Mark B

Hi,

I have a 95 wrx with no ABS, but instead have a water injection cylinder behind the drivers headlamp. Am I supposed to find a switch for this, or is it totally automatic. Does it need refilling?

I also have a gizmo box called a AFR (air flow resetter) with 2 buttons; one which has some numbers next to it which can obviously be changed. Does anyone know what this does, as yet I have not touched it.

andrew

I've got a WRX RA, which also comes with no ABS as standard, and it also has a water spray onto the intercooler. I've got a switch on the left handside of the steering column which when pressed squirts water onto the intercooler for about 5 secs. Later cars have an automatic setting for the water spray. Maybe you should check if you can find the wiring for the washer motor fitted to the bottle, and see if it is connected to the switch you mention.

I can't really see the need for the water spray in normal UK use, as we seem to have water spray from the sky most of the time anyway! Maybe on track days?

Mark B

Andrew,

I have looked to the left of the steering wheel and there is a black swtich which goes up or down. It currently is on up. When stationary if I flick it down the engine sounds like it has gone into a different mode by reving slightly. You definately know it has done something. Is this the switch.

However, I was gunning it up a hill last week and temptation got the better of me so I flicked the switch down and the car cut out. How embarassing. I stopped and restarted it, and it was fine. I stopped a bit later and put the switch back to the up mode.

Any comments would be appreciated.

Any help on the the Air Flow Resetter?????

Moray Mackenzie

Are you sure the AFR box doesn't monitor and/or adjust the Air Fuel Ratio? If so it would not be wise to play with it without expert help (maybe at a rolling road tuning centre)!

andrew

I guess that your car is missing the switch that mine has, sorry!

Does the water bottle behind the drivers headlight have a pump attached to it?

Do you have rubber pipework on the underside of the bonnet where the air intake scoop is? If you have it should be connected to two spray heads, a bit like the windscreen washers jets on the other side of the bonnet!
This is how the water spray is set up on my car, it looks a standard factory install

hope this helps

Mark B

Andrew,

I'll pop the bonnet tomorrow and have a look. So does the water spray just literally spray water onto the engine? What actually does it do?

abetts

It sprays water onto the intercooler thus reducing the temperature of the air which goes into the engine. Lower temperature means denser air. If fuel is mixed in the right ratio this should result in more power.

That is the theory. In the British climate and in normal road use I am pretty sceptical as to whether it has any value other than impressing your mates.

clarence

I think the I/C waterspray facility is more suitable for Japanese use as they have hot summers there.
Turbo engines produces a lot of heat and if driven hard during high ambient temperatures, the engine will gradually lose power due to thermal loss. The waterspray will help to regain some of the power lost. The Mazda RX-7 (pre-facelift) suffers badly from this problem and Skyline GT-Rs will also suffer if the optional oil cooler is not specified (standard in UK spec cars).

Mike Tuckwood

Now my technical knowledge is not as complete as most others so this will come in the form of a question.

Is the main job of the waterspay not to increase the DENSITY of the air fuel mix, so there is more to compress?

The actual air cooling capabilities of the device being perceived as more of a calculated bonus. While being technically viable, if the air is cool anyway it is still contributing to the performance?

Russell Haley

Humid or wet air is generally LESS dense than dry air otherwise the clouds would sink !!

Of course as the humidity increases towards 100% and the water is no longer as a vapour the air density increases and it turns to water and it rains !

There are two types of "water injection" - not sure which the STI has as I'm fairly new to the car, but the explanation for both is:

Spray ONTO the intercooler radiator means better cooling hence denser air and therefore the engine management system can inject more fuel. This is why charge coolers (air-water intercoolers like on some Esprits) are better than air-air intercoolers as they maintain a more constant inlet temperature.

Water injection directly into the cylinders is to cool the charge and allow more ignition advance, more efficient combustion and hence more power.

As I said, don't know which one you guys have, but hope this helps.

Russ

Benny Boy

Now here's a thing......

