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Impressive write-up and details Nick. Thanks for sharing the journey. I'm both jealous of the mods and also inspired to think about installing the ones I have sitting in my garage (OCC, HX, grille).
 
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From my previous post in another thread:

The Q50 gas tank is one of the more oddly shaped gas tanks I've seen. See below:


96256



As you can see, it's essentially two tanks with a bridge that connects the two tanks and allows filling both sides with fuel.

The system is designed to empty the driver's side first but based on the eductor design, the fuel level on both sides is drawn down equally until then. From what I can see, there is little in the way of baffling on the bottom of either tank to minimize fuel sloshing around when the car is under hard acceleration.

So when the fuel level gets down to 1/3 of a tank, each side is roughly at half of that or 1/6 of a tank. I can see how under hard acceleration the fuel level at either the transfer tube suction or the suction on the bottom of the fuel pump assembly could momentarily drop below either suction. If the fuel flow is interrupted long enough to cause the fuel pump to starve, it could cause hesitation during hard acceleration.

I'd say a full tank is unnecessary extra weight if you're planning on WOT pulls, but 1/3 to 1/2 of a tank should be adequate to avoid fuel pump starvation and keep your weight down for better performance.
 

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Discussion Starter · #43 ·
Impressive write-up and details Nick. Thanks for sharing the journey. I'm both jealous of the mods and also inspired to think about installing the ones I have sitting in my garage (OCC, HX, grille).
Just trying to help, that's all. Thank you!
 

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Discussion Starter · #44 ·
From my previous post in another thread:

The Q50 gas tank is one of the more oddly shaped gas tanks I've seen. See below:


96256



As you can see, it's essentially two tanks with a bridge that connects the two tanks and allows filling both sides with fuel.

The system is designed to empty the driver's side first but based on the eductor design, the fuel level on both sides is drawn down equally until then. From what I can see, there is little in the way of baffling on the bottom of either tank to minimize fuel sloshing around when the car is under hard acceleration.

So when the fuel level gets down to 1/3 of a tank, each side is roughly at half of that or 1/6 of a tank. I can see how under hard acceleration the fuel level at either the transfer tube suction or the suction on the bottom of the fuel pump assembly could momentarily drop below either suction. If the fuel flow is interrupted long enough to cause the fuel pump to starve, it could cause hesitation during hard acceleration.

I'd say a full tank is unnecessary extra weight if you're planning on WOT pulls, but 1/3 to 1/2 of a tank should be adequate to avoid fuel pump starvation and keep your weight down for better performance.
Thanks. I've been looking into the design of it as well and I agree. I haven't necessarily been looking for a different fuel tank. I'm wondering if there are any track stars around the forum that deals with this issue frequently, given that we could experience it on public roads.
 

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I personally have not experienced this phenomenon yet. I have driven a few times with the fuel light on, but I'll also admit that I have not yet given my car the 'beans'. That's right, I've never put my foot to the floor in the 10 months I've had it...Call me paranoid for not wanting to break something if I drive the car too hard. Suffice it to say I've done some spirited driving, but I haven't taken it to the full extent yet.
 

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I personally have not experienced this phenomenon yet. I have driven a few times with the fuel light on, but I'll also admit that I have not yet given my car the 'beans'. That's right, I've never put my foot to the floor in the 10 months I've had it...Call me paranoid for not wanting to break something if I drive the car too hard. Suffice it to say I've done some spirited driving, but I haven't taken it to the full extent yet.
WOT ≠ engine failure. Try it, you might like it.
 
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WOT ≠ engine failure. Try it, you might like it.
I will, but like I said it's just paranoia on my part. I just need to find a good open piece of road to "experiment".
 

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Discussion Starter · #49 ·
I personally have not experienced this phenomenon yet. I have driven a few times with the fuel light on, but I'll also admit that I have not yet given my car the 'beans'. That's right, I've never put my foot to the floor in the 10 months I've had it...Call me paranoid for not wanting to break something if I drive the car too hard. Suffice it to say I've done some spirited driving, but I haven't taken it to the full extent yet.
Giving your car "beans" if your own prerogative, and no one will fault you for that. Paranoid or not, it's your vehicle, do what you're comfortable with!

