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745i fuel/pressure readings - need feefback
tritterbrewHi folks, I'm learning and trying to tackle fuel mixture/idle/boost issues. I need some feedback on my readings - thanks in advance! '84 745i w/ 186K - very good condition (I think) and most of the fuel, ignition, fuel injection, wiring, etc. has been replaced w/in the past five years. The only change from stock is running a rising rate pressure regulator (at stock setting) and modified chip with wastegate vac. line still attached - max 6 psi boost. From cold start: Engine idle - fuel at 30 psi, vac at 20 in. hg Pull off vac from fuel regulator and pressure goes to 40 psi While driving, fuel psi goes from 30 at idle, 40 at 0 in. HG and 50 at 6 psi boost Car runs mostly lean but if I kick down I get a rich mixture - I've put the CO screw to the bottom and next I'm adjusting the AFM once I rule out pressure issues From warm start - ambient temp. 80 deg. and hot engine Idle fuel pressure 25 psi, vac at idle 15 in. hg Fuel pressure at 0 in. hg is 35 psi Fuel pressure at 6 psi. boost is 45 - 50 psi I've noticed that the needle on the fuel pressure gauge fluctuates about 5-10 psi very rapidly, particularly when under acceleration. Is this normal? I also find that warm idle is much worse than cold idle and I'm not sure why the vac. is different, could this indicate a vac. leak that only shows up when the engine is hot? Please advise with any feedback on these readings. I don't know if these are normal. If they aren't, please advise what you think might be the next step? Steve C., if you are out there, I sent you back an email last night with an update - thanks for your continued help! Cheers and happy Mom's day to any moms out there. Ted R. '84 745i
Jon 86 745 MSTed, The fuel pressures sound about right. The 20 in of vacuum sound high unless you are idling above 900 rpm. With a stock fuel pressure regulator you should be at 40 lbs above ambeiant pressure. Example would be my car idles at 900 rpm. I have 16 inches of vacuum. The math would be 40-16=24 psi at idle. If you remove the vacuum hose you should see the maximum rise in the regulator. Second who's chip are you using? What are the fuel mapping rates? Is the Motronic fuel mixture control knob set at zero? If not this could be the cause of rough or poor idle and lean or rich running conditions at midrange. This knob should be set a Zero as it cannot compenstate for any poor fuel mapping that the chip may be giving. How are you checking for Fuel Air Ratio. If you are using a low quality gauge that breakes down the spectrum into only 8 or 10 LED's then you cannot expect to adjust the system correctly. You should also be sure that the gauge is calibrated correctly by using a calibrated voltage meter. Once you put a chip into your Motronic that is not stock then you open up a Pandoras box of problems that could be future issues. Just be sure that what you use is tried and proven to work as advertised. Anything short of that is asking for trouble. The chip maker should be able to tell you what his chip does and why it does it. Just my .02 cents worth. Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts
tritterbrewJon, Thanks for the update. The chip came from Steve C. and it's the same one being used by a number of 745i folks out there. If I understand your explanation, you should be running about 24 psi fuel pressure at idle? This is quite a bit lower than what I'm running and I made sure that the rising-rate reg. matched the stock regulator at idle... Since I'm running lean and it seems that I have higher pressure than you, could this mean that I've got clogged fuel injectors? I guess the best way to tell is to send them off to RCENG? Also, you said that there should be a diff. of 40 psi between vac. and fuel pressure. When I'm at 0 vac. I do run at 40 psi fuel pressure. The problem is that when I'm at 15 vac. I'm not running at 25 psi fuel... I assume that the 40 diff. also applies to boost? If you are running at 16 psi boost, does that mean your fuel pressure is about 56 psi? Finally, is it normal to see the fuel pressure rapidly (the needle is a blur) fluctuate about 5-10 psi while driving? I hope that this discussion is helpful to others. If not, I can take it offline and just post the findings on this board? Cheers, Ted R. '84 745i "Fraulein"
