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Everything You Need To Know About Octane

All About Octane: What it is, how it’s done, and the best race fuels, concentrates, and alcohol injection kits on the market

Rick Jensen Sep 7, 2015 0 Comment(s)
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With neck-snapping beasts like the 650-horse C7 Z06 roaming around, factory performance cars have never been faster. Cheers to the Corvette team for cranking out that pump-gas power number, because that thing is flat insane.

The rest of us spend thousands to equal or exceed the supercharged LT4’s output. But normally, high-compression or boosted engine builds tuned for 91-octane street gas leave power on the table. If you want to add more timing or crank up the boost for more ponies, you’ll need more octane to keep that engine-killing detonation at bay.

And adding octane can also benefit our lightly modded Vettes, too. Since the high-octane glory days of the 1960s, premium pump gas octane ratings have dropped, and then leveled off in the mid-1990s. They also vary widely around the United States. I travel between the East Coast and the Midwest a lot, and seeing an NYC-area Sunoco station with an Ultra 93 pump gets me all tingly. Does that make me weird? Yes, but let’s see how you feel at rural Midwestern gas stations with 89-octane “premium.” Throw in the fuel quality and octane variances between different stations and tankfills, and you can understand why our thriving performance aftermarket craves octane-boosting products.

But deciding to add octane is easy—the hard part is deciding how to add it. For example, let’s say you decide to run race fuel: how much octane does your car need? Do you buy leaded or unleaded race fuel? Should you buy oxygenated race fuel or not? Is mixing race fuel with pump gas recommended, and if so, how much do you use?

And those questions are just about race fuel—there’s also race fuel concentrate to consider. And while alcohol injection is a slightly different solution to the octane equation, it also can solve your octane-deficiency problem.

All offer benefits and drawbacks, so we’re going to discuss each method in depth. And then you can go forth, head swimming in octane knowledge, to choose the best octane enhancer for your Corvette.

02 Rockett 100 Gas Dispenser 2/25

Race Fuel

Race fuel is the old guard of high octane—it’s been around for decades, it’s produced by numerous companies, and it’s available in many octane ratings and formulations.

It’s a fascinating concoction, so to further educate ourselves we reached out to two gentlemen with a combined 80-plus years of fuel experience: Jack Day, president of Rockett Brand Racing Fuel, and Tim Wusz, Rockett’s VP of engineering. These two made and sold race fuel at Union 76 during its NASCAR partnership, then started Rockett Brand in 2004. These days, Illinois-based Rockett Brand offers unleaded and leaded racing fuels with 100-, 110-, 112-, 114-, and 118-octane ratings, and E85 with a 112-octane rating.

Race fuel is comprised of fewer than 100 hydrocarbons: there’s maybe six prominent ones, and the rest are present only in small quantities. A good race fuel manufacturer only includes fuel components that will give desired qualities—high octane, a fast burn, good vaporization, and for leaded fuels, the ability to play nice with lead.

Compare that to normal pump gas: it is a mixture of several hundred hydrocarbons, with many of them occurring during the refining process. As they can’t be separated out, these components are just along for the ride—they burn just fine in non-race, non-high rpm engines anyway.

Race fuel is a fantastically complex product, but of course the first thing we all wonder about is its…

03 Rockett Brand Tim Wusz 3/25

Octane

A fuel’s octane number is its ability to resist detonation. And it’s important to note that octane isn’t power—the benefit to raising a fuel’s octane quality is only valid if the engine it goes into is detonating. The higher a fuel’s octane number, the more resistant it is to detonation.

An engine only needs enough octane to prevent detonation; if it’s tuned for 91-octane pump gas and has a slight ping on a hot day, filling up with 118-octane race fuel won’t add crazy horsepower.

Fuel has what’s called an anti-knock index, or AKI, which is calculated based on the average of two different tests: the research octane number (RON) test, and the motor octane number (MON) test.

The research octane number test consists of a single-cylinder engine that runs at 600 rpm. Using 125-degree F intake temperature and standard barometric pressure, this part-throttle test determines a fuel’s detonation resistance at light load.

