Bags

iTrader: (3)

The other day on the highway I was wondering if my vaccum canister had enough stored vaccum air to operate my Variable intake.

I know your car creates a vaccum at idle and slighty higher and the canister stores that vaccum.. but if your on the highway for long time, 45 minutes or more, and you passed a few people or whatever.. causing the stored vaccum air to be used.. would it be possible to have the canister run out?

Guess the better question to ask is how much air can the vaccum canister hold?

Do you need to have your car idle for 5 minutes before driving?

and at what point does the engine stop creating a vaccum condition?

just curious to see what others have to say on the subject..or am I just completly outta my mind?

thanks

dwapenyi

iTrader: (3)

Well, you can sit here like a techno bookworm and discuss all the theory behind vacuum and millimeters of hG stored at certain RPMs for a x period of time, etc


OR

just floor it and find out

DW

matty

iTrader: (54)

I was wondering the same thing...Im ordering it in a week

Does the car start up the same ?? What if it sits for a long time, 1-2 weeks ??

What if your on the highway jumping from 4 past 5 (where it kicks in and used vacuum) and back to 4 and you do that a few times, if your messing with a ricer, does the vacuum ever run out and have none when you go back past 5 ??

-Matt

Bags

iTrader: (3)

I did that.. That is why I am asking.. I won't say what speed, but running 3rd gear in an automatic at 6500 rpms should give you the idea.

That is why I asked.. I shifted into 4th/OD and I was only able to be there for a short time..traffic was coming up on me.. but it almost felt like it was not working...

And when you slow down below 4800 RPMS, my set RPM, the vaccum air is released and since I am still well above idle.. I was just curious

Cumalot

iTrader: (8)

Bags, have you tried having OD on to see how it pull on the highway? I don't mess with the OD button anymore, I just leave it on.

Keven97SE

Technically, yes it's possible to "run out of vacuum", but practically, it's not going to happen. Assuming you have no vacuum leaks AND you are tapping into a vacuum source that always has vacuum when the throttle is barely open, the check valve will ensure that the vacuum cannister always has vacuum. When the Harlan switches the solenoid, the vacuum from the cannister draws in the air from the MEVI actuator. The vacuum level inside the canister drops slightly due to the switch, because ambient air from the line between the solenoid and MEVI actuator has now entered the cannister. Every time the MEVI switches back and forth, the vacuum in the canister will continue to drop unless it's allowed to replenish itself during a closed (or near-closed) throttle condition.

Since all it takes is for the throttle to be nearly closed to replenish the vacuum level in the cannister, you should be okay. Even if you're on the highway hammering the gas, you are undoubtedly going to come off the gas enough to pull more vacuum. If you don't, likely you're beyond 5000 rpms and so the MEVI won't have a chance to switch back, thus you'll retain vacuum still.

The only condition I can think of where you could deplete the vacuum level in the canister is if you tap your vacuum off a SWITCHED vacuum source such as that which goes to the fuel pressure regulator. That source ONLY has vacuum at idle...the rpms have to be at idle, I believe, for the fuel regulator to get vacuum.

It's also important to keep the distance between the MEVI actuator and the solenoid to a minimum. The longer the hose between the two, the more ambient air gets sucked into the vacuum canister when the MEVI switches. That results in a larger increase in pressure (ie larger vacuum drop) every time the MEVI switches to the high rpm configuration. This is probably a neglible effect assuming the vacuum source is correct, though (vacuum source spec'd as I stated above).

In other words, I need to change my vacuum source for my MEVI. I never even really thought about it until this post.

[SIMPLIFIED VERSION]
Think of it this way: Every time the MEVI switches to the high rpm config, the vacuum cannister sucks in some air, which drops the vacuum inside it a little. You have to replenish the vacuum inside it to keep the cannister from continuing to drop it's vacuum level.
[/SIMPLIFIED VERSION]

iansw

iTrader: (7)

There is actually more vacuum created at 60mph if you take your foot off the gas than at dead stop idle anyway.

Example: I am at 15-17Hg's at idle with my SC.

