123quattro

For anyone looking for something more than an 044, these are nice.

Aeromotive A340: 340lph @ 40psi.
http://aeromotiveinc.com/products-pa...-center-inlet/

jcorenman

Hint: Skip the "halving" unless you are max'ing the injectors (in which case you should up-size them instead);
And when you get the SuperMAF installed, zero your WOT map and do your tuning on the main map.

Z

If there's a 20 amp draw from an 044 pump, something's wrong. The specifications from Bosch show 14 amps at 5 bar pressure.
http://www.bosch-motorsport.com/en-U...2776426379.pdf

Here are the current draws at different pressures when an 044 pump was tested.


There's never been a problem with any of the 044 pumps that I've seen installed using just the factory wiring, with no additional relay being used. The stock wiring supplying power to the fuel pump is 2.5mm^2 in area, which is more than enough to supply the required current, even at the length used in the car.

Rob Edwards

Z-

True, but how many amps does an 044 plus the internal FP plus the NBO2 (or WBO2, if you pull it off the stock wiring? (I know Murf sells the strainer to get rid of the internal pump, I have one too). Just for discussion let's say Joe Sixpack buys an 044, hogs out the ring connectors on the stock FP wiring so they fit on the 044 studs, keeps the internal pump, and uses his factory NB02 when he's not sharktuning? All of that is going to be greater than 20 amps when at WOT, no? The wiring to the pump(s) might be ok, but I managed to blow fuse #38 (15A) in my GTS under the scenario above.

One might be ok on stock wiring, but it's trivial to provide a dedicated 12V feed to the 044 (well, trivial unless you use cheapass fuse holders...). Seems like cheap insurance to me.

123quattro

I've always seen 044s installed with a dedicated relay. Chances are if someone is running that pump they are making a lot more than stock power. If you lose the fuel pump under high load in an engine like that chances are you'll melt a piston. Seems like cheap insurance to me.

jcorenman

Rob, the NBO2 sensor draws around 1.7 amps during warmup and then drops to 1 amps (info here, Theo's site). I measured about 13.5 amps for the whole thing-- 044, in-tank pump and NBO2 sensor (my wideband is powered by the ignition-on bus). That's with the stock 55psi fuel pressure, higher pressure will be more amps.

And as Mike mentioned above, the 2.5 mm^2 wire is fine with 20+ amps. There is some voltage drop, about a volt as I recall-- which is only an issue if you need 100% from it (which I don't).

I also checked the pump spec sheet (Z has a link above), voltage is spec'ed for "supply voltage" of 6 to 16.5, with an "operating" voltage of 13.8. I am not sure what that means, exactly, but the curves show performance (flow and amps) from 7 to 15 volts. At 3.8 bar and 12.0 volts the curve is right around 11 amps, and flow is 230 L/hr.

Using a relay and getting the supply voltage up to 13.5v (or so) would raise flow to 275 L/hr, and also increase amps to around 12.5-- according the spec sheet.

I went back and forth on the relay question and decided it was fine with stock wiring. The measured 13.5 amps (at the panel) was pretty close to the 15 amp fuse so I swapped it for a 20A for some extra headroom, and which the wiring is good for.

And then I read Greg B's comments about the pumps not lasting as long without a relay, and now I am going back and forth again...
Gotta go find another six-pack.

BC

I'm going to relay a regular pump this weekend just to see if it makes a difference coming straight from the battery.

123

In my opinion, anybody running the stock internal fuel pump with an 044 external pump really isn't doing themselves any favors. If somebody wants to do that, adding the extra relay would reduce the amount of current that passes through the stock wiring.

Isolating the O2 sensor power from the fuel pump power would be a better option. I know of one stroker that died and wouldn't start because of the fuel pump not running. Because of it not being installed properly, a problem developed with the O2 sensor power, and that was the end of the power to the fuel pump too then. Keeping the O2 sensor power separate from the fuel pump power would reduce the current going through the stock pump wiring, and also prevent a situation like that from occurring.

Using one relay dedicated to the fuel pump is great. Using two relays to run it increases the chances of a failure occuring though. Adding more parts, wiring, connections, and complexity than needed isn't in a very good way to increase reliability. If it was, you'd be seeing all kinds of Rube Goldberg type configurations on professional race cars, instead of them simplifying as much as possible. Plenty of 928 owners have been stranded due to a fuel pump relay. Sooner or later, all relays fail. I'd rather not have to rely on two of them, each of which is just waiting to cause problems, unless there was no other way to do it.

I've never seen an 044 pump failure due to not using one of the second relays, and some of them have been run for years and quite a few miles that way. Not sure how low supply voltage or current can kill an electric motor or pump, since that's how the speed or output is intentionally regulated with some of them. From some of what I've seen, I'm really wondering about the effects of possible pump cavitation due to the reduced pressure on the suction side of the pump. The specification for the inlet to the 044 pumps is why Tim Murphy started making the in tank strainers with the larger outlet, and larger hose size going into the 044 pump.

jcorenman

God points, and one way good to overcome the additional suction caused by a larger pump is certainly to use a larger strainer. Tim's super-sized strainer is a sweet solution, and simple.

