An eye on the provinces

Rich H · Post by **Rich H** » Tue Dec 19, 2006 3:13 pm

SELC*CK, the main contenders have had a big bitch fight on this thread. If you don't bother with SELC*CK anymore (And who can blame you!) this sums it up:

OK, we all know Scruffy is blunter than a fu*cked pencil but please. If nobody should be allowed to be outspoken certain product's pitfalls then what is the point of this bloody forum?

It's about fuel pumps BTW and how they can suffer form fuel starvation. Mostly when they run out of fuel to pump, but that seems a little lost on them

r055 · Post by **r055** » Tue Dec 19, 2006 3:23 pm

I glanced over this the other day...

Post by **campbell** » Tue Dec 19, 2006 9:45 pm

I got bored by the end of page 1, but it was entertaining.

The best bit was when our Neil waded in

robin · Post by **robin** » Wed Dec 20, 2006 11:44 am

Shame, because in amongst it was a crucial nugget that may actually have made sense to discuss.

One post suggested it might be possible to deadlock (my word, not his) the pump(s) in the eductor design because if you pump the collector dry then there is no fuel to spin the eductor and if the eductor isn't spinning you cannot refill the collector. Thus you need to stop the engine and let the collector gravity fill, which is OK on a full tank, but on a near-empty tank might take some time.

But is this true? We will never find out because the egos and slagging culture got in the way

Tut - perhaps you can ask Gaz directly to comment on the above - hopefully this is a misunderstanding and not an issue (or Gaz can comment directly if he's on here - are you?).

Cheers,
Robin

Rich H · Post by **Rich H** » Wed Dec 20, 2006 1:16 pm

The parasitic pump will fail when the main pump runs out, but that will only happen when you have used the .4l in the collector tank. The parasitic pump will always provide more flow than the main pump requires as the parasitic pump is so efficient 1:4 litres pumped but it does bleed power from the main pump, if you were on the limit of the main pump then you may have a problem but given that the fuel return goes back into the colector as well it should maintain feed. They are used in helo fuel tanks as there are no moving parts and no electric involved, just a nozzle and a cunning design. (Think carb jet and you'll understand, it's the same principal, the airflow "sucks" out the fuel) The flow used to power the pump is also added to the output.

The main point that seems to have been missed is that the pump design has no effect on startvation. If the pump can flow enough fuel at the right pressure it will work for a given engine. If the pump doesn't get the fuel to pump that is a fuel tank and feed problem not the pumps fault.

How long would a left hander be to used .4litres +return fuel? I would imagine that it is more of a problem for traditional feed and pressure setups as the parasitic pump will pump vapour/air as well, but a traditional pump will not (not very well anyway) so a brief interruption to the trad pump will bring a temp loss of flow and then a delay as flow is restored but the parasitic one will not delay as soon as fuel is restored.

my 2p

Rich

robin · Post by **robin** » Wed Dec 20, 2006 2:50 pm

RICHARDHUMBLE wrote:The parasitic pump will fail when the main pump runs out, but that will only happen when you have used the .4l in the collector tank.

Correct, but at that point as there is now no flow out of the main pump and the collector is empty and the parasitic pump isn't running, you end up in a stalemate situation; only gravity feeding of the collector will allow you to regain flow, and on a nearly empty tank that might be a long time coming.

How long would a left hander be to used .4litres +return fuel? I

About 10-20 seconds depending on power output, and throttle application. But don't forget it needs enough headroom to recover on the next straight (still on full throttle) before the next left hand corner. Could be made worse by downhill run into corner (or uphill, whichever way drops the fuel level relative to the collector.

Oh, and you don't want to think about what's happening to your oil while all this cornering is going on

Cheers,
Robin

tut · Post by **tut** » Wed Dec 20, 2006 3:19 pm

Robin

Have read the thread as it concerns Craig, Brian and myself, but could not debate on it, its not knowledge that I have.

I will put your question to Gaz, I dont think he reads on here, and e-mail him yourself and Richards points.

One obvious point to me is not to let your fuel get too low. There is a lot of crap talked about weight at times, of cause the lighter the better, more so in very short Sprints and Hillclimbs, but not so much on track, where other factors are going to have a bigger influence on performance. I am 35 kgs lighter than you or Scotty, which I think equates to a full tank of fuel.

