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john banks 09-02-2004 12:29 PM

100% methanol seems preferable
Have posted some info on NASIOC about this, thought would also put it here at Ed's request.

Tried pump fuel tune, mid 11s AFR, 328 WHP on Delta Dash, 19 PSI at peak power.

Added methanol/water injection as screenwash or 50/50 mix and it didn't gain much and detted with high EGTs, tried various different mixtures/timing.

100% ethanol injection controlled the det better and took more timing and leaner AFR, but did not make more than about 335 WHP.

100% methanol injection about 10% of the fuel did 341 WHP.

10% methanol in the tank did 364 WHP.

I tried to optimise AFRs on each setup.

Anyone know how a Techedge wideband will read with a 10% methanol mixture in the gas tank? False high or false low? Seems nice at indicated 12.2 AFR.

Comments welcome.

hotrod 09-02-2004 01:38 PM

Just out of curiosity John.
Did you note any trend on the difference in ideal ignition timing between the pump gas, ethanol and methanol configurations?

I tried to chase down a value for the change in combustion speed as you add alcohol to fuel, but the folks over here at the National Renewable Energy Lab could only confirm that several sources note that the addition of alcohol slows the combustion but no one, gave any objective data so you could judge by how much.

My thinking is given that one of the "problems" WRX tuners have is the tremendous amounts of ignition advance the ECU dials in at high rpm, if you slowed the burn without getting detonation it might dramatically improve power output.


Charged Performance 09-02-2004 09:39 PM

John, thanks for taking the time to come over and sharing your experiences here with those who visit. I still am not convinced that water is not preferable when richer than optimum AFR. But I do respect your contributions elsewhere and considered it worth sharing with as many as possible to consider your work and findings. And bring about a bit of discussion.

When using 50/50 mix - what was your timing like when you were getting det? Did retarding the timing at that point reduce EGT and det? and were you also losing power from retarding at that point? (i.e. is it all possible that you beyond MBT when you were getting det I guess is what I am getting at.)

As methanol is not naturally stoich to the sensor in the same way that water/steam is, I imagine the stoich of 98RON (I believe you are using) and methanol at a 9:1 ratio could be calculated mathematically from the chemical composition of the two. From there you could probably make a rough calibration of your lambda sensor and get a closer answer as to the air-mixed fuel ratio.

john banks 10-02-2004 12:07 AM

I've been playing in the range 25-32 degrees BTDC at 6000 RPM at 19 PSI approx.

Retarding the timing did fix the det with the 50/50 but the power was killed by doing so. EGTs easily got over 900C. Since the power was nothing like optimum despite trying a range of AFRs (limited by EGTs usually if I tried to lean it out) I don't think I got to MBT.

The problem with saying lean it out until there is no excess hydrocarbon is that the engine would have melted I believe. I really don't like EGTs over 900C that are achieved so quickly, on a very prolonged thrash I would tolerate up to 920C which is hotter than most would allow, and that is just before the turbo.

I don't think I can control conditions tightly enough to state the effect of ignition timing on EGTs although I know the theory. The things that affect my EGTs are boost, AFR and how much alcohol was used.

There are other variables that may make my findings different from the theory that water would be better. Probably lots of them.

I just plumped for what was easy to get power from without fear that I wasn't going to melt my engine or det.

Trying yo get my head around what my wideband is doing, I've ended up mapping to EGTs in the high 800s Celcius so far, "12.2" on the wideband seems to get there. Going leaner kills the timing and doesn't seem to add power.

Charged Performance 10-02-2004 12:21 AM

I would agree that you had not reached or passed MBT just trying to bring out more of the details.

I also agree that getting much over 850* I would have stopped leaning you took it farther than I would have. Your results are just so much different from the results I achieved with the 2.0 wrx on both the td-04 at 19psi peak and the vf34 at 21psi peak. Trust me John not doubting your results just trying to understand them.

There is no doubt your boost, AFR and whatever supplement will be the primary determinant of EGT, was just making sure there wasn't timing induced det raising the EGTs but your timing was nowhere advanced enough for that. Your EGTs and det were definitely induction mixture level related for your boost level based on the additional information - but again at odds with my own exeperiences. Did you test the flow of your Aquamist system to make sure it was flowing as much as you thought?

