I gotta side with Weissach. Even though you can monitor AF by watching the o2 sensor or by a wide o2 kit. Your still unable to see the AF ratio per EACH cylinder. When using 1 NOS injector spaying into the plenum, end cylinders may run lean. Over time even a small 50 shot could eventally damage ring lands.

Now stick an NOS injector into each intake runner (also with fuel), then 100 -200 hp is safe.

 

Here's a couple of options for making one:
http://www.clarks-garage.com/shop-manual/fuel-20.htm

 

Sublimate- Thanks for that. I may give that a try. Still going to try and find a machine shop.

So here's the update from last night. I didn't get to working on the car until close to 8pm last night so the progress is minimal, but they say slow and steady wins the race - but I hope to chage that once everything is installed!

Last night I routed the N2O line and the wire to trigger the solenoids. This was the most trepedatious part of this whole install for me as I had to dril a hole in my car. I know, I know - it's just a fricken car, but it still made me worried.

The other day when I pulled the carpet on the driver's side, I noticed a hole in the floor that led into the frame rail. So after staring at the damn thing for 2 days I finally drilled the hole and fed the N2O line into it. Then I treaded the solenoid control wire, and finsihed it off with a rubber gommet. Unfortunately the grommet is a bit loose (I.D.), so I put a tighter one on too with the intention that I'll put some RTV or something to do a final seal after I've tested things and am sure that I don't have to re-wire/re-route things.

I started on the wiring, but didn't have any spade connectors left so I stopped there. I should have all the wiring done tonight.

Things left to do (sans wiring):
* Get fuel rail fitting made
* Make platform for N20 bottle
* Get bottle filled
* Give it a try

Pics:

 

True, but unlikely. we are not shooting the spray straight up, but pointed to the middle of the plenum. actually, this would favor all but the front two, if at all even still, IT wont be a lean charge that any of the unbalanced cylinders create, it could be an unbalance of the fuel air ratio COMBINED. This means some cylinders would produce a couple of more hp than the other, and thats not a big deal. this is one of the reasons, you dont want to run 250hp shot through a single nosile.

So again, no cylinders will run lean as the air fuel mixuture is mixed AT THE NOSILE , not at the cylinder. also , why the ring lands?? detonation??? 50hp shot is pretty mild and like i said, even if you had the wrong mixture, it would have to be a perfect issue to create a 14.7:1 mixture to cause issues (or close to it. Odds are way against it as a complete failure of the fuel , would cause a way lean condition (ie 17:1 or greater) and as you should know, this is not a problem for heat. poor running yes, but not detonation or heat. usually, its buring valves you worry about or holes in the pistons. 50shot systems used correctly cant really create this kind of problem, unless you really screw something up and have some bad luck on top of that.

Next concern?

You can side with whom ever you want. side with the guy that "heard of" someone ruining (5) mustangs, or side with the guy that HAS used the NOS system on a 928, saw NO issues at all and had the luxury to take the engine apart after years of racing and NOS use and saw NO hints of problems on pistons, valves, rings or heads and valves AND also showed that leaning is not a part of position of the nosile. atomization of the fuel to the perfect ratio is mixed at the nosile and added to the stock engine managment controlled mixture of most of the hp produced. 240 + 50 hp.

MK

 

I know you have much experience with this subject on the track Mark. But I was looking at the longevity of the engine. Say over the period of 10,000 miles. Hot and cold starts and using all kinds of "blended" gasoline. I agree 50 shot is mild but still, all that NOS favoring a few cylinders than others will cause engine damage over time.

 

Hey Andrew- Did I understand Big Dave correctly- are you folks having a Beer Night next Thursday? I'm up in Michigan next week for recurrent training. When and Where-?

N!

 

The NOS and additional fuel spray together in a predetermined proportion. Assuming that this proportion is happy happy, are you saying that the additional fuel sprayed and the NOS sprayed choose to part company inside the plenum to the point that NOS in concentrated form gets to some cylinders without much or any of the additional fuel?

I would believe that the happy-happy proportion isn't quite so precisely happy happy in each cylinder - it could vary a bit, but would it really vary enough to cause concern? I suppose that I can see the NOS/fuel mixture favoring some cylinders more than others causing some pistons to push harder than others.