But you are correct in that even with the fuel light on, if you aren't giving the car "the beans," you will most like not experience the same issue.
 

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When I was remote tuning with AMS I logged a fuel cutoff. Per AMS, “Giving it the beans” with less than 1/4 tank, especially on a tuned car with higher than stock fuel demand can result in a fuel cutoff due to the limited flow from the secondary (drivers side) tank.

I never go below 1/4 anymore…
 
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I never go below 1/4 anymore…
Agreed. I recall Seb telling me it's best to keep the fuel level at least 1/2 in the Q to prevent any fuel pick-up issues during higher-G maneuvers.
 
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Thanks. I've been looking into the design of it as well and I agree. I haven't necessarily been looking for a different fuel tank. I'm wondering if there are any track stars around the forum that deals with this issue frequently, given that we could experience it on public roads.
Z1 anti starvation kit.
 

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What's that?
A hydramat, fuel pump, and some lines. the z1 kit is marketed for G/Zs however nothing about it is actually unique to the G/Z and could be used on any saddle style fuel tank. It is a universal kit. You can also make your own very easily. the Z1 is pretty well priced though and convenient.

In a saddle style fuel tank such as ours, they utilize a venturi system that syphons fuel from the driver side saddle into the fuel basket/passenger side saddle. In normal circumstances this works pretty great, however it has 2 main inherent flaws that are exacerbated when the fuel level gets low. The venturi system can only be as efficient as the amount of fuel being returned to the basket from the pressure regulator, at WOT the amount of fuel being returned is drastically reduced, reducing the effectiveness/efficiency of the venturi system, the other issue is the venturi pickup in the driver side saddle is one singular point that under hard G forces (straight/turn/braking) the fuel sloshes away from that pickup. So at WOT with low fuel you effectively are really only able to draw from the passenger side saddle cutting your available fuel in half, if you have 1/4tank / 5 gallons you only have access to the 2.5gallons in your passenger saddle, although most likely less since that fuel will slosh as well.

To combat this installing a secondary fuel pump in the driver side saddle to feed the fuel basket/passenger side saddle will eliminate the need to rely on the venturi system that is inefficient at WOT when little fuel is being returned. To combat the fuel sloshing a hydramat is utilized which acts similar to a sponge and will absorb a large amount of fuel into it and not allow for this fuel to "slosh" giving the secondary fuel pump constant access to fuel. Even if fuel is sloshed away in the passenger side saddle away from the basket/pickup, the secondary pump will constantly have fuel and be able to send it to the passenger basket pretty much right up until its bone dry.
 

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Discussion Starter · #57 ·
A hydramat, fuel pump, and some lines. the z1 kit is marketed for G/Zs however nothing about it is actually unique to the G/Z and could be used on any saddle style fuel tank. It is a universal kit. You can also make your own very easily. the Z1 is pretty well priced though and convenient.

In a saddle style fuel tank such as ours, they utilize a venturi system that syphons fuel from the driver side saddle into the fuel basket/passenger side saddle. In normal circumstances this works pretty great, however it has 2 main inherent flaws that are exacerbated when the fuel level gets low. The venturi system can only be as efficient as the amount of fuel being returned to the basket from the pressure regulator, at WOT the amount of fuel being returned is drastically reduced, reducing the effectiveness/efficiency of the venturi system, the other issue is the venturi pickup in the driver side saddle is one singular point that under hard G forces (straight/turn/braking) the fuel sloshes away from that pickup. So at WOT with low fuel you effectively are really only able to draw from the passenger side saddle cutting your available fuel in half, if you have 1/4tank / 5 gallons you only have access to the 2.5gallons in your passenger saddle, although most likely less since that fuel will slosh as well.

To combat this installing a secondary fuel pump in the driver side saddle to feed the fuel basket/passenger side saddle will eliminate the need to rely on the venturi system that is inefficient at WOT when little fuel is being returned. To combat the fuel sloshing a hydramat is utilized which acts similar to a sponge and will absorb a large amount of fuel into it and not allow for this fuel to "slosh" giving the secondary fuel pump constant access to fuel. Even if fuel is sloshed away in the passenger side saddle away from the basket/pickup, the secondary pump will constantly have fuel and be able to send it to the passenger basket pretty much right up until its bone dry.
Huh, that's good to know. I honestly didn't know it existed. The only reason I asked was that I did a cursory search on the Z1 website, but didn't find anything. I'll dig further, thanks for the info!
 

