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-   -   X98 vs 100% Meth WMI (https://www.jb4tech.com/forums/showthread.php?t=49926)

kfardan 06-29-2020 09:55 PM

My personal experience on the N55 engine is 100% Meth made more power than 100% E98.
The car did however feel just a little bit smoother with E98.
I tried even mixture of both maybe 70-60% Meth and the rest E98 .. made almost same power as 100% Meth.
So now I just stick with 100% Meth.

Might be different on B58 though, but give both a try and see which one works for you.

RMM 06-30-2020 07:59 PM

FYI I have BM3 with my own tune at about 25 psi, and e20 + 98, JB4 for meth, but no boost control, so I just run in map 0, with meth trigger set to 4.

Still running x98 on my car, I did try mixing in a bit more water again, like 25, 15, and it seems like at 25% I start to lose power, however the timing is perfect, so the water seems to be slowing the combustion down, or improving timing correction, but lose a little power.

I did increase the knock tables a little, and now have pretty consistent timing on both, however, there is a definite correlation to the % water, and timing corrections, so that would tell me that running more water is likely more safe for detonation.

One interesting comment, I have been adding more timing to my tune and , with more timing the power loss with added water is less noticeable. That supports my theory that the water is slowing the combustion and moving the MBT timing up. When I only had about 10-12 deg timing, adding 25% water was a noticeable and repeatable power loss like around 8%. However now with 14-16 deg timing, it is barley noticeable, or in the range of only 2-3%.

It may be that to get the benefit of the added water you need to add a few degrees of timing, but without a proper day of dyno testing I think that would be hard to know conclusively, as you would need to do many runs to compare different water % and different timing tables.

KnifeEdge87 08-30-2020 06:13 PM


Originally Posted by AWSAWS (Post )
I can give you some scientific data.
Methanol takes way more energy to vaporize than ethanol
You can burn about twice as much meth for the same amount of air as ethanol so methanol makes more power.

Water takes way, way more energy to vaporize than methanol. So...

Hate to dig up an old post but the above is scientifically inaccurate

For the same amount of air the energy released by ethanol and methanol for combustion is almost identical. Enthalpy of combustion is 1367 kJ/mol for ethanol, 726 kJ/mol for methanol so once you consider that for the same amount of air (always the limiting factor) you burn twice as much meth but meth produces half the energy, the result is more or less the same.

The WMI being injected also doesn’t actually vaporize in the intake charge (at least not by much), it atomizes (tiny liquid droplets as opposed to undergoing state change to become a gas). So given the amount of this fluid undergoing state change is minimal, the specific heat capacity is the metric we want to use, not the heat of vaporization. Specific heat capacity of ethanol and methanol are almost identical so there’s very little if any benefit for one versus the other.

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