Fuel Flow problems and troubleshooting [Stock Only]

[xandalis]

Alright, so I'm working on a lifter/payload for The Simple Heavy Lifting Challenge, and I'm running into some problems. My problem, is this: the 4th stage in (stage 2 in this case) reads as having let's say, 1200/1500(ish, I'm rounding here) dV on the pad. After liftoff, by the time the previous stages have been dropped and stage 2 is the current stage, it's down to about 800/1100 dV at stage sep. I'm using 3-fold asparagus symmetry, and do not usually see this happen. I suspect that it's my engine clusters (I'm not using rockomax-engines) of LV-T45's causing the problem.

Anyway, a bit more on the staging flow (as intended anyway): S5 stacks feed into S4 stacks, which feed into S3, which feeds into the primary lifter body in S2. Should I try adding more fuel feeds, or is this more of an inherent problem with asparistagers that I haven't noticed on my others until now?

-Edit: Also, the primary stack core is a 1m stack with 3 2.5m stacks radially mounted, all 4 stacks have engines, and I've "loop fed" the fuel lines between the 1m core and the 2.5m radials to ensure (in theory anyway) even fuel distribution at this stage. (again, the stage that seems to be eating fuel for no reason).

This is really starting to cause some hair loss on my end, so the help would be greatly appreciated

Edited June 8, 2013 by xandalis
Forgot some tech info

[Atanar]

Your description is hard to understand, and no matter how precise you describe it, on such complex things a screenshot is nessecary to follow what you are talking about.

And yes, delta-v-calculations with fuelpipes may be bugged on various mods.

Also, see that your asperagus fuel pipes are all on the top tanks or you might encounter some weired emptying of middle stage tanks.

Adding more fuel pipes than 6 for a 6-booster asparagus is not a good idea. Fuel lines have no limits and distribute the fuel very well if set up correctly.

Edited June 8, 2013 by Atanar

[xandalis]

So, sounds like I'll have to go tweak the positioning of the lines. As for mods, non-issue: this is a stock build. Thanks for the tips, but no screenshots will be posted until it's ready for entry into the challenge. Yes, I'm a secretive-type when it comes to development.

[Nao]

Earlier stages could drain some fuel from top ones if there are fuel loops as you said.

You could launching the thing on a pad with clamps holding the center stack and check if the fuel drains properly, if not then its a fuel loop problem.

[entaran]

I tend to put my asparagus fuel lines on the bottom stage just above the engine. I find that it distributes better that way. (plus it makes no sense to pull fuel from the top of a gravity fed tank)

[xandalis]

Thanks for the responses. I did indeed have a bad loop, caused by a phantom fuel-line (this build has been plagued by VAB bugs). Not really sure if was actually a phantom fuel line, or some other part (say, an engine?), but I finally did get it to stop bleeding fuel.