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Old 06-09-2013, 01:11 AM   #1
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Default Requesting advice - AFR's and water-methanol

I have an M45 supercharger with crank overlay pulley, DIYPNP, and recently installed water-methanol system with the nozzle right before the throttle body/ supercharger. I am trying to optimize this setup for awhile before going to a turbo in the future.

For this year I added the DIYPNP and crank overlay. It's running about 10PSI towards redline, starts at 6PSI around 4,000RPM.

It makes a lot of heat at these levels, so I added the water-methanol recently. I prefer it versus an FMIC because I don't want to invest too much into the M45 and think a turbo system would merit a bigger core.

So far, I am using -20F washer fluid, which is approx 30% methanol. I have tried the medium nozzle and small nozzle. The medium nozzle keeps my temperatures at 100F over ambient during long pulls, and the small nozzle is at about 140F.

Without any w/m spray, my AFR targets at WOT are 11.8, and my tune gets very close, possibly 1-3 tenths rich. There is a rich spot in the 4k-5k range that I'm working on.

With either nozzle, my AFR's sink to 10.0 immediately and possibly climb to the low 10.X's very close to redline. I have tried backing off the start PSI/full PSI flow settings, but then the cooling effect on my AIT's drops off. I will typically accelerate from 3.5k-6k or so during testing, and it sits at 10.0 the entire time.

I'm trying to understand what is going on and if there is something seriously wrong. From what I have read, cars such as WRX's see an AFR shift of 1 unit with 50/50 water-methanol. I checked the nozzle spray, and it does seem to give nice atomization.

Please let me know if you have any advice on this. Is it possible that the methanol is enough to really richen up the mixture that much? It seems like I would need to pull a lot of fuel to get back to 11.8 or even somewhere above 11. Could it be something else like a sensor problem?

My next thought is to run 100% distilled water and check for cooling and AFR changes.

Overall, I would really like to stay no more than 100F above ambient, which is what I had with the medium nozzle and would probably mean a lot of re-tuning were it to be with 30% methanol.
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Old 06-09-2013, 02:51 PM   #2
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Are you spraying pre or post blower?
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Old 06-09-2013, 03:27 PM   #3
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My next thought is to run 100% distilled water and check for cooling and AFR changes.
That's what I'd do. If you still see an AFR shift, then it's an issue with your temp corrections. If you don't, then you know it's the methanol shifting the AFRs and you can adjust appropriately.
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Old 06-09-2013, 04:00 PM   #4
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Are you spraying pre or post blower?
Pre-blower. It gives a nice cooling effect for the blower and allegedly increases its efficiency by creating a better seal between the rotors. The air itself might be cooler were I to spray post-blower, but then the blower could become incredibly hot.

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That's what I'd do. If you still see an AFR shift, then it's an issue with your temp corrections. If you don't, then you know it's the methanol shifting the AFRs and you can adjust appropriately.
Thanks for the input. I didn't think of the temp. corrections; I had adjusted them when I tuned the car and thought they were pretty good, but WOT pulls may not have been in this temperature range before. Seems like I would need to pull quite a bit of fuel.

I will try to test it with distilled water tonight.

Any opinions on whether it is preferable to run distilled water versus water-methanol? Methanol could require pulling fuel and increasing risk if the system fails, but it may give better cooling. I am not looking to change the timing table if using methanol, which might be where the primary benefit of methanol would be.
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Old 06-09-2013, 05:54 PM   #5
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Primary benefit of the meth is to increase the timing that the increase in octane lets you do.
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Old 06-09-2013, 06:12 PM   #6
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Primary benefit of the meth is to increase the timing that the increase in octane lets you do.
Thats the primary benefit of the water, its an anti-detonate.

The only benefit of the meth is that it is more volitile creating a drop in IAT. The real reason it was mixed in in the first place was to prevent the mixture from freezing when used in aircraft and to provide fuel enrichment in boost. With modern fuel injection being used at above freezing temps there is no reason to use any meth.
A little alcohol is good to add to prevent algae bloom.
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Old 06-09-2013, 06:21 PM   #7
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Well yes and no. The water lets you run more timing because the charge is cooler and because a damp charge is slightly harder to light off. With the same charge temp meth lets you run more timing than straight water because it raises the octane of the mixture.
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Old 06-09-2013, 07:24 PM   #8
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Speaking from both personal experience and NACA reports:

I'm spraying post-turbo.

With 100% water, I see almost no charge cooling. There simply isn't time for the water to change phase before being ingested in the cylinder. However, water provides about double the "octane" boost that methyl alcohol does. This is because the latent heat of water is about twice that of alcohols.

With 50-50, I see some charge cooling. This is because the alcohol is able to phase change much more rapidly than water.

The main reason to do post-compressor WI is to increase timing due to the "octane" effect. If you are looking for charge cooling, nothing is more effective than an intercooler. I will say that OP's charge cooling spraying pre-compressor with alcohol (100F cooling reported) is impressive, but still nowhere near what an intercooler would achieve.