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2018 Infiniti Q50S RWD
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Discussion Starter · #58 ·
A hydramat, fuel pump, and some lines. the z1 kit is marketed for G/Zs however nothing about it is actually unique to the G/Z and could be used on any saddle style fuel tank. It is a universal kit. You can also make your own very easily. the Z1 is pretty well priced though and convenient.

In a saddle style fuel tank such as ours, they utilize a venturi system that syphons fuel from the driver side saddle into the fuel basket/passenger side saddle. In normal circumstances this works pretty great, however it has 2 main inherent flaws that are exacerbated when the fuel level gets low. The venturi system can only be as efficient as the amount of fuel being returned to the basket from the pressure regulator, at WOT the amount of fuel being returned is drastically reduced, reducing the effectiveness/efficiency of the venturi system, the other issue is the venturi pickup in the driver side saddle is one singular point that under hard G forces (straight/turn/braking) the fuel sloshes away from that pickup. So at WOT with low fuel you effectively are really only able to draw from the passenger side saddle cutting your available fuel in half, if you have 1/4tank / 5 gallons you only have access to the 2.5gallons in your passenger saddle, although most likely less since that fuel will slosh as well.

To combat this installing a secondary fuel pump in the driver side saddle to feed the fuel basket/passenger side saddle will eliminate the need to rely on the venturi system that is inefficient at WOT when little fuel is being returned. To combat the fuel sloshing a hydramat is utilized which acts similar to a sponge and will absorb a large amount of fuel into it and not allow for this fuel to "slosh" giving the secondary fuel pump constant access to fuel. Even if fuel is sloshed away in the passenger side saddle away from the basket/pickup, the secondary pump will constantly have fuel and be able to send it to the passenger basket pretty much right up until its bone dry.
I tracked my G35 quite often and I don't recall ever having this issue of fuel starvation with it. But, now that I think of it, I don't think I would get down to less than half a tank (from full) after a whole day (not pushing a whole lot of power admittedly). I haven't looked at the fuel tank type or design for either car until just recently.
 

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A hydramat, fuel pump, and some lines. the z1 kit is marketed for G/Zs however nothing about it is actually unique to the G/Z and could be used on any saddle style fuel tank. It is a universal kit. You can also make your own very easily. the Z1 is pretty well priced though and convenient.

In a saddle style fuel tank such as ours, they utilize a venturi system that syphons fuel from the driver side saddle into the fuel basket/passenger side saddle. In normal circumstances this works pretty great, however it has 2 main inherent flaws that are exacerbated when the fuel level gets low. The venturi system can only be as efficient as the amount of fuel being returned to the basket from the pressure regulator, at WOT the amount of fuel being returned is drastically reduced, reducing the effectiveness/efficiency of the venturi system, the other issue is the venturi pickup in the driver side saddle is one singular point that under hard G forces (straight/turn/braking) the fuel sloshes away from that pickup. So at WOT with low fuel you effectively are really only able to draw from the passenger side saddle cutting your available fuel in half, if you have 1/4tank / 5 gallons you only have access to the 2.5gallons in your passenger saddle, although most likely less since that fuel will slosh as well.

To combat this installing a secondary fuel pump in the driver side saddle to feed the fuel basket/passenger side saddle will eliminate the need to rely on the venturi system that is inefficient at WOT when little fuel is being returned. To combat the fuel sloshing a hydramat is utilized which acts similar to a sponge and will absorb a large amount of fuel into it and not allow for this fuel to "slosh" giving the secondary fuel pump constant access to fuel. Even if fuel is sloshed away in the passenger side saddle away from the basket/pickup, the secondary pump will constantly have fuel and be able to send it to the passenger basket pretty much right up until its bone dry.
This is the first time I see this solution for our cars. Seems straight forward and simple after reading Z1 instructions. Good catch, I like people who take informed and thought out risks. Have you called them to let them know it worked on a Q50? Maybe if they advertirse it as a solution for Q50's more people will buy it.
 
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Link?
 
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