Jake Posted July 4, 2006 Share Posted July 4, 2006 (6sp VVTi) I'm checking my car over before it goes for mapping tomorrow. It's got an Aeromotive FPR with gauge. How do I check what the fuel pressure has been set to? Do you just look at the gauge while the car is ticking over? Stock fuel pressure is 36psi right? Is that at tickover? I presume stock pressure is the best setting to use given my setup? (Motec m600, 800cc injectors, stock rail, stock fuel lines, stock fuel filter, no FPD) Anything else worth checking? Thanks Quote Link to comment Share on other sites More sharing options...
SimonB Posted July 4, 2006 Share Posted July 4, 2006 Get a bit of wire and bridge the +B and FP terminals in the diagnostics port under the bonnet. Then turn on the ignition. That will run the fuel pump and allow you to check/reset the static pressure (static because the injectors aren't opening). Pressure when idling will be less as it's pulling a vacuum. Quote Link to comment Share on other sites More sharing options...
Jake Posted July 4, 2006 Author Share Posted July 4, 2006 Pressure when idling will be less as it's pulling a vacuum. LESS? It's running 50psi at tickover at the moment. I'll go check. Thanks Si Quote Link to comment Share on other sites More sharing options...
Jake Posted July 4, 2006 Author Share Posted July 4, 2006 Get a bit of wire and bridge the +B and FP terminals in the diagnostics port under the bonnet.Damn, there's no contact in the FP terminal (VVTi engined Supras are different) Quote Link to comment Share on other sites More sharing options...
supradibbs Posted July 4, 2006 Share Posted July 4, 2006 not sure if i read that right jake but for your injector size you should be running more than 36psi at idle thats stock pressure example am running 650s at 40-42 psi mate off mine running 1000cc is running over 50psi Quote Link to comment Share on other sites More sharing options...
Jake Posted July 4, 2006 Author Share Posted July 4, 2006 for your injector size you should be running more than 36psi at idleI don't understand, why would bigger injectors need more than stock pressure? Quote Link to comment Share on other sites More sharing options...
LeeT Posted July 4, 2006 Share Posted July 4, 2006 I don't understand, why would bigger injectors need more than stock pressure? you don't. you can raise the pressure to compensate for having smaller injectors. never heard of waynes theory before. My car runs at 36psi at tickover and when i pull the vac lline from the regulator its around 43psi which is about right. not that it matters but im on 850's Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 4, 2006 Share Posted July 4, 2006 I don't understand, why would bigger injectors need more than stock pressure? You don't. You should run them at the pressure they've been tested. If you run them at anything else then they're not flowing the amount of fuel that they're claimed to flow. Otherwise you could ramp the pressures up mega high and run the 440cc's at enough pressure to flow 1600cc (if the injectors could handle it that is!) Quote Link to comment Share on other sites More sharing options...
Jake Posted July 4, 2006 Author Share Posted July 4, 2006 OK. So should I be concerned that mine is running 50psi at idle? How can I check the static fuel pressure? I'm sure I'm not the only VVTi running an aftermarket FPR. Quote Link to comment Share on other sites More sharing options...
SimonB Posted July 4, 2006 Share Posted July 4, 2006 Ah, forgot it's a VVTi, don't know how to do the fuel pump diagnostic on those. You could pull the pressure hose off the regulator and start the car, it won't be as accurate as the injectors will be opening and closing but near enough. Quote Link to comment Share on other sites More sharing options...
LeeT Posted July 4, 2006 Share Posted July 4, 2006 OK. So should I be concerned that mine is running 50psi at idle? How can I check the static fuel pressure? I'm sure I'm not the only VVTi running an aftermarket FPR. i found the static fuel pressure was the same as just pulling the vac line. 50psi doesnt sound right. i think you really need to speak to someone like Terry or Mig Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 4, 2006 Share Posted July 4, 2006 OK. So should I be concerned that mine is running 50psi at idle? How can I check the static fuel pressure? I'm sure I'm not the only VVTi running an aftermarket FPR. Not sure. I don't know what the base-pressure for the VVTI is, or even what size injectors it has. Basically unless you have some kind of fuel computer to lean the fuel back out at the low end, you don't need to adjust the fuel pressure. A lot of people fit an adjustable FPR, increase the fuel pressures so that the AFR's are OK when you've got a lot of boost on at the top end. However it means you end up running rich at the bottom. The stock ECU will try to sort it out as much as it can with the aid of the O2 sensor, but it can only do so much... So you need to find out primarily what the base pressure *should* be. Quote Link to comment Share on other sites More sharing options...
Jake Posted July 4, 2006 Author Share Posted July 4, 2006 Thinking about it, does it really matter what the fuel pressure is set to (within reason)? I mean, as long as it's mapped properly at that pressure, and the fuel pressure doesn't change, it'll be right - won't it? Quote Link to comment Share on other sites More sharing options...
Alex Posted July 4, 2006 Share Posted July 4, 2006 Stock is 42psi...it's not unheard of to map using a higher static fuel pressure...I believe I know of a couple out there...if the injectors can handle more pressure then there's no issue... Your MoTeC is more than capable of maintaining a good idle despite big injectors and higher pressure than stock. In short if the car is mapped for it it's absolutely fine and it will leave you with more head room (lower duty cycles). Quote Link to comment Share on other sites More sharing options...
Alex Posted July 4, 2006 Share Posted July 4, 2006 And just to confirm with the VVTI there's no way to prime the system like with the old spec...so it's get it running and disconnect the vac hose...unless the motec has the capability to fire the fuel pump up without the engine running...but then you'd need access to the map to do that... Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 4, 2006 Share Posted July 4, 2006 Thinking about it, does it really matter what the fuel pressure is set to (within reason)? I mean, as long as it's mapped properly at that pressure, and the fuel pressure doesn't change, it'll be right - won't it? Just to confrm what Alex has said. If the car has been mapped at 50psi, then that's what it should be left at. Quote Link to comment Share on other sites More sharing options...
Clarkey Posted July 4, 2006 Share Posted July 4, 2006 Stock is 42psi... I've heard that 36psi or 40psi is stock. Confusing .. Quote Link to comment Share on other sites More sharing options...
TLicense Posted July 4, 2006 Share Posted July 4, 2006 The workshop manual says that the pressure at idle on a UK model is between 33-40psi. Quote Link to comment Share on other sites More sharing options...
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