Why not NOS?

[skip_168]

Originally Posted by jay3000

Can the bottom end handle 75 HP from a turbo or supercharger?? What would the difference be???

ok, well here is the deal..

A turbo or supercharger takes air,(19% oxygen), and compresses it.. The fuel injection system can keep the air/fuel ratio at about 14.7 to 1 even with the extra oxygen & air from the turbo or supercharger.

With NOS, you are injecting liquid Nitrous Oxide into the engine, about 200 times more oxygen than the fuel ingection system can handle. If left to it's self, this would lean out the mixture & act like a blow torch and melt down a cylinder head.. this is why a NOS system has an additional fuel nozzle with the NOS nozzle.

Here is the real problem: getting the mixture right

I know the companies who make the systems say its all good, but if you are off on the mixture by even a little bit, your 10k boxster engine will turn into a boat anchor in about 25 seconds...

Now back in the day when I was building air cooled Porsche engines, NOS was a BIG NO NO.. just due to the fact that the extra HP brought along with it alot of extra heat that an air cooled engine could not get rid of fast enough..

[944boy]

The biggest problem is the F&F ruined the reputation of Nitrous. But this is not a limited discussion. The 944 line has been out for 26 years and adding nitrous brings up the same kind of debate. There are some very sophisticated systems now that plug into the OBDII and meter based on injector duty, RPM and so forth. A well done system has no more risk than any other bolt on mod. It will be cheaper initially but you do have to refill the tank. is it worth it? Thats your own decision. I am sure people have added nitrous, I have heard of it on other boards. If you are interested I would do the research with nitrous guys, they may tell you its not worth it for your car. But I would inquire with someone who is neither selling a product, or bent on maintaining a strictly OEM car.

Just my .02 while sitting in an airport at 5am.

[dmcutter]

While researching something else recently, I think it was 3.6 swaps, I recall seeing and IMS upgrade/replacement or something such as that on a site. If the IMS is the weak link since they changed the design, can shaft bearings be replaced/upgraded to handle additional power?

[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

[Jake Raby]

The issue with the 3.4 would be the cylinder wall thickness. Even with our proprietary Nickies cylinders and installaction processes, cylinder integrity under boost would be a concern with the 3.4 bore size.

At the current we are working on two Turbo engine sizes, one is based off the stock 2.5 engine and remains 2.5L, but uses much thicker cylinders and is designed to see serious boost levels. This engine package will reliably create 300RWHP easily at low boost, using all Turbo specific components like our billet rods, upgraded rod and main bearings as well as thermal barrier and friction reduction coatings, dished (boost specific) pistons and a camshaft thats further optimized for boost.

The other is based from the original 3.2 engine, but we use an even thicker cylinder for serious levels of boost. This combination is still being designed, but I expect 400HP at low boost a possibility..

More power could be made, but we are engineering reliability into these packages, not maximum output and thats the rreason why we want to create big power from lower boost levels, not putting the engine "on edge".

Any power adder has the capability of enhancing output, or blowing the engine to bits- effectiveness is 100% in the subsystems and engineering that goes into them, from the fuel tank to the exhaust pipe..

I'd certainly never add boost to a stock 9896 engine, it doesn't have the proper CR and has inherent engine issues that create failures when being driven mildly while being well maintained.. Adding boost has proven to be a catalyst for most, while some have gotten decent mileage from them..

I won't replace my motor again with a 2.5, that's for sure. I'm going for wicked-fast next time around.

Guys like you and their desires are exactly what we hope to fill, both normally aspirated and forced induction.

Anyway, hate to steer the topic way off track, especially since I am a new guy here.. So if you want more discussion maybe we should start a new thread and allow the NOS conversation to ecape from the Hi-Jack :-)

[dmcutter]

Since I started the thread, you have my permission to go off on the turbo tangent.