Some water injection questions
21 December 2002, 05:31 PM
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Can anybody answer the following
1)Will a water injection system actually lower in cylinder temps.If so will it do it enough so as to actually have a protective effect against piston damage
2)Will all cylinders be cooled equally?
3)If using a standard ECU,how will it be triggered?
4)What would be more effective at achieving a protective effect on the cylinders,water injection or an oil cooler?
Many thanks,Deep.
1)Will a water injection system actually lower in cylinder temps.If so will it do it enough so as to actually have a protective effect against piston damage
2)Will all cylinders be cooled equally?
3)If using a standard ECU,how will it be triggered?
4)What would be more effective at achieving a protective effect on the cylinders,water injection or an oil cooler?
Many thanks,Deep.
21 December 2002, 07:02 PM
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Deep,
1) Yes it will lower in cylinder temp's. It also has the effect of raising octane. However, it has limitations. It can't protect the pistons, if the "map" is running lean, or det', if the ignition advance, or boost, is far too high.
If used with the stock ECU, it will lose a little power (few bhp). Although if, and when we get one of those hot summers, I would expect to see some gains.
2)If the jet is correctly placed, the water will be well mixed in the air. This will then get distributed as equally as the air normally is.
The "hottest" cylinder will still run hotter, but overall temp's will be lower.
3)The ERL systems are normally triggered by a pressure switch, provided in the kit.
4) WI, and oil coolers are really doing different things. Keeping the oil cool will help it retain it's film strength, so preventing the bearings, and pistons picking up.
Unless you are really pushing a lot of power, or running the car hard on track, and assuming you are using a GOOD quality oil, your oil temp's should be ok.
WI will help to keep them down though.
Mark.
1) Yes it will lower in cylinder temp's. It also has the effect of raising octane. However, it has limitations. It can't protect the pistons, if the "map" is running lean, or det', if the ignition advance, or boost, is far too high.
If used with the stock ECU, it will lose a little power (few bhp). Although if, and when we get one of those hot summers, I would expect to see some gains.
2)If the jet is correctly placed, the water will be well mixed in the air. This will then get distributed as equally as the air normally is.
The "hottest" cylinder will still run hotter, but overall temp's will be lower.
3)The ERL systems are normally triggered by a pressure switch, provided in the kit.
4) WI, and oil coolers are really doing different things. Keeping the oil cool will help it retain it's film strength, so preventing the bearings, and pistons picking up.
Unless you are really pushing a lot of power, or running the car hard on track, and assuming you are using a GOOD quality oil, your oil temp's should be ok.
WI will help to keep them down though.
Mark.
21 December 2002, 07:58 PM
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Thanks Mark.I've had the Ecutek remap from Pat on mine.Could this be tweaked to take account of the WI so I d'ont get the small decrease in BHP?
I've seen the system you sell.Comes with option of different washer jet sizes.How does one decide on the optimum size.
Cheers,Deep
I've seen the system you sell.Comes with option of different washer jet sizes.How does one decide on the optimum size.
Cheers,Deep
21 December 2002, 08:43 PM
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Deep,
Normally you try to inject about 10% water; IIRC the STi VII has 565cc injecotrs, and there are 4 of them, so that'de be 2260cc/min of fuel as a maximum (but your injector duty cycles aren't that high). You'de need to choose a jet which is close to 200cc/min, I think that would probably be a 0.6 or 0.7, off the top of my head (Mark has flow charts).
The water is normally triggered by a switch, which is pressure dependant, but the Denso ECU in your car computes fuelling from a Mass Air Flow (grammes / cylinder) figure, it would be possible to tweak the map to take advantage of the water, but it's a little trickier than a speed/density system like Link/MoTeC/Pectel etc.
The Denso ECU runs open loop fuel on boost, so you can do pretty much what you want with fuel. Ignition is always under closed loop control; there is a base value that is VERY conservative, and then there is a table which tells the ECU how much more advance it is allowed to add. If one finds that the ECU is using all of the advance it's allowed to run then more can be added to the compensation map. This will allow it to add even more with the water on, but it still retains a very safe base map, but with the added protection of the water. It is worth bearing in mind, though that running more advance will put more heat into the pistons, water jacket etc, so to some extent the benefits of the water are countered by the fact that there's more ignition advance.
