Guest bastaad525 Posted August 11, 2004 Share Posted August 11, 2004 Cygnus - you have mentioned a couple times that you have set your RRFPR, to run at 45psi at full boost. I just wanted to clarify with you on that... are you saying that you have it set to add 3psi of fuel pressure to every 1psi of boost? And this is in addition to whatever fuel pressure increase is provided by the stock FPR yes? So all in all you're running somewhere in the 70-80psi range under full boost? I just want to be sure I'm reading that right... seems like an awfully high about of pressure to run. fl327 - now YOU stated that you were running 12psi of boost at 50psi of fuel pressure, also on stock EFI. I'm assuming you were running an adjustable, NON rising rate regulator, so increasing fuel pressure only 1psi per 1psi of boost? I'm also assuming you mean 50psi was the idle pressure? Or was that the max pressure it would hit at full boost? When you set it to 50psi was that with the engine idling and vacuum reference connected or disconnected? What FPR did you use? Did you adjust your AFM at all to compensate for the richer mixture? Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 11, 2004 Share Posted August 11, 2004 fl327 - now YOU stated that you were running 12psi of boost at 50psi of fuel pressure, also on stock EFI. I'm assuming you were running an adjustable, NON rising rate regulator, so increasing fuel pressure only 1psi per 1psi of boost? I'm also assuming you mean 50psi was the idle pressure? Or was that the max pressure it would hit at full boost? When you set it to 50psi was that with the engine idling and vacuum reference connected or disconnected? What FPR did you use? Did you adjust your AFM at all to compensate for the richer mixture? Yes that would be me. 50psi at idle, BG adjustable fuel pressure regulator, non rising rate (replaces factory regulator). At least 62psi fuel pressure at 12psi. With the vaccum disconnected I had 52-3 psi at idle. I have still to this day not opened up the AFM, I dont know why just havent had to I guess, not with stock injectors I guess. Its a good way to fine tune a bigger injector setup to get it to idle and also a good way to destroy a good tune-thus I leave it alone since I dont currently run a huge injector. This is with 20btdc initial timing with the 83ecu that likes 24btdc. I ran this combo thoROUGHly for about six months, and got used to it. Taken it beyond 6k rpm ALOT. Quote Link to comment Share on other sites More sharing options...
john kosmatka Posted August 12, 2004 Share Posted August 12, 2004 Len are you using stock injectors with that setup or a set from a different car, Im thinking that there stock since you didnt have to opent the afm, also what kinda 1/4 times have you been running on that setup. Thanks, John Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 12, 2004 Share Posted August 12, 2004 Really odd that you didn't need to adjust the AFM at all... 50psi of fuel pressure at idle should cause the car to run pretty rich on stock EFI... maybe not so rich that the O2 or whatever wont compensate for it I guess? Sux because I"m still not running the O2... even after I bought a brand new bosch sensor and installed it, the car would run worse with it hooked up, so I leave it disconnected. After my last dyno and wideband test, I may end up going with the cartech RRFPR afterall... still trying to decide. Originally I had been against the cartech, a lot of info and discussion I've had back and forth with guys on here, for and against. But now I kinda like the idea of having the cartech unit only affect fuel pressure on boost, meaning I wont have to fuff with the AFM or anything to keep the car running smooth off boost... But... I'm still debating between the cartech and the MSD non rising rate unit... the biggest point in the MSD unit's favor? It's only about $200 less I'm going to end up picking up one of them tommorow, either way. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 12, 2004 Share Posted August 12, 2004 On the cartech FMU, what range of adjustment does it have? what are the minimum and maximum rate of gain that it can do? After Sean73 posted some calculations for me, it looks like I"m gonna need to run about 65ish psi of max fuel pressure under max boost, which means I need the FMU to supply only about 2psi of fuel per 1psi of boost... I'm not sure but I think I remember reading the specs on that unit before, and the minimum gain it could do was like 3 or 5psi per psi of boost... way too much fuel for me. Checked the cartech website and they dont say what range it covers. