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Previous Next Up Topic Off Topic / Rants and messages / Anyone run nitrous? (17551 hits)
By Jay H (X-20) (ManxVair CC) Date 2010-03-09 22:23
Just curious if anyone has run nitrous. I'm thinking about fitting a small shot to my Subaru powered buggy. Just curious if anyone has ever tried this or has any experience/words of wisdom about nitrous in general.... not necessarily on a buggy.

By LoCashJohn Date 2010-03-10 01:03
My buddy Lester and I ran nitrous on his Manx drag car.

First motor was an 1835, dual Dell 40's, semi-hemi heads with 40X35.5 valves, 1 5/8ths merged header and MSD ignition and I think the compression was around 8.5:1 .  With a "50 shot" (approx a 50 hp boost) it'd run a consistant 7.50 (7.501, 7.503, 7.500, etc) et in the 1/8th mile.  With a 75 shot it would run a consistant 7.20.

Then Lester built a 2275 and with the 50 shot it ran 6.70s.  At this point we started thinking about the safety of the pan based buggy and decided to build something different.

In the 6 or 7 years that combo was run we only had 1 failure that we attribute to ourselves.  Keep in mind that every pass was "on the spray" from the launch through the traps.

Here' my nickels worth of advice about nitrous, squeeze, spray, giggle gas or whatever you want to call it so long as you don't call is NAWSSS!!!!

If running a carbed motor, make sure you're fuel pump is up to the task.  Run 2 seperate pressure regulators; One for the carbs and one for the fuel solenoid.

Make damn sure you install a "hobbs switch" (pressure controlled electrical switch) in the fuel line that feeds the fuel solenoid.  Adjust it so it cuts power at a pressure level just below your operating pressure for you NOS fuel system.  Wire it so if fuel pressure drops it kills the nitrous system.

Use fogger nozzels with changeable jets not the much older stuff where the fuel and nitrous enter the manifolds at  two seperate points.

For drag racing/bracket racing consistancy add a purge solenoid on the nitrous side of the plumbing.  Make purging a regular part of the burnout and pre-stage routine.  Install a master ON/OFF switch in EASY reach of the driver.  Install the actual triger switch on the carb/throttle linkage.  Set it up so the switch triggers at 100% throttle (WFO)

About the above.  This will work on the street, but use caution.  With the system armed, when you floor it, stay in it.  If it scares you and you let off, stay off the gas pedal.  The worse thing you can do is floor it (nitrous triggers), foot suddenly comes off the gas even a little (nitrous shuts off), then you floor it again (nitrous triggers again).  This sequence of events can lead to a nasty nitrous backfire in the manifold.  

Wire your ignition system, start button so you can "dead roll" the motor before every start.  Here's why:  If the valve on the bottle is open (your at the track or just forgot and left it on) the only thing keeping nitrous from seeping into the intake manifold is the nitrous solenoid (remember the bottle is at approx 1,000lbs pressure).  Solenoids are prone to leaking so do not trust them.  When cranking the motor you want to roll the engine over for a few seconds WITHOUT the ignition system firing or injectors injecting.  This will clear the intake of any possible nitrous and eliminate any chance of a manifold explosion.  Then flip a switch to "normalize" the cranking process and fire it up.

If you have any specific questions feel free to ask.
<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Jeff GS Date 2010-03-10 12:41
Whew!  That's a great write-up John - but sure sounds easier to just run a bigger turbo and fuel injectors!  A lot to think about (getting all the sequencing right) every time you want to run a little juice.
By LoCashJohn Date 2010-03-10 14:55
In the end turbo charging is the way to go for most applications.  Nitrous is great for a detail concious guy who doesn't have tons of fabrication skills or tools.

Nitrous also works well WITH a turbo system.  In fact they go together like peanut butter and jelly.  A very small shot (say a 25) into a draw through carbed turbo system at full boost (maybe 22-26lbs) can see hp readings climb by as much as 70+.  The intake cooling benefit is mostly to thank.

