Nitrous

Just a little!!! My site.

thanks for that - I've already been looking at your site mate prior to posting on here :o)))

I'm in South Yorkshire and I've been looking at getting the kit done by these folks..

They seem a little bit pricey but look to have some good kit. I spoke to one of there guys on the phone and he said best/cheapest option is to buy the kit, fit it and then have them test it.

Yep, trev knows what hes doing... Talk to him often.

I would do it all myself but it depends on your abilities?

I'm a novice mechanic (quite capable of removing and fitting most things but I admit my background knowledge is limited). My brother has master mechanic qualifications and has much more in depth knowledge about engines and systems, his day job is fixing cars. I'm still reading your site BTW, chances are I'll end up having a go myself (with a little help). A mate of mine is wanting to do the same to his Audi 80 coupe, that's got a 2.2L 5 cylinder Quattro engine and goes like stink already.

I'm trying to understand how the injection of nitrous/extra fuel is actually physically done in a controlled manner, is it just fired into the plenum chamber with extra fuel feed once activated? Wouldn't they need to be progressively linked to the engine RPM. How will this affect the ECU engine and fuel management system which constantly monitors and adjusts, many times a second, the standard fuel injection on this car. How can it ensure equal distribution to all cylinders? The injectors fire the normal fuel supply straight into the void above the cylinder inlet ports and not into the low pressure plenum chamber reservoir. Will this affect the fuel/engine management sensors once the nitrous mixture starts to be drawn into the mix? The other thing that I can't quite figure is how the rising engine rpm and subsequent increased air flow through this chamber which will affect the n20/extra fuel/air ratio, can maintain the power increase with a fixed n2o/extra fuel supply (Is it a progressive delivery?) and vastly more air, wouldn't the n2o component be greatly reduced at higher rpm. Sorry if these are daft questions.

You can do progressive control, see the bottom of this reply. OTOH, you can just cram in 50 horses (controlled by the size of the jet, you'd just open the solenoid valve to let the flow through) of nitrous at say, 4000 revs and get the power + torque lines instantly lifted up the graph.

How do you think SPI rather than MPI injection works? Assuming all your pistons are managing to pull in similar amounts of air / fuel, they should get similar amounts of laughing gas.

I'm pretty sure Burgerman covers progressive control through PWM (pulse width modulation) of the fuel / gas solenoids. I read the old version of the site, so I couldn't tell you where to look on the new one. PWM control would look something like this for say, 66% of full power, pulses of on on off, on on off, or off off on for 33%. With progressive control you'd be able to get some boost from nitrous at lower revs without so much fear of turning your engine's internals into s**te from trying to transmit masses of torque.

Thanks for the reply

Yes. Constant nitrous, and constant fuel flow in a basic system. You can do this progressively, via a pulsed controller based on time and/or rpm.

No.

At WOT conditions it resorts to a fuel "map". No closed loop system is used. Even if it is you would simply jet it with the correct fuel for full power whatever the engines own fuel system does.

How can it ensure equal

Because the nitrous is EXTREMELY effective in atomising the fuel as it enters the motor into a fine fog of nitrous and fuel. It does this at the trhottle body. From here each cylinder in turn draws in its own volume.

Actually since each one draws in a slightly different amount due to manifold/cam/port/valve differences it is actually a more precise method than ionjecting the "right" amount in the normal way per cylinder.

No.

It doesnt. Its a fixed x value regardless of rpm.

can maintain the power increase with a fixed

Of course. Thats why it makes say 40 bhp at 2000 rpm and the same 40 extra at 6000 rpm

I'm nervous about arguing but unless the n2o/extra fuel supply rises with the engines increasing RPM to match the increasing air flow being drawn through the plenum chamber by the cylinders then the ratio of n2o/extra fuel to air (in the chamber) must drop, it can't possibly be same can it? The only constants are the internal dimensions of the chamber and the n2o/extra fuel supply when on. The speed and therefore volume of the air stream it's being injected and atomised into per unit time is constantly changing with engine rpm. Much more air is being drawn through the chamber at higher RPM. If the n2o/extrafuel supply doesn't increase to maintain the ratio then as engine rpm increases the nitrous ratio per unit volume of air passing through the plenum chamber will decrease. This is what i'm trying to understand and trying to say in my usual cryptic way. Unless the nitrous system is only ever on at a fixed engine rpm and thus fixed volume of air per unit time.

Thanks for the reply, I think I'm getting there. :\

Don't be!

Exactly. It does drop. This is why a constant power increase right across the range happens. If you feed in 40bhp at idle, you get 40 EXTRA at idle... If you feed the same 40bhp at 6000 rpm you still get 40 bhp, Extra...

What actually happens is that it fires many more smaller doses as the rpm increases. Like the string chopping machine. If you feed string as constant rate, it chops BIG lumps at slow speed but tiny nibbles 6 times smaller at 6000 chops per sec! But its doing it 6 times faster????

So extra torque decreases with rpm, extra power stays exactly the same, as power is Torquie X rpm?

Forget whats goung through the engine.

Think, you are adding the correct chemical mixture of Nitrous (oxygen) and fuel. Constantly. At all rpms?

Which gives more ENGINE power.

So what! This 40bhp INCREASE still stays the same! Because you are firing less nitrous more often...

..the n2o is increasingly diluted as the airflow increases but the extra heat generating capacity of the n2o remains constant, it's just being used in smaller amounts more often per unit time... i'm getting there.

And if the string was fed faster as the cutter sped up it would make a hole pile of big lumps in next to no time. The penny has finally dropped. (burgerman holds his head)

If the ratio of nitrous was maintained then a jet giving say an extra 40bhp at 2000rpm would progressively result in an extra power increase of 120bhp at 6000rpm (or thereabouts) a very hot engine and a very nice torque curve. My only concern now is how it will affect the existing fuel management system and sensors if at all, which is what really started me on this thread. I can't imagine how it couldn't but that's probably me being thick. There has to be more exhaust gas leaving the cylinders which is one of the monitored quantities i believe.

Yep. This is what an expensive rpm controlled nitrous pulse controller achieves.

At FULL throttle, those sensors are unused. The motor resorts to a slightly rich 4 to 5 percent C0, and a simple map. Don't worry, its not important!

No, exhaust gas free oxygen is measured, but to be cortrect on nitrous would be off its rich scale anyway... But this is NOT used at full throttle, just cruise and idle.

SORTED, hats off to the burgerman. All I need to do now is figure out what bits are best to buy and how I can get them in there. Easy :o)

he can tell you that aswell.