N20 jetting?

**mpe331lx** · 07-25-2009, 12:24 AM

I was looking at N/X's jetting for an LT1 and they dont exactly match the jetting list posted in the sticky

Here is N/X's Jet chart:
50 = 35/20
75 = 41/24
100 = 52/31
150 = 62/35

The sticky:
NX, TNT, Zex Jet Sizes (Wet kits)
Single Nozzle (RWHP Rated)
50HP = 35N 10F
75HP = 41N 22F
100HP = 52N 28F
150HP = 62N 33F

All the n20 jets are the same, but the fuel jets are slightly smaller (except the 50, that seems way too small).

Are these jets listed in the sticky tried and true after track and dyno testing and the N/Xs jetting more of a "safe" nitrous:fuel ratio?

It looks like the fuel jets are 40-47% smaller then the nitrous jets (40-44% n/x, 46-47% in the sticky excluding the 50. The stickys 50 shot has the fuel jet bieng 70.5% smaller... That cant be right.

No one ever lists a 125.

Doing a little math, a 57/33 should be pretty close to N/Xs n20/fuel ratio.

**BLOWNDFIZ** · 07-25-2009, 08:13 AM

For sure that 50 seems wrong in the sticky. As far as how the mfg comes up with the appropriate size jets, sure there is testing done but I think some if not most are theoretical based on similar math that you used.

From personal experience I found that what NOS recommended as jet sizes did equate to the RWHP levels shown, however dyno testing with a WB showed me that their recommendations were too lean (for me). I ended up playing with fuel sizes until I get to an acceptable WB reading then use math to increase my shot size. I may not know exactly how much "HP" I'm spraying, but I can estimate based on ET increase if I really care.

**jakesz28** · 07-25-2009, 08:55 AM

Originally Posted by BLOWNDFIZ

From personal experience I found that what NOS recommended as jet sizes did equate to the RWHP levels shown, however dyno testing with a WB showed me that their recommendations were too lean (for me). .

So what AFR do you tune for?

What I have found is just about every manufacturer that I have used had a rich AFR. I have had to lean out every kit that I was serious about makiing power with. There is no set AFR to dyno tune or use as a goal for the most power. Each car will want a little something a different. Maybe one car needs a little more timing or way less fuel. It is best to go off of the plug and not a wideband.

Once you adjust the afr by reading the plugs you can then look at the wideband and use it to see if a flow problem devolopes later. On small shots in the 100-200hp range there is a large tuning window and you can get away with about any AFR.( I'm sure I will get nailed for that one ) Timing is what will hurt the motor faster then afr. But on the larger shots if your rich you will pinch the the ring lands and then start to lift the land.

My cars afr on 350 jetting is in between 12.8-13.1 and the plugs still have a bunch of color with c-16. So the color tells me I still have a way to go on leaning it out. What most of the serious nitrous tuners have noticed is what ever AFR ratio the car made the most power at N/A is what they want on the bottle. I know of one guy that has even been up in the range of 15-1 on his wideband.

**95formula383lt1** · 07-25-2009, 01:52 PM

phil, u putting some juice to the camaro sometime soon?

**BLOWNDFIZ** · 07-25-2009, 03:06 PM

Originally Posted by jakesz28

So what AFR do you tune for?

I am probably being too conservitive. And I do need to look at the plugs. I shoot for high 12's but I consistently see mid 13's on the wideband (which sounds like I'm putting too much faith in). I also pull a considerable amount of timing (5 degrees on what is probably a 100 shot at most). I think my current jetting is 46/36.

Your reply has made me feel a little better about spraying the car. So as long as I'm in the 13's and see no 14's I should be OK. Of course I am now going to pull the plugs and take a look for good measure. To get a really good true reading you have to check them right after a pass correct? Or can I get away with driving it back to the pits?

**jakesz28** · 07-25-2009, 04:33 PM

You will want to pull them at the end of the track and you will have to do it on a new plug. If you have been driving on the street it will have a bunch of color. It sounds like your doing better then most of the people tuning with a wideband. I get tired of looking at the post were someone says mid 11's for afr.

A lot of things can give a wideband a bad reading, not limited to placement in pipe, air leaks, cylinders not getting the same ratio do to intake flow, misfire in one hole. On small shots you have a large tuning window on big ones it may not be uncommon to have different cylinders needing different timing ect.