Pressurise the surge tank?
 

Was thinking about fitting a regulator to the surge tank over flow, thus pressurising the surge tank and giving the main pump a bit of a head start?

Has it been done before? Any reason why not? Seems like a good idea to me, but i cant find any info on it, so there must to be a reason it isnt a common place thing...


Im thinking a Carter Black (or similar) lift pump, dead head reg on the overflow (or bypass style??), adjusted to maybe somewhere under a bar surge tank pressure?

Main pump is a bosch 044

Please feel free to tell me what is wrong with this idea

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https://www.google.com.au/url?sa=t&r...64542518,d.dGI

If i used this^ at the surge tank over flow (as per diagram post 1), and connected the vacuum/boost port to the intake

manifold, adjusted it for maybe a couple of psi above atmosphere, then at intake vacuum

conditions it will be pretty much wide open, so the lift pump isnt getting overworked and at

boost it will be a couple of psi above my boost pressure, effectively giving the EFI pump a quite a decent head start

Please feel free to pick this idea to bits. It seems so simple, yet no one seems to be doing it, I'm sure i'm missing something here..

*light bulb* would having the extra regulator in the system make it impossible to adjust or create weird pressure fluctuations or something?
because it is essentially pressurising the return line too.

Fuck it, think im just going to swap the 044 for one of these mother-huggers http://www.injectorsonline.com/images/products/50.jpg
350lph@5bar, out flows 044, built in suction pump, quiet, AMG mercedes spec, ra ra ra

Pressurizing the fuel going into the pump could (very unlikely though) damage the pump if it's too high a pressure. A fuel pump can only create so much pressure and is designed to do so with unpressurized fuel. If you're having pressure/flow issues then you should look into upgrading your fuel pump(s). While a clever idea, you're adding complexity to a system which doesn't need it, with added cost, and time to tune it. As all surge tanks I have seen have the return at the top (thus ensuring a full surge tank) having some amount of pressure before the fuel can escape is redundant.

A surge tank is designed to ensure that your engine has fuel during high G maneuvers that might cause fuel starvation if one only had a fuel tank and it was less than full. Each one should be designed for the car it will be in and take into consideration things such as maximum fuel requires (over some short time interval) and longest time interval where the surge tank will not be able to be fed by the tank.

Absolutely unnecessary complexity with no benefit.

The purpose of the surge tank is to eliminate the possibility of fuel starvation from slosh.

If you need to "boost" your main pump then maybe it needs an upgrade.

There are several pumps available that will flow enough for really high (600+) whp levels. If you need more maybe you should be looking at dual pumps.

If you need more pump there is a partially submerged dual bosch 044 surge tank avaliable. I've been using 1 for almost 2 years with great success.

You usually plumb your FPR return back to your surge tank. Pressurizing it would just increase the load on the pump with no gain in this configuration since you are now venting to an area with higher than atmospheric pressure. You are better off up sizing your surge tank outlets or increasing the height of the tank to increase head pressure.

Yeah, I might review the surge tank outlets size, thanks for the heads up. Re; plumbing fpr to surge, did you check the diagram in the original post? - it is plumbed that way - it is exactly the same as a conventional external pump surge tank set up, except with another regulator on the surge tank overflow, the idea being to get some extra money's worth out of the lift pump by creating some head pressure feeding the efi pump.

I dont really think having a bar or less of extra pressure in the return line would hurt anything, as long as the fuel rails are getting the right pressure, which might actually be the problem - having two regulators fighting each other, pressure control could get messy.

Anyway, its all bullshit until someone tries it, which wont be me now, just bought a "veyron" pump, which should hopefully be exactly what im after - a bit more pump than one 044 and hopefully less noise! Kinda uncharted territory though it seems

Incorrect in terms of EFI pump power input/load, pressure pump is still only lifting the same mass flow (if maxxed out , otherwise say 15-35% more ie the point of the exercise depending on pump vol/head pressure relation) to rail pressure (from a higher base pressure due to pressurised surge), the differential across the rail FPR will simply be less (ie less heat generation across the FPR, it is simply more open), the efi pump power required/absorbed (for the same mass flow) will actually be less ;) Or you get significantly more flow to target rail pressure from same power pump, the aim of the game.

Provided the rail FPR can flow ~15-35% more than it does now the regs will not fight each other, you simply reference the one on the surge return to tank to atmosphere and the rail FPR to manifold. If you were running bullshit drag boost (80+PSI) you could use an EFI pump as a lift pump and reference it to manifold pressure (or to fuel rail pressure) too (but a lower differential pressure than the rail reg) to allow the pumps (effectively running in series) to maintain volume against the much larger head pressure by better sharing the pressure rise at high boost.

