dry kit jet sizes question

[John_D.]

I emailed the nos guys, and asked them for jet size pairs for higher power levels for my dry NOS-5175 kit.

Their reply was: "I don't have any higher jetting combinations for that system. Thanks, NOS tech dept."

So, does anyone have some specific matching jet size pairs written down anywhere, for the nitrous and bypass jets on a dry system?

This past weekend I drilled my .047 nitrous jet out to a .056.

I believe 12secondv6 mentioned a while back, that a .063 is a 120hp shot. The original .047 is an 85hp shot. So I split the difference and went for a .055 for now, just to see what would happen.

In the absence of a smaller bypass jet, I had to crank the maft to the max 14% rich setting to compensate. (normally I run it 2% lean, so that is a 16% variation). So now I have to change the maft setting back and forth, depending on whether I plan to spray or not. Luckily I didn't go straight to the .063 sizing... Since I have maxed out the maft range already.

I would rather just have a matching bypass jet, and not have to flip the maft back and forth... (and not have to experiment with a bunch of bypass jet sizes to figure out which one to use). So if anyone has any good jet sizing info, please share. Thanks!

[ July 16, 2002: Message edited by: John_D. ]</p>

[John_D.]

(not being satisfied with the original answer, John writes back to nos and tells them he has already drilled his nitrous jet, suggests to them as a starting point that maybe I need a 34 bypass jet, and so now what...)

They write back:
"The problem is that the 56 jet is good for about 125hp. You only have six fuel injectors which might not supply enough fuel. You will need to try the 34 jet in the bypass and you will probably need to use the MAF translator to supply enough fuel. We have not done this on a six cylinder before so I do not have any details to give you."

They didn't answer about how small can I go on the bypass. I don't want to rupture the fpr...

I saw on another site where they suggest putting a .040 shim in the blue regulator that is mounted between the nos solenoids... This may be a possibility. It would also apply more pressure to the fpr, so I still have a concern about how much pressure it can take from the vacuum port side.

So, do you think the .056 is really 125hp?! I think they probably overrate the hp ratings a little... If it is 125hp, then the .063 will be killer.

Anyway, still need some jet pairs if you have 'em. Thanks!!

[ July 16, 2002: Message edited by: John_D. ]</p>

[12secondv6]

Never drill out your own jets, that could be bad.
Machines drill out the jets at nos, can you do it better w/ just your hand and a drill?
As for what rating is a 63?
I dynoed n/a and nitroused w/ a 63 jetting.
I gained 111.8 rwhp and 156.9 rwtq.
Almost 112 rwhp gain on a 120 shot.
I'm sticking with the 63 jet rated at 120 hp
They told me once that it is a 150 hp jet.
I have spoken to soooo many people who get conflicting answers from their tech dept.
Call them on the phone.
Speak to a supervisor.
See what happens then

[John_D.]

<blockquote>quote:</font><hr>Originally posted by 12secondv6:
Never drill out your own jets, that could be bad.
Machines drill out the jets at nos, can you do it better w/ just your hand and a drill?<hr></blockquote>

Probably not better, but realistically for this application of a jet, so what?

If you have information on why not to do this, I'd like to hear what it is. (I'm always asking "why" on here, aren't I...) ;)

If I was working on a fuel jet in a carb, I probably wouldn't drill my own. Size accuracy being a minor consideration. The bigger consideration being the ability to get a particular radius on the jet inlet and outlet, so the flow and pattern are very precise.

Pattern is not a consideration in this case. The nozzle (not the jet) would control that anyway, and it's so far upstream, it doesn't even matter.

So unless I'm missing something, it seems that requiring a machine to do the drilling for me is overkill. My size 54 wire drill bit worked great. Would be kinda like having a robotic welding arm to weld an aftermarket exhaust on a car... You could, and it might be a slightly better weld, but what's the point? [img]smile.gif[/img]

I just need the fuel calibrated to match the new nitrous flow... I don't care if the nitrous jet is .055, .056, or .057. I just don't want to have to switch the maft back and forth all the time...

And I'd like go on up and try a .063 at some point... :D
(which conveniently is a 1/16 drill, well ok, it's .0625 actually, but I'm not going to worry about the extra .0005 that should come out of there to make it exactly a 63 jet)

But I do need some way to get the fuel ratio up there... So, any dry jet size relationships (charts, number pairs, whatever...) would be great. Thanks!