Also a small shot can substantially increase torque at lower RPMs.  Here's how:  A turbo or blower or even a plain old carb depend on crank shaft speed (rotaional speed) to get fuel and oxidizer into the chamber.  If the throttle is wide open and the crank is spinning fast it can get a lot of fuel and oxidizer in to blow up and do work.

With a nitrous system, the flow rate of the added fuel and oxidizer is a constant.  In other words there is no throttle for the nitrous.  If the crank is spinning really fast as the system is spraying each cylinder only gets a little sip of spray.  BUT if the crank speed is low (like launching from the starting line) the flow rate is still the same BUT each cylinder gets a much bigger bite of the constantly flowing fuel and oxidizer.  The torque of the motor goes through the roof! 

That old 1835 leaving on just carbs would barely get out of it's own way.  Afterall it was just a mild street motor being used for racing.  But with a 75 shot it left like you were getting shot off the deck of a carrier.  Launching on spray and seeing the differeence in torque output is quit amazing.
<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Jay H (X-20) (ManxVair CC) Date 2010-03-11 02:16
Thanks for the info. I've done my homework and have a handle on everything you mentioned... except for the dead roll. I understand why you mention it though and want to thank you for bringing up another safety feature I haven't been able to read anywhere on the net during my research. Yet another reason why I like the DBA.

I am turbocharged with a stock turbo, and am looking for a little extra. While I thought about upgrading the turbo, i'm concerned about the increase in lag I might have if I went with a larger turbo. (I have experience in changing turbos on my SAAB SPG I modified)

While the turbo change was an option, I decided I might like to try the bottle in order to keep the smaller turbo and minimize lag.

By LoCashJohn Date 2010-03-11 03:18
You'll be very pleased with nitrous as the icing on your turbo cake.  It really sweetens the flavor.

What sort of driving are you planning on?
<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Brad H 1498 Date 2010-03-11 19:00
"You'll be very pleased with nitrous as the icing on your turbo cake.  It really sweetens the flavor.

What sort of driving are you planning on?"

Death grip on the steering wheel, foot to the floor, hair on fire kind I'm assuming LOL

Good info John. Good luck Jay....I think ;-) Remember, headlights forward, shiney side up

By Jay H (X-20) (ManxVair CC) Date 2010-03-11 21:42
I was hoping for airplane-launch-off-carier type driving. :-) The hair on fire would be a caveat to the experience! I took a buddy of mine on a ride in the buggy and it was hard for him to admit it...... I accelerated better in the buggy then his 600 H.P. Acura does at the track!

Although I've never dragged the buggy under the lights, I'm sure she would do well if I ever take the chance do run on the track.

I've got the water/methanol injection for cooling the intake charge due to the fact that I'm not running an intercooler. I figured Nitrous would help the air charge cooling a bit better.

By LoCashJohn Date 2010-03-11 22:33
I advise a single fogger nozzel aimed at the inlet of the turbo compressor housing.  Set the jetting for about a 25-50hp shot.  Since you're not drag racing don't worry about the purge feature.  The nitrous hit won't be quit as violent but that's ok.  Use a master switch you can reach easily and fab a triger switch on the throttle linkage.

When you floor it (with system armed) make sure you're pointed where you want to go.

There's a really good book on nitrous systems that can be found in many large speed shops.  I don't recall the title or publishing company but it shouldn't be hard to find.  Much of what it'll tell you I've already covered but it's still a great resource.
<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Brad H 1498 Date 2010-03-11 23:46

Just make sure that external engine parts don't accelerate faster than the car!  Please post some videos of your rocket Jay would love to see it in action.

By Jay H (X-20) (ManxVair CC) Date 2010-03-12 02:04
Hey Brad,
Thanks for that link. It shows how important it is to have the nitrous flow stop when you want it to stop. I have read that some people wire in dual nitrous solenoids IN SERIES will help ensure this sort of thing does not happen. Obviously, regular testing for operation is still needed, so you know if you have a failure of one or the other. It looks like I would want to order another nitrous solenoid. That there is an eye opener.

