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The mkiv Supra Owners Club

what water to use in water injection?


supra matt

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It will be ok for now, but i don't think its big enough, its difficult to tell unless you have a wideband, the AFR will go richer if your injecting the right amount of water are you planning on fitting something to control fuelling etc?

 

hi ricky ya i got a wide band gauge it runs rich any how when on boost or wot i goes down to 10.2 :Pling: . ya i got a safc 2 to take some fule out top end . Just need it setting up now :D

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Water doesn't affect AFR guys. But if done correctly it allows you to run safer *and* leaner.

 

If the methanol content is appreciable (3% or more of fuel) then you do see it go richer.

 

Sorry but i can't agree! on every car i have used water injection on, it has affected the AFR! when used at the correct quantity's and that is without methanol, if you take a look at some of the proven scientific papers that are written on the subject, it will explain why, as i can't remember offhand, i will provide a link when i can find one, as the Aquamist WI forum is down at the moment, so i can't link it through there, must have been doing something wrong all this time then.

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hi ricky ya i got a wide band gauge it runs rich any how when on boost or wot i goes down to 10.2 :Pling: . ya i got a safc 2 to take some fule out top end . Just need it setting up now :D

 

Yes the TT goes silly rich at WOT especially when decated, i have seen AFR as low as 8.9 before i adjusted the fuelling but that is due to water injection, what wideband have you got? can you datalog? the thing to do is log a couple of WOT runs without water, and then again with water, before you start to take any fuel out, i have a chart somewhere that will give the appropriate jet size for the Supra, calculated on the overall fuelling, will see if i can find it.

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Matt the ideal AFR for power is 12.5 BUT do not try and run this, it will provide good power BUT it will be to close to melting things, it can be done with WI but unless you have various safeguards in place, ie automatic boost cut or timing retard, should the WI fail, you risk meltdown:(

as you have no failsafe device i would only aim for 11.5 perhaps 11.8, at WOT/full boost, it will still give good power but be relatively safe.

 

Oh and running AFRs of 10.0 or slightly below is not a problem, although not good for power.

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Sorry but i can't agree! on every car i have used water injection on, it has affected the AFR! when used at the correct quantity's and that is without methanol

Do you think that the water retains or releases oxygen?

..., if you take a look at some of the proven scientific papers that are written on the subject, it will explain why, as i can't remember offhand,..

Some of them I've uploaded myself, lol...

..the Aquamist WI forum is down at the moment, so i can't link it through there,..

It's been hacked, you do know the WI forum moderator, right?;)

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Just recounting my experiences with water injection john,

not trying to prove who knows best!:rolleyes: and yes i do know you moderate the WI forum, moderation does not pre define expertise in the subject, so if you have seen or uploaded some of the papers on the subject then you must know there is a document that has some relation to what i mentioned?

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If injecting water alters the AFRs then that's an indication that the speed of burn has slowed down too much. (so you don't manage to burn as much fuel as before the WI - but since the ECU sprays as much, the wideband shows rich;) )

 

Typically that means too much water is being sprayed too early, or the cylinder distribution is not very good - leading most of the water into one or two cylinders. The wideband simply averages out the results, no way to tell who the culprit is.

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i'd say use demineralised water and if its working properly it should cause a change in the AFR.

Water injection cools the surrounding air and allows you to push more mass air into the cylinders which in result should mean more fuelling.

 

I've not done much with car engine water injection but surely you should set these up to run water flowing at high rpm WOT

All my experience is with things that produce 22500lbs of static thrust :D

 

Out of interest does it allow temperatures elsewhere to rise EGT etc

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If injecting water alters the AFRs then that's an indication that the speed of burn has slowed down too much. (so you don't manage to burn as much fuel as before the WI - but since the ECU sprays as much, the wideband shows rich;) )

 

Typically that means too much water is being sprayed too early, or the cylinder distribution is not very good - leading most of the water into one or two cylinders. The wideband simply averages out the results, no way to tell who the culprit is.

 

Apology's John, after finding a couple of the write ups i was thinking of, i have found i have my wires crossed, slow burn is a contributing factor, and it can also cause a temperature drop across the lambda, which in turn can cause lowered AFRs, which is a little worrying as the first lambda is the std one?

i will keep looking as i'm sure there is document that has another explanation for lowered AFRs.

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AFRs should not be looked in isolation, because they can be deceptive sometimes. Not as deceptive as EGTs, but one still has to be aware of the possibility.

 

Here's another example:

You are overfuelling like mad and the WB shows that. Nice.

Because of the overfuelling, under full boost you get some missfires - the WB shows lean at the time of the missfires, so the 'natural' thing is to assume that you are running lean under full load and you need even more fuel.

This makes matters worse of course, and despite risking borewash the damn thing still misfires and shows lean.

 

This is a standard 'gotcha' by the way;)

 

The answer lies in understanding what the WB does: it counts stray oxygen molecules. The more it finds, the leaner it shows. (oversimplified, but does the job here)

 

When you have a rich misfire, there is no proper combustion, so the fuel doesn't get used up. The oxygen doesn't get used up either, so it finds it's way through the tailpipe --- hence the WB is fooled to showing 'lean':eyebrows:

 

In similar lines, injecting other liquids in the CCs is bound to affect combustion in some way - so the AFR readings would change.

The trick is not to create an erroneous Cause/Effect relationship in the likes of: the table has legs. The dog has legs. Therefore the dog is a table.:D

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WI when done properly allows you to run 12-13:1 with a *larger* safety margin compared to silly-rich (11:1 and the like)

 

If you are not sure about the quality of your WI installation, then 12:1 is a safe compromise.

 

Richer than 12:1 and you lose power for no good reason. Remember that water is FOUR times more effective than fuel in absorbing excess heat in the combustion chambers.

Without the need for heat absorption 14:1 would be plenty good for safe power (I've run 14:1 under full boost and it runs very smooth indeed):cool:

 

...but without a nozzle in each runner we cannot be 100% confident about even distribution, hence the 13:1;)

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