Fuel pump upgrade?

[Ewan]

I am in the process of having Jon Mitchell Garage modify my 250 bhp Turbo SE to about the 320 bhp mark. So far they have fitted their performance head, the 3 bar FPR, a dual port wastegate and manual boost controller, the new chip set and a boost gauge. De-cat pipes are also being fitted to improve breathing. The latest suggestion is that the fuel pump be upgraded also. Does anybody know how necessary this is, given my current power aims? Clearly I don't want to starve the poor thing of fuel, I just don't know at what point the standard fuel pump gives up. Any advice from fellow modded Turbo owners?

 

[TTM]

To me it sounds like the standard injectors will be more limiting than the original fuel pump, unless you forgot to mention you are also having the injectors upgraded?

We are running Walbro GSL392 fuel pumps on significantly modified 2.5L and 3.0L engines and we haven't had any issue so far.

 

[944 man]

Not withstanding what Thom has said, Id suggest that you always replace the fuel pump. Even if its able to comfortably deliver the fuel required; what will happen if it starts to fail on boost?

Let me answer for you: the mixture will lean out and before you even realise either youll hole one or more pistons, or the detonation will cause a catastrophic big end bearing failure. In either scenario youll be lucky to retain much more than the cylinder head and maybe conrods - worst case: nothing but the head (and thatll needs extensive flushing).

In order to establish whether the OEM Bosch is up to the job, youll need to know how many litres per hour it can pump. If its comfortably over your peak flow requirement then a new Bosch part will suffice; if not then Id look at Warlboro first.


Simon

 

[chrisg]

+1 for 944 man's advice, before you start 'leaning' on the engine, replacing the fuel pump even just a 'standard' turbo one is a good idea - after all the youngest the pump will be is 20 + years. I had an issue with my fuel pump starting to fail at full boost several years ago at a Silverstone GP track evening.

I replaced it but it had already done damage, resulting in a burnt exhaust valve and engine rebuild 4 months later.....

 

[Ewan]

It appears that a new fuel pump may be in order then.

Any input from you other modded turbo owners - Suffolk944, 944Turbo, Simkin911, Frenchy, barks944, Lowtimer, GPF, MarkK, Driver944, DivineE and others - have you lot all fitted upgraded fuel pumps, are you all "gambling" on detonation by using the standard item?

 

[simkin911]

Ewan, I am new to Turbo ownership and not all at experienced with these matters. The Turbo was modified by RPM for the previous owner a couple of years ago. There is no mention of a fuel pump upgrade. It sounds sensible for you though from the postings above.

 

[sawood12]

I went round this when modding my turbo (now barks') and I cannot remember how many hp's the original fuel pump is good for but it is more than the 280ish HP I achieved before handing the car over to Tom, so I concluded it wasn't necessary. I think 300 bhp ish is where you need to start looking for a flow-rate increase.

However, as with everything with a modded car, if you were doing things properly you'd replace every component in the system as as they are suddenly, after 20yrs or so and 100k ish miles, going to be having a harder life and ongoing reliability has to be a consideration. Having said that, most of us don't have an unlimited pot of cash to dive into to do proper jobs of it, therefore we are all carrying risk and in my view given the reliability of the OEM pump ( I've never heard of one failing) then unless you're approaching the max flow rate of the unit then you'll probably get away with continuing to run it. A failing pump could lead to the problems described above whether your car is modded or not, so who knows what the MTBF is of these things, but I'd guess it is many millions of hours.

However in your case since you're reaching in excess of 300+bhp then I'd say that a fuel pump upgrade is needed to one that delivers a higher flow rate.

 

[944 man]

Warlbro pumps cost about £100 - in a number of ways this is a bargain and itll be one of the best one hundred poundses that youll have spent! []

 

[Frenchy]

Nope not got one on mine yet, but when funds allow i will, obviously recommended but had no issues so far nor have i heard of any with others that run the same spec, you decide ?

 

[robwright]

Me neither Mark. In fact as with all chipped turbos my car overfuels on boost and my AFR shows accordingly. My pump seems more than man enough. I am sub 300 though and would consider an upgrade if I was looking for serious HP. Not that a sniff under 300 isn't serious lol []

 

[George Elliott]

Ewan, if you measure AFR, you will see a leaner reading if the pump is struggling, it will be at high revs for prolonged periods, in the upper gear ratio's, probably 4th and 5th. The injector duty cycle is highest at that point, and the flow will absorb the fuel pressure, and the FP is opposed by max boost in the manifold, so everythings against the pump.
If the AFR is good, then the pump must be good?
just my 2 penneth, and note, I do not have 3.0L project experience.
perhaps its a to be safe measure??
Good luck
George

 

[Frenchy]

A nice to have, though if funds allow go for it as it cannot do any harm, as previously posted going past 320 ish a must have.

 

[Diver944]

Same advice here, if you're around the 300bhp mark then the standard pump is fine and has some safety margin (if it's in good health). Once you start to go higher it's always about matching the fuel flow to the air flow and making sure you have enough spare capacity to avoid the catastrophic onset of running very lean. I have the Bosch Motorsport 044 pump in mine

 

[George Elliott]

what......only one of them Paul?

I thought 3.2T's had one per injector [] just to be safe of course!

George

 

[Diver944]

It's funny you mention that. I have heard of some cars running twin fuel pumps, one being a built in redundancy purely for safety reasons, but I suppose you have to draw a line somewhere []

 

[Lowtimer]

I'm on a standard fuel pump but I am only running 15 psi boost at the moment and it has headroom. However, although my car is low mileage I am always awayre o fthe age of various critical components and at some stage will change the pump rather than wait for it to wear out.

However it is all academic at the moment as the car is still in pieces at the body shop.

 

[Hilux]

I find myself in complete agreement with 944man who I would certainly listen too if I may say and also Paul (Diver944) who appreciates also the necessary diversity....................

If the pump and filter (and pipes to and from) are original and you`ve spend a tidy sum tuning the engine then especially in a Turbo`d car you really do not want to run lean. A 20 year old pump and filter are not the ideal if you think about it long and hard. The pump can fail and the filter if partially blocked will reduce (mask) the diversity of pressure built in by Porsche and the pump will be working harder anyway.

I would also check carefully all fuel pipes for condition and replace any flexible pipes with new and renew all clips - again as an insurance policy.

Total cost max £150 if you DIY but it depends on how much you consider the risk of your engine grenading.

Equally, if the injectors you are retaining are on or approaching their limits then you definitely want a pump that will deliver a consistent high head pressure. Two pumps are overkill but I can see why one might as excess pressure is simply bled back to the tank via the FPR. I would use a modern uprated pump such as Sytec or Walbro or Bosch (at least 6 bar for 3 bar at the rail I would say - a 50% diversity factor) but I dont know what the OEM pump max pressure rating was though?

The AFR may be fine, in fact it will be until the pump pressure drops if if it starts to fail. At high revs/max boost it only takes a second to lean out too much and melt pistons. Too quick for any sensors to react.

A good pump and pipes/clips (and equally a very good filter) is an insurance policy in my book

 

[944Turbo]

Bosch 044 as well, though there were no signs of the original not being up to it, seemed sensible.
Tony

 

[Diver944]

The price seems to have gone down since mine was fitted. A few places are selling it around the £150 mark at the moment

http://www.fuelpumpsonline.co.uk/bosch-044-fuel-injection-pump-0580254044-170-p.asp

 

[u63af]

Anyone know what banjo sizes we need for a 944 when buying a bosch 044?