Compressed air is extremely cold, and very, VERY dense. Now, why hasn't somebody come up with a way of injecting compressed air into an engine in tiny spurts over a certain r.p.m.? To rig up 2 scuba bottles with 7200 litres of air is very easy and then think of the results. A lot safer than NO2 (Nitrous Oxide), cheaper and easier to fill.

Have I missed the point?
Benny

Russell Haley

Had a ride in a supercharged Mini with Nitrous injection once - my terror was only short lived though as the engine didn't get us home !

You can get the turbo to do the same as the air bottles - just keep the waste gate closed and block off the dump valve but then the engine won't last so long !

Nitrous works because it has more oxygen per unit volume than air so gives you more power for the same cylinder pressures.

abetts

Re. Russell Haley's post. Subaru use water spray onto the intercooler as opposed to water injection. The reason for cooling is not purely down to climate. Air heats up when you compress it.

Mark B

Had my car in for a service today, and asked them to confirm whether I had water injection or not. They said no, the cylinder thingy behind the drivers side headlamp is a type of carbon filter system??

Is this right?

clarence

Subaru put the waterspray onto the I/C because it's situated on top of the engine rather than in front of the radiator (as in GT-R, Evo VI etc), therefore the cooling efficiency is not as good. With the hot climate in Japan during summer, waterspray is needed if the car is driven hard because the hot air from outside cannot cool down the I/C sufficiently due to the high temperatures in the engine bay and the fact that the engine is directly below the I/C.
I've been in a STi IV at the end of last summer in Japan where temperatures are around 22-23 deg, after 30 mins of hard driving, the heat given out in the engine bay is unbelieveable when u open the bonnet.

Mark McE

I think the reason the water spray (& adjustable centre diff) were fitted to RA's is that for group N rally use you had to homologate any bits & bobs you wanted to use on the rally cars - hence the silly gearing & stuff.

I use it if i've been sitting in traffic for a while and then want to let it rip as i think it should help get rid of the heat soak thats happened whilst there's not been much air passing through under the bonnet.It also might help to cool things down after a good run.

Cheers, Mark.

clarence

I think as well as for homologation purposes, the I/C will need more cooling 'cos of the short gear ratios (meaning higher revs at the same speed compared to the standard ratios).
Please correct me if I'm wrong, Subaru only homologated the WRX Type-RA for Gr.N and the WRX STi, the WRX STi Type-RA and the WRX STi Type-R are not homologated. It also means that the adjustable centre diff is not homologated 'cos only the STi Type-RA and Type-R are equipped with it. The Impreza WRX Type-RA is not equipped with adjustable centra diff.
The Impreza homologated for Gr.A is called the Impreza 555, I think it's based on the Impreza WRX (again non-STi) because at the time of homologation, Subaru hasn't started making STi's yet, and the 555 has a small rear spoiler.

malique

huh?

dmel

To Benny Boy:
Things are not as you describe them.
The first law of thermodynamics is DU=DW
+DQ. The internal energy of the gas is equal to the amount of work you do on the gas plus the net heat transfered to the gas. When you compress the gas quickly i.e. there is no time for heat to be exchanged between the gas and the environment (refered to as adiabatic compression, DQ=0) ALL THE WORK YOU DO GOES TO INCREASE THE INTERNAL ENERGY OF THE GAS i.e. the gas temperature AND pressure increase. This is what happens in the compressor of your engine and this why you need the intercooler. In the scuba bottles there is a small heat exchanger at the compressor (when you fill them up) which tries to get rid of heat and also sometimes compression is done to two stages in order to reduce this problem.

This is simply to say that temperature and pressure are two completely independent variables. Compressed air can be extremely cold, at normal temp., or extremely HOT (as you have it on the heat exchanger at the back end of your fridge) (the cooling medium is usually not air in fridges but the same principles apply nomatter what liquid you use to transfer heat)
Sorry about the lecture. Just trying to sort out thermodynamics issues.

DavidLewis

You cannay change the law of physics, Jim!