Water injection?

[paul jacobs]

Having just waded through the NOS topic, for which many thanks PC for your usual comprehensive reply, it set me wondering about the advantages of water injection.

 

This would seem to offer the benefits of higher HP due to better cooling of the intake charge mixture, without the downsides of blowing up the engine, in fact it could even help with the reliability. It must also be cheaper to install, environmentally friendly, naturally sustainable and lighter.

 

Anyone had a experience of it or got any good or bad comments [PC?]

[sjwb]

Generally used to cool the compressed (ie hotter) incoming charge on forced induction motors. You know, when you compress a gas it gets hotter, which is the opposite requirement for inlet gases.

Not sure about naturally aspirated engines.

 

Steve B

[Bob Corb]

You'd need to use something more volatile to have a benefit on an NA motor. Switching to methanol fuel has benefits but is a very long topic to get into at this time in the morning. Nitrous systems are the best in this respect for charge cooling.

 

You could just try to duct colder air to the engine in the first place and prevent it from being heated in the runners by applying an insulating coating right down the runners and into the ports. Also good exhaust insulation to keep under bonnet temps down will help.

 

BC

[AMMO]

I met Richard Lamb from ERL a few years ago. He makes water injection equipment. At the time I was racing an air-cooled V-twin with quite high compression and had been considering water injection.

 

Richard told me that he knew of nobody who had used his kit for normally aspirated applications, it is used only with forced induction.

 

As for lightness, remember you have to carry a load of water around. Also if it was such a great idea, how come no front-runners (that I know of) are using it in NA applications?

 

AMMO

[Old Septimus]

Whilst we are on these exotic topics, where does nitro (?methanol) fit into the scheme of things?

[Bob Corb]

Right, getting complicated eh?

 

Methanol injection - lower calorific value (CV) than petrol but less likely to suffer det problems. Volatile hence good charge air cooling from evaporation hence more air per cycle, runs richer (~8:1?) than petrol so more fuel of lower CV can be burned. Engines compression ratio should be increased to take advantage of the lower propensity for det/knock. Overall the increase in engine power is marginal (in this NA example anyway) and your fuel tank will need to be twice the size for the same range. Methanol is an expensive fuel - not worth the bother.

 

Nitromethanol - not sure about this but if I assume its a combination of nitroglycerin and methanol then basically its a fuel which carries mostof its own oxidant, therfore you can put more fuel in compared to the same engine running on methanol alone (i.e. ridiculaously low AFR). This would give massive power increases but would tear the engine apart unless it was custom built to handle stupid cylinder pressures. Forced induction would then increase the cylinder pressures and power into the stratosphere hence 5000BHP drag racers. But have you seen someone trying to start one up....

 

Charge cooling on an NA petrol motor is achieved by optimal positioning of injectors (hence twin injector per cylinder setups.

 

How about water injection into the exhaust manifold?? Control exhaust temp therefore allow exhaust pulse tuning to be optimised over a larger range of speeds as you can control the speed of sound.

 

Got to go lunchtime over.

 

BC

 

Edited by - bob corb on 22 Feb 2002 14:53:06

[John Reay]

I had an ERL water injection kit on an 8injector 16v turbo Golf I used to own. It made a huge difference to the way the car drove because we could use more ignition advance. I managed to find 20bhp just by remapping the ignition curve when the water was 'on'

I used to run a 50% water 50% methanol mix which gives a further 1.5 octance. The most amazing thing was that you could drive the car very very hard and the engine just stayed nice and cool.

 

I know some people run them on nat aspirated engines but I can't really see the benefit, but if you are turbo'd or supercharged then it is certainly an option.

 

I've since sold the car and taken to the world of Sevening, much more fun biggrin.gif

 

John