecu which is why your OS is an attractive option.
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hsv08
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Re: LS1 Boost OS - Development

Post by hsv08 »

antus wrote:With the spark cut cylinders wont get flooded, the unburnt fuel will go in to the exhaust and you'll get huge backfires. Unless your doing it for show you generally want fuel cut.
Fuel cut does work great as a factory option, and does the trick, but we want that difference, the ability to have flames out the exhaust, the stuff the crowds and judges get up on and that edge to help get those few extra points above the others. Lets face it, The sport (if you can call it that) is all about the crowd, it does nothing good to the cars or engines, but people still love it.
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hsv08
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Re: LS1 Boost OS - Development

Post by hsv08 »

bubba2533 wrote:Yes, some of the fuel will go out the exhaust, but some will also likely coat the spark plug. I'm not saying it's a sure thing, but I think it's a reasonable theory based on the video. It sounds like it attempted to fire as the rpm was falling. Then it was re-started after the engine died and it was missing on some cylinders. To me that sounded like it had fouled spark plugs from unburnt fuel (flooded), but I don't really know.

If the code is working just fine, then I'm not sure what else could be causing it. Have any theories?
What i will try to do ( and it wont be to healthy) is try lean it out up top, to reduce the chance of plugs fouling from unburnt fuel. ill just set my PE to 13.5 at 6k to test.
But we have also had troubles of it initiating one cut just prior to limiter but on the way up to it ( about 5.5k ) then dyeing out almost like you've shut the ignition off. Kill the ignition and restart engine before rpms fall to zero and starts up to life straight away as if nothing happened.

Will test a few theories this weekend and see if i can get a definitive "condition" Where it happens more often then not.
Highlander
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Re: LS1 Boost OS - Development

Post by Highlander »

Flames out the exhaust will wash your cylinder bores. Very bad idea. Only reason to do spark cut is when you have suplemental and unmetered fueling that could still cause combustion to occur because you are not removing all the fuel going into the cylinder.
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hsv08
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Re: LS1 Boost OS - Development

Post by hsv08 »

Highlander wrote:Flames out the exhaust will wash your cylinder bores. Very bad idea. Only reason to do spark cut is when you have suplemental and unmetered fueling that could still cause combustion to occur because you are not removing all the fuel going into the cylinder.
We are not talking about methanol her or E85. The quantities of fuel are not huge. We have run spark cut systems on many vehicles before without an issue. Instead of using the MSD system we just want to use the factory system. Which will do the job just fine when we figure out what's going on.
Antilag systems work the exact same was to a certain degree. Driftcars we've tuned with links etc all run spark cut. They are on the limiters just as often. Your not going to bore wash an LS and do any damage with a simple spark cut limiter system.
bubba2533
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Re: LS1 Boost OS - Development

Post by bubba2533 »

Thinking about new features for the next version of the custom OS, so if you have ideas comment on my Patreon post Linked Here.
LS1 Boost OS V3 Here. For feature suggestions post in here Development Thread. Support future development ->Patreon.
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Phoenix
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Re: LS1 Boost OS - Development

Post by Phoenix »

Just something that a little different. A way for the 7603 to use a Gen 4 DBW throttle body?
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