onephatz Posted May 17, 2004 Share Posted May 17, 2004 I don't know if I just had some bad gas or weather the dyno more load than it usually sees running down the road, but the darn thing just didn't run right. with the wide band up the tail pipe, it showed a way lean condition under load. it started pinging an knocking and running like crap. funny thing is that after I left the dyno it ran great(still does). I'm running stock 280zxt fuel system stock injectors stock turbo front mount 3" exhaust greddy bov two fuel pumps I can only think of two things that would cause a this lean condition, 1. fuel pumps not pushing enough fuel 2. afm not reading correctly mainly because I've run techron thru the fuel system and have a new fuel filter and a good fuel pressure regulator(stock). am I mistaken or am I supposed to run the fuel pumps in parellel or series. me being a poor college student can't opt for a nice walbro so I am running a stock zxt pump and a stock z pump in parellel to get the extra flow needed. any ideas where I need to start thanks jesse btw. just lost to a sti last night (just 1 car length though) Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 17, 2004 Share Posted May 17, 2004 Well it would help to see how lean you were, how much boost you were running, what power it made, etc. I am not using a 2nd pump, and making about 260whp from it. The stock 190lph pump should be good for at least 300whp. I have run into situations on my ZXt where the injector plug will come lose, and cause me to run dead lean. I have stock injectors with an SDS EIC and 2x450cc DSM injectors. Quote Link to comment Share on other sites More sharing options...
onephatz Posted May 17, 2004 Author Share Posted May 17, 2004 Well it would help to see how lean you were' date=' how much boost you were running, what power it made, etc.[/quote'] under load and just as boost started to build it was running extremely lean, like 16:1 lean. right now the boost is set at 14psi. it does spike to around 16 but settles down to 14. I don't know how much power it was putting down because it wouldn't pull past 3000rpm. I looked at the computer and it said I only put down 35 hp for the amount of time it pulled. so....... jesse Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 17, 2004 Share Posted May 17, 2004 Definatly sounds like a fuel delivery problem. Perhaps a clogged/bad injector, or fuel pump issue. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 17, 2004 Share Posted May 17, 2004 Not knowing the flow and pressure numbers on the nissan pumps, I am just guessing, but I would imagine that the ZXT pump is the 'stronger' one, which would then make the 2nd pump irrelevent, and it may actually be hindering things. Fuel pressure gauge would be next on the list...... Tim Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 17, 2004 Share Posted May 17, 2004 I believe they are both 190lph. The fuel gauge would be a good idea. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted May 18, 2004 Share Posted May 18, 2004 Yep Tim had me sold on that one too when my new fuel pump immediately caused my car to run like crap... definately worth doing I think whenever you altered the stock fuel delivery system and even worth using on a bone stock system if it's having running problems you're trying to track down. You can pick up the stuff you need for an easy DIY under-hood fuel pressure gauge for about $15. here is a pic of mine... kinda hard to see, it's there in the lower right hand corner of the pic... but should be good enough for you to get an idea. Basically a few brass pieces to make a tee, then a sprinkler system pressure gauge (reads 0-100 or 0-200psi I forget). Works great. Quote Link to comment Share on other sites More sharing options...
onephatz Posted May 19, 2004 Author Share Posted May 19, 2004 when I installed the second fuel pump, at idle the one zxt pump would was pushing around 40psi. when I turn on the second fuel pump the pressure raised to about 45psi. I don't know what she is running when I drive her down the road but it can't be that much different I would think. I think that I may take the afm off tomarrow to see if everything is working good there. how would you be able to check to see if an injector is not firing correctly. would running a bottle of techron thru it help? am I wrong but isn't this system (stock turbo, stock injectors, stock fuel system) supposed to be able to put down at least 250hp with an intercooler at 14psi or so? AND not destroy itself. I suppose this would explain why it likes to run on the warm side just cruzin down the highway at 70mph. I don't think I am going to run it till I at least get some sort of solution conceived for this thing. I am suprised i haven't melted anything yet. jesse Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted May 19, 2004 Share Posted May 19, 2004 Stock turbo and injectors can support 250hp, but the stock ECU/AFM will not. The problem is in the limits of the airflow meter. The AFM's flap is fully open, under WOT, somewhere between 4000 and 5000rpm. After that point the ECU can no longer use the AFM as a source to measure airflow. Of course, the more boost you're running, the sooner the AFM 'maxes out' as well. At that point, I figure the factory ECU switches over to a default fuel map, using only RPM, intake air temp and probably head temp sensors to determine how much fuel to supply. Now, the ECU would only have been programmed to provide fuel for at the most 10psi of boost, as this is when the factory pop off valve would have vented (you DID leave that installed didn't you? ) so theoretically it would never have had to supply fuel for more boost than this. This is why every ZXT motor that gets dynoed w/o increased fuel pressure or bigger injectors runs lean above 4000-5000rpm, even as low as 8psi when intercooled, as you run leaner with an I/C installed. However, the AFM measures air fine up to that point, and this is why most air/fuel curves on the dyno will show very rich in the midrange, and then suddenly going lean when the AFM maxes out. If you aren't even running rich in the midrange, and as you stated are actually running THAT lean (16:1??? JEEZ) as soon as boost starts to build, I would think you have some other problem. If you're running 40-45psi of fuel pressure at idle with the vacuum line connected to the fuel pressure regulator, than that shouldn't be your problem. Most guys with adjustable FPR's running 10-15psi of boost set their fuel pressures in this range anyways. Stock idle pressure is supposed to only be about 30psi... so you've already got a healthy increase there. BUT... have you watched your fuel pressure on the dyno?? It's important to see what the fuel pressure is doing as the motor is revving and boost building under load. Maybe your FPR is bad and fuel pressure isn't rising with boost? Other possibilities... maybe something got worked loose in your fuel system and clogged the filter or something else.... the techron maybe worked some gunk loose? Replacing the fuel filter at this point would be cheap insurance. AFM might have been going screwy... any possibilty any water might have gotten on any connections or anything? Could be other electrical gremlins... man good luck hunting those down.... you might even consider having an electrical place test your wiring harness for shorts/breaks if you can't find any other possible cause. Very odd that it only did it on the dyno but be VERY careful until you find out why it did that or you might be looking to rebuild you're engine. Quote Link to comment Share on other sites More sharing options...
