Learn me - drag racing technique with nitrous

Well it looks like we found a nitrous kit in budget.  I've never driven a car with nitrous before, nor do I have much drag racing experience. I did a couple of google searches and learned to "spray out of the hole" from honda forums...

So, 3100 ish lb car with driver, RWD, drag slicks (older), ford 302, 3 speed manual, LSD, 100/125/150 shot of wet nitrous (plate system). Mechanical secondary carb (I think 650 cfm), msd ignition box. What do we do? Obviously the goal is the shortest ET. Driving technique is my biggest question, but also curious about changing plugs, using a throttle pedal nitrous switch, burnouts, etc. If it seems like I know nothing that's because your intuition is correct. 

also, I tagged nitro strength in this thread because nitrous wasn't an option but nitro strength was. I don't even know what nitro strength is but it sounds awesome. 

“Nitro Strength boosts up the vitality level in body and also supports stamina. Nitro Strength improves the all exercise execution for the instant muscle development in the body. Nitro Strength overcomes the muscle's weakness and make them strong.” - google

In reply to Andy Neuman :

Is that supposed to be like a fortune cookie where it gets better if you put "in bed" at the end?

Waaaay back in the '90s I was drag racing a 5.0 Mustang, and though I mostly ran brackets, I had an N2O system on it for some fun passes.

Most of the electronic controls available today were not around then.  I ran an MSD ignition box so I could run their retard box, activated with the N2O (also had a two-step).  I don't remember specifically how much I was retarding it.  The N2O was wired with a micro switch on the throttle and a button on the wheel, in series, so both were required for gas to flow.  The arming switch was separate.

Most of the time, the track wouldn't handle spraying in first, so I'd hit it 2nd.  It still shocked the tires pretty good, and sometimes I'd get wheelspin in 2nd and 3rd.  At 3000lbs race weight, a "100 shot" usually got me ~ 11 mph.  If you can use one of the newer controllers that allows a progressive 'hit', I'd highly recommend it.

Remember, if you 'pedal' the car, N2O shuts off.  If you forget to release the button, when you go full throttle again it's back on, and will likely spin.  It takes a little practice... 

needs more thunder muscle

Simulator experience tells me to start spraying as soon as you think doing so wouldn't cause the car to break traction.

Im learning from this thread as well.

Also, the amc likely has cast pistons. Dont detonate it. I think you have to retard timing and knock the plug gap narrower is what i always read in car craft.

Its a 750 double pumper on there as well if i remember right. 

back when i looked into spraying a SBC, iirc the ignition timing rule-of-thumb was to take away 2 degrees of advance for every 50hp of nitrous, so a 150 shot would require pulling 6 degrees out.    plugs should be 1 or 2 heat ranges colder.   i'd bet that hot rod magazine has probably published a beginner's guide to nitrous at some point.

Spray till the tires won't take it, then back off a bit.  That usually involves either a timer, or a gearshift sensor, so you don't spray for a half second, or you don't spray in first gear, or whatever suits your combination.

Lots of good advice here, especially the switches in series. Since I drive to the track, and often autocross, I physically unplug the solenoid power from the relay when not in use. A toggle switch would also work for that, but it has to handle the higher (20+) amps of both solenoids. The relay signal wire has a dashboard toggle switch in series with a momentary switch. I used the windshield washer spray lever as my momentary switch because Challenge budget. So instead of cleaning the windshield, I clean up the track of my opponent. I would like to put a pedal switch in series as well, but so far this works. 

Other things I've learned in my own research:

• Don't install the nitrous kit until you have a wide-band installed. You will be tempted to spray before knowing how lean you are.
• Don't spray at too low an RPM. Nitrous power (or torque?) is a function of time (steady flow rates of fuel and nitrous) NOT a function of engine speed. This means at lower speed, you are cramming in a higher volume of fuel+nitrous in the chamber than at high speed. This can kill rods or crack pistons. This is also what makes nitrous amazing compared to a turbo. No spool, all the power all the time.
• Start small. There's a guy on eBay who sells jets like $5 a pop. Order $100 worth and use the 2 you settle on for the Challenge. Use an online calculator based on your fuel pressure. Start with 50, spray in 2nd gear, see how that feels. 
• Jet rich, then lean up. Shoot for no leaner than 12.5. Lean = hot = hole in a piston. A rich shot is still more power than not spraying.
• Make sure your fuel pump is reliable. If fuel pressure drops while spraying, you just went lean at 100+hp over your original max hp.
• Keep the nitrous line clean. When the bottle isn't hooked up, keep tape or plugs over any openings. Or use a nitrous filter. Small debris can keep the nitrous solenoid stuck open, which means you're still spraying nitrous when you let off, but not fuel. This means lean + unintentional acceleration.
• Do NOT heat your bottle with a blow torch!!! It weakens the bottle structure and is also just stupid and forbidden at pretty much every track.
• SFI jacket required. Get the pants too while you're at it.

