hans14914

I am curious if anyone has any experience with the Bosch Motorsports B261-205-413 type pumps on the 928. They appear to have the same specs as the venerable 044 pump, but have an 8-bar line pressure over the 5-bar of the 044. Is this too much for the stock regulators? Would this more powerful pump be a better replacement for a single-pump conversions (for those with late model cars trying to avoid the intake failure).

Thanks,
Hans

RicerSchnitzzle

Can't see a benefit as the 044 will flow more than most boosted 928's can use. Would it hurt, not sure.

FlyingDog

Additional pressure means additional heat. I wonder if you're more likely to have boiling problems. Other than that, I don't think the extra line pressure would be a problem. Some of the boosted cars run pressures higher than 8bar with the FMU cranked up.

AO

Hans- The 044 pump is good to about 650RWP (sustained). Why you'd want anything more than that is beyond me. Heck the stock pump can make it to a little above 500RWHP. Most people go to the 044 pump when the stock one dies. The Murf Stage III uses the stock pump.

Lizard928

Andrew,
Have you tested this to 650RWHP?

John Kuhn is finding he has to up the voltage to keep up and he isnt even breaking 600RWHP.

Everything I can find says that it tops out at 700NA HP and 600 boosted HP. But none of them say crank or wheel, so I would plan for around 550 rwhp out of it safely. But if you can prove me wrong I will be more than happy to see it!

AO

Hell no, I haven't tested it to that. LOL!

I just recall seeing it somewhere that it would support upto 650RWHP, but then there are a lot of caveats that come with that number as there are so many things that can affect HP and fuel delivery. My main point was that Hans's setup will likely yield somewhere around 450WHP, so if an 044 will be overkill, why even consider anything else?

Lance J

side question....does anyone know where to get a replacement spring that goes in the out put side of the pump secure by a 19MM bolt the connects the line the runs to the filter. there is a small spring that goes in like a spacer. i lost my now my wont stop leaking fuel

AO

Are you talking about the crush washer?

RicerSchnitzzle

Must be the crush washer. Only spring is in the check valve and you can't see it. Most autoparts stores will have them.

Lizard928

I have 2 check valve assemblies from 044 pumps. Brand new if anyone needs them.

Not going to be running that style in my setup.

Bill Ball

Well, then, it looks like George and I should install the second 044 in his car before we go racing. We've been fighting with falling fuel pressure at high speed and have eliminated a lot of other potential reasons.

slate blue

Most Bosch injectors have an 8 bar limit, there is gains to be had with the higher fuel pressure, I will look at higher than the 43 psi my car runs. The heat in fuel would be not a worry. Current technology is to use at least 5 bar.

In F1 they capped the fuel pressure at 100 bar, some teams were running over that. I will be very interested to see what you find out.

Greg

ptuomov

Just a little note on comparing pumps. It's very important to get the flow rate as a function of the fuel line pressure. Not surprisingly, all pumps that I have seen are producing lower flow rates when pumping against a higher pressure. For example, if you go to Fuelab's page and check out the various versions of Prodigy pump, you'll see the curves. The curves are by the way very different for different pumps.

The same pump will support more hp in NA carburated setup than in NA EFI setup and more in NA EFI setup than in supercharged EFI setup. This is because the pressure against which the pump has to pump is different.

Also worth noting is that the relevant pressure for the injectors is not the absolute pressure but the pressure differential between the fuel rail and the intake manifold. Thus, if one boosts by 20 psi, one has to hook up the fuel pressure regulator reference line to the same 20 psi boosted manifold, so the regulator knows to up the fuel pressure by the same 20 psi. This leads to sometimes very high fuel line pressures that the fuel pump has to pump against, which can dramatically reduce the flow rates.

Then, there's the return line. In the conventional return system such as 928's, at idle a huge quantity of fuel is returned to the tank. This means that the fuel return line will either have a very high pressure or one has to change the lines to larger diameter ones. The former is risky and latter is a PITA. The solutions that have been used in boosted cars is to hook up two 044's in parallel and use a Hobbs switch to turn on the second 044 only when there's some boost in the manifold and when not much fuel need to be returned anyway.

A new solution that I am working on is to use a Fuelab Prodigy pump that takes a desired flow rate signal and connect that to the MAF signal. This setup, should I ever get it to work, would be very close to a flat-head system. I think I can run this with huge flow rates with the stock return lines.

heinrich

Higher fule pressure REQUIRES new fuel lines ... just sayin'

Lizard928

Sterling, I wouldnt plan on too much more with the stock in tank pump helping it.

Bill, what power levels is George running? His car is boosted if I am not mistaken either.
For anything over 550RWHP when boosted I would run twin pumps.
I already have 2 new 044s which will go into my TT car, I will run them on seperate switches so that I can only run 1 if I should so choose.