TonyJ

I need some opinions...

What do you think about fattening up the fuel jet on a wet setup?

Let's say that my a/f is 12.6, a little leaner than I'd like. If the NX chart recommends 52/28 jets, would it be safe to go to 52/31 to fatten the fuel?

Thoughts?

NXJeremy

Yes you can do that to fatten up the nitrous system, you're on the right track. I personally like using dedicated fuel systems for the nitrous systems so that all changes to the system don't affect the car's NA performance.

Wile_E

I went with a larger jet for fuel because the recommended jets had me too lean. I'm a little rich up top but the fuel curve starts off lean and gets richer as the rpms go up.

Is your like that or is it flat?

Here's the jets I used and here is what my A/F looked like.
Run 2 ---- NA
Run 5 ---- 41 nitrous / 28 fuel
Run 6 ---- 52 nitrous / 35 fuel

Is there any way to flatten out the curve?

TonyJ

Wile_E

Why didn't you switch jets while on the dyno? That would've fattened it up some. I figure everyone's setup is different so the jet sizes might vary a little on each setup.

A little bigger fuel jet should work out for you just fine.

TonyJ

I was dynoing at an organized dyno day that gave us 3 runs for $50. No time for tuning, though. I didn't get the idea for fattening the fuel until last night. I hadn't heard of it before. I was just looking for a solution short of pulling timing...

TonyJ

Anyone else have thoughts on this? Ricky or Dave?

Nitro Dave's Nitrous Outlet

iTrader: (25)

Tony,
What is the airfuel on motor?
Also looking at this graph they were spraying starting at 1600 RPM.That asking to blow it up. Do you have a window switch on the car? They should have not started pulling that car untill around 3,000.Pulling it from such a low RPM like that can cause the car to bog and then BOOM nitrous backfire.
Dave

860 Performance

iTrader: (1)

It looks to me like your NA air/fuel is way off. Your up around 15:1 until you hit the N20. Then it drops down, not quite enough, but it does go down.
Do you have a graph of just the motor without nitrous? If so post it.
Basicly, make sure the motor is tuned right before changing jets.

Wile_E

It looks like he started spraying at 3000 on the graph. That's where the power shot up and the A/F ratio started a steady downward curve.

TonyJ

The shot was between 3000 & 5600 with an MSD Digital RPM window switch. Here's a baseline from a couple of months ago an the new run compared...

Wile_E

I think he wanted to see the A/F on the baseline run.

Nitro Dave's Nitrous Outlet

iTrader: (25)

Yes we need to see airfuel on the base line.There is one of two things happening.
First.The car is running lean on NA.If this is happening you need to get the car tuned before trying to adjust the airfuel on nitrous.

Second.Since the car was starting to be loged in 4th gear(six speed) or drive(Auto) The car was lugging to start with and the graph may not be accurate.

I think the first one is probley the reason.
Dave

TonyJ

This is the best I've got from the first dyno...

TonyJ

? any thoughts?

Nitro Dave's Nitrous Outlet

iTrader: (25)

Why are they pulling that car like that.I don not understand why they are pulling the car ?

First of all the car has to be in fourth gear and they are pulling it from 1200 rpms.The car is struggling.That graph will not be accurate.Either take it somewhere else or explain to them that they need to pull this car from about 3000 rpms.
We need a accurate pull before we can go any further.If you do a good pull and the air fuel graph still looks that bad you need to get someone to tune the car.I would do this before spraying.
Dave