Is a Water/Methanol Injection Kit the Tuning Aid You Need?

By Tom Suddard
Dec 4, 2022 | tuning, Methanol | Posted in Shop Work | From the Dec. 2015 issue | Never miss an article

The premise behind water injection is simple: Squirt a mixture of water and methanol–windshield washer fluid, basically–into the engine’s combustion chamber to cool the intake charge and prevent detonation. 

A few factors decide a given fuel’s detonation point: intake air temperature, ignition timing and cylinder pressure combination. Cylinder pressure can be developed by compression ratio, supercharging or turbocharging. If you can reduce one of the three variables, then you can increase one or both of the other two.

The water/methanol mixture vaporizes and cools the intake charge significantly, allowing you to increase the timing and boost. In layman’s terms, water injection can produce the same effects as high-octane race fuel–but without the cost or complexity of finding it at the pump. 

This technique has been around for decades, but it has only become a mainstream modification in the past few years. Credit more precise engine control systems with making water/methanol injection durable enough for everyday use. Additionally, companies like AEM now offer turnkey, all-inclusive kits.

Okay, so water/methanol injection is relatively easy to add. But is it really necessary? Here’s a handy guide to making that decision.

Step 1: Does your engine have a high compression ratio? Or is it fed by a turbocharger or supercharger? 

If your answer is “none of the above,” then water/methanol injection probably isn’t a wise investment. If you do have one or more of these things, move on to Step 2.

Step 2: Can you adjust your ignition timing and/or boost pressure?

Installing water/methanol injection without retuning your engine will usually cost horsepower, as the water replaces some of the combustable air inside the engine. If you can’t advance the timing, increase the boost pressure, or both, don’t bother adding water/methanol injection. If you can, move on to Step 3.

Step 3: Are you willing to void your warranty?

Manufacturers aren’t too fond of extra water inside their engines. And their caution isn’t unfounded: If the water/methanol injection tank runs dry–you may need to fill it up at every gas stop–then detonation and engine damage are likely. If there’s a malfunction, the engine could hydrolock. Basically, if you still go to your dealer for oil changes, water injection isn’t for you. If you’re just cautious, we suggest adding a failsafe mechanism to your system. AEM offers them with its kits.

Practical Exercise

Wayne Presley at Very Cool Parts has made more than a few trips to the dyno. He recently used a water/methanol injection system while tuning a Dodge SRT-4.

Click the chart to open it in a new window

We had a 2005 Dodge Neon SRT-4 in the shop for a fresh engine with forged rods, forged pistons, cams and ARP head bolts. It was being fed through an AGP 50 trim turbo with an AGP front-mounted race intercooler. 

After breaking in the motor, the tuning process on the dyno began with good results. The motor was pulling well through 18 psi of boost using 93-octane pump gas with no detonation. 

When I turned up the boost to 20 psi, the knock sensor started pulling timing to protect the motor, causing a drop in power that’s easy to see in the graph below. At the wheels, we were seeing 341 horsepower and 370 ft.-lbs. of torque. We expected more. 

We had already added the largest intercooler that would fit in the front of the car, but we needed to cool the manifold air temperature more. So,I added a water/methanol injection system. This was a system that progressively added more mix in relation to the boost level. I set the start point to 12 psi and ramped up to maximum flow at 18 psi. 

Thanks to the cooler intake charge, I was able to add ignition timing as well as increase the boost to 22 psi. The horsepower and torque climbed up to 395 and 401 respectively. That’s 54 more wheel horsepower with zero detonation, all while using the same 93-octane fuel. The only equipment change was the addition of the water/methanol injection. 

I highly recommend a system featuring a warning indicator or other failsafe to let you know if the system stops working for any reason. And use either the premixed water/methanol solutions or mix your own with distilled water. The orifices in the spray nozzle are very small, and tap water will have minerals in it. This will eventually clog the nozzle just like the hard water does to your shower head at home. When that happens, little or no mix is injected, and that extra boost and timing you’ve added to the tune might lead to some very bad and expensive noises.–Wayne Presley

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MrFancypants Reader
7/30/20 8:54 a.m.

Has anyone tried running E100 through one of these systems?

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) Dork
7/30/20 9:07 a.m.

