FiTech Go EFI question

[Topless69GT 28]

So my FiTech Go EFI arrived today. Well at least the fuel command center did. Still waiting on the actual EFI unit. My question relates to the vent line from the fuel command center back to the tank. It states the fuel tank needs to be vented and a vent return line needs to be installed back to the tank. What have you seen done to run a return line back to a stock style tank. Also is the stock tank considered vented? I can't imagine that pressure would build up in the stock style tank. I would think the stock style pop open gas cap would not seal that well and pressure build up would not be an issue.

[larryc94 38]

It's a must to run a vent line, I used 1/4" nylon fuel line with these clips  http://www.quickclips.org/purchase/ tied into the filler neck.  I have seen fuel spit out of the vent line after about 10 mins after shut down.  The gas we have with the ethanol is horrible, it boils so easy.  It's the reason carbs don't work as well when we had leaded gas like when our cars were new.

 

Our gas caps are vented, the filler neck surface where the gas cap seats has an indent at about 11 o'clock so the cap doesn't seal completely

 

Also FiTech recommends to reduce  the Fuel pump control  PWM low flow to 38% to slow fuel pump at idle to prevent heating the fuel.

 

Larry

[ray1970 88]

At the risk of over or under thinking the vent hose thing I ran mine out the front of the car the same as the radiator over flow..

WHY?

The command center is just a big float bowl.

I work in motorsports and all but California bikes vent out short tubes that end up over the motor.

STD car carburetor's have no vent line at all.(This can be a problem at times)

Im not lazy but if I don't see a need for something I will get on to something my car really needs.

 

2000+ miles with the fitech and never a problem with the CC..

The throttle body stuff I will NOT get into..

[larryc94 38]

It's not a question of over or under thinking, it should be vented back to the tank.  Them calling it a vent is a poor choice of words.

 

This has been discussed on different forums,where it's been reported that guys have attached a catch can and gone for a ride and collected a cup of fuel.

 

The needle and seat in the CC is the Holley adjustable type.  What happen when dirt or what ever reason they stick happens.  Well in your case you'll have fuel pouring on the ground under your car, you won't know till you smell it or some one points it out to you.  With a carb it usually starts dumping out the vent and down the venturi and the engine stalls.

 

Like  I said I've seen fuel spit out the vent after the car sat for 10 mins or so popping the gas cap and peering in where the vent enters the filler neck.

 

FiTech is giving you the warning about the "vent line" to protect you and themselves.  If you have a mishap and your car burns your insurance may not cover you losses because you installed it improperly according to the manufactures instruction and warning

 

Larry

[ray1970 88]

Its still just a vent and if fuel flows out of it there is a problem. would like to know about it and

Fix it..

Never seen mine leak.

In 40 years I have had more carb leaks than I can count...Been on fire 3 times.

Yes I carry a fire extinguisher.. (now)

 

Im not saying do what I do just telling you what I did..I'm OK with it..

The fitech vent thing is only a warning..Im over 18 by a long ways.

[Topless69GT 28]

Ray1970 I am going to route it the way you did. If I have issues I can always run it back to the tank later.

[larryc94 38]

Just make sure you have fire insurance.  

[Vicfreg 771]

I know this is an old post but I am getting ready to install the FiTech system with the command center.  I was wondering about the vent as well, and wanted to know how you all made out with it.

[larryc94 38]

On 5/13/2016 at 7:27 AM, larryc94 said:

It's not a question of over or under thinking, it should be vented back to the tank.  Them calling it a vent is a poor choice of words.

 

This has been discussed on different forums,where it's been reported that guys have attached a catch can and gone for a ride and collected a cup of fuel.

 

The needle and seat in the CC is the Holley adjustable type.  What happen when dirt or what ever reason they stick happens.  Well in your case you'll have fuel pouring on the ground under your car, you won't know till you smell it or some one points it out to you.  With a carb it usually starts dumping out the vent and down the venturi and the engine stalls.

 

Like  I said I've seen fuel spit out the vent after the car sat for 10 mins or so popping the gas cap and peering in where the vent enters the filler neck.

 

FiTech is giving you the warning about the "vent line" to protect you and themselves.  If you have a mishap and your car burns your insurance may not cover you losses because you installed it improperly according to the manufactures instruction and warning

 

Larry

 

On 5/13/2016 at 8:51 PM, larryc94 said:

Just make sure you have fire insurance.  

I stand by what I posted

[Shep69 149]

 

Im not using the command center with my FiTech  but if you go on the FiTech owners group face book page im sure theres a mod that the guys are doing to avoid problems. There are known issues with it. I think that it overheats or something . A lot of people are removing them for in tank pumps. 

Im happy with my FiTech  . The only mod that im considering is milling the duel plane manifold divide wall down as they say that this makes them run better. I can't put a spacer in due to the shaker hood clearance. 

[Kevin427 18]

How about a charcoal canister mounted under the fender?

[larryc94 38]

It has to go back to the tank unrestricted

[Vicfreg 771]

Shep, thanks for the info.   I have the command center and I am going to give it a try.  Ran into a couple folks over the summer at car shows that were using it, that is what got me interested.   I have heard some thing about overheating, will keep an eye on that.   I have a dual plane Edelbrock Performer RPM manifold installed.  I am not anxious to remove it and modify it.   I also will be running a Shaker hood, so will have the same problem with a spacer.    I think that for the RPM band my engine will operate in, the dual plane is still the correct choice.  I used to run a single plane (torker) years ago on a small block ford, and I had to really wind it out to get it to run right.  It also was not happy in the cold weather.

I will be putting my engine in within the next 30 days, so hopefully by March, I will be running the engine with the EFI system all in.