By design, NOS systems are infrequently utilized.

If you drive 100,000 miles with NOS installed, how many NOS injected miles are you really driving? How many cumulative operating minutes of risk would the engine be exposed to? 20 seconds of yeeeehaaaa a day, every day for a year adds up to 122 minutes. Perhaps the concern is greater for the maniacs that aim for 5 minutes of giddiap a day. Those guys would probably be our star producers for kill stories and I would probably worry about their engines a bit.

You aren't a maniac, now, are you Andrew?

 

Um, this coming from the guy that has no fear of racing with toothless cogs.

 

Obviously, we all have different tolerances of risk.

 

No, I'm not a maniac... yet. But I may have maniacal tendancies on occasion

Ok so here's what I got done tonight. I hooked up all the electrical stuff in the engine bay and made it pretty. Then I hooked up all the electrical stuff to the arming switches and placed the push button on the false pedal. Hooked the battery back up to test. I armed the swithces, and pushed the button...

"pa-pak" [release]... "pa-pak" solenoids are firing!!!

I didn't have time to hook up the tank warmer or the back end stuff tonight. I hope to get that finished tomorrow. With any luck, I might be able to test this weekend. Gonna fill the bottle tomorrow just in case. Sorry I don't have any pictures on this post. I did take a couple, but I need to go to bed now, so I'll post them later. Good night.

 

yes, yes, and yes. it was used on the street for over 20k miles with the NOS hooked up and used it on the street and on the track. obviously, at this time, it was not a daily driver. However, what part of the "NOS cant favor one or two cylinders" are you having an issue with. remember, NOS is mixed with fuel at the nosile, so a "few" cylinders cant be going lean or near stoich to cause a problem. you also dont use NOS on start up, cold or hot and who cares abot the gas. again, its only a 50shot.
also keep in mind that engines during street cruising, run at near the deadly stoich by design. engines dont cook at stoich during cruise (low power settings) they do when the mixture is at stoich and the mass flow is high enough to cause a detonation due to the increased pressures and heat.
its a narrow range, and you almost have to try to hit it right to have it happen on a 928. you dont hear of too many burned valve 928s. it happens, but its much more rare than on other cars.

Mk

 

well said. heck, a bottle gives 14 x 14 second bursts at 50shot if i remember correctly for a 10lb bottle OR, 30 min, 10lap race on a road course, used on all straights.
thats not much time of rough running if thats the only issue. however, if you had a serious mixutre issue, then it could destroy an engine ,and thats what we find out at the dyno

mk

 

You know... all this negativity/"oh you better watch out" stuff reminds me of whrn Andy K and Tim Murphy started their projects. Heck I think Herr-Kerr got a few funny eyes too. It's not like I'm going down the path to the dark side... ok maybe a little bit . I am not making any permanent modifications to my car - except for the hole in the frame rail, but I guess a strategically placed rock could do the same.
I figure, I'll run with this for a while, get my giggle juice jollies out of my system, and when I'm ready to play with the big boys, I'll de-install it, sell it to someone else that wants to have the same fun as me and then I'll look to put a supercharger in or move up to a different 928. In any event, it should be a fun ride!

 

People generally seem to act like it is the end of the world if you do anything out of the ordinary.

LEAVE IT STOCK!

The hell with that... Stock is boring.
If you want to go faster, then you have to take some risks.
Any power increase, puts additional strain on the internals, no matter what the mod is...

 

Mark is trully the aurthority on NOS and the 16v. Just to volatile for me. I've seen lean piston failure due to over shot. Becomes very $$.
As Mark stated, one nozzel spraying fuel/NOS into a plenum that was designed for DRY intake air is too much for me. I'ld ***** foot it.
Andrew your installing a well designed system, and probably won't have any problems. Hey by the way where are you mounting the bottle? I would choose the rear passenger foot well. Safest place in case of collision and easy to reach to if you have to turn off the master valve. Their I go again thinking of the obscurity.
I looked into NOS for my 16v. But ended up with Carl's SC. Once installed boost is endless and never run for a refill.