Alex Posted March 21, 2003 Share Posted March 21, 2003 How do you run a fuel pump at 13.5volts, when your battery/electrical system is only rated at 12? What would I need to change to be able to run the pump at a higher voltage? NB: I don't want to do the 12v pump mod - this is a seperate question. Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 21, 2003 Share Posted March 21, 2003 Get a 1.5v AA cell battery and wire it up in series Only kidding. Actually, I reckon when the motor is running you will be putting about 13.5V through your car anyway. Car electrics=12V is a bit of an over simplification AFAIK. Quote Link to comment Share on other sites More sharing options...
Nathan Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Darren Blake Actually, I reckon when the motor is running you will be putting about 13.5V through your car anyway. Car electrics=12V is a bit of an over simplification AFAIK. Agreed. Nathan TDI PLC Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted March 21, 2003 Share Posted March 21, 2003 Alex, mine hits just over 14v when running according to the Autronic. Quote Link to comment Share on other sites More sharing options...
Adam W Posted March 21, 2003 Share Posted March 21, 2003 13.8 on mine. Quote Link to comment Share on other sites More sharing options...
Adam W Posted March 21, 2003 Share Posted March 21, 2003 I just thought - why not start your car up and then get a multimeter on the pump connections in the boot, you can see exactly what it's getting then (don't disconnect the pump connector to do this though . . . !) Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 21, 2003 Share Posted March 21, 2003 The thing to remember is that even though you may have 13.5v at the front of the car you may not see that at the fuel pump in the rear. The reason being is because it's quite a long run for the cables and our pumps draw quite a lot of current so any resistance in that run (or particularly the earth) will have an adverse effect on the voltage seen. To be 100% you really need to measure the voltage as close to the pump as possible (and measure it across the terminals) and if you do see a lower than desired voltage check all connections, particularly the earth ones. Quote Link to comment Share on other sites More sharing options...
Nathan Posted March 21, 2003 Share Posted March 21, 2003 Good point Martin and the UK pump does draw a huge amount of current relative to it's flow abilities. The Walbros use much less current whilst being a more efficient pump. So much so that many can run twin Walbros on the stock wiring. Try that with 2 UK pumps and you will not only have red-hot wires you will probably trip the fuse and/or fuel pump ECU. Nathan TDI PLC Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted March 21, 2003 Share Posted March 21, 2003 I've just measured mine... (Sad, I know), I'm getting 13.88 measured directly across the battery with the engine running, and 13.56 at the pump and the pump ECU, (Walbro pump). I suppose if you wanted to be ultra fussy, you could use a relay to make a direct connection to the battery but I doubt 0.3 volts would make any significant defference anyway. Quote Link to comment Share on other sites More sharing options...
Nathan Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Matt Harwood and 13.56 at the pump and the pump ECU, (Walbro pump). Yep. Just what we found. Nathan TDI PLC Quote Link to comment Share on other sites More sharing options...
Alex Posted March 21, 2003 Author Share Posted March 21, 2003 So...are we all agreed that if all is working properly our pumps run at ~13.5v which means the 13.5v ratings should be the ones we are interested in? Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted March 21, 2003 Share Posted March 21, 2003 Personally, I'd say yes. Unless there is a high resistance supply problem. - Easily checked with a multimeter. Quote Link to comment Share on other sites More sharing options...
Alex Posted March 21, 2003 Author Share Posted March 21, 2003 Well this has been a surprise, thanks for the quick responses. I will multimeter mine...and possibly upgrade any wiring which is sub-standard. So where did they get the "12v fuel pump mod" come from Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted March 21, 2003 Share Posted March 21, 2003 i thought it was 14.4 vplts when car was running. if you that concerned you could always relocate the batterey to boot like the skylines have. what sort of price are the twin walbro pumps and is it overkill for stock turbos. was looking at the power house racing fuel system, that has 2 walbro fuel pumps think it was a stage 2 fuel kit. what have you got planned alex? Quote Link to comment Share on other sites More sharing options...
Alex Posted March 21, 2003 Author Share Posted March 21, 2003 I am getting a pump...to help fill a hole in the fueling at the top of the rev range, that's all Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted March 21, 2003 Share Posted March 21, 2003 12 volt is a very general term for car electrics. The 12v mod basically means stopping the pumps ecu from dropping to the lower voltage (9v approx - 8.7 when I measured mine at idle). The 12v mod as described on mkiv.com wires the pump to 12v all the time the ignition is on... I didn't like the idea of that much so I wired mine slightly differently. I've wired mine through a 5-15 volt relay that makes the pump see 12v, (or maximum available voltage), when the engines actually running. * If that doesn't make much sense, feel free to call me tomorrow - 01622 683044 * Just waiting for Pete Betts to pop along and explain how to make it more simple... Quote Link to comment Share on other sites More sharing options...
Terminator Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Matt Harwood The 12v mod as described on mkiv.com wires the pump to 12v all the time the ignition is on... I didn't like the idea of that much so I wired mine slightly differently. I've wired mine through a 5-15 volt relay that makes the pump see 12v, (or maximum available voltage), when the engines actually running. That sounds like a very good idea Matt. Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Alex Holdroyd So where did they get the "12v fuel pump mod" come from As Matt say's it's just an arbitrary term. Do you want to be the one to rename it to the "12.8v to 14v fuel pump mod" ? Quote Link to comment Share on other sites More sharing options...
Terminator Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Martin F As Matt say's it's just an arbitrary term. Do you want to be the one to rename it to the "12.8v to 14v fuel pump mod" ? Perhaps " full voltage fuel pump mod" would be better. Quote Link to comment Share on other sites More sharing options...
Alex Posted March 22, 2003 Author Share Posted March 22, 2003 I'm not adverse to running better cabling to the back from the battery.... if I was to get some should I use 70A Car Battery Cable, 40A In Car Ent cabling, or just 20-30A Twin Power Cable? All of those are listed in the Maplin Catalogue.... Matt, Is there any chance you could document your mod for an FAQ/idiot like me? .......I think the plug on the battery is going to need an overhaul too!! Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted March 22, 2003 Share Posted March 22, 2003 No problem Alex, I'll have a look at the wiring colours I've used and post it up later. Personally, I wouldn't bother running new cables, just do the wiring conversion at the pumps ecu. Unless you're meter gives you low readings at the ecu. When measureing the voltage, ideally, get someone to hold the RPM over 1000 to make sure the alternator is at full strength. The figures may/will fluctuate slightly. Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 25, 2003 Share Posted March 25, 2003 Interesting product, Fuel Pump Booster. http://www.msdignition.com/fuel_8.htm Quote Link to comment Share on other sites More sharing options...
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