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KnifeEdge87 KnifeEdge87 is offline
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Default Water injection vs WMI - 08-24-2020, 07:21 PM

Is it possible to use 100% distilled water?

What would the cost/benefit be from doing this? (Stuff growing in the tank from not having something preventing growth?)

Water absorbs heat twice as good as meth (latent heat of vaporization is 2.2j/g for water vs 1.1 for meth), specific heat capacity (by mass) is 4j/g for water vs 2.5j/g for meth, all this gets worse for meth when you consider itís less dense than water so thereís actually much less of it in a given volume.

I keep hearing meth has AntiKnock properties ... but so does water, thatís the whole point of water injection, Reduce temps to reduce knock So you can advance timing...

Meth of course is a fuel so you can combust it with more oxygen (but if you had that excess oxygen already, then you can combust it with petrol/gas as well, the ďbenefitď from meth as a fuel only exists if your fueling system is underspecíd, meth cools better than petrol, but water cools better than meth)
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JBoe JBoe is offline
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Default 08-29-2020, 02:54 PM

The issue is that water isn't combustible. Thus, it's additional won't provide the larger gains most are looking for. To up the boost you need the supporting fuel and octane. Meth provides both. That's why most run a mix. Best of both worlds... However, as you mentioned, some have fuel limitations. Thus we use 100% Meth as it better suits the setup. In the end, it's about removing the limiting factor or at least shifting it to a point where it's not an issue because you're satisfied.


AFE Drop-in Filter
BMS Meth Kit (100% M1)
Muffler Delete
CA 91 Piss Gas...
(8oz Boostane 95ish Oct)
E85 (2Gal/Fill)
BEF (Race_WMI)
JB4 (Map 7 - Add 45... 19-20psi)
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KnifeEdge87 KnifeEdge87 is offline
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Default 08-29-2020, 08:08 PM

The primary job of wmi isn't to add fuel though (if it was the M4 GTS' water injection wouldn't do anything)

It's to lower the intake air temperature so you can run more aggressive boost /timing

Unless the stock fueling system is the limitation I.E stock injectors/pump can't deliver enough fuel to make >350bhp regardless of how much air the turbo is capable of providing (which it could well be the case, in which case meth definitely solves the problem)

I guess if enough people are doing it there must be a reason...

It's not an unusual thing for stock fueling systems to be the limiting factor. In the Mazda MX5 space I know the fueling system is one of the first things that begin to limit power increases once you get forced induction in the mix. For some reason I just didn't expect that to be the case for the B48 given it shares components with the B58, maybe the fuel pump is capable but the stock injectors can't keep up...
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JBoe JBoe is offline
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Default 08-29-2020, 10:57 PM

No one is stating that water injection isn't used to lower temps and help improve timing. The engine and turbo setup is designed around it's known components. Compression ratio, heat dissipation, intake flow, etc. Then you have to add in a layer of safety to ensure warranties can be maintained. The M4 falls into this category.

When the water level is low/empty power is reduced as the overall setup is made in a way that requires it's benefits to have max safe performance. Same goes for our setups. While we cut into the safety net to increase performance, we can only go so far before reaching limits. Options to get pass those limits vary, but WMI fits for most. Our setups respond better to octane than just cooling the intake charge, even though we wish we can have both. Thus, most default to what's needed and go full Meth or even E85.

At some point, once again we hit limits. Turbo compressor efficiency, fuel pump, etc. Thus, we upgrade more. It's a vicious cycle... Lol! Your question was originally around why we don't use straight water and if it's safe to do so. It is safe, but it will only provide so much. Unfortunately, most of us aren't satisfied with what pure water can provide given our setup's design. So we opt for what does work, even though we may give up some cooling and timing. The new levels mix of higher boost, more fuel and increased (not maximized) cooling charge, result in higher whp/wtq levels. It's all about finding the combos that work best for the application.

Hope that helps clarify my response to your answer as why we choose the paths we have.


AFE Drop-in Filter
BMS Meth Kit (100% M1)
Muffler Delete
CA 91 Piss Gas...
(8oz Boostane 95ish Oct)
E85 (2Gal/Fill)
BEF (Race_WMI)
JB4 (Map 7 - Add 45... 19-20psi)
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KnifeEdge87 KnifeEdge87 is offline
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Default 08-30-2020, 12:19 AM

Yeah

That’s basically what I was trying to get at. If I run straight water it would not give as much performance as water/meth but I was trying to get an idea of how much difference it would be.