280zinsanity Posted May 19, 2004 Share Posted May 19, 2004 Jesse, your car runs warm because you have a small fan. The night I drove it, it ran warm, and it was like 50 outside. I bet your stock clutched fan pushed alot more air than that one... Quote Link to comment Share on other sites More sharing options...
onephatz Posted May 20, 2004 Author Share Posted May 20, 2004 ok let me see if I have this right. the stock computer/fuel system is only capable of of delivering 10psi worth of fuel in stock form. with the advent of higher fuel pressure(rrfpr) this problem can be bypassed fairly easily. besides those facts, there is proubly a problem with either a injector not firing correctly, clogged fuel lines, clogged injector, or afm issues. did i miss anything? you'll be happy to know that it was getting 14.7:1 idling though I'm going to be taking things apart tomarrow to find the culprit. I'll let you know. thanks jesse p.s. the fan is fine because 1. the fan doen't matter driving down the road at 55mph, and 2. idling for extended periods of time doesn't cause it to over heat. Quote Link to comment Share on other sites More sharing options...
280zinsanity Posted May 20, 2004 Share Posted May 20, 2004 sorry man, your correct. i know nothing. then i guess 4 different cars that i had fan issues that i fixed were something else. but whats funny is, they stopped overheating when i got an adequate fan on. what do i know. i didnt grow up around a shop. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted May 20, 2004 Share Posted May 20, 2004 ok let me see if I have this right. the stock computer/fuel system is only capable of of delivering 10psi worth of fuel in stock form. with the advent of higher fuel pressure(rrfpr) this problem can be bypassed fairly easily. That's pretty much how I understand it, and what has been demonstrated time and again by cars running stock or mostly stock turbo EFI setups on the dyno. It's not so much what it's 'capable' of, but rather, what it's been artificically limited to by a very conservative fuel map. The hp limit of injectors of course is theoretical just based on the amount of fuel they are rated to flow but the number should be accurate... one thing that no one has cleared up for me though... when you say the injectors can only support up to 250hp, is this WHEEL hp or CRANK hp? If its crank hp then of course that comes to more like 210-220 at the wheels... I really haven't seen anyone exceed those numbers on stock injectors on the dyno to know for sure either way. But I know that bone stock the fuel system always seems to limit itself to about or a little above 200rwhp, boost increases will bring up the torque and midrange, but top end hp wont go up much if at all because at that point the fuel just runs out. Increased fuel pressure is just a 'cheat' I really dont know how much more power it would allow, or how much extra pressure it would take to get there. Bigger injectors definately allow that limit to be crushed. with the advent of higher fuel pressure(rrfpr) this problem can be bypassed fairly easily. Stay away from the rising rate regulator, just get a regular, boost referenced regulator... rising rate will add fuel whenever there is boost present... not just on the top end which is where you really need it. Or do what someone else here did if you really want to use an RRFPR, use it with an adjustable one way valve (he used the grainger style valve that most of us use as boost controllers) to keep boost from affecting it until the level YOU specify (9psi is good)... but this will still hurt your mid rpm performance once full boost is achieved before the 4-5k rpm 'cutout' by the AFM. Better to just get a regular adjustable regulator, adjust the pressure up, and then tweak the AFM to lean out low and midrange. However, running 45psi at idle... you're really already just about where you would want to be anyways... I wouldn't mess with it at all. besides those facts, there is proubly a problem with either a injector not firing correctly, clogged fuel lines, clogged injector, or afm issues. did i miss anything? you'll be happy to know that it was getting 14.7:1 idling though I'm going to be taking things apart tomarrow to find the culprit. I'll let you know. Sorry... that's the nature of EFI and especially of the 280zx efi.... it's a complex system and problems can be caused by any number of things and you just gotta start eliminating them one by one. There are very few problems I've seen, heard of, or dealt with personally with ZX EFI that myself or someone else could say "okay this ONE THING has to be the cause". All the ZX's I've dealt with (3 so far) have been VERY prone to electrical bugs and glitches in the EFI systems... sometimes taking a lot of time and money to track down, some of which I never DID track down. You're dealing with 20+ year old wiring that has corroded and been worn or bent and exposed to high heat in the engine bay from that turbo... it was never made to last forever. Fuel lines and injectors get dirty and clogged every so often... this stuff happens and all of it can cause the kind of problems you were having. If you dont want to spend the time to try to track it down, pony up the cash to take it to a nissan shop that has a computer that can diagnose the EFI, and have your fuel system flushed, and go from there. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted May 21, 2004 Share Posted May 21, 2004 Just finished reading a post on wiggling the ecu connectors. Loose efi connector and unlucky putting the car on the dyno? Quote Link to comment Share on other sites More sharing options...
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