Vacuum?

[RaVeN1469]

To vacuum or not to vacuum, that is the question. I have been told to just say screw the vacuum because it isn't needed. In theory the MAF should be more than capable of handling everything. Is there any benefit to hooking up the vacuum safety wise? For those of you that do have the vacuum lines hooked up where did you tap them? If no one has any suggestions I'm just going to randomly tap another line and hope I don't screw something up. I was thinking about the larger line that runs into something next to the fuel rail that has my FPSS on it then it runs to the intake. Does it really matter where I hook this up to?

[RaVeN1469]

Is this just a stupid question? I would really like to know how I'm supposed to hook up the vacuum. I'm just about done with the install and would like to have it done right. If I don't get advice from here guess I'll just take a shot in the dark. How does everyone here have theirs hooked up?

[anthony gorman]

ive never heard of a non vacuum set up. mines screwed up too. i think its the nitrous regulator.

[John_D.]

What is it, that goes to the vacuum on a 5176?

On the 5175, there's a line that goes to the vacuum line that goes to the fuel pressure regulator (fpr). It kicks the fuel pressure up, from 45psi or so, up to around 55-60 psi. This gives you a little extra through the injectors, in addition to what the maf sensor is telling the pcm to provide.

There is not really a whole lot more actual cfm flowing through the maf. Just a gas that has more oxygen in it. The maf sensor doesn't know this. It is affected by the colder air charge (as a result of the cooling effect of the nitrous), which then cools the maf sensor wire more, making it look like more air is flowing.

What size shot?

In addition to the maf sensor effect, and the increased fuel pressure, I also had to max out my MAFT to tell the pcm there was even more air flowing than the maf sensor reported. 14% rich setting. When I went with a 100 shot.

I tied into the vacuum line coming off the passenger side of the intake, from a black plastic plate. The line went to the fpr. I spliced into the existing line.

The nitrous applies pressure to the fpr (which normally sees only vacuum).

[12secondv6]

Yup, he said it.
Same place I had mine spliced in for vaccum.
Don't juice a dry shot w/o it cause that would be bad.
You would potentially cause damage to the engine.
Now wet is obviously different cause it has a fuel solenoid spraying in fuel.

[RaVeN1469]

Actually I don't think it's really a 5176. I have no idea what kit it really is but the instructions they sent me are for a 5115 which is the mustang 5.0 kit. But those could just be instructions they had laying around, it came from some performance shop in texas. But the kit has that blue nitrous regulator inbetween the solenoids which has a vacuum line that goes to a Tee. Down off the Tee is a blue nut where you place the jet (59 is what came with it for nitrous and what I plan on for the bypass, unless otherwise suggested) and the instructions say run this to an "existing vacuum". The other one goes straight and the instructions say hook it to the fpr. Well I can barely see my fpr and don't think there is anywhere to directly hook a line, so I'm assuming you tap into the line that hooks to it.

I'm running a 42 nitrous jet which is supposedly about a 85 shot. Would it be a good idea to run rich on this kind of a shot? If so how would I go about doing that? I probably won't be spraying a whole lot because I'll be in college but anything that will add safety is worth it.

[John_D.]

That blue regulator is so you don't send 900 psi down the line to your fpr. The fpr should only be seeing a few pounds on the vacuum line. (normally the fpr only sees vacuum, which drops to nearly 0 psi at wot). While spraying, it actually swings from vacuum, to zero, and over to a pressurized setting.

The bypass jet is so the pressure can bleed off the line when you're done, and to help manage the pressure while you're spraying.

This is from the 5175 kit directions:

Bypass_______N20_______Approx HP.
42___________32________50
42___________34________60
42___________36________70
42___________45________85

So the 42 belongs in the tee to the fpr.

The kits actually come with a 47, not a 45 jet, for the 85 hp shot.

The 59 would have to be the n2o jet, and it is huge for a dry shot. It will be well over a 100 shot.

The 42 bypass will be too large for this nitrous jet. (bleeding off too much pressure off the fpr). I am running a 57 nitrous jet, and I had to max out my maft on the rich side, to keep from running lean with the 42 bypass.

NOS suggested a 34 bypass jet might help, so I may try that later. (there were some posts about all this in a thread called "dry jet sizes" in this forum.)