 

[larryc94 38]

I have a RPM airgap on 351c with a command center for 2 years, I've been in parades , stuck in traffic in 90* temps and never had a problem.  The command center is not modified.  The dual plane runs fine and with a 3.70 rear and 5 sp it's always in the power band and just pulls.  I also have the dreaded 4v cc heads, if you run the correct cam it has ton's of low end

[Shep69 149]

2 hours ago, larryc94 said:

I have a RPM airgap on 351c with a command center for 2 years, I've been in parades , stuck in traffic in 90* temps and never had a problem.  The command center is not modified.  The dual plane runs fine and with a 3.70 rear and 5 sp it's always in the power band and just pulls.  I also have the dreaded 4v cc heads, if you run the correct cam it has ton's of low end

Good to hear your not having issues Larry. I don't know how you got the air gap under the hood with a shaker . I had to use a big block base and mod it to get my shaker to fit under on my 351w performer rpm intake. Does your RPM air gap have the divide wall milled out slightly? they say that this helps . I think the new ones are all milled out now.

[larryc94 38]

The airgap comes with a  notch in the divider and I think the 351w sits taller than a 351c.  The shaker fits but I would like it 1/2" lower, I could rework the base

[Vicfreg 771]

Hi Larry, thanks a lot for your insights.  I have a couple questions about the FiTech install.  The first one is easy, which is where did you put your O2 sensor?   I am using shorty headers and am thinking I can put it in a transition pipe downstream of the collector.  The second question is about the darn vent.   I have seen endless opinions about if/where/how to run the FCC vent line.  I plan to do that, and was thinking I would run a line parallel to my fuel supply line, back to the tank, and install a threaded bung on my fuel filler neck to run it to.  What was your approach for this?

 

[Vicfreg 771]

Shep, I am running a Windsor based stroker with the same intake as you.   I am also going to use a shaker hood.  Any details on what exact parts you had to use and/or modify, and pictures would be greatly appreciated.  I was even considering using adjustable motor mounts in an attempt to address this issue, so if you are using stock motor mounts and have your shaker lined up, would love to hear the insights on that.

[larryc94 38]

4 minutes ago, Vicfreg said:

Hi Larry, thanks a lot for your insights.  I have a couple questions about the FiTech install.  The first one is easy, which is where did you put your O2 sensor?   I am using shorty headers and am thinking I can put it in a transition pipe downstream of the collector.  The second question is about the darn vent.   I have seen endless opinions about if/where/how to run the FCC vent line.  I plan to do that, and was thinking I would run a line parallel to my fuel supply line, back to the tank, and install a threaded bung on my fuel filler neck to run it to.  What was your approach for this?

 

 

I have the O2 right after the bend where the H pipe is horizontal.  The vent line I ran is  1/4 nylon fuel line with these clips http://www.quickclips.org/home/ and used a 1/8npt x1/4 barbed fitting screwed into the filler neck

[Vicfreg 771]

Larry thanks for the info. So did you just drill a hole into the filler neck and just tap it and screw the fitting in?   Also,  if the line is clear do you ever see any gas in it?  I was wondering if running it under the car would cause like a P-trap and keep it from venting    

[larryc94 38]

Drilled and tapped the hole.

Line is black but did check it one time after car was shut for 10 min and popped gas cap and see fuel spitting  out into the filler neck

The "P" trap thing was perpetrated elsewhere and yes fuel will be in the line, but you have pressure or vacuum acting on it.

In your house the P trap doesn't impede flow because of the pressure pushing it, same here but you can have vacuum too.

The CC vent is not an atmospheric vent.  If it was then the P trap scenario would affect it

The problem somebody had was they tried to repurpose a vent line back to the tank that had a built in restrictor.  And every time he got stuck he blow the line through pushing fuel pass the restrictor, and it worked till the line filled again.

Some of the GM cars do have a line you can use but you have check it for restriction.  If you can blow thru it free it's good to use, if not you'll end up with the problems he had

One thing he posted his problems on many forums so hence the wide spread problem

[Vicfreg 771]

Hey Larry, you and I are on the same page here about the P trap.  I am moving forward with it.  Just for fun, I put together a simple comparison to show how little pressure is actually required to clear the loop seal.   I went down to the shop, and took some rough measurements on my car.  Where I am going to locate my FCC, at the highest point (top of the fender) it is about 24" from where the bottom of the "loop" would be.  Then I measured from the centerline of my gas cap hole in the rear, to the same place on the vent line low point, and it was about 12".    So, I put together 2 diagrams which show  the pressure required to clear the loop seal.   I am sure this will spur some dialogue, but also clear things up on the vent line.  In my opinion, not running it would be unsafe.

 

Visio-Loop Seal.vsd.pdf

Visio-Loop Seala.vsd.pdf

[Vicfreg 771]

Oh, here are picture versions of these:

 

[Vicfreg 771]

Additional explanations about assumptions:

1. Water specific gravity is 1.0.  Gasoline is 0.74.   The exact dimension of water height that is equivalent to 12" of gas is actually 9", not 8", but I was trying to make the example realistic based on the measurement of my fast food cup.   :)
2. The assumption about the P trap equalizing due to the manometer effect may not be true at all times, depending on the internal pressure of the FCC.  However, if the FCC is at or above atmospheric pressure, the loop seal will clear at any pressure above 0.32 psi.
3. I make no certifications on my "calculations", but do attest to completing the practical experiment with the straw.....

[larryc94 38]

Those are some calculations, I know it  just works.  BTW what happens when the gas is in a vapor state!

 

I know the fuel in the CC has had to been boiling at some point.  It get hot under hood, no a/c and can feel the heat inside cabin but has never affected anything