Hi All, I managed to sort out a fuel pressure gauge at last, so last night I checked the system pressure coming out of the metering head. Turns out im running 4.4bar, and I believe the book spec is 4.5bar. From what i've read, a 1mm shim ups this by 0.6 bar, but i've got some 0.5mm shims that I can use for half that. Can anyone tell me what the optimum fuel pressure is for a 16v on K-Jet? I've got the WUR drilled ready to setup at 48PSI hot idle once i've set the system pressure up, as I understand the system pressure will increase the control pressure. Any advice appreciated
Book spec for nearly all K Jet cars is 5 bar. A 0.5mm shim (depending on the spring condition) should give you .75 bar pressure increase. A 0.1mm shim should give you about 0.15bar increase.
Looks like its running a good bit down on standard then, guess the spring must get weak with age. I'll try the 0.5mm shim and see where that takes me on the gauge. Any ideas on what differences increased fuel pressure will make to the running of the car apart from the fact it raises the control pressure?
The WUR is basically a restrictor but as the feed and control side of it is fed straight from the fuel pump and the pressure is then bled off to the return line, upping the system pressure will up the control pressure. If you were to just up the system pressure without adjusting the control pressure the system may run weak. However as your system pressure is below spec simply bringing it back to dead on book spec should just require a CO adjustment afterwards.
Thanks golden Im going to bring the system pressure back up, then adjust the WUR control pressure for the 48PSI at hot idle like the slealth racing mod. Once thats done, i'll throw it on the gas analyser and setup the CO. Noticed the 12v connection was broken on the WUR the other day, so I soldered it up with a new connector, now the performance has suffered. I guess the extra heat from the 12v connection has raised the control pressure more and the fueling is weaker Should be running spot on once i've set it up with the gauges anyway
I've had that before, guy couldn't work out why he'd never get more than 25mpg form a 1.6GTI. Should all be spot on once you've set everything back up. Just be vigilant for leaks. Once you've reset the system pressure anything that was a bit marginal could start leaking (cold start injector etc).
I somehow knew you would show up in this thread Hirdo I dont think there is any accurate way at all of getting 48PSI control pressure without using a gauge. The control pressure is adjusted by using the 4mm allen screw that is located behind the tamperproof brass cap on the back of the WUR. Adjusting the Fuel pressure also has an effect on the control pressure, as the WUR control pressure is dependant on the system pressure in the first place. Get yourself a guage and set it all up - a 0-100PSI one would be ideal, thats what im using.
Got it from here mate, its the 28 quid 0-7bar kit, its just a cheapo but it seems to work well. Had to make up a couple of pipes out of old 16v WUR hoses so I can run it inline while the engine is running. Its oil filled as well, seems pretty good quality. You get the inline fitting, jubilee clips, and some high pressure hose. Flusted - I read on the forum 5.4bar was a good pressure to run as well but wasnt sure whether it was right or not.
5.4 Bar is the maximum allowable system pressure. Remeber, upping the system pressure on a K Jet does not increase the ammount of fuel delivered at the injectors.
Have you checked fuel pump is getting is correct healthy supply of battery voltage? Quite common for it not to be the case with corroded terminals, alarm/immobilisers etc.. may explain reduced supply pressure.. just a thought. often overlooked
Is this something stealth would check if i had them rolling road tune my car? (sorry for small hijack)
Oh come on... How did you know that? eheheh But the problem is not the gauge! It's the way to control pressure, cause i don't want to tamper with the WUR myself, and around here, no one does that mod!!
Just mark where it is on the wur and adjust it till you get the 48psi you want.If it all goes wrong,turn it back to where you marked it.
I found out last night that the 4.4bar reading I was getting was actually the control pressure line! Thats 64PSI! Im geussing what happened was when I drilled the WUR, the drill went through the brass globe (its very thin), landed on top of the allen head and turned it (it seems very easy to turn). That explains the poor performance since I drilled it and fixed the broken 12V connector. Anyway, I adjusted it down to 48PSI hot idle - well impressed with the running of it now, the car is much more responsive and smoother, and pulls better right through the range. Idle has smoothed right out as well. I havent fiddled with the timing yet either. Cold running this morning was better than it ever has been too, car was much smoother. CO was right up at 3.6 on the analyser after setting it, took it back down to the usual 2.0 Didnt manage to read system pressure though - I was under the impression that the other line going to the WUR could be used for system pressure, but im getting a zero pressure reading on this line with the engine running. What line can I use for system pressure? Hidro - I seriously wouldnt go adjusting anything without a gas analyser and the gauge, as once you change one thing, it knocks everything else out as well.
Smithy you probably didn't hit the allen key with the drill it's probably just fixing the heater element supply. As far as measuring the system pressure it's done by conecting the gauge to the WUR supply line and then blocking the output (the Bosch test gauge has a valve on it to do this). This may seem odd but the pressure in the WUR supply line is limited by the pressure regulator in the metering head and so reads true system pressure. So you actually can use the same position to test system and control pressure but only if you have a gauge with a shut off valve in it. Smithy does your test kit look anything like this?
