By Bill Kennedy

Extrude Hone is helping Jeff Garmon of Garmon Diesel Performance in McDonough, Ga., turn diesel pickup trucks into drag racing rockets that can cover the quarter mile in less than 11 seconds. Garmon says he gets a significant portion of the horsepower needed to make the big trucks move so fast by using fuel injectors treated with Extrude Hone's abrasive flow machining process. 

Garmon builds racing pickups for the Diesel Hot Rod Association's (DHRA) Pro Street Shootout for modified street diesels.  Pro Street has two truck weight classes:  5,500 lbs. for trucks burning straight diesel fuel, and 6,200 lbs. for those that inject nitrous oxide gas to produce more power.

For the 5,500 lb. class, Garmon starts with a 5.9 liter, 12-valve, inline six-cylinder Cummins engine. In stock form, the motor has a single turbocharger running 15-18 lbs of boost and direct mechanical fuel injection. Through an automatic transmission, it puts out about 140 hp. and about 365 lb./ft. of torque to the rear wheels.

To increase power, Garmon replaces the single turbocharger with two larger turbos, and hikes the boost to 80-90 psi. Engine structural changes are minimal. Garmon said he mills the pistons to drop the compression ratio from 17:1 to about 12:1.  "We o-ring the heads and o-ring the blocks to keep the head gasket on, but that's about it. Stock rods, stock crank, stock block.  These little engines are tough." On a dynamometer recently one of his modified engines registered 762 hp. at the rear wheels along with a staggering 1,558 lb./ft. of torque. 

Garmon says the key to success is management of air and fuel. The massively increased airflow produced by the turbochargers has to be matched by a much greater flow of fuel.  Accordingly, the engine's fuel injectors are enlarged to Garmon's specifications by Extrude Hone Corporation's MicroFlow abrasive machining process, which  employs a low-viscosity abrasive-laden honing material.  Garmon said, "They run the honing material through the injectors and enlarge them.  The process makes the interior like glass. It polishes it to a slick, hard surface and makes it flow much more fuel than just making the hole big." Other racers enlarge injectors via electrical discharge machining (EDM), Garmon said, but the result, he said, is "Nasty. It's not polished."

On one of his engines, Garmon says, "you could take the Extrude Hone injectors out, put the stock ones in, and it probably would lose 250 hp." 

Jim Bower, diesel injector specialist at Extrude Hone, said the company has been treating diesel injectors since the early 1970s, when the big truck OEMs sought ways to get consistent emission performance from their engines in response to tightening government emission regulations. That effort continues, as well as work on enlarged injectors to boost performance for non-commercial trucks. Those modified injectors typically increase flow by 30 percent,  providing street truckers 80-90 extra horsepower.  Garmon's injectors are a different story, Bower said. With orifices enlarged from about 0.008" diameter to about 0.013", flow improves 150 percent.  Normally, the fuel management system of an engine couldn't handle such an increase and the motor would bog down, Bower said. In fact, he recommended against such a big change.  "I told Jeff I didn't know how he could burn all that fuel," Bower said.

But Garmon Performance Diesel has its own dynamometer and Jeff Garmon repeatedly tested the high-flow injectors and tweaked timing and other elements of the fuel delivery system to produce maximum performance.

The results speak for themselves.  At the May 7, 2005 DHRA meet at Beech Bend Park in Bowling Green, Ky.,

Darren Morrison, running a Garmon engine in his four-wheel-drive slick-tired Dodge Ram 2500 pickup, won first place honors and set a new DHRA record of 10.77 seconds for the quarter mile.  He outpaced all the higher-powered nitrous-assisted trucks – running EDM-enlarged injectors – by more than half a second. 

Garmon says he will have his own two-wheel-drive  truck ready for the DHRA Diesel Nationals at Indianapolis Raceway Park, Indianapolis, Ind., June 25-26, 2005.  With two customer trucks as well as his own in the running, Garmon says,  "It's definitely going to be one of the three of us that's going to win, I can tell you that right now!"

 

Contact Extrude Hone Powerflow at 1 800-613-1065 or By Email.

Editors note: Bill Kennedy is an independent industrial and technical writer based in Latrobe, Pa.