The motor octane number test is more severe: the single-cylinder engine runs at 900 rpm, and breathes 300-degree F intake air. This is a heavy-load test that determines how a fuel will perform at wide-open throttle.

When buying gas at the pump, you’re choosing a fuel based on its AKI—the pump wears EPA-required decals showing (R+M)/2 and fuel grades like 93, 89, and 87. So as an example, clicking the “93” button means you’re selecting a fuel that might have a 97 research octane and an 89 motor octane. (97 + 89 = 186) / 2 = 93 octane.

But with race fuels, companies sometimes only list the MON number for fuels they consider “track only,” and can list the MON, RON, and R+M/2 numbers for street-friendly formulations. Both the MON and RON have value; however, unless you need to choose a race fuel based on its RON or R+M/2 number for a certain racing class, experts recommend that you base your fuel choice on its MON.

But Day adds an important last word on octane. “All racing fuels are not the same, or made the same way. Between two different brands of race fuel, the one with a higher octane number doesn’t necessarily mean that it’s a better fuel. You only need an octane number to satisfy octane requirement, but a quality racing fuel is about the entire package, not just its MON.”

04 Rockett Jack Day 4/25

Race Fuel Properties

Speaking of the entire package, let’s get into how race fuel works—we’ve already discussed motor octane, research octane, and R+M/2 values, so let’s cover a few more important properties of race fuel:

A fuel’s burning speed describes how quickly it releases energy. Different race fuels contain different amounts of additives, which affect the speed at which that fuel burns. This gets ultra-technical real fast, but basically, the goal is to create peak cylinder pressure (and power) for your specific engine type and motorsport.

Its energy value describes how much potential energy a fuel can make, and is measured in BTUs.

The cooling effect describes how well a fuel helps cool an engine’s intake mixture as the fuel goes from a liquid form to a vapor. Related to the heat of vaporization, cooling effect benefits all engines as it increases the density of the inlet air and therefore, improves volumetric efficiency.

Its specific gravity is the ratio of a liquid’s density compared to water, at a specific temperature. The specific gravity of race fuel can range from the .690s to the low .800s at 60 degrees Fahrenheit.

A fuel’s Reid Vapor Pressure (RVP) is a liquid fuel’s evaporation characteristics, measured in pounds per square inch. You’ve experienced RVP by buying summer and winter gas: summer fuels are blended to have 7 to 10 psi RVPs, preventing the fuel from evaporating in the summer heat (and creating high gas tank pressure and airborne pollution). Conversely, winter fuels can have RVPs of 10 to 14 psi, as there’s less chance of evaporation in cooler temps. A quality race gas has around 6 to 7 psi of vapor pressure; carbureted engines can’t have too light of a vapor pressure, or it can cause vapor lock.

Its distillation is a measurement of a fuel’s evaporation tendencies when heated. As fuel is a mixture of many different hydrocarbons, it will evaporate at different temperatures until the end point (E.P.) is reached. An example could be, “10% evap @ 141.0 °F, 50% evap @ 174.0 °F, 90% evap @ 214 °F, E.P. @ 260 °F.”

The oxidation stability measures a fuel’s resistance to breakdown by using oxygen, pressure, and heat, and recording the amount of time it takes to break down while in storage.

A fuel’s oxygen content shows if it is oxygenated or not. Some manufacturers simply say “Yes” or “No,” and some show a percentage: “0” for none, or “3.5.”

Its lead content shows if a fuel has tetra ethyl lead or not, and if so, how much.

And finally, the color is simply the color of that specific fuel.

23 Octane Pump Gas 5/25

Oxygenated Race Fuel

Highly oxygenated fuels are the relative newcomer to the race fuel scene. They have oxygen molecules in them, thanks to oxygenating components like methanol and ethanol. Compared to straight hydrocarbon race fuel, they require richening the mixture, but they also make more power. However, some oxy fuels aren’t as low-maintenance as hydrocarbon fuels, and are best for dedicated racing vehicles. See the “How To Choose The Right Race Fuel” sidebar in the extended web version for more information.