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 12, 2004 Share Posted August 12, 2004 Im running stock sized injectors, really good reliable ones, but yes stock sized. Fuel system (pump, linesize, regulator, blah blah) on my car except for the injectors should support my goals of 280-300rwhp-kinda low I guess but ill be able to drive it alot and my next car will be faster. I wont touch the afm with the stock injectors-its probably the last thing I would do-just personal preference. I was all over the high 13 second range on street tires before I lost interest for the time being in 1/4, ill be back, but im in no rush. Times vary from a best of 13.77 to my average 13.9-14.1 thanx to a 2.21 avg 60ft from boiling the H rated 60series tires and a open diff that doesnt believe that its not an LSD coming out the hole! Im sure I run rich at idle, I run factory fuel system with no emissions devices except a pcv, I should expect to run rich at idle and I accept the compromise. Hp is least of my concerns at the moment, Im trying to get lsd and rear disk brakes mounted up, and then I want to straighten the body work side up. Turbo upgrade big injectors and new management would be next on the menu after the body is good and straight, then Im doing a V8. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 12, 2004 Share Posted August 12, 2004 Cartech/BEGI FMU 2022: A boost-reading FMU gradually "pinches off" the fuel return line as boost rises. By pinching off the return line totally, fuel pressure at the fuel rail increases to a maximum of the capability of the fuel pump. So, boost=return-line-pinch=fuel pressure rise. In the boost signal line that runs to the FMU there is a bleeder. The bleeder is adjustable. Wide open bleed, the FMU does NOT react to boost so the car runs stock fuel pressure based on the stock regulator. Close the bleeder all the way and the FMU fully pinches the return line when it gets boost to get MAX fuel pressure. What I do is leave the stock regulator intact to control fuel pressure in a stock way when not on boost. Then I pump my shop compressor up to 14psi and get the car idling. I connect the FMU boost feed line to the 14psi compressor and watch my fuel rail pressure. Then I adjust the FMU bleeder (onset) so that the rail gauge reads 45psi. With the Walbro, I can make it go as high as about 90psi. This does NOT gaurantee pressure at full throttle because if your fuel line is too small, you still may not get enough flow to maintain your FMU set fuel pressure. Summary: Engine Idle. FMU inline in the fuel return line, and connected to intake manifold for boost reference. Vacuum line is connected to stock regulator. Approximate-FUEL RAIL PRESSURES-at idle: IDLE FULL/VACUUM: 35psi IDLE/NO VACUUM: 40psi 14PSI BOOST TO FMU: 45psi (set by onset bleeder on FMU) The rate at which the fuel pressure goes from 40 to 45psi is linear with boost. Assuming fuel pump supply is adequate. Drawback of FMU.....Example: Reaching full boost at 3000rpm will lead to 45psi rail pressure which may be to rich for 3000rpm. FMU NOT RPM dependant. Neither is a RRFPR. whew...got all that? Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 12, 2004 Share Posted August 12, 2004 525 - a couple of questions... What size fuel feed and return lines are you running? You say that it runs like crap when you connect an O2? If you're currently not running any kind of O2, what signals your ECM to come out of limp mode and accept readings from the sensors like TPS position/HTS value and make adjustments to things like injector rate? Just curious. Thanks. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 12, 2004 Share Posted August 12, 2004 Cygnus... what you're describing doesn't make sense to me, as far as what your final fuel pressure gets up to. Even without the FMU, you should be seeing at LEAST a 1:1 pressure rise with each PSI of boost. So if at 0 vacuum your fuel pressure sits at 40psi (mine does exactly the same) at 14psi of boost you should be at 54psi of fuel pressure, just using the stock FPR. I verified this myself watching the pressure gauge on the dyno. I always get 1psi of fuel pressure per psi of boost. If I can't get away with running 52-53psi of pressure at 13 psi, I can't see how you're getting away with 45psi at 14. In my other thread a little ways down (the fuel injector size vs. hp rating post) Sean 73 did some math for me and figured out that you'd need fuel pressure at least in the 50's to support upwards of 200rwhp - 10psi of boost. Maybe I'm misunderstanding something here? Jersey - funny thing is, every ZX I've owned has run better w/o the o2 connected... *shrug* don't ask me why. The fuel feed is just the stock fuel feed on the 240, however big that is. For the return line I'm running it thru the metal line that used to go to the vapor tank, which I think is 1/4 inch. When I initially used the super tiny stock return line, fuel pressure shot up to like 80psi. Now it runs at about