nscason Posted January 19, 2007 Share Posted January 19, 2007 Ok, i have a 77 with all kinds of bolt ons. i am running the stock motor(n/a), big bore tb, zxt injectors cold air intake, header, cran cams xr3000... and so on and so on. my question is, besides fuel consumption what is the difference from running 30 to 60 psi? i had a problem a while back. my fpr went out. there was a hole in the diaphragm. gas was coming out of the vacuum port. i have a palnet fuel rail with a gauge. before that fpr went out it was running at 30 psi. i had an extra zxt fpr that i put on and it now runs at 60 psi. i dunno, i think that the car seems to like it more. i am in the process of putting in all kinds of aftermarket fuel stuff. the new fpr is adj from 30 to 100 psi. can anyone give me some good info on the difference from running the pressure at the stock 30 on up? no one that i have talked to where i live seems to really know. if any one can shed some light on this for me that would be great. thanks. Quote Link to comment Share on other sites More sharing options...
getZ Posted January 19, 2007 Share Posted January 19, 2007 there was an article I read a while back in one of my magazines and one of the guys from TPI (tuned port specialities) prefered a higher pressure for better fuel atomization. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted January 19, 2007 Share Posted January 19, 2007 Your injectors and pump determine the pressure you should be running at. Older EV1 style Bosch injectors are really only designed for one operating pressure, (ambient + ) 3 bar. The later EV6 style injectors have apparently far superior spray pattern (atomization) but good luck getting one of those. Your pump comes into it when you consider that it has to be capable of pushing hard enough to generate the pressure you want. I wouldn't think getting an average EFI fuel pump and setting the reg to 100psi would do many good things for the longevity of the pump. Of course, you could always go some Bosch motorsport products, pump (no, not an 044) and injectors.. they're offical rating is ``>8bar''. Dave Quote Link to comment Share on other sites More sharing options...
nscason Posted January 19, 2007 Author Share Posted January 19, 2007 to be honest i never intended on pushing my fpr to 100 psi. that would be asking for trouble. i do understand that doing that cant be good for my stock pump. the highest that i would be thinking of going would be around 70 to 75 psi. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 21, 2007 Share Posted January 21, 2007 Stock fuel pump deadheads at 60psi. So you will have pressure, just no flow to the injectors. The internal relief lifts at that point... Stay to the 45psi WOT manifold referenced signal. Makes pulsewidths longer for better control of idle, and shorter for better resolution at full load. You can also trim the injector capacity somewhat using a middle of the road pressure, allowing for a +/- 10% enrichment or leaning of the fuel mix by simple pressure adjustments while tuning. Hundreds of thousands, if not millions of car out there running at 3bar. Why reinvent the wheel? Quote Link to comment Share on other sites More sharing options...
nscason Posted January 21, 2007 Author Share Posted January 21, 2007 what exactly is 3bar? ive seen it on this site but don't know what it means. as soon as i get my aftermarket fuel system all plumbed up ill back the pressure down to 45psi. until then there's nothing i can do about the 60 psi that i have now. im using a zxt fpr only because the stock one took a crap. Quote Link to comment Share on other sites More sharing options...
mikeatrpi Posted January 22, 2007 Share Posted January 22, 2007 1 bar = 14.5 psi. A bar is another unit of pressure. Quote Link to comment Share on other sites More sharing options...
nscason Posted January 22, 2007 Author Share Posted January 22, 2007 ah ill try my best to remember that number. thanks. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 22, 2007 Share Posted January 22, 2007 The ZXT FPR will not regulate to 60 psi, it regulates to far less than that. Sounds like you have a restricted return line, and you simply are running on your internal relief valve... Eventually your pump will either overheat or simply burn out. Quote Link to comment Share on other sites More sharing options...
linluv84 Posted January 22, 2007 Share Posted January 22, 2007 If you run the fuel pressure too high, you can cause the injectors to not open properly. This would make tuning really interesting... Quote Link to comment Share on other sites More sharing options...
nscason Posted January 22, 2007 Author Share Posted January 22, 2007 thats the kind of thing that i have been wondering. every single injector that my car had clogged up or stopped working. the guy i bought it from got injectors off some junker car. i replaced them with what autozone said where for MY car but they were for a zxt. a completely different injector. i did notice this right away, but im not the kind to argue when new ones were under $50. the Cherokee i used to drive they were well over $15- for new ones. and if the zxt fpr that i have isnt supposed to be at 60 psi what should it be? is the clogged return line maybe what killed the stock fpr? i am going to replace the fuel system with -8 an line and alum 5/16 tubing. and yes i know that 5/16 is closer to -6 an. it will be easier to upgrade the tubing later than all the -6 an i would have to down the road. is there anybody that thinks -8 is going overboard in size or is it reasonable for eventually having a monster under the hood. i did fugue on going and getting an aftermarket pump if and when the stock one goes out. any body have any ideas on a good one that wont cost a small fortune? Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 23, 2007 Share Posted January 23, 2007 somewhere around 36 psi at idle, and 40-42psi at WOT (sensor line off the FPR at idle), after you go onto boost, the pressure will stabilize at Boost+WOT pressure, so at 10psi boost, you will have 50-52psi fuel pressure. From that, you see that people boosting much more than 12psi are running really close to deadheading the pump. Given there IS a pressure drop from the pump to the front of the car (even in the ZX!), what you read at the fuel rail may be a much as 5psi LOWER than what is at the pump!!! Larger lines help...but there is a thing as overkill. For high pressure lines, the flow they can support is pretty outrageous. It's not like you only have 3psi to push the stuff through there as in Carburetted Applications... Quote Link to comment Share on other sites More sharing options...
nscason Posted January 23, 2007 Author Share Posted January 23, 2007 once i get the extra fittings that i need im going to plumb up the rest of my system. i purchased alum 5/16 tubing. i eventually want Hp in the range of 400 to 500 Hp. that is a few years down the line though. should i put on the new line that i have or go bigger with the numbers that im eventually going to go for? i do have to use adapters to go from the 5/16 to the -8 an line that i have. i also am going to get an after market fuel pump the moment min goes out. is there any reason that i shouldn't use alum line for the main and return lines? im just trying to see if im wasting my money or not. thanks for the pressure numbers ill try to see what the problem is this week. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 24, 2007 Share Posted January 24, 2007 I used .035 Wall T304L Stainless Steel.... But then again, I get surplus 20 foot sticks from completed jobs for free, so what else would I use? LOL Quote Link to comment Share on other sites More sharing options...
endurorider Posted February 13, 2007 Share Posted February 13, 2007 1 Bar is 14.5 psi or 1 atmoshere at sea level. I would run fuel pressure at the stock level. Too much fuel pressure will cause you to run to rich. Basically your blowing the valve in the injector open. if your engine likes the excessive fuel pressure. I would suspect a vaccum leak and the added fuel is covering it up. We had a car in the shop that was driving us nuts because the fuel trims were running -15% or so and could find nothing wrong, until we checked the fuel pressure and found it was at 75 psi when it should have been at 40 psi running. Oh check your pressure running not just turning on the key. The fuel pressure regulator in the pump was defective and we replaced it under warr. If your running an aftermarket injector, I would follow there instuction or call there tech line. Being that your in ca and you drive a 1977 your still subject to california smog program so have those carb numbers ready. Quote Link to comment Share on other sites More sharing options...
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