Jon 86 745 MSQuestion of running lean first! Did you check the Motronic to see if the Fuel Quality Control (FQC) was set a Zero? This is the first place we must start! Second question of fuel pressure regulator: The stock fuel regulator will not run enough fuel pressure to Achive 16 psi of boost with out running CATASTROFICLY LEAN! Meaning Death to your engine. This is where an FMU comes into play. At 16 psi of boost you will need about 85 psi of fuel pressure with stock injectors and the Team 745i.com Chip. Our chip changes the injector timing pulse length the achive a fuel charge to the engine no mater what the boost pressure or the engine timing. I have no idea what your chip does but I would sure ask!! I would bet that if you look at the (FQC) setting it has been changed to a postion that incresses the fuel flow and retards the timing. This is why the rough idle, lean at cruse and rich at throttle up. YOU CAN NOT ACHIVE THE AMOUT OF FUEL NEED TO RUN THE SYSTEM SAFELY WITH THE FQC SETTING AND THE FUEL REGULATOR YOU HAVE!!!! This is the reason for the Stock regulator and the FMU system we use! I do not want to appear like I am shouting but you are creating a scenerio for distruction!! Some of you guys amaze me. You go out and do these things to your car without reguard to what is going on inside the power plant. As much as we have talked on this subject on this board and the other board and you still do not ask the right questions before you jump in! Ted I am not picking on you. I hope that anything I and others have posted here will help you in your endever to achive more HP. I just hate to see you destroy your toy before you get to benefit from the great output the engine has to offer. Sorry for the ranting just my .02 cents worth. Ted feel free to call me any time if I can help. 800 476 2285 (work) 228 219 9390 (Cell) Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts
JensI like your comment, I also know of 3-who well lets just say don't use this chip any more, because of IDLE issue and more............. Sincerely Jens
tritterbrewJon, Thank you for your input. Ted R.
tritterbrewJon, At first, I wasn't going to address your rant since it is difficult to do without sounding overly defensive. The comment "you guys amaze me" amazes me! I'm not an idiot and I thought I made it clear from my earlier posts that I'm trying to get everything set before I start increasing the boost over stock. I do have a FMU installed and the fuel mixture setting on the Motronic is at zero. The mixture gauge is accurate since I've tested it against my DVM. I realize that asking you guys for help without knowing the details of my setup is unfair. I will get things straightened out and report my results for other newbies on the board. Cheers, Ted '84 745i
scottieTed, you are in the right direction. I think Jon's comments are in good spirit and aimed specifically at protecting you and your engine, since there have been a few mishaps in the 745i world in the past due to lean running at high boost. Expensive mistake and we all felt the pain. I have Steve C's chip and I have a good idle...well as good as these big 6 is going to get. My car runs very strong with it at 6-12 lbs. (This is with California Chevron 91 ) I have yet to try the 115 octane racing fuel that Don and Victor have obtained locally. They say it is great. Don's car reportedly is pulling smooth and strong at 15 lbs. Scottie Sharpe San Jose CA Discussion Board SYSOP 84 745i 85 535i
dnliiicorrection Scottie- 17psi today and like silk!
