05-19-2018, 03:49 PM | #23 |
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05-19-2018, 11:42 PM | #24 |
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How does a fuel pump solve pickup issues? Doesn't make sense to me, the issue is fuel sloshing to the wrong side of the tank during high G turns, not the fuel pump being too weak to keep up.
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05-19-2018, 11:45 PM | #25 | |
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Exiting the keyhole (right hand 90 degree carousel type turn, off camber) while unwinding the wheel and applying throttle, I can get limp mode every time I am close to 2/3rd fuel or less. It does not happen in left hand turns. Just right hand turns with high G forces. |
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05-20-2018, 01:43 AM | #26 |
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I found info that the passive jet pump on E36 is driven by the return fuel line. In the M2 it's driven by a split line from the electric pump directly inside the tank.
In the E36, the flow in the return line, and as a consequence the jet pump too, will get very weak on full throttle since the return line get's fuel from the pressure regulator at the engine. Excess flow from the electric pump will be dumped in to the return line to keep the correct pressure. When on full throttle there is less excess flow since the engine is taking most of the fuel. Hence the classic behavior of starvation on long right handers on full throttle. The M2 jet pump is driven by the flow from the electric pump directly in the tank. But as you can see on the diagram posted earlier there are some pressure regulators and stuff inside the tank. My next step is to try to understand how they affect things. |
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05-20-2018, 02:10 AM | #27 |
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So after the T-connection split from the main fuel line, the fuel going to drive the jet pump goes through one pressure regulator (no 7). And after that there's a split to a pressure control valve (no 11) that dumps excess fuel in the tank. No idea why there are two...
In theory this is much better than the E36 setup. In the E36 the flow driving the jet pump decreases with more throttle. In the M2 the flow driving the jet pump should be constant since it is driven by a constant pressure. The only situation where the jet pump would decrease pumping is if the electric pump is saturated, not being able to keep up delivering what the engine takes, resulting a drop in fuel pressure out from it. And of course, if the electric pump is sucking air the jet pump will stop. Which everything points to is what happened to me. How other cars correct themselves after a few minutes is odd. Would like to know how. Last edited by MagnusT; 05-20-2018 at 02:23 AM.. |
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05-22-2018, 02:17 AM | #28 | |
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Okay, continuing my thoughts on how it seems the fuel system works. Take my thoughts for what they are, an analysis from available info, not an absolute given truth.
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There is a mistake in my above description about the M2. The pressure regulator inside the tank works exactly like in the older cars, it regulates the pressure to the engine by dumping excess fuel back to the tank exactly like in the older cars. Just that it's now located in the tank instead of in the engine bay. This results in the exact same behavior, increasing the throttle makes more of the electric pump's output go to the engine, leaving less and less flow dumped out of the pressure regulator which in turn leaves less and less to drive the jet pump. And as in the older cars, the more flow the electric pump can over deliver, the higher up in the rpm range the pressure regulator will still dump enough flow to drive the jet pump at full speed. So nothing's changed really. ---------------------------- I had a look at Dinan's pump upgrade rebuild kit. What they do is simply drive the jet pump directly from the output of the electric pump instead of as in the original setup drive it from the excess fuel dumped by the pressure regulator. Since we don't know how much the electric pump can over deliver, and therefore don't how much fuel is dumped by the pressure regulator to the jet pump at different engine loads, it's hard to analyse pros and cons. But generally the jet pump would have more fuel to power it with the upgrade. But at higher loads, when more percentage of the electric pump fuel output goes to the engine, the jet pump will compete for the available fuel output in the upgraded setup instead of shutting down at higher engine loads and leaving all fuel that is needed to the engine. Again, this depends on what the electic pump's maximum flow is, how much it's capable of over delivering at full engine load. And it is possible there is an inverse pressure regulator built in to the Dinan kit's machined T-connection, shutting down flow to the jet pump when available pressure decreases under a certain value. But I doubt this is built in. Here's the install guide for the upgrade kit: http://files.dinancars.com/webresour...b74b2d5746.pdf Last edited by MagnusT; 05-22-2018 at 02:28 AM.. |
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07-08-2018, 09:33 AM | #29 | |
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Since BMW hasn't come back to me on this issue yet, is your solution the same a s mine, fill up, fill up, fill up, fill up... |
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07-08-2018, 09:54 AM | #30 | |
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Will the fuel redirection compete against each other and the HPFP with more power? I’ll find out in a couple weeks after I install the Dinan turbo. I won’t be running an aftermarket down pipe, just to rule that out as an issue. If you do get some kind of “fix” from BMW, please let us all know. |
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07-08-2018, 10:27 AM | #31 |
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What I think is very strange is that my car completely dies on me on the track, even with the whole pump assembly swapped out. Yes I could restart it but it would only run on a few cylinders for a handful seconds and die. But that's it. Until I fill up a few liters fuel. Most of you other guys seem to get limp mode. Which for a few disappears by itself after having the car just parked a while.
Am I alone or maybe not with this behaviour? |
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07-08-2018, 10:39 AM | #32 | |
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07-08-2018, 11:02 AM | #34 | |
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07-08-2018, 11:20 AM | #35 |
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Ah, interesting!!!! They swapped the whole pump assembly but there are other parts that can fail in the left side of the tank?
The tank had 14 liters in the left half and 0 in the right when they checked the first time around. The dash gauge showed ca 1/4. Do you know what it is in the tank that fails? Edit: On the street I can drive the car down to one or two liters left in the tank. |
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08-01-2019, 11:06 AM | #37 |
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I just did an open track day with the Dinan turbo, BM3 Stg 2H E30 with E30 fuel, and was able to run the tank almost dry several times.
The dinan LPFP mod fixes the low fuel level pickup issue, and should not be confused with HPFP crashing if your car is modified. |
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08-01-2019, 11:59 AM | #38 | |
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Are you running an OTS tune or custom? What does the "H" stand for in Stg 2H? |
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08-01-2019, 01:01 PM | #39 | |
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Halim modified the OTS map to take advantage of my Dinan turbo. He’s done this for a few of the Dinan turbo guys to hopefully come up with some OTS maps for the Dinan turbo since it’s more off the shelf than larger turbos & tunes. |
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08-01-2019, 03:37 PM | #40 |
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I've been talking to them about a Dinan OTS map. Supposedly they're working on one. I have a Dinan turbo as well but haven't tuned yet. I was going to after I do my intercooler and down pipe. They said it might be ready in a couple weeks or it might be a couple months.
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08-01-2019, 05:23 PM | #41 | |
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Last edited by M2C AW; 08-01-2019 at 06:51 PM.. |
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08-01-2019, 08:54 PM | #43 |
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Agreed...I learned the hard way, twice, that once I am below 1/2 I need to pit and fill up.
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08-02-2019, 06:04 AM | #44 |
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Why didn’t BMW install the pump and pickup on the other side? Most tracks are clockwise so you always have more fuel on the left side of the tank due to g forces!
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