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  • Destroyed spark plug electrode on track, input

    Hey guys,

    I was at the track yesterday in northern California. It was hot.

    Motor is an S14A SR20, all bolt ons, 550cc and Z32 MAF. Car was running excellent, albeit hot (210-220*F (104*C)) until my third session, I had took some pace laps because coolant temps were just getting to hot. When I went to get back on it, the car would build boost (12psi, I run ~13psi) and was just very choppy. I do not recall an 'event' under load where things went to ****, it just happened after my cooldown laps. I'm hoping I didn't detonate big time. Here are the spark plugs I pulled out.



    Here were the maps I was running. I know timing is probably aggressive, it's in between a map I received from PL and the stock SR map. I figured plenty of idiots up the boost on stock ECUs with those timing numbers, so I'll be okay. Maybe I've joined the ranks of idiots.





    I replaced the plugs with BRK 7 iridiums, kudos to this awesome chick who gave me 4 the day before. I don't usually pack them, but now I will. I added some fuel, pulled 2* of timing in load area, and took it back out on track. It ran like a champ and doesn't seem any different now. I'll be boroscoping that cylinder along with leakdown/compression test this week. I'll check out the turbine wheel of my stock T28.

    Just looking for your guys input. Do you think this plug slowly eroded or it was a single event? Does this look like detonation? Speculation on damage caused or recommendations going forward? Should I be weary of this cylinder? I'll check out the plugs after a few 100 miles.

    Keep on boostin..


  • #2
    Definitely detonation, you can see the cracked insulator and all the specks of molten aluminum that deposited on the plug (those came from your head and piston).

    Your maps are a little all over the place. They also ramp in way too much ignition timing towards redline in my experience. The most I'd ever ramp in was 2 degrees on a given load from peak torque to redline. Even that ends up being pretty aggressive depending on how your engine breathes (anywhere from 4-6 degrees more timing added if you log it at a constant boost).

    Keep in mind the calculated load is going to alter based on the VE at the RPM, so it will actually decrease towards redline. So if you add in the 5-6 degrees your map does at the same load, it will actually trail off the load and add in another 2-4 degrees. So you'll be running really high timing up top where it's hard to hear detonation.


    You also have to realize that our stock ECUs are not as advanced as newer setups, so you cannot run the same tune for a max dyno number street setup as you can on track. You have to make the whole map conservative if you're going to take it on track since it cannot tell what's going on with the IAT, and doesn't really correct well for CLT either.
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    • #3
      I have essentially that same setup and have been using BKR7E, but get some detonation/knock unless i'm mixing in race fuel. I recently picked up some BKR8EIX (since I can't seem to find regular BKR8E) and might see how those do.

      Was told to take out a degree of timing. I suppose one of these days I should go for a retune on the powerfc, but not many places left around here!
      97 Kouki SR 240

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      • #4
        Originally posted by 0wn3r View Post
        I have essentially that same setup and have been using BKR7E, but get some detonation/knock unless i'm mixing in race fuel. I recently picked up some BKR8EIX (since I can't seem to find regular BKR8E) and might see how those do.

        Was told to take out a degree of timing. I suppose one of these days I should go for a retune on the powerfc, but not many places left around here!
        You don't really need to retune. Just grab every column/row whatever from about 26-28 degrees and pull out one or two (I'd recommend 2 if you're really knocking a bit without mixing in race gas).

        EGTs will go up, but it's the cost of keeping the engine from knocking on pump gas.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


        DefSport Koni Sleeve and Spring Perch Buy!!!
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        • #5
          Originally posted by Def View Post
          EGTs will go up, but it's the cost of keeping the engine from knocking on pump gas.
          Does that mean more turbo inlet gasket blowouts? Already on the 4th one. heh
          97 Kouki SR 240

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          • #6
            Yea - but they blow out anyway when you're on throttle a lot.

            Take it from me, just weld the damn thing together. I tried everything to get them to last with fasteners - just was not happening. Like you, I hit my 4th one and said F it.
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
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            • #7
              I've had problems with the inlet gasket in the past but I'm using stage 8 locking hardware and it is holding up great so far.
              Last edited by eye-5; 08-04-2014, 09:30 AM.
              Chicago Region SCCA SM # 688 http://www.scca-chicago.com
              TSSCC SM # 688 http://www.tsscc.org

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              • #8
                What plugs were you running?

                I'm curious as to why it was just #1... Was that plug hotter than the others?
                Is the timing somehow advanced on that cyl?
                A lot more deposits than the others somehow?
                A poor performing injector? -dirty, bad connection, or ??

                It might be a good idea to send your injectors to get cleaned

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                • #9
                  Originally posted by Def View Post
                  Take it from me, just weld the damn thing together. I tried everything to get them to last with fasteners - just was not happening. Like you, I hit my 4th one and said F it.
                  One of the times I actually cracked the stock exhaust manifold by that gasket area...talk about surprised.
                  97 Kouki SR 240

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                  • #10
                    A crack in the divider inside the collector? They all have that.
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
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                    • #11
                      Here is a question: Your fuel map, is that target AF readings (looks to be NISTUNE software)?? If so, unless you are running E85, anything over 12:1 in boost is pretty darn lean IMHO.