Jon 86 745 MSTed the reference to "some of you guys amaze me" was not aimed directly at you.I simply refer to the fact that there are people out there trying to achive things and have no idea on how there car works. Please infer my appologies to the fact that you did not answer my questions in the responce post about the Meter and FQC switch. Now for you being an Idiot I cannot and will not call you that, nor did I infer that to you in any such factor. I myself did not rant as you called it but I will admit that I did preach. And I will continue to do so. As I said earlier you can destroy an engine by being lean. You cannot set your system by using an 8 or 10 led Fuel Mixture Gauge. These gauges do not have the circutry need to brake down the 1 volt spectrum that is used with the O2 sensor. If your digital meter does not break down beyond .1 (tenths) of a volt then it is not accurate enough for gauge testing. I myself use a Fluke model 87 that I send out twice a year for calibration and certification. If that sounds anal then I am an anal kind of guy. I guess thats the engineer in me. You asked a question and I gave you my answer even though it's an opinion. It was free. Take it for what it's worth. You can ask any of the guys that I have helped with their cars how I have worked with them to achive what they are looking for. If they bought anything from the "Team" then they got a complete understanding of what they bought and exactly how to set it up and how it worked. Even if they never bought anything or got something from somewhere else I still extended any help possiable to them! I extended this same offer to you by giving you my phone numbers one of which would not have cost you one cent. Now for your Issues on how to get your car running correctly I again extend the warmest of invitations for you to call me. To write everything down on this board would take me hours as this reply has done. I cannot type worth a damn. Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts
cliffoi have tryed to adjust the tension spring in the airflow meter as suggested on the 745i.com site, and noticed abetter response off idle. i have had the car on a dyno yesterday, and the results showed a massive lean out from idle to the boost threshhold, after which the air/fuel ratio was spot on. the guys at the workshop pulled the cap of the afm, and spent about 1/2 an hour adjusting things. the end result was correct mixtures from idle all the way to 5500 rpm. i was told that due to the long path that the air has to travel, the older the afm unit,the less well it will work. What im trying to say is that a proper workshop has the correct measuring equipment and knowledge to fix things, and avoid things like burnt/holed pistons. she idles beautifully now,and pulls like a train.can i ask who steve c is, and does he have a website to visit.
JensThats why I'm trying to find and make a Mass flow meter CLiffo :) Sincerely Jens
Afshin-SwitzerlandJens, A question please, would it also be avalable for the L-Jet 745i ? If so, count me already as one of your first buyers .... ! Regards, Afshin. 1982 745i
Jon 86 745 MSThis AFM thing has been a hot topic among the Big Boost Group guys on a daily basis. It would be the best thing to do and get rid of the thing. Cliffo, I commend you on your effort to get it right. Money well spent!! Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts
Kristjanlittlebit offtopic but Jon has a point. I´ve been reading roadfly board about couple of years, although I cant understand everything you guys are talking about. But I have learned lot about 745 and turbo engine from Jon, Jens and others. Thank you. I know that when I have the chip and the wastegate mod - I will not try to run higher boost before I have double checked all systems. I wish I could speak a little more english. Then I could express myself better. Kristjan proud to be 745 owner. BMW 745 `85 full stock Edited by - Kristjan on May 14 2002 06:28:19
Jon 86 745 MSThere is nothing wrong with your English!! Jon Jacobs 86 745i (Das Rocket) 16 psi+ Boost with Team WWW.745i.com Performance Parts
cellguruAnd there is nothing wrong with your typing Jon :-)
ra0507Jon, I don't know about the FQC. Please advise what it is and how I adjust it. I have purchased an air mass sensor replacement for the air flow meter but will not install it until after I get things working correctly with the AFM. Rick
JensRICK!!!!!!!!!!!! Be very careful VERY careful, not if you bought the one from BMP make sure they toulk the 5Volt cut of out, otherwise you will have huge problem, remember the one you got is for an 735 which only sensis up to 5Volts ours goes higher. Sincerely Jens
ra0507Jens, Thanks for the input. Mine is, I am sure, the same one, but it came from "Split Second". I will check with them to ensure that it is not limited to 5-volt. They did ask if I had the 5V or 7V version. What is the correct answer? Rick
Bob745_DallasRick, When I spoke with Split Second about 1-1/2 - 2 years ago they claimed not to have an acceptable MAF conversion unit for the 745. In fact, they asked if anyone on the Left coast might be willing to let them experiment on a 745. Sometime later John Stein informed me that he had a Split Second unit which did not work correctly with the 745. My belief is that Split Second learned from John's application that they still had work to do to be able to handle the 745. John claims to be nearing the point where he will be trying again to make the unit work. Maybe you should communicate directly with him to see what his issues were before installing the unit. If it were me, I'd place a call to Split Second just to make sure that the unit is fit for your application. I'd love to hear that it is. My order would be placed immediately.
Jon 86 745 MSBob I would be next in line!!! We need to get on John Stein to get going. I will see John the weekend of the 15th. I hope to give everyone a first hand report. Jon Jacobs 86 745i (Die Rakete) 16 psi+ Boost with Team WWW.745i.com Performance Parts