Hola señores

fake edit: I don't have enough posts yet to be able to post pictures so please copy past the url's to see the pics. The fuel system is being used to support 6x 85lb/hr injectors (already bought) on a custom Ross Machine Racing rail for a turbo '89 325i.

Got my two walbros in but I'm now realizing that I may have made a bad design choice in how to hook them up.

This is how I originally intended to hook them up. I'm using a dual inlet, center return rail from Ross Machine Racing.

kai.caltech.edu/e30turbo/fuel-DualFilter.jpg

Then I ran into more and more pics of bimmer/Supra guys running all their pumps into one big line, one filter, and then splitting it up via Y pipe to both ends of their dual inlet rails.

kai.caltech.edu/e30turbo/fuel-SingleFilter.jpg

The advantage of the second picture that seems most worthy to me is that you can run the motor with just one pump below a certain boost level and you can not blow up your motor if a pump dies. The advantage of teh first setup is possibly greater efficiency using seaparate lines and filters.

What do you guys think? Andreas at PPF uses number two for his single turbo s38 e30m3 car and that is almost reason enough for me to go with number two. Does anyone know of a car running a setup similar to number 1?

Im also running twin intank walbros feeding a y-block then a single filter....single inlet fuel rail......single return line then split to dual -8 lines at the tank area to get to the twin return hose bibs.

should fix the images...

Hola señores

fake edit: I don't have enough posts yet to be able to post pictures so please copy past the url's to see the pics. The fuel system is being used to support 6x 85lb/hr injectors (already bought) on a custom Ross Machine Racing rail for a turbo '89 325i.

Got my two walbros in but I'm now realizing that I may have made a bad design choice in how to hook them up.

This is how I originally intended to hook them up. I'm using a dual inlet, center return rail from Ross Machine Racing.

<img src="http://kai.caltech.edu/e30turbo/fuel-DualFilter.jpg"/>

Then I ran into more and more pics of bimmer/Supra guys running all their pumps into one big line, one filter, and then splitting it up via Y pipe to both ends of their dual inlet rails.

<img src="http://kai.caltech.edu/e30turbo/fuel-SingleFilter.jpg"/>

The advantage of the second picture that seems most worthy to me is that you can run the motor with just one pump below a certain boost level and you can not blow up your motor if a pump dies. The advantage of teh first setup is possibly greater efficiency using seaparate lines and filters.

What do you guys think? Andreas at PPF uses number two for his single turbo s38 e30m3 car and that is almost reason enough for me to go with number two. Does anyone know of a car running a setup similar to number 1?

So do we need to modify the lines at all to run either single or dual Walbros?

two pumps feeding different ends of the fuel rail is a bad idea. If one pump is stronger than the other (or one pump dies), the fuel will have to reverse flow in the rail on the lower pressure side.

I'm not sure I understand the twin pump thing other than a required flow issue with those injectors. (which I also don't understand). Drag car I assume?

These appear to both be drawing from the same side of the tank. (baffled volume perhaps? does the return go there?) how do you make sure neither pump sucks air?

techno,

Thanks for the heads up about the dual pumps pitfall. I realized that one pump dying would definitely screw things up but didn't think that one pump could actually be stronger than the other. It still seems unlikely given that the two pumps will be identical but I do understand that manufacturing tolerances/random things could lead the pumps to be slightly unequal in power.

Yes on drag car. Building the fuel system to be ready to go into high hp.

The tank pictured is the stock e30 fuel tank and yes it is baffled and yes the return dumps into a sort of pasta bowl welded to the bottom of the tank (done by BMW, stock) just below the stock pump. That square'ish U is my attempt at drawing in the bowl that exists there.

The reason I split the return line is because the stock return line feeds into a hard tube with .23" ID on the driver side (in picture...left=passenger, right=driver) which snakes around inside the tank to the passenger sides and dumps into the pictured bowl. I was worried that the .23" ID return line would not be sufficient to carry all return fuel but I did want to keep it's function of keeping fuel in the bowl.

I'm hoping someone who has messed around a lot with M20 fuel tank modding will chime in.:help

I don't have any guarantee that neither pump will suck air other than following the setup used by turbo supras and the ppf single turbo s38.:evil2

I was never a fan of multiple pump setups. If one craps out you could be dangerously lean, and your car will still run.

It is very common to run dual or triple pumps with the supra guys.

You would be best to tee the pumps into one main supply line, then split it off to both ends of the rail. The return then dumps back in the tank.

I understand some of what the dual feed is trying to accomplish. With such large injectors, the rail pressure drops and spikes caused by the injectors will do bad things. (large injectors drawing from a relatively small volume will cause a large pressure drop, and depending on the distance to the FPR, may stay low for a little longer than one would like... then the FPR catches up, and shortly thereafter, the injector closes... and now you have a pressure spike... just as the next injector opens. :D) Depending on fuel rail configuration, you'd probably end up with rich and lean cylinders and never really figure out why. or worse yet it'd even itself out to "the right A/F ratio" by the time it all gets to the collector in the exhaust pipe and you'd have no clue why there are odd misfires or lean/rich spots in random cylinders at random RPM's.

The problem is it's not really a fix for the problem. The "proper" solution is multiple injectors. The stock manifold isn't really well suited for high RPM high HP applications anyway. The injectors are too close to the cylinder for that. So run modest sized injectors near the cylinder like is done currently so you retain the drivability and control you have now. Then add bigger injectors upstream (perhaps in front of the runners) and pulse all of these together. (continuous PWM signal to all injectors.) With the big ones all pulsed together and way upstream you fix both your pulse harmonic problem and the fuel/air mixture distribution problem you don't know you have yet.

The proper fix on the fuel rail is pulse dampers. Converting to a center feed and dual outlet might work too. Either way you're just trying to buy some time by isolating the pulses of each bank. Get your pulse events for the feed line 240 degrees apart insted of 120.