You are better off using pure methanol or a blend from an evaporation, octane and detonation resistance point of view.

z31maniac MegaDork
7/30/20 9:15 a.m.
MrFancypants said:

Has anyone tried running E100 through one of these systems?

Why not just tune the car to run on E85 then? 

From what I understand most engines can already reach MBT with ~E60, so going all the way to E100 isn't really necessary. 

MrFancypants Reader
7/30/20 9:29 a.m.

In reply to z31maniac :

Ahhh, fair point.

MrFancypants Reader
7/30/20 9:30 a.m.
Paul_VR6 (Forum Supporter) said:

You are better off using pure methanol or a blend from an evaporation, octane and detonation resistance point of view.

So my thought about ethanol is that if you live you can get it at the same place you buy gasoline, making it super convenient.

slantvaliant (Forum Supporter)
slantvaliant (Forum Supporter) UltraDork
7/30/20 10:04 a.m.
Vigo (Forum Supporter)
Vigo (Forum Supporter) MegaDork
7/30/20 10:29 a.m.

The thing i always think about when trying to explain detonation is all the bomb-camera footage from Vietnam. You could pretty clearly see the pressure wave moving away from the center much faster than the actual flame front. I went ahead and edited out my political statement from the middle there before posting. 

Another thing that's interesting about a draw-through turbo setup like that Oldsmobile, or water/meth injection in general, is that at low-ish charge temps your ability to vaporize liquid in the fast-moving charge air is somewhat limited and you are generally just adding a 'safety margin', but as your charge temps go up you can actually vaporize so much liquid that you can stop using an intercooler. Seems kind of counterintuitive! There are a lot of really fast drag cars that inject a huge proportion of their fuel pre-turbo and drop their discharge temps from 500f to 200f roughly. Of course, 200f isn't a great number for a street car on pump gas, but if you're running high octane fuel and can only floor it for 6 seconds at a time without dying, it seems to work out! 

frenchyd PowerDork
7/30/20 10:31 a.m.

In reply to MrFancypants :

That has been my policy. Tune and  Run E85 with a back up of washer fluid for times when the E85 you get is less than 85% Ethanol. ( E85 can be as low as 51% ethanol at the pump)


  At those times  if you have a EFI system where you can dial back timing with a few key strokes, that's what you should do. But if like me you're dealing with distributors and carburetors you need a crutch. Hence windshield washer fluid.   
My Luddite solution will be to simply drive knowing the restriction and avoid high boost situations. If that's not possible I flip on the toggle switch and using a Kinzler  dial -a-jet  squirt in the proper mixture of WW fluid 

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
7/30/20 11:21 a.m.
Paul_VR6 (Forum Supporter) said:

You are better off using pure methanol or a blend from an evaporation, octane and detonation resistance point of view.

-Paul - 1992 Corrado SLC 3.6 VR6 11.38@120 ALLMOTOR ig:@needavr6

Pure water is itself an anti detonant, up to 2x the amount of gasoline injected in highly forced induction applications.  Ricardo was running incredibly high BMEP while lean of stoich, with the main limitation being the stength of his test engine and the limits of his dynamometer.

Methanol does a wonderful job of reducing charge temps (I have heard of 30+psi turbo engines on carbureted methanol with iced over intake manifolds after a pass) but because it is also a fuel, ultimately it CAN detonate.  What water brings to the party is that it is inert and interrupts the detonation process, similar to EGR.

Apexcarver UltimaDork
7/30/20 11:30 a.m.

Did some looking into it when researching blower stuff for my Mustang. 


Reasons to not go straight ethanol or methanol is that the mix they are using in those isnt combustible on its own, so you dont have to worry about it as much from a safety perspective. Saw a lot of articles on testing percentages of methanol and mixing to get it right, most of the washer fluids need a kick up.  Tuning is interesting as you are adding more fuel, so if you tune for it you run lean if you run out and could damage your motor. 


The show stopper for me is that SCCA flat bans it for autocross. I suppose they worry about someone torturing the alternative fuel possibilities of it and making a flammable mixture?  Either that or just plain rules creep, the alternative fueling could provide a performance advantage that would make it a "need to have to be competitive" thing. 

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