Tom Wilson
March 1, 2013
Cooling intake air temperatures pays off. Using a stock engine tune simply adding water/methanol from a Snow Performance kit chilled the Laguna Seca’s inlet air 23 degrees, thus adding 1 degree of ignition timing and 8 hp. Dyno-testing was performed on Rocky Mountain Competition Research’s Dynojet in Colorado Springs, Colorado.

Water injection has been around forever, but after going in and out of fashion for decades, it's gaining a firm foothold in the performance-car world. A big reason is Matt Snow at Snow Performance is dedicated to educating the world that water is less expensive than race gas, and almost as easy to install. His line of computer-controlled water/methanol injection kits has proven popular with supercharger fans where boosted induction air temps are hot enough to bake a turkey, and now he's showing naturally aspirated powerplants benefit from water as well.

So what is the big deal with water injection? It sure doesn't sound like a good way to build a big fire in the combustion chamber, after all. Well, in a nutshell, that's the point. With high compression, boost, or low-octane gasoline (and by that we mean any modern pump gasoline) it's easy for cylinder temperatures and pressures to spike over safe levels. The classic hot-rodding ways of avoiding momentarily excessive cylinder pressures are to raise the fuel's octane, lower the compression ratio, lower blower boost, or retard ignition timing. Obviously all of these reduce efficiency and cost power, but can be necessary to avoid engine damage.

But spray a little water into the intake stream at the right time and peak combustion pressures are lowered as well. The water changes state into a vapor, absorbing heat in the processes. Voila, it's as if your pump gasoline was suddenly C16 race juice. What little space the water takes up in the air-fuel mixture is more than compensated for by the ability to retain advanced ignition timing, boost or what have you. And just a little water does the cooling trick, without quenching the main combustion by any meaningful degree.

Even better than plain water is a 50/50 mixture of water and methanol. In car circles this is often referred to as simply water or water/meth, while over at the airport it's called anti-detonation injection. The flyboys were the first to put methanol in the water to reduce freezing at altitude, but everyone has found methanol has an evaporative cooling property, and unlike water, is also a high-octane fuel so it actually gives a little urge to the mixture. The fuel component of methanol is not a primary factor when running small amounts of water, but as the boost and power go up, it can help retain some power.

Obviously, the hotter the intake charge, the more effective the water/methanol injection, which is why it's a natural for blower motors. The water is sprayed into the mixture downstream of the blower where intake temps are highest, giving the maximum evaporative effect. But as Snow Performance's testing shows, water/meth is useful on naturally aspirated engines as well. This is of practical use on endurance applications where the engine runs at WOT for extended periods-in other words, at open-track or road race events where the fun typically lasts 20 to 30 minutes at a time.

In such applications, water injection is used not so much to boost power, but to retain power by not heat-soaking the engine, causing the engine management to retard the ignition timing either because the software says to at elevated coolant temperatures or because the knock sensors are hearing things. If you've tracked your Mustang and sensed it was getting lazy as the session went on, then you know what we're talking about.

To put some numbers to it, Snow Performance ran a series of chassis-dyno tests, plus some instrumented road miles, to document what their water/methanol kits can do on a naturally aspirated 2012 Boss 302 Laguna Seca. And just to maintain everybody's attention, they also included a 50-horse shot of nitrous in their test program as well.

Full results are in the data, but to sum it up, the Snow kit cooled the air charge 22 to 23 degrees on average and delivered an extra degree of ignition timing and thus extra 8 hp with no tuning whatsoever when running naturally aspirated. With the whiff of dry nitrous-meaning no extra fuel was added-the cooling effect was the same, making the super-simple nitrous hit safe and effective, as the medicine adverts like to say. That's tremendous cooling.

The only curious result was the combination of nitrous and water injection didn't result in any greater cooling effect than with the water alone. One explanation is the general trend during these tests was for the intake air temps to continue to drop at the end of the test when the water had already quit flowing, clearly a lag in the data stream. This suggests the water cooling effect could be even greater at the track where the full-throttle applications are longer than a dyno pull, especially with nitrous, where the engine accelerates that much faster.