25 Octane Pump Gas 6/25

Race Fuel Octane Ratings

Now that the technical stuff is out of the way, let’s take a look at the octane range of today’s race fuels. We researched various race fuel manufacturers, including Rockett Brand and Torco, to create the following list. And for clarity’s sake, we’re not including any outliers that you wouldn’t use in your Corvette anyway, like FIA-approved fuels.

That being said, today’s race fuels are available with:

Motor octane number (MON) ratings of 95 to 120
(R+M)/2 / research octane number (RON) ratings of 100 to 118
Highest unleaded MON: 110
Highest leaded MON: 120
Leaded and non-oxygenated MON of 96 to 120
Leaded and oxygenated MON of 100 to 120
Unleaded and oxygenated MON of 95 to 101

05 Rockett 93 Oct Blend Chart 7/25

Blending Race Fuel With Pump Gas

Adding a few gallons of race fuel to varying amounts of pump fuel is a popular octane-boosting method that enthusiasts use. We were curious what a race fuel expert would say about it, so we asked the Rockett Brand team. Here’s what they said:

“[Mixing race and pump fuels] is an okay thing to do, and much better than ‘octane boosters.’ It does not damage the engine, and improves the quality of the street gas. Octane numbers blend almost linearly, and we actually publish blending charts on our website for those who insist on doing this. For example, if you blend a 92-octane pump gas with a 100-octane race fuel in equal amounts, you will get a 96-octane fuel.

“But keep in mind, if you don’t want to spend money on straight race fuel, you are watering down the benefits that that straight race fuel has. You may get the octane you need, but you will not get the optimized vapor pressure and blending.

“Overall, I recommend that the user choose the octane that he or she needs, and not try to be a chemist and play with the fuel. Do you water down your drink before you consume it? Life is too short to drink cheap booze.” Well said.

06 Torco Accelerator Corvette 8/25

Race Fuel Concentrates

Race fuel concentrates are a relatively new player in the octane-adding game, and one prominent product is Torco Race Fuels’ Accelerator. This unleaded race fuel concentrate is blended in-house at Torco’s Arizona location—alongside leaded, unleaded, oxygenated, alcohol, and nitro race fuels. We had questions, and Jody Davis at Torco Race Fuels gave us answers.

“A race fuel concentrate adds fuel ingredients to pump gas to increase its octane,” Davis starts. “We do this by ‘over treating’ the Torco Accelerator race fuel concentrate. These are the same chemicals used in our unleaded race fuels, but they’re included at a very high treatment rate. When the concentrated formula is mixed into the pump gas, the treatment rate is very similar to what our unleaded race fuels have in them.”

Davis believes that, compared to race fuel, race fuel concentrates have easier portability and numerous blending options. “We have many customers that use the Torco Accelerator when they are going to the track. They will use pump gas to drive there, then they simply pour the can into their vehicle and hit the track. Many racetracks do not offer race fuel at the facility, so this is a great, easy-to-handle option.

“The other major benefit is that the customer can tailor the octane requirement to their engine. They can make a 97-octane fuel, while a race fuel supplier may not make one that fits their needs. Torco Accelerator can be mixed to whatever the customer may desire.”

We also asked Jody why Accelerator was only available as unleaded concentrate—was it customer preference, or would enough lead not fit in the small containers? “Lead is not used in a concentrated form due to the fact that the lead is extremely toxic,” he explained. “Aside from that, for a concentrate to treat 10-20 gallons of pump gas, there would need to be 40-80 grams of lead in a container. A typical, 118-octane leaded race fuel only has about 6 grams of lead per gallon—so 80 grams in a quart container would be a ton.” Fair enough.

