Hello,

My spark plugs keep blowing up. I think it might be the ECU but not sure.

I have two ECUs: one stock and one Stage0 ECU, remapped by Wankelshop:

The Stage 0 Engine Protection includes:

1. Elimination high revving the engine during cold start cranking.

2. Lowering the high idle speed rpm when the engine is cold.

3. Setting idle

4. Cold start limiter set to your wish rpm.

5. Increasing the oil injection amount.

6. Lowering the switch on temps cooling fan 1 & 2.

7. Elimination of dangerous lean running engine at part load all gears - The well known cat killer.

8. Adjustment of installed performance coils with better dwell timings

NEW 9. ECO adjustment to approx. 4000 rpm for more efficiency and performance.

Elimination of DTCs included.

With the stock ECU, the car runs "fine" (considering a very low compression engine, with lots of backfires).

With the Stage0 ECU, it runs much better but if I get near 6,000RPM, the spark plugs on Rotor1 explode. I'm guessing that number 8 (modified dwell timings on the coils) on the Stage0 ECU might be the issue but I'm not sure.

Troubleshooting done to isolate the problem:

-swapped coils around, in case it was a faulty coil - same result
-swapped plugs around in case it was a faulty plug cable - same result
-switched back to Stock ECU but now car does not hot start (Stage0 ECU fixes hot start issues on low compression engines) and backfires are constant

I was thinking of trying out Denso Iridium Racing plugs instead of NGK as to my knowledge, the only reason why the spark plug would explode like that would be due to very high voltage and I'm thinking that racing application plugs would go with racing coils (I have AEM Smart coils).

Picture one is for the first set of plugs (brand new, less than 5,000Km / miles, whatever) and picture two is for another brand new set which lasted one week

 

did you crack the plug when you installed them? thats all i can think of. also ive never heard of this ecu. got a link? what was used to remap the ecu?

 

The plugs were tightened by "hand". I know they need to be tightened to 17Nm but I don't have a torque wrench or whatever it's called.

I don't think they were cracked during install, otherwise the first set wouldn't last so long but if using a torque wrench fixes that, I'll try and source one. Picture with the white background is for the first set of plugs, picture with the red is for the second set.

Strangely enough, only the spark plugs on Rotor1 blow out.

I don't know what was used to remap the ECU but it works fine except for the spark plugs issue. Here's the link to the ECU remap:
https://www.wankelshop.com/product_i...all-years.html

 

i doubt an ecu would crack a spark plug but i cracked one years ago when installing it. what ecu/flash was used is important

 

Ok, I've asked Wankelshop about this.

If the increased voltage is from the wiring harness, would the Denso Iridium Racing plugs help over the NGK Iridium ones?

 

ngk oem plugs always. some boosted guys have shimmed rx7 plugs in a renny but i doubt thats your case

 

Ok, I will order another set of NGK Iridium ones and find a torque wrench and see how that goes. Will reply with what method Wankelshop used for the remap, if they answer. Thank you for the help!

 

What kind of socket are you using? When you say "Rotor 1" do you mean the front or rear rotor?

 

Just a normal wrench you would inf for tightening spark plugs on any ol' piston car. By Rotor1 I mean the one that is the closest to the radiator

 

update:

Reply I got from Wankelshop regarding the remapping:

" Hello, I use several softwares for the Mazdas from Versatuner, Cobb, Mazdaedit and so on. Your problem has nothing to do with the stage 0 Mapping. I mapped alone this year over 100+ RX8 Stage0. Spark plugs were either dropped or tightened too hard. Please install a new sparkplug".

And he was right. Got new plugs but in the meantime, the engine is bleeding oil. 1L (33oz) in 9km (5miles). I will replace it in a few weeks. This is what I had waiting for me in the parking lot

 

you don't have any business tuning your own car

 

^agreed. That's why the good folks at Wankelshop tuned it for me. I just installed the parts and turned the key.

As for me thinking that a high enough current would make a spark plug explode, I thought that made sense. Does seem a bit silly now that I think about it. A car can't really generate that kind of power otherwise it would explode every spark plug at every start up.

But I'm here to learn and unfortunately, it's a slippery slope. I've started reading, asking and posting about this car on every forum I could find since over a year and a half ago and I'm still learning since some people say "yey" while others say "ney" and I'm basically caught in the middle.

 

I don't see how this could happen except for a side force applied to the spark plug. So what is that force? Are you holding the wrench at an angle when installing or uninstalling the plug? Is the spark plug wire too short?

Those are the leading plugs, do the trailing break also?

 

I was just tightening them too hard. I don't have a torque wrench so I thought I would just tighten them as hard as I could. It was just sheer luck that the other ones didn't co kapow also. Or maybe I dropped them before installing and the crack expanded when the engine was running.

Got new plugs and a new engine. Gonna make the swap in the coming weeks