Silver arrow

One thing is for sure, WI isn't for the set and forget people. I simply would give up 10 hp to not have to screw with constantly tuning and making sure it's full. My end goal is as much HP as I can get while maintaining near stock sound, ride, idle, driveabilty, and reliability. I want my car to be what it could have been stock.

peter head

There are plenty of water injection systems which doesn't need tweeking every two days - they are there and available now.

Remember the days when car used carburattors? Like anything else, If your go for the more matured WI systems, all you need to do is add water when you refill your fuel tank - but it will cost more than the "constantly tweeking type"

Imaging your car uses less fuel on higher power-runs than the manufacturer's standard output power. Is this worth lifting your arm to refill the water tank between alternate fuel fill?

Peter head - observer

jehcpa

I agree in no manner is it for people who do not monitor their fluid levels. But it isn't exactly a daily list of chores to complete - conscientious awareness and monitoring of the new system is all that is required. But it is not appropriate for those that want to set and forget - fill up with gas and turn the key.

I also wouldn't bother with doing anything more complicated than buying a higher octane fuel for only 10hp, fortunately we are dealing with a lot more of an increase than that.

I think it was the navyblue diy system but on someone else's car and conversations with navyblue convinced the other person's tuner to give WI a fair shot as a tuning tool.

As more and more WRX's implement these systems and based on my experience across makes and applications for going on 20 years, my guess is that maintaining a knock free tune at MBT will increase torque and hp by about 10% for each full multiple of reduction in the AFR. So by reducing fueling from 11:1 to 12:1 a user should expect at least a 10% improvement in their power measures knock-free and at MBT from tune to tune. Reductions from 11:1 to 13:1 should yield at least 20% improvement. From the tuning that has gone on during the summer months of 2003 I think most would agree these are conservative estimates based on the results of those using the UTECs and WI.

Of course two things about AFR - there is no point in going leaner than 13:1 because due to inefficiencies of the chamber - even though all the fuel isn't being used leaner than 13:1 all the oxygen won't be either. You really want to at least use up all the oxygen. The second thing is that water dilutes the partial pressures being measured by a wide band lambda sensor and reports AFR closer to stoic than is actually occuring. Can't get a firm figure on the error but my best guess is that when my sensor reads 13:1 AFR my actual AFR is closer to 12.5:1.

Lastly with water/methanol mixes things get really out of synch and calibration since methanol has its own stoich point and also can permit further leaning of gasoline since methanol will burn in its place. But I wouldn't expect my 10% rule of thumb to continue to apply leaner than 13:1 air to gasoline - maybe 5% more after that point when replacing gasoline with methanol. NavyBlue has done some work pulling a lot of gasoline and using methanol - he may have more input on that aspect.

Ed.

jehcpa

Yes, you should be able to road tune for water injection. I think you would be surprised what a good tuner can accomplish using a road dyno with data logs. Obviously the more tools available the better and the tuning may occur over an extended period of time rather than in one hour or one day, but taking it in steps incrementally is good experience for seeing what is occuring and how the progession of the tune is developing.

Ed.

peter head

Using high octane fuel only means that you can run higher boost or more ignition advaces without detonation, it doesn't mean that you can ignore high in-cylinder pressures and temperatures.

Due to the extra power produced, you still need some form of in-cylinder cooling - dumping fuel or water injection. Dumping high octane fuel is expensive.

There is more reason to inject water (whilst we are on the water injection related thread) when tuned for high octane fuel - the melting point of the piston is still the same on 91 or 100 octane fuel.

peter head

It would be interesting to know, at lease for myself if Fuel-Dumping is being widely used by most tuners as wells as car makers, such as WRX and EVO, would this practice be acceptable as the Holy Grail of Power tuning?

If the answer is yes, there is not reason for any tuning company to exist as dumping fuel is so easy to do for anyone who can just increase the fuel pressure and turn up the boost - rather paying for big dollars to the tuners to do virtually the same thing.

Any anwers would be appreciated.

jehcpa

Manufacturers definitely use fuel dumping to suppress knock from a baseline setting. The use timing retard to catch any knock that gets through the fuel dumping. It is done because it requires no thought on the drivers part and gas is paid for by the consumer and is relatively cheap in most of their eyes (7 mpg Expeditions). It is also done for when a driver either doesn't or can't use a decent octane rating.

