Injecting water into a rich a/f mixture is not a good idea

[Sampi]

Hi, I just installed Aquamist S1 system to my Audi A8 1.8T quattro 1999. It has a swedish BSR chip in it and it dynoed nicely 144 kW and 340 Nm last time.
Now I went to dyno again to check the effect of recently installed Supersprint catback exhaust etc. and installed S1 after that. 98 fuel is recommended with the chip, alltough I?ve been using 95 in daily driving. Well, I fueled the car with 98 octane pump gas for the dyno run and got LOWER figures from the dyno. Engine was running heavily rich (AFR 11-11,5:1,), S1-installer said that benefits of S1-system are seen only after AFR of 12,5:1. S1 brought only minor benefits when engine and room were hot. What could cause that overfuelling? Ofcourse S1 shoud be adjused with progammable chip to make it more usefull, but could that gasoline hassle be the cause of ECU?s eratict behaviour?

[Richard L]

Originally Posted by Sampi

Hi, I just installed Aquamist S1 system to my Audi A8 1.8T quattro 1999. It has a swedish BSR chip in it and it dynoed nicely 144 kW and 340 Nm last time.
Now I went to dyno again to check the effect of recently installed Supersprint catback exhaust etc. and installed S1 after that. 98 fuel is recommended with the chip, alltough I?ve been using 95 in daily driving. Well, I fueled the car with 98 octane pump gas for the dyno run and got LOWER figures from the dyno. Engine was running heavily rich (AFR 11-11,5:1,), S1-installer said that benefits of S1-system are seen only after AFR of 12,5:1. S1 brought only minor benefits when engine and room were hot. What could cause that overfuelling? Ofcourse S1 shoud be adjused with progammable chip to make it more usefull, but could that gasoline hassle be the cause of ECU?s eratict behaviour?

I have just posted a similar answer on the following thread:
http://www.aquamist.co.uk/phpBB2/vie...hp?p=7057#7057

Please read it first and I will try to see if I can help you to tackle your current situation.

First of all. Untill you did a back to back dybo plot on the same day, it wouldn't be a good comparison. Anyway - putting WI on an already rich afr is not going to help power at all. Your combustion temperature may already being overcooler.

It the summer, you may have a positive gain on WI but in winter, we get a few post on this topic.

Richard

[JohnA]

True, the majority of people stick W.I. on top of an engine running extremely rich and then they complain that W.I. is useless (or even loses them power)

I did dyno runs on mine and only started seeing pure gains as the AFR dipped to 12:0 and beyond (13:0, didn't have the nerve to run leaner under full boostops: )

Adding water as the AFR was 10.5:1 did nothing for extra power - didn't lose power either, as I was way beyond the manufacturer's limits. At 12.5:1 I was looking at 8% more power with around 10% water/fuel ratio.

[Revhead]

Originally Posted by Richard L

Not so long ago, a user of our WI system has lost some 40+ WRHP during a dyno tuning session, not surprise to know that he was quite disappointed. Only after a few months later and have discovered that his engine is tuned to run an a/f ratio of around 10.5:1.

I would really like to hear from anyone if they have suffered the same experience?

I wonder if the tuner's intention was to get extra power by fitting the water injection alone without optimising the other engine's supporting hardware(ie increasing boost). IMO, the tuner may have thought the water injection as a pure power adder(ie nitrous).

I may be wrong here but the reason one(for me) would run a water injection is to maximize the whole setup(run as much boost, compression ratio, ideal ignition advance..etc) with commercially available fuel.

Bottom line, if mapped for the WI then fuel has to be reduced due to the water occupying the space normaly occupied by air, that means if the water is NOT working the lean running results. Given the above then ign can be advanced to take advantage of the cooler charge.

I agree...or increase boost.

[keithmac]

On my Megasquirt you can use the output from the pump as a trigger to go onto the second fuel tabel and spark table, so if the pump doesn`t trigger the maps don`t switch, seems the safest way to do it? if the pump/wiring fails the engine just runs in non-water mode.

[1 Quick Bunny]

Keith, would you mind sharing specifics on this? Especially your wiring specifics. I still don't have mine fully integrated.

[Wolf_Tm250]

Originally Posted by JohnA

Adding water as the AFR was 10.5:1 did nothing for extra power - didn't lose power either, as I was way beyond the manufacturer's limits. At 12.5:1 I was looking at 8% more power with around 10% water/fuel ratio.

I have an HFS-5 progressive system Motec-PWM driven:

could anyone tell me HOW to know I'm getting a 10% w/f ratio entering my engine ?

TIA !

[JohnA]

Originally Posted by Wolf_Tm250

...could anyone tell me HOW to know I'm getting a 10% w/f ratio entering my engine ?

TIA !

Example: If you have six 500cc/min injectors then they provide 3000cc/min when maxed out, right?
If they are operating at 80% duty rate when you WI is operational, that means they are providing 2400cc/min.

If your WI with the pressures/nozzles you've got provide 240cc/min, then you have (at that point) a 10% w/f ratio :smile:

[Wolf_Tm250]

Originally Posted by JohnA

Example: If you have six 500cc/min injectors then they provide 3000cc/min when maxed out, right?
If they are operating at 80% duty rate when you WI is operational, that means they are providing 2400cc/min.

If your WI with the pressures/nozzles you've got provide 240cc/min, then you have (at that point) a 10% w/f ratio :smile:

Sorry JohnA....

I didn't explain correctly what I meant to know....

I perfectly understand what you wrote me... fortunately :lol: :lol: :lol: :lol: ....

but what I'd like to know is WHAT is the relation between the PWM values in my PWM-Motec map, AND the water quantity coming out from my nozzles....

Moreover, given that I have a progressive pump, the water injected varies even with the water pressure supplied by the water pump...

Could I use the cc/min value in the DDS3 flow sensor as a good, real value to make my calculations ?

Thank you very much.

[slowMX5]

Originally Posted by keithmac

On my Megasquirt you can use the output from the pump as a trigger to go onto the second fuel tabel and spark table, so if the pump doesn`t trigger the maps don`t switch, seems the safest way to do it? if the pump/wiring fails the engine just runs in non-water mode.

One thing that I am keen to get working is to use the flow meters Vout as a fuel/ignition trim. This could either apply a trim to reduce timing and add fuel to ones WI map if the signal disappears or one could use it in reverse to add timing and pull fuel from the table in proportion to water flow. That way one runs a safe default map with timing and fuel adjusted as WI flow increases.

When I was looking at this a couple of years ago (been too busy to look into it over the last 2 years) the DDS2s output signal was too noisy - not sure if it has been smoothed yet or is the DDS3 has a smooth signal that can be used?