Why not NOS?

[jay3000]

Originally Posted by Brucelee

You seem certain that the Box can deal with the NOS hit. I am curious as to why you believe this?

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

[Tool Pants]

That Tool Pants and his pictures....

[Brucelee]

Originally Posted by jay3000

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

It seems the IMS is the weak link in the Box engine. How might that be effected by a boost from either a Turbo or NOS.

It is interesting that Porsche has never offered up a Turbo on the Box. This is kind of out of character for them, as they have put them on many past models.

That could be coincidence or not. I guess I never thought of that before?

[angman]

More pictures wanted from Tool Pants!

[fragdude]

Originally Posted by Brucelee

It seems the IMS is the weak link in the Box engine. How might that be effected by a boost from either a Turbo or NOS.

It is interesting that Porsche has never offered up a Turbo on the Box. This is kind of out of character for them, as they have put them on many past models.

That could be coincidence or not. I guess I never thought of that before?

Putting a turbo on the Box would put the Box in 911 territory which is a big no-no cause when the guys who pay the big bucks for a 911 realize that a Boxster can be faster than them they will get kinda mad. This is also the reason why our engines are so muffled.

and on the above picture: I want to know what kinda shift kit that guy has!

[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

[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

[jay3000]

Originally Posted by dmcutter

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

And, we've all learned something.. Hopefully Kirk will tell us more. He seems to know alot more than "it'll blow it up"..

It does seem to be a difficult engine to get much more performance out of.

[Kirk]

Originally Posted by jay3000

It does seem to be a difficult engine to get much more performance out of.

I'm not sure there's really anything in particular about this engine that makes it more "difficult". The high compression ratio is great for a naturally aspirated engine. It's only when you try some form of induction that it's a problem. The lack of improvement from headers, exhausts, and intakes on performance just tells me that Porsche makes a good, highly tuned product from the factory that is already pretty much at the peak.

The tight packaging is a bit of an issue though. Where do you even put a supercharger, turbo, or intercooler? The engine bay is really tight, which makes these issues more difficult to overcome.

But back to the engine... again I don't think it's so much "difficult" as it's just underdeveloped. If you could buy some pistons that would drop the compression ratio to 8:1, a forged crankshaft, forged connecting rods, etc., then you could rebuild the bottom end for not 4 psi of boost but more like 14 psi of boost and run that all day long with no problems. But nobody out there is really developing these kinds of parts for the Boxster engine. That's a shame... but for the same money or less people would just rather drop in a 911 engine, which makes a lot of sense.

[dmcutter]

I talked to Marc at Turbowerx a lot when he was developing the kit for the 3.2 and he said he could do a monster build with low compression pistons and such and run high boost and get around 500 hp. He estimated the cost would be about what most people are talking about for a 3.6 transplant. I would really worry about that much power being tractable, though...last year on the TOD in the rain my PSM kicked in a few times. Twice the stock power would be pretty hairy unless I kept it about 2 gears high and below the powerband.

[Adam]

Originally Posted by dmcutter

I talked to Marc at Turbowerx a lot when he was developing the kit for the 3.2 and he said he could do a monster build with low compression pistons and such and run high boost and get around 500 hp. I would really worry about that much power being tractable, though....

It wouldn't be usable power in the first couple gears since boxsters don't have an LSD. You would have to budget in an aftermarket limited slipper if you did something like that.