Finally, Davis gave answers to some of the frequently asked questions that Torco gets:

• “Accelerator is safe for late-model cars, as it contains ingredients that have either been used in unleaded pump gas, or is still being used in unleaded pump gas.”
• “It will leave an orange residue, which is one of the ingredients. It will leave a very light residue on the spark plugs, but is easily wiped off and won’t build up like carbon—and it won’t harm O2 sensors or catalytic converters.”
• “Accelerator’s shelf life is usually much longer than a year, but we recommend you use it within one year as we have no control over how it is stored—keep it in the original container as it is light sensitive.”
• “Mix it by pouring the concentrate into your fuel tank first, then filling with pump gas on top of it. This will provide ample agitation to mix the product with the pump gas.”
• “And stay away from mixing Accelerator and fuel in plastic fuel containers, as the plastic allows light to penetrate the fuel and the Accelerator can separate from the fuel.”

07 Alky Control 9/25

Water-Methanol / Alcohol Injection

A bit different from the race fuel solution to octane, these injection systems are known as water-methanol injection, or alcohol injection. They’re “octane on demand,” activating from as low as idle, to high-load or mid to high boost levels. Unlike fuel that flows through the injectors, water-meth systems inject fluid into the “up pipe” going to the throttle body. They’re effective on forced-induction and high-compression engines that see street or track use. And they’re hugely popular on turbo or supercharged street machines that would otherwise use hundreds of gallons of race fuel during normal street driving.

It’s common for different vehicles to use different water/alcohol formulations for their overall goals. For instance, enthusiasts using an aftermarket blower with street boost levels might use a 50/50 water/meth mix. But hardcore turbo guys running ultra-high boost forego the water entirely, and use 100 percent methanol.

08 Snow Methanol ZR1 Pump 10/25

For more insight we spoke with Matt Snow, president of Colorado-based Snow Performance. Snow Performance specializes in water-methanol injection systems, and Matt explained how a water-meth system works, what fluids can be used, and why it’s such a cost-effective solution when premium pump gas won’t cut it.

“An engine running pump gas is limited on how much compression, cam timing, spark, and boost it can run,” Matt starts. “But water-methanol injection increases the detonation threshold of the engine, allowing more timing and/or boost for more power and efficiency without inducing detonation.”

While several liquids can be used, including ethanol or iso (rubbing alcohol), methanol is preferred as it gives more detonation control. “Due to testing difficulties in the standardized test engine, methanol’s RON is published as 105,” Snow explains. “But in reality, the effective octane of methanol is much higher—some say as high as 130. So when you’re discussing the effective octane—the actual resistance to detonation in the combustion chamber—91-octane fuel with a 50/50 water-methanol mix compares well to 116-octane race gas.”

It’s important to note that Snow’s Boost Juice fluid is a 50/50 water-meth mix—which he believes is safer. “Even though our systems can use [100 percent methanol], straight methanol has high flammability. So we recommend a mix of half methanol and half water. That way you get 90 percent of straight methanol’s effective octane without the high flammability, and you get the cooling advantages of water as well.”

And if your engine isn’t extreme, you don’t even have to run 50 percent meth—grabbing a bottle of blue windshield washer fluid at your local gas station is acceptable fluid too! “Most engines don’t need 116 effective octane, so for a 30 percent methanol mix, you can inject that blue windshield washer fluid with a -20º rating. Combined with 91-octane fuel, this mixture can hold its own compared to 110-octane race gas.”

09 Snow Water Methanol Nozzles 11/25

Snow Performance’s water-meth systems include a controller, a tank, a high-pressure pump, and a nozzle. These bolt-on systems have harnesses with plug-in connectors, and nozzle mounting plates so no wiring or drilling is required. The controller injects the right amount of water-meth at the right time using application-specific engine parameters, and the nozzle creates a spray with very fine atomization.

As the popular ECM tuning suites support water-meth systems, tuning is straightforward—though letting an expert tune it is recommended. On that note, Matt stresses that water-meth isn’t like injecting nitrous, and too much can cause combustion quench. The method is like so: after baselining and getting the engine’s air/fuel ratio to 11.5-12:1, the best way to tune is to start by over-injecting the water-meth, and trimming it until no power is lost on the dyno. Then you can start adding timing and boost.

