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dpuma8

Possible spark blow out. How small of a gap can I run

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I have an L28et with GT3076r turbo and Megasquirt 2 3.57 with NGK R BPR6EY plugs that were gapped at .03.  With this gap, I could not rev past 3200 rpms but after gapping the plugs down to .025, I now can rev my car to 4200 rpms before it happens again.  Do I need new plugs or do I keep closing the gap on my spark plug?  What is the smallest gap I can run?

 

 

and I had problems with revving past  3200 rpms.  I changed the gap to .025 and I can now rev to 4300rpms before I run into the revving wall.  

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I've run 0.020" at higher boost levels. This is where porting and a cam comes into play. Keeping your boost below 15psi really makes this part of life easier.

On a single coil system, you are limited like this. Go COP and the gaps can open up again, get smoother idle and more consistent firing!

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On 6/15/2019 at 2:21 AM, dpuma8 said:

I have an L28et with GT3076r turbo and Megasquirt 2 3.57 with NGK R BPR6EY plugs that were gapped at .03.  With this gap, I could not rev past 3200 rpms but after gapping the plugs down to .025, I now can rev my car to 4200 rpms before it happens again.  Do I need new plugs or do I keep closing the gap on my spark plug?  What is the smallest gap I can run?

 

 

and I had problems with revving past  3200 rpms.  I changed the gap to .025 and I can now rev to 4300rpms before I run into the revving wall.  

Other's have asked what coils you are running and this is important since you run the MegaSquirt.  You need to know the dwell time vs spark energy of your specific coil so you can input the appropriate dwell times in your software.  Too little dwell can result in too little spark energy.  Gapping down to 0.020" is not uncommon for high boost applications, but with a good coil setup no reason you can't run much higher. 

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Just an update.  I smoothed out the tune a lot and now I can rev it without any issues like I had before.  My problem now is fluctuating boost at WOT.  My logs show boost is erratic up to 12psi meaning that it rapidly goes up and down 3 psi until I get to 12 psi near 6,000 rpms.  Above 4500 rpms, the car sound slouder but doesn't feel much faster.

 

  My voltage is in the 12's and will drop to high 11's at higher rpms.  So possibly a spark blowout?

 

I am using an All-Star 81230 coil, magnecor wires, Tial MVS wastegate with 10psi springs, NXS manual boost controller, Greddy BOV on the hot side.  The MBC and BOV share a vacuum line connected to the intake manifold.

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Posted (edited)
5 hours ago, HuD 91gt said:

Why is your voltage so low?

 Exactly. Coil secondary output can drop up to 15% with a voltage drop of only 1.0 volt. A correctly operating charging circuit on a Datsun should put out 13.5 volts easily.  ALL the way from idle to Redline. At 11.5 volts you could be seeing over a 30% drop in Coil output. 

 

European cars typically put out a bit higher voltage. 14.1 to 14.2 volts charging is not uncommon on most European cars since the mid 90's.  

Edited by Chickenman

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On 8/2/2019 at 6:19 PM, dpuma8 said:

Just an update.  I smoothed out the tune a lot and now I can rev it without any issues like I had before.  My problem now is fluctuating boost at WOT.  My logs show boost is erratic up to 12psi meaning that it rapidly goes up and down 3 psi until I get to 12 psi near 6,000 rpms.  Above 4500 rpms, the car sound slouder but doesn't feel much faster.

 

  My voltage is in the 12's and will drop to high 11's at higher rpms.  So possibly a spark blowout?

 

I am using an All-Star 81230 coil, magnecor wires, Tial MVS wastegate with 10psi springs, NXS manual boost controller, Greddy BOV on the hot side.  The MBC and BOV share a vacuum line connected to the intake manifold.

