cobrakiller1989

iTrader: (1)

I got my new selenoid for my NOS 5151 kit cuz the old one stuck. i hook everything up and go out to try it. DAMNIT!!! i flip the switch, no power at all, and i hear popping sounds. I started off with the 150 hp jets(#.070 and .053 i think) i hit the switch in second gear, it pulled really hard for a split second and then began to pop. so i put the 100 hp jets in to try the(.055 and .042) this was actually a little better, but still popped at 4500 rpm. I checked my plugs and they were very white, no color at all. so my last attempt was to put the .053 jet in the nitrous port and the .042 in the fuel. this was a tiny bit better, but still popped. my fuel pressure is at 40 psi at idle and 50 at WOT. any ideas on why i am running so lean?
thanks alot

bjm323

What have you done on the ignition side of things? Have you added anything as far as a MSD box? How old is the coil? We went thru this same thing once only to find out the coil was weak. We added an MSD-6 box and it took care of the problem. We then put a new coil in also. Hope this helps.

94-6spd

"I checked my plugs and they were very white, no color at all. so my last attempt was to put the .053 jet in the nitrous port and the .042 in the fuel."


I noticed that you put the bigger jet on N20 and the smaller one in the fuel. Is this right or did you mean to post it the other way.

That would definitely put your car running lean.

cobrakiller1989

iTrader: (1)

in the book it has
nitrous-fuel
150 shot 70-53
100 shot 55-42

i take that as the 70 for nitrous and 53 for fuel...am i coorect with this?

94-6spd

Every nitrous system that I have ever delt with has the fuel jet bigger so that you will run a little on the rich side to be safe. Try switching the jets around.

150 hp - 70 fuel and 53 nitrous

100 hp - 55 fuel and 42 nitrous

I'd bet this cures the problem.

Omar

Cobra, your jettings are correct. Do not switch them around. Every system and car kit is jetted a little different.


On the 70N/53N combo for 150HP, it actually is already a little rich. Dropping the fuel down to a 42-46 range which actually get you the 150HP.

I also had the same probs you described.


An MSD 6AL ignition box, new plugs, wires, and cap and rotor fixed it for me.

94-6spd

Omar, Are your nitrous jets larger than your fuel jets on the 5151 kit? Maybe the fuel infection kits are jetted different than the carb kits but that's the first I've heard of for the fuel jets being smaller.

Omar

Yes, on the 5151 kit, the jettings are just as cobra described.

I have seen so many different jettings for different cars and kits, that i stopped trying to form a "this generally works" type of list.

I have always suggested calling the manufacturer, getting a starting point, and then getting some dyno time.

GofasterFirebird

iTrader: (3)

Come on now!! On a carb car I squirt the fuel in at 7 psi. EFI I use 50 psi. Where would I need a bigger orfice to get the same amount of fuel in??? Bottle pressure is the same.


I actually use the 100 fuel jet with the 150 nitrous jet. How do you know you are lean??