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I just installed a100 shot NOS system in my '78 280Z. It's a dry system that uses the stock injectors for the enrichment. Because the supposely limit for a dry system is 80 shot , I tricked the cold start injector to kick in every time the NOS switch is engaged. The car pulls like a bat out of ****, front end rises about 2 inches on take off and the shift to 2nd breaks the rear tires loose (P225/50VR15) for about 35 ft. before there is any traction. If I engage it in 3rd gear at 70mph, about 3-4 sec later it will pass 100 mph when I shift to 4th. Before , I noticed the engine would run out of steam at about 5K rpm, with the NOS engaged, it pulls hard to 8K. The only problem I'm having is the engine will sometimes backfire through the intake(I can see a grey smoke) shooting out of the front grill at speed (about 75mph) when system engaged. It never did that before with 70shot jets and I didn't used the cold start injector. Could the backfire be caused by the intake manifold, I heard the Z manifold was only designed the flow air and not fuel threw it. Any ideas or suggestions are appreciated the fixing thie BIG problem.
 

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It shouldn't have any distribution problems w/ the Z's intake manifold as you are running a dry kit as nitrous oxide is a gas. With a wet kit you could have problems due to the gas that would have to travel through the intake unless it's a port injecting fogger kit. The backfire could be caused by a couple of things. Most common would be to rich, but you say it's coming from under the hood. What kind of revs does this happen at? Nitrous should only be engauged above a certain rpm, generaly about 3k or more. If it is backfiring through the intake you are most likely running lean. Do you normally monitor your bottle pressure? When the bottle pressure is higher you have to run more fuel to get the correct A/F ratio. Check your sparkplugs to see if they show a lean or rich condition. Also look to see if the electrodes are melted/damaged at all. This is a sign of detonation, very very bad to have. It can be caused by too much timing or too little fuel.

Kyle
 

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i agree with kyle... you're running lean. turn the cog on your air flow meter to run richer, upgrade your injectors, increase fuel pressure, or anything else that will increase fuel flow into the cylinders. you will blow your engine if you continue to drive your car while it's lean. good luck.
madcowz
 

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If you feel you are running to lean, try the rising rate regulator it will help a BUNCH! It is a major seat of the paints feel on my modified 280Z, no nitrous on mine. However does sound interesting.
 

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The dry nitrous kits use a fuel management unit that spikes the fuel pressure up an outrageous amount. Not sure if they are adjustable. If so try running higher fuel pressure with it. With a 100 shot you will definatley need to decrese timing from stock. Rule of thumb is about 2 degrees per 50 hp you add.

Kyle
 
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