 

The boost fluctuation sounds like an issue with your duty cycle of the closed loop feedback on your boost controller assuming it is controlled by the MS.  Without knowing how or what you use for a boost controller hard to exactly know what is happening.  Regarding the dwell and voltage, the spark energy will be a function of both dwell time and battery voltage so a lot of systems have a 3D map to account for both variables.  I run the Bosch P100-T coils in the link below and going from 14V down to 12V requires ~0.9ms of additional dwell to achieve equivalent spark energy. 

https://www.finjector.com/documents/4ec9f695740c8/0221604006_DataSheet_enUS_T6821266699.pdf

 

From what I saw based on a quick check on the summit racing website, your coils will run in the 4.0ms range, but that is based on a calculator and not the actual coil performance from the manufacturer.  You need to get the actual dwell times as a function of current draw and battery voltage to be accurate and then run them at a level sufficient based on the spark energy you desire.  For the Bosch coils on the EVO I run them pretty hot at ~80mJ of spark energy based on a 7amp draw, but I also run ~35psi on a 9.5:1 motor.

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Not sure why my voltage is so low and I am not sure where to start looking.  I have a Z Specialties 105 amp alternator that needed to be rebuilt for bad bearings after not too much use.  I don't have any extra accessories like a radio or anything like that.  My car is wired with EZ wiring harness.

 

My boost flutter issue has been fixed by rearranging my vacuum lines.  My MAP sensor was hooked up to the #5 intake leg so I moved it to the port between #3 and #4.

 

I still have an issue though where it feels really flat once I get over 4500 rpms so I can't tell if this is because my P90 cam is losing steam, my ignition timing needs more advancing,  or because I have spark blowout.

2019-08-07_20.57.25.msl CurrentTune.msq

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On 8/14/2019 at 1:25 PM, dpuma8 said:

Not sure why my voltage is so low and I am not sure where to start looking.  I have a Z Specialties 105 amp alternator that needed to be rebuilt for bad bearings after not too much use.  I don't have any extra accessories like a radio or anything like that.  My car is wired with EZ wiring harness.

 

My boost flutter issue has been fixed by rearranging my vacuum lines.  My MAP sensor was hooked up to the #5 intake leg so I moved it to the port between #3 and #4.

 

I still have an issue though where it feels really flat once I get over 4500 rpms so I can't tell if this is because my P90 cam is losing steam, my ignition timing needs more advancing,  or because I have spark blowout.

2019-08-07_20.57.25.msl 2.05 MB · 1 download CurrentTune.msq 119.09 kB · 1 download

 


Hi, 

 

I took a look at your log and tune and have a few suggestions

 

- Your TPS doesn't appear to be calibrated right. It looks like you are going WOT and only achieving about 85% TPS

- Your spark plugs are the wrong heat range. They are too hot, 6 is an N/A heat range. You should be running a 7 heat range plug like a BKR7E or BPR7E. 0.028 gap should be fine 

- Based on logs you make boost really late for such a small turbo. Is this just you only jumping on the throttle later in the powerband or is this where you have to be to make pressure? Do you have boost leaks? You should make or buy a boost leak tester and test. For comparison I am running a older, less efficient, larger frame turbo, and making positive pressure at 2k and start making decent power around 3k.

- I'm not sure how accurate your wideband is but things look a bit fat under boost generally. I'm seeing high to mid 10 AFR's on some of your pulls, low 11s on others. Try to target mid to high 11s under boost if you can

- Your spark map looks too conservative to me. In fact, all of your timing seems to diminish as RPMs go up. This is actually the opposite of what you want: Once you are past peak power, you should look to slightly increase timing to to carry power higher in RPM range. FWIW my tune on my L28ET (that I messed with on a dyno and whatnot but admit is far from perfect) is at 24 degrees advance at 180KPA, yours is between 22 all the way down to 18 depending on RPM. Again, FWIW, messing with my timing, under power, I was able to gain 5-10HP per degree of timing added - if something like that is true on your engine, you could imagine yourself dropping 20-40HP as you remove timing at the top of your powerband. Maybe this is some of the flattening out at 4500 that you're feeling? I'm not recommending that you just jump everything up to like 22 degrees at that load or whatever, but you should definitely review some other people's tunes and whatnot and consider tinkering with this a bit

- I don't recommend running a tiny gap. I thought I was having ignition issues on the dyno, de-gapped a new set of BKR7E plugs to 0.020, and then fouled them out after only a couple of pulls, losing power after every pull. I don't think a single coil setup can reliably run this small of a gap. I slapped another set in at 0.028, got all of the power back, and then did several more pulls without issue. 