“On boosted vehicles using pump gas, most tuners are good with an 11:1 air/fuel ratio, and they pull 1/2 degree of timing out for every pound of boost on the WOT table. With water-meth, the engines don’t have to run so fat because combustion is being cooled by the water-meth, and the air/fuel ratio can be adjusted more for peak power.

“And Snow offers additional peace of mind with SafeInjection, an upgrade that monitors our system for flow. If it ever gets too high or too low, it will trigger a safer tune or open up a BOV to reduce boost instantly.”

The water-meth reservoir can be located in the engine bay, or elsewhere like the hatch or trunk. Snow Performance offers several reservoir sizes, including a 3-quart container, 2.5-gallon reservoir, and a modular, 5-gallon “fuel cell.” And regarding usage, a 500-horse Corvette with a 3-quart reservoir carries enough fluid for 12 quarter-mile passes.

10 Snow Stage3 Controller Corvette 12/25

The Parts Store Octane Booster Myth

It’s very important that you don’t lump race fuel concentrate and other high-octane chemicals in with parts-store octane boosters. Somehow, the word “octane booster” became the “Coke” of adding octane—and those words have been used on milquetoast parts-store products for decades.

Those inviting plastic bottles do look super cool, and after dropping a few bucks and eagerly dumping mystery fluid in the tank, you swear that you feel some extra power in the old butt dyno. But the truth is, they’re mostly slick marketing at work: these products don’t add full octane points, like say from 91 to oh, I don’t know, “104” octane. They only add “points” of an octane, or from around 0.2 to a little over 1 octane number. Now, if you have a slight ping and want to spend $8 to go from 91 to 92 octane, then by all means buy the stuff—it may restore a couple of horsepower. (Or you could buy some top engine cleaner and remove the carbon deposits that may be causing that ping instead.)

Thankfully, there’s said to be some effective octane adders out there. While we’ve not done in-depth testing, some have reported good results with brands like Klotz and Aces.

11 Xylene 13/25

Homebrew Octane Boosters

For years, DIYers have added big octane to pump gas by following formulas found on sites like the Homebrew Octane Boosters page, and using available chemicals like toluene, xylene, iso alcohol, and methanol/ethanol. However, some of these powerful chemicals are very hazardous, and require adding a lubricating and/or cleaning agent to play nice with your engine and fuel system. Some aren’t legal in states like California, either.

And according to the Rockett Brand brain trust, a higher octane rating doesn’t a good race gas make. While you won’t be surprised that a race fuel company doesn’t recommend these homebrews, these guys have forgotten more about gasoline than we will ever know. So for your and your engine’s health, you should at least listen to what they have to say:

“Please stay off these homebrews,” Rockett’s Wusz states. “They’re dangerous and they don’t work like you think they do. It takes solid science to make a good gas; it’s not what you put into it, it’s how you blend it. And just overdosing gas with toluene might raise the octane, but it’s not necessarily enhancing performance even if it won’t activate the knock sensor until later. Octane is just one of numerous aspects in gas. For instance, toluene burns slower—it can cause problems, especially on the exhaust side of turbo applications.” Okay, you’ve been warned.

Av Gas

Av gas seems like a fantastic bargain, especially because of its high octane and affordable price. And many enthusiasts, your author included, have used aviation gas to add performance to forced-induction street machines for years. But again, Rockett’s Wusz says you get what you pay for.

“First, av gas is designed for planes flying at 10,000 feet, and running a max rpm of 2,800,” he explains. “And planes have air/fuel mixture controls that allow the engine to be ‘full rich’ at takeoff. This is critical, because the specific gravity of aviation fuel is on the low end, down as far as the .69X range. It’s a very light fuel that needs to be richened up, or it can make an engine run lean.”

And besides lean air/fuel ratios, there’s more bad news. “Av gas has a much bigger blending tolerance window than racing gas does,” he says. “When the window is broader, you get lower-quality hydrocarbons that slow the burn down. That’s okay for aviation, as it doesn’t affect a plane’s performance. But for vehicles—especially high-performance cars running high rpm—it isn’t good. In short, 100LL isn’t the same as 100-octane racing fuel, and you’ll get better performance out of the racing fuel.”


