Gtr Surge Tank/fuel Setup

[raz0r$harP.UK]

Hey,

Got a couple of questions trying to streamline fuelling system for a 400kw GTR. With a surge tank, 720cc injectors, dual entry fuel rail, and braided line, it feeds off:

- GTR pump as a lifter from stock, but this appears to be mounted externally (?)

- 2x unknown external pumps from the surge to a single fuel line under the car

- T-piece splitting fuel line to twin filters in the engine bay, then to rails

- All pumps wired direct to battery via fused relays

- Standard fuel pressure 2.5 Bar

Not sure why the GTR pump is mounted that way, perhaps to wire to battery easier. From watching fuel level gauge cycle up and down, appears to be sending too much fuel around, and returning it to the tank.

Going to replace the pumps & lines for peace of mind, but also hopefully to minimise fuel smell in cabin

- Will a lifter pump (Std GTR/Tomei/Nismo pump) and a single Bosch 044 from the surge handle my requirements? Especially under boost (Up to 2.5 Bar boost)

- Any benefits to having two external fuel pumps running off the surge tank?

- Do I need another inline filter elsewhere?

Cheers

[raz0r$harP.UK]

Another related qu:

Anyone mounted fuel pumps underneath the car?

Where would be best place to do so?

[Sydneykid]

First job is to identify the main pumps, they will have part numbers stamped into the bodies. With that info I can make some exact recommendations.

In the interim, let’s assume that they are Bosch 044’s. Then it’s simple numbers;

720 cc per minute X 6 injectors X 60 minutes in an hour = 259 litres per hour

A Bosch 044 is rated at 220 litres per hour at 12 volts at 73.6 psi.

That equates to 255 litres per hour at 13.8 volts at 73.6 psi

The 73.6 psi represents 36 psi fuel pressure + boost (37.3 psi)

If you are running less than 37.3 psi (2.55 bar) boost then the pump will flow more.

So, depending on you boost level, one Bosch 044 should do the job just fine provided it is getting 13.8 volts ie; has a relay and good solid wiring to the battery/alternator.

“Normal” braided hoses tend to sweat, that’s why they aren’t used inside road cars. You can get “no sweat” braided hose from Earls. They are a little bit more expensive but that gets rid of 90% of the fuel smell problem. The lift (GTR) pump should be mounted in the main fuel tank, they are not designed for external mounting. That will remove a little more of the smell. The best method to eradicate the remainder (of the smell) is to encase the surge tank, pump and hoses in a sealed box with a hose (for fumes) vented to outside (the car).

So all that is left is for you to properly identify the main pumps.

cheers

[Beer Baron]

holy cow batman! when did you get a GTR?!? looks pretty serious mate. i likey.

I would think a stock GTR pump and one single 044 should be fine to flow enough for 6X720cc inj at up to 5bar pressure. the fuel smell is most likely caused by the lines breathing a little. braided rubber lines have been know to breath and smell a bit. perhaps look at repacing them with teflon line (if it's not already) or steel tube. mounting the pumps under the car is no problem providing they do not become the lowest point under there. try and tuck them up somewhere near the spare wheel well, and of course away from the exhaust. also get some better mounts than those ones on there. with rubber 'washers' between the bracket and the car body and a rubber insulator around the pump too. another inline filter would be a good idea. I'd go for an earls one, they flow lots, not much pressure drop and are cleanable and cheap.

[R31Nismoid]

As SK said, need to know whats already there, you might not need two pumps

Although having the GTR pump externally is "interesting".

The big bosch (should you decide to go down that path) would be adequate no problem in single form.

Surely you can live with the fuel smell, it makes you more mentally alert

But drop the lifter back into the tank, it will as SK also said... get rid of some of the smell and a lot of un-warranted hose which is also causing the smell.

My surge is in the boot and i dont get a bad fuel smell at all, only if i leave the car sit for a week and then drive it do i notice it.

Sounds like an interesting setup Vijay

Any more details?

[raz0r$harP.UK]

First job is to identify the main pumps, they will have part numbers stamped into the bodies. With that info I can make some exact recommendations.

OK just took off the clamps and they are both Bosch 979s, which from the Bosch spec sheet flows 165L/hr @ 12v and 73.6 psi.

Based on what you guys said, it looks like I could probably achieve my goals with a single 044. Just worried I guess. Is there any validity in my assumption that using 2x pumps would somehow help to prevent catastrophe in the event of one pump failing? (i.e. if one pump fails the other would provide the required flow to meet the pressure?).

[raz0r$harP.UK]

Hmm.. just noticed another peculiarity.

When I compared the pic of my tank lid with one that performance-wise posted in a DIY thread, I seem to have a fourth fitting there, which doesn't look factory.

Not sure why (I haven't had time to look inside the tank yet).

I don't know why they would do that?

[Beer Baron]

with a little poking around you should be able to establish what it is. It can only really be things. either fuel return, or fuel feed (under pressure). my money is only fuel return.

[Sydneykid]

OK just took off the clamps and they are both Bosch 979s, which from the Bosch spec sheet flows 165L/hr @ 12v and 73.6 psi.

Based on what you guys said, it looks like I could probably achieve my goals with a single 044. Just worried I guess. Is there any validity in my assumption that using 2x pumps would somehow help to prevent catastrophe in the event of one pump failing? (i.e. if one pump fails the other would provide the required flow to meet the pressure?).

If you only have one pump and it fails, the engine stops, you know it and no lean running occurs.

If you have two pumps and one fails, the engine keeps running, you don’t know that one pump has failed, so you could have lean running and you wouldn’t know.

cheers

[raz0r$harP.UK]

If you only have one pump and it fails, the engine stops, you know it and no lean running occurs.

If you have two pumps and one fails, the engine keeps running, you don't know that one pump has failed, so you could have lean running and you wouldn't know.

So what would be the difference if I had, say, a single 044, and that fails (ie only partially working, providing less than full flow) - wouldn't that also result in a lean out?

Just asking as I have spoken to a couple of ppl with similar power requirements who have said to leave a second pump in there as insurance. If I have two pumps and one fails, wouldn't the second pump meet the rail pressure by pumping more fuel to compensate for the failed pump? (up to the limit of the pump)

Oh yeah, in response to my query about the extra fitting, I had a think about it and if that GTR pump is my external one (but located out of the boot), it would need the fitting to connect back through the lid to the filter sock. Just a hassle to properly look as half of the hoses run through the GTR boot bracing.. so hoses would need to be removed and I'm not quite there yet!

[Sydneykid]

So what would be the difference if I had, say, a single 044, and that fails (ie only partially working, providing less than full flow) - wouldn't that also result in a lean out?

Two pumps = twice as much chance of one failing. If you are that worried, run a fuel pressure gauge.

cheers