Ok, I don't know if this really works, but I meet a Infinity mechanic last night who gave theBlue and I a tip at the track.

He told us to pull of a specific vacume hose and more fuel would be delivered to the engine.

Does it work? The first run after doing this theBlue and I both got our best times of the night, so it might.

Anyways, I don't know what the correct name of the hose is, or what it really does, so I took some pics and circled it in all of them.

If anyone has more info that would be great.

http://www.rit.edu/~ejj5875/maxima/img/hose1.jpg
http://www.rit.edu/~ejj5875/maxima/img/hose2.jpg
http://www.rit.edu/~ejj5875/maxima/img/hose3.jpg
http://www.rit.edu/~ejj5875/maxima/img/hose4.jpg

I attempted to find this in my Haynes manual, but didn't have any luck.

 

I will have to try that. Thanks.
Surely you cant leave this off?

 

Don't know, I put mine back on after a few runs, and my times went back up about .1.

 

That just gives you max fuel pressure. That line gives manifold vacuum to the fuel pressure regulator. The lower the vacumm (wider throttle opening) the more fuel pressure you get. Disconnecting that line totally closes the regulator so you get maximum fuel pressure all the time. This extra fuel might give you power, it might not. You lose power from being too lean and from being too rich. You're just richening the mixture across the board, not always a good thing.

But if it helps your times, helps them consistently, then go for it.

 

first the "Poor Man's CAI" and now the "Poor Man's (APEXi)SUPER AFC!!"...well almost.....

 

Hmmm.. i think ill try that later tonight to see what happens. I wonder if i can use this to help tune the NOS. Thanks for the pics! Very clear too!

Daniel B Martin? Any ideas?

 

I dont know about using it to "tune" with NOS. This isnt the kind of thing that you'd want to leave unhooked all the time. An overly rich mixture will kill a catalytic converter pretty quickly. Your spark plugs will foul and your mileage will suck.

But, it could offer that little margin of safety when running hard on NOS at the track...until you can afford an S-AFC.

 

Okay, that's the vacumn line I figured you guys were talking about. I'll try do this mod next time at the track. I've always wondered if my Max was going lean or rich at WOT. This little mod may let me figure it out. After looking at my dyno runs, I think the VQ goes a little lean with the y-pipe and intake.

Do you guys let the line dangle or do you plug the end?


Dave

 

It's just by chance that I saw this post. I usually stick to the 4Gen forum.

Ben Garner correctly identified the hose as the vacuum signal line which controls the fuel pressure regulator. Removing this vacuum hose will boost fuel pressure from the minimum 34psi to the maximum 43psi. The hose must be plugged or else you will draw unfiltered (dirty) air into the intake manifold. This procedure is the proper method for testing the fuel pressure regulator.

In normal around-town driving I would expect the Oxygen Sensors and Engine Control Unit to reduce the fuel injector pulse width (the "on-time") to compensate for any additional fuel. With Wide Open Throttle the engine management system "throws away the rule book" and ignores those frantic "Too Rich! Too Rich!" signals from the Oxygen Sensors. However, if you put more fuel into the engine without also putting more air, you won't achieve much.

I am skeptical about this trick, but I trust numbers. If timing slips say this provides a benefit it has to be the all-time cheapest Maxima hop-up!

 

Do you think this "trick" is safe to use DBM??? Not that everyone elses opinion doesn't count, but you're the Maxima guru

 

I can't see it doing any harm if you try this for a day or two. In the long term an over-rich fuel mixture could send enough black soot into the exhaust system to coat the Oxygen Sensor tips and give you that nasty Service Engine Soon light.

 

you need that vacuum hose in order for the NOS kit to bump up your fuel pressure any more than stock WOT. if you take it off, you'll just be running at 43psi when you're on the bottle.

 

It won't richen the mixture, its just a regulator.

I will ensure highest possible pressure. It won't re-map your fuel curve, foul your plugs, put too much lead in your Catalytic Convertor, etc.

Its will just regulate max fuel pressure. This could be to your advantage under load (if you experience fuel starvation, but Its doubtful you will), but normal driving, you won't know the difference.