On the freeway at cruising spped, when i take my foot off th gas, I'm at 20Hg.

So as long as you take your foot off the gas for even a second, your vacuum will always be replenished. This also occurs in mid-shift between gears somewhat.

IanS

matty

iTrader: (54)

Well what line are you suppose to tap into for the vacuum ??

-matt

Bags

iTrader: (3)

Man.. seriously.. your at about 130 MPH when OD is on and I am over 4800 rpms.. so no, NOT really effectively

I tried the other day at our meet and traffic was coming up on me so I had to shut it down.. I am looking at trying it soon,yeah I need to be put to sleep I am way outta control, but we will see

I promise you this with your car.. OD on may not be a big deal.. but in a non cricket car.. it helps to be off



Keven..wow.. I got lost twice in there... thank you that does help..and yes I am on the fuel pressure regulator as well.. the distance is very short on the hose length


Iansw..thank you..check your pm please

Matty..there are a few

Mr Cranman

iTrader: (1)

But I took it from the vacuum line that is right after the throttle body. Here is a picture of where I tapped for the vacuum. http://www.unm.edu/~garbear/Pictures...cs/maxpic1.jpg

If figured go to a really good source.

-John

Mishmosh

iTrader: (3)

This is really a non-issue. There is no real world condition that would trigger the solenoid off-on-off-on-... so rapidly without manifold vacuum at least being restored some in between. At high rpm, the engine has will generate higher vacuum like Ian says. And there really is no "non-switched" vacuum source in the car unless you tap your canister feed into another canister elsewhere.

As long as your canister is large enough, you have nothing to worry about. I'm not even the slightest bit concerned with this. If you want to see how many off-on's your canister can muster, just try this: idle the car for a couple of minutes, then shut the car off. Trigger the solenoid by connecting the leads to the battery. Remember the car is off so there is no vacuum source feeding the canister. Your canister should be able to open the valves quite a few times...you'll be surprised.

Bags

iTrader: (3)

Sounds like you might have given this a run????

Thanks I just might try that to see..

Mishmosh

iTrader: (3)

Ha ha... I played around a lot with the damn thing after the initial install.

Alternatively, you can just clamp the feed to the canister with a pair of locking forceps, set the rpm switch low (like 1000), and just pull the throttle while the car idles... that may make the experiment a little easier since it leaves the system completely intact.

As long as your tubing from the canister to solenoid to VI actuator is short enough or small enough (like 1/8" I.D.), most any canister should have plenty of pulls in it. ...and if you have a gonzo canister like Speedtrip's, you probably could get 50+ activations (without vacuum feed) no problem!

xHypex

iTrader: (1)

I setup my canister to tap into the FPR, and in my 220 mile journey from Austin to Dallas I triggered the VI MANY times It definitely kept working, and I drove non-stop the whole trip.
-hype

Bags

iTrader: (3)

I did a 55 mile trip twice this morning and had zero problems.

i was just curious

thanks for all the answers

Dave B

Hmmmm...I've got my VI tapped into my fuel pressure regulator too and I haven't had any problems. Keven, are you sure the regulator isn't seeing vacuum all the time?


Dave

Keven97SE

Yes. Disconnect the vac line to the FPR, turn the throttle a little to rev the engine and see for yourself. Vacuum shuts off past idle. It'd be kinda silly to always have vac on the FPR anyway...Nissan would have simply removed the vacuum line and adjusted the mechanical specs of the unit to run at a constantly lower pressure.

But after reading everyone's posts, I think the FPR vac connection is probably fine. I'm probably just being problematic here (as usual!).

xHypex

iTrader: (1)

Sometimes you're just too meticulously analytical Usually that's a very good thing, but sometimes you just worry too much
Hopefully I'll get my car back soon so I'll give you a call.
-hype

Dave B

Keven-

FYI:

When you quickly rap on the throttle, vacuum drops. That's normal. When I tested my manifold vacuum line at the "T" off the fuel regulator, vacuum at idle was at 22 Hg which is ideal. When I stabbed the throttle, vacuum dropped like an anvil. When I revved up slowly, vacuum slowly increased. All these systems checked out perfect according to the FSM in terms of vacuum. I also followed the vacuum line from the fuel regulator to the manifold and there is no "air regulating" device attached to the line. It simply plugs into the manifold. Use a flashlight and you'll see for yourself.


