Some recent nitrous notes

the head · 06-19-2005, 10:40 PM

Well I did some jetting last Friday night. I've gone from a first generation NOS nozzle to a soft plume nozzle, to now running a ny-trex nozzle. The ny-trex appears to be the best one as the mph and times changed as I jetted it. Also, my previous jetting attempts with the other nozzles would eventually show a lean indication and no gains in power. I had pretty much attributed this to a poor fuel mixture and the fact that our intakes were never designed to flow liquids/aerosols. If you have ever popped the throttle body off, you'll see what I mean. The main difference with the ny-trex nozzle is that it sprays at a 70 degree angle instead of the industry-standard 90 degrees. This has definitely allowed it to get the mixture off the side of the intake inlet pipe and more into the air stream. With no changes to jetting with the ny-trex nozzle in place, it showed a somewhat rich mixture instead of a somewhat lean mixture.
I played with the jetting, going as high as 103hp jets but the check engine light came on towards the end of the run (flashing) and then went out as I was on the return road to get my timeslip. The data logger showed that I had good mixture (actually too rich) and timing was still OK meaning no detonation. So I'm thinking a sensor became unhappy as a result of that jetting and I tuned it back down to about a 80hp setting to keep things somewhat happy.
Some of you might notice that this was only a 1 second gain from the all motor times but I was unable to activate the nitrous as soon as I wanted to due to some traction issues. With the 50-60hp jetting it would grab but with the bigger jets it will not with the tires I have. I'm most likely going to play with it a little more to get the jetting just right. My next step with it is to go with a direct port and right now I'm content to just run the one nozzle and get about 100hp from it with no problems. What this is pointing me to is the Unichip programmer since I can also put a timing retard table in it for when the nitrous is running. I would think that with the mods I have at this point (CAI and the exhaust) that the programmer would help anyway but I just wish it would've eliminated the speed limiter and, alas, it does not. So I'm more or less waiting to see what else may come up. I'm sure I could always get it and then sell it off if something better came along. I'd just really like to do it once, though. With long tube headers eventually coming and the Stillen fuel system upgrades (part of the supercharger - I don't know if they will sell it separately) there are several directions to go in.
With the 103hp jets in the truck went over 98mph in the heat with a delayed activation. It was making the power but I want to be certain of what kicked that light on before I go back.

Vegas04 · 06-20-2005, 12:16 AM

thanks for letting us know. Nitrous is starting to sound pretty tempting. You can only use when you want to and you don't really deteriorate reliability or fuel economy. Do you have the tall or short gearing? Also, what size tires are you running in the back? I'm definitely excited about seeing your direct injection setup in the coming months. From what I hear the direct setup is a little safer b/c you eliminate the risk of blowing up the intake before the throttle body. Any truth to that?

the head · 06-20-2005, 06:35 AM

I have the 3.36 gear.
At the track I run 29" tall tires so that I don't hit the speed limiter when on the spray. Using a gear calculator it is equivalent to roughly a 3.70 gear.
The backfires that cause the intakes to blow off can happen for a few reasons:
1) Activating it at too low of an rpm - this allows the cylinder pressure to escape during the overlap of the cam when the intake and exhaust valves are open. Sometimes the pressure will not be fully relieved through the exhaust and this causes the still hot exhaust to travel back up that respective intake runner which ignites the air/fuel mix that the other cylinders are trying to suck in.
2) Fuel puddling from a bad mixture can also cause this. It is usually combined with a backfire.
3) Shutting the throttle with the nitrous still going full blast. This causes a backfire as well.

But yeah, going with a direct port allows not only a lower chance of puddling the fuel, but also an even distribution of nitrous/fuel per cylinder. The single nozzle does a decent job but not as well as each cylinder getting its own shot. I'm still trying to figure out how much power you can run with it. Based on what the Stillen numbers are coming back with, I'd imagine with good engine control that 100-125hp is still a safe amount. Due to the size of the intake runners I'll be going with 90 degree nozzles there as this will be roughly in the middle of the air stream for each runner. The 70 degree nozzle would be spraying onto the runner wall due to the reduced diameter of the passage. I'm not sure when this is all going to happen. I should get a controller first before going with the direct port to play it safe. But I also know I can go with about 80hp and start with that. But jets for 8 nozzles would be expensive and I'd like to spend as little time as possible dialing that in.

Vegas04 · 06-21-2005, 12:36 AM

I'm confused by the beginning of your post... 29" tire is smaller than stock size, right? So a smaller tire means that your engine computer and speedo would show 110 mph (or whatever the max speed is) but you would really only be goig like 102 (approx.) So how does running a smaller size tire keep you off of the rev limiter? I would think that you would want to run a large enough tire that you wouldn't hit the rev limiter in fourth gear and no larger.
Also, if your race tires are larger than stock, you would end up with the equivalent of a numerically lower differential gear ratio, right?
The states, from my understanding, seem to conflict with one another, can you clarify?

the head · 06-21-2005, 06:14 AM

The rev limiter isn't affected. The speed limiter is. I put the tire diameter into a calculator and then plugged in my trap speed on nitrous - 98mph, roughly - and then determined how much speedo error it would give it. Since I don't go 114mph through the quarter mile that gives me some room to play with. The shorter tire is like putting in a steeper gear in the rearend. This helps with acceleration. In my case just running the shorter tires drops my ET by 0.15sec on average. The 29" tire throws the speedo off, but not enough to activate the stock speed limiter.

Aries · 06-23-2005, 11:51 AM

nice notes Eric.
I'm headed back to the track this next week with the nitrous set on 125hp and the dry shot converted to wet. I too am very happy with the Ny-Trex nozzle and it's spray pattern. It got me arround my buddy's lightning last night from a roll, and I should definately see the ET difference on a 29" tire with the 4.10 rear gears.

the head · 06-23-2005, 01:10 PM

Good luck with it. What day are you headed out there? Hope the leg is doing better.

92TripleBlack · 06-23-2005, 01:24 PM

The only reason I haven't installed NOS is I would use it all the time and continually have to go and fill the bottle. I want something I can use all the time and not have to keep making trips to the fill station like a SC or turbo or stroker conversion. Good numbers head.

Aries · 06-23-2005, 01:55 PM

Quote:

Originally Posted by the head

Good luck with it. What day are you headed out there? Hope the leg is doing better.

Hoping to get out there next sunday (pending the woman's approval)
The leg is doing much better, and we may bring the race car out and run it a bit too.

the head · 06-24-2005, 12:05 PM

I don't know if I will make it out there. I'm real curious to see what kind of MPH you're turning. My jetting calculator says that I should be running about 90hp but my MPH isn't increasing that much. Considering the old-school look at it, I'm doing 91mph (in the heat) on motor and high 97s on the spray is about 65-70hp.