Too big a fuel pump???

[gtstii]

hey all, just a quick tech question:

if you select an aftrmarket fuel pump for your car which flows much more than you need, I realise that this wont make the A/F ratio any richer cos it's controlled by the pressure reg. but I've heard that you can have problems with the fuel having to keep recirculating back to the tank as the pump supplies more than is needed and that this can cause the fuel to heat up?

is this true??

[benm]

I'm not sure if that is true or not, it probably is. I replaced the standard R33 GTS-t pump afew months ago with a Bosch 040 and apart from noticing a difference immediately without touching anything else (smooth at higher boost) i have not had any problems.

* GTST pump is 135 litres per hour and supports 300 bhp at standard pressure

* Bosch 040 pump is 235 litres per hour and supports 520 bhp at 73.5 PSI

[Sydneykid]

Hi gtstii, if you have a swirl pot that the fuel returns into, then you can have fuel heating problems. If it returns into the main fuel tank, then I wouldn't worry.

I have heard of (not experienced) problems with very large fuel pumps when the fuel pressure regulator and the fuel lines are not big enough to bypass all of fuel that is not required by the injectors. This can lead to overfueling and premature aging of the fuel pump itself. So I would make sure that the fuel pressure regulator is a large enough and upgrade the return lines to the tank.

Hope that helps

[gtstii]

thanks a lot for that - always helpful !

I have been trying to select a fuel pump for the past week and need something for 200rwkw, so will select something which can support up to around 250rwkw to allow for future mods.

The thing is, I have spoken to a few diff. places and have been getting SOOOOOOOOOOOOO much different info, here goes (long one):

- I like the Walbro pumps because they are quieter, smaller and cheaper but I have read on SAU that their flow rates are specified at 0 pressure and that they do not actually support 500Hp.

Then a couple of tuners have told me that they sell walbro 500hp pumps by the truckload and haven't had problems with them!

- A bosch pump sounds like a good, reliable option but I know that they are noisier and require a bit of stuffing around to fit.

I would look at something like a bosch 910 or 975 and wanted it to be fit in the tank and this is done/recommended by a few tuners but then a tuner in Melb. told me that they wouldn't do this as these pumps are designed as external pumps and he wouldn't "risk" putting them in the tank.

He also says that b/c these are external that they should have a small pre-pump supplying fuel to them at pressure instead of having to suck up their own fuel in the tank.

Also, bosch did not recommend installing them in tank b/c they are too big.

- I spoke to Petroject's Melbourne office(www.petroject.com.au) and they recommend a pump which they have picked especially for use in skylines and wrx's.

He says that the bosch pumps require too much stuffing around to fit and that they have a pump which has a 50mm OD and fits straight into the std bracket and is a high flow unit that will flow 220l/hr (@2.5bar) for $305 - but it isn't a brand name pump, in fact he told me that the pump has no brand? :confused:

Can anyone shed some light on this!! :confused:

I need help to decide

[Sydneykid]

Hu gtstii, I only use standard Nissan pumps (GTST, GTR or Z32) and Bosch Motorsport pumps. So I can't comment on any other brands.

As for noise, I have found from experience that if you mount a Bosch pump properly in the tank they don't make much more noise than a standard GTR pump, ie; with the standard insulation, decently secured and not touching the tank anywhere.

Every loud pump I have seen has been poorly installed, with no vibration insulation, loose clamps and touching the bottom of the tank.

There are Bosch pumps that are designed to be mounted in the tank and there are some that are designed to be mounted externally. However most of them now are designed do both. My local Repco store has the Bosch catalogue with all the possibilities listed, I can only suggest you try yours.

As for not wanting to risk mounting them in tank, well from memory....

Mercedes Benz and Lamborghini use 910's

Ferrari and Porsche use the 975's

Audi use 040's

SAAB use 945's and 953's

They all seem to thinks it's OK.

Hope that helps some more

[gtstii]

thanks man............ and are the 975's in the porsches in tank?

