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Discussion Starter #1
application: BBC twin 78/75 turbos , 210 lb hr injector , LS cop ,DIY autotune 36-1 trigger wheel and crank sensor , efi connection 1X cam sensor.
I had been running in batch for initial start up and first road trips. it would run somewhat ok but had sync issues as rpms climbed past 2500 rpm and would occur more often as rpm went up. I have tried multiple air gaps on the crank sensor and i am currently at .015>.018 measured around the circumference of the trigger wheel. i have added a 1k resistor to the cam sensor and i have verified i have .07 volts off> 4.9 volts on on both sensors. I have composite logs that show no sync errors while i am having the current engine operation problems.Sync errors have not been completely eliminated but they are rare now.
I have since made the switch to sequential and I am not able to do more than a start up and run for short periods of time. the engine initially fires up and and sounds good but about the time the O2 sensors start working some 20 seconds or so after start up the motor noticeably sounds worse with light popping out the exhaust and starts fouling plugs. I am assuming the popping is causing extra air the O2 sensor is reading so it is adding fuel.
I have done some of the typical checks such as manually firing injectors and coils to verify operation and firing order.
I have been working with a guy out east who has been looking at logs and helping with suggestions but it I may be overlooking something physical.
I can share my files if someone would like to see them.

Is there anyone near the Tulsa area familiar with the megasquirt products I can have double check my install ?

thanxs
Mike
 

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Have you contacted DIYAutoTune? Matt is the man to help you figure it out. I sent him an email on a LS project, and he helped me figure out what was wrong (my lack of wiring proficiency). I'm following your posts here and on facebook. We're now doing something very similar to what you're doing. Please report back on here when you get it figured out.
 

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Discussion Starter #3
I have emailed Matt and spoke to him on the phone , he had noticed a double trigger I had on one tooth that ended up being a burr on that tooth and on an email I just read he recommended a much larger air gap of 1mm on the sensor. I have another vehicle with a microsquirt on it and I have not had near the issues I am currently having. Some of it is a learning curve on my end some of it I am sure is do to the endless possibilities of engine configurations.
 

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Discussion Starter #4
I am also questioning if some parameter such as fuel requirement could be off enough to cause these problems as I have pulled some 25% fuel in the very table in the active cells and I still am fuel fouling plugs. I have a symptom on cylinder 6 where it is washing the plug clean. I thought it might be an injector dripping issue so I had them tested and flowed and all the injectors were fine. I test fired the coil and it worked. I pulled that plug wire off and ohmed it in many positions and it was 55 ohm on a 14 in wire which is similar to all the others.
All the plugs are fouling within minutes but #6 is fouled and washed clean
 

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Reasonable dwell? I wouldn't run it in closed loop for idle nor maybe at all while you try to figure out this problem. Just get that complication out of the equation.
Maybe the stupid stuff first. Run the valves? No valves tight or loose? Vacuum leak or even header leak? Your logs showing any additional enrichment at idle? Accel enrichment that is set up really sensitive can play hell with a tps signal that has just a touch of noise. It will sit there and throw fuel at it all the time because it thinks the throttle is being wacked.
 

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Discussion Starter #8
Dwell is 3 ms .checked valve lash and I am loose a couple of thousands . I did a compression test and I was at 150 psi throttle closed (low compression with a 250 degree cam) which is my engine's average. Tps tracks good at 0 with the throttle closed.
Please continue asking questions as I believe it is something I am overlooking or knowledge I still need to acquire.
 

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Where is WBO2 sensor(s) installed, clock relation to position and what rpm is it going into closed loop??

Does it have IAC valve??

What fuel scale is it running and what commanded AFR at idle and low rpm??

What plugs??

Although not as popular the last few years the flying magnet trigger setup is why everyone quit running all the non-magnetic trigger setups 20yrs(or more) ago. They aren't as nerdy as the fine tooth Hall Effect trigger setups that have come back in vogue the last few years. However they are like a baseball bat, simple and effective.
 

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Its ur non resistor sparkplug causing rf noise. Put any resistor plug i bet money ur problem will go away
 

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boost ref fuel pressure regulator? I had a new magnaflow regulator with a pin hole in the diaphragm... it after a few minutes of running it would start pushing fuel into the intake. I hydraulic locked the engine twice before i figured it out.
 

