closed loop operation

[bhearts]

hey everyone. getting my pulse width modulation water meth injection set up on my aspire. i have a 96. im still shooting to make this my gas sipper for nows, so here comes my need for your inputs. i will spray water meth into my motor under cruise conditions and i want to know how much my ecu will correct my fuel trim levels after it sees this extra fuel. what percent correction can i expect under closed loop operations?

[FestYboy]

the water meth won't be seen as a fuel source, so your ST and LT trims will not move much if at all. if you're looking to have it engauge JUST at cruise, use your EGR solenoid control to trigger the meth control. otherwise, i'd tap into a secondary MAP sensor and have a gated trigger activate it inbetween 8 and 14" Hg. that's typical cruise vaccum.

[Advancedynamix]

what are you using to control the injector? Typically water meth is most beneficial under load, which is where your engine is consuming the most fuel anyway. I'm not saying your technique hasn't been used successfully, but its tricky and usually requires the entire engine management system to be tuned specifically for it. It'll be an extremely low flow rate. about 8-10 percent of volume of fuel (by weight) and may require a stronger ignition setup. Also, be cautious of the injectors you use, most are not corrosion resistant enough to be used for long term water injection. We used siemens injectors, but I can't recall the model. The water injection used during engine cruise was only a benefit when the engine was drastically overloaded. Vehicles like a VW Vanagon Camper show improvements, but most economy cars don't. One thing I have also noticed is that when a wideband oxygen sensor is placed at the end of a tail pipe it will read lean (numerically higher percentage of stoic) than what the wideband oxygen sensor will read in the head pipe. This is why I would never dyno tune a water meth system with the dyno O2, I would require a pre cat wideband. Since the research I was involved in is not my intellectual property I can't give much more information than that.

[FestYboy]

yeah, you cant use a sniffer in the tail pipe if there is a cat upstream... you'd have to replace it with a test pipe (hence the term) before tuning.

[Advancedynamix]

Even without a cat I have noticed that the dyno air fuel is usually leaner when the water meth comes on but the car wideband shows slightly richer.

[bhearts]

im to be using a standard water meth injector. im just going to be manipulating the pump for pressure linear to load.

[Advancedynamix]

Gotcha, that's going to be difficult to tune. Not telling you it won't work, so give it all you got. You may want to try using mister system nozzles as they are closer to the flow your looking for and they are cheap and they atomize better than most water meth nozzles. Actually, a few companies use mister system nozzles in their injector kit. When I say mister system, I mean outdoor cooling misters for a patio. They sell them at Home depot here, but your area may not have them, so you may have to go online. They are less than 10 bucks for 3. Hope that helps.

[XFSE71]

I'm replying to this thread because the title "closed loop operation". I am unable to achieve closed loop on my '93. Elsewhere on this site I reported a flooded VAF which caused a good running car to fall down and not get back up since. By resetting the VAF spring tension I managed to get it out of seriously overfueling down to a steady normal idle. In fact I was able to dial in a lean misfire with the VAF. I used propane enrichment and dialed in 25 rpm drop. The CAT is lit. Exhaust stinks running fixed 8.5 ms injector on-time @ idle. The o2 is fixed @ .6V based on VAF, no o2 sweep. I could see the o2 drop to ~.2V during the lean misfire. So I accept that the new o2 is working, simply reporting no change in Exhaust Oxygen content. IAC is working but slow to react.
How do I know I'm not in FMEM? How can I achieve closed loop operation? How can I fix this car?

[FestYboy]

discussed this in the other thread, the PCM MUST see a signal of 160*+ from the ECT sensor in order to enter closed loop (from experiance reading PIDs from scan tools). when a ECT goes dead, it usually reads -34* and the PCM WILL NOT insert a nominal value in its place.

[bhearts]

so im really nooby, but ill ask anyways, why wouldnt my o2 sensor read water/meth as a fuel source. or lets say i planned a different source of fuel lets say propane. thats what closed loop operation is for is to correct lean or rich mixtures to try to get to 14.7 under cruise conditions. thats why i wanted to know if i added an auxilary fuel supplement like a steady state propane from a simple propane bottle, and i was planning this for cruise only, what percent added fuel levels could i expect my ecm to correct before it gets out of its range of correcting. id like to try this with propane because i believe the gaseous state of propane would exceedingly help my combustion burn quality at cruise. could i just monitor my o2 voltage while adding propane, until it breaks a steady voltage, that means it cant correct my fuel trim anymore?

[Movin]

The burn rate of propane is not much of a benefit but the 114 octane will allow the computer to remap the timing curve over time. We can advance the timing on our primitive systems. Using Propane there will be proportional LT fuel adjustments over time. The better running will taper off because of this.

Water Meth will release extra oxygen that will be computed by the o2. The extra fuel from this offsets the extra oxygen for near neutral change to LT or ST. Timing can be advanced. Again the alternative fuel and extra oxygen will produce benefits that are generally better short term. Burn rate again is pretty similar so not much advantage from Meth but when water cracks the hydrogen burns much faster so there is a benefit from that to consume more of the unburned hydrocarbons. The heat of compression and early combustion can only crack so much water, and water that remains a gas or worse a liquid will quickly dampen your improvements.

The check engine light will tell you when it cannot tolerate any additional fuel !