High Octane Buyer’s Guide

The following race fuels, race fuel concentrates, and water-meth / alcohol injection systems are some of the best octane-enhancing products on the market today. Be sure to check out each manufacturer’s website for more information.

12 Rockett 100 Race Gas 14/25

100E Unleaded

Rockett Brand’s 100E is a street-legal gasoline with a MON of 97, a RON of 105, and an (R+M)/2 of 100. This oxygenated fuel is designed for on- and off-track use in all performance engines with compression ratios of up to 14:1. It is specifically blended to remain stable under extremely high cylinder pressure, and will resist power-robbing detonation of combustion chamber “end-gas” to improve engine horsepower and acceleration. An excellent fuel for street-driven, late-model Corvettes.

Company: Rockett Brand, www.rockettbrand.com
Specs: 97 MON, .717 Specific Gravity, 10% alcohol, 3.5% oxygen
Available: At the pump, in 5-gallon pails, 55-gallon drums, in bulk, and by direct shipment from dealer locations
Price: Contact a distributor for more information

13 Rockett 112L Race Gas 15/25

112L Leaded

Rockett’s 112L is a leaded gasoline with a MON of 107, a RON of 117, and an (R+M)/2 of 112. It’s formulated for use in normally aspirated engines with compression ratios as high as 16:1. Primary use of the fuel is by asphalt and dirt oval track racers, but it is also a great option for drag racers and sports car racers as well.

Company: Rockett Brand, www.rockettbrand.com
Specs: 107 MON, .721 Specific Gravity
Available: At the pump, in 5-gallon pails, 55-gallon drums, in bulk, and by direct shipment from dealer locations
Price: Contact a distributor for more information

14 Rockett 118 Race Gas 16/25

118L Leaded

Rockett’s 118L is a leaded gasoline with a MON of 115+, a RON of 120, and an (R+M)/2 of 118. It’s designed for use in supercharged and turbocharged racing engines, as well as extreme naturally aspirated mills. It burns faster and more completely at higher RPM than other fuels, allowing it to deliver greater horsepower. 118L works best in applications with no sanctioning body restrictions, where engines have no limits on compression ratios, boost levels, or nitrous amounts.

Company: Rockett Brand, www.rockettbrand.com
Specs: 115+ MON, .701 Specific Gravity
Available: At the pump, in 5-gallon pails, 55-gallon drums, in bulk, and by direct shipment from dealer locations
Price: Contact a distributor for more information

15 Torco Accelerator Case Octane Booster 17/25

Accelerator Race Fuel Concentrate

Torco Accelerator is an unleaded race fuel concentrate that contains many of the same additives that go into race fuels. This blend of components will transform the makeup of premium pump gas to closely resemble race fuel. Using Torco’s blending chart, you can mix Accelerator with premium unleaded to raise octane above pump gas levels—without having to transport gallons of race fuel.

Company: Torco, www.torcoracefuel.net
Specs: .710 Specific Gravity
Available: In 32-ounce cans, 8-ounce bottles (pack of 6), 32-ounce cans (pack of 6), and 5-gallon pails.
Price: $20.95 - $320.80

16 Torco 5gal Fuel Pail 18/25

Hot Rod 110 Leaded

Torco’s Hot Rod 110 is a leaded gasoline with a MON of 106, a RON of 114, and an (R+M)/2 of 110. It’s aimed at naturally aspirated engines with up to 12:1 compression and fewer than 500 cubes.

Company: Torco, www.torcoracefuel.net
Specs: 106 MON, .740 Specific Gravity
Available: 5-gallon pails, 55-gallon drums, and in bulk
Price: Contact a distributor for more information

17 Snow Performance Stage 3 System 19/25

Water-Methanol Injection System

The Stage 3 Boost Cooler is an advanced water-meth system for EFI, turbo, and supercharged vehicles. It creates a 2D injection map based off of boost and fuel injector pulse width, to deliver highly accurate and tunable water-meth delivery. And it will control two Hyper-Sonic Nozzles independently of one another, to provide your engine the exact amount of water-meth needed at all rpm ranges. This 2D map injection and dual-stage technology translates into highly accurate injection curves and tuneability, resulting in 50- to 110-horsepower gains and up to 150-degree air-temp reductions. And its 300-psi UHO pump and terminated weather-tight OEM harnessed wiring connections make for easy installation in your EFI and boosted vehicle.

