well i hit the dyno today. baseline pull went great. 303hp 335 ft lbs. so we got my fuel pressure set on the nitrous fuel system and go to make our first run.i have some one watch the fuel pressure. i get on it and the N2O kicks in and starts poping. so se immediatly stop. fuel pressure was fine the whole time.so we check timing. 34 degrees. so we drop it down to 32. make another pull. same thing. so we were stumped. at this time i was open header. so we bolted back up my exaust thinkin maybe that will help richen it up a little. try another pass. SAME THING. so we make a pass without the bottle. now its poppin a little off the bottle. so we decide to put in bigger jets.went to 74/78 from 71/74. now it doesnt pop off the bottle and put down the best number ever for full exaust 307 hp/ 353 ft lbs. so we say try one more bottle run. it pops!!! what the crap is goin one here. the only thing that i can think of is that my ignition isnt quite strong enough and its killin my spark sometimes. all i have is a stock replacement accell HEI and some parts store wires. im runnig standard autolite plugs gapped at .045. waht do u guys think?

i would like to add two things, i was running about a 70/30 mix of 94/112 octane fuel. and the popping off the bottle would only happen at about 5- 5500 rpms and about 4300 and up on the bottle.

Back off that gap to 35. Nitrous likes the smaller gaps! Goodluck! ;)

what about a colder plug?

Where in the heat range from hot to cold plugs are you using now? How do the plugs look after your dyno session and nitrous?! :D

here is the thing with that. i dont know what im at now. i just know i use a autolite 605 plug for vortec heads. i ahevnt looked at them. what should i look for?

Can you describe how the plugs looks? What color is the base ring-black,tan? How does the ground strap look? See Pat Kelley's site as he has good pics of what plugs should look like when tuned properly! graemlins/waving.gif

What was the bottle pressure? Since you were on a chassis dyno I assume they had a wide band oxygen sensor hooked up that would tell you the A/F ratio?

What system and jetting for the nitrous system?

After the pull did you pull ALL the plugs?

After you dropped the timing to 32* for the nitrous, did you bump it back up for the motor runs? That may be causing some popping.

yea..make sure you have a N20 pressure gauge...and make sure all of the lines are leak free. open the bottle valve all the way. Shoot for 950 on the N20 gauge. What N20 jets(fuel and N20) are you using? also what system is it?

Popping usually means not enough fuel. I had the same problem on my nitrous runs. It was not a matter of fuel pressure, it was a matter of fuel volume. I stepped up to a bigger fuel pump, 130gph Holley mechanical with a regulator, and the popping stopped. I gap my plugs at .35 and set my fuel pressure at 6.8 psi. My timing is set at 34 and I run a 30/50 mix of 110 Sonoco and 93 pump gas.

i will pull a plug tonight and see what it looks like. jetting was .047 n20/ .053 fuel. the system is a sniper kit. i added a super high flow valve and put a gauge in it. gauge read 930-950 the whole time. has a ntrous dedicated fuel system with a holley blue pump just for teh n2o. dyno had a a/f meter but we have allready proven that to be wrong a couple weeks ago when some of my freinds with "in car" wideband a/f meters dynoed and they said perfect and his said way lean. so i dont know if i should trust his but it was in the 14s on a/f

Did you purge the nitrous system a few times before the dyno pull? What HP setting our you using. I've ran a 150 shot on a stock motor, pump, ignition ect.

If you can;t even purge the system at 3500 rpm and instantly hit 5-6000 there are serious problems, sounds like you have the plate on backwards? (upside down)

looked at plugs today. light tan color with some white. dyno sheet can be seen here.
http://idahostreetracing.com/gallery/my-car/NOS_dyno

u can see where it starts screwin up at about 4200 rpms.

k guys, i went out for a drive tonight and i noticed something when accerating from about 45mph and rollin into it so it wont downshift i notice a spot where i starts accelerating harder. like the secondaries are opening. could that be part of it? ive been racking my brain and cant think of anything!!!

If you're in the 14's on the a/f ratio meter you're way too lean for nitrous. I'd run a much richer mixture and a set of fresh plugs gapped at .035. We've seen 60 hp gains from spark plug changes.
Another thing to check is the secondary opening of the carb. Introducing fuel and air below the carb will disturb the air flow through the carb and may cause the secondaries to close off. If the plate is upside down, it's even worse. If you can get a DP carb, use it.

Is your fuel pump electric or Mechnical?

Easiest and cheapest thing to do is close the plug gap to .030 to .035. I had the same problem in my Chevelle which is all set up correctly for a 275 hp shot of nitrous. I got out the nitrous book and it said you must have a closer gap because of the increased cylinder pressure. As soon as I did that, problem solved and what a rush!! Make sure you are using the type of plug recommended for nitrous. Colder and short ground strap. I am running A.C. R42T in a big block. Then I would start looking at the weak ignition. I have a MSD 6AL with a timing retard module hooked to the GM HEI distributer. Good Luck :D

they are both holley electrics. blue for the n2o and red for the motor. the a/f on the dyno has been proven to be wrong and it was at the end of my tail pipe. im investing in some ignition. i got a bonus so i have a little extra money. i need a new dist. anyway.

I don't think I would use somebody elses a/f gauge to presuppose how the dyno's a/f ratio meter is calibrated. I would start with my n/a setup and tune it up for the best power before ever tackling the nitrous. I'd be looking for 12.5 to 13 n/a and 11.5 or richer on the bottle. The a/f ratio requirements are different for nitrous, about 9.5:1, so you end up with a compromise between the two, depending on how much gas you shoot. The consequences of being a little too rich are less than the consequences of being a little too lean.

How much pressure on nitrous? (fuel)

Did you free flow your nitrous fuel system when trimming it? So it was 5psi on a free flow condition trough your jet size?

What are you going to do when the ignition really wasn't the problem?

well first ive always needed a distrubutor, it was just working OK. we just set the pressure with all the lines hooked up. the dynos a/f is off and was documented by a AEM and a FJO wideband A/F. the thing didnt even take a reading half the time. i just dont see how it could be fuel pressure. i would think that a blue pump would flow enough for the nitrous system.

To properly set flowing fuel pressure you either take the plate off and put it over a bucket or put the fuel jet you will be using at the end of the line and fitting. You then open the fuel solenoid and adjust the regulator with the fuel flowing through the jet. If you do it without the fuel flowing through the jet, with the solenoid closed, you can set the pressure wrong.

thanks i will do that. we just turned on my pump and tried to set it that way.

You can also purge the sytem and have someone watch the gauge to see what the pressure does when the nitrous is activated. Can you even purge the system at 3000rpm? Are you using a holley reg?With the regulator dead headed it will be 1-1.5lbs high until the sytem is activated.

The Holley blue with the supplied regulator is the pump I use for my Nitrous fuel supply and it works fine for a 275-325 h.p. shot of nitrous on my Chevelle. Are your supply lines big enough? I still say its your plug gap first or ignition. Did you try the plug gap yet???

i have -8 an line from the pump to the regulator then it goes down to the 5/16 line they provided. i got a full msd with 6a box im goin to pu it. im going to close the plug gap to about .037 and ive got a leed on a 750 dp for pretty cheap.

I would take that plug gap down to .035 or less just to iliminate that as a possible problem! I run mine at at .033 all the time and the car is mostly on the street. As far as your lines from the fuel pump, that is exactly what I got and is works fine.

thanks. im goin to test it out tomarro so i will see