It's perhaps worth noting the origin of this thread.... the stock STi VII map is ridiculously rich, if you could get an AFR meter with a scale long enough to handle it, the needle would end up across the channel in France somewhere. I've pulled fuel out, and the engine is much crisper, but it's still very rich. If you were building and tuning a performance engine from scratch then you'de run it a lot leaner than I programmed your ECU to, which is already quite a lot leaner than it left the factory. I have to assume that the STi engineers aren't complete muppets and that they have a good reason for shoving so much fuel in there, and the usual reason is that they're using the extra fuel to cool the combustion space... now that your engine is running a bit leaner it's much crisper, picks up better, and pulls much stronger...
The ECU has "found" another six degrees of advance on boost, which any tuner will tell you is an enormous increase. The "poor" advance originally was almost certainly due to the extremely rich map, there's just so much fuel that it's leaving glowing carbon deposits in the cylinders, now it's getting a more complete burn, but it's still very rich, again to try to keep temps down, but obviously it will be running a little warmer than it has been because a) it's not got as much fuel to carry heat away and b) it's running more advance.
The water injection certainly would help carry away some of this extra heat, but there are a few other cars that I've either mapped myself or been involved with, which are running "proper" AFR (about 12:1, much leaner than yours) and have been making good power for a long long time without any trouble, but they're Phase I engines, which are very different to the STi VII engine; there aren't many people out there who know the limitations of that engine yet... not all of us can afford to blow them up just to figure out what they'll put up with and when they go south
I've been as "gentle" as I can possibly be on your engine, while still getting some good improvements in terms of throttle response, torque and power. The extra heat due to these alterations will be minimal, and the nature of road driving may well see overall temps a little lower (it's pulling through the revs more freely, so it's on boost less time between gear changes, so it has less time to build up heat, etc etc). As a safety feature, water injection will probably get you cooler than it was in the first place, used as a means to getting yet more advance you may be "chasing your own tail"
Cheers,
Pat.
Normally you try to inject about 10% water; IIRC the STi VII has 565cc injecotrs, and there are 4 of them, so that'de be 2260cc/min of fuel as a maximum (but your injector duty cycles aren't that high). You'de need to choose a jet which is close to 200cc/min, I think that would probably be a 0.6 or 0.7, off the top of my head (Mark has flow charts).
The water is normally triggered by a switch, which is pressure dependant, but the Denso ECU in your car computes fuelling from a Mass Air Flow (grammes / cylinder) figure, it would be possible to tweak the map to take advantage of the water, but it's a little trickier than a speed/density system like Link/MoTeC/Pectel etc.
The Denso ECU runs open loop fuel on boost, so you can do pretty much what you want with fuel. Ignition is always under closed loop control; there is a base value that is VERY conservative, and then there is a table which tells the ECU how much more advance it is allowed to add. If one finds that the ECU is using all of the advance it's allowed to run then more can be added to the compensation map. This will allow it to add even more with the water on, but it still retains a very safe base map, but with the added protection of the water. It is worth bearing in mind, though that running more advance will put more heat into the pistons, water jacket etc, so to some extent the benefits of the water are countered by the fact that there's more ignition advance.
It's perhaps worth noting the origin of this thread.... the stock STi VII map is ridiculously rich, if you could get an AFR meter with a scale long enough to handle it, the needle would end up across the channel in France somewhere. I've pulled fuel out, and the engine is much crisper, but it's still very rich. If you were building and tuning a performance engine from scratch then you'de run it a lot leaner than I programmed your ECU to, which is already quite a lot leaner than it left the factory. I have to assume that the STi engineers aren't complete muppets and that they have a good reason for shoving so much fuel in there, and the usual reason is that they're using the extra fuel to cool the combustion space... now that your engine is running a bit leaner it's much crisper, picks up better, and pulls much stronger...
