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221 Posts
Discussion Starter · #1 ·
I just ordered a nitrous kit that I'll install and use at the upcoming All Ford day at the local NHRA track. I know about the rule now requiring an SFI jacket for nitroused cars, so I also ordered a jacket.

Are there any other things I need to be concerned about to pass tech inspection? The bottle will be trunk mounted, and I do have a rear firewall. Does the bottle still need to be vented? Any other gotchas to watch out for?


1,305 Posts
Yes, the bottle will need to be vented to the outside. That will require a blow off valve.
Thats about it...
One other thing... make sure you only have 12" (Total) of rubber fuel hose (and that includes the nitrous fuel line).


<font size=-1>[ This Message was edited by: Thordane65 on 5/31/06 4:11am ]</font>

7,497 Posts
If you don't get all those details taken care of, don't leave the bottle at home... as most places will allow you to run anyway. I haven't seen too many bottle vented to the outside. I've only had to wear a jacket one time. I don't have a battery disconnect switch, and I have no rear firewall. So far, I've not had a problem running anywhere. However, I do have a catch can, driveshaft loop, blowproof bellhousing, 6pt roll bar, racing seats and a 5pt harness. Usually, each track will have a few 'key' items they look for, then the rest will generally fall within the 'spirit' of the rulebook. The faster the car, the more strict they are with the rules.

Good Luck!

1,305 Posts
HAHA, Mike you said what I was thinking... I actually had typed more and deleted it... what happened to me was the night before the race, I had forgotten all about the blow-off.... so I simply took out the bottle and told the tech guy I was running without it... then in the pits I installed the bottle. Unethical of course... but I was faster

1,950 Posts
The vent only needs to be connected to the outside if the bottle is in the same compartment as the driver. You must have a 'wall' (factory seat/bracing/etc...) to qualify as a separate compartment.

221 Posts
Discussion Starter · #6 ·
Thanks for the feedback, guys. As always, it's appreciated.

I do have a 22ga firewall installed where the rear seat used to be, so it sounds like I can avoid having it vented. I'll find out more when they tech it next month.

7,497 Posts
As for tuning...

Here ya go...

Before you start, make sure to have a bottle heater and pressure
gauge, along with a fuel pressure gauge and regulator for the nitrous
enrichment. A good ignition system is also mandatory... one that
doesn't keep advancing the timing to the moon as the engine revs.
It should STOP at around 36 degrees total. (with the nitrous off)
Check it!!!!!! Wild advance KILLS nitroused engines...
Factory distributors are really bad about this.

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


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!!!!!

847 Posts
You guys are lucky I got screwed at out local track with my nos. I new they were wrong but what can U do?. They made me have vent and fire wall with bottle in trunk. Now they have a new tech guy (probably cant afford his own car) bitching because my harness is out of date by one year but my car can run with stock 66 lap belts dosent make any sence.
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