So, driving a pass will be something like this:

1. Pull into the burnout box. Do burnout (this is already sort of outside my comfort zone in an official setting).

2. Pull up to the line. 

3. Arm nitrous system. Ensure 1st gear in selected.

4. Go! Likely no nitrous since 3k to 5.5k rpm will go really fast in 1st gear, and traction issues mentioned as well.

5. Shift to second.

6. Activate nitrous with steering wheel button and WOT switch.

7. Shift to 3rd (hold down nitrous button since the WOT switch should take care of stopping flow during shift?)

8. Win?

In reply to Robbie :

Can't win if you're not powershifting WOT. 

Stampie said:

In reply to Robbie :

Can't win if you're not powershifting WOT. 

Honestly, thats my concern with running a wide open switch only. Im getting good at powershifting at WFO.

Don't forget:

0. Open bottle valve

My first run I didn't even spray until 3rd or 4th gear, just to see what it would feel like. Then the next run I sprayed once in 2nd, then lifted for each shift (automatic). The next run I held it from 2nd to the end. I think I can do 1st gear next time because my tires friggin hook.

I'm following along on this too. I have NO experience, but I've been reading. A recent search turned up the same advice as AngryCorvair posted: 2 degrees per 50hp and plugs 1 - 2 degrees colder.

My car (5-speed 'Tiptronic'), shifting at redline, drops about 2,000 rpm going to the next gear. My guess is that as I pass about 3.5k rpm in second, I can start and keep it spraying with a WOT switch. How's the gearing on the 3 speed manual? -How low is 1st, how much rpm drop between gears? (not that I'd have advice with those numbers, but that's what I'd be considering.)

One of my favorite quotes:

"When i first started thinking about nitrous on my capri i talked to an old guy at the dragstrip about how to tune for it. His recomendation was keep going up a jet until something broke. Then go back down a jet with the new motor."

With my Bosch Motronic EFI I don't think I can change the timing. Would changing fuel make a difference?

Robbie said:

So, driving a pass will be something like this:

1. Pull into the burnout box. Do burnout (this is already sort of outside my comfort zone in an official setting).

2. Pull up to the line. 

3. Arm nitrous system. Ensure 1st gear in selected.

4. Go! Likely no nitrous since 3k to 5.5k rpm will go really fast in 1st gear, and traction issues mentioned as well.

5. Shift to second.

6. Activate nitrous with steering wheel button and WOT switch.

7. Shift to 3rd (hold down nitrous button since the WOT switch should take care of stopping flow during shift?)

8. Win?

That pretty much covers it, plus opening the valve, as noted... 

If you're not running skinnies on the front, and slicks on the back, drive around the water and back in to do your burnout.  Everyone behind you will thank you.

I would suggest lift throttle shifting until you get the hang of how it all works together.  The small amount gained in powershifting is far less than the N2O gains...

Gearing - if we shift at 5800, we come back at 3300-3400. 26.2 inch tire may not be exact but should give close enough MPH for our purposes. 3900 to 5800 is the approximated powerband of the motor. (loosely approximated). 

WOT switches are great ideas and rpm window switches are excellent.  I don’t use either because old school.  

Patrick said:

WOT switches are great ideas and rpm window switches are excellent.  I don’t use either because old school.  

*cough*

AAZCD said:

With my Bosch Motronic EFI I don't think I can change the timing. Would changing fuel make a difference?

 

One racer/bullder (and I can't remember who) gave away a little secret when he said that almost everyone doesn't retard timing enough with nitrous.  Just because it's not breaking doesn't mean you aren't overadvanced.

Knurled. said:

Patrick said:

WOT switches are great ideas and rpm window switches are excellent.  I don’t use either because old school.  

 

*cough*

For reference, yes my 54 belair has nitrous

Patrick said:

Knurled. said:

Patrick said:

WOT switches are great ideas and rpm window switches are excellent.  I don’t use either because old school.  

 

*cough*

 

 

 

For reference, yes my 54 belair has nitrous

You're my hero 

In reply to Patrick, Dusterbd13-michael :

I kick it old school because I'm an old fool.

Woop, there's my exhaust valves

(Was it an exhaust valve or a piston that died because of the lack of a WOT switch?  I need to be precise in my ribbing)

Exhaust valve, and i needed that kick in the pants to put the 799 heads and ls6 cam in.  I would have used a wot switch on it if i wasn’t at $2016.xx that year.  I really should use them but i am stubborn

+1 internets for Tag Team reference

In reply to Patrick :

So ideally you'd recommend a WOT switch AND a momentary button on the wheel or shifter? 

Sounds like you were only using a momentary?

I'm sort of wondering if a WOT switch is sufficient by itself...