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Discussion Starter · #1 ·
I sourced a uprated fuel pump (Walpro 255 lph)and one of the Maptun authorised dealers said it would be a straight swap, well it isn't on a 1992 Carlsson
The pump is shorter in length and also smaller in diameter....however I cut a spare old pump open and slotted the new pump into the empty casing to make it fit the housing. I just need to solder the wires together now and sort out the high pressure pipework. Does anyone know how to soften the plastic pipe correctly??
Next is I need to fit, or I'm advised, to fit a adjustable fuel regulator. IIRC the standard regulator is set to 3 bar, I have just removed a spare fuel rail and am going to modify it to allow an after market adjustable regulator. Do I need to go for a rising rate one 1:1.7 or will a 1:1 be sufficent....and will I need to do anything with the regulator type thing on the return line?
I'm thinging of buying this one, will it be suitable or am I better off getting a FSE type?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...me=STRK:MEWA:IT
 

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Discussion Starter · #2 ·
I;ve just found this info...would this type be better...definitely easy to fit though!

NEW RED SERIES RISING RATE TURBO FUEL PRESSURE REGULATOR. for ALL turbocharged SAABs from 1985 and later which includes all 900, 9000, 9-3 and 9-5! This regulator will also work in conjunction with ANY vehicle in need of additional fuel support (the engine must already be factory turbocharged and should already have a rail type fuel pressure regulator)

Fuel delivery is by far the most important update necessary when attempting to move more air into your engine. Any time the amount of air entering the engine is altered, whether through more turbocharger boost levels(APC upgrade, manual boost controller, etc), new cams, a ported cylinder head, etc., the need for additional fuel delivery will become a factor to reach a 14 to 1 fuel/air ratio (a bit richer for turbo owners). The correct mixture will go a long way in creating more power and reducing headaches. The SWEDISH DYNAMICS Red Series Rising Rate Fuel Pressure Regulator is a fully adjustable component that runs in line with your stock regulator to give you all the fuel pressure you'll need up to 100psi. The beauty of this BELL ENGINEERING system is the fact that you can continue to update fuel delivery parameters as additional upgrades are made to the engine…making this the last FPR you'll ever need.

Other brands of "rail" type replacement fuel pressure regulators offer an adjustment via spring loaded check valve and an increase of fuel delivery. Unfortunately, the adjustment will increase or decrease spring preload under all (full engine load, no load, idle, etc.) engine conditions and won't allow for easy tailoring. A higher full load adjustment will always bring about a higher idle fuel deliveries and thus brings multiple problems in conjunction with larger fuel injectors or additional fuel components. In these cases, an enrichened adjustment can bring about a rough idle and low rpm engine "bog" and a reduced performance.

Our Red Series Rising Rate Fuel Pressure Regulator is active only under forced induction or turbocharger boost levels and will allow for a much greater range of adjustment over the competition. In short, because our regulator runs in-line (after and in the return line) with the factory fuel pressure regulator at the fuel rail, the adjustment will allow for fuel pressures up to the capacity of the fuel pump while under boost (100-120 psi!) while still allowing for only 35 psi fuel rail pressures at idle (dependant on OEM or factory SAAB rail regulator 2.5,3.0,etc). The fact that our RRFPR runs on the factory return line will also allow for mounting anywhere under the hood (no bulky aftermarket fuel pressure regulator requiring mounting on the fuel rail!).
 

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this sounds like the ideal compromise unless you are going for a re-map
I guess at high boost when your set up "runs off the map" your fuel delivery system is maxed out
the injectors are at 100% and they have nowhere to go...hence engine leans out melts spark plugs ...you know the score...
Now with this set up depending on when the rising rate kicks in (adjustable?) it will allow the fuel system to have more capacity when you need it
downsides ?
fuel pump has to be able to deliver pressure as well as volume

sounds good tho...
 

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If you are talking about softening the end of the fuel line at the pump/tank end there is a tool to press it on. I didn't know about it so I boiled water and put the plastic end in it, repeted several times, pushed really hard and finally got a good fit.
 

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I'm not convinced about RRFPRs... not on a good adaptive system anyway. Surely the right way is to map the fuelling properly and simply make sure there's enough pressure/flow to meet the demands of the (larger) injectors.

Some brands of RRFPRs are known for drifting from their static setting over time too, which is far from ideal!

Anyway I have a spare FSE RRFPR which you're welcome to try to see if it works.
 

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Discussion Starter · #6 ·
Okay, as I see it the standard fuel reg drops the fuel pump supply pressure to 3 bar to the fuel rail. As the fuel pump is a positive displacement pump it will supply ever increasing pressure against a dead head until it stalls, thus in the fuel tank the pipework is configured to allow a constant bleed thru a orifice back to the tank. Also on the return side of the rail there is a regulator type gadget (auto bleed system??) which must be set to relieve at 3 bar also??
As the standard boost pressures of the car is around 1 bar the differential across the injectors is then 2 bar but as I plan to run 2 bar boost this differential drops to 1 bar....am I seeing this correctly??
So do I need a 1:1 supply regulator set at 4 bar to keep the 2 bar differential and if this is so what about the return regulator thing...this would keep dumping the extra pressure back to the tank...thats why the Red Series regulator seems ideal. However as the new fuel pump can supply all the fuel I need do I just fit bigger injectors and leave the standard regulators alone? I'm just trying to understand the fueling concept before I decide what to do....anyone explain it for me a what set up would be best bearing in mind I'm pre trionic
 

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The reason that fuel regs have a feed of the inlet manifold pressure connected to them is in order for them to maintain the differential pressure across the regulators a at the desired value, otherwise the ECU can't deliver the correct amount of fuel- it does this by knowing what the differential pressure is and the flow rate of the injectors.

Thus, if your boost is at 1 bar with a 3 bar regulator, the absolute pressure in the fuel rail will be 4 bar, but the differential pressure across the injectors will be 3 bar.


If you lower the flow resistance (thus increasing the flow rate for a given pressure) of the injectors, you will deliver more fuel for a set time of opening.
 

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Discussion Starter · #8 ·
Also on the return side of the rail there is a regulator type gadget (auto bleed system??) which must be set to relieve at 3 bar also??
 [/b]
This appears to do nothing as I can blow and suck thru it with no resistance. Thought it might be some sort of bleed valve so filled it with water and could still blow and suck...none the wiser.

Bubbles, thanx for that, completely forgot about the vacuum pipe to the manifold...brain working overtime!
 

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A few thoughts
the pressure regulator works downstream of the rail restricting flow
the "new" one works further downstream restricting the flow more when it is instructed to do so..
(pressure switch ?)
this will be on a rising rate to maintain the "pressure over boost" on one level but as it is rising rate it will provide an ever increasing pressure diferential over boost
now the thing that controls this will be the lambda sensor and as long as the ecu does not get confused over the huge air flow rates it may keep things in control
It may prove a tad interesting setting the thing up
sounds as if you will need a session on a rolling road to do this...
 
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