08-24-2019, 11:27 AM | #1 |
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Hello all. I’m new here. Just got a 2014 M5 CP with 50k miles on it. Love the car but I’m having spark knock issues. Most any time I role into the throttle above 30-50% I get knock as it gets into the boost. I’m in nor cal so I get acn fuel but I wouldn’t think it wouldn’t think it would be this bad. Car is bone stock. I obviously use premium fuel. I got bm3 just to monitor and confirm it was truly knocking. The logs confirm what I’m hearing. I would love to put a stage 1 tune in it but if it gets spark knock in stock form I’m worried. I have changed plugs to ngk 95770 1 step cooler with no change. I switched to Amsoil 0-40 signature oil because it has the api-sn plus rating. Thought it may help after reading about all the low speed pre ignition stuff new di motors see. No change though. It doesn’t consume very much oil so I don’t think that’s contributing. Maybe 1/2 a qt in 3k.
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08-24-2019, 09:38 PM | #5 |
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Yeah for tuned vehicles. I’m stock and don’t plan on going over stage 1 ever so I didn’t see the need for 2 heat ranges cooler. Most stage 1 tunes are ok with stock plugs if they are relatively fresh. Then again maybe I should have gone 2 steps cooler due to the crap gas we get in CA.
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08-28-2019, 01:23 AM | #6 |
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Also was wondering if a tune may help this issue by increasing the amount of fuel at lower rpms. Stock the afr is 14.7 at wot until almost 5k rpm then it tapers to 12.6 by redline. That seems a bit lean to me at least in the lower rpm. Looks like some of the tuned stuff runs a bit richer down low. Maybe that will help cool the combustion and drown out some of the pre ignition. I may try the stage one tune and do some logs to see how it reacts.
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08-28-2019, 02:52 PM | #7 | |
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08-28-2019, 11:46 PM | #8 |
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Your absolutely right. I wouldn’t go into this without carful monitoring and data logging. I operated a dyno professionally for 6+ years. I have a good ear for hearing knock. I would love the increased fuel from the tune without the extra boost. I haven’t learned the bm3 tuning software but if I do I guess I could try to richen up the afr and see if it helps. I’m starting to think the factory bmw tune runs things as lean as possible with aggressive timing for max efficiency making it close to knock as is. Then you throw in the fact it’s not running on 93 octane. Also the 91 in CA is even worse then the rest of the countries fuel.
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08-29-2019, 05:02 AM | #9 |
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If it's knocking and you say the petrol in CA is questionable then I would try putting an octane booster into the tank.Don't like to say your being shortchanged in your particular area but we in UK have 99RON petrol for our M5's with stringent checks from government inspectors on suppliers.
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08-29-2019, 05:15 AM | #10 |
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I've run my M5 on several tanks of non-ethanol 90 octane (US) without issue other than probably a little less power. The fuel mileage increased though. I should note that the temps were a bit cooler. It was probably in the 50-60F range at that time.
It's possible your high pressure fuel pump is showing signs of weakness. Being a 2014, you already have the updated version, but that doesn't make it bulletproof either. Dirty injectors could also factor in. Do you ever get "shadow codes" for any misfires? It's not the greatest diagnostic path, but I would also try the octane booster for a couple of tanks and maybe get a quality injector cleaner run through. See if there is any improvement. |
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08-29-2019, 08:58 PM | #11 | |
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08-29-2019, 09:58 PM | #12 |
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Definitely take a closer look at afr. Lean condition is anything above 14.7 to 1. Depending on mileage maybe think about a bad o2 sensor or vacuum leaks. Like technician117 mentioned too, maybe your hpfp or injectors are giving out. You could try some race fuel to see if that bumps down the afr.
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08-30-2019, 12:09 AM | #13 |
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I think I’ll try an octane boost and see what happens. Tough to diagnose this one. No codes whatsoever and runs fine besides the sound of pinging when getting into boost. Even the data logs look to be normal. So when it’s running at 14.7 under heavy load conditions the fuel trims are dead on so it’s doing what it wants it to. Only thing is if it’s a bad sensor it’s making its corrections based on false data. Just hate to throw parts at it.
When using Bootmod3 does anyone know how the spark on all the cylinders is monitored. You can see 1-4 not all 8 and if you look at superknock there are 9 channels you can monitor but none are labeled. I’m guessing the superknock is in counts per cylinder because some are at 0 and others are at 300 plus. May have to do another post on this to figure out how BMW does things in the DME. |
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09-01-2019, 04:56 AM | #14 | |
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09-01-2019, 07:59 AM | #15 |
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O2 sensors can get lazy and not throw codes. Happens all the time and across any make/manufacturers. At 50k miles, his are about due as a PM change anyway (the primary o2's).
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09-25-2019, 06:43 AM | #18 |
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Knock as we all know is usually caused by too much timing advance and or being too lean fuel mixture.
I'd get it on an AFR meter to check it. Maybe change the O2 sensors as these are very sensitive on the S63tu. Not sure can be done on a stock engine with regard to timing, maybe get a tuner to check it and adjust as required. Get a reputable stage 1 map put on with a touch of extra fuelling and a degree of retard to keep things safe?
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09-27-2019, 12:31 AM | #19 | |
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im just trying to know more and understand better in the case i get this bc every video ive seen on f10 knocks, im not sure if it is actually knocking, bad vid quality, etc |
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09-27-2019, 02:17 AM | #20 | |
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09-27-2019, 02:36 AM | #21 | |
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09-27-2019, 12:53 PM | #22 | |
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