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Old 12-25-2007, 12:56 AM   #1
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Default Detonation: Do I have it or not?

Hey guys, let me start off by saying merry christmas! Now to my question: Today I took the car out for a nice drive it was very cool outside and my intercooler pipes were not even hot, infact they were extremely cool. I did a bunch of runs and when I was goin flat out in 4th gear I would get some sort of noise between 5,000- to redline. It only happens in fourth gear fifth gear no noise nothing. Now my down pipe does rattle sometimes so I think that is what is making the noise, but I feel that the noise could be detonation what do you guys think? Owe this might help: 8psi, frontmount, stock ecu, 330cc inj., td04-15gHL
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Old 12-25-2007, 01:18 AM   #2
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Check your plug color. Detonation happens, or can happen, in any gear. What are you using for ignition management?
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Old 12-25-2007, 01:58 AM   #3
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90-94? watch the oil gauge next time.
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Old 12-25-2007, 08:54 AM   #4
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and by that he means if it gets jumpy/shaky when you are hearing that noise its detonation
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Old 12-25-2007, 11:29 AM   #5
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and by that he means if it gets jumpy/shaky when you are hearing that noise its detonation
I wanna chime in here. Question - even with the oil pressure gauge, is there any way you can have detionation without it affecting the gauge? And how dramitacally goes the gauge shake?
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Old 12-25-2007, 01:06 PM   #6
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The gauge wiggles back and forth about the width of the needle. It's noticeable. You can have detonation that doesn't affect the gauge, too, though.
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Old 12-25-2007, 01:15 PM   #7
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I have a 99 so unfortunately I can not tell by the gauge as for ignition management I have none because I never noticed any detonation and wanted to keep stock timing. Also, what should I look for on the plug that would indicate detonation?
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Old 12-25-2007, 01:30 PM   #8
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I believe you can also see detonation in the boost gauge (if under boost obviously).
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Old 12-25-2007, 02:00 PM   #9
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Quote:
Originally Posted by sickmiata09 View Post
I have a 99 so unfortunately I can not tell by the gauge as for ignition management I have none because I never noticed any detonation and wanted to keep stock timing. Also, what should I look for on the plug that would indicate detonation?
The easyest way to tell by the plug is if the electrode is all chewed up/the plug is damaged. Detionation is very hard on everything within the combustion chamber
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Old 12-25-2007, 02:04 PM   #10
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why not fix the downpipe rattle than asses if it still happens? that will rule out the downpipe
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Old 12-25-2007, 02:58 PM   #11
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why not fix the downpipe rattle than asses if it still happens? that will rule out the downpipe
+1 on that. Process of elimination.

http://www.verrill.com/moto/sellingg...colorchart.htm or
http://www.centuryperformance.com/spark2.asp

Look at the overheated, preignition, and the detonation plugs.

Do you have any form of air/fuel or wideband gauge on the car? Maybe your running lean as well. I have a '94 with the 'real' oil gauge and I've had detonation and never noticed the gauge moving. You can try retarding your timing a few more degrees and see if that helps eliminate the noise your hearing. If it's detonation it should get quieter or stop. What are you using for ignition management?
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Old 12-25-2007, 09:55 PM   #12
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99 has knock sensor for the ecu, which pulls ign if detected- and it's fairly sensitve
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Old 12-27-2007, 09:34 PM   #13
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99 has knock sensor for the ecu, which pulls ign if detected- and it's fairly sensitve
If knock is detected what can the stock ecu pull? 2-4deg? Infinite? I've never actually heard what the Miata's knock system is capable of pulling or if it has a limit. It might be interesting to find out. I still need to program mine.
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Old 12-27-2007, 10:15 PM   #14
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I don't know for sure. I ran the mazdacomp production shim-under-bucket valve train and custom cams in my 99 with stock ecu. The knock sensor picked up the new valve train noise as knock and killed all our new power. I never measured it as an ecu went in after that race.
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