Nitro scramble button setup

[johnnydmd]

Way back when I first started my first nitro drag car setup, I had thought about adding nitrous to it, and was (correctly) talked out of it. While they "sort of" work (and you'll hear a lot of passionate, varied opinions on that), the implementation really isn't useful, IMO. Back in the day, Nitrous Express came out with an RC nitrous system. It was very similar in design to the 1:1 system they sold. It used a mechanical switch to release the nitrous into the carb when the throttle was open past a certain point. Then RB Innovations came out with one that was nearly identical and just as poorly implemented if not worse. This design was really good for one thing - ruining your engine. Now I have seen a number of videos, that do show it "working" and creating a lot of power, the tradeoff isn't worth it. Better to use higher nitro content fuel, or a bigger engine.

But what about a system that is controlled by a button on the remote, aka, a "Scramble button"? Something that was toggled on/off for a split second or so at the end of a run. Same lean-out conditions would be there of course, so what about a "wet" system? You know, one that actually mixes fuel with the nitrous using a small fuel rail that pushes fuel into the mix? I was thinking about all of this not really for nitro engines, but for 4-stroke mini v-8's that are coming out, but I did wonder if it could also be useful for a nitro drag car.

So I got to researching needed parts, and designing after doing a good bit of research of the 1:1 designs:

When armed, there is fuel in the bulb and line running to the Y fitting on the nitrous line, and there is pressurized nitrous in the line running from the tank to the toggle valve. The fuel is held in due to the bulb being a 1-way valve itself, and not being forced into the exhaust line. When activated, the nitrous flows past the toggle valve along with fuel that is in the bulb that is being sucked as well as pushed by the exhaust pressure. The amount of fuel is regulated with a valve. At the end of the line going into the carb (air filter hose) is a needle (a repurposed HSN is ideal fit) to get a spray and regulate the final amount. This may cause a (very) brief moment where gas tank pressure is not 100%, but quickly reverts when the button is released.

Essentially this is used as a scramble button - you hit it for a half second or so and release to get a little extra on the top end. The amount of pressure and N02 being injected should not be a large amount, as that is likely to cause blow-by due to the design of nitro engines. We aren't looking to double the power here - it's a shot of extra, nothing more.

So, I got to building. I already had a bunch of the fittings and line, as well as clips for the connections that potentially could pop off under pressure.

I had nearly everything within a day ordered, and it quickly came together. The HSN was a perfect solution for the nitrous/fuel mixture, and threaded into filter hose securely, at a 90 degree angle to the air flow.

After I had it all together, I made sure there were no air leaks, and I tested the valve action from the radio. Then I ran the car with the system unfilled, and unarmed to make sure the car didn't act funky in any way. It ran just as before. Hooray!

The nitrous bottle is a refillable type as they don't make threaded minis of N02 for some reason. So I'm waiting on the adaptor to allow me to fill it from a nitrous bottle (which I have one of ). Once I have that in hand, I'll be able to see how the system is when the nitrous pressure is released into the line, and hopefully there isn't too much expansion of the lines (or lines popping off). I do have a remedy for the line expansion handy, if necessary, though.

The way to operate this would be a few steps:

1. Disconnect fuel bulb from exhaust line.
2. Close fuel regulator valve, then prime it with fuel. Reconnect.
3. Open fuel regulator valve to desired position. (Here I think I will change to a better valve at some point that has measurements).
4. Open nitrous regulator valve and bring pressure up to desired level. No clue yet what a good level will be, but that'll be the fun part I think.

Questions I still have:

1. How solid is the bulb's 1-way valve? Will nitrous pressure overwhelm it? (If so, maybe a better valve will be required).
2. Will the exhaust pressure + suction of passing N02 be enough to pull enough fuel for a good mix? I think so.

 

[luke66]

thats super dope.

 

[Jamr]

Mad Max style!

 

[9x19]

Nicely done!

Does the added performance overcome the added weight of the nitrous components?

 

[johnnydmd]

Nicely done!

Does the added performance overcome the added weight of the nitrous components?

That's another good question. I haven't weighed the parts yet. They aren't terribly heavy though - and the bulk of that is the tank/regulator, which I put on the front where it's badly needed. So, I'm thinking it should, but won't know for sure until I get to testing in a week or so when the filler adapter arrives.

 

[Doom!]

I seriously don't know how you keep all of this stuff straight, very cool, and very confusing for an electric guy.

 

[luke66]

I seriously don't know how you keep all of this stuff straight, very cool, and very confusing for an electric guy.

i have to say, nitro cars look like way too much fun, but way too hard to use!