A smaller bypass jet will hold more pressure against the fpr, which in turn will give you more fuel pressure (and more fuel), up to a point.

If you run a 59 nitrous jet, you will need to do something. MAFT, boost-a-pump, adjustable fpr, programming, something... To get the fuel delivery to match the nitrous flow.

You'll need a way to monitor the a/f ratio to tune it correctly. Autotap, or an a/f or egt gauge.

As far as running rich, you need to run rich no matter what shot. Rich as in "not 14.7:1", more like 12:1.

Richer than that won't help and will take away power.

12.3 - 12.5 is probably optimal. Much leaner than that, and you are courting disaster (a meltdown somewhere, and/or detonation).

There are some sites that show the hp power curve for the lean/rich settings. And also that approximate the o2 sensor voltages for those a/f ratios.

Everyone pretty much shoots for about a .90-.92 o2 sensor voltage at wot while spraying.

[RaVeN1469]

All right, I'm starting to understand all of this. But one thing that is just beyond me, is what happens to the line off the bypass jet? If you just leave it to atmosphere won't you loose your vacuum in your lines when your running normal (no nitrous)?

So it looks like the jet I have is going into the bypass and I'll be finding another one, probably a 45, for the nitrous. I won't be running anything larger than about an 85hp or occasional 100hp shot (maybe) because I can't afford upgrading the fuel system, that and I don't have anywhere near enough mods to be running even a 85hp but oh well.

(only reason I mention a 59 jet is because thats what was in the kit when I got it)

I have an autometer a/f gauge already installed. Is there a thread about tuning and setting my car to run rich? How will I know the volts when I spray? 0.0=first red led --- 1.0=last green led? I'm running stock 02 sensors also, is this sufficient?


Sorry about all the questions but I want to make sure everything is done exactly right, I'm dealing with my pride and joy.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by RaVeN1469:
All right, I'm starting to understand all of this. But one thing that is just beyond me, is what happens to the line off the bypass jet? If you just leave it to atmosphere won't you loose your vacuum in your lines when your running normal (no nitrous)?

I have an autometer a/f gauge already installed. Is there a thread about tuning and setting my car to run rich? How will I know the volts when I spray? 0.0=first red led --- 1.0=last green led? I'm running stock 02 sensors also, is this sufficient?<hr></blockquote>

Good questions. Ok, about the vacuum line. You need to splice into the existing line. It goes from the intake to the fpr. When you're not spraying, your added line doesn't do anything extra, and the vacuum still runs the fpr as usual. When you do spray, some of your nitrous will go through the line, and hit the fpr. Nothing should be open to the atmosphere with this arrangement.

FPR
|
|
|
|----jet----------Intake
|
|
|
Blue regulator

Your new parts in this diagram are the lower left parts. The blue regulator, the line, the tee, and the jet. The existing parts are the line from the intake to the fpr, and the fpr.

Tuning...

The stock o2 sensors are ok. A wideband sensor would be more accurate, but the stock ones are ok for basic tuning.

I don't know about using an led gauge. It will be harder to evaluate. You'll probably need some documentation for the gauge. Depends on if it registers at a fine or coarse level on the high end of the scale. A cruise gauge may be finer in the middle and coarse on the ends. A wot gauge is finer on the high end.

The basic factory jetting with the 5175 kit is supposed to be ok without making other fuel system mods. Your gauge will probably be good enough to tell you if you're running too lean, or if you are ok.

I had to spray as far upstream from the maf sensor as possible. When I sprayed close, I got very erratic maf readings, which caused the a/f ratio to go all over the place.

Hope this helps. Let me know if you have other questions...

[RaVeN1469]

So for the line off the jet I place a tee in the line coming off the passenger side of the intake and for the other one I place a tee close to the fpr?

I think your right about the a/f gauge, it must be coarse at wot because I loose readings at a certain point but it seams real accurate at stoich. I have the nozzle placed in the base of my lid, right in front of where the silencer would be and right behind the ait sensor. It was already predrilled when I got it because I bought it used :D .

Now considering I spray and determine that I'm running lean, then what do I do? How do I make sure I'm running at 12.3-12.5? or what ever I'm going to run at.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by RaVeN1469:
So for the line off the jet I place a tee in the line coming off the passenger side of the intake and for the other one I place a tee close to the fpr?

