Author Topic: Strange problem from nowhere - solved!  (Read 7644 times)

Offline gox

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Strange problem from nowhere - solved!
« on: August 01, 2011, 08:11:14 pm »
After a year or more car running just fine,now it just started to missfire with no rule.On idle it will go up to the limiter,first gear up to 6500 (limiter is 7000) then all the higher gears missfires on below 5000rpm,in 4th or 5th gear it starts at 3800-4000rpm.There is no trigger errors,even tryed with different maps and checked all the config very carefully and couldn't find anything that would cause engine to missfire.
We changed almost everything that could cause this problem: coil,alternator,cap and rotor,spark plug cables....
Maybe someone can see something in log that we dont see....
Here is the log,its lean in some places because of the different maps that are used:

Engine is m20b25 with stock 60-2 trigger,stock coil rotor and cap,Holset HX35

http://www.vems.hu/files/MembersPage/MilanaPerisic/v3.3_n002834-2011.07.30-14.09.38.vemslog

« Last Edit: August 04, 2011, 07:06:48 am by BMW 325i »
E30 2.7 - VEMS,KKK K27.2,Schrick,1bar

Offline mattias

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Re: Strange problem from nowhere
« Reply #1 on: August 01, 2011, 10:54:55 pm »
With an upgrade to 1.1.95 you can supply more useful log files, and enjoy better functionality.

Your overboost fuelcut is a tad low.. set it to 250 kPa, if a signal hose to the wastegate melts it will be noticed.

You seem to have issues with low battery voltage, check all the heavy wiring, engine ground straps, also make sure your generator is really up to the task - it's common that this is overlooked, the stock one is usually too small once everything is powered up with powerful fuel pumps and cooling fans.

Also, since you're already running a missing tooth trigger - a cheap upgrade for the ignition system would be installing a coilpack and going to wasted spark. Some Bosch coils (Motorsport) are compatible with the stock wires used with the distributor, or just get a used coil and wires from some other vehicle. Many Opel V6 engines are suitable, and Ford. Two 4 cyl coilpacks could also be used, with one coil in the last coilpack not used.

Make sure you're using resistor plugs too, like NGK BCR7ES (small socket) or BR7ES. You can try plugs with 'P', like BPR7ES, but they are more prone to misfire