[Nachius]

This comes directly from an owners manual!

Bypass_______N20_______Approx HP.
42___________36________70
42___________32________50
42___________34________60
42___________45________85(some say 47 for N20)
42___________63________120(12secondv6 info)

Hope People can use this info!

[ July 18, 2002: Message edited by: Nachius ]

[ July 18, 2002: Message edited by: Nachius ]</p>

[12secondv6]

What if you screw up on the drilling of the jet?
You put it in, hit the juice, run terribly lean and boom.
Why take such a chance?
Can I provide definate proof, well, I'm too lazy to look for it.
Wander around on some of the nitorus vendor sites and you will find it

[John_D.]

<blockquote>quote:</font><hr>Originally posted by 12secondv6:
What if you screw up on the drilling of the jet?
You put it in, hit the juice, run terribly lean and boom.
Why take such a chance?
Can I provide definate proof, well, I'm too lazy to look for it.
Wander around on some of the nitorus vendor sites and you will find it<hr></blockquote>

Screw up...? Put drill bit in, turn on drill, press down. Take drill bit out. Test fit - drill fits, next size up does not. Done deal.

Run lean...? Autotap and maft. Right on the mark. Testing and tuning. That's what this stuff is all about, right... That's also why I ask questions of knowledgeable people on here, hopeful they will provide some useful information to prevent problems. I don't want to tear anything up, so if someone has real information to help prevent it, great. That's definitely a concern, or I wouldn't be taking the time to do this.

Too lazy...? Sorry, I can't take "don't do it just because I say so, and no I can't support my position, but just do it because I'm the man and I say." Too many old wive's tales get started and regurgitated endlessly that way.

Wander around...? Already did that quite thoroughly. That's where I got the .034 suggestion as the counterpart to a .056 jet. Also the .040 shim in the blue regulator. Also the information on wire drill sizes that correspond to jet sizes. Also the idea that I don't need to rely on somebody else to drill a hole for me.

I do need some more corroborating information to support the .034, and some information beyond the .056 range, if anyone actually has it. I haven't found anyone yet who instills much confidence in me regarding their information on this issue.

So by asking around, maybe I won't have to go buy 20 different size jets and just try all of them. I can do the R&D if needed, but why duplicate what has already been done and tested somewhere. I learned a long time ago that I don't have the time to reinvent everything... Even though I like to and get caught up in it if I'm not careful... [img]smile.gif[/img]

We kind of got off topic... (The real question being "what jet/shim combinations go together" not "what is the optimal way to obtain a particular jet")

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Nachius:
This comes directly from an owners manual!

Bypass_______N20_______Approx HP.
42___________36________70
42___________32________50
42___________34________60
42___________45________85(some say 47 for N20)
42___________63________120(12secondv6 info)

Hope People can use this info!
<hr></blockquote>

Nachius, thanks for the info!

I have this in my manual too. Did you notice that they show 10hp per 2 jet sizes, from 50-70hp? It goes 32, 34, 36. Then all of a sudden they jump 11 sizes to a (45 in the manual, 47 in the actual kit), for the next hp step. Definitely not a linear progression. And not enough data points to determine the curve.

And the bypass jet remains constant in their table. This won't work. The bypass jet is way too big for a nitrous jet any bigger than a 47. It bleeds off too much pressure. Pressure that should be getting applied to the vacuum port of the fpr to boost the fuel pressure.

So there needs to be a list of descending bypass jets to correspond to the bigger nitrous jets. There are no data points for this jet, to establish either a linear progression or an exponential curve.

The closest thing I've found (and I don't trust it because it doesn't match the NOS chart and I need to find two charts that match -- best 2 out of 3 kind of thing) is this:

Bypass_______N20_______Approx HP.
44___________34________40
42___________37________50
42___________38________60
36___________41________70
34+__________44________80
34+__________46________90

The 34+ for the bypass represents a combination of a .034 jet, and a .040 shim added to the blue bypass regulator.

Looks like I will have to establish my own chart... If/when I do, I'll post it.

[12secondv6]

You might want to just call any nos tech line and ask them about drilling it out.
I don't have the info and I'm sorry but I know it is out there.