tooquick260 Posted June 10, 2013 Share Posted June 10, 2013 Ok I have my turbo swap completed and working out small details (checking interior under dash wiring question in other posts) I have a AEM tru-boost controller in my car. I have played with boost a little bit. When initially installed with the controller off just using as a gauge the boost was reading 5.6 as a max. Is that normal for these cars? Car runs goooood on this as in drive ability! Smooth power is good with some slight hesitation sometimes in first. Ok, so when I reset the parameters in the controller to up the boost and max it out at about 7 lbs of boost. The car will about 3/4's of the time run good but cut out back fire when getting up on the boost the other 1/4 of the time, boy when it doesn't cut out its a blast. So, being a goofball or what ever you want to call me. Upping the boost to 10 lbs and the car comes alive it is really fast compared to what it was n/a. But the backfire farting issue is more prevalent. What I have.... L26 block, compression at 8.7 to 1, stock 83 ecu, stock 83 used injectors, stock 83 wiring harness yes crackly wires, intercooler, 240sx throttle body, P90 head with an upgraded cam, 2 1/2" exhaust to a 2 1/4" inlet round muffler to a 4" outlet. Questions or deductions. Am i driving past the ability's of the ecu/afm? Do i have a fuel delivery problem? I do also have an AEM air/fuel gauge in the car. When the farting happens the gauge is not spiking total lean, its highest reading is about 14.2 ratio. Under boost when it does not fart or cut out it reads about 10.7 as lowest and usually stays around the 11.4's. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted June 10, 2013 Share Posted June 10, 2013 Sounds like fuel or spark. 7ish psi is stock and 10psi is completely normal for an L28et. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 11, 2013 Author Share Posted June 11, 2013 Yeah thats what I am thinking.. weird that it doesnt do it on lower boost. Question is why.... what is making this happen. Quote Link to comment Share on other sites More sharing options...
Xnke Posted June 11, 2013 Share Posted June 11, 2013 Keep in mind you're feeding a smaller motor; so you should be able to run 10lbs no problems. Check your plugs for death ash or signs of fouling; and remember that if you are misfiring the O2 sensor will read rich...even if you are lean! Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 11, 2013 Share Posted June 11, 2013 (edited) I thought this thread was about a person you knew with indigestion and a bad attitude... If it was NA I'd say you had a lean condition, maybe a lean spot in the AFM or low fuel pressure. But the same should apply to boost I would guess. What's your fuel pressure? edit - pretty sure that the FPR raises fuel pressure under boost, just like it lowers it under intake vacuum. If the hose from the manifold to the FPR is off or blocked, you'll be rich off-boost and lean on-boost. Somethng to check. Edited June 11, 2013 by NewZed Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 11, 2013 Share Posted June 11, 2013 Keep in mind you're feeding a smaller motor; so you should be able to run 10lbs no problems. Check your plugs for death ash or signs of fouling; and remember that if you are misfiring the O2 sensor will read rich...even if you are lean! Correction , if you are misfiring the O2 will read lean . It's an O2 sensor , it detects oxygen content . Misfired occurs when air/fuel mixture didn't ignite ( no boom ) . The O2 will detect unburned air/fuel mixture when misfired occurs , but it detects only oxygen ( by design ) not HC ( fuel ) . Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 11, 2013 Author Share Posted June 11, 2013 Keep in mind you're feeding a smaller motor; so you should be able to run 10lbs no problems. Check your plugs for death ash or signs of fouling; and remember that if you are misfiring the O2 sensor will read rich...even if you are lean! OK, i havent checked the plugs since I first started the motor. I agree that the motor combination should handle the boost. Should be able to go to 12lbs! So, this is more of intermittent issue. I am going to clean all the contacts again and do some more wire chasing to see if I have some faulty connections. I thought this thread was about a person you knew with indigestion and a bad attitude... If it was NA I'd say you had a lean condition, maybe a lean spot in the AFM or low fuel pressure. But the same should apply to boost I would guess. What's your fuel pressure? edit - pretty sure that the FPR raises fuel pressure under boost, just like it lowers it under intake vacuum. If the hose from the manifold to the FPR is off or blocked, you'll be rich off-boost and lean on-boost. Somethng to check. Fuel pressure is at 38 lbs. The vacuum line to the FPR is working, as in if I pinch the vacuum line and rev the pressure does not change. When open the pressure changes when rev'd Correction , if you are misfiring the O2 will read lean . It's an O2 sensor , it detects oxygen content . Misfired occurs when air/fuel mixture didn't ignite ( no boom ) . The O2 will detect unburned air/fuel mixture when misfired occurs , but it detects only oxygen ( by design ) not HC ( fuel ) . Does this system really use the O2 sensor? I do have it hooked up. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 11, 2013 Share Posted June 11, 2013 My 83 turbo had O2 sensor . Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 13, 2013 Author Share Posted June 13, 2013 I do have the factory O2 sensor connected. Driving the past 2 days if I have a passenger it does it sooner, like when torque starts to climb the ignition/fuel breaks up. Now I can drive and keep it off boost and its faster than traffic. If you punch it goes right into fart, crackle misfire. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 13, 2013 Share Posted June 13, 2013 Sounds like you have a weak ignition system . Misfires under load . Check your coil , cap , rotor , etc. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 13, 2013 Author Share Posted June 13, 2013 It is original coil. Cap is new, rotor was cleaned up and reused. Will check that again.Spark plug wires are new. Why would it do this. I will get a video of this happening. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 13, 2013 Share Posted June 13, 2013 Make sure the wires are not AutoZone brand , see to many problems with this brand . NGK is the way to go . Quote Link to comment Share on other sites More sharing options...