 

[Greywolf74]

Thats awesome!

 

[johnnydmd]

Well I had a 3 day weekend, and I learned a lot. I must say, a lot of hilarity was involved

First, on the pressure side, well, you cannot use nitro line! It blew up like balloons. Ditto for the fuel bulb. So I inserted them into 1/4 inch rib tubing, creating somewhat proper pressure lines. I also used zipties as clamps to the fittings. For simplicity's sake I removed the "wet" portion of the system and just kept it as a dry system. It actually "kinda" worked at this point, but it was not holding pressure well in the system. I'd put it to around 70 psi, and it would drop down to 30 pretty quickly. A quick test in a bowl of water showed many leaks.

So, I got to thinking that I could pick up some actual proper pressure line for airbrushes, as well as metal clamps that would really keep things tight. To fit on the connectors, I inserted some nitro fuel line inside the ends. I also grabbed a shrader valve I had laying around and modified it so that I could slip the pressure line over the end and clamp it tight. This fixed the problem of the regulator leaking using a non-valve fitting (it's designed for shrader valves to begin with). The setup now was very simple looking, and was airtight:

Oh, I also got my charger adaptor, but of course had to find a fitting to make it work with the nitrous bottle.

This in and of itself was a project, as I had to use a 4mm steel tube to act as a depressor through the fitting. It did work though!

I tested it out, and I was able to boost it to 100 PSI without issue. It would drop to about 85 PSI as the tubing expanded a bit but would then hold there steadily for well over 10 minutes. So, this system really works quite differently than the others where it's just opening the bottle and shooting nitrous through a restrictor valve. As I built this system, I soon realized why those were designed that way. One, they were made for general nitro racing, not specifically drag racing, and not "one shot". Two, the reason for the external 9V battery is because it requires a lot of power to fire a solenoid that could move with a lot of pressure resistance. The way this system is designed, is that after you charge the little bottle and hook it up, you then use the regulator to (carefully) charge the pressure lines with the desired PSI and then close it. The system is then in its "armed" state. Then when you hit the scramble button on the controller, the solenoid at the end of the pressure line opens, and the N02 releases into the outbound lines, through the restrictor valve and into the carb. So, basically, it's "one shot". Maybe that's not ideal, I am not sure. But, what it does allow is for fine tuning the shot in ways you cannot with the other systems.

Note - Replaced the carb needle I was using to meter the output with a control valve as the needle wouldn't properly seat tight enough to prevent air from leaking around the inlet. I'm sure I could have figured something out there, but it was easier just to use one of the control valves I had handy and replace the needle with a standard threaded nitro fuel nipple.

The control valve on the output line can be set to control the length of the boost, which can be anywhere from instant to about 1.75 seconds. I have it currently set at 1.5 seconds. The amount of boost in that time frame can be controlled by the PSI you set (increasing it will slightly increase the length too, but not too much from my testing of it). I have found that I can go up to about 95 PSI before the solenoid won't open due to the limited amount of voltage the receiver can supply. That seems like plenty though. I think at 1.75 seconds I have plenty of time to use it from the 30-50 ft mark and it follow through to the finish line.

I plan to first test this as a dry system. My thought is that it's not nearly enough air to cause a lean-out. However, if it does, I can surely put the fuel bulb in the output line with a little fuel in there and the N20 will push it through and mix with it. Probably best to put it before the restrictor valve, but I'd have to test that as it might cause the bulb to inflate too much. We got some 50 degree days coming this weekend, so I should have an opportunity to do some real-world testing.

 

[Doom!]

Great write up, again this stuff is so far beyond me.

 

[johnnydmd]

Catching a weather break this week with a day or two in the low 60's, so I might have a little time to at least run the thing and see if it leans out. I already have the contingency parts on order. Rather than a fuel bulb which surely would inflate, I found a decently large, clear fuel filter that would work. I already have an airplane refueling valve so I could very easily prime it with that.

I'm thinking the proper amount, if needed at all, might be to fill it half. Having it before the regulator valve will cause it to mix with the N02 as it is pushed through the squeezdown and misted.

 

[Greywolf74]

You always build the coolest stuff. I think I have penis envy

 

[9x19]

Don't envy your penis...

Nicely done, and can't wait for the track report.

 

[johnnydmd]

Was able to do a little bit of testing at long last

It wasn't warm enough for a true, full pass, but I did do some 50-70 ft stuff, at about 58 degrees last week. I typically refuse to do full passes under 60, simply because I like my car and don't want to cartwheel it when the rear tires break loose in that chilly air.

