Hopefully n2oMike will be replying soon. He has a wealth of knowledge on this subject and isn't afraid to share it.

You may also want to do a search in this forum for "nitrous".

Erik

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1966 Ford Mustang 2+2
Mine - Restomod in Progress

My ignition is a Unilite with a Mallory high output coil. I just installed it but it is okay if it needs to go. I just have a Holley mechanical fuel pump, not anything special.

Mostly geared to a carb system, but applies to all.... Here Goes!!!

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Now that we've got the juice, how do we have fun with it?

Well first off, you don't want to get anxious and hurt your
engine... Once the system is properly installed, check to
be sure its fuel enrichment is working properly. Turn the
nitrous bottle off, arm the system, and with the revs around
3000 rpm, tap the button. The engine should fall on it's
face. It should be about like hitting a kill button.

Now that we know it works (the engine is getting enrichment fuel).
Let's see what other items are necessary...

-COLDER spark plugs! Do NOT use Split Fires! For the street,
use the coldest non racing plug you can find... especially
if you might have to use the system with pump gas.

-A bottle heater and pressure gauge! You MUST know what your
bottle pressure is to get consistent results! The gauge tells
you the pressure, the heater allows you to control it. Keep it
around 900 psi for best performance.

-Fuel... Use the BEST you can find! Detonation on nitrous can
lead to some VERY un-pretty things! Straight pump gas should
not be used on systems over 125hp on a 302. These engines with
their 10 7/16" head bolts are prime game for blown head gaskets
if everything isn't right. A little detonation goes a loong way
on these motors...

Make sure you have a good ignition system with good wires.

**** Now that you are set up, how is it tuned???????? ****

First is timing. The timing NEEDS to be retarded about 3
degrees for every 50hp of nitrous boost. If you don't, it's
bye-bye head gaskets, or worse! You need to go with the upper
end of this scale when pump gas is used (even if you add octane
booster). Just DO IT!!!!! I use MSD's Multi-Step Retard to
do this automatically anytime the nitrous is engaged.
If you are in the market for an ignition system, The MSD Digital 6 Plus
costs $279, has a timing retard, a two step rev limiter, plus
is adjusted by little dials. (instead of chips)

******** FUEL SYSTEM ********

To start, make SURE your fuel system is able to maintain
full fuel pressure at full throttle high rpm with the
nitrous engaged! It's better to be safe than sorry here.
I've seen cars break into the 10's with a single Mallory
140 or Holley Blue pump, but wouldn't really recommend it.
I use two Mallory 140's on my car. One for the engine, the
other for the nitrous.

******** FUEL PRESSURE ********

If the fuel pressure is too high, the car will exhale a bunch
of black smoke out the exhaust, and will not run anywhere near
its potential. It will feel very lazy (well, for nitrous).
We want to lean it out, just not toooo far.
My buddy's 2V 351C Mach I went from 9.00 to 8.50 in the 1/8,
just from lowering the fuel pressure!

Start with the smallest hp jets, with the fuel pressure turned
up extra high. This will ensure an extra margin of safety.
With the tranny in neutral (park), bring the revs up to 3000
and tap the button. The revs should jump up a bit. Probably
not super crisp or fast... just kind of a 'VROOOOM'. Do this
with the bottle pressure at its operating range. (850-950 psi)

If it hits EXTRA hard, like BAM! You are probably a bit lean,
and need to increase the fuel pressure.

We can now start to decrease the fuel pressure....
Do this with the car in neutral. Starting with the pressure
high, we are going to be tapping the button at 3000 rpm as we
gradually decrease the fuel pressure.

As the fuel pressure is lowered, the engine will start to respond with
increasing aggressiveness. The VROOOOOM will start to turn into
a BANG! When it BEGINS to get pretty crisp, it's time for a road test!

At full throttle around 3500 rpm, hit the button and hold it
for 3-4 seconds. The car should respond in a positive manner. :-)
As you let off the button, kill the engine, coast to a stop,
and check the plugs. They should look clean, but have NO specks
on the porcelain. If they do, it's aluminum from the pistons,
and the fuel pressure needs to be increased. Chances are, at
this point it will still be a little rich, and you will find no specks.

