NITROUS OXIDE ( nos / n2o ) advice forum

Hi there, this is my first posting and although familiar with two and four stroke engines, I've had no experience with Nitrous Oxide.

I run a small race boat of a catamaran design, (look up zapcats/thundercats). It has a 50hp 700cc three cylinder, two stroke engine. At around 4500-5000 rpm it's good for 50mph. It's an under stressed unit as it's originaly designed for much bigger boats so does not have to work hard to push around a boat that four people can carry.

There are relatively few tuning options for the engine as they are kept standard for racing to ensure fairness. I however, don't race so I'm looking at getting a small power increase.

The propeller has been heavily tuned already and gives good acceleration and top speed, (always a compromise on boats). It will happily deal with more rpm.

So what I'm interested in is increasing power by around 5-20% but only when the conditions allow.

The installed system needs to be simple, light and waterproof. I don't have a 12v supply so it would need to use a battery.

Any suggestions or advice? Could I use a bike kit for three cylinders or could I simply use a single injector into the airbox? Can a system deal with rough conditions and being rocked around?

Kind regards,
Steve.

You certainly wont have an issue with getting nitrous to the engine even if the boat is rocking to 45 degree's
But you will need to make sure the fuel feed cannot slug air when the boats a rockin' !!

You cant just put nitrous into the air box unless you have an engine management system to richen the fuel feed to the engine when running nitrous.

I'm sure Trev will be along soon to advise. But if you need a battery to power the system it may also need to power a separate fuel pump from a small stand alone tank I think. Unless you engine runs from an inboard tank that is?? If air slugging could be an issue with your fuel tank when the boat is rocking you should fit a fuel pressure cutout switch so the nitrous shuts down if fuel pressure drops, and I would make this switch have a manual reset function as well. You can do this by arming a latching relay via a pushbutton to arm the system. And have the coil feed to the latching relay run via the fuel pressure switch. Its simple relay logic which will kill the nitrous if the fuel pressure drops and will keep the nitrous off until you re arm the system manually. I know Trev has many 2 stroke customers so he will assist further.

regards
Perry

Thanks for the reply.

The boat does not really rock, it more sort of rears up and slams down hard. It's a rough ride.

The fuel pump is below the bottom carb and is diaphragm fed so i don't think fuel pressure would be an issue.

What ever I decide, it has to be simple. Switches etc should be avoided. The whole boat gets very wet with spray so electrics are to be avoided.

Steve.

Unfortunately ALL 'current' nitrous system are electrically powered and activated, so switches are unavoidable with 'current' systems.
However, if you really can't manage to make an electrical system water tight, we used to manufacture a cable operated (manual) system that would solve that problem and on such a modest power increase your pump 'might' be adequate.

To determine how the system would be best fitted, I'd really need to see a pic of the induction system, so if you can send that to trev@noswizard.com I'd be happy to advise you accordingly.

What about one of those little kits you made that used propane and a small battery from a lawn mower or something

Propane would certainly be a good solution but he'd need more than those systems delivered. Thankfully I've come up with a way of fitting a system to this now and I'm just about to send out a quotation for it.