What is Pro Mod?

 

Pro Modified Cars are 250 + mph doorslammers, running on Injected nitrous / gasoline or methanol.

They are the fastest class of drag cars with working doors. Pro Mods are purpose-built race cars cloaked

in replica street car bodies ranging in style from the 1930s to the present day.

Pro Mods cover the quarter mile in under 6 seconds but the average is the low 6 second range.

 

Promods have become fan favorites and part if the thrill is to cheer for your favorate type of Pro Mod.

Nitrous or Supercharger - Always like to pair them up to see who will get the win.

 

 

 

 

 

 

 

 

 

Anatomy of a Pro Modified

 

Below is the anatomy of a typical Pro Mod, though cars do vary in detail.

 

 

 

 

 

 

 

 

 

Specifications

Pro Mod cars are permitted either a nitrous oxide-injected motor burning specialized race fuel

or a supercharged engine running on methanol.  Minimum weight is 2325lbs for some nitrous-injected

cars or 2600lbs for some supercharged methanol cars. Nitrous or blown (supercharged) motors cost

approximately $75000.00USD and up from a recognized engine builder. Nitrous motors are upwards

of $95,000.00USD. Connecting rods last from 25 runs on a blown car to 50 runs on a nitrous car and

cost around $1,200.00USD and up. Valve springs are consumable items and individual pistons and

rings need changing on a regular basis. A blown car would have its spark plugs changed after every

run if the tuner wanted to 'read' the plugs or after every 2 or 3 runs if not.

 

1. Chassis  

  Chassis are custom fabricated from 4130 chrome moly tubing according to strict rules. The Maximum

  permitted wheelbase is 115" (2.92m). Features of the chassis include twin chassis rails, strut-style

front suspension, carbon fiber or aluminum interior paneling, aluminum motor-mounting plates,

coil-over rear suspension and 4-link or swing arm-mounted axles. The car has front and rear brakes

but relies primarily on twin parachutes to slow it from speeds of 230mph and faster.

 

2. Body

 

Pro Mod body shells are highly modified replicas of original car bodies built from composite materials.

The bodies may have been roof- chopped, sectioned, stretched in the wheel base, scaled down from

the original or otherwise modified to give better aerodynamics and accommodate the huge rear tires.

The maximum front overhang is 45”. A rear wing is added to give down-force at the top end of the track.

A central driving position is not permitted.

 

3. Fuel

 

Nitrous motors use a high octane race fuel. The blown cars use methanol. The fuel system on a nitrous car can

flow up to 8.5 gallons per minute and the blown car fuel system can flow over 15 gallons per minute. In a blown

car methanol costs around $10.00 per gallon and each run would use up to 12 gallons including the burnout. In a

nitrous car unleaded race fuel costs around $25.00 per gallon and each run would use approximately 3 gallons, as well

as 6lbs of nitrous oxide at $10.00 per pound.

 

4. Engine

 

Engine capacities are not restricted for nitrous-assisted motors and cubic inches are up in the 904” at the top end of the scale.

There is a restriction of  526 cubic inches for supercharged (and Turbo charged) methanol engines. In addition,

the blown entries are restricted to a maximum valve size of 1.9" exhaust and 2.4" inlet and are restricted to 20%

overdrive when using the 14-71 high helix blower. Nitrous motors produce in the region of 3 horsepower per cubic

inch so the differences in engine size, minimum car weight, etc., are designed to redress this balance so that both

combinations can be competitive.

 

5. Drivetrain

 

Pro Mod cars use a multi-disc clutch. A maximum of 3 discs are allowed. Most cars use a planetary-design

transmission, commonly the Lenco or B+J. Some cars have also started to experiment with a twin lay shaft

transmission such as a Liberty . Nitrous cars generally use a 4-speed transmission and blown cars use a 3-speed.

Blown cars are permitted a maximum rear axle gear ratio of 4.56:1.  The use of automatic transmissions

and shifters are now permitted in the class.

 

6. Driver Safety Equipment

 

A fire-resistant suit including gloves and shoes must be worn by the drivers of nitrous cars. The drivers of blown cars use

the same suits, gloves and boots as Top Fuel drivers. Helmets and a 360-degree neck brace must be worn by all drivers.

The Hans device, as worn by Formula 1 drivers, is also required and is gaining in popularity. A 5- point, 3"-wide driver

harness must always be fitted. All cars are equipped with a shatterproof bell-housing and a transmission blanket to

protect the driver in the event of a clutch or transmission failure and an engine 'diaper' to contain any spilled oil.

 

7. Suspension

 

Cars are required to have production-style suspension systems. Most cars use purpose-built, McPherson-style

struts with rod-ended control arms at the front and 4-link rear suspensions which allow an almost infinite range

of adjustments to compensate for track conditions. Coil-over shock absorbers are used at the rear along with anti-roll bars.

 

8. Wheels and Tires

 

Rear wheels are 16" in diameter and 16" wide and have to be 'beadlocks', i.e. have clamping rings to secure the tires.

Rear tire pressures are from 4.5psi and front tires run up to 34psi. The tires are designed to 'crinkle' to assist the

launch and will 'grow' in height by approximately 4" during the burnout and at the top end of the track. A pair of

rear wheels costs in the region of $2000.00USD and a pair of slicks about $1000.00 - two or three pairs of slicks

are needed in a season.

 

9. Brakes

 

Pro Mods are equipped with aftermarket disc brakes on all four wheels with some cars using carbon fibre discs and pads.

The brakes are used in conjunction with dual parachutes to slow the car from speeds of up to 255mph. Brakes are generally

single-pot on the front and 4-pot on the rear with the system designed to rear-bias through the large rear wheels and tires.

Carbon Fiber rear breaks are now mandatory.

 

10. Data Logger

 

Most Pro Mods carry an on-board data logger which monitors and records information from sensors located all over the car.

Data is used, for example, to make the fine clutch adjustments essential to maintain the car at peak performance.

Other sensors monitor exhaust gas temperatures, fuel flow, throttle position and rear suspension travel.

A data logger can cost from $3000.00USD (to monitor basics for tuning) and upwards depending on the type and sensors.