stock psi. With the MSD fuel pump and the stock fuel feed, the fuel pressure had no problems hitting 54psi on the dyno... of course, who's to say it was flowing enough and not causing my really weird O2 readings. The last time I dynoed though, O2 readings were VERY consistent with other dyno's I had seen run on very similiar setups, so I don't think the stock feed line is a restriction or at least it wasn't at that point (10psi boost, no I/C, 200rwhp). If I hook up the O2 sensor the idle gets noticeably rough, lots of sputtering and misfiring. This was before and after installing a brand new bosch unit. Not running the O2 does not keep the ECU from seeing signals from the other sensors. I don't use the TPS either, even after using a voltmeter to adjust it perfectly (goes open the second you breathe on the throttle), it's another sensor that makes the car run worse. Well all it affects is the idle... it smooths the idle out when I hook it up, but causes a little stumble every time it comes off idle, very annoying. So all it runs on as far as I know are the HTS, AFM and air temp sensor in the AFM. I'm pretty sure it reads signal from the HTS as if I disconnect that with the car fully warmed up and running it will go super rich and then die, disconnecting it with the car cold has no effect... not the most scientific method, I know With all these sensors disconnected the first couple times I dynoed I got a very typical A/F curve, compared to several other stock or near stock setups I had seen dynoed. A rich midrange, and a lean top end. All the O2 is affecting is my gas mileage, it makes it run a bit rich at idle and light load, but doesn't affect WOT operation. The TPS ONLY affects idle, with it disconnected, the motor just never goes into idle mode, so this also causes it to run a bit rich at idle (or is it a bit lean? I keep hearing differently). The car has always run smoother with these two sensors disconnected from day one, and I finally gave up on trying to diagnose why. After testing and replacing and adjusting, nothing worked. But, even in around town driving, I dont think I suffer for it, the car seems to run great. My gas mileage sux, at about 17-20mpgs, but that's about it. Reading my plugs, they don't ever show as running TOO rich though, just a little darker than ideal. Again, this has been the case with all three EFI Z's I've ever owned, and I've talked to others who've had similiar experiences. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 13, 2004 Share Posted August 13, 2004 Hmmm Bast. you got me thinking now about the stock fuel regulator. My listed rail fuel pressures were taken at idle in the garage. I simulate the 14 psi boost to the FMU by hooking up my compressor to the FMU. In my method, I am NOT feeding 14psi to the stock regulator. In fact, the stock regulator is still seeing vacuum when I do this test. Soooo you are right. I should pull the stock regulator vacuum line off the intake and feed the 14psi to BOTH the stock regulator and the FMU to see my true rail pressure effect. Thanks for paying attention Bast. On a side note: I did NOT think that the stock fuel pressure regulator was able to act upon boost anyhow. It is only a vacuum device, isnt it? I'll try to redo my setup and take new pressure readings this weekend....if the rain stops. Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 13, 2004 Share Posted August 13, 2004 I'm running 12 psi of boost with the Cartech FMU and I'm using stock 76 NA injectors and ECU. At 12 psi, I was runing 14.7 a/f ratio (dyno tested) with 70 psi of fuel pressure (too lean but 235hp at the wheels). I have recently increased the pressure to 85 psi and I'm finally making some black smoke out the exhaust. However, the biggest problem in make fuel pressure is finding a pumping system that can delivery high flow and high pressure at the same time. In all pumps, as the pressure goes up, flow goes down. In most cases, flow drops to almost nothing at 90 psi. An in-car flow pressure gauge will tell what is going on (get one). In my case, the stock pump could only make 55 psi under high flow conditions. Eventhough it would make 90 psi at idle when the return line was pinched closed. So setting the FMU higher did nothing! I needed more flow. If you install two pumps in-series (one pump feeds the other) then much higher pressures are obtainable. In fact, I use three pumps now! A low pressure pump to pull out of the tank then to a stock style high pressure pump (in the stock location) then to another high pressure pump which is mounted up front by the fuel filter. I can now (if needed) generate over 100 psi under high flow conditions!! However, two stock style, high pressure pumps should be enough to maintain 70 psi. MSD makes a big pancake type regulator that allows a lot of adjustment: (idle pressure, no vacuum pressure, and boost pressure ratio). I friend of mine uses one on his 78 turbo retro fit (stock NA ecu). He is using turbo injectors with an idle pressure of 15 psi, 20 psi no vacuum, and 50 psi at 12 psi of boost. This way he doesn't need all those stupid fuel pumps! The bigger injectors (24lb vs 17lb) help handle the flow requirements, not just more pressure. And the stock regulator is not used with this setup. But with all this said, an FMU is only a bandaid on a broken leg. We all need to get new programmable EFI's to do it right!!! