This is a very usefull thread. Please, lets keep it that way. I respectfully ask that you two remove the comments and picture. Please.. I've put a lot of time into this subject and would like to keep this thread a usefull learning tool.
This does get me thinking of failures though!
When you place an impact on the parts of a car they may not be able to stand up to those shock loads.
Picture a 16 penny nail thats already 1/2 way into a 2x4.
Now take a 16lb hammer, raise it 3 inches above the head of the nail and strike it as hard as you can. You *might* move it.
Now picture that same hammer raised 2ft above the nail and strike it as hard as you can. It will definately move and just might fall to one side or the other because the force was not straight down and was just too much for it to handle.
This is the whole point in controlling nitrous. Ramping shot size is like little hammer strikes vs a big ole wallap all at once.
If you slowly ramp up the motor load, the engine can usually take more than you might think possible! Trevor in england has proven this many times. I'm blown away than he can usually start off with a 50% increase in power. And wind up between 75% and 100% power increases on otherwise stock cars. He's even pushed one to a 175% power increase before the motor broke.
The only two things he really adresses is spark plugs and making sure enough fuel can be supplied. Plugs are cheap and easy to replace. Getting the fuel system up to snuff however can get expensive. Consider this though, what burns? It's not the air, its not the nitrous, and it's not the source of ignition. It's the fuel
! If you can't get enough fuel into the engine.. your only going to lean out the a/n/f charge and break parts.
Me personally.. I have a "old school" rule of thumb I have developed over the years. I have in the past limited power increases to 35% over what was delivered in stock form. I had for years considered that my power limit. And instead of adding more power to go quicker.. I focused on putting it down to the pavement.
Currently on the ranger I'm at 43% of a power increase (297hp now) and next summer I'll up it to 51% (314hp). She's got 43k miles on it and I've not seen one hint of any damage to my little 4.0L ranger.
Here is a list of what will typically fail with a fixed hit shot of nitrous.
(fixed hits always lean out a a/n/f charge for a second or two when activated. That makes the burn ultra hot and extremely powerful. That.. breaks parts)
FIXED HITS AND INITIAL LEAN OUTS
Broken rods is the number one danger! When a rod breaks you'll be lucky to walk away with a intake manifold and some valve covers. Interestingly too.. rods almost always break on the down stroke.
High wear on piston skirts. Piston slap and blow by become the norm.
High wear on the rod bearings. Usually the only down side is reduced life of the motor.
High loads on the main bearings. Usually not a failure.
Piston faces get too hot and will spatter aluminum. This can be seen as specs on the spark plugs.
Lifted heads The main head bolts stretch. Once they have.. you'll never get to the same power level w/o replacing them. And it's likely you'll have a headgasket leak too.
Auto tranny clutchs can slip. This is not all that bad actually because it can help remove shock to the rest of the drivetrain. However ETs will get slower and slower.
Manual tranny gears can break. (any of you T5 mustang guys ever break 3rd? I have)
And one last thought about shock loads. Shock loads are not a one time event. Those shock loads rebound *back into the tranny / engine*. A manual tranny car with a fixed hit kit and spraying off the line is the absolute worst possible shock loading you can do. Thats why you see and know of so many people who will only spray after they have left the line by about 5-10ft.
The only real "downside" to ramping is the cost of controlling nitrous and fuel.
You'll easily spend double the money up front. But if efficiency is paid attention to you can recoup that cost in 1 - 2 years of spraying.
Honestly.. there are no other down sides. If your willing to increase power by 50%.. fixed hit kits are dangerous. (75shot on a 4.0L ranger) But ramping it is easily doable and you'll have no side effects if the air, fuel, spark, and nitrous are all in balance.