So on a B48 with a down pipe, BEF, and either Water or Water+Meth. What’s the difference we’re looking at?

Honestly I’m not even sure how much WMI alone provides (assuming BEF already completed + hi-flow catted DP).

You’re of course correct that everyone has different requirements/targets and would choose different systems to achieve that goal. If for example, water injection only provides say 15hp increase whereas WMI would provide 50+hp increase in the same scenario, I think the meth/water combo would be the way to go. But if it was like 40 vs 50 then I’d rather give up the 10hp and take the convenience of only needing distilled water.

Reason I ask again is that in Hong Kong it’s a bit of a pain to get meth for the system. The shop that sells this kit locally can provide but not only is it quite expensive (~30USD per gallon of 50/50 mix) it’s actually quite inconvenient for me to go there to get it. Boostjuice from Summit Racing is I think 40USD for 4 Gallons so 3x price difference for a consumable is a bit tough to stomach.

If I was in the states I think I would go WMI no questions asked but my particular situation is a bit more nuanced just because of the difference in marginal cost.

Obviously this is very different depending on the setup but may I ask for you how long a gallon of meth mix lasts you ? I would expect in most setups that the system never activates in normal commuting driving and only during “spirited” drives so I guess the most appropriate measure is “# of fun miles per gallon of meth”.
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JBoe JBoe is offline
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Default 08-30-2020, 08:53 AM

I have a 2gal tank and top it off every month or so. It's never empty. I purchase it in 5gal cans. That's been lasting me roughly 6-7 months. I tend to drive in sport+ and semi-aggressive unless in congested traffic or on a long highway cruise.

I haven't seen anyone run straight water and tune for it. You'd be breaking new ground there. With 50/50 you should be over 400whp. With 100% Meth at 20psi I'm at 460ish whp depending upon temps. It's been 100+F in my area of SoCal, thus it drops power a bit. Still way more than when I was running 50/50 mix.


AFE Drop-in Filter
BMS Meth Kit (100% M1)
Muffler Delete
CA 91 Piss Gas...
(8oz Boostane 95ish Oct)
E85 (2Gal/Fill)
BEF (Race_WMI)
JB4 (Map 7 - Add 45... 19-20psi)
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Mike_L Mike_L is offline
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Default 08-30-2020, 01:46 PM

400whp on a B48? I don’t think so. B58, yes, but certainly not the 4 cylinder. Even 300 at the wheels would be pushing it with just computer work and DP and WI.


Mike Levy
2021 Tanzanite Blue II M550i xDrive
2018 Silver Equinox LT 2.0T
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JBoe JBoe is offline
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Default 08-30-2020, 03:17 PM

Quote:
Originally Posted by Mike_L
400whp on a B48? I donít think so. B58, yes, but certainly not the 4 cylinder. Even 300 at the wheels would be pushing it with just computer work and DP and WI.
Forgot it was B48. Yes, I'm speaking for B58. While levels aren't that high, it provides a range comparison and answers what usage of Meth would look like.


AFE Drop-in Filter
BMS Meth Kit (100% M1)
Muffler Delete
CA 91 Piss Gas...
(8oz Boostane 95ish Oct)
E85 (2Gal/Fill)
BEF (Race_WMI)
JB4 (Map 7 - Add 45... 19-20psi)
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KnifeEdge87 KnifeEdge87 is offline
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Default 08-30-2020, 06:48 PM

Yeah 300whp sounds about right.

A good BEF with a catted hi flow DP would be alone about 300BHP and WMI & excess boost probably adds an extra 30-40hp or so on top so at the wheels 300hp seems reasonable.
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KnifeEdge87 KnifeEdge87 is offline
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Default 08-30-2020, 07:24 PM

BTW I think i know why most B48/B58 don’t “like” water injection. I have a hunch it’s because the IATs simply are not that high ?

In the M4 their marketing material states (i haven’t checked any M4 logs to verify) that the IAT without water injection is like 70c. For me in my B48 and many of the B58 logs I see IATs closer to 50c. So conceivably at 70c you get much more vaporization (state change to gas) so it removes quite a bit of heat from the intake charge, methanol will boil instantly at 70c but being an OEM system they probably felt the added danger of meth and liability concerns to not be worth it. On our B48/B58 water will just absorb a bit of heat whereas meth will still readily evaporate at 50c.

This is something I didn’t really consider in my analysis way above ... which is alcohols have much lower boiling points than water ... stupid me right ?
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