cgsheen Posted June 13, 2013 Share Posted June 13, 2013 (edited) OK, i havent checked the plugs since I first started the motor. I agree that the motor combination should handle the boost. Should be able to go to 12lbs! So, this is more of intermittent issue. I am going to clean all the contacts again and do some more wire chasing to see if I have some faulty connections. Fuel pressure is at 38 lbs. The vacuum line to the FPR is working, as in if I pinch the vacuum line and rev the pressure does not change. When open the pressure changes when rev'd Does this system really use the O2 sensor? I do have it hooked up. OK tooquick, back to the FSM. You already know when the ECU "uses" the stock O2 sensor (hint: ONLY when it's trying to get into closed loop mode and that's only when you're cruising. Go back and read my previous explanation or the FSM - you know this, don't get confused by other comments...) The ECU is working off the base map when you're under load or in boost (as in: couldn't give a rats a$$ what the O2 sensor is doing) so it must not be getting the info it needs from other sensors. Could be sensor, connector(s), or wiring. (important stuff: Intake air temperature (AFM), AFM position, TPS (needs to know throttle is open), CAS (both 60 & 1 degree signals), CHTS...) (Most of the problems I had with the stock harness were actually at the ECU - the pins on the ECU, & the sockets. The 280ZX had a wonderful habit of leaky windshield. The placement of the ECU was right under the bottom left corner where the windshield leak would drip right on top of it. SO - my ECU and harness plugs were super corroded - fought with them for months! When mine "farted, choked, and stalled" I'd jiggle the wires going to the ECU to make it straighten up again. Moral: don't trust any of the electrical connectors on these 30+ year old harnesses) Fuel Pressure - sigh - go back to the FSM. (everyone that's sick-and-tired of me saying this over and over raise your hands. Ok, all of you can skip over the next paragraph...) Fuel pressure is not a static (constant) value. The FPR is supposed to maintain a 36.3 PSI differential between fuel pressure and manifold pressure. If your manifold is in vacuum (which it should be much of the time, and definately when at idle), your fuel pressure should be less than 36.3 PSI by the amount of vacuum. For example: IF your intake manifold was at -5 PSI (5 pounds of vacuum), fuel pressure should be reduced by 5 PSI (36.3 - 5 = 31.3). IF your intake manifold was at 5 PSI boost (5 pounds of positive pressure), fuel pressure should be increased by 5 PSI (36.3 + 5 = 41.3). This is explained in the FSM - even has a little chart showing fuel pressure relative to manifold pressure. Is your fuel pressure at idle really 38 when it probably should be closer to 28-30? Check your plugs. Are they sooted up - black? Edited June 13, 2013 by cgsheen Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 13, 2013 Author Share Posted June 13, 2013 I am getting schooled... Thanks for the info! At idle I am at 38 lbs of fuel pressure so, should i remove the vacuum line and reset the fuel pressure down to 36 lbs? Then reconnect the vacuum line and it should be correct. I will look at the plugs as well Quote Link to comment Share on other sites More sharing options...
cgsheen Posted June 13, 2013 Share Posted June 13, 2013 Sounds like a plan. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 14, 2013 Author Share Posted June 14, 2013 Ok ,, so I went down on the FP. No difference in performance. Car lays over going into upper rpms, stumbles and pops on boost Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 14, 2013 Share Posted June 14, 2013 FPR could have a bad diaphragm. On an NA car a bad (cracked or holed) diaphragm leads to extra fuel getting sucked in to the manifold through the FPR diaphragm. Under boost, the opposite would happen, you'd push air in to the fuel lines through the FPR. Rich NA, lean boost. Let it idle, no boost, and check the FPR vacuum hose for fuel. I'm just guessing, not a turbo guy. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted June 14, 2013 Share Posted June 14, 2013 Ok ,, so I went down on the FP. No difference in performance. Car lays over going into upper rpms, stumbles and pops on boost Didn't think that would help much, my "fuel pressure lecture" above was a "stop the misinformation!" comment (OK, rant...) not a "there's your problem" comment. (I guess I should start labeling them as such...) Go back to my first paragraph. When an L28ET ECU is getting all the information it needs, it'll make the engine purr like a kitten. (another disclaimer: here I'm also making the assumption that all the mechanicals in the engine are within stock specifications to begin with...) Don't over complicate it - each one of the sensors I mentioned above is fairly easy to re-test. The rest of the ECCS tests are pretty simple too. Go back through the FSM. And now for something completely different: Are you beginning to understand why I suggested that you just go ahead with the Z31 ECU swap from the get-go? This time spent on trouble-shooting the stock ECCS could have been used to - well, you see where I'm going... When you do the Z31 swap, you'll be re-visiting much of this. Exactly why I wish I'd just done my Infiniti M30 ECU / MAF swap when I FIRST put the turbo engine in. The only positive side to my stock L28ET ECCS experience is "the knowledge I've gained" - sigh... Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted June 14, 2013 Author Share Posted June 14, 2013 Yes, i have the chopper wheel and maf so far. Have located the Z31 ecu turbo, 150 and 199. Have not pulled the trigger on buying them yet. Well I do have a upgraded cam,,, so? I am suspecting the injectors. I have four of one shape and 2 of another. Don't know if I have an issue there, but it runs so good on lower rpms. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 14, 2013 Share Posted June 14, 2013 (edited) Most Nissan injectors are color coded . Make sure all your injectors are turbo injectors or at least they all match for your setup . Edited June 14, 2013 by Domzs Quote Link to comment Share on other sites More sharing options...
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