Decrease the fuel pressure a little at a time while making the
above test. As soon as you begin to see ANY specks on the plugs,
raise the fuel pressure a half pound or so, and you should be
close to optimum for that hp level. If you want to try other
jets, you need to go through this same testing procedure again.
Start rich, and work your way down.

You will be **AMAZED** at how much better a nitrous system works
once the fuel pressure has been optimized!

**** Other things that help optimize a nitrous equipped car ****

- A good exhaust. BIGGER is BETTER! 3" pipe and mandrel
bends rule in nitrous applications!

- Proper camshaft. A lobe separation around 110 deg is a
good compromise on a carbed street engine.
Some extra exhaust duration is also a plus.
8-12 extra degrees is good. To maximize
nitrous performance, go to 112. 114 on an
EFI car.

- Compression. Low compression makes tuning a lot more
forgiving. Make the same mistake with both
a high and low compression engine, and your
chances of living through it are MUCH better
with the lower compression.

If an engine is a little low on compression
anyway, (5.0 with a cam for example) nitrous
can bring in a SERIOUS wake-up call!

Good Luck, and HAVE FUN!!!!!

http://www.enhancedhealth.com/NOS2.htm

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'65 Fastback

Wiyh a 100 HP shot, what is the cost per race?
Do you use the nitrous all the way down the strip from start to finish?

Some folks are just plum ate up with dumbass!

Set on 100hp, you'll get around 100 seconds worth of 'fun' out of a bottle.

Yes, I engage the nitrous at the starting line. It makes the 60fts drop from from mid 1'6's off the bottle, to a best of 1.43 on it!

Good Luck!

------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220

quote:

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Originally posted by 65_289:
So are you bouncing off the rev limiter with the nitrous on? Does that hurt the engine?

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The nitrous is hooked up so it can be activated by either a throttle switch, or a button on the shifter. At the track, I use the throttle switch... so anytime the throttle hits the floor, the nitrous is activated!

When getting ready to launch, I'll bring the engine up on the 2-step around 6000 rpm at 3/4 throttle. (nitrous not on) When the light turns green, the clutch is released and the throttle gets buried. (nitrous turns on) After that, sh*t happens pretty quick! So the answer is, no, I don't have the nitrous activated with the car on the rev-limiter getting ready to take off.

But, from experience on the street with radials... (often go up in smoke, and let the engine free-rev on the bottle) Hitting the rev-limiter with the nitrous on can result in some MAJOR backfires! BAAAM! These are muffler busting SOB's! I blew apart two perfectly good stainless steel Edelbrock mufflers once like that. (these were the RPM mufflers that weren't fully welded. They were replaced with the fully welded 'race' series #5525, and no problems since) Of course there haven't been any major backfires since, either.

Good Luck!

That answers most of my questions and gives me a good idea of the nitrous "game."
I think it is a good way to go for what I plan on doing...AFTER I get some racing experience.

quote:

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Originally posted by n2oMike:
But, from experience on the street with radials... (often go up in smoke, and let the engine free-rev on the bottle) Hitting the rev-limiter with the nitrous on can result in some MAJOR backfires! [b]BAAAM! These are muffler busting SOB's! I blew apart two perfectly good stainless steel Edelbrock mufflers once like that. (these were the RPM mufflers that weren't fully welded. They were replaced with the fully welded 'race' series #5525, and no problems since) Of course there haven't been any major backfires since, either.

Good Luck!

[/B]

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I've heard about nitrous backfires. Scary stuff.

What about setting your rev limiter at say 6000, and setting the nitrous on a window switch to come on at 6200? That way, you could launch with the throttle buried, and not have to worry about the accelerator pump setup, and not worry about a nitrous backfire? The time it takes for the engine to go up 200 rpm would probably be no more than it takes to go WOT from 3/4, right?

I've got a way using two different relays to launch 100% wide open if I want.

It works fine for the time being.

quote:

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Originally posted by n2oMike:
The engine falls below 6k rpm on the shifts... so the nitrous would turn off. WE CAN'T HAVE THAT!

I've got a way using two different relays to launch 100% wide open if I want.

It works fine for the time being.

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That's a good point. I forgot about the rpm drop on shifting.

quote:

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Originally posted by 65_289:
That's a good point. I forgot about the rpm drop on shifting.

But if you were running a slush box that launched at say 3000, then a 3200 window switch would be ok, since you never drop below that in a run. Right? Off-base?

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Sure