Maybe it's just me, but I can't see my first post. I'll repost it:

Ok I have everything working correctly, and I'm almost ready to go. I changed to BKRE6s, and gapped them to .040. I adjusted my FPSS so that it only activates when above ~58psi. My last question before I go for my first run is how much room for error do we have on the listed NOS PSIs?

According to the tables
50shot, 62psi;
60shot, 67psi;
70shot, 72psi;

Right now with a .034 bypass jet I'm getting about 61-62 psi, so I'm right on for a 50 shot. I'm assuming NOS left some room for error, and the listed psi is already a little rich for safety, but does anyone know by how much? I'm just trying to figure out what kind of a range I should be in.

Also at idle if I activate the first solenoid I get 72psi with my .034 bypass jet at 1000psi. However, when I go to make a test run in 1st, 2nd, and 3rd gear I get 62psi Any comments?

Thanks in advance
-hype

 

Well first, at idle, your car is using the minumum amount of fuel to sustain a 700 rpm idle, so your fuel pressure should be higher than doing full throttle runs. You do have some room for error on the fuel, but thats why you should be checking your spark plugs for signs of detonation (small black or silver like specs on your spark plugs) Now heres the fun part, you can't just check one and call it good, you need to check all of them. You can't drive the car around after a run either, you need to shut it off asap and check them. Best way I found was to do a nitrous run on an empty stretch of road, and as soon as I let off the gas, I would shut the car off (not all the way or your steering wheel will lock) and let it coast to the side of the road, then pull the plugs, this way no carbon deposits have reformed on your spark plugs. (Disclaimer: You need to be very careful when doing this, I am not advocating shutting your car off while its moving, nor advocating using nitrous on the streets, simply sharing what worked for me. end disclaimer) It also helps if you have an EGT, that way you can see if your running rich or lean. Good luck!

 

well said Matt...

 

Wizza, update your sig. Unless you're running Nitrogen Dioxide (N02), you should change it to N20.

 

Yeah I plan on pulling my plugs to read them, much like you described. My main question is what was your personal experience from the past; i.e. if you could have done it again what would you have done differently. I'm sure most of you would be sure to run at least xxx psi over what you thought was the miniumum, or running a xxx shot you had to get xxx psi to prevent detonation. I know all cars are different, but it would be nice to have some real world experience/data to back up the theoretical stuff that's on paper.

Very thorough. I had already thought this out, but hopefully it'll save someone from having a bad experience

EGT would be nice, but it wouldn't really help prevent initial problems from a first time spray. I do plan do dyno soon so I can be sure of my A/F, but so much happens so quickly I can see how those who don't really know what they're doing or get greedy blow motors.

Always good information/advice to be found here.
-hype

 

I think NOS built a lot of "head room" into those fuel pressure specs. I found that my 50 shot work best (plugs looked best, EGT's were happy) around 58psi FP, and the 70 shot worked best around 67-68psi.

Like you said though, each car is different.

 

Do you have any idea what jets you were running to get your psis? Right now the only chart I have is Thomas's. I also find it strange that he shows he was able to run a 50-85 shot using a .042 bypass jet. I suppose that meant he was getting 80psi with the .042 bypass jet, but I'm not even in the ballpark for that. Yesterday while I was testing I only got ~67 out of my .042

50 .032 .042
60 .034 .042
70 .036 .042
75 .040 .042
80 .042 .042
85 .045 .042
-hype

 

I had the same chart. I ended up using a .042 jet for about 68psi with my 70 shot, which is what I settled on. I never went above that.

I don't recall what bypass jet I used with the 50 shot, sorry. However, it did take some testing of different jets to find one that worked.

 

He was able to get those pressures with that bypass jet because he had switched to the upgraded fuel pump, once you change over to the walbro 255lph you will have that pressure. The stock pump will never push that much.