Now considering I spray and determine that I'm running lean, then what do I do? How do I make sure I'm running at 12.3-12.5? or what ever I'm going to run at.<hr></blockquote>

Just one tee is needed. The end with the jet goes toward the intake. One end goes to the fpr. One end goes to the blue regulator.

If you're running lean, you have to get more fuel through the injectors.
-- Lie to the pcm (maft) saying there is more air, and then the pcm will hold the injector open longer
-- Kick the fuel pressure even higher (boost-a-pump, adjustable fpr, smaller bypass jet), and then more fuel will come out during the same injector pulse time
-- Bigger injectors (creates some idle and part-throttle issues...)
-- PCM reprogramming (good luck...)

To monitor, you will probably need something like autotap or obd2, or a voltage gauge, or a wot a/f gauge.

edit - added - You may be able to get more fuel by putting the nitrous upstream of the iat sensor. Colder air being denser, the pcm may adjust even more. Or it may go the other way, realizing you have cold air, and accounting for this by deducting for the additional cooling effect over the maf sensor wires... Not sure about this part of the equation.

Maybe 12secondV6, magnus, dom, or one of the other guys know if a colder iat reading (based on actual colder air, not on an iat resistor mod...) will give you more fuel, less fuel, or neither.

[ July 31, 2002: Message edited by: John_D. ]</p>

[Nachius]

edit - added - You may be able to get more fuel by putting the nitrous upstream of the iat sensor. Colder air being denser, the pcm may adjust even more. Or it may go the other way, realizing you have cold air, and accounting for this by deducting for the additional cooling effect over the maf sensor wires... Not sure about this part of the equation.

Maybe 12secondV6, magnus, dom, or one of the other guys know if a colder iat reading (based on actual colder air, not on an iat resistor mod...) will give you more fuel, less fuel, or neither.

[ July 31, 2002: Message edited by: John_D. ][/QB][/QUOTE]

Thats just what I was getting ready to ask I did a search and found this after reading througha few posts. Basically I'm gettin ready to install my Nitrous Kit (Dry) and was wondering about nozzle placement as far as would it hurt anything putting it before the IAT sensor and spraying there or would it just be better to put it after the IAT sensor?

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Nachius:
Basically I'm gettin ready to install my Nitrous Kit (Dry) and was wondering about nozzle placement as far as would it hurt anything putting it before the IAT sensor and spraying there or would it just be better to put it after the IAT sensor?<hr></blockquote>

I moved mine to the passenger side of the air box. I used to have it in the silencer, pointed toward the throttle body, and it didn't work very well there at all...

Since my IAT is in the tubing up close to the air box, mounting the nozzle anywhere in the air box places it before the sensor. I figured putting it in the opposite side would allow the nitrous and air to mix as much as possible before hitting the iat, and to mix even more before getting to the maf sensor.

I think it softens the initial hit, the further away it is. But this has an advantage, of not getting me into a bunch of suspension mods trying to handle too much extra torque right off the line... Once it comes in, it's just as strong as any other arrangement.

If I remember right, when I was trying to work out my placement, 12secondV6 had recently come across some information that also said the further upstream, the better.

[RaVeN1469]

Ok, well I guess your going to have to spell it out for me. Exactly where and how do each vacuum line attach? I know one goes to the vacuum line by the intake and I'll use a Tee. But how does the other one hook up? There is only one spot on my FPR for a line and theres currently a line on it. Do I disconnect this line? I must be missunderstanding you, that or I'm an idiot. Thanks for all the help

[John_D.]

Ok, here's a before and after, maybe this will help clear it up. The back of the engine is on the left of the diagram, and the front of the engine is on the right side of the diagram.


BEFORE:
(one solid line to the fpr)

FPR
|
|
|
|-----------------Intake

AFTER:
(A line from the blue regulator to the fpr. With a tee in it. The bottom of the tee attaches to line from the intake.)

FPR
|
|
|
|----jet----------Intake
|
|
|
Blue regulator


With the new arrangement, when not spraying, vacuum from the intake still goes to the fpr, just like before. (it will actually suck on the blue regulator too, but it doesn't care, it just ignores it...) Then when you spray, the blue regulator opens, nitrous pressure goes shooting over to the fpr, with some of the nitrous bleeding off into the intake.