Zex nitrous kit has had good reviews when it comes to safety. I would keep it to around a 50 shot tho, wouldn't want to blow a nice engine like that.

 

The 4.2L could probably take a 100 hp wet kit. The wet kits are safer because you add fuel to the nitrous charge at the same point it's injecting. A dry kit you have to run a vac line to your fuel pressure regulator and it increases the fuel pressure of your injectors. The problem with a wet kit is that the fuel can puddle in the intake manifold if you inject it way to early. Best to inject it right before the throttle body. Or if you do direct port injection and mount 8 nitrous nozzles in your intake manifold. One into each runner where it goes to the port in the head. That gets really expensive.

For a 50-100 hp shot though a dry kit would probably work fine. Its usually when you run 125, 150, 175, 200 hp shots that your injectors can't add the power so you run a wet kit which taps into the fuel return line and takes fuel from there and injects it with the nitrous through the nitrous nozzle.

The 4.2L isn't a weak motor. The A8 w/ a 100 hp shot would be like the older S8. Probably out run it too. You ever see the movie Ronin? They sprayed an Audi S8.

http://www.andysautosport.com/audi/2...xide_kits/zex/

You'd have to get a switch that can work with the Audi's throttle body electronics since I believe you have drive by wire which doesn't use a throttle cable.

 

Remember that Ronin was a movie - it's doubtful that they had an operating N2O system in that car. And what someone above said seems to hold true - I have done reading in the past in the A8 forum and it seems that every fifth post or so was related to a transmission problem.

You could probably get around some of the issues with the wet/dry system by spraying the nitrous in ahead of the MAF, so that it reads the additional oxygen charge and fuels the engine accordingly. I'd do what another member said though, and keep it to a 50-shot. The motor may handle 100, but the transmission probably won't, and I doubt there's that much extra headroom in the OEM injectors. You're likely to be running static on the spray.

 

that's what water/meth injection is for

 

Using nitrous to cool an intercooler is such a waste of good nitrous. The nitrous sprays at like -129 degrees so if you spray it into the engine, you get a very cold intake charge, and the added hp. The colder intake charge really helps on forced induction cars, so you usually see more gains on a turbo or sc car than on an n/a car.

I don't think spraying the nitrous before the MAF has any effect. The maf won't read it. The fuel is upped via a t'd vac line going to the FPR that raises the FP in accordance with the flow of the nitrous (on a dry kit). In a wet kit, you tap into the test port in the fuel rail and add an elbow-fitting. It takes fuel from the return line and sends it up to mix at the nozzle with the nitrous charge. Remember fuel pressure is very high but the engine doesn't use all the fuel that is being sent up from the pump. A lot of it gets sent back to the tank via the return line. Now if you have a returnless fuel system then it's different. But most cars have a return style fuel system.

I can tell most/all of you guys have never used or installed a nitrous system. Just telling this guy "it won't work" without any in depth knowledge of how a nitrous system works, is wasting his time. If you don't know, just say "I don't know, you should research" or just don't reply.

A 4.2L can run on a 100 hp shot all day. As long as you have the nitrous system tuned (it wouldn't hurt to put it on a dyno and check A/F ratio with a wideband O2 sensor. Then you can adjust the jets to keep the A/F in check. You can get it close out of the box, but personally I'd like to fine tune it. I'd run a wet kit, and then adjust your fuel jet to the nitrous jet by testing AFR. I'd also recommend getting a set of copper plugs that are a heat range colder than stock. You will change them frequently with nitrous, and platinum plugs don't work well with nitrous.

I have a nitrous car with a dry kit, and I helped my friend put a wet kit on his car. He sprays 150 shot and runs it almost every weekend at the track and very frequently for cash on the street. We even have our own nitrous fill tank at his shop.

