I am finally getting around to tuning my dry nitrous setup and am having problems getting enough nitrous. I have a pretty serious 0.071 jet that should be good for about 170 HP but I am not getting the performance I would expect. 0-60 is about 4.6 on the bottle vs. 5.4 on the engine. It is also really rich at about 0.65 lambda on the bottle with a tune that should be more like 0.75 lambda.

Should I start by drilling out the jet to something enormous and let the super powershot solenoid act as the only restriction?

Thanks,

Jeff

 

0-60 isn't really a good way to tell IMHO. Too many variables cause the numbers to show strange results. I've ran to 60 in mine well under 5 seconds to over 10 seconds (lots of tire smoke ).

Are you using street tires? How much spinning? Is the N2O progressively controlled? 170 is a lot of spray and you should easily feel the difference.

 

Yeah, I agree about 0-60 not being a precise measure, but it was the most tangible metric I had. As for your questions, yes standard 255/50 street tires, but not as much wheelspin as I would like! They fight for traction through first but have no problem hooking in 2nd. I am using a progressive controller but past 3500 RPM it is wide open so aside from the first bit of first gear there is no reduction from the controller. I have verified the controller shows the PW at 100% through 2nd gear.

Perhaps the most accurate indicator of the size of the shot is the AFR and injector pulsewidth. On the stock tune injector PW runs about 55% and just under 0.80 lambda, whereas on the nitrous tune it is right around 80% PW but only 0.63 lambda. Accouting for some desired extra richness on the juice (say lambda 0.75) the nitrous tune is setup for about 40% more fuel (power). With the stock engine being somewhere around the 250 HP mark that would work out to perhaps a 100 shot worth of nitrous. However, at 0.63 lambda it looks like I am only getting about a 75 shot worth of nitrous. Running that through a performance calculator gives me about the right improvement in 0-60 time so everything adds up. Don't get me wrong I do feel a difference but not really what I would expect from a 0.071 jet.

The plumbing is all pretty standard NOS kit stuff: -4AN supply, -3AN to the nozzle, Super Powershot solenoids and a filter. The kit came with a standard supply line (14 ft IIRC) which I coiled in about 8" loops under the carpet to take up the excess. I doubt that makes much difference though. No elbows at all, just a tee for the pressure sensor joined to and another tee for the purge joined to the main solenoid. I see about a 50 PSI pressure drop when I start the spray so about 850-900 PSI should be showing up at the inlet to the main solenoid.

There is snow on the ground now so more testing will have to wait until spring but I'll try drilling the jet to 0.125 and see if that helps. If not I may swap purge and main solenoid guts, since I had an earlier problem with the main valve sticking open, and if that still doesn't work maybe ditch the Super Powershot altogether and pickup a 250 HP pulsoid

 

I've had similar issues caused by an obstruction in the nitrous line.

Mine was a piece of teflon tape blocking the passage from the inlet fitting into the nitrous solenoid.

It's obvious that in your case the restriction isn't the jet, so drilling out the jet won't fix the problem. It might be an adequate work around, but it's not actually fixing the issue.

I am guessing that you don't have access to a dyno where you are, as you are testing using calculated 0-60 times and a Lambda meter. Diagnosis is tough without a more consistent measure of power/performance.

If you drop the jet size down, how does the car react? I can't imagine that it slows down with a 65 jet in it. That would help us verify that the restriction in the system isn't the jet.

I would check the lines for obstruction, and disassemble the noids looking for obstructions.

It sounds like you have taken the noids apart already. I've made mistakes and put springs back on top the plungers that were too big. The magnet still easily overcomes the spring, but the spring is so big that when it is fully mashed the plunger is only opening about .005 - .007. It was tough to find because the noid still clicks, and on disassembly it appeared to be working correctly.

 

Thanks for the tips. I will start looking for obstructions. Since I don't see a large pressure drop at the pressure sensor just upstream of the main nitrous solenoid the obstruction is presumably at or after the solenoid.

I did not use any tape on the system but there is nothing saying paste can't break loose and get stuck somewhere. I will also look again at that solenoid. The cylinder bore was damaged which was originally causing it to stick open. I fixed the problem of it sticking, but maybe now it is being prevented from opening fully. I will swap the guts of the main and purge solenoid and see if that helps.

You are correct, I don't have a dyno anywhere close [that I know of] but assuming the tires are hooked 0-60 is a decent measure of performance. I picked up a set of drag radials so I should be able to get more consistent launches now

 

The zero - 60 test is more fun anyway, lol.