[benm]

I had my Bosch 040 mounted intank in the same bracket as the standard GTS-t fuel pump, cost me $340 fitted.

[gtstii]

how loud is it and how much power will an 040 support?

[benm]

Well for my car to start now I have to turn my ignition on for 5sec first, then pump the pedal as i turn to key otherwise it just sits and churns.

During that 5sec I can hear the pump switch on and then after 5sec it clicks off but thats only if I dont have my aircon on or my stereo on otherwise I cant hear it. The -only- time I can hear the pump is that first 5sec, cant hear it when sitting at lights etc etc.

The standard R33 GTS-t supports 300bhp which is ~180rwkw (by my calculations).

The Bosch 040 supports 520bhp which is ~310rwkw.

The Bosch 910 supports 450bhp which is ~268rwkw

If you plan to have 250rwkw sometime in the next 12-18mths i'd be getting a pump that does atleast 280rwkw, you don't want a pump thats working 100% all the time.

[JimX]

- I like the Walbro pumps because they are quieter, smaller and cheaper but I have read on SAU that their flow rates are specified at 0 pressure and that they do not actually support 500Hp.

Then a couple of tuners have told me that they sell walbro 500hp pumps by the truckload and haven't had problems with them!

How many of those cars were running 500hp though? At a guess I would say absolutely none. Steve (I think) did a big write up on the Walbro pump awhile ago, if he (or the true author I've forgotten) can remember where the original thread about it was, it would be an interesting read.

My main concern with the Walbro pump is it doesn't like pressure too much, which would give plenty of concern if you wanted to fit a rising rate regulator. Even if you had a mildly modded Skyline of around 350-400hp, you would likely be on the edge of the Walbro's limits. If you decide to get one then be careful.

One (unnamed) Sydney workshop tried to sell me a Walbro at full retail price ($400) and offered to buy my unused 044 from me for less than his trade price ($200 or something?!). The reason being he said that my car wouldn't need the extra pumping capacity of the 044, and I would save around an hour's labour plus some money on extra fittings needed for the 044. So I was going to pay around $300 for the "privilege" of "upgrading" my 044 to a Walbro. In the end I'm glad I did the research and found out what a gyp that would have been, and I fit the 044 myself for $60 worth of parts. A nice way to save $240.

Edit: I realise that time is money and even though it took me around 4 hours to fit myself, my post-tax income for 4 hours is still far less than what I'd be shelling out to the workshop for 2 hours @$80/hour. And now that I know what I'm doing I can fit one now in far less than 4 hours.

[gtstii]

thanks for the advice JimX, I have read your post in the past and this is what first got me investigating.

I have spoken to a few more people and heres what I've been told:

- I know A LOT of people here fit bosch pumps in tank but Bosch have advised me that they recommend against this as all but two of the bosch pumps are designed to be external pumps (sydneykid: porsche/ferrari etc use them, but externally)

You can look at the bosch motorsports catalogue by following the links on www.bosch.com.au and here you can see that the only two bosch pumps which are specified as interanl pumps are the 040 and the 023.

I did a bit more research on the walbro pumps and the advantage of them is that they are new technology whereas most of the bosch pumps have been around for 20-30 years.

The Walbro's have their own sound insulation and they are available in a size which fits straight into the std factory bracket, they are also specified as an in-tank pump!

They come in 4 versions:

1. 190l/hr

2. 190l/hr (high pressure)

3. 250l/hr

4. 250l/hr (high pressure)

Anyway, I was worried about their flow rate capacities under pressure and have been assured by petroject that the 250l/hr pump will still flow 220l/hr at 2.5 bar which will be heaps for my application.

I then did my own research and found a site that has a table of all the walbro pump flow rates at diff. pressures (in gal/hr) I converted this to l/hr and found that the 250l/hr high pressure walbro pumpseems to have heaps of capacity at all sorts of pressure (even when compared to the bosch flow rates)

check out this site for the walbro pump table: http://www.autoperformanceengineering.com/

(click on fuel pumps - in tank)

Remember: This is all from advice I have been given by a number of different sources!

