Gjorde en tankevurpa om bränslesystemet. Skrev igen på bimmerpost men postar texten här osså:
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.
MagnusT skrev:
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.
In reply to my own "no idea why..." above.
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.
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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/webresources/datasheets/c21932ad4aa6ef213e2d9db74b2d5746.pdf
Magnus Thomé
Bromsar bäst som bromsar sist...
Och håller med 
