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Water Ethanol Injection

Road Tuning

Discussion and questions related to the course Road Tuning

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I need a little advice on tuning with EU 98 Octane fuel (US 93) and water / ethanol injection.

In my country, methanol is illegal and whiperfluid contains ethanol. Therefore i am using 50/50 water ethanol. (Measured the actual ethanol content to be 50%)


BMW M50 2.8L Inline 6

9.0:1 CR

240 deg 9.7mm - both cams set to 0.5mm overlap at TDC.

Snow Performance injection kit with 625cc nozzle at 25cm before the throttle body.

Precision 6266 AR.81 turbo.

Ecu Master EMU Black

Timing is verified at idle and 6000rpms.


1 bar of boost and 4300rpm the knock limit is 8 deg.

1 bar of boost and 5500rpm and above, 16 deg of timing dosent knock at all. So the timing curve seems strange to me.

I am using both EMU knock detection and knock ears.

Adding the water ethanol injection - lambda drops from 0.78 to 0.7 and i am pulling 22% fuel to get back at 0.78.

When meth is spraying its actually loosing power. 30nm aprox.

Power is picked up again when increasing timing. 6 deg increase from 4500rpm - 12 deg increase at 5500 and above. This was done on a dyno.


It could sound like i am spraying too much?

Does others experience power loss the same way as i do?

Should i increase ethanol content? As the ethanol i am using is 92% before blending with water.

Any tips is much appreciated.


Mustang dyno showed 465WHP / 520WNM @ 1.4-1.5 bar boost.

I did really expect it to make more power than this, comparing other m50s on the 6266.

It is not uncommon for water/alcohol injection to result in lower power before you make adjustments to the tune. The water/ethanol injection can on some engines slow down the burn, meaning you need more spark to get equivalent, and also affect lambda.

I would add spark until you reach whatever you feel is the safe knock limit. Also, you can run a leaner lambda than without the injection. However, you still need to be careful. You can still damage something, and as you add spark or lean out the risk increases.

Well, simply adding methanol won't make any power, of course, that's why you compensate by advancing the timing, as Arghx7 already mentioned.

I will simply paste this here FYI, a very nice insight into water/meth spray, also the source

-The proper mixture of water/methanol to inject:This is debated a lot, but it generally ends up being 50/50 by mass, not volume. Sorry guys who are mixing your own and filling two jugs equally, you failed -- you should have used a scale. Methanol is about 74% the weight of water, so if you thought you were running 50/50 and you measured by volume, you're actually running around 37% methanol to water. DOH! Don't worry though -- if you're not detonating, then you're in the money, because all that extra water is there to cool the combustion event and perhaps the boost charge as well, especially if it's hot enough and has some distance to travel (see turbo piping and high boost supercharger.) Ideally, in my opinion, you'd run the perfect mixture that had just enough methanol to up your octane rating enough to ward off detonation with the cooled combustion event -- this is because the water cools better than methanol. If you run 35/65 (-30F washer fluid, what I used to use), and it prevents all detonation, moving to 50/50 would just add octane while removing cooling ability. This is why I never messed with mixing before I went to 11 pounds. Now that I'm here, one 100+F day and I detonate a little -- time to add more octane. By running 35/65 instead of 50/50 when that was all I needed, I cooled the combustion event (and to some degree, the charge) quite a bit more. Remember that the methanol that cools is what is left over, so more water means more cooling, not only because it cools better than methanol, but because it isn't burned. The methanol is still burned, and the remaining methanol from running rich is all that is left to cool! This is why I'm so against people running more methanol than they need -- not only is running pure methanol dangerous, it's not required most of the time. Any methanol you can replace with water means more cooling and less flash danger. Seems obvious now, but good luck convincing some folks.

-The proper ratio of spray to fuel:Generally speaking, you want to be around 20 - 25% spray to fuel. any more and you could potentially (so I've heard) wash water down the cylinder walls and contaminate your oil sooner than you change it. Personally, I don't put too much faith in this since we squirt a lot more fuel in there, and the methanol burns too, so it should (in my head) just depend on how much water you're shoving down there. I have about a 25% spray to fuel ratio on average in my power band (less than 25 at 8500 rpm, more than 25 at 6k rpm.) You can determine the proper amount by calculating the fuel you use by multiplying your injector size * 4 then factoring in your duty cycle. Injectors are rated at 43psi from rc, and we run around 51 pounds of fuel pressure, so the injector flow is a little under what it's rated, but that changes with your boost curve, so close is good enough. For example, if you have a duty cycle of 60% on 650cc injectors in the middle of your powerband (say 7400 rpm), that's 650 * 4 * .60 = 1560 cc/min of fuel, so your methanol jet should be spraying at 1560 * .25 = 390 cc/min. If you are unsure about your jet, it's easy to flow test -- just take an empty oil bottle and point your jet there, trigger your pump, let it go for 30 seconds, let the foam settle, then multiply the ml by two for ml/min and there you have it (one ml is one cc, for those who didn't know).