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Discussion Starter #13
nitrous sbc383 i owe you the beverage of your choice. I put Autolite 24 plugs in it and most all problems went away. the engine sounded cleaner and when i pulled a little fuel out for my idle cells the afr's responded correctly.
again thanxs

the engine did die after running for a few minutes and does not want to restart. It has the symptom like it ran out of gas but my data log shows a consistent 42+ psi (target 43) fuel pressure. It had done this a couple of times thru out the week and i would let it sit with power off for a few hours and it would start back up, although it ran terrible before the plug change.
I am going to look more at the data log to see if i can see why it died.
 

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nitrous sbc383 i owe you the beverage of your choice. I put Autolite 24 plugs in it and most all problems went away. the engine sounded cleaner and when i pulled a little fuel out for my idle cells the afr's responded correctly.
again thanxs

the engine did die after running for a few minutes and does not want to restart. It has the symptom like it ran out of gas but my data log shows a consistent 42+ psi (target 43) fuel pressure. It had done this a couple of times thru out the week and i would let it sit with power off for a few hours and it would start back up, although it ran terrible before the plug change.
I am going to look more at the data log to see if i can see why it died.
Good call. I would still suggest that you take control of the idle tuning. AND double check on the logs to make sure accel or other enrichment isn't happening. If you had noise on the tps, that will trigger enrichment. You end up chasing it to the point where it dies from being overly rich. And the o2 sensor in my experience is worthless at idle tuning and can jack things up there. IMO, idle tuning especially at first is best using the kiss method.
 

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Fuel pressure? Someone else could chime in, but those big injectors probably aren't the best at idle..
I would jack the pid's up and enable auto tune right at startup. You might need to click in the advanced tab to adjust the temp and load so it will run at cold startup.
 

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I've also got a 540bbc twins on the ultimate.....are you using a ls wiring harness..if so, the different firing order will fuck with things....had to move injectors and coils around.....let me know if you need any data from me....
 

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Discussion Starter #18
I am using the universal harness. So I terminated injectors and coils in the standard BBC firing order.
Since changing to the resistor spark plug I now have a tune able engine.
I do have several problems still.
The engine dies randomly after warm up , symptom is running out of fuel as the engine rpm tapers off as the engine is dieing but tuner studio gage monitoring my pressure transducer mounted on the regulator shows a constant 43'ish psi. The engine will not restart for a period of hours after this happens and then restarts easily and runs as if there is no problem. During the time it will not start tunerstudio fuel pressure gage shows proper fuel pressure and I have cracked loose the fuel line at the fuel rail and it is under pressure. In megalog viewer during the time the engine is dying it displays a falling fuel pressure but I am unsure of that data as I do not have the fuel pressure regulator boost/vacuum referenced right now and megalog viewer show a rising fuel pressure as high as 90 psi at times.I am installing a mechanical gage to verify fuel pressure. I have data logs of the engine dieing.
My IAC doesn't work, I do not get voltage changes from the ECU while in test mode on the 4 pins. It is an LS style IAC.
My flex fuel sensor does not work. I have flex fuel fail status indicated in tunerstudio.

Turbocuda, I would like to share tunes to help me learn more. [email protected]

Thanks
Mike
 

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Turn off the EGO control and tune it straight from the fuel and timing tables. Also turn off the flex fuel sensor blending and put the same fuel in it until you get this worked out.

You mentioned early on that the issue would develop about 20 seconds after initial startup and you equated that to the O2's becoming operational. Your O2 control is set to start correcting 20 seconds after startup - I see a correlation there if it is still occurring in the same manner. What are your engine state settings set to? And what does Matt C. have to say about this?
 

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Turn off the EGO control and tune it straight from the fuel and timing tables. Also turn off the flex fuel sensor blending and put the same fuel in it until you get this worked out.

You mentioned early on that the issue would develop about 20 seconds after initial startup and you equated that to the O2's becoming operational. Your O2 control is set to start correcting 20 seconds after startup - I see a correlation there if it is still occurring in the same manner. What are your engine state settings set to? And what does Matt C. have to say about this?
Seriously this right here. Get all the complications out of it and just get it to idle steady state without corrections and enrichment.
 
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