Given that Snow Performance has worked out the details of water injection, the resulting user-friendly injection kits would seem natural for open-track Mustangs, blown or not. The charge cooling gained certainly delivers peace of mind - not to mention extending the horsepower fun to the entire open-track sessions.

Horse Sense: Water injection was highly developed in World War II as a power enhancer for supercharged airplane piston engines. Today that heritage continues development at the hands of Reno air racers, who have abandoned air-to-air charge cooling in favor of even more water injection in their 4,000hp V-12s.

Road-Course Nitrous
Over the years we've seen a few nitrous systems designed for road course duty. Mainly these were 75-plus-horsepower hits staged to ramp up once full throttle was reached. Great in theory, these systems couldn't offer the fine throttle response a road racer must have, and instead offered something more like "nitrous lag." They gave a useful thrill on big tracks with few corners but were too notchy on tight tracks with numerous on-off throttle applications.

Now Snow Performance reports simple nitrous systems showing up at open-track events. These are nothing more than the nitrous bottle plumbed into the intake tract with a 50hp nozzle. No additional fuel is added; such dry systems rely on a stock engine management computer's tendency to run rich at WOT. That's crafty but dangerous thinking in our book. It's the sort of thing stock-car racers have been known to do when qualifying for a particularly important race (the bottle goes in the leg of the driver's suit).

Naturally, the worry with such a basic system is running lean, but Matt Snow says his water injection system provides a good safety net in these cases. The water and methanol act as both coolant and fuel to match the nitrous' oxygen.

And are we seeing the term dry nitrous system migrate from it's original meaning where it denoted an arrangement that blew nitrous into the intake tract and the additional fuel via the engine's injectors rather than adding an additional fuel nozzle in the intake tract? If so, we'd prefer something like nitrous-only to denote these new helping hand systems.

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On The Dyno

NA Snow Nitrous NA vs. Snow
RPM Power Air/Fuel Power Air/Fuel Power Air/Fuel Power Air/Fuel
2,750 161.82 14.14 165.72 14.34 160.95 14.64 -0.87 0.50
3,000 176.53 13.36 179.69 12.94 175.96 13.33 -0.57 -0.03
3,250 195.10 13.01 198.12 12.62 193.58 12.67 -1.52 -0.34
3,500 209.82 12.95 213.36 12.56 207.89 12.42 -1.93 -0.53
3,750 228.75 13.03 232.29 12.64 226.19 12.60 -2.56 -0.43
4,000 248.00 13.13 251.08 12.84 244.55 12.73 -3.45 -0.40
4,250 270.00 13.18 272.51 12.88 265.47 12.73 -4.53 -0.45
4,500 288.92 13.25 292.99 12.88 295.46 12.71 6.54 -0.54
4,750 306.26 13.21 309.50 12.62 340.11 12.92 33.85 -0.29
5,000 321.72 13.15 325.11 12.50 355.31 12.80 33.59 -0.35
5,250 338.57 13.14 345.74 12.66 379.02 12.80 40.45 -0.34
5,500 356.07 13.21 360.72 12.77 395.72 12.87 39.65 -0.34
5,750 362.36 13.30 368.47 12.93 405.22 13.04 42.86 -0.26
6,000 367.39 13.39 376.47 13.06 410.48 13.06 43.09 -0.33
6,250 374.71 13.32 382.20 13.08 419.87 13.07 45.16 -0.25
6,500 377.20 13.36 385.44 13.07 423.98 13.17 46.78 -0.19
6,750 377.95 13.34 385.66 13.09 424.20 13.08 46.25 -0.26
7,000 371.25 13.31 381.71 13.18 423.77 13.05 52.52 -0.26
7,250 368.42 13.30 379.41 13.19 427.30 13.16 58.88 -0.14

Snow Performance's test vehicle was a 2012 Boss 302 Laguna Seca set up for NASA High Performance Driving Events (open tracking). Modifications included Hoosier racing slicks, adjustable shocks set firm, a Snow Performance Stage-3 Boost Cooler water/methanol injection system, along with a 50hp dry nitrous system.

