Nitrous, retard timing by torque increase?
Nitrous, retard timing by torque increase? I am now pretty certain that tuning nitrous should be by the amount of torque increase and not horsepower increase. I believe someone verified that with me in an earlier thread, since a 150 shot of nitrous at 3500 rpms is going to increase the torque alot more than at 5500rpms.
My engine:
3500rpms 250hp/375lbs. if add 150 shot it increases to 400hp/600lbs
5500rpms 385hp/368lbs. if add 150 shot it increases to 535hp/515lbs
You can see a 150 shot increases torque(cylinder pressure) dramatically at lower rpms. So if I'm correct if I was to spray the nitrous at lower rpms I am going to need more timing pulled compared to higher rpms because there is a much higher torque(cylinder pressure) increase at lower rpms.
So if the recommended 1-2 degrees per 50 shot(50 horsepower) is not accurate, shouldn't I pull a certain amount of timing for the amount of torque increase instead? If so is there a recommened amount of timing to be pulled per certain amount of torque increase?
My engine:
3500rpms 250hp/375lbs. if add 150 shot it increases to 400hp/600lbs
5500rpms 385hp/368lbs. if add 150 shot it increases to 535hp/515lbs
You can see a 150 shot increases torque(cylinder pressure) dramatically at lower rpms. So if I'm correct if I was to spray the nitrous at lower rpms I am going to need more timing pulled compared to higher rpms because there is a much higher torque(cylinder pressure) increase at lower rpms.
So if the recommended 1-2 degrees per 50 shot(50 horsepower) is not accurate, shouldn't I pull a certain amount of timing for the amount of torque increase instead? If so is there a recommened amount of timing to be pulled per certain amount of torque increase?
You are entirely correct. Problem is the logistics in such fine control. So typically you pull timing for the biggest areas of Tq...and suffer a bit where you COULD have added some back.
What is so hard about pulling a couple more degrees in the torque band than you do in the power band?? The 2 per 50 is just a starting point rule, you should be tuning from plug readings...
When are you ever gonna be at 3500rpms while spraying? For a split second at the launch. You're thinking about this a little too deep. You pull too much timing then creep it back in based on the plug. Only way to correctly do it.
But, yes, he is overthinking it...
I was going to say the same thing about the launch... but then I looked at his signature, and saw he has a 6 speed... maybe one of these guys who sprays on the street. In which case, I would pull 2 more degrees in the torque band - I always set up street sprayers that way cause they spend more time in the 3-5k RPM range than a drag car flashing right through it on the convertor would...
But, yes, he is overthinking it...
But, yes, he is overthinking it...
I'm probably overthinking this too, but was hoping for some added assurance. I might do a progressive shot from 250 shot to 300 shot. But I have my rings gapped for only a 250 shot. Why would I not be ok? Reason I ask is below.
With a 250 shot at 5500 rpms I will be at 635HP/606Lbs. As I progress up to 300 shot at 6500rpms I will be at 700HP/566Lbs. So if torque is truly a direct relation with cylinder pressure, stress on parts, and somewhat heat. How would the 250 shot gapped rings not be ok with a progressive shot to 300 at 6500rpms if the torque has decreased from what it was at 5500rpms?
By the way I will have someone tune this if I do go this big of a shot but I'm curious about my rings. Thanks for all of your help.
Better to overthink than to underthink! 
I'm no expert on ring gaps - you would have to go to an engine builder on that. If you know what rings they are and what gap you are at, you may be able to talk to the ring manufacturer and find out more about what they will handle. I know what you are saying about staging the nitrous and bringing the last 50 later in the RPM range - I think you would be ok because the cylinder pressure has decreased a bit by then, but I would consult the experts...
I'm no expert on ring gaps - you would have to go to an engine builder on that. If you know what rings they are and what gap you are at, you may be able to talk to the ring manufacturer and find out more about what they will handle. I know what you are saying about staging the nitrous and bringing the last 50 later in the RPM range - I think you would be ok because the cylinder pressure has decreased a bit by then, but I would consult the experts...
