383 with spray
#1
383 with spray
Alright so I just finished reading all the threads concerning Tony's 383 build that he stuck in his c-5. First of all WOW, that engine cranks. I was wonder how an engine like that would respond to nitrous. I know I know just another example of american greed, but i want more. . . and I want it now.
#2
It would be fine with nitrous if he had the right pistons in it. Had a cam speced for it, made sure the tune is dead on and then and the juiced it up.
A forged short block with the right pistons will support a lot. 4" stroke Wiseco pistons Hell fire rings and spray away!
If your looking for a build we can certainly help you out, we build n2o engines for big amounts of juice all the time from a 100 shot to how ever much you want to spray. 400 shot dual stage?
A forged short block with the right pistons will support a lot. 4" stroke Wiseco pistons Hell fire rings and spray away!
If your looking for a build we can certainly help you out, we build n2o engines for big amounts of juice all the time from a 100 shot to how ever much you want to spray. 400 shot dual stage?
#3
11 Second Club
Joined: Jun 2005
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From: Was New Orleans, but swam to Baton Rouge
Alright so I just finished reading all the threads concerning Tony's 383 build that he stuck in his c-5. First of all WOW, that engine cranks. I was wonder how an engine like that would respond to nitrous. I know I know just another example of american greed, but i want more. . . and I want it now.
#4
What is a nitrous cam? Bigger on the intake duration than exhaust, big LSA? lots of lift, what is the difference from a N20 cam and say just a normal Forced induction, big NA cam?
#5
Here is a quotation from someone (non sponsor cant post link)discussing this:
A cam optimized for nitrous (N) is quite different than a cam optimized for NA use. It will make a lot more power while on N, on the order of 10-15% of the nitrous boost, but lose quite a bit compared to an optimized NA cam off the juice. I want to take a minute to explain a little about this and offer suggestions about compromises that will work pretty well with either.
Using N poses a problem. An optimum head for nitrous use would have a larger exhaust valve at the expense of a smaller intake valve. When you add N, you are drastically increasing the volume of exhaust gasses needing to be pumped out. If you add a 150hp shot on to a 300hp motor, 50% more exhaust gas is created, for example. Not only due the pumping losses go up dramatically, there is more residual gas and contamination of the intake charge to deal with. The exhaust valve area would need to be 50% larger to fully compensate.
Not only is 50% more exhaust valve area completely impractical, it would severely compromise NA power. So, the cam must be used to compensate. The method of compensation is to open the exhaust valve earlier. As a rule of thumb, the range to look for is 10-20 degrees earlier with 150-300hp of nitrous. There are a couple of ways to open the exhaust earlier. We can increase the LSA, increase the exhaust duration, or advance the cam. As with all aspects of cam design, there are always tradeoffs. Increasing the exhaust duration will also increase overlap when typical cam profiles are used. If we had exhaust lobes specifically designed for nitrous available, which most of us do not, just the opening side could be lengthened. Increasing the LSA opens the exhaust earlier, but decreases overlap. As with a wider exhaust lobe there will be a downside if the overlap was correct in the first place.
This leaves us with advancing the cam. Let's look at some valve events by starting with a typical aggressive SBC HR cam: 294/300 on a 110LSA installed 4 degrees advanced. The valve events are IO/IC-EO/EC 41/73-84/36. This gives us 77 degrees of overlap. We want to use a 100hp shot and compensate by opening the exhaust 10 degrees earlier. The valve events we want are 41/73-94/36. To get this, we can open up the LSA to 112.5, increase the exhaust duration to 310 degrees, and install it on a 106ICL (6.5 degrees advanced). We now have valve events of 41/73-94/36 with 77 degrees of overlap - just what we wanted. This might lose 20hp or so compared to the first cam off the juice, but gain an additional 20-30hp on it.
The compromise position is somewhere in between. Open up the LSA a couple of degrees, advance the cam a couple, and bump up the exhaust duration a bit. The choice is yours - but keep in mind that most cams are so far from optimized in the first place that a properly chosen nitrous cam is likely to be better both on and off the juice. So there is a compromise but if you were going for optimum performance in one area or the other you would have your cam ground specifically.
A cam optimized for nitrous (N) is quite different than a cam optimized for NA use. It will make a lot more power while on N, on the order of 10-15% of the nitrous boost, but lose quite a bit compared to an optimized NA cam off the juice. I want to take a minute to explain a little about this and offer suggestions about compromises that will work pretty well with either.
Using N poses a problem. An optimum head for nitrous use would have a larger exhaust valve at the expense of a smaller intake valve. When you add N, you are drastically increasing the volume of exhaust gasses needing to be pumped out. If you add a 150hp shot on to a 300hp motor, 50% more exhaust gas is created, for example. Not only due the pumping losses go up dramatically, there is more residual gas and contamination of the intake charge to deal with. The exhaust valve area would need to be 50% larger to fully compensate.
Not only is 50% more exhaust valve area completely impractical, it would severely compromise NA power. So, the cam must be used to compensate. The method of compensation is to open the exhaust valve earlier. As a rule of thumb, the range to look for is 10-20 degrees earlier with 150-300hp of nitrous. There are a couple of ways to open the exhaust earlier. We can increase the LSA, increase the exhaust duration, or advance the cam. As with all aspects of cam design, there are always tradeoffs. Increasing the exhaust duration will also increase overlap when typical cam profiles are used. If we had exhaust lobes specifically designed for nitrous available, which most of us do not, just the opening side could be lengthened. Increasing the LSA opens the exhaust earlier, but decreases overlap. As with a wider exhaust lobe there will be a downside if the overlap was correct in the first place.
This leaves us with advancing the cam. Let's look at some valve events by starting with a typical aggressive SBC HR cam: 294/300 on a 110LSA installed 4 degrees advanced. The valve events are IO/IC-EO/EC 41/73-84/36. This gives us 77 degrees of overlap. We want to use a 100hp shot and compensate by opening the exhaust 10 degrees earlier. The valve events we want are 41/73-94/36. To get this, we can open up the LSA to 112.5, increase the exhaust duration to 310 degrees, and install it on a 106ICL (6.5 degrees advanced). We now have valve events of 41/73-94/36 with 77 degrees of overlap - just what we wanted. This might lose 20hp or so compared to the first cam off the juice, but gain an additional 20-30hp on it.
The compromise position is somewhere in between. Open up the LSA a couple of degrees, advance the cam a couple, and bump up the exhaust duration a bit. The choice is yours - but keep in mind that most cams are so far from optimized in the first place that a properly chosen nitrous cam is likely to be better both on and off the juice.
#6
Thanks for the info, that answered a lot of info, it seems exhaust duration is the key.
#7
11 Second Club
Joined: Jun 2005
Posts: 1,537
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From: Was New Orleans, but swam to Baton Rouge
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#8
Nice. . . the necesity for an increase in exhaust duration while keeping the same overlap makes a lot of sense. I was just making sure that the greater piaston speed of the stroker engine wouldn't cause any excessive force with the use of the juice. I guess if you build an engine using the right alloys for the crank and rods it'll take the abuse.