Z28_LT4

I have been running a 100 shot NX and have been wanting to up it to 150.
Bryan Herter dyno tuned it and I need to know how much timing to pull for the 150?
I've been pulling 4* for the 100 shot with 93 octane. Should I pull more or just leave it alone?

My sig does'nt say it but my shortblock is new GM that now has 5000 miles on it and I'm running a Racetronix 255lph with the plug and play harness.

Does my setup sound like it would be alright with the 150 shot?

Joe B

With the mods in my sig....I pull 7 degrees when I run the 150 shot.......which is pulling one degree more than the standard rule of thumb of (2 degrees per 50 HP increase).......I've also found on the dyno that even pulling 10 degrees, Im only loosing around 11 HP, so being a little safer (with the conservative timing) it isn't costing much anyway...............and Im sure as long as it never goes lean...yours will be just fine for many many years, just as mine has......Im a few months away from 7 years of running nitrous on this bottom end, and all is still just like new(knock on wood)......Joe

CANTONRACER

Did he tune it for the nitrous as in having you guys run smaller fuel jets?

Z28_LT4

My car actually went lean on NX's recommended jets so I had to put in a 1 size larger fuel jet. But that was on the 100 shot, I never got a chance to try the 150 on the dyno. Should I try 2 sizes larger on the 150 shot and then read the plugs?

Thanks for the help.

CANTONRACER

I would call NX and tell them that and let them figure it out...they should be able to hit it right on the number.

Joe B

Just curious, what jets were you running for the 100 shot, and now the 150 shot.......

Z28_LT4

I run a 52 nitrous jet and a 32 fuel jet for the 100 shot and I haven't tried the 150 shot yet. NX's recommended jetting for 100hp is 52-31 and for 150hp its 62-35. I'm thinking I should run a 37 fuel jet and watch my plugs. If its running rich I'll just run a 36 fuel jet.

Is this right or is this way off base?

526 SS 96

If you are starting to lean out, I would get a fuel pressure reading before I changed anything further. Install a -4 T on to the fuel noid and check the fuel pressure during a run. If your pressure starts to drop you are running out of fuel. Checking your plugs after the fact is a risky tuning plan.
That is most likely the case, I had the same issue. I had the racetronix 340 lph pump and wire harness too .

Z28_LT4

I have a fuel pressure safety switch so I shouldn't have to worry about going lean should I? Wouldn't the nitrous feel like it was pulsing if the fuel pump wasn't keeping up? The fpss would kill the Nitrous activation as soon as the fuel pressure dropped and when the fuel pressure returned to normal it would activate again. Creating a pulsing feeling of which I don't have?

Keep the opinions coming this is very helpful. Thanks

526 SS 96

No, you would not feel any surging, it will just suddenly backfire through the intake. Most of the FPSS switches I came across where crap and didn't work.
Nothing is better than manualy checking your working pressures to verify your electronics work properly, especially when you could be facing thousands in potential damage because of a defective sensor. How can you be sure of the setting of your FPSS, they are not a plug and play item, you have to check them and adjust to your cars needs. For all you know it could be set too low. If you are leaning out and you just put in a bigger fuel jet, you have a supply issue.

Z28_LT4

I will buy the T fitting but I'm not sure how I could see the gauge while driving? My gauge only has a hose on it maybe 12 inches long and it won't reach the windshield. I've been thinking about buying a Nitrous pressure gauge and Wideband gauge from Dynotune, I guess I'll have to buy a fuel pressure gauge from them too.

526 SS 96 what did you do to get enough fuel? I was under the assumption that the Racetronix pump was more than enough for my car

I have a AutoZone fuel filter on it. Is there a such thing as a high flow filter that fits are cars? I'm also running the original fuel regulator that came on the car, is it a restriction?

526 SS 96

The gauge set up is for dyno runs where you can stand close enough to the car to get a reading. I wouldn't try to read the gauge while spraying and driving . If you HAD to you could just find a way to make the hose longer, but some dyno time is still your best bet.
A little money on the dyno can save you alot on the long term scope of your project.

"I've been thinking about buying a Nitrous pressure gauge and Wideband gauge from Dynotune, I guess I'll have to buy a fuel pressure gauge from them too."

Save your money, you will need it for dyno time. Once you get the car sorted out, just regard the N2O as a fire and forget weapon.

Q: "526 SS 96 what did you do to get enough fuel?"

A: This is kind of a touchy subject. I was told by my dyno guy to change the fuel line to a larger diamiter (3/8 stock to -8 AN) because the line could not carry enough fuel. Racetronix insisted that I made a mistake with the wiring harness . I checked the voltage and it was ok, so I changed the lines on the car to -8 supply and -6 return. The problem was solved to the 100 shot, but there was no chance for the 150 (kept dropping pressure). I think I just had a bad pump and it should of been changed out, but I had such a hard time with racetronix that I didn't want to have to argue over it. I ultimately ended up going with a complete weldon fuel system. It was very expensive, but I have not had 1 single supply or reliability issue. This is not ment as a dig on racetronix, they make good products, but I did have a very hard time trying to explain my problem. If you can, I would try to make sure you are getting enough voltage to the pump. Also, if you have not done so, I would install the voltage booster that racetronix offers (in line with your harness). If that does not solve the problem I would ask to exchange the pump for another one. The 255 should be enough for your car. I just installed a hot cam and NX kit for a ls-1 car, and he went with the racetronix 255 pump and harness and didn't have an issue at all with fuel pressure. So start with the basics (pump voltage & pressure during a pass), and work your way back from there. It sucks, but this is how the car game is.

P.S. You do not need a high flow fuel filter. I don't even know if any one offers such a thing in this case, but you won't need it if they did.

Z28_LT4

I think if this problem ends up being fuel pressure related I'll just buy a standalone fuel system from Nitro Daves or Harris Speedworks. I've been thinking about relocating my battery any way.

Is there any down fall having a fuel tank under the hood of a street car?

PoorMan

Wow; so how long you been doing this on a stock block? 460 rwhp?? No way I would go over 500. Good luck. I wish I had the money to do it to my setup.

Z28_LT4

I've only been spraying for three months but the engine has been in the car for 5 years. I think once I get everything figured out that there won't be any problems and It'll run for quite a while. If not I've been thinking about building a 383 with a 200 shot