Additionally, Snow Performance dyno tested the Boss' standard and TracKey tunes; there was the most minimal changes in power so we aren't bothering with those results here and are using the TracKey tune as the baseline. In other words, this was a typical open track car in that the engine was not supercharged nor even highly tuned.

Snow Performance's first test was to document how much reduction in intake air temperature occurred with water injection. This test was done on the road, with the engine temperature verified at 210, then accelerated in second gear between 2,000 and 7,500 rpm.

Measuring the intake air temp before and after the water injection took a little doing. The incoming air temperature information was captured from the car's stock IAT sensor using a DiabloSport handheld device. The IAT sensor is mounted before the throttle body and water injection nozzle, so it essentially reads ambient air temperature.

To measure the air temperature downstream of the throttle body and after the water injection nozzle Snow thought they could use Ford's second air temperature sensor on the RoadRunner engine. It's appropriately placed in the intake manifold, but Snow found that accessing its data with the Predator meant running afoul of the engine's stock tune. Therefore Snow added its own thermometer, a laboratory-type Omega thermometer fitted with a K-type temperature probe. The intake manifold was drilled and tapped to accept the probe's ¼-inch NPT temperature probe, which protruded into the air stream. It's believed this helped speed the temperature probe response time, rather than relying on the stock probe which is buried in the intake manifold casting.

Still, Snow Performance found a slight delay, or possibly a lingering cooling affect, as the charge air continued to drop after the water flow had been shut off. This could be continued quenching as it can take a little time for all the water to change state from liquid to vapor, which is when the cooling takes place.

And there's plenty of cooling affect, as shown by the results.

On The Dyno cont.

Run Description Start Temp End Temp Change Avg. Change
1 Stock with TracKey 99.5 102.2 2.7 0.75
2 Stock with TracKey 104.9 103.7 -1.2
3 Add Water/Meth 114.6 89.8 -24.8 -23.25
4 Add Water/Meth 95.0 71.2 -23.8
5 Add Water/Meth 109.4 81.5 -27.9
6 Add Water/Meth 87.0 70.5 -16.5
7 Add W/M and 50hp shot 115.0 94.1 -20.9 -19.88
8 Add W/M and 50hp shot 105.0 84.8 -20.2
9 Add W/M and 50hp shot 99.4 76.9 -22.5
10 Add W/M and 50hp shot 100.0 84.1 -15.9

We're not sure why, but perhaps the nitrous doesn't allow as much of the water to change state because the nitrous cools the water

A few things stand out to us from this test. For starters, at first glance there's little to choose from in the baseline tests. Inlets and intake manifolds are somewhat air cooled, at least when the throttle is open and large volumes of hopefully cool ambient air is passing through. It seems here that the first run was with a cool engine that warmed up making the first pass, then cooled the inlet marginally on the second run with fresh air. It's also likely that intake air temps didn't rise any more thanks to this fresh-air cooling, as it were, and it's also just as likely that once the engine compartment heat soaks at an open-track that some of this air cooling effect goes away. None of this was enough to matter in this brief test, but it illustrates what happens to the inlet air in a heat-soaked engine compartment during a 20-minute open-track thrash as the starting and ending temperatures were trending upward.

It's a different story when the water/methanol starts to spray, though. Snow's water/methanol system averaged a chilly 23-degree drop in inlet temps, which is definitely significant. This is definitely enough to avoid pulling ignition timing, and seems to keep inlet air temps about 18 degrees below ambient in Matt Snow's experience. Also, temperatures continued to drop after the run indicating a longer pull through more gears might result in lower inlet temperatures yet.

Add in the nitrous and the temperature drops are not quite as dramatic. We're not sure why, but perhaps the nitrous doesn't allow as much of the water to change state because the nitrous cools the water. But the combination does seem especially consistent, aiding tuning.

The second test was a traditional charge on a chassis dyno. The results are unambiguous: with water there's a bump in power all the way across the power band, and the nitrous shows a 50hp hit, as advertised. The trick is the water/methanol added a big safety margin with the inexpensive, simple nitrous-only system. With the methanol apparently acting like a touch of fuel to match the oxygen added by the nitrous the air/fuel mixture stayed at a safe 12.5:1, and it's thought the water may reduce the risk of a nitrous backfire.