QUESTION TO THE MAPPERS regarding fuel pump.
18 March 2011, 12:25 PM
#1
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QUESTION TO THE MAPPERS regarding fuel pump.
Hi. My car: V2 STI 96 with following mods:
- Major_Sarcasm CHIP (boost raised to 1.1bar)
- 100 cels Sports Cat downpipe and decatted centre section
- K&N 57i IK
- NGK PFR7B's spark plugs
- standard size injectors (380cc)
A couple of months ago I bought a WALBRO 255 fuel pump and now I finally got some time to fit it but... By fitting uprated fuel pump will cause overfueling or it will run fine ? I've read a few threads on here and other forums and some people say that it will be fine and others say that will cause overfueling. What should I do ?
To FIT or not to FIT ? :-)
Thank You
- Major_Sarcasm CHIP (boost raised to 1.1bar)
- 100 cels Sports Cat downpipe and decatted centre section
- K&N 57i IK
- NGK PFR7B's spark plugs
- standard size injectors (380cc)
A couple of months ago I bought a WALBRO 255 fuel pump and now I finally got some time to fit it but... By fitting uprated fuel pump will cause overfueling or it will run fine ? I've read a few threads on here and other forums and some people say that it will be fine and others say that will cause overfueling. What should I do ?
To FIT or not to FIT ? :-)
Thank You
18 March 2011, 12:30 PM
#2
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I'm not a mapper but it's the fuel pressure reg that controls the pressure at the injectors and unless your old pump was really knackered (tech term) then the new pump shouldn't make any difference to the pressure at the injectors.
18 March 2011, 12:42 PM
#3
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Thanks mate. That's exactly what I was told by Mark (Lateral Performance) when purchasing this pump. In my opinion my car runs ok, so don't think that my standard FP is knackered or something. But as I said I've got the new one and would like to fit it.
Oh well, I can always change it back if not running fine.
Oh well, I can always change it back if not running fine.
18 March 2011, 01:26 PM
#4
It's normally suggested to use an aftermarket fuel pressure regulator when fitting a higher pressure / flow fuel pump to classics, as the OEM fuel reg can be overcome and allow over fuelling due to the higher fuel pressure.
If you have an AFR gauge you can monitor the fuelling.
Many threads on here about it, and fitting the pump.
Pain to keep changing the pump, you can always easily add a FPR if needed after the pump swap.
If you have an AFR gauge you can monitor the fuelling.
Many threads on here about it, and fitting the pump.
Pain to keep changing the pump, you can always easily add a FPR if needed after the pump swap.
18 March 2011, 03:35 PM
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^^^ +1. And like you have been told, the pump doesnt control the flow of fuel. I am running an uprated pump and have no problems. Fit it and forget about it mate, it will be fine.
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18 March 2011, 11:57 PM
#12
Engine Specialist
I read Stu's article as saying that uprating the pressure of the fuel system has a negative effect unless all other related systems are corrected to suit.
An uprated pump will not directly effect the state of tune UNLESS the original pump is not able to keep up with current demand, but the map has been modified to suite a weakness in the fuel system by increasing the injector duty.
In my opinion a renewed fuel pump prior to any mapping modifications is a common sense safety modification, especially on a car of over 10 years old. When a car is remapped to a higher boost level the fuel pressure regulator will increase the demand from the fuel pump to keep the fuel flow at a constant pressure within the manifold.
Walbros and such like are higher flow pumps, which essentially means they will 'max out', (100% duty) at a much higher flow rate than the standard alternative, (dependant on car and model).
Some ecus allow the mapper to view fuel pump duty, some dont, so sometimes the injectors will have to be run at a much higher duty cycle because the pump might not be able to supply what it should have if it wasn't worn. This then presents the problem of the map working perfectly for now, but as the pump wears further it will lean out. If it is caught prior to failure of the engine then a new pump can be fitted, but since the old pump was weak, the new one will now be supplying more and making it run rich! Remap time again! You see the issue with assuming your pump would be ok.
That said, I wouldn't insist on a pump change unless it's a very old car, or the pump duty I deem to be too high when remapping.
Graham
An uprated pump will not directly effect the state of tune UNLESS the original pump is not able to keep up with current demand, but the map has been modified to suite a weakness in the fuel system by increasing the injector duty.
In my opinion a renewed fuel pump prior to any mapping modifications is a common sense safety modification, especially on a car of over 10 years old. When a car is remapped to a higher boost level the fuel pressure regulator will increase the demand from the fuel pump to keep the fuel flow at a constant pressure within the manifold.
Walbros and such like are higher flow pumps, which essentially means they will 'max out', (100% duty) at a much higher flow rate than the standard alternative, (dependant on car and model).
Some ecus allow the mapper to view fuel pump duty, some dont, so sometimes the injectors will have to be run at a much higher duty cycle because the pump might not be able to supply what it should have if it wasn't worn. This then presents the problem of the map working perfectly for now, but as the pump wears further it will lean out. If it is caught prior to failure of the engine then a new pump can be fitted, but since the old pump was weak, the new one will now be supplying more and making it run rich! Remap time again! You see the issue with assuming your pump would be ok.
That said, I wouldn't insist on a pump change unless it's a very old car, or the pump duty I deem to be too high when remapping.
Graham
19 March 2011, 01:50 AM
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Graham,
So, according to fact that my car is running higher boost than standard, it will be better if I'll fit the high flow pump (Walbro255) right ? Sorry for that but I'm VERY confused now.
Cheers
So, according to fact that my car is running higher boost than standard, it will be better if I'll fit the high flow pump (Walbro255) right ? Sorry for that but I'm VERY confused now.
Cheers
Last edited by ScoobyForLife27; 19 March 2011 at 02:04 AM.
19 March 2011, 08:13 AM
#16
Engine Specialist
You may well be ok with your current fuel pump, but given the age of the car I would not hesitate in changing for a Walbro, especially considering they are on £70.
Hope that helps,
Graham
Hope that helps,
Graham
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