[JimX]

That's the first I've heard of a high pressure version of a Walbro. Maybe they copped a lot of flak for not being able to supply high pressure so they made new versions. If those figures are correct, then it may be worthwhile getting a high pressure Walbro.

But try to find out from an independant source if they are telling the truth or not first.

[gtstii]

well, thats what I'm saying - I was told by petroject of the flow rates of the walbro's, even at a bit of pressure and did some research and found that table on www.autoperformanceengineering.com and it backed up what they said.

these guys are good too cos they have service vans driving all around, all you have to do is call them and they deliver it straight to you

[BigDatto]

Hi gtsii,

if you can, get the Oct '03 backissue of Fast Fours. They have a very informative & detailed 6 page tech story on fuel systems, with independent views from a few different EFI specialists, includingPetro-Ject. Yes they certainly seem to know their sh!t.

Also you can find walbro 255's on ebay for USD$85 + shipping USD$10. about AUD$124 on your doorstep. (go you aussie dollar !) What price have you been quoted locally ?

I need a pump too - but I'll wait up to 2 wks if the saving is worthwhile !

hope this adds,

G

[Sydneykid]

Hi guys, let me quote from ..........

http://www.autoperformanceengineering.com/

"These pumps flow 255 ltr/hr at 40 psi"

Now a quote from www.bosch.com.au

"Bosch 910 pump is 200 litres per hour at 73.5 PSI"

Notice the difference here.....

The way I see it is the Walbro pump is OK for an N/A engine that runs 40 psi fuel pressure total. But not OK for a turbo engine that has to run 40 psi fuel pressure above the boost level ie; boost = 20 psi + 40 psi = 60 psi.

The Bosch pumps rated at 73.5 psi, haves plenty of capacity ie; can run boost up to 73.5 - 40 = 33.5 psi.

If you have a rising rate fuel pressure regulator (to increase the injector flow) then you need this sort of capacity even more.

Yeh I know Walbro have a high pressure version, but it's only rated at 50 psi, which is OK if you only want 10 psi of boost. Note the specification of the high pressure version, FPT012, for the Supra turbo which from memory runs 10 psi boost standard. If you rate that pump at 73.5 psi (same as the Bosch) their table shows around 150 litres per hour.

Now if only we could convince Walbro to make a 73.5 psi rated pump at 300 litres per hour that costs $US85. That would really get those Bosch prices down.

Hope that all makes sense and I haven't missed anything.

[gtstii]

after a bit of further research, I've decided that the Walbro's aren't bad but I might go for a bosch in the end.

After all the advice I have received, I'm now thinking of going for a Bosch 040 pump. The reason for this is that this is one of only 2 Bosch pumps which are designed as in tank pumps as i said earlier.

Bosch and a couple of other people don't recommend using their other (external) pumps internally and I have heard of a few people having very noisy bosch pumps. If you have a look at bosch's efi tech catalogue on their site, it states (and I quote):

Title: Noisy External Fuel Pumps

"Many fuel pump noise issues are relates to cavitation caused by insufficient fuel flow to the pump from the fuel tank. Keep in mind that external "Roller Cell" design fuel pumps are not designed to "draw" fuel from the tank. Vehicle design usually ensures that either the fuel pump is mounted low enough to be gravity fed, or a "Pre-Pump" or "Lift Pump" is fitted into the fuel tank of the vehicle.