One point that seems to be consistently missed is that the talk is concentrated around racing, and I presume the LOT type races will be around 30 mins max. When we do a track day, many of us are at racing speed as soon as we leave the pit lane, and are out for 40 mins plus. I often back off if I find myself on my own, and wait for another group, but I know others that drive flat out for the whole period. Any problems should show up then, especially on a circuit like Spa. In fact I believe oil has been one, but not sure about fuel.

tut

Rich H · Post by **Rich H** » Wed Dec 20, 2006 4:22 pm

Are there may constant LH corners 20-20 secs long?

The parasitic pump will stall when the fuel in the collector runs out, but this is because this is a tank problem, not a pump problem. The pump is solid, but the design of the tank (With the pump off to one side) is flawed.

Best option would be 2 parsitic pumps running from the ends of the tank to the collector, this ensures (As they will pump vapour as well as fuel) you will always get a flow. Problem is in the installation. Bear in mind that you will only need a pickup pipe at each end as the parasitic pump will create the vacuum for you at the pump end. Job done (Bar the actual manufacture, fitting and installation...!)

(For me this is clearly an exersize in mechanics as there is no way I'm going to have to worry about that for a looong time

)

Post by **pete** » Thu Dec 21, 2006 1:52 am

Thanks I now know how a pump works.
Kind of (possibly enough to draw it in such a way it would make sense to me. Perhaps enough to explain it to someone else. Not enough to build one.)

Two questions though:

1. why did it take you two 3 posts to conclude what they haven't concluded in x pages?
2. I don't frequent SELOC much, I don't think I ever post, but fcuk me how big are some of those egos???

Oh hang on - SOUTH EAST LOC. Southerners, that makes sense!!

robin · Post by **robin** » Thu Dec 21, 2006 9:00 am

It's not so simple as all that, and I don't know that we have actually concluded much, but our discussion has been of a technical nature between people who have nothing to prove.

Of course you then waded in with your generalisations about Southerners (I am one!) and off we go ...

Cheers,
Robin

Tom · Post by **Tom** » Thu Dec 21, 2006 1:32 pm

robin wrote:It's not so simple as all that, and I don't know that we have actually concluded much, but our discussion has been of a technical nature between people who have nothing to prove.

Of course you then waded in with your generalisations about Southerners (I am one!) and off we go ...

Cheers,
Robin

ah yes....the north versus south battle..

(Man of Kent faction)

Rich H · Post by **Rich H** » Thu Dec 21, 2006 2:16 pm

As Robin says SELC*CK's a small community stuffed with HUGE egos. We are just a bunch of like minded fools who have a little technical understanding and enquiring minds. Some of us own Elises and some of us live in Scotland too

GregR · Post by **GregR** » Thu Dec 21, 2006 2:33 pm

Tom wrote:
robin wrote:It's not so simple as all that, and I don't know that we have actually concluded much, but our discussion has been of a technical nature between people who have nothing to prove.

Of course you then waded in with your generalisations about Southerners (I am one!) and off we go ...

Cheers,
Robin
ah yes....the north versus south battle..

(Manservant of Kent faction)

Post by **pete** » Fri Dec 22, 2006 6:46 pm

robin wrote:It's not so simple as all that, and I don't know that we have actually concluded much, but our discussion has been of a technical nature between people who have nothing to prove.

Of course you then waded in with your generalisations about Southerners (I am one!) and off we go ...

Cheers,
Robin

Oh no. I can feel SE going the same way and it will all be my fault. Someone should moderate me.

pete

I'm a southerner up here but in England I'm a Northerner

A Pedant writes:-
Your illuminating discussion may not have concluded with a plan how to re-design the pump but your discussion seems to be concluded. On another forum they would be arguing still, but be no further along

robin · Post by **robin** » Fri Dec 22, 2006 7:00 pm

pete wrote: Oh no. I can feel SE going the same way and it will all be my fault. Someone should moderate me.

It's OK, we're mostly thick skinned I think

Your illuminating discussion may not have concluded with a plan how to re-design the pump but your discussion seems to be concluded. On another forum they would be arguing still, but be no further along

Too true.

Cheers,
Robin