Company: Snow Performance, www.snowperformance.net
Specs: 300 psi pump, 3-quart fluid reservoir, three Hyper-Sonic Nozzles
Price: $849.99
Notes: 1-year warranty, 2.5- and 5-gallon reservoirs optional, 3/8-inch 300-psi pump upgrade for 700-1,000-hp applications optional

18 Snow Performance 3gal Fuel Cell 20/25

5-Gallon Fuel Cell

This 5-gallon modular fuel cell is designed to work with all Snow Performance gas systems to deliver a plug-and-play, race-ready fuel cell assembly. Comes complete with a sump, 3/8 NPT outlet, modular pump/solenoid mount, and your choice of red, blue, or black ¼-inch high temp nylon tubing. This fuel cell will maintain fluid to the outlet during high speed turns, and allows seamless integration of all Snow Performance pumps/solenoids for those who want the ultimate in a race-ready, water-methanol reservoir.

Company: Snow Performance, www.snowperformance.net
Specs: Comes with two aluminum straps, 3/8 NPT outlet fitting for ¼-inch tubing, one power solenoid upgrade, and 15 feet of ¼-inch high temp nylon tubing
Price: $249.99
Notes: Larger reservoirs available, see website for more information

19 Alky Control C5 Corvette Methanol 21/25

C5 Methanol Injection System

This Methanol Injection kit is C5-specific. It features a 250+ psi pump (on M15 and water) with a waterproof cover, which works in tandem with a 15-gph nozzle and a check valve. A progressive controller is preset for 1997-2004 Corvettes, and a 2-bar GM MAP sensor with regulator reads boost and supplies a signal to the controller. This complete kit includes a 90-micron inline filter, pre-taped pump fittings, and custom-length Teflon-lined braided hoses, AN fittings, and wiring. Twin nozzle upgrade available for combos making over 650 rwhp.

Company: Alkycontrol, www.alkycontrol.com
Specs: 250+ psi pump, M15 15-gph nozzle
Price: $609.95
Notes: M10 or M15 nozzle, 2.5 and 3-bar MAP and MAF upgrade available, twin-nozzle upgrade available

20 Alky Control C6 Corvette Methanol 22/25

C6 Methanol Injection System

The C6-specific Methanol Injection kit uses two 15-gph nozzles with the 250+ psi pump (on M15 and water). A progressive controller is preset for C6s, and a 2-bar GM MAP sensor with regulator reads boost and supplies a signal to the controller. Additionally, a custom relay transfers power from the fuse box to the controller, eliminating any interference from the system and vehicle electronics. This complete kit includes a 90-micron inline filter, pre-taped pump fittings, and custom-length Teflon-lined braided hoses, AN fittings, and wiring.

Company: Alkycontrol, www.alkycontrol.com
Specs: 250+ psi pump, twin nozzles
Price: $609.95
Notes: M10 or M15 nozzles

Special thanks to the Rockett Brand team for enhancing my octane IQ.


21 Octane Race Gas 23/25

How To Choose The Right Race Fuel

Our testosterone-addled car culture holds competitiveness and individualism high. Yet when race fuel is concerned, we blindly chase forum advice like bridesmaids after a bouquet. And while we love us some good old fashioned forum advice ourselves, with products like fuel or oil, it’s best to consult with experts. So here are some tips on how to choose a race fuel:

Contact the company: contacting a race fuel company’s tech support team is the best advice we can give you. Why? Well, besides the fact that their engineers actually make the stuff, these folks know our industry’s cars, engines, and motorsport series well, and they’re probably familiar enough with your modifications to recommend a killer fuel.

