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      09-02-2016, 06:28 PM   #1
dre99gsx
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Fuel starvation during cornering?

Do you guys experience any starvation issues due to the single pump located on one side of the tank? Particularly, guys who road race and run supercharged setups?

Read about the E36 M3 guys installing dual pumps, one on each side of the fuel tank (obviously not possible on Z4) to alleviate this issue.

Also, does anyone know what type of fuel pump is used in Z4/Z4M, and the flow rate of the pump? I took a look at one saw a serial number with no other markings.
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      09-05-2016, 11:22 AM   #2
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No supercharger, but I haven't seen any issues so far. At Daytona on the 30 degree banks with 1/2 tank of fuel I didn't have any issues, and I've been on the Daytona infield course with the low fuel light on without an issue. I'm not pulling fuel with the stock 3.0si at the rate you'd see with a boosted engine, but at least it's a data point.
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      10-03-2016, 03:07 PM   #3
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Don't know about the "M", but the stock Z4 is equipped with a siphon in the tank to transfer fuel to fuel pump side. I've been on road courses and had no issues with less than one-quarter tank.
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      10-03-2016, 08:14 PM   #4
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Yes I'm experiencing this now at the track under half a tank. I ran my tank on fumes on two occasions at the track before this problem occurred so I have a pump on order. I will report the results as soon as it's in and I'm back to the track.
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      10-18-2016, 02:15 PM   #5
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hmm thats weird. I ran with only 1/4 tank and I didnt have fuel starvation.
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      10-19-2016, 11:47 PM   #6
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So my starvation was the fuel pump had come unclipped from the bracket in the tank and was floating around and sucking air.
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      10-20-2016, 02:27 PM   #7
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Quote:
Originally Posted by longress View Post
So my starvation was the fuel pump had come unclipped from the bracket in the tank and was floating around and sucking air.
that's the 2nd one that I've heard of like that.
Is there a better way to keep it in place?
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      10-20-2016, 08:58 PM   #8
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Hey Ian,

You probably just read about my issue twice as this is the second thread I posted this in. I'm still puzzled about how this happened. I don't think this will be a common problem as it shouldn't come un-clipped that easily. I think my situation was an anomaly.
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      10-21-2016, 09:21 AM   #9
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Quote:
Originally Posted by longress View Post
Hey Ian,

You probably just read about my issue twice as this is the second thread I posted this in. I'm still puzzled about how this happened. I don't think this will be a common problem as it shouldn't come un-clipped that easily. I think my situation was an anomaly.



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      10-19-2020, 09:32 AM   #10
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Minor update - as my power levels increased and my g-forces increased (stickier tires), this issue has been getting worse. Since I'm running quite a bit of fuel to feed the monster, anything under 3/4 tank will starve at specific corners at specific tracks, like clockwork.

I'm not a fan of installing an accumulator with secondary pump, although I fear that's my only recourse.

Anyone have additional insight on Z4 solutions to keep the fuel pump happy? It's possible the fuel feed tube from the driver side of the tank isn't connected or somehow cracked but I don't remember that being an issue.

Wish I could see a cut away of the tank to figure out solutions
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      10-19-2020, 03:20 PM   #11
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Quote:
Originally Posted by longress View Post
Hey Ian,

You probably just read about my issue twice as this is the second thread I posted this in. I'm still puzzled about how this happened. I don't think this will be a common problem as it shouldn't come un-clipped that easily. I think my situation was an anomaly.

I wonder if this might be my issue... recently after doing an airbox and a crap ton of new suspension mods (MCS 2way remotes, pretty much everything solid) I am starting to get a hick-up during extremely high G corners. Car is totally fine everywhere else except those high G corners.

I am just going to bite the bullet and replace the pump. I'll report back with how I find the old pump when I pop open the tank.
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      10-19-2020, 09:55 PM   #12
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Not ideal, but wonder if a surge tank is needed to keep up with the gs you are seeing. Radium makes a slick kit for the m3s

http://www.radiumauto.com/Fuel-Surge...esM3-P305.aspx
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      10-20-2020, 09:38 AM   #13
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Quote:
Originally Posted by Calichase View Post
Not ideal, but wonder if a surge tank is needed to keep up with the gs you are seeing. Radium makes a slick kit for the m3s

http://www.radiumauto.com/Fuel-Surge...esM3-P305.aspx
I am going to look into this.... thanks for the link!

