Why not NOS?

[Kirk]

Be careful.... 75 HP shot? 150 HP shot? NOPE, ain't gonna happen. The issue is not what the engine can "take" as in how strong the crank, pistons, connecting rods, etc. are. That is not the issue at all as I am sure the bottom end is more than strong enough to handle the extra power of a mild NOS shot. The problem is DETONATION.

Plain and simple it's detonation that causes an engine to blow. Sure you can get detonation from a poor mixture of nitrous and fuel, but as stated previously most modern systems are pretty good at getting the right ratio into the engine and for a mild shot you would do fine with the stock fuel system without needing a separate pump or tank, simply T-ing off of the stock system and stock fuel pressure.

The big problem with our cars and why they can't run a simple 75 shot like a Honduh is that this is already a high performance engine from the factory. The stock high compression ratio (11:1) is the main issue here. If squeezing even a very mild shot of nitrous into a high compression engine like this you run a real risk of detonation and destroying your engine. The same goes for adding on a turbo or supercharger where only mild levels of boost can be tolerated. That's why most turbo engines are around an 8:1 compression ratio.

A couple of sources I've researched this in the past with are this book by A. Graham Bell:

http://www.amazon.com/Induction-Performance-Practical-Supercharging-Turbocharging/dp/1859606911/ref=pd_bbs_1?ie=UTF8&s=books&qid=1218481199&sr=8-1

If you want to do ANY kind of forced induction with your car BUY THIS BOOK!!! It is an excellent resource and I've read it a couple of times now just for fun.

Another resource I have is an excellent review of nitrous use that Sport Compact Car did around 1999 or 2000.

Both of these sources STRONGLY recommend NOT using nitrous on anything around 11:1 or higher compression ratio with a simple NOS system (like the ZEX setups). Sport Compact Car said that even a 50 HP shot of nitrous was pushing it at 11:1. About the only thing you could do for $500 would be a 25 HP shot that would probably be safe, but it may be difficult to find the proper fuel and nitrous jets to get that small of a shot.

To go with a higher nitrous shot you'd have to either rebuild the bottom end with lower compression pistons or put together a "safer" system than what you can buy for $500. What would I do if I were building a safer system?

1. I'd get a Knock Link or other form of detonation detection and display. I've got one in my car from a previous turbo WRX. Photos are in my thread in the Show and Tell forum.

2. I'd get nitrous pressure and fuel pressure gauges.

3. I'd get the appropriate window switches to make sure the nitrous doesn't kick in too low or stay on until red line. MSD and NOS sell these.

4. You'd have to pull ignition timing with a bigger shot of nitrous. No, you would not reprogram the DME. If you did that, then you'd be driving around with retarded timing all of the time, even when you're not on the juice, which is retarded. Instead, you would need to switch the ignition system over to one of the MSD (or equivalent, there are other options) ignition systems with controllable timing and set it up to only retard the timing when you're hitting the NOS.

5. Colder spark plugs.

6. Lots of prayer. I'm sure there's more that I'm missing... Of course a dedicated fuel pump and tank with high octane fuel wouldn't hurt, although it probably would not be compatible with your O2 sensors and catalytic converters.

With all of that in place... maybe you could run a 50 shot of nitrous. Maybe more if you really want to push it. What's the point then???

Kirk

[Kirk]

This is Kelvin Ho's car from Southern California.... I think somewhere in the LA area. He had his nitrous system up for sale on eBay a couple of times this last winter. I don't know if he ever sold it, but it was like $450, used....

[Kirk]

Here's a 996 with a front trunk mount...

[Kirk]

Another... not sure who's this is, but it looks like it's in a Box

[Kirk]

And my favorite, two nawz bottles mounted on the speedster humps...

[jay3000]

Kirk. Would not the vast majority of things you listed also have to be done with any forced induction setup?? Are the turbo, and supercharger setups addressing all of these issues or are they just keeping the boost down low and hoping the knock sensors will retard the timing enough to save the engine??

Another issuse would be traction control. Another member mentioned a "traction control swith", and I thought "why". Then it occured to me. Engine management cuts fuel to some cylinders.. That wouldn't work.

[dmcutter]

I feel compelled to rat Jay out now that he's joined and is posting. HE is the one who instigated all this.

[Kirk]

Originally Posted by jay3000

Kirk. Would not the vast majority of things you listed also have to be done with any forced induction setup?? Are the turbo, and supercharger setups addressing all of these issues or are they just keeping the boost down low and hoping the knock sensors will retard the timing enough to save the engine??

Yes, with any forced induction setup you'll have to pull timing as the boost pressure increases and it would be wise to have the gauges, etc. (although I would use EGT, boost, and a wide band O2). But with a turbo or supercharger you're pretty much running forced induction all of the time, unlike nitrous, which is just temporary. So with a turbo or supercharger you would re-map the DME or use a piggyback system to control the fueling and timing. You need that any way as you'll need more fuel out of the injectors. With nitrous you don't need a new fuel map as you can simply provide the additional fuel with the nitrous.

Still, even with remapping the DME, you'll have to run at a fairly low boost pressure. It's tough. People get greedy (just as with nitrous) and end up turning it up to get more.... As a result you see a lot of people who buy the turbo or supercharger kits and then suddenly want to sell their cars within 6 months... Obviously there are a couple exceptions on this board where boost has worked well for them, over the long haul.

Hoping the knock sensors will retard the timing is a big hope. I personally wouldn't count on it. Even the Knock Link is wishful thinking. The problem is that once detonation hits, if it hits hard enough, fast enough, it may be too late to react whether it's by lifting the throttle when you see knock on a Knock Link or whether it's by the DME pulling timing.

Kirk