Learn to read the labels: “[With all of the products and misinformation out there], today’s consumers have it tough,” Day says. “But they need to learn how to read and understand what goes into race fuels. And Rockett’s tech support team is happy to answer any questions they might have about them.”

Quiz your tuner: additionally, your tuner and/or builder can be a wealth of information about race fuels and your engine’s octane requirements, so feel free to reach out to them too. However, if you’d rather try to spec a fuel yourself, or you have a unique build and need to zero in on your compression ratio first, you can…

Calculate your engine’s dynamic compression ratio to determine octane needs: if you’ve ever been curious about your turbo/supercharged or high compression N/A engine’s “max” compression ratio, look up an online dynamic compression ratio calculator. They usually are set up for either N/A or forced induction, and let you input specs like your engine’s bore, stroke, rod length, head volume, gasket thickness, static compression ratio, degrees ABDC of cam timing, altitude, boost, etc. Then they compute the effective compression ratio that your engine sees. As an example, I input one of my turbocharged engine’s specs. While the dynamic compression ratio without boost is always lower than the static CR, at 25 psi boost my engine sees a 19:1 compression ratio. Armed with that info, I’d have an easier time weeding out 100-110 MON race fuels and choosing a higher octane for that ultra-high compression ratio.

Stick with non-oxygenated race fuels unless you’re shooting for a record: High-tech, highly oxygenated race fuels are the latest and greatest right now, thanks to the potential for more power over non-oxygenated fuels. But keep in mind that oxygenated fuels can require additional ECM fueling changes. They may also need additional, lower-micron fuel filters, and some can even cause crankcase dilution, and can be hard on your fuel system if left in the tank for awhile. So unless you’re shooting for a record or a class win, we’re pretty sure those non-oxygenated, 115+ MON fuels will handle anything you can throw at them.

Make decisions that’ll minimize your spending: using leaded fuel in a late-model, mostly street-driven Corvette causes accelerated oxygen sensor and catalytic converter fouling, which results in you paying out the nose for replacement parts. How can you avoid such an expensive fate? Start with only running unleaded race fuel, or only mixing in small amounts of high-octane leaded race fuel with your pump gas (though leaded is illegal on the street, and will still eventually kill those O2 sensors). And if running high-octane leaded is mandatory for your balls-out forced induction build, consider going to a cat-less exhaust system to avoid these issues.

Safety first: an old hot rodding truism is, “An engine doesn’t know how much octane it’s running—unless it’s too low.” And here’s the rub about high-powered engines that need high octane; damaging detonation can be a tank of low octane or a bad tune away. We don’t want that. You don’t want that. So when you choose your fuel, do the following (or pay a good dyno tuner to do it for you): use a wideband O2 sensor, start with conservative boost, timing, and air/fuel ratios, and gradually turn up the wick. Also, data log the hell out of your pulls until you know the tune is spot on.


22 Octane Race Gas 24/25

Race Fuel Storage Tips

From the refinery into your engine, street gas only “lives” about 30 days. But thanks to purer components and specific additives to extend shelf life, quality race fuels like Rockett Brand can stay potent for several race seasons. But fuels have to be stored the right way—if you’ve ever unscrewed the cap on a fuel can that sat in the sun, you’ve heard the hiss of gas escaping. This “weathering” is the loss of the fuel’s light ends through evaporation—the lighter hydrocarbons are escaping. So to prevent your fuel from weathering, do the following:

• Keep fuel in a metal container: light deteriorates fuel, so this is the best way
• If you must keep it in a plastic container, make sure it’s dark colored
• Ensure that the container’s O-ring seals properly, and isn’t damaged or brittle
• Keep the jug’s caps and vent caps tight: they’re there to prevent massive vapor buildup, but keeping them closed tight won’t allow evaporation to break down your fuel
• Store your fuel containers in a cool place, away from sunlight

Try to resist the urge to unscrew the cap and inhale that sweet, sweet race fuel smell.

24 Octane Corvette C6 Dyno 25/25

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