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      10-19-2021, 01:31 PM   #23
Vanne
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love that radium kit
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      10-20-2021, 07:16 PM   #24
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love that radium kit
LOL, have you tested this kit on track yet?
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      10-21-2021, 11:07 PM   #25
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Not yet, but I have an option to buy it very cheaply..
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      11-07-2021, 06:59 PM   #26
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So, unfortunately, I'm gonna have to eat my words here a bit...

This last weekend at Barber Motorsports Park, I had a fuel starvation episode. (y'all jinxed me!)

I was definitely a bit low on fuel on the last couple laps of a 30 minute session (though not the lowest of the weekend...but, the previous day the track was cold and wet). My AiM was reading 4 gallons when it happened. The first time it cut power for about 2 seconds and I got a warning from the AiM that I had low fuel pressure (I installed an AiM pressure sensor on the fuel line). The next lap it cut for about 3 seconds. I had 3.8 gallons when I pitted in on that last lap.

The situation where it happened was after a prolonged high G right turn complex that starts with a carrousel pulling 1.3 - 1.55 G's with part throttle that lasts for 7 seconds followed be a hard charge at full throttle up a hill while still pulling close to 1 G that also lasts for 7 seconds. At the top of the hill it cut out. Fortunately over the hill is a hard downhill braking zone and both times the motor came back to life before turn entry at the end of the braking zone.

While this has not happened before, I was turning consistently faster laps than before with a PR improvement of 1.2 seconds (1:35.7 while being chased by a GT4 Clubsport. He didn't catch me). Perhaps the increase in lateral G's and the low fuel in this session was just enough to cause the starvation.

My assumption on the situation would be that the carrousel pushed the fuel to the left side of the tank leaving little in the baffle chamber, but part throttle allowed the siphon valve to keep up with demand. Once I was hard on the gas for 7 seconds while still pulling G's the siphon couldn't keep up.

The next session out, more fuel solved the problem.
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      11-08-2021, 07:26 AM   #27
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Interesting... On occasion now I noticed you are at NJMP when I'm at Pocono. We need to run into each other at the track someday being that we're in the same state...

Anyway, yes, anytime I am cresting a hill during or before a prolonged high-G turn, I get fuel cut. You'll find me topping off the car with gas before every session - it helps minimize it. I do go through a half tank for every 20min session. Annoying to keep refilling but that's the game.

There aren't many people here pushing their Z4s to the limits with "stock" tank/pump configs like us that can speak to this. Once you start pulling high G's, it seems we're on our own.

The good thing is for me, it happens on queue in specific parts of the track. I can actually predict it, time it, and sometimes apply 70% throttle for 1-2 second on corner exit (instead of 100%) and issue is resolved.

We're just reaching the limits of the OEM system in imho.
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      12-07-2021, 09:46 AM   #28
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So I ran the car last weekend at Road Atlanta and went as low as 2.5 gallons with no fuel starvation issues. To me this verifies that my fuel system is functioning as designed and that the episode at Barber was due to unique circumstances.

If you're having fuel starvation at high fuel levels, something is malfunctioning. Or in the case of your turbo 2JZ, you've just exceeded the systems capabilities.
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      12-07-2021, 09:57 AM   #29
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Not sure I understand. Your Barber post points to starvation the way you phrased it, and you now toss it up to " unique circumstances". Is it or isn't it starvation? Remember every track is different.

Go back to Barber to 2.5gal and see if you experience the same thing? That would probably confirm any suspicion.
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      12-19-2021, 06:39 AM   #30
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Andre,

Have you looked into whether there exists a fuel accumulator that could be plumbed into our system?

I found this, but not sure it is compatible with our cars.

https://store.034motorsport.com/full...fuel-pump.html

And this, but it doesn’t appear to be available.

https://watermanracing.com/product/o...y-accumulator/

It would seem to me that there should be a device that functions like an oil accumulator. I’m just not finding it.
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      12-19-2021, 08:51 AM   #31
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Those are cool units. A few other companies make similar items. Unfortunately I would have to plumb a return line and hack up the entire OEM fuel system on the Z4. I have this under consideration but first thing I have on the docket is to replace the oem venturi system with an upgraded unit and test. It's possible the OEM unit is clogged and/or to small as was suggested by Radium

http://www.radiumauto.com/Venturi-Je...-Kit-P760.aspx
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      12-19-2021, 03:40 PM   #32
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Aftermarket siphon may be worth a shot, but in post #4 someone tried one to no avail.