                      For a 300ZX MAF, it seems the transition from vacuum to 0 to boost happens between 50 and 60 on the Load scale from what if that helps for a frame of reference.

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                      • #12
                        The load vs pressure relationship changes with a changing k value if I'm remembering things correctly.
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                        • #13
                          Correct (and should be scaled based on injectors and MAF).

                          Even with a deviated K (which may not change much since the injectors require a decrease in K value and a bigger MAF requires a increase in K value, so the numbers may end up closer to "stock"), for a proper tune the threshold of 50-60 (or around 64) is typically where you transition into boost and anything above is boost.

                          Either way, if he is 12+ in boost (especially in high RPM where the knock sensor is de-activated) and still on pump gas, he will see a good amount of pinging and as you say, not have any way (unless it's audible) hearing it.

                          12psi of boost on a T28 will put in the the upper 90s to low 100s range (which I will confirm when I get home since I JUST did a Z32/490cc tune this past weekend and have my logs for) on the N62 MAF, give or take. So well into boost at 12:1 + on the AF. Not a good vale IMHO.
                          Last edited by RalliartRsX; 08-04-2014, 01:07 PM.

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                          • #14
                            Originally posted by RalliartRsX View Post
                            Correct (and should be scaled based on injectors and MAF).

                            Even with a deviated K (which may not change much since the injectors require a decrease in K value and a bigger MAF requires a increase in K value, so the numbers may end up closer to "stock"), for a proper tune the threshold of 50-60 (or around 64) is typically where you transition into boost and anything above is boost.

                            Either way, if he is 12+ in boost (especially in high RPM where the knock sensor is de-activated) and still on pump gas, he will see a good amount of pinging and as you say, not have any way (unless it's audible) hearing it.

                            12psi of boost on a T28 will put in the the upper 90s to low 100s range (which I will confirm when I get home since I JUST did a Z32/490cc tune this past weekend and have my logs for) on the N62 MAF, give or take. So well into boost at 12:1 + on the AF. Not a good vale IMHO.
                            Still don't agree with those rules of thumbs. Once you go to a Z32 MAF, your load values are going to change greatly from say 480 cc injectors to 550 cc to 740 cc injectors. You really need to check where you are in the map and adjust your tune accordingly.


                            The only hard part about MAF based tuning is knowing what your timing is relative to how much boost you're running at that point. The fueling is stupid easy (which I do agree that it needs to be richer than mid-high 12's, I'd say 12.0 at the leanest, and I actually like things more like mid 11's on pump gas).
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                            DefSport Koni Sleeve and Spring Perch Buy!!!
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                            • #15
                              This is a direct quote from the NISTUNE tuning guide Def

                              The Injection Multiplier (AKA “K Constant”) is one of the primary values that the ECU uses to calculate
                              injection times for most parts of the maps. So by adjusting this value we affect everything else.

                              If you’ve not changed airflow meter or injector size then K value need not be changed – only actual
                              fuel map values should be altered. If you have changed AFM/injectors, then it is necessary to adjust K
                              Constant. This is done automatically by NIStune if you use the “Resize Injectors” and/or “Change Mass
                              Airflow Meter” utilities under the “Operations” menu.

                              This calculation is based on a simple ratio of old vs new for both injectors and airflow meter. For example if the
                              stock K value is 34,275 and injector size was changed from 370cc to 550cc then the new value will be 21,475 x
                              (370/550) = 14,447. Bigger injectors require a smaller K value.

                              Same deal with airflow meters except we use maximum horsepower figures to do the calculation. For example it is
                              taken that a standard SR20 airflow meter gives its maximum reading at around 290hp. If we fit a Z32 airflow meter,
                              which has a max HP rating of approx 550hp then the calculation is 21,475 (standard K value) x (550/290) = 40,728.


                              If you change both injectors AND airflow meter you need to do both of the above calculations: 21,475 x (370/550) x
                              (550/290) = 27,400. Experience has shown that changing to a larger AFM and injectors at the same time is a recipe
                              for success because one increases K Constant and the other decreases it. A K Constant that finishes close to the std
                              value will always make tuning easier.
                              In all honesty, for all my tunes, I have never had to scale the K value constant greatly from what I started with on many setups. I end up individually scaling the load cells as I use my MAP sensor and MAF in conjunction to MAP across the board, so numbers that I quote for boost threshold is what I have found to be where boost starts for the N62 MAF. Yes, I am looking at the individual load cells via the ECU datalogger but the overall MAF scale will remain the same on the graph which would correlate across to Mass of air or HP.

                              I see what you are saying though of the K constant changing the load cells. However, there is a good chance the load cells above 50 are in boost, which explains why I saying why 12+ is way to lean for boost. At no point in his map is the AF number below 12........That can't be good and on pump gas, I am sure he was pining more from a super lean condition as compared to too much timing (or in conjunction with too much timing).

                              Its hard to tell from plugs because unless you run into boost and shut it off immediately, from what I understand, the plug readings will be off.

                              We all should know by now how much "HP" of air a T28 flows for a given boost for a basic SR20, which can then be mapped across to the MAF as well (for Horsepower produced).
                              Last edited by RalliartRsX; 08-04-2014, 03:00 PM.

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