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contraption22
04-19-2010, 04:47 PM
Quote:
Originally Posted by contraption22
Mike (ZIN),

To bring back an old thread,

Is there any way to make a dry shot work without completely re-engineering our fuel systems, short of a custom cal?

Sure, the trick is to keep the boost pressure consistent. In a non-cal application, you'll most commonly, need to boost the fuel pressure above "normal", this adds the extra fuel for the nitrous. The amount of HP/nitrous is limited by the amount of fuel you can get though boosting the pressure. 80-85PSI is pretty much the max you can go, though some have gone higher, I think it is a good compromise with safety and max HP.

You need to test to see what your maximum fuel pressure is when @ full boost, then we can see what kind of "overhead" we have for adding nitrous. I'd start small, something like a 28 jet.

This is small enough to potentially do something but small enough to ensure we can't hurt anything. At the same time, it gives us an idea as to how much fuel we have to work with.

The best way to tune is by spark-plug color/indications. But, that method of cutting the engine off clean, isn't too kind to turbos, so a wide-band O2 is the next best thing. 10.5-11:1 is typical for heavy nitrous/turbo applications, but I would expect this application would prefer something in the 11-12:1 range. And, I would still look at the plugs for any signs of detonation, which is more likely to hurt an engine than running lean...

Another way to get the needed fuel is to fool the computer into adding extra fuel by modifying the coolant temp sensor's signal into making the computer think it's -20* out.

The first way I mentioned is the easiest, as there is a kit made to do just this, the NOS 05115, made for 5.0L Fords, though it can be made to work on anything using a vacuum/boost referenced fuel pressure regulator.

The second method is how we did our Neon (05182nos) and the Viper kits (05180nos). They worked great, but are a little more involved, but not too much.

Interestingly, you could do both!! Of course, you'd need a top-notch fuel pump to do it!

If anyone would like to know more, feel free to PM me or we could start a new thread...

Mike

zin
04-19-2010, 06:53 PM
One thing I'll address right off the bat: Dry nitrous DOES NOT MEAN NO FUEL IS ADDED.

Sorry if I overemphasized, but the point is that many people misunderstand that a dry nitrous system is one where the fuel comes from the computer/injection and the nitrous is added alone into the intake ducting.

Properly burnt fuel is HP, nitrous alone is no more helpful than air alone.

That said, please feel free to ask any nitrous questions, I'm happy answer them. And I subscribe to the notion that the only stupid question is the one you don't ask.

Mike

contraption22
04-19-2010, 06:54 PM
So currently I am running 42psi base fuel pressure. At max boost, this would be 72psi. So generally I have about 13psi of room before I hit 85psi.

Previous to this week, I was running just at 85psi max fuel pressure, but I have since installed larger injectors for no other reason than to keep my max fuel pressure lower to keep my pump happy.

zin
04-19-2010, 07:15 PM
So currently I am running 42psi base fuel pressure. At max boost, this would be 72psi. So generally I have about 13psi of room before I hit 85psi.

Previous to this week, I was running just at 85psi max fuel pressure, but I have since installed larger injectors for no other reason than to keep my max fuel pressure lower to keep my pump happy.

If you are running a standard 1:1 fuel pressure regulator, then your max pressure won't change, as it is simply base pressure plus the boost, that is, unless you'll be lowering your base pressure. I'm guessing you had your base pressure higher to get more fuel from the injectors, and now will be bringing it back to a more "normal" base pressure...

Mike

contraption22
04-19-2010, 07:22 PM
I had it set at normal 55psi, using a cal tuned for 72lb injectors. I just swapped in 83lb injectors for the sole puropose of running lower base fuel pressure.

BTW.
Thanks so much for taking the time to answer my questions. You are always a huge help, mike.