Drag Racing Online - Technical - Pro Mod Wad pg.1 Vol. IV No. 3 March 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 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.

Dear Pro Mod Wad,

I am faced with an unusual problem. Recently I fitted the Pro Shot with foggers onto a small Suzuki 1300 cc swift car with a slightly high compression of 9.5 to 1 and using the standard carburetor with just two foggers.

I started with a jet size as follows: nitrous jet of 24 and a fuel jet of 28. The fuel pressure was 4 on the regulator and the nitrous pressure was 900. When the system is activated, the car just drowns, indicating a fuel rich condition.

Finally, after a lot of changing jets and frustration, it began to run a bit clear when the nitrous jet was increased to about 1/16-inch by drilling retaining the fuel jet at 28.

This is leaving me a bit confused as in all my previous usage, the nitrous jet was always larger than the fuel. Could you advise me on what could be wrong (or what mistake I am making) as I do not want to land up with a blown engine.

Thanking you,

Bobby

Bobby,

Here's the scoop on your problem. It is not unusual for smaller displacement engines to run rich when fitted with the Fogger system. The nozzle allows large amounts of fuel to enter the intake system so there must be much more air added to burn the fuel. The fact that you ran a 1/16" drill through your nitrous jets and got better results tells me you were way rich. You actually squared the jetting at 28/28 by drilling.

My suggestion to you is that you go back to a smaller pattern to start off your tune-up and see what is going to make your engine happy. I suggest you start off at 20 nitrous and 20 fuel and see how the engine responds. If necessary you can back the fuel jet down to 18 or move the nitrous up to 22 to check results if it still seems a little rich. You can then move up in jetting steps to get the performance results you are looking for.

WARNING: You can put too much nitrous in the engine and you WILL cause damage, so be careful as you have a small engine size to work with. Do not be surprised if the fuel jet stays smaller than the nitrous as this happens in many cases to get good performance.

If you have not already installed 1 or 2 step colder spark plugs, do so and check them after a hard run to make sure there are no detonation specks showing on the porcelain. If you do see any traces of this, reduce the nitrous jet size till it is gone.

Bobby, I hope this info helps. Thanks for writing.

Pro Mod Wad

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