You were using the 2d? What size are your fuel injectors and what was their max IDC? Another thing that has become common is that when using upgraded injectors with the 2d you are lowering your IDC which is also what the the HSV is referencing - therefore your injection mixture is going down too - as your EGTs are going up. Bad thing. The solution here has been with upgraded injectors to use two jets. I have even made a intercooler to throttle body hose with two bosses in it to assist with this without tapping the intercooler.

With those EGTs which I would have never gone near - I would actually say you were not flowing as much injection as you think. Did you have the manifold pressure sensor set to its max setting?

Sorry for the twenty questions. I want to either identify where something in this implementation didn't succeed as it should have not in theory but my actual use - or if there is something truely unusual with the results I and others have gotten with the EJ20 in the US.

At this point I suspect lowered IDCs at less than max Aquamist pressure and flow without a second jet may be the reason for your results. You just should not have been seeing those EGTs with 10% water/methanol mix.

Sorry for the rambling run-on sentences.

john banks 10-02-2004 12:30 AM

I was using 1S and the pressure switch was at various levels between 10 and 16 PSI, I know it was working because when enabled the methanol and ethanol made an obvious change to the AFR - indicated leaner.

Theoretically I am not a fan of the 2D based on the effective map being the complete oppostive of what is shown on the Aquamist site - ie more in the midrange than at the top, not the other way around.

I am using 740cc injectors at 70% IDC at an extra 8 PSI base fuel pressure.

To be honest 900+ EGTs are par for the course at this sort of specific output on Subarus and not necessarily the concern everyone implies - there is of course a boundary layer with the piston and I have sodium filled exhaust valves - I ran over 920 on the original cast piston EJ20 and standard valvetrain and it was perfect, Bob and Harvey (with c. 500 BHP on 2.0 get up to 950C but they have forged pistons and sodium filled exhaust valves).

Charged Performance 10-02-2004 12:44 AM

At the same time the static input of the 1s results in the pressure differential dropping fast at the jet head. While an ideally mapped WI system would peak in the midrange where more knock suppression is needed - I think the 1s is farther from that profile because of the drastic drop off mixture to fuel beyond the midrange. The input pressure is constant but through the jet is not and then the fuel is increasing during the same time the WI mixture is falling. The broader the boost range in which the WI is engaged the less well suited the 1s is the application.

For instance prior to the 2d I would frequently need to use a two or three stage system to get a good broad coverage of water to fuel ratio on higer than 12 psi of boost applications.

Were you hitting those EGTs and det in the midrange or top range?

The 2d will increase its duty cycle at the HSV going from mid to top range - but it will also is losing that pressure differential so it is not as far as the map example from the 2s document.

All my experiences are being related through my use of the 2d. Others may have comparison with a static input system like the 1s.

john banks 10-02-2004 09:29 AM

Det was everywhere, high EGTs were as always worst at the top where the EGBP builds on a small turbo.

john banks 10-02-2004 06:50 PM

From what I could see of the example Aquamist map the absolute amount injected reduced with increasing RPM, so the relative amount to fuel with reduce more dramatically.

The amount injected on the mappable system did not seem to be an RPM aware or scaled quantity but just a duty cycle.

So the 2d would be further from the example than the 1s which would be quite close?

AKWRX 11-02-2004 01:49 AM

Injecting methanol really complicates the tuning process. Complete combustion (stoich) for gas is about 14.7 A/F. For methanol it is about 6.3. Methanol has less fuel energy than gas, but adds considerable quantities of oxygen. Adding, 10% methanol, to gas creates a new unknown stoich value somewhere in between, maybe closer to about 13.8...who knows? The oxygen sensor is primarily measuring the very, very small amount of remaining oxygen from the combustion process. A sensor calibrated for gas will read leaner once significant alcohol is injected (more oxygen is available). The issue is calibration. "How do you know exactly what the A/F accuracy is with this new fuel mix?" Unfortunately, you don't.

It gets even more complex when using a rising rate of alcohol injection. My SMC hardware starts at about 6 psi boost with 70 psi injection line pressure, and ramps up to 100 psi by 16 psi boost. So, now you have not only a new fuel mix, it is also changing. Trying to tune using conventional wisdom with target A/F values is a bucket of worms that may have no practical solution. It's even tougher, when there is no access to an AWD dyno.

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