The ECU has "found" another six degrees of advance on boost, which any tuner will tell you is an enormous increase. The "poor" advance originally was almost certainly due to the extremely rich map, there's just so much fuel that it's leaving glowing carbon deposits in the cylinders, now it's getting a more complete burn, but it's still very rich, again to try to keep temps down, but obviously it will be running a little warmer than it has been because a) it's not got as much fuel to carry heat away and b) it's running more advance.
The water injection certainly would help carry away some of this extra heat, but there are a few other cars that I've either mapped myself or been involved with, which are running "proper" AFR (about 12:1, much leaner than yours) and have been making good power for a long long time without any trouble, but they're Phase I engines, which are very different to the STi VII engine; there aren't many people out there who know the limitations of that engine yet... not all of us can afford to blow them up just to figure out what they'll put up with and when they go south
I've been as "gentle" as I can possibly be on your engine, while still getting some good improvements in terms of throttle response, torque and power. The extra heat due to these alterations will be minimal, and the nature of road driving may well see overall temps a little lower (it's pulling through the revs more freely, so it's on boost less time between gear changes, so it has less time to build up heat, etc etc). As a safety feature, water injection will probably get you cooler than it was in the first place, used as a means to getting yet more advance you may be "chasing your own tail" Cheers,
Pat.
21 December 2002, 09:10 PM
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Hi Pat.Thanks for the explanation.The car is running really nicely.So much better,brings a smile to my face at last.However if I was satisfied I would,nt be a Scooby driver! My hope was to adopt a (?pseudo)scientific approach to bring combustion temps down so perhaps we could be a little more aggressive with the tweak.I think that I will go forward with the WI before the tweak and then let you decide whether we can do a little more.
Many thanks and it was a pleasure to meet you,Deep.
Many thanks and it was a pleasure to meet you,Deep.
21 December 2002, 09:17 PM
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Pat, you said that the WI may allow more advance which will increase temps and so cancel any useful effect.However that means that we've got more advance(also maybe leaner mix?) but for the same temp.Does'nt this mean a useful power gain with no deleterious effect on piston temps and hence a sensible way forward?
21 December 2002, 11:48 PM
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Pat, are you saying that increased cylinder pressure & hence torque leading to raised temperatures is more important than the reducing effect of extra advance on EGT? I never got the alterations in EGT I expected by advancing ignition on Phase II engines - is this because there are opposing factors affecting the EGT?
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22 December 2002, 09:25 AM
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Oh, and with a smaller jet you will need to take it off and clean it out at least once a month as I think you live in a hard water area so it will get furred up - and smaller jets do gt blocked much more easily.
Trout
Trout
22 December 2002, 11:12 AM
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Trout,I take it you're running one? If so which system have you got.Just wondering if the all singing ERL version with dash mounted warning lights and flow meters is really necessary.
22 December 2002, 11:33 AM
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Deep,
The nice thing about the DDS2, is that it will not only tell you if you run out of water, but will also tell you if a jet has become blocked. As well as helping you to pick the correct jet size.
It's a little like having a Knock, or Lambda Link, just to let you know everythings running correctly, but you don't HAVE to have them.
Pat could certainly tweek your map so that you don't lose any power. WI can be used for "pure safety", pushing the engine close to it's limits, or, somewhere in between.
Mark.
The nice thing about the DDS2, is that it will not only tell you if you run out of water, but will also tell you if a jet has become blocked. As well as helping you to pick the correct jet size.
It's a little like having a Knock, or Lambda Link, just to let you know everythings running correctly, but you don't HAVE to have them.
Pat could certainly tweek your map so that you don't lose any power. WI can be used for "pure safety", pushing the engine close to it's limits, or, somewhere in between.
Mark.
22 December 2002, 03:40 PM
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Thanks Mark.A couple of questions before I take the plunge.
There is a 2s system that 'allows you to 3D map the water injection to your engine'.Does this have significant advantages over the simpler pressure triggered 1s system(for my requiremwnts,ie Ecutek,want safety,but also a some more power)
Many thanks for taking the time to answer my questions,Deep.
There is a 2s system that 'allows you to 3D map the water injection to your engine'.Does this have significant advantages over the simpler pressure triggered 1s system(for my requiremwnts,ie Ecutek,want safety,but also a some more power)
Many thanks for taking the time to answer my questions,Deep.
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