At the very least the car could probably use a new pump/filter. I have never changed the pump and had the car since new so I am sure its getting a bit tired. The fuel filter is integrated with the pump so i am sure that needs a change too after 86K miles

I'll also do some data logging this weekend and see if I confirm it is fuel starvation.
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      10-21-2020, 01:45 AM   #14
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Quote:
Originally Posted by Calichase View Post
Not ideal, but wonder if a surge tank is needed to keep up with the gs you are seeing. Radium makes a slick kit for the m3s

http://www.radiumauto.com/Fuel-Surge...esM3-P305.aspx
Not necessary at all. I pull 1.8g at chuckwalla track with 1/4 tank and no issue at all
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      10-21-2020, 07:34 AM   #15
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My experience with my track MCoupe is that the fuel system scavenges every drop of fuel before it shows the first sign of starvation. In fact, I have run it out of fuel on two occasions. Both times I got about 3 seconds of run time after the first sign of starvation and then I was coasting. My old E36 racecar with dual pumps could be run for 10 minutes starving on fuel.

Maybe the difference is in the shape of the tank...?
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      10-21-2020, 08:38 PM   #16
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Quote:
Originally Posted by AriuSen View Post
Not necessary at all. I pull 1.8g at chuckwalla track with 1/4 tank and no issue at all
Keep in mind I'm sucking probably 3 times the fuel of a Z4M at my power level. If I part throttle around these turns I have no problem obviously.

If you're stock, then I can see this being some other issue possible... the Z4M fuel pump has a bucket that itself traps fuel but it only holds so much in there before it has to rely on the feed.

As a data point, I suck down 5.5 gal of fuel in a 20 minute lapping session which is roughly 1:30 per lap (2.25miles), or 30miles. Shit.. like 6MPG lol Turbos are very thirsty. I can see the fuel gauge drop a hair after every long pull!

Now it's quite possible that the lines connecting to the other side of the tank somehow have ruptured or cracked and thus it's not properly pulling in fuel from that end. I could look into that but not sure of the best method to test it. Also, my fuel pump assembly is only 2 years old, only a few thousand miles on it.


https://www.zpost.com/forums/showthread.php?t=844672

Guy above seems to have similar issues, with Supercharger installed

Found a diagram:

http://www.unofficialbmw.com/images/...20Part%202.pdf

page 2/3 onward. If you look at the diagram on page 27, you can see the pump sits inside a bucket. On high-g right turns, that bucket will have just enough fuel for a period of time. It's possible I eat through all of it quickly, leaving me with no return fuel to siphon up more fuel from the other side of the tank. Matter of fact, I'm running the pump at full 72psi which means there is little fuel being returned to the other tank, making the siphon even less effective.

If I part-throttle through the turn, there is a lot more fuel returning, which keeps the siphon going.

AND, I just stumbled onto this:



Go to about 4:30. It seems funny the Aeromotive guy is talking about "road racer with a saddle tank who's oem syphon jet wasn't working well enough". It's $270 for their syphon kit btw...
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      10-21-2020, 10:18 PM   #17
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You’re burning about 50% more fuel than me. No doubt that’s the issue. I wonder now if one is to burn E85 if this issue will rise up. Fuel consumption is said to increase 25-30%.
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      10-18-2021, 11:30 AM   #18
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Quote:
Originally Posted by F360C View Post
I am going to look into this.... thanks for the link!

At the very least the car could probably use a new pump/filter. I have never changed the pump and had the car since new so I am sure its getting a bit tired. The fuel filter is integrated with the pump so i am sure that needs a change too after 86K miles

I'll also do some data logging this weekend and see if I confirm it is fuel starvation.
So for awhile this issue went away but it came back this weekend at Pocono while running their mega track configuration. It was happening consistently on the two straights where I would be down shifting from 5th to 4th and then rolling back on the throttle. Both turns are high speed/high G right hand turns. After I would downshift to 4th and get back on the gas the car would sputter and sound sort of like when the traction control kicks in on my 911 Turbo or a motorsport grade TC system where it cuts spark. Before when I got this issue on high g turns it would cut power hard but this time it was like it was just misfiring. The funny part is there is some other high speed turns there but I was not getting the misfire.... it seemed to only happen after I had done a run through 3rd/4th/5th on the stirghts and then was downshifting to 4th. Fuel level didnt matter... full tank and 1/4 tank it did the same thing.

I never changed the pump/filter and I just clicked over 90K miles so that is going to be the first course of action along with getting the injectors cleaned. I'll let everyone know if I find the pump not attached correctly.
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      10-18-2021, 01:09 PM   #19
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It's not just you. I noticed similar experience on Lightning coming into T1 from high speed straight. I think the combination of heavy braking (gas goes towards front of tank) and then tight-right turn OVER a crest, all contributes to the fuel pump starving, even on a full tank. I always get a sputter when I'm on the gas after T1.