Stage 0/1 tuning will pull that fuel on the basis that the user will only use the highest tune available. If you use 87 octane on a 93 octane map - the safety fuel has been pulled too far to suppress knock and you will see timing pulled way back from the resulting knock.

Power tuning still relies on fuel dumping to prevent baseline knock - they just dump less fuel than OEM. Hence the reason for additional power even when boost is not increased - until your AFR is at optimal power AFR any leaning increases power. If boost is increased two things occur you have more air which will burn more of the fuel and to prevent knock less fuel will be pulled from the maps.

But mainstream tuners do use fuel dumping look at their target AFR and stage progression - at some point they all require updated injectors to reach those rich targert AFRs. Keep in mind though that even with water injection you eventually will need additional fuel flow once you get to an air flow point where all the oxygen isn't being used.

Even though water injection can help get more from the stock injectors than you could otherwise get - it really is not a bad idea to have enough fuel injector capacity to be able to get to a safe fuel dumping tune even if it is not a powerful one.

The benefit of big dollar tuners are that they know the car's characteristics and how much fuel can be pulled and still suppress knock for those that don't know or want to find out on their own where that higher power but still safe level of tune is.

I think those implementing water injection properly are showing that for power producing purposes using water in place of extra fuel will add power safely.

I guess my answer is that the holy grail of power tuning is the highest level of power you can get while still suppressing knock - some use fuel for suppression others are using water. The science shows that using water instead of fuel will result in more power. Though the complexity, monitoring and maitenance is the trade off. Fuel dumping is easy since that is the starting point from the factory.

Ed.

jehcpa

My WRX was using an adapted system 2d. You would need to tune for any of the kits or at least contemplate the impact of the water being injected. During the off season here in the NE I am preparing my STi now for the same setup.

The 1s is like many DIY kits - a pump is turned on and off by a trigger in this case a set boost level. Prior to injection the water is at a fixed pressure and a fixed flow. With increasing boost the differential pressure across the jet face decreases which will decrease the water pressure and flow into the intake. Additionally as rpm increases the steady flow rate of the water results in less and less water in each cylinder stroke. Neither of these are good for optimal tuning. At low load/rpm levels you will probably have too much water to be optimal and high load/rpm levels you will probably have to little water to be optimal. I only recommend the 1s for people who are not going to tune specifically for water injection but rather simply to provide some additional knock suppression and cylinder cooling over an already safe tune - knock sensing ignition will generally increase advance naturally in this case (except UTEC-like systems which have a max and only retard). I would only recommend using a very small jet to make sure the engine never bogs but the induction charge and cylinders get some cooling help.

The 2d provides a water flow that is progressive with rpm and load by following a system that is already designed very well for that purpose - the fuel system. As load/rpm increases, your fuel IDC increases and so will the flow of water. It does not address the drop in pressure differential but rarely are you exactly metering water as you would with fuel it works well over a nice range so if you can get 10% - 15% water to fuel you can tune optimally for the conditions. If you are already doing road tuning, you can road tune for this as well. Won't be as optimal as a dyno maybe but you will be able to get a good tune, many in the lower 48 road tuned before they went to a dyno with results they were pleased with.

The 2c can be driven by any third party EM that can drive an extra fuel injector. For instance some have converted UTEC's boost solenoid drive to drive the HSV with good success (it does require some beta firmware from txs and a stand alone boost controller for boost control). Xede can also be modified to drive the HSV directly though I am not thrilled with its frequency which is too high for throttle body injection of a liquid. Other fuel controllers that have additional drives can also be used Link, Autronic, Motec, etc. or a stand alone auxillary fuel controller. The nice thing about the 2c you can actually peak the water flow during boost transition and other knock sensitive times and reduce the amount of fuel to water in higher rpms where boost and knock tendencies sometimes decreases.

This was a brief overview and I hope it helped - but provided your objectives are well defined in advance you can get the right system to achieve them and implement it with satisfaction.

Ed.