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      10-19-2021, 02:31 PM   #23
Vanne
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love that radium kit
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      10-20-2021, 08:16 PM   #24
Michael9218
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Quote:
Originally Posted by Vanne View Post
love that radium kit
LOL, have you tested this kit on track yet?
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      10-22-2021, 12:07 AM   #25
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Not yet, but I have an option to buy it very cheaply..
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      11-07-2021, 07:59 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, 08:26 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, 10:46 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, 10:57 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, 07:39 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, 09:51 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, 04:40 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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