I see a lot of posts talking about safe HP when it comes to nitrous but almost nothing about torque. That's strange, because torque is what breaks things.
I have an 1985 L98 auto that came from the factory with forged pistons and the consensus seems to be that a 150 shot is pretty safe even on engines that came with cast or hypereutectic pistons. Holley sells a 150 shot NOS kit for L98s so they seem to believe that is safe also. But when you run the numbers through the torque=HP*5252/RPM formula you get some surprising results.
At a typical 2400 RPM launch the stock engine is putting out about 145 HP and 310 ft. lb. of torque. Add the 150 shot and at the same 2400 RPM launch the engine is now putting out 295 HP and a shocking 640 ft. lb. torque! That's more torque than a brand new ZR1 ever makes -- and it has 6 bolt mains and a forged crank.
If you then accept that 640 ft. lb is safe for a stock L98 it's a straight forward matter to hook up a progressive nitrous controller to keep the torque constant at 640 ft. lb. through the entire 2400-5000 RPM rev range. The engine would be putting out an impressive 610 HP @ 5000 RPM and the car should be crossing the quarter in the 10s at about 130 MPH.
So my question is whether 640 ft. lb. is safe for a stock forged piston L98, and if not why does everyone seem to believe it is?
I really doubt it is going to be that much torque, it might be using the progressive controller, if your car does hook up it would probably not be good for it... but unless you have some slicks or drag radials it will just light up the tires, my C4 has nitto NT05's on the rear and it still spins the tires off the line occasionally and i dont have 600 + ft lbs of torque......
First things first. The nitrous system should not engage under 3K RPM. I ran a 50 shot at times in the past (helps when boost is not really "in" yet) and lowered it to 2800 RPM, and just did not feel comfortable. And this was on a fully built engine. Eventually went away from the nitrous all together.
Max nitrous I ran on my '85 was 125 shot, but am looking forward to hearing the results of your attempts to run a 365 shot on a stock L-98.
I made 590 RWTQ with my L98 bringing on a 140 shot at 2500. I can't explain why your theory of maintaining 600 TQ from nitrous inception to shift point won't work, but I don't think it will.
I also think that RPM is harder on parts than power/torque. I broke a piston on my stock bottom end from RPM, not nitrous use. I ran probably 100 bottles or more through the stock TPI and never hurt anything. I put an intake on it, never sprayed it, but was shifting it at 6300 and broke a piston.
First things first. The nitrous system should not engage under 3K RPM. I ran a 50 shot at times in the past (helps when boost is not really "in" yet) and lowered it to 2800 RPM, and just did not feel comfortable. And this was on a fully built engine. Eventually went away from the nitrous all together.
Max nitrous I ran on my '85 was 125 shot, but am looking forward to hearing the results of your attempts to run a 365 shot on a stock L-98.
Good luck!
While I agree that using a full shot of juice from a launch is a bad idea, I was simply pointing out that if you install a kit without adding anything fancy like most people probably do, the system will engage the full shot as soon as you hit the WOT switch -- which for an auto car is around 2400 RPM. I can only assume the systems were designed with this in mind.
Even if you do put in a 3K window switch a 150 shot is still making 590 ft. lb, and a more conservative 125 shot like you were running is about 545 ft. lb when it engages. Perhaps my skepticism wasn't showing through on my original post, but it all sounds like a lot to me.
I really doubt it is going to be that much torque, it might be using the progressive controller, if your car does hook up it would probably not be good for it... but unless you have some slicks or drag radials it will just light up the tires, my C4 has nitto NT05's on the rear and it still spins the tires off the line occasionally and i dont have 600 + ft lbs of torque......
The laws of physics say that if you really are making an extra 150 HP on top of the stock 140 or so at 2400 RPM you will make 640 ft. lb. There's no breaking those rules! Even tire spin will not prevent the engine from making that torque briefly until the revs start to rise.
That being said, does a 150 shot really make 150 HP at all revs? Is there some efficiency differences at lower RPM that might reduce the amount of HP the engine really makes, even if the nitrous flow is constant?
I made 590 RWTQ with my L98 bringing on a 140 shot at 2500. I can't explain why your theory of maintaining 600 TQ from nitrous inception to shift point won't work, but I don't think it will.
I also think that RPM is harder on parts than power/torque. I broke a piston on my stock bottom end from RPM, not nitrous use. I ran probably 100 bottles or more through the stock TPI and never hurt anything. I put an intake on it, never sprayed it, but was shifting it at 6300 and broke a piston.
If I run the numbers on your results (based on reading a 1985 L98 power curve published by GM in the owners manual) I figure you were making an extra 130 HP @ 2500 RPM. That's awfully close to your 140 shot so the numbers seem to check out.
I am also impressed you have a dyno sheet proving you were actually making 590 ft. lb. without breaking anything. I am a bit amazed that can be done on a stock engine but it gives me hope that I can make some absurd amounts of power on my own L98.
You do raise a valid point though about the engine speed. Is 590 ft. lb. at 2500 RPM somehow better than 590 ft. lb. at the 5000 RPM redline? As long as you don't exceed the stock redline I assumed not, but perhaps someone who has blown some stuff up can explain if this is true or not and why.
I made 590 RWTQ with my L98 bringing on a 140 shot at 2500.
Yikes. I just realized you said "RWTQ". Assuming you have a manual car and 15% drivetrain losses, that works out to about 690 ft. lbs. at the engine. How is that thing still in one piece?!?