https://www.bimmerforums.com/forum/s...iphon-Pump-Kit
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      10-17-2022, 05:00 PM   #33
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anyone have a reasonable budget solution or found if a new fuel pump solved the issue? I'm a recent owner and took my mcoupe yesterday at buttonwillow raceway and did get some hesitation on some corners at half tank. Looking to see if anyone has found some solution or if a new fuel pump helped before I fork out money for a new one.
Thanks!
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      10-17-2022, 06:57 PM   #34
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Budget solution is to run a full tank every session...
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      10-19-2022, 12:29 PM   #35
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I could and did , but it's weight penalty when trying to PB, haha!
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      10-27-2022, 01:40 PM   #36
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Quote:
Originally Posted by dre99gsx View Post
Budget solution is to run a full tank every session...
I think there has to be something at play here were all missing. I have owned my car since new (Got it september 2006) and it is only recently I have gotten the fuel starvation issue. Up until this year I have never experienced the issue and that is with running full slicks on track. It was this year when I was running street tires at Pocono that I had the issue for the first time. It could be that I am just a much faster driver and the car pulls much higher G's with the mods and now the starvation is happening. That said in the past I have been on track and literally ran the car out of fuel and didnt have any starvation.

The interesting thing is my brother also has an m coupe he has owned since new and he has not experienced the issue. He is just as fast on track as me.
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      10-28-2022, 06:37 PM   #37
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I would guess the fuel pump is slow failing. I had idling issues with my e46 m3 and it seemed to have gone away after replacing the fuel plump. I haven't taken the z4m fuel pump apart but it's different from the e46 m3, which I'm not sure can be modified for an aftermarket like an e46 m3.
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      10-09-2023, 11:50 AM   #38
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Finally getting back to this.

I have a solution in the works. I'm going to adapt a spare Walbro 255lh/r pump in the tank. The pump will be mounted onto the current stock fuel pump 'canister' and wired in parallel with the oem pump.

I have an inlet hose that will reach all the way to the driver side of the tank, attached to the siphon jet hose to keep it submerged.

The outlet of the pump will plumb right into the stock canister, dumping fuel in there from the driver saddle side. I expect to run this pump full time.

Only two concerns are extra current draw on my fuel pump driver (I think it can handle it, will verify), and by constantly transferring fuel to the passenger side, the fuel level sender may always think the tank is full.

First issue may be fixed by running two separate power/ground through the fuel filter bulkhead and hook them up to a separate switch if I need (or one of my spare AEM outputs).
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      02-18-2024, 10:08 AM   #39
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UPDATE: Fuel starvation seems to be fixed. Specific corner(s) on lightning where the issue would manifest itself over and over, are gone. Matter of fact, I ran a few sessions on nearly 1/4 tank with no fuel starvation!

1. Added a Walbro 255lt/hr fuel pump attached to the current fuel pump canister
2. Routed the inlet (that white barb nipple at the bottom of the pump) over to the driver side via a Hydramat (smallest I could find). I had to use a mini camera to see all the way in side the tank but slid the hydromat as far down as possible. NOT an easy task and requires patience and some strong neck muscles! Used submersible fuel hose to attach it. Magents under the tank to keep the hydramat inplace, although it will barely move as it is.
3. Walbro pump wiring is simply T'd off the current fuel pump wiring. The Walbro is never run at high pressure, so the current draw is very low even when it's running 100% of the time.

Installation is such that I can insert/remove the 2nd pump fairly easily with AN fittings and submersible hose everywhere.

No increase in fuel pump noise inside the cockpit.
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      02-20-2024, 12:41 PM   #40
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Fuel level

What did this do to your fuel level reading?
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      02-20-2024, 12:45 PM   #41
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No difference. Obviously, eventually the passenger side of the fuel tank will fill up and spill back over to the driver side, but if I remember correctly, there are two fuel level floats in the tank. Both are read and the final tank level is calculated from that.

Technically, if you ran your car for one hour, the OEM jet siphon itself would moving fuel over from the driver side to the passenger side to the point where it would overflow back to the driver side... I'm just doing it at a faster clip.
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