I'm running a NOS dry kit, that I've converted to a wet kit, using a NOS Super Powershot solenoid, and a fogger nozzle.

I've verified that the wiring is good, and that fuel does pump through the line when the solenoid opens.

I have a nitrous pressure gauge, a fuel pressure gauge, and a wideband o2 installed on the car.

Running N/A the tune runs at 13:1 at WOT.
Fuel pressure runs at 40-41 PSI. Good and solid.

When I first went to the 100 HP jetting (46 n2o and 31 fuel) I had problems with it running lean (really really bad lean). So I pulled the 31 fuel and replaced it with a 33 fuel (the fuel jet for the 125 shot), and by watching the stock o2 sensors the AFR looked in the ball park. I did this before getting the wideband.

Fast forward a few months. I went to the track this past weekend, and with a full bottle nice and warm I had ~1100 psi pressure.

I had some minor shifting issues NA (car was staying in gears too long, past the optimum shift point) so I loaded a new tune before running my first nitrous pass.

The first nitrous pass went by but I forgot to look at the AFR during the run. Ran a 12.7 @ 108.18

The next nitrous pass I got in it right off the line, around the 330' mark, I looked at the wideband, and it spiked to 15:1 it was ranging between 13.5 and 15.5. Moving around pretty quickly, so I got out of the gas in a hurry.

I went back to the pits and upped the fuel jet to a 37 (which my calculator says is the fuel jet for a 150 shot) and made another pass.

Again, I nailed it off the line, the car ran really strong and felt smooth, but again the AFR was real lean. It showed 14.3 or so , but it was steadier this time. Ran a 12.6 @ 107.xx

So I'm left to wonder what the deal is. The fuel jets are clear. The fuel pressure stays solid at 40 psi during the run. But the AFR goes way lean when spraying.

The fuel side of my system comes off the fuel rail, goes to a T where my fuel pressure sender is attached, then into another T with the FPSS installed, and then into the solenoid, and out to the nozzle.

I was kinda expecting that the calculators would be slightly off, but I wasn't expecting them to be that far off. Based on these numbers, it appears that I need to make the fuel jet larger than the nitrous jet. Is that normal?

 

Congratulations on the DIY nitrous. Man, I love creativity. Good work using the O2s/wideband with some cautions testing/tuning.

I looked up fogger system baseline tunes. It looks like a .032 jet supports 300 hp with 8 nozzles, not just one. I couldn't find the jet recomendations you mentioned, not that it's a big deal.

I think your problem is the inside diameter of the fogger nozzle. Looking at it closely I think you will find the ID to be .035 or so. It is your jet size. Which is why you see very little AFR change with jet changes.

If you are not using a "fogger" nozzle then your restriction is somewhere else.

Let us know.

 

This is the nozzle that I'm using: http://store.summitracing.com/defaul...5&autoview=sku

The fuel side of the system consists of:

90* elbow fitting from fuel rail to
-4AN braided line to a Tee
the "top" leg of the tee goes to my fuel pressure sender
the straight through leg goes to another tee
the "top" leg of that tee is where my FPSS is located (set for ~36 psi, it will pulse the solenoids at idle from a lack of fuel pressure)
the straight through leg goes into the Super Powershot fuel solenoid (NOS-16080NOS) and then out of that into a -3AN line to the Fogger nozzle noted above, which is mounted in my intake elbow.

I'm going to check the flow on the fuel side and see if I can locate a restriction.

 

Last Saturday at the track, before making nitrous passes, I loaded a tune to the car. The only changes to the tune were shiftpoint changes.

I made the first nitrous pass and didn't get to look at the WB gauge.

On the second pass, I looked at the gauge right at the 1/8 mile mark and it was over 15:1, so I got out of it.

I put a bigger fuel jet in it and made a third pass, it was still lean (14.3:1).

With that I was finished for the day and we drove home shortly after.

Since then, I've been trying to look for reasons for it to be lean. One person suggested a problem with the seal in the fuel solenoid being swolen and causing a restriction, another mentioned that maybe I've maxed out the flow capability of the nozzle I'm running. I tried looking on the 'net for what the nozzle I'm running can flow, but couldn't find it anywhere.

Based on the calculators a .047 nitrous and .028 fuel is a 100 HP wet shot with a single nozzle.

Back in April, at raceday I was running that and it was super lean, so after race day I swapped to a .031 fuel jet and then discovered the brass shavings in the .028 jet. The stock O2's looked ok after putting the .031 jet in it so I left it like that. Since then I've added the wideband, nitrous and fuel pressure gauges, and haven't run the nitrous until last weekend. Friday, before going to the track, I armed the nitrous system but left the bottle closed, and hit it. I watched the AFR, but it didn't change as much as I thought it would. I was confused, but considered that maybe the high pressure nitrous flowing past the fuel would help create a vacuum and pull fuel with it.

So the jet I ended up putting in it Saturday was a .037. WAY bigger than the .028 called for. When it was still lean, it really perplexed me.

So last night I get out there with a friend, and we get to talking about it. He recommended just putting a bigger jet in it and trying that, but my brain said that there had to be a reason that the car needed that much more fuel jet, there had to be a cause for it. So we pulled the lines, pulled the elbow off the car checked the jets blew in the nozzle, and tried finding problems. There appeared to be one tiny piece of something in the fuel jet, and my wife said that when my friend blew through the nozzle, something copper came out. But I never could find anything on the floor.

So we flow tested the fuel side of the system, we tested with the line just open, then with a .037 jet in a spare nozzle, then with the .041 fuel jet in the spare nozzle. We also tried it with no jet in the nozzle. It seemed to flow fine.

So we put the car back together with the .047 nitrous and .041 fuel jet and went out and drove the car. The AFR went to 11.5:1 with no nitrous flowing (just fuel flowing), so I opened the bottle, purged and with 900 psi pressure, the car hauled ***! AFR was still 11.5:1 too

So, we "tested" it a few more times, and went back to the house. After discussing that it was richer than I want it, we decided to up the nitrous jet .

We stuck the .052 nitrous jet in it and went back out. This time, when spraying (still with 900 psi pressure) the car ran at 12.5:1, which is about where I want it.

The car was scary fast too. When I hit the gas at 60-ish, it spun the back tires till about 70 MPH and before I knew it, I was at the top of 3rd at about 115 MPH.

Fuel pressure was solid, and the AFR was solid at 12.5:1 too.

So I'm not sure what we did, but I guess there was something in the fuel side keeping it from flowing right and we got it cleared out.

I might have to hit up Alabama International now...

 

That's some very good info Lee, thank you for sharing!