690 ft. lbs @ 2500 RPM also works out to 330 HP or a 180 shot based on a 85 stock HP of about 150. If your L98 is a later model it will have more stock HP than in 85, but I still figure you must have been getting more than 140 HP from the bottle.
the turbo callaway l98's made 560ish tq at 2500 rpms.
I feel the way the power is ramped in will decide if something like this will live.
hitting 6XX tq at 2XXX rpms with instant on is shocking the rotating parts.
If it were me, I would want to smooth into it. I would think the rod bearings would hate you at the very least.
as for progressivly controlling your hp to keep it at 600ish for the full pull, I would like to see the math on how to maintain this, and how the nitrous numbers increase.
I guess aks has an idea with the 365 shot.
Last edited by bill mcdonald; 08-19-2009 at 04:03 PM.
the turbo callaway l98's made 560ish tq at 2500 rpms.
True, and this would give me confidence if it weren't that Callaway completely rebuilt the engines -- including replacing all the internals (pistons, rods, valves roller cam, crank, bearings, even 4 bolt mains). That's why trying to do something similar on a stock L98 seems questionable.
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I feel the way the power is ramped in will decide if something like this will live.
hitting 6XX tq at 2XXX rpms with instant on is shocking the rotating parts.
If it were me, I would want to smooth into it. I would think the rod bearings would hate you at the very least.
Agreed! Thus the requirement for a progressive controller.
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as for progressivly controlling your hp to keep it at 600ish for the full pull, I would like to see the math on how to maintain this, and how the nitrous numbers increase.
I guess aks has an idea with the 365 shot.
Not too tough really. You jet for a 365 shot and set the controller to start off at about 40% PW or perhaps even less (ie: maximum 150 shot) and work up as the RPMs rise. Here's a sample screen cap from the software used to do this:
The net result is constant torque and a linear rise in HP. Here's a graph I made that should help visualize it:
The yellow/green lines are for the 640 ft. lb. progressive nitrous. The others are for a stock motor and a constant 150 shot See the legend at the bottom right corner. You might need to click the image to see full size.
Given the nitrous controller is so readily programmable is there any reason not to set it up this way? If 640 ft. lb. is on the steep side, I could obviously go with something more modest -- perhaps 500 ft. lb -- about the same as a 100 shot hit at 2500 RPM. Did I just say "modest" and "500 ft. lb" in the same sentence?
True, and this would give me confidence if it weren't that Callaway completely rebuilt the engines -- including replacing all the internals (pistons, rods, valves roller cam, crank, bearings, even 4 bolt mains). That's why trying to do something similar on a stock L98 seems questionable.
Agreed! Thus the requirement for a progressive controller.
Not too tough really. You jet for a 365 shot and set the controller to start off at about 40% PW or perhaps even less (ie: maximum 150 shot) and work up as the RPMs rise. Here's a sample screen cap from the software used to do this:
The net result is constant torque and a linear rise in HP. Here's a graph I made that should help visualize it:
The yellow/green lines are for the 640 ft. lb. progressive nitrous. The others are for a stock motor and a constant 150 shot See the legend at the bottom right corner. You might need to click the image to see full size.
Given the nitrous controller is so readily programmable is there any reason not to set it up this way? If 640 ft. lb. is on the steep side, I could obviously go with something more modest -- perhaps 500 ft. lb -- about the same as a 100 shot hit at 2500 RPM. Did I just say "modest" and "500 ft. lb" in the same sentence?
I don't think you can spray enough nitrous to over come the TPI intake like you've drawn in your graph. If you look at even the highest boosted turbo/sc motors at some point the graph rises then peaks and then falls. You might be able to overcome a little bit but to have a solid flat torque line due to a progressive controller I don't think will happen.
Besides if you hit a stock L98 with a 350 shot you might be able to do it once but that will be the only time Youre also going to need some serious fuel for that.
I don't think you can spray enough nitrous to over come the TPI intake like you've drawn in your graph. If you look at even the highest boosted turbo/sc motors at some point the graph rises then peaks and then falls. You might be able to overcome a little bit but to have a solid flat torque line due to a progressive controller I don't think will happen.
Yeah, you are correct about that. N20 only has about 2.3 times the oxygen content of air so even if the stock engine was consuming pure nitrous it would max. out at about 530 HP. Of course nitrous is under pressure so theoretically you could also use it to supercharged the thing...
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Besides if you hit a stock L98 with a 350 shot you [i]might[/] be able to do it once but that will be the only time Youre also going to need some serious fuel for that.
That's where I scratch my head. What would ultimately kill the engine? It shouldn't be the torque (cylinder pressure) since others on this list have already reported making more torque than I am talking about (see neat's post about 590 RW torque) on their engines..
About the fuel, yeah you would need some fuel system work. I think the stock injectors are only good for 400 or so HP.
I created that on a spreadsheet, but I read the values off the printed power and torque curves in the owners manual. I scanned the image then used the Gimp to read off the coordinates.
I put a copy of the scanned image here if you don't have your manual:
If you want a copy of the spreadsheet I can post that also. I did it in OpenOffice.org which is free to download.
Admittedly my original assertion of a 640 ft. lb. 400+ shot was not realistic, but I can't see why a progressive 200 shot wouldn't be.
Here's a more practical graph that shows the stock engine (red & blue), a progressive 200 shot with peak torque of 425 ft. lb. (green & yellow), and a fixed 150 shot (purple & light blue) starting at 2400 RPM.
That huge torque spike of the fixed 150 shot is what I want to avoid, and what I expect could result in a broken engine. The relatively modest 425 ft. lb. hopefully won't!
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How much torque can a stock L98 safely make?
Youre also going to need some serious fuel for that.