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 13, 2004 Share Posted August 13, 2004 Cygnus - makes more sense now The stock regulator DEFINATELY reacts to boost, dyno verified with my own eyes. I run about 34 psi at idle with vacuum, 40psi with no vacuum, and on the dyno, full boost at 12psi, about 52 psi of fuel... it definately goes up with boost. Pyro - hard to make good assumptions for me, based on your experiences... I know N/A injectors are smaller than turbo ones, but I dont know by how much. I do know that 70 and 85psi fuel pressures are a lot... whereas, assuming my fuel injectors are flowing close to their rating (260cc) I know I can get the flow I need at about 65psi max (at full boost). I did find the graph that shows what my pump will flow at that pressure: You tell me if that's enough flow... I have no idea how to figure that out mathematically. I know the pump was rated to support some 400hp, whatever that's worth. I know a few other guys running this pump that are making more power than I, that's for sure. I do have the pump wired via relay directly to my battery charging circuit, so it should be getting max voltage. An FMU may just be a bandaid, but if it is than programmable EFI is some expensive surgery, and for those of use w/o the money, a bandaid is many times a perfectly fine alternative Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 13, 2004 Share Posted August 13, 2004 I recently installed those MSD pumps and I have seen those graphs. However, I don't think they flow as much as advertised. That is why I added another low pressure fuel pump. Go to RC engineering. There are a lot of formulas to calculate flow for injectors. For example: ((new pressure/old pressure)**1/2) x old flow rate = new flow rate so a 190 cc injector at 75 psi with flow the same as a 260 cc injector at 40 psi. (75/40)**1/2= 1.369, (**1/2 is square root) then 1.369 x 190 = 260 cc. But remember the manifold pressure! Injectors flow less in a manifold with positive pressure. 40 psi is really 30 psi under 10 pounds of boost so 75 turns into is 65 psi. Therefore, a 190 cc in a 10 psi boosted manifold with 75 psi of fuel pressure (65) flows like a 280cc injector with 40 psi (30). ((65/30)**1/2) x 190 = 280cc. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 15, 2004 Share Posted August 15, 2004 Ahh cool so the stock regulator does react to boost and it does so in a logical way. It keeps the same pressure difference across the injector nozzles at all times. So if boost goes up 1psi fuel goes up 1psi. Vey cool. Quote Link to comment Share on other sites More sharing options...
Kazuya1274 Posted August 16, 2004 Share Posted August 16, 2004 Pyro I am curious about this MSD fuel pressure riser. From what I am getting from your friends car, with this he can set the idle fuel pressure to 20 psi (which is less than stock), 0 vacuum is at 35 psi, and full boost is 55 psi? I wonder how it can "reduce" the fuel pressure at idle. I tried looking on MSD's website, and could only find part # 2222, which is a boost adjustable fpr (which I think takes the place of the stock one). If you can adjust this thing at 3 different points, it would help me out a lot becaue I have turbo injectors with the stock 81 ecu, and it tends to run rich at idle, as well as through the whole powerband at 7 psi (got a boost controller, just need to install it!). Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 16, 2004 Share Posted August 16, 2004 I'm not sure where he got it, but it is huge! About 4 inches diameter and 2 inches tall. It has three adjusting screws on it; one for idle pressure, one for low vacuum, and one for boost. He had to run 20 psi at idle because he is using a non-turbo ecu with turbo injectors. Do a search on the web and you should be able to find it. If not, i can get the part number from him. Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 16, 2004 Share Posted August 16, 2004 Sorry. I gave you the wrong information. The FMU is made by Vortec, part number VOR6X100-001. Summit sells them for 280.95. Quote Link to comment Share on other sites More sharing options...
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