My solution is part throttle it for just 1-2 seconds after T1, then go full, and it goes away.

I have a venturi "upgrade" to try someday and see if that reduces the issue. For now at least, every single session I do on any track requires me to start with a full tank for the least amount of disruption. That reduces it.

In Pocono NORTH, the long tri-oval I'm flat out and don't get fuel starvation, which is odd in itself. I have no explanation.

I have a feeling our best solution here is to use a small fuel accumulator. I had to so something for my Meth injection because my meth pump would start from high Gs and the meth tanks sloshing the meth all to one side, starving the tank outlet.

I created a small cylinder about the size of a soda can that sits lower than the tanks. There is always meth in there. When the meth tanks start to starve, there is enough in the 'soda can' to run meth for about 10 seconds of boost. By that time, the meth from the tanks will start filling it up again with gravity.
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      10-19-2021, 08:04 AM   #20
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I’m going to opinion that y’all have a fuel system malfunction. I’m scooting around the track pretty hard (1:33’s at Road Atlanta) and have zero fuel starvation issues. As stated above, only when run to empty do I have any starvation (and then it’s game over!).

Even with the higher fuel consumption rate, you shouldn’t have starvation. I would start by replacing everything in the tank (pump/filter and regulator). Verify everything is attached properly and go from there.
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      10-19-2021, 08:14 AM   #21
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To add: my pump/filt/reg are all new-ish. Is there possibility of a clog or disconnect of the venturi on the driver side of the tank? Not sure how to check other than drain the tank and try to reach over with my arm.
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      10-19-2021, 10:43 AM   #22
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Quote:
Originally Posted by dre99gsx View Post
It's not just you. I noticed similar experience on Lightning coming into T1 from high speed straight. I think the combination of heavy braking (gas goes towards front of tank) and then tight-right turn OVER a crest, all contributes to the fuel pump starving, even on a full tank. I always get a sputter when I'm on the gas after T1.

My solution is part throttle it for just 1-2 seconds after T1, then go full, and it goes away.

I have a venturi "upgrade" to try someday and see if that reduces the issue. For now at least, every single session I do on any track requires me to start with a full tank for the least amount of disruption. That reduces it.

In Pocono NORTH, the long tri-oval I'm flat out and don't get fuel starvation, which is odd in itself. I have no explanation.

I have a feeling our best solution here is to use a small fuel accumulator. I had to so something for my Meth injection because my meth pump would start from high Gs and the meth tanks sloshing the meth all to one side, starving the tank outlet.

I created a small cylinder about the size of a soda can that sits lower than the tanks. There is always meth in there. When the meth tanks start to starve, there is enough in the 'soda can' to run meth for about 10 seconds of boost. By that time, the meth from the tanks will start filling it up again with gravity.
So the issue you describe is literally identical to mine. Heavy braking, high g right hand turn and get a sputter. Back off the throttle for a second and get back on the throttle and its fine. It only happens in specific corners but it happens at those corners consistently lap after lap.

Quote:
Originally Posted by Michael9218 View Post
Iím going to opinion that yíall have a fuel system malfunction. Iím scooting around the track pretty hard (1:33ís at Road Atlanta) and have zero fuel starvation issues. As stated above, only when run to empty do I have any starvation (and then itís game over!).

Even with the higher fuel consumption rate, you shouldnít have starvation. I would start by replacing everything in the tank (pump/filter and regulator). Verify everything is attached properly and go from there.
I think you're on to something here.... when my car was new (owned it since 2006) I never had these issues. I could run it till I literally ran out of gas with no issues. The only difference was I was not as fast as driver as i am now. That said I have run the car on Pirelli slicks that really generate the corning G's with no sputter and this weekend I was just on RE-71 street tires.

Quote:
Originally Posted by dre99gsx View Post
To add: my pump/filt/reg are all new-ish. Is there possibility of a clog or disconnect of the venturi on the driver side of the tank? Not sure how to check other than drain the tank and try to reach over with my arm.
This what throws me off thinking it is a defect in the fuel system vs a defect in the design. If you replaced everything and still have the issue then it rules it out be a defective part unless it is something in the other side of the tank we can't see. That said its not unheard of to get some defective parts off the shelf.

I think at the very least I am going to fall in your foot steps and replace everything in the fuel system and see if that cures the problem.
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