Verdict is mostly in: It works! There was no lean-out whatsoever, the plug was intact after about six or seven hits, engine temps were fine. (I really don't think a 1-2 second burst is nearly enough to hurt anything honestly). Power gain was significant. Almost felt like it shifted into second gear when I'd hit the nitrous. The only issue I felt needed to be addressed was that the output line is full of air on the first application of NO2 and would get pushed into the carb. The solution was to "clear" the line by hitting the nitrous a little before doing the hit. I don't know how effective that really was, not sure if the NO2 would leak out and be replaced by air or be sucked out by the air passing through the carb inlet for that matter. So, my solution to that last little piece was to replace the fuel nipple that is mounted in the air filter elbow with a one-way check valve. So even if the nitrous would get sucked out, air wouldn't be able to backflow into the tube. This ensures that the nitrous hit is pure nitrous, with no air getting pushed in ahead of it.

I've also found a better flow control valve for the output line than the plastic turn-screw one. Hopefully it works better than the metal lever ones I tried from aquarium lines (leaked like hell). It's for nitro fuel, so I'm thinking it should be airtight.

 

[Chubaka]

Very interesting. I always wanted a mini nitrous purge system.

 

[johnnydmd]

While looking for some fittings, I stumbled across something that changes a lot of the design - pneumatic tubing/fittings kit for dental equipment, in 4mm OD size. Total game changer.

Much cleaner, lighter, and has zero swelling/expansion when charging the pressure lines. This presented a problem in that the amount of NO2 in the pressure lines was very small in comparison the big 8mm ID air hose, so ultimately, I would need to add in an expansion tank. I couldn't find anything small enough to work here, so I decided I'd make one using some of the fittings that came with my kit, a 1/2-inch ID PVC riser and end caps.

The center of the tank (the PVC riser fitting) comes today. I also ordered some 3/4-inch ones too, just to try out and see what works better. The tank is 2 inches long in either case, so not very large or heavy. I'll give it a cool paint job too

This will allow for a much larger bank of NO2, meaning I could probably get several full pass hits before having to recharge the system from the metal cartridge.

So why not just have the regulator on the cartridge open all the time and pressurize the system that way you ask? Couple of reasons.

1. The system would not stop charging until it reached the pressure that's in the cartridge. I can't say for sure what the PSI is generally, but it's very high, and far too much for the little 6v solenoid to open (really, it's limited to about 100 PSI). So, it has to be carefully controlled and measured, something that isn't even possible to do when charging the cartridge with NO2.

2. The regulators aren't exactly the most airtight things ever. These are designed for quick bursts to fill up bicycle tires, so it's very necessary to use a Shrader valve to block off the regulator from the pressure lines going to the solenoid.

3. This gives complete and precise control of the boost PSI going into the engine.

My little aluminum flow valve arrived to, and I gave it a little test. It worked well, but I think I'm going to use that as the purge valve instead, because I found some ultra precise valves that are made for the dental lines that will work way better.

 

[Jamr]

I'm still not sure what the hell this is for....lol.
Looks cool though.

 

[johnnydmd]

I'm still not sure what the hell this is for....lol.
Looks cool though.

It's an "on demand" nitrous oxide system for a nitro engine. Huge power adder at the expense of a shorter engine life generally

 

[johnnydmd]

Finished the system this weekend. Had beautiful weather on Saturday for testing, but I was short one (major) part, and didn't finish until last night. Next week looks like we have a chance for some near 60 deg temps on Saturday, so maybe then.

I did adjust the valves and test the duration. I got about 4 seconds of boost in total, without about 3 of those being strong. That's more than enough and gives me a lot of room to adjust the flow.

The system is actually very lightweight, aside from the metal cartridge and regulator. The cool thing is once you've used that to charge the expansion tank, you can take it off to save weight, as the system cannot backflow because of the Shrader valve.

 

[Doom!]

Finished the system this weekend. Had beautiful weather on Saturday for testing, but I was short one (major) part, and didn't finish until last night. Next week looks like we have a chance for some near 60 deg temps on Saturday, so maybe then.

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I did adjust the valves and test the duration. I got about 4 seconds of boost in total, without about 3 of those being strong. That's more than enough and gives me a lot of room to adjust the flow.

The system is actually very lightweight, aside from the metal cartridge and regulator. The cool thing is once you've used that to charge the expansion tank, you can take it off to save weight, as the system cannot backflow because of the Shrader valve.

Are you activating it on the starting line or is it on a radio switch?