^Thanks to your generosity with your engineering insight,Slides , i ended up trying this out with a cartr black(4601) and a 0-30 psi reg feeding the surge tank feeding the pierburg e3l. Initialy set to 12psi,as a seeminglysensible (to me) starting poin compared to the full 18 pound it it capable of (just), it seems to work well but maxing out the pump relay, im guessing the differnce in current draw between a freeflow cartergold andthe blavk at 12psi. Also of note was that the pierburg (semi solid mounted) was completely inaudible against the fully floating rubber mounted carter pump at 12psi.
While im rewiring it to decent specs im thinking to dial it down from 12 to maybe 6 or 8.
My question is regarding pressure calculation;
Is it straight addition, or a multiplication of pressure ratio?
The tuner has set the base pressure to a manly 65psi so whilei was in there chasing fuel restriction i thought id try this idea out after all.

For our purposes (although somewhat dependent on pump design and theory=/=practice due to absolute pressures possibly expanding clearances in pump bodies/parts) you can use simple addition for what is close enough to incompressible fluid in this case. If it was compressible like intake air you would be looking at pressure ratios.

So you just add or subtract the surge pressure depending on what you are working out.

That is a very solid base pressure, are you trying to push more flow from existing injectors? I guess with even half a bar in the surge it isn't too much above the standard 3 bar base, if you are not going to run stupid boost levels the efi pump should still maintain the differential across the board.

Thanks Slides. Yeah Im not sure why he's got it up so high, i think he just likes the lower duty cycles and then chucked maybe another 5 or 10 on it to keep it fat while iv got the car back to a few little things before it goes back on the dyno. Its running 1000s and 1400s.
Goals arnt too amazing - pump gas and a s3 diff housing. The way its going looks like it might be making 400 well before 15psi!
Edit, so it probably massive overkill, but i like the idea, and its nice to have plenty of headroom.

Something sounds wrong. So your running 65 base therefore 80 at 15psi.

Stock lines? What reg are you using? Also most run the fuel rails in parallel not in series.

have you upgraded the wiring to the pump?

Yep. I couldnt believe it either when i picked the car up. AFRs are good but a bit fat. Im guessing he dialled it up a bit to keep things safe till he gets the car back, but it still pretty bloody high. Ill pick his brain on that next tim i talk to him.

3/8 and -6 feed, parralel rails, turbosmart 1200 fpr,
5/16 8mm return.
Wiring is the pissy microtech set up worked fine with carter/044 for 10 years. Project for tomorrow morning is rewiring to 60a relay and fat-arse cable.

I have still been having great results with the pressurized surge tank that I am running, it eliminated all the cavitation and the fuel pressure drop at high rpm/load. It also allowed for faster start ups as the 044 did not have a check valve. Good luck getting it lined out.

Stay tuned, I'm actually going to try to use a pressure opening check valve on the surge tank return line instead of a regulator. Well see how it works.

Glad to know im not mad then. Got into a massive arguement with the guy at the speed shop when i went in there to get the pump and reg. He couldnt get his head around it.

Kevinbtz, glad its working out, i have to admit i probably woulndt have invested into doing it untill you did it first.

T-von, that sounds cool as. - and off i go to google what
pressure opening check valve is..

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Trust me dude, there are so many "experienced" or "expert" people who have NFI what they are doing when you step slightly outside convention/normal servicing etc. It is especially frustrating when you have the knowledge to do stuff yourself but not the tools/equipment/space/time.

I had a "local expert on BT50s" servicing mine when I lived in the Lithgow district, my car developed a bit of steering pull at one stage, I can't remember if it was after a dodgy wheel alignment when I got new tyres or just as the suspension settled a bit, instead of balancing the castors/leaving a small asymmetry so it pulled straight/(very slightly to side) he left the car with over a degree of asymmetric static camber in an attempt to get it to pull straight (maybe he worked on graders in the past??) :lol: it still didn't, this guy owns the workshop and is training apprentices, using an expensive aligning rig :( .

It is very good to learn tips and techniques for common stuff from guys like that as it is their bread and butter, but as soon as it gets complex you need someone that really knows their shit or a nerd who can work it out from first principles.

I really don't see much of a point? Are you trying to solve a problem that you're running into that requires adding this much complexity?

We run a 60-70psi in most of our cars that run modern injectors. We would rather have the pumps working alittle harder and keep the injectors at lower duty cycle. Some Model/Brand injectors do strange things after being at high duty cycles for long time.

When you have 3-4 walbro 400's at your disposal you can afford to do it.
My own RX7 has two Holley 1800s on it so i have plenty of pump at my disposal.

You should look at base pressures for some of the new direct injection BMW's. You will be nicely suprised. We are so far behind.

To be fair I don't think conventional port injectors would last very long with DI rail pressures either :lol: I don't fancy suffering fluid injection and having the lower half of my arm debrided.


Do you have your own flow tester or don't find too much difficulty in getting flow and latency data for the higher base pressures?

I've been getting the same impression lately. V8 boys and dealership mechanics in particular
Also you wouldnt believe it but ive been through the same shit re getting a decent wheel alignment on my 4x4 diesel work pig. Had a beautiful alignment ( by yhe mob that does my mazda) on it prior to getting new tyres ( maxxis 980, i highly reccommend for an agro A/T that is quiet and grips like bejeezus on EVERYTHING and is still quiet)
Went from perfect to pulling to the left. Took two goes to still not get it right. Oh well, i cant finish rolling my smoke when the lights go green now.