 

Good call BJJ. Thanks, now I understand why my readings are way off from most of the others. I was just concerned that I was only getting ~62psi on a .034 bypass jet whereas others were getting 100psi on a .042 I guess I'm sticking to a 50 shot then because I'm trying to avoid buying a Walbro and a FPR for a while. I guess I could always go buy some smaller jets as well.
-hype

 

Ok last question:
For those of you who sprayed on a stock pump; did your pressure slowly bleed off at higher rpms? Right now with my .034 bypass jet my pressure bumps up to 62psi and slowly bleeds to about 59psi before redline. My car only has 61k and my pump has been pretty consistant when tuning fuel pressures, so I'm just looking for some comments on your experiences again
-hype

 

Typically two things happen when using the stock pump with n20. First, you'll see a gradual loss like you are describing. I didnt have a gradual loss but I oouldnt get my fp to rise above 50 psi using any jet. The second thing you may see is a lag of sorts. You'll spray and your fp gauge for example will read 50 psi and when you let off the spray, the fp gauge will spike up to about 60 psi then back down. The gauge isnt wrong, the pump is just surging, so make sure you go by what the constant reading is not the peak reading. My pump hung in there for a couple of weeks until I noticed my idle fp would be low or inconsistent, that's when my fp started to go out on me and I knew it was better to be safe than sorry.

 

Cool thanks for the comments DCmax. I tested several jets, and the highest I can get my FP to consistantly maintain is about ~60psi. The ~60psi is the low point when it bleeds from 62 down, and when I let off the gauge will read about 70psi before it goes back down to normal pressures. If I activate the first solenoid at idle I can maintain a constant 70psi, but while driving I get 62psi again.

I don't have a problem with upgrading my fuel pump, but I'd rather not have to deal with a FPR as well. I was considering the Walbro 190lph High Pressure pump that came out recently, but there weren't any flow rates listed yet. Hopefully a HP 190lph will let the stock FPR do its job and give me enough pressure to increase my shots. I believe Chunger first pointed out the HP 190lph, but since I can't search I can't find the website to buy it from.
-hype

 

where are these jets that you all speak of?

 

does anyone have a hook up for jets? I need a .69

 

Hey guys, what should the fuel pressure be at idle and at wot?

 

32 at idle
43 at wot-ish

 

I just had my fuel pressure installed and it was reading 33.3 at idle. Havent had the cahnce to go wot because of bad weather. should it be 43 at wot in any gear?

 

yes at any gear.
33 is probably right. yours is digital? your guage I mean.

 

Yep. tells me to the tenth.

 

I am 38 at idle and 47 at WOT??
D

 

Update: Today I installed my Walbro 255lph HP pump, and I'm definitely getting a lot more fuel. My fuel pressure with the stock regulator is 40psi at idle and 49psi at WOT. I wanted to tune my fuel for nitrous so I used the .042 jet and got 95psi (BTW what's our injector lockup again).

Speaking with Iron Lung once he mentioned to me that he runs no bypass jet in order to bring his FP down. My next test run I ran with no bypass jet, and I got 72psi that creeped up to 76psi. This should be a little rich for my intended 70 shot, but at least it's down from the 95psi I got earlier. Do you all have similiar experiences with dry kits and a Walbro?

I'm planning to dyno this week: 1 run NA, 50 shot, and 70 shot so we'll see how my A/F and everything else goes. I'm thinking my next purchase should be a Fields AFC so I can tune down both my NA and nitrous fuel rate.
-hype

 

I guess you don't have an aftermarket Fuel Pressure Regulator.
I would get one if you dont. You don't want to depend on your N2O for ANY performance.

 

What exactly are you trying to say
-hype

 

I was telling you that you are losing HP because of your increased fuel pressure. I guess you knew that huh?

 

Ok yeah I realized that, but I should be relatively close once I move up to a 70 shot. That's also why I mentioned the SAFC. Just to wonder were your PSIs as high as mine are? I'm running my bottle at 1075psi btw.
-hype

 

well, I just know my experience. when I sprayed (with less pressure), my psi would gradually increase to about 95psi. I spoke to a holley engineer about not using a bypass jet, he told me that you can ruin your FPR if you don't, the plenum in the FPR isn't made to handle that kind of vacuum. Something to that extent. Goodluck.