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I have a 98 a4 stock with 2.73 gears and a 150 shot of a zex nitrous kit. What's the most u can spray on a stock bottom end car? And I want to setup my car for straights nitrous setup anything suggestion on what I shud go with?
I would say that a general rule is to spray 1/3 oof the factory HP. So 345 hp is factory, I would spray 125HP (give or take a few ponies) . Add some race gas for extra security ( Or retard timing)
There is a lot of things that come down to saying what's a safe amount.
mileage
condition of engine
tune
fuel being used
stock car, stock tune is good for 100HP safely assuming the fuel system is good and motor is sound
150HP I would pull some timing if using 93 octane and put in a set of NGK TR6 plugs
There are many people who have sprayed 200+, sprayed high mileage cars, etc , but there is always that chance.
so my suggestion would be 150 for long term and be certain your fuel pump and filter are up to par even at that level. The 200 area can be snuck up on with proper tuning, data logging and some race gas.
I always suggest an in car wideband or dyno the car to make sure the air fuel is safe.
Running a safe nitrous set up should be your first concern. I suggest that you reference the nitrous section at LS1TECH. The engine timing,correct plugs,fuel supply,and activation rpm are very important factors. Some people run on the ragged edge and express this procedure as the correct way to run nitrous. I'll tell you this...if you disregard the proper procedures for a safe set up...the odds are you car (engine) will not last for long...yes I run nitrous at over 600rwhp and I do attempt to run the car as safe as possible.
If your using the Zex kit that pulls back when fuel pressure goes.....here's the deal on my old car.
My old C5 had houdreds of bottles run through it (120,000 + miles) with the Zex kit with 125 pills. I then added 2 - 50 shot dry kits + the Zex (225 shot total) and never looked back.
The Zex kit is the safest kit out there. Premium gas is needed for security though. A tune won't hurt either !!
I fried a valve when I changed to a Money Maker hidden kit jetted @ 175 and hit my 100 shot dry kit.