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plyhammer

Please don't be a hater, I am just trying to learn. I have the 79 n/a 924 and would like to put in a dry nitrous system for kicks. I didn't pay too much for the car but would like a little fun. I am looking at a simple 50 shot system but need to know if it works well with the cis setup. Has anyone used nitrous on theirs and how is it going? Thank you for you comments.

skemcin · Joined: 02 Sep 2003 Posts: 1284 Location: Plainfield, IL

plyhammer · Posted: Wed Oct 12, 2005 4:18 am Post subject: video

It doesn't pull up.

plyhammer · Posted: Wed Oct 12, 2005 4:20 am Post subject:

I will try to pull it up at home.

skemcin · Joined: 02 Sep 2003 Posts: 1284 Location: Plainfield, IL

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

That's for the 2.5L 924S. Completely different engine.

I would think some sort of extra fuel enrichment would be necessary when you hit the button (although, not the 5th injector, unless you want two rich cylinders and two lean ones...).

nick

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

You'd have to use extra injector, and in order to get proper amount of fuel out of it, you'll need to use extra fuel pressure regulator with it. Not an easy task, but doable.

And BTW, installing a nitrous on 924 2.0 NA is a one of the easiest (and efficient) ways to get better performance out of it

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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
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plyhammer · Posted: Wed Oct 12, 2005 10:04 pm Post subject: info

Sound like someone has some information. I would love to here part numbers and things that might make this a lot easier for me. Thanks

Porsche924boy · Joined: 25 Mar 2005 Posts: 252 Location: Ohio

I'm like you a dry NOS would be fun but i've been told that you have to do a engine rebuild. Or is the engine rebuild only when using wet. I also herd the DRY nos hooks up to your air intake.
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Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

EVERY nitrous system is installed to the intake tract, wet or dry.
I don't have any part numbers, it's easier to find some injectors and stuff at the local junkyard.
What about fuel pressure ragulator, it can be as simple or as complicated as you want it to be, important thing is that the injector needs to be tuned to run properly with nitrous shot and it has to be done at least with wideband lambda. And of course, all this nitrous thing means that your engine is in decent condition and oil pressure, compressions etc are fine. Otherwise you won't driving at all soon.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

OK, let's work with the basic concepts here.

NO2 is used because it has more oxygen in it than the normal air that we breath. Adding just nitrous to the engine will cause it to run lean, because the CIS sees volume of air, not molecular density of air.

So you have to add more fuel, and this is where it becomes challenging. The stock CIS is only really capable of increasing fuel by increasing the pressure, which would require a solenoid switched adjustable fuel pressure regulator, which would be challenging to say the least.

A wet kit is the obvious choice. I would "tee" into the cold injector line, which should always be pressurized, and use that to fuel the fuel solenoid. I would then make a bung for the nitrous injector to fit into on the plastic intake pipe just before the throttle body, glue it on, and go with that. An arming switch to power the circuit and the relay powered off the WOT switch, and you're ready to go.

You won't be able to use all that much nitrous in the 924 engine compared to modern EFI 4 cylinders, due to the poor combustion chamber design.
_________________
'81 931 in various states of assembly

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

Cbass, I was actually referring to the 5th (no, 6th

)injector, that is controlled by independant fuel pressure regulator.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

The 5th/cold start injector is great to shoot a little extra fuel for starting, but you want to trust that it will feed all four runners equally at WOT and redline??? Especially given its location off the side of the intake by #4? Sounds like asking for trouble.

nick

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Oh god no, not in it's stock position. Put one before the throttle body, tee'd off the same line. The advantage here is you could power the CSI directly without need for a seperate solenoid, much cheaper than a wet setup. Put the nozzle into a bung in the plastic air intake pipe, and feed the CSI into the same location to ensure you get a nice mix of the gas and the fuel.

Our cold start valves are a favourite for use as additional injectors in other vehicles. I'll ask the dodge guys how much extra fuel one of these puppies sprays.

Naturally, the optimum setup for nitrous would be port injection in all four runners, it would guarantee minimum expansion of the gas, keep it nice and cold, ensure 100% equal distribution, etc. Also optimum would be to use wet naawwzzles(terrible pun), but my concept is cheaper by far.
_________________
'81 931 in various states of assembly