- Definitely fix the alternator issue or look into something shorted out and drawing too much power. I really recommend swapping to a 1 wire GM alternator. They are way cheaper than Datsun alternators, super reliable, and you can get them at almost any parts store. The swap took my less than an hour after my ZXT alternator failed. Highly recommend. No reason for you battV to be moving the way it is and I'm sure it's making megasquirt pretty angry. Test out your voltage in a few spots on your wiring harness. It might be that you just need to put the megasquirt on a relay more directly tied to the battery if you’re getting 14v elsewhere. According to the megamanual, your megasquirt should be powered off of a relay powered directly from batt positive itself and not from any other source. 

- Try a higher averaging lag setting on your RPM input, it might help it smooth out RPM input a bit. It's really shaky in your current setup. I've been messing with this on my tune too

- Move your MAP signal, it looks a bit dirty. You may want to try moving it somewhere on the manifold where a single cylinder's pulses can't affect it so much

 

hope you find this helpful :) wrenching on a megasquirt system can be both frustrating and reeally rewarding once the stars align and it finally works properly!


edit: also wanted to note that you should separate your BOV and MBC lines. Generally people put their BOV on a dedicated vacuum line from the intake manifold, and then run the MBC/wastegate off of the charge piping or off the compressor itself if it has a nipple

 

another note I just thought of: how are your grounds? In my experience, megasquirt gets angry with poor grounding. All of megasquirt’s grounds should be run back to the intake manifold and grounded together, separate from all of the car’s other grounds. 

Edited by Zcardude

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My 105 amp alternator is a 1 wire setup.  Is there a general safe advance map for an L28et?  I see some of the maps in the Megasquirt map sharing section of hybridz but I am not sure if any of them are safe or not.

 

My voltage issues are better after rearranging things but not perfect.  Now MS will read 12V at idle, increase to 14.2V while drivinjg with some moments where it drops to 12 again before raising up to 14.

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It sounds like you may have an issue with the alternator, you should not see the voltage drop once you are off idle, but that when measured at the battery or fuse panel.  I'm not sure where your voltage is being measured - if you are getting that off MS, you don't have a good power wire to the ECU, it is dropping voltage when you make it busy.

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7 hours ago, dpuma8 said:

My 105 amp alternator is a 1 wire setup.  Is there a general safe advance map for an L28et?  I see some of the maps in the Megasquirt map sharing section of hybridz but I am not sure if any of them are safe or not.

 

My voltage issues are better after rearranging things but not perfect.  Now MS will read 12V at idle, increase to 14.2V while drivinjg with some moments where it drops to 12 again before raising up to 14.

 

I don’t think there’s a known “safe advance map” for our engines, but what I said about timing slightly increasing after peak torque is a really common pattern. If you take your car to a dyno and have someone tune the timing, that’s how your spark map will end up. Guaranteed. In the meantime ensuring that your base timing is set right and then reviewing a lot of other tunes and staying conservative is probably alright. But you shouldn’t lose several degrees of timing as you run up through the RPMs. 

 

Also yeah it sounds like you’ve got a problem with your alternator or some kind of wiring issue. I mentioned that you may want to try to relay the megasquirt directly off the battery rather than scabbed into some other part of the electrical system (not that you’ve done that ;) I obviously don’t know what’s going on with your wiring), that may help if you want to try something that should only cost a few dollars rather than needing to do a whole alternator swap. FWIW I’m running a 90A Gm 1 wire and based on datalogs I fluctuate a whopping .1v over the course of a very long drive, essentially keeping a rock solid 14v constant. That should be your goal and would probably be a decent place to start solving problems with your install. 
 

Definitely post results as you try things out and they get better. I messed with my L28ET megasquirt setup for quite a while before I finally started becoming happy and relatively satisfied with it. Good luck!

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