But the other way to avoid suction is to push fuel into the external pump. That is the reason that Porsche used the intank pump in the first place. Yes, they can be troublesome and they draw a couple of amps, but they do work well-- and this is a 928 we're talking about.

I did do a quick flow check on the intank pump into a collection bottle-- and it pumps a gusher with a two-foot lift. I didn't measure it-- gushers of gasoline scare me-- but it was many times the flow that you get from the return-line when testing the the external pump.

Cheers,

SeanR

I've already had a relay set up for my pump, was going to go that way for the factory pump to see if I get more juice out of it, so I'm good for the 0fofo pump when the time comes.

Z

That works fine... if the in tank pump and it's strainer can supply at least as much fuel as the 044 pump is trying to pump. If not, the in tank pump and/or it's strainer are just helping to starve the 044 pump, creating lower pressure between the in tank pump and 044 pump, and very possibly causing the fuel to boil in there because of it.

On a couple of different occasions now, when replacing the in tank pump or strainer, gas at the opening of the tank was clearly seen boiling. A drop would be hanging there, with tiny bubbles boiling away in it, and that was at atmospheric pressure, with the fuel and air temperatre probably around 70 degrees or so. Reduce the pressure and/or increase the temperature ahead of or inside the 044 pump, and that's going to happen even more easily.

GregBBRD

Invariably on this Forum, If I say "apple" someone else will say orange......

I add an "extra" relay, because I believe that the stock circuit was designed to "carry" 15 amps.

The Bosch Motorsports Specification page clearly says that an 044 pump needs 14 +/- 1 Amp to make 5 Bar of pressure. If you want to make 8 bar of pressure, you need another amp. And this is at 22 degree C! Get that fuel heated up to a higher temperature and more current is required!

I always put an intank pump in front of my 044 pumps....anyone that has tested one of the intake pumps knows that they will fill a 5 gallons bucket really quickly. The 044 pumps are quieter and last longer, if they have a stock pump feeding them. Bosch makes pumps that are designed to "suck" (such as the pumps on the '87/'88 models) and pumps that are designed to be "fed" fuel (like on the '89 model.) I think the 044 pump is happier being "fed" fuel.

The "stock pump circuit" powers up the O2 sensor, the internal fuel pump, and the external pump, on a 15 amp fuse. Clearly, to run an 044 pump correctly, 15 amps is "borderline". Add in the two other consumers and the 15 amps fuse simply won't do it. The "current draw" is up near 20 amps, when everything is working at its peak. You need a bigger fuse than the actual "current draw" or you will be replacing thqat 20 amp fuse every few days. That measn you need a 25 amp fuse.

Extra relay or a 25 amp fuse in a circuit designed to carry 15 amps.....

Freedom of choice means you get to choose.

But don't sit around mystified when your 044 pump gets really noisy, when the fuel heats up and you are running stock wiring!

hacker-pschorr

Does this do anything to address the fact that the stock outlet in the tank is smaller that what is specked for the 044 pump?

That was the whole point behind this kit:
https://rennlist.com/forums/928-foru...iner-kits.html
https://rennlist.com/forums/8516374-post22.html

We had multiple cars with 044 pump cavitation with the stock outlet. Todd has a double outlet for his car and made the prototype for the single outlet that is in my 81.
We would have preferred to have gone larger, but as you know, there are space restraints.

The cavitation probably isn't an issue for most people, this was in cars making over 500rwhp. But.....I remember reading somewhere on here that starving an 044 is a bad idea at any power level, cannot remember who posted that.

+1
Reason for the larger tank outlet with matching larger pump inlet Tim sells.

I agree the idea behind the in-tank pump is a valid one. Problem is, they are so prone to breaking you go from an excellent setup to a very starved pump without any warning until the air/fuel ratios get really scary from lack of fuel.

GregBBRD

That's a beautiful part!

However, I don't have to deal with the smaller fitting going into the tank, because I use a in tank pump 100% of the time, to feed the 044 pump. Like I indicated, I believe the 044 pump likes to be "fed" fuel, not have to suck it, on its own.

I believe there has been a couple of threads about noisy 044 pumps and noisy stock pumps, when they were not properly "fed". I remember one particular thread, where I told the OP how to fix his "noise" problem.

I have not had any premature failure issues with "new" in tank pumps. I feel that they will "last" for 80,000 miles plus....like they did originally.

I've had the "benefit" of working on these cars, extensively, since they were brand new. I'm going to guess that most of the people here as somewhat "newer" to these cars, than I am. I seriously didn't see any "issues" with in tank pumps until the cars had many, many miles and many years of use on them.

However, as always, there's more than one way to skin a cat.

James Bailey

[QUOTE=GregBBRD;9877026]Invariably on this Forum, If I say "apple" someone else will say orange......

Greg somewhat like the wild wild west where everyone wanted to take down the top gunslinger .....even if they had to shoot him in the back Gets to the basic reason why most people post.....they wish to be heard, respected....and what better way to earn respect than shoot the expert
See you Thursday so we can change those fuel lines on the very brown 1980 !