Information for racers - Different Racing Fuels
Newsletter No. 3 - Fall 2011

All of the staff at racecarbook.com & airdensityonline.com hope your racing season is going strong.  The information that follows is about how a racing engine and vehicle or vessel work.  It was derived from extensive combustion engineering commercial projects and our own race testing.  It is provided for racers to increase the performance of their vehicles & vessels.
 
 
E85 fuel for racing is highlighted in his newsletter.  The next newsletter will be sent out around December 2011.  To unsubscribe, use the link at the bottom of this email.

E85 as a Racing Fuel
E85 is examined as a racing fuel.  E85 is a combination of ethanol and low octane gasoline.  Some racers report more power from E85 than from methanol.  On the other hand, when the Indy Car League converted from methanol to straight ethanol, dynamometer tests revealed a reduction in power after the conversion.  Regardless of those differing results, several racers are interested in the conversion because of good availability in some areas and low cost of E85.

Lean Out Methanol Fuel Setup To Run E85
The conversion from methanol to E85 requires leaning out the engine about 35-50% from the methanol mixture setup.  E85 contains less oxygen to support combustion than methanol.  That changes the air to fuel ratio.  In addition, converting to E85 from gasoline requires enrichment of about 20-30%.

Horsepower From BTUs Analysis
The BTUs per pound of fuel indicate the heat energy from the fuel.  However, since various fuels are run at different air to fuel ratios, the BTUs per pound of the burn ratio mixture of air and fuel are a better indicator of heat energy.  BTUs per pound of mixture are a good measure of how much horsepower an engine will make.  
Read the full article.


New Engine Combo For Low Percentage Nitro
Recently we tested a new engine combination in our drag race car.  It is based on our previous drag racing blown alcohol Hemi with a 14-71 blower featured throughout our publications.  This low maintenance bracket engine made between 1,200 and 1,700 horsepower, depending on blower overdrive and the proper nozzles & jetting.  That is all covered in our Fuel Injection Racing Secrets book.  Note that RPM operating ranges were kept low for reliability and cost reduction.  That kept the power levels below the actual attainable levels if the engine were wound out instead.

Rotating Ass'y Changes
The rotating assembly was changed to off-the-shelf parts.  The resulted in:

  1. a bigger engine, previously 438 ci; now 478 ci
  2. lower compression, previously 12 to 1; now down to 8.2 to 1.

New Engine Combo Result
The reduction in compression was in preparation for testing various low percentages of nitro.  We started with straight methanol, and the fuel injection setup needed changes to the air to fuel ratio from the previous setup.  It needed leaning down about 10%.  In addition adjustments were done to restore idle characteristics that were affected by the low compression.

Low end power was reduced as a result of the lower compression.  While we did not measure it, top end power seemed to remain the same as it was for the previous high compression rotating assembly.  That was indicated by the same MPH in test runs from the new combination as similar setups with the old combination. 

Air to fuel ratios were developed for straight methanol in the new combination as well as various low percentages of nitromethane.  More about that is written throughout our nitro blog.

Some of the test runs can be viewed on our videos.
 

Effect of Air Density
... is illustrated in Fuel Injection Racing Secrets, p. 159, and discussed on several other pages throughout that book.  Tuning can be inaccurate if it is first considered based on changes in the volume of air and then considered instead based on changes in the weight of air.  For example, a common engine measurement, cubic feet of air per engine revolution, is a volume.  In this book, it is converted to the weight of air per engine revolution.  Then it is corrected for air density.

The effect of air density is discussed specifically on p. 115 through 119 and throughout other sections from 5000 HORSEPOWER ON METHANOL

The effect of air density is discussed throughout MOTOR SPORTS STANDARD ATMOSPHERE & WEATHER CORRECT METHODS

AIR CFM & AIR WEIGHT
Air density has a profound effect on the amount of air going into an engine. It does NOT change the CFM that is the volume.  It changes only the weight of that air.  If the air density is up from 100%, it increases the weight of air into the engine.  If the air density is down from 100%, it decreases the weight of air into the engine.  At an elevated location such as Bonneville, an air density of 80% is common on land speed race days in the hot summer.  The CFM going into engine scoop remains the same as it would be at lower, sea level locations.  However, the density of the air at high elevation and hot days is lower. Low air density is low air weight.   That effect on tuning is further illustrated throughout our books.

Aerodynamic Drag
The same effect applies to aerodynamics. The CFM going around the body of a racer at speed is the same at both high and low altitude racing events. However, the weight of the air is different. That is why it takes a lot less power to push a racer through the thin light air at Bonneville on a hot day than the thick heavy air at sea level on a cool day.

Is Thin, Light Air Good Or Bad For High Speed Racing?
Is the decreased power necessary to push a high speed racer through thin air more or less than the decreased power of the engine from thin air? Consider the following:

  1. In normally aspirated engines in a vehicle with greater drag, the loss in engine power may be a lesser effect than the positive effect of the thin light air on the car body that is not aerodynamic.
  2. However, in a streamliner with lower drag, the improved aerodynamics from thin light air on the car body may be less of an improvement than the loss in engine power.
  3. In supercharged engines, the thin light air may be a blessing in both full bodied & streamline cases. The reduced drag from thin light air, especially on a sedan, may shine over the loss in power from thin light air.  The use of a supercharger doubles or triples the CFM into an engine that may restore a lot of the power.  Also the blower overdrive can be turned up to compensate for the thin light air in many cases.
  4. The other issue would be the speed.  In slower classes with smaller engines, the aerodynamic advantages of the thin light air may be trivial, and the loss in power from thin light air slows the racer.
  5. In faster classes with larger engines, the aerodynamic advantages from thin light air may out weigh engine power losses from thin light air, and the racer may really fly.

These facts should be considered for land or water high speed racing when choosing a combination.

Compensate Air Density With Blower Overdrive >> How Simple
In some supercharged racing classes, the supercharger overdrive can be changed to restore power from drops in air desnity. It can be increased from a lower overdrive setup used in low elevation heavy air conditions to a higher overdrive setup for high elevation thin light air conditions.

Funnycar Drag Racer Example
In one drag race setup using 18% overdrive, the racer went a 6.8 second quarter mile ET at a sea level racetrack at a moderate temperature. The race car was taken to a racetrack with an elevation of 5,500 feet and a hot day. Airdensityonline/tracks was used to get the air density values from a forecast of that race track. Those values were put into our on-line fuel injection jetting calculator, Pro-Calc to determine a blower overdrive to compensate for the thin light air at the high elevation. The calculator determined that 45% blower overdrive was necessary. That was installed in the race car, and guess what, it ran 6.8 seconds right out of the trailer at the high elevation racetrack.

Door Slammer Drag Racer Example
The same exercise was done for a 9.0 second drag race sedan running at sea level with a low blower overdrive. Pro-Calc was used to determine the overdrive increase to compensate for a subsequent 2,100 foot race track location. The appropriate overdrive was installed, and the sedan ran a 9.0 second drag race at the higher elevation racetrack right out of the trailer.

Fuel System Summary
In both cases, the appropriate blower overdrive increase was used to compensate for the drop in the weight of air from the altitude.  The nozzles & jetting in the fuel system were not changed.