Learn me - drag racing technique with nitrous

Robbie said:

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...

I recommend WOT + momentary in series. WOT for safety (since you're not running a fancy ECU that can prevent the nitrous from spraying outside of safe rev/load ranges) and momentary for control (since you don't want it to spray during shifts or before you have the traction to spare, or again, at low revs).

In reply to GameboyRMH :

What Richard said.  WOT switch only says you get spray immediately.  I would do momentary + WOT or rpm window + WOT.  I prefer momentary because sometimes you need to back off or you can hit it when you feel safely hooked.  

The only time i sprayed off the line I exploded my axles.  The new car shouldn’t have that weak link

A lot will depend on how much traction you have available. If you think you want to spray late in 1st, then the momentary works well. Otherwise rpm windowing works better as it will just work for you, and be consistent.

Agreed on timing pull 2deg per 50hp assuming you don't change fuels, a little octane goes a long way. 

Get cheap spark plugs and read them. Lots of them. For every 50 over 50 go one colder (ex 100 shot, one heat range colder).

Not sure what you have for fuel but if EFI using a second regulator to get low pressure will give you more window to tune on smaller shots. Jet sizes at high fuel pressure make big changes. 

Make sure only the pistons that make it are in the budget. 

My personal rule of thumb is you can make 2x stock power on cast pistons if tuning is good, less if it's got flimsy rods (Honda, etc). 

We had good success with the WOT TPS switch + $.59 1st gear lockout. Basically a little piece of wire hooked to the shifter with a male headphone jack on the end plugged into a female on the dash. The pull to second arms the nitrous and you’re off to the races. 

Fumbling with buttons & switches & E36 M3 does not sound fun to me.

I would suggest a button instead of a WOT switch if the car pulls the front tires too high or if traction is marginal. With a WOT switch it's an instant on/off of a lot of torque with no ability to modulate. If you use a button you can keep spraying while using the throttle to modulate. Much much better results.

Too lean doesn't kill nitrous engines, but too much timing will. Basically if you optimize your timing for a rich mixture and then something happens to lean that mixture out, you end up with too much timing for the lean mixture which then leads to engine damage. I would lock out timing and use a retard box if you can fit that into the budget. Without a retard control of some sort you will be forced to pull timing even when the nitrous isn't spraying, which will cost you NA power in 1st gear if you start spraying in 2nd.

Another problem with a manual trans nitrous car is the fact that you will need to have enough clutch to handle the torque with nitrous flowing, which will be too much clutch for a proper drag launch, especially if you are launching without the nitrous. You can try to modulate the clutch hit with your foot, but be warned the results will not be pretty. You will get far better results if you rig up something similar to my ClutchTamer device, here's a link to it's website... http://clutchtamer.com . With something like the 'tamer in place you can raise launch rpm up much higher, also be able to launch with the nitrous on a 1sec delay timer. Far more effective than waiting until 2nd to spray. The 1sec delay basically serves to give the car some time to transfer weight before you hit the tires with nitrous torque.

Here's a link to a well done youtube video of a NA Coyote swap car using the 'tamer... https://www.youtube.com/watch?reload=9&v=yuZcEyl_vAE

Grant

In reply to poopshovel again :

That's really smart. We have a 'dogleg' box (hahahaha no it's just an old 3 speed) where first is back and second forward, but we could do the same thing.

In reply to weedburner :

Interesting! 

However if "pulling the front wheels too high" becomes one of our issues, I will be very happy.

I do have a motorcycle steering damper that is probably less than $5 budget hit. Might be a neat way to use it; to soften clutch engagement.

I did learn today that our kit didn't come with the original wot microswitch but did come with a momentary button as the person we got it from was using it in momentary only configuration. So even though switches are cheap that might sway our decision.

In reply to Robbie :

I wouldn't want to run a nitroused anything through any 3 speed, unless changing transmissions in the pits is one of your hobbies.

That three speed needs to be put out of it's misery. 

So, 175 shot 

My thought on the WOT switch is to wire it in series with a momentary switch. Both have to be closed in order to spray. Momentary gives control over when it initiates and gives you the ability to cut it off/modulate while you are still at WOT. WOT switch because if you aren't flooring it, you don't need to be spraying. Does that make sense?

WOT switch in series just isn't a good way to modulate power, especially if you are trying to walk the fine line between bog and spin.

Let's say you have a 150 shot that you are trying to "modulate". Say you launch the car at 5500, the clutch is probably going to pull the engine down to around 3500 or so if it doesn't spin first. At 3500, that 150 shot represents an additional 225ftlbs of torque that turns "on" or "off" with the WOT switch. Say your 302 makes 375ftlbs thru the throttle body, adding 225ftlbs thru a WOT switch means you are switching back and forth between either 375ftlbs or 600ftlbs of torque at the input shaft. Not really a good plan to walk the line between bogging and spinning, and a good reason to wait until 2nd gear to spray.

If you use a button you are able to keep that 225ftlbs of nitrous flowing constantly, while modulating the portion of the torque that's infinitely variable between zero and 375ft/lb via the throttle body. Instead of binary switching between 375 or 600 with a WOT switch, the button gives you the ability to vary torque anywhere between 225 to 600ftlbs using your foot. You will be able to easily spray 1st gear without blowing the tires off.

Just be sure to add a window switch, as it will protect the engine from spraying at too low of an rpm, also sets an upper spray limit that makes WOT shifts safer for the engine.

Grant

Subscribing so I can find it faster.

Go big or go home or just don’t oil down the track until last last call. 

Andy Neuman said:

Go big or go home or just don’t oil down the track until last last call. 

Well, I agree on both counts. Unless I'm racing next to you, of course.