3/7/03

Ed. Note:  Wady Hamam or Pro Mod Wad as he is known in the sport as drag racing's main nitrous Guru. He has been involved in nitrous oxide injection almost from its inception especially with the Pro Mod division.. He is originally from the Buffalo, New York area and has been involved in all types of racing from flat track motorcycles to fuel dragsters. In his wasted youth he even raced a fuel funny car powered by a blown and injected small block Ford! He and his brother campaigned a front motored Top Fuel dragster and lost a race against Don Garlits at the now closed Niagara Falls Dragway. His advice about nitrous problems is highly sought after but he is hard to get to. He has agreed to answer one question every couple of weeks for Drag Racing Online readers. Email your questions to: promodwad@racingnetsource.com, and he will answer the question he finds most intriguing. (Original caricature Pete Millar)

Wady,

A couple of my N2O buddies were discussing the strangest nitrous tuneups they had ever encountered. One took place over a very melted-down piston. One of the guys was explaining the tuneup a pro had done on his system. The philosophy had something to do with "there are two sides to the fuel curve." This tuneup called for as low as 3.5 lbs of fuel pressure. Can you explain what he was referring to as a two-sided fuel curve?

Mike Walker

Mike,

No, I can't explain a two-sided fuel curve because I have never heard of such a thing. You mentioned a discussion took place over a piston that was now an ashtray; that's what happens with 3.5 lbs of fuel pressure, as far as I can see.

What I do know is most, if not all, nitrous racers and engine builders tune with pounds per hour more than with pressure. I have heard from some racers who, if they flow 300 lbs per hour through a flow gauge, may see as little as 5 lbs of fuel pressure. That amount of flowing fuel will support a LOT of horsepower.

I know that in multi-stage systems fuel pressures are not as high as with single and dual stages, but a two-sided curve is not familiar to me.

These days, with the fuel cell mounted in the front of the car as well as the pumps, and much shorter feed lines, lower pressures probably do show up on the gauge or computer printouts, but 3.5 sounds disastrous to me.

Sorry I wasn't more help.

Wady

Pro Mod Wad,

I am running a 355 c.i. Chevy 12.5 to 1 pistons, H-beam rods, factory crank, all forged pro heads with 2.08 intake valves and 50 cc combustion chambers. I have a 600-622 lift cam with 290-300 duration, and a Wiand tunnel ram with 2 660 carbs.

Would I be better off with a fogger or a dual plate system? This will also have a dedicated fuel system for the nitrous. I also plan to use a micro switch so that I'm spraying nitrous at full throttle the entire quarter-mile.

Which is more tunable?

Rich Carlson

Rich,

Definitely a direct port system. It has way more tuneability and benefits. You can tune each cylinder individually and really fine-tune your system.

Plates are good, but there is a point during your run that standoff feeding back into the manifold from piston speed and cam overlap, that the carb and nitrous signals will come almost to a standstill. When this happens, the power level flattens dramatically and the engine will stop pulling hard.

This does not appear to happen in direct port systems and they seem to pull hard till shut down. By reading your plugs and adding or subtracting nitrous and/or fuel from the nozzle, you can get all cylinders to work the same and make maximum power in the engine.

Wady

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