When a fuel pump is to be replaced it is important to ensure adequate supply of fuel to the main pump exists. Details on how to check this is detailed in the article "EFI Fuel Pressure Testing Procedures"

Important Note - Fuel Pumps that fail due to cavitation/fuel starvation caused by insufficient clean fuel supply are not covered by Bosch warranty"

(catalogue found under: www.bosch.com.au, then follow the following links - automotive replacement parts and accesories - engine management components - technical articles, page 3)

This ties in with recommendations made to me by Bosch when i spoke to them and also by a tuner in Melb. as I mentioned in a previous post above:

(quote) "He also says that b/c these are external that they should have a small pre-pump supplying fuel to them at pressure instead of having to suck up their own fuel in the tank"

Again, I don't pretend to be an expert, I'm just trying to put out there all of the info i've been told, if you dont agree - let me know!

More to think about!!

[Warpspeed]

Sydneykid is spot on with his comments about the higher pressure requirements of a turbo engine (as usual).

But another thought comes to mind. If you leave the stock pump in the tank, and fit an external pump in series (Bosch or Walbro), then the pressure capability is going to be much higher than either pump by itself. So although a Walbro might start to droop in flow at high pressure, it might be well up to the job if mounted externally in addition to the existing pump.

What I like to do, is run an airline via a pressure regulator from the workshop compressed air supply to the fuel pressure regulator on the fuel rail. You can then dial up say 20 psi "boost" and fool the fuel system into thinking the boost is actually there.

You can then measure the return fuel flow at that "boost" and see how your fuel pump and lines are coping. You can also plot fuel flow versus "boost" and get a pretty good idea of how good the whole fuel system is handling the flow.

If you have six 550cc injectors, I would like to see a comfortable margin above 6 x 550cc (3.3 L/min) of fuel flow at maximum boost pressure. This is not difficult to do, and well worth the trouble.

[Sydneykid]

Hi gtstii, a couple of real world examples might help here.

I had an R32 GTR with a Bosch 044 mounted in the tank, it made a lot of noise. Even when the tank was full! Think about that, the ultimate gravity feed, 60 litres, all of it above the pump inlet. Plus it had all that fluid around it to stop the noise getting out and it still made a bloody racket.

It made noise because it had no insulation (rubber) between the pump body and the bracket. It was also mounted too low and the filter was resting heavily on the floor of the tank.

So I fitted a standard Skyline rubber (modified a bit) and lifted the pump up off the floor. Bingo, no more noise. Even when the tank was empty it made less noise than it used to when the tank was full.

I can give you three other similar examples, with an R32 GTST and an R33 GTST. I have never personally had a Bosch fuel pump mounted in a Skyline tank make, what I consider, to be excessive noise.

Now I am not knocking the Bosch engineers, what they told you and what is written is absolutely true. But it is not the WHOLE truth, you have to ask specific questions to get the whole truth. Plus they are dealing with all cars, not all of which have the fuel tank mounted and insulated as well as a Skyline's.

In the race GTST we have a GTR pump as the lifter to the surge tank and a Bosch 044 supplying the fuel to the engine. It is solidly mounted to the boot floor, has braided lines and an inline filter all bracketed to the floor and it makes a huge racket. Even with my helmet on and at full noise I can hear the thing rattle away when the surge tank is empty. It makes a good safety warning.

Previously we had 2 X GTR pumps mounted the same way and they made much less noise.

But this year I have a low fuel pressure warning built into the dash, so I am going to rubber mount it and the ancillaries to stop that damn noise.

Hope that helps some more

[JimX]

SK, what's a "standard Skyline rubber"? I imagine anything that fit the standard pump isn't going to fit on the 044 without modification.

[GTR-Ben]

I have a question about fuel pumps etc thats confusing me a bit..

Have a GTR here that seized the fuel pump. Pulled it out and it looked like a stock pump.

This car runs a T88 @ 1.5bar, fuel pressure sits at over 3.5bar..

I replaced it with a stock GTR fuel pump and it still holds this pressure at the above boost..

The car runs low 11's with no traction etc. Will run 10's for sure. Will be running it on the dyno soon.

The fuel pump wiring has been changed with larger wires etc.

To run the times and to have the pull this car does.. it is putting out over 600HP.. how can it do this with the stock pump running around 60psi? Does rewiring the pump help somehow?