 

throw a wet kit on that thing. call nos and talk to them about the jetting. id say start at 50 work your way up to 100 shot. you could probably safely run 125 shot if you run a colder spark plug. just make sure the system can ONLY come on when your at wide open throttle, thats where you can run into problems. the intake welds is just in the stupid movies. if nitrous is setup right youll be fine screw all the others who dont know anything about it. an audi is just a car and should be treated like any other. an a8 on the bottle would be pretty damn cool and nobody would see it coming. its easy to set up and your car is stock 90 percent of its life. you only use the nitrous sometimes so it really isnt that hard on your motor. supercharging ang turbocharging puts a strain on your motor everytime you drive it. alot these guys are scared of nitrous and dont know anything about it. ive ran a 100 shot on my v6 lincoln ls for years with no problems and 150 shot on numerous 5 liters. i dont know about your tranny could be an issue, might not be. spray wet right before the throttle body. NOT through the maf. colder plug with a smaller gap. zex kits are real safe and easy to setup. they shut down the nitrous if theres not enough fuel pressure and they read wide open throttle. you could do an rpm window switch so that it comes on then shuts off right before a shift then comes on again. lots of things you can do. it will be awesome. im putting my kit on my b5 s4 this winter. these cars are cool going faster makes them cooler.

 

That's exactly why many are "scared" of spraying an A8. Take a look at it sometime - there are a LOT of people who've had transmission trouble on the A8 without any type of power adders. It's not that the motor can't necessarily take it - the transmission seems to have been borne out as a weak spot on these cars, before throwing another hundred horses through it.

Try not to advise people until you look at the full situation - an A8 drivetrain isn't a Mustang drivetrain (and honestly, nitrous abilities included, it's better off for it). These cars have documented transmission issues that surface with higher miles. Throwing nitrous at them like they're fox-body cars is hastening the problems.

Scott Long - what cars are you guys spraying? Just curious, but I have a feeling they're cars with performance intentions. The A8 wasn't one of those. Hopefully everyone's keeping in mind that the OP is talking about a luxury sedan, not a pocket-rocket or pony car. Nitrous is great, and I'm a fan, but more than just the engine's ability to handle it needs to be considered.

 

again... my $.02... the engine and the car can handle the 100 shot... BUT... the transmission will not... not on that auto tranny. good luck with that end of it unless you're going to purchase a tranny from Stage 10 or swap in a Manual 6-speed. Someone over at Audiworld has done it before on an older A8, so it's not impossible. Just be careful with the instaneous power on that tranny. Maybe you'd be better of with a reliable option such as the soon-to-be-released PES supercharger for the 4.2L A8.

 

150 shot that b*tch and lets end this non-sense, if the man wants to shoot up his lady with some nos, let him do it, and make some vids cause i bet that sh*t would take off..go to an authorized NOS shop and ask them what they think.


look, as long as you don't shoot it in 1-2 gear or low rpm, you should be OK i mean I have an A6 with a TIP and the engine is doing around 420 bhp and the tranny seems to be putting up with it okay (also have a tip chip) but it's with k04's not NOS :-D haha i mean, you're not planning on shooting every time you start the car are you? just when some S4 B6/7 pulls next to you and you wanna be able to keep up right? or whatever, track day, should be ok, just don't abuse it... i mean i abuse my tip more then i should, but it will bite me in the *** in the end...

 

I have a little experience with this on domestic V8's. I agree with Scott. A direct injection setup is the best solution for complete dispersion of NOS and fuel. They are expensive and custom to install, but for the serious NOS-er, it's the way to go. However, you do run the risk of fuel pooling in any wet kit application. A direct injection system make sure that all cylinders receive the same amount of each (NOS and fuel) so that, for example, the furthest cylinder from the throttle body (TB) isn't starved. In a standard dry kit where you're blowing NOS through a ring located at the TB or MAF, the first cylinders closest to that will get most of the NOS and less and less as the NOS finds its way to the back of the intake manifold. Under boost, there's no problem. NA, there is.

Does anyone know what these cars dyno at AWD stock and what AFR's they're tuned to??

I've never liked NOS alone. It makes a driver very dependent on it because the car never feels the same when off it. Kinda like crack!

A 50 shot shouldn't harm the engine much -- nor with you be able to tell really. But all versions of the 4.2 V8 are 11:1 compression, if you go much higher you run the risk of blowing your heads off or, as someone mentioned, blowing the welds in the heads -- WOW!! NOS or any power adder for that matter add to the dynamic compression ratio and 11:1 is already very high.

I didn't know about the weak transmissions on these cars. Who is level 10? Do they build beefy 6 speed trans's for our cars?