Dave

XXXL Cracker

iTrader: (3)

Why do you tap into the FPR? Is that how everyone is setting this up? I was checking the diagram on the website (not sure who's site it is, maybe Hypes) and did not see the FPR there. Is this just an alternate way to set it up or I am I just missing the obvious?


Also, for those of you who got there MAP/Baro from a junkyard, where do you locate this in the engine bay? I was at the salvage yard today and was unable to locate it?

Any help will be appreciated!

DL

iansw

iTrader: (7)

You can find the solenoid (actually 3 of them!) on the 1987-1990 Nissan Pulsar NX. It is physically attached to the stock air box.

Also, you can essentially mount the vacuum Tee anywhere that vacuum is coming out of the manifold. EVAp/fpr/Whatever.

IanS

Keven97SE

Well, I stand corrected. I'll just sit in the corner and shut my trap then...



Less work for me to do. Guess my hookup it fine!

...on another note, I'm sbout ready to pay Harlan a visit to take back my rpm switch or any other one he has lying around. I've emailed him three times with the question "When will I receive it back?" but when he does respond (only has twice), he goes off about what he thinks is wrong. I'm starting to get a bit perturbed. I've been waiting on this for two weeks now and I don't even have an ETA. I wish I would have shelled out the extra $40 or whatever for the MSD switch, quite frankly. It'll be December before I get my VI working at this rate. I can't say I recommend the Harlan switch after my experience.

Dave B

I use to have the same problems you had with your RPM switch and then it stopped after I played around with the fuse I hard wired into (under dash fuse box) and retorqued my ground.

For the time being, why not hardwire a toggle switch to Map/Baro? When you go WOT and the RPMs get to 4500rpms, hit the switch, and activate the VI. If you hold the rpms to redline in every gear, you'll be entering the ideal VI activation point (ie you can leave the switch "on"). My VI is set for 4700rpms and I can just about enter each gear at or close to 4700 on each shift.


Dave

iansw

iTrader: (7)

I just had a strange problem.

i was driving around, and did a quick stomp on a Honda on the freeway.

The Honda lost (of course) but not as much as usual.

So I popped the hood when I got home without turning the car off.

The RPM switch was lit up with the red LED and revving past 5k didn't open the switch.

I turned the car off, then on, and now it works fine again.

Anyone else see this before? I've had the VI since March, and I've never seen this.

IanS

RS Motorsports

iTrader: (3)

I tapped into my fpr as well and i am only getting vacuum when the car is in neutral (it won't open in any gear), i have posted this before and was wondering what could be wrong. I see that everyone that is hooking it up there isn't having any problems and I am starting to wonder if it could be my canister. I am gonna try and tap the same vacuum sorce as crannman did to see if that works. Any other suggestions would be helpfull too. also did you guys use a smaller hose for the small nipple on the canister like 1/8" cause iv noticed even when i tie it down with a 5/32" hose it is still a little loose.
Ryan

iansw

iTrader: (7)

I tapped right into where the EVAP goes into the manifold.

i also used a very small hose and put that inside a bigger hose (zip-tied tight with some sealant around it.)

It's worked perfectly since March. I think I'm going to hook a LED up to the RPM Switch and put it in my cabin on the Gauge Pod to keep a better eye on it.

IanS

Dave B

Test your canister to verify that the check valve is working. SImply remove the canister and blow into each of the nipples to verify the check valve is operating correctly and that air can pass thru only one way, etc.

Your vacuum lines CAN NOT be loose because they will leak. They must be snug. Sounds to me like you need some smaller vacuum line.


Ian-
Sounds to me like you are experiencing the Harlan RPM switch problem many of us have experienced. Mine's been fine for over 2 weeks now.


Dave