2nd Generation Specific 1986-1992 Discussion

N.o.s

Old 05-19-2004, 07:48 AM
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How bad is a 50 shot of nos on a stock s5 ?

I can get a good deal and was just wonderin any help would be appreciative ?



Thanks Nick
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Old 05-19-2004, 09:14 AM
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Make sure you use a WET Setup and not a dry one. You stock fuel injectors are working very close to their limit and a Dry setup is asking them to work even more.



Get a Wet setup and upgrade your fuel pump. When you are picking the pills to put in for a 50 shot use a pill that is about 2 or 3 sizes bigger for the fuel. This will ensure your not going to lean out.



Also retard your timing about 1 or 2 degrees you can run a risk of detination if you dont.



You can also do a couple of N2O pulls and then pull your plugs make sure they are on the darker side.



IMHO - Once you install it go and do a dyno pull ($60-100) and make sure that she is not running lean. Then you'll know your safe and an added bonus is you'll know what your putting to the wheels. The 100 bux for a dyno pull is well worth it when you figure in how much an engine rebuild is.



I used to run a 50 shot in my 90GTU and it pulled pretty damn hard. You'll pick up 50 horse but the Torque will be much much more.
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Old 05-19-2004, 09:33 AM
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Dry setups are pretty hacked up to begin with (except when you have a standalone that does it right as opposed to a "pinch valve" setup).



Stock injectors are close to the limit? Well they are 44 lb/hr or so? This gives 176 lb/hr max, 80% (safe limit) of which is about 140 lb/hr. According to Racing Beat, BSFC of a street ported 6 port is .53-.55. I don't imagine a stocker is that far off from there. That gives a maximum of ~260 HP at 80%, which would seem that they aren't anywhere near max'd out.

But - the bolt on dry systems don't increase injector duration at all (at least the ones I've seen). They use the aforementioned "pinch valve" in the return line to increase pressure. Injector duty cycle does not change at all - it's fuel pressure. Injector flow increase as the square root of increase in fuel pressure, so you're asking alot from the fuel pump.

Besides that, the pinch valve setup can't possibly be as correctly tuned as a wet setup with a fuel jet.
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Old 05-19-2004, 10:58 AM
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Check this out from the FAQ section...



Click here!!!
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Old 05-19-2004, 11:48 AM
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Originally Posted by 83turbo' date='May 19 2004, 09:33 AM
Stock injectors are close to the limit?
Stock injectors on a 15 year old car are not up to the job. I should have said the stock Fuel system is not up for the task.



I have been debating dropping my Wet setup back into my TII as well that FAQ is making me want to do it sooner then later. I plan on installing a sperate fuel system just for my NOS.
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Old 05-19-2004, 02:30 PM
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There are a couple dry set-ups (expensive ones) that do claim to alter the injector duty cycle, but yes, most do run an FMU. All and FMU (fuel management unit) does is up the fuel pressure whenever the Nitrous system is used. The problem with this is that... 1. old injectors vary in their spray pattern and output volume due to gum and varnish buildup around the pintle. Not so much a big deal when running N/A, but adding forced induction to a poor spray pattern can result in Nitrous back fire, and adding nitrous to an incorrect injector volume can result in running lean under certain operationg conditions. This can be HELL to try and tune for, as the wideband takes the air fuel average of both rotors... so while one rotor runs rich, the other runs lean. While this can still occur running a wet system via the stock injectors, the wet system does its own fuel enrichment, and thus has much less of a chance of running lean, and a MUCH lesser chance of nitrous backfire.

That being said, I hate dry nitrous. The kits lack in tuning for me.



PS- when you typed NOS as n.o.s., I thought you meant New Old Stock.
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Old 05-19-2004, 04:18 PM
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Originally Posted by 83turbo' date='May 19 2004, 09:33 AM
Dry setups are pretty hacked up to begin with (except when you have a standalone that does it right as opposed to a "pinch valve" setup).



Stock injectors are close to the limit? Well they are 44 lb/hr or so? This gives 176 lb/hr max, 80% (safe limit) of which is about 140 lb/hr. According to Racing Beat, BSFC of a street ported 6 port is .53-.55. I don't imagine a stocker is that far off from there. That gives a maximum of ~260 HP at 80%, which would seem that they aren't anywhere near max'd out.

But - the bolt on dry systems don't increase injector duration at all (at least the ones I've seen). They use the aforementioned "pinch valve" in the return line to increase pressure. Injector duty cycle does not change at all - it's fuel pressure. Injector flow increase as the square root of increase in fuel pressure, so you're asking alot from the fuel pump.

Besides that, the pinch valve setup can't possibly be as correctly tuned as a wet setup with a fuel jet.
But the stock ecu doesn't push past 65% duty cycle, correct?
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Old 05-19-2004, 11:51 PM
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forum myth.
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Old 05-20-2004, 12:57 AM
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Originally Posted by scathcart' date='May 19 2004, 11:51 PM
forum myth.
So what is the max the stock ecu will push the injectors to?
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