If you do take advantage of the "octane" effect, automatic failsafes are absolutely required. My failsafe is to automatically disable EBC and drop to wastegate-only boost.
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Old 06-09-2013, 07:36 PM   #9
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Any opinions on whether it is preferable to run distilled water versus water-methanol?
If what you are after is charge cooling, then the more meth the better. Water takes a lot of energy and time to change phase.
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Old 06-09-2013, 07:59 PM   #10
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If what you are after is charge cooling, then the more meth the better. Water takes a lot of energy and time to change phase.
But that heat energy is absorbing is still heat its pulling out. Changing phase doesnt instantly pull heat out, that latent heat you're talking about IS the heat it pulls out as its getting ready to phase change. Once its pulled out its latent heat value it phase changes. But if one has a better heat transfer coef then that one will absorb the heat energy faster.
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Old 06-09-2013, 10:43 PM   #11
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Leafy, ever heard of psychrometrics? Ever wonder why you have to constantly drain water from your air compressor?

Water doesn't do squat to drop intake temps. Actually, it may do a little if you inject pre-turbo like OP. But nothing like alcohol.
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Old 06-10-2013, 12:05 AM   #12
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Thanks a lot for the help, guys. I have really appreciated the advice, especially since this has been a pretty frustrating problem.

I tested it with 100% distilled water tonight.

Savington nailed it - I was still running 10.0 at wide-open throttle. I adjusted the MAT correction table to get out of that condition.

Also, I found that the water did not cool as well as washer fluid. It still did offer cooling, but I think it was overpowered by the heat of the blower while the washer fluid would cause the IAT to peak.

What I am now stuck on is why this happened. With absolutely no fluid being sprayed, my AFR's were fine at wide-open throttle. With spray, I had to pull fuel in the MAT table to get the AFR's to the right level. The temperatures are different, sure, but not hugely different, and still fall within the temperatures I have been running. Is the density of the air and/or presence of vapor also playing a role? Should I be adjusting the VE table?


Also, I know that an intercooler would be the ideal method for charge cooling, but I would prefer to wait until swapping to a turbo system to add an intercooler. The reason would be that turbo's function well with larger intercoolers while superchargers need minimal throttled volume, so I would wait until converting to a turbo system to set one up given its different requirements.
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Old 06-10-2013, 01:25 AM   #13
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Quote:
Originally Posted by hornetball View Post
Speaking from both personal experience and NACA reports:

I'm spraying post-turbo.

With 100% water, I see almost no charge cooling. There simply isn't time for the water to change phase before being ingested in the cylinder. However, water provides about double the "octane" boost that methyl alcohol does. This is because the latent heat of water is about twice that of alcohols.

With 50-50, I see some charge cooling. This is because the alcohol is able to phase change much more rapidly than water.

The main reason to do post-compressor WI is to increase timing due to the "octane" effect. If you are looking for charge cooling, nothing is more effective than an intercooler. I will say that OP's charge cooling spraying pre-compressor with alcohol (100F cooling reported) is impressive, but still nowhere near what an intercooler would achieve.

If you do take advantage of the "octane" effect, automatic failsafes are absolutely required. My failsafe is to automatically disable EBC and drop to wastegate-only boost.
^This

There is a lot of misunderstanding about "Meth injection" because of the stuff that these kit companies say. Its pretty sad but I dont think they even know how this **** works, theyre just selling some rebranded agricultural pumps and counting their profits.

The NACA study on "internal cooling" is where the fundamentals of water/meth injection originated. They were using it on carbuerated aircraft engines with forced induction and no intercoolers. They found that the added fuel was necessary because it was lowering AFR, which as we know will help prevent detonation to a certain point, because they wanted to keep the mixture fro freezing at high altitude and to lower the insanely high temperature non-intercooled charge.

Now we have fuel control that they couldnt even imagine in the 1940s. So NACA's suggested 50/50 mixture is pointless. I would rather have my fuel injection system control the injection of fuel, not sharing the load with a a pump and garden hose nozzle. Plus if you tune the meth into the fuel map, then if the water/meth injection system fails, not only will you not have the water but you will also be running lean on top of that.

This myth needs to be put to bed.
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Old 06-10-2013, 01:42 PM   #14
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Originally Posted by mc85 View Post
What I am now stuck on is why this happened. With absolutely no fluid being sprayed, my AFR's were fine at wide-open throttle. With spray, I had to pull fuel in the MAT table to get the AFR's to the right level. The temperatures are different, sure, but not hugely different, and still fall within the temperatures I have been running. Is the density of the air and/or presence of vapor also playing a role? Should I be adjusting the VE table?
I don't know the answer to your question. However, if you use MS for WI control, the MS automatically disables EGO corrections when spraying because it expects the AFRs to be inaccurate (note, you would probably be running open-loop at those boost levels anyway). So the effect is known.
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Old 06-10-2013, 08:28 PM   #15
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I don't have a way to control the WI via MS at this time. Currently using the PWM controller that the AEM system came with, with a LED indicator on the dash to indicate pump on/pump speed/low fluid/etc.

Since adding WI and adjusting my MAT correction, I am close to hitting AFR targets at WOT from 5k-redline, but I am running rich from 4k-5k and at part throttle; in other words, I need to fix my VE table. I struggle with if (and how) this was caused by WI, or if it was there all along and WI helped me find it. I suppose that my car now runs at intersecting conditions of [MAP, AIT] that it has never seen before...?
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