fuel pump losing the plot ??

[wilbo666]

Shows pressures...

Some more here, but no 341...I'm sure if you google you will come across it

http://www.gnttype.org/techarea/fuelsystem/pumpflows/

Cheers
Wilbo

[Kyosho]

I'm going to hazard a guess it's not actually the pump, or fuel side of things.

I'm going with an electrical design issue.

Redo all of the wiring with brand new, and THICKER wiring.
Particularly run an earth straight to a CLEAN spot on the chassis (For testing, even throw it straight to the battery!) but make sure you have sufficient sized cable.

I'm hazarding a guess as you're running the pump, the wiring is heating up, which causes an increase in resistance, which gives you a voltage drop at the pump, which drops off your flow rates...

[Mos]

Do you even have any idea how much the temperature has to rise by to, say, double the resistance?

[oldcorollas]

277deg C? .....

[jeffro ra28]

Ed, Did you ever sort out the pressure issues on the dyno?
Is what is happening now in the car related at all to what was happening on the dyno?
I think you have 2 different problems.

What sort of data acquisition system was the dyno using? What sort of engines were typically run on that dyno? e.g. mechanically injected engines, EFI engines, 4 cyl, 8 cyl? Has the dyno got its own alternator?
Obviously its a bit late to talk about that crap cause its not on there anymore. But atleast we may be able to eliminate some suspicions.

[Joshstix]

It hasn't been on an engine dyno as far as I know.

[CrUZida]

AFAIK thats the Walbro 255 vs the 255HP.
The normal Walbro starts to reduce at 58psi (or ~16psi boost on a stock 42psi system).
The HP doesn't drop as much.

[jeffro ra28]

It hasn't been on an engine dyno as far as I know.

My apologies. I just incorrectly assumed that an engine of this caliber and build would have been engine dynoed.

[chiksluvit]

sorry i guess i gotta rephrase that..
it works with turbos, but it won't work as well in high pressure conditions.

http://www.roadraceengineering.com/f...pflowrates.htm

the stock supra pump shits all over the walbros
taken from SAU, factory r33 r32 gtr 300zx jecs pump flows 235 l/h compared to 210 l/h both @ 25 psi

so why would you run walbro in cars like these mentioned if the factory pump already flows better?

not saying that the walbros are bad, they're ok and i actually had one in my stockish r32 gtst skyline, car ran stock boost so pump could handle it anyway.

reason why i asked is i didnt know what ed's car had, i assumed it was 2jz with the works, just for attacking his issue from a different point of view.
cheers

[ed]

all right - if linden hasnt already bought a new pump, i might just try new wiring, disconnecting the reg vac, and a full tank of gas and see what happens

otherwise, weve got a plan for either an 044 to drop straight into the tank, or run the walbro as a lift pump to a swirl pot/surge tank, then the 044 as an external pump

[LeeRoy]

If you want to rule out the reg as being an issue i have a brand spankers sard sitting at lindens you can borrow if you would like.

[ed]

i think the aeromotive without vac should be fine

talked to linden today too - we have an 044 on the bench waiting, and weve decided to go external pump and swirl pot, all in one go. the bosch will require rewiring, so we'll make sure that wire is up to task

[oldcorollas]

remember to plug up the vac line

also, log the MAP thru the ECU and see wtf it is doing... if it is doing strange things, you may have larger problems..

hmm.. manifold heating up and leaking with temp?

[Kyosho]

Do you even have any idea how much the temperature has to rise by to, say, double the resistance?

From the calcs I just did (With a few assumptions, such as a 0.2ohm resistance in the wiring already, matched with running 13.5Volts at the pump, and alt putting out 14.4volts.
Calced pump to have a resistance of 3ohms,
and an increase from 20degrees (At which point I use 0.2Ohms) to 50degrees (I've seen alot hotter then this before in insufficient cabling, I've seen plastic melting off etc) you'll get an increase of 0.0234ohms, which coincides with a 0.2volt drop...

Get temp in cable up near 80 odd degrees, and you're looking at loosing nearly half a volt...

See how much the flow rates change from 13.5 - 12 volts? So you drop your flow to some where in there...

[Mos]

From the calcs I just did (With a few assumptions, such as a 0.2ohm resistance in the wiring already, matched with running 13.5Volts at the pump, and alt putting out 14.4volts.
Calced pump to have a resistance of 3ohms,

Okay, so pump draws 4.5A.

and an increase from 20degrees (At which point I use 0.2Ohms) to 50degrees (I've seen alot hotter then this before in insufficient cabling, I've seen plastic melting off etc) you'll get an increase of 0.0234ohms,

Close enough to.

which coincides with a 0.2volt drop...

I'm not following your calculations there. Isn't is 0.1V drop?

Get temp in cable up near 80 odd degrees, and you're looking at loosing nearly half a volt...

I get 0.18V?

See how much the flow rates change from 13.5 - 12 volts? So you drop your flow to some where in there...

If we assume a linear drop, taking the 250lph at 43psi we would get around 11.7lph drop with a 0.5V drop on supply. This translates to around 4.6% in drop in flow.

From Ed's original post, approximately:
9.5k->8k -> 16% drop
8k -> 7.5k -> 6.4% drop
7.5k -> 7k -> 6.6% drop

Even if the supply was dropping by 0.5V, the fuel starvation seems to exceed that.

I'd like to calculate the Joule heating of the cable, but I'd like to measure the exact size of the cable first. 0.2Ohms is quite high and translates to around 0.44 square mm cross sectional area for an estimated 5m length (shorter length estimates decrease the x area). From memory the cable is more likely to be around 1.5 sq mm, which, at 5m, would correspond to around 0.06Ohms.

Mos.