Drag Racing Online - Technical - Pro Mod Wad pg.1 Vol. IV No. 12 December 2002

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Ed. Note: Wady Hamam or Pro Mod Wad as he is known in the business is NOS'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 in

volved 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.

Pro Mod Wad:

My question is in regard to the necessity of using a purge valve. I am planning to install a 50 - 100 hp nitrous plate system on my bracket only race car this winter. I have heard some say a purge valve is necessary to maintain consistency with a nitrous system on a bracket car while others tell me that not purging the system prior to making a pass will soften the hit when the nitrous comes on. I plan on initially applying the full shot between 3000 - 4000 rpm with an RPM switch. Depending on results I may or may not install a progressive controller. What is your opinion? Thanks in advance and Happy Holidays.

Sid Grimes

Hi Sid, and Happy Holidays right back at ya. What you hear about purging on both sides of the discussion is true. Here are the facts about purging and why it's done. Even though the Nitrous is under fairly high pressure in the bottle, believe it or not it is not flowing at full pressure when solenoid opens. There is a slight lag time till it reaches full velocity thru the feed line and solenoid and on to plate or nozzle. This along with the fact that the nitrous in those areas turns from liquid to gaseous a few minutes after the system is turned off creates even more of a lag time. If you activate the system without purging the gaseous Nitrous has to be moved thru the system before the liquid gets to the plate/nozzles. This is the reason for the "soft hit" when not purged. Some racers use that for an advantage if they do not want to "strike the tires " on the launch or on a not so good racing surface. When you purge you have removed the gaseous nitrous and allowed liquid to be right at the main solenoid when it opens thus a much stronger launch hit of Nitrous. If you are planning to use the progressive controlled system in your car I would strongly advise the use of the purge valve to assure yourself the most benefit from your system when it activates. Thanks for a great question and good luck in your racing endeavors.

Respectfully,

Wady A. Hamam

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