By LoCashJohn Date 2010-03-12 04:02
Keep in mind that cars like that are the extreme.  Some guys spray more than a 1,000hp worth of nitrous in multi-stage systems that'll nearly empty 2, 20 pound bottles in a single pass.  That's very different than a single nozzle set up.
<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Brad H 1498 Date 2010-03-12 14:15
Wasn't trying to put the fear of god into you or anyone about nitrous, just remembered this video. I also understand that this car purged the nitrous internally (into the intake) not into the atmosphere as most do. I don't think you'll be spraying a 1200 shot into your Subi. Are you going for a NO2 set up? or still just thinkin'? I'm considering a turbo for my bug when I get at that in a couple years.

By Jay H (X-20) (ManxVair CC) Date 2010-03-12 17:12
I took the plunge. Got a 10 lb cylinder, single spray nozzle set up for 75 shot, solenoids, remote bottle opener, low fuel press shut off switch, throttle switch, and other switches/wiring.

Got it used. Trying to find a filling location now! Doesn't look like its readily available here in western ma.

By LoCashJohn Date 2010-03-12 19:07
Check with your local mom n' pop type speed shops.  They usually do nitrous fills.

I've never used a remote bottle opener so I'd use caution.  Remember to wire the motor for a dead roll feature.

You'll also want to jet down from that 75 shot a little.

Also, with the large torque increase the spray gives your present clutch may not hold the power.  Listen for slippage the first time you hit it.

<a href="http://www.LoCashRacing.Org">http://www.LoCashRacing.Org</a>
More brains than bucks...
By Jay H (X-20) (ManxVair CC) Date 2010-03-12 21:35
I just got the KEP DUAL clutch set up on the stage II pressure plate. That is going in and the plan is to wire/plumb/install the nitrous at the same time. I'll keep everyone posted.

By Brad H 1498 Date 2010-03-12 22:51

You might want to think about some clutch engagement management to soften the hit at launch if you plan on any sidestepping action with spray or do you have a hydraulic clutch, seems to me you do ,but can't remember.

By Jay H (X-20) (ManxVair CC) Date 2010-03-13 01:31
I was thinking of going hydraulic with a stage III KEP pressure plate, but decided on staying with the Stage II and the dual discs instead. I've gotten real good at heal and toe and even better at holding the Hurst line lock on while I have my two feet to do as God intended, lift the clutch and smash the gas! LOL :-)

I don't plan on engaging the nitrous at low rpm or right off the line really. I'll be playing with it in the beginning (If I can ever find a place to fill). It's more for fun than anything else. :-)

I was thinking about using a DPST switch under an aircraft-style red guard. Up would arm the nitrous as well as switch Megasquirt maps to one with the retarded timing while down would de-energize the nitrous and switch back to the more advanced non-NO2 timing map.

That's the plan.... I still need to swap clutches, install the nitrous, copy maps and retard the timing for the "race map" and do some testing/tuning.


By Allison Daytona Ken Date 2010-03-13 02:53
By Jay H (X-20) (ManxVair CC) Date 2010-03-14 04:32
Ken, Did you go faster? :-)

By Allison Daytona Ken Date 2010-03-14 14:17
not really the coffee was weak.                  Ken.........
By Jay H (X-20) (ManxVair CC) Date 2010-03-19 10:59
Well, I was able to find a place to fill locally only about 10 min away! Got the bottle filled and started the install yesterday as  far as the engine is concerned. I got the fogger nozzle bung welded into the intake and fabricated a mount for the WOT microswitch. The Subaru engine has a little tang on the end of the throttle plate pivot rod that was perfect to actuate the switch. I just needed to fab the mount to hold the switch and I had the engine pulled for a clutch upgrade, so that was the time to do both projects.

I still need to mount the solenoids, fab a switch plate for the "Nitrous control center",  plumb, and wire it up. then its testing.

By Walter P 3290 Date 2012-07-03 07:25
It would actually be interesting to see how the whole thing would keep up though considering the lot of other concerns like how it is going to solve the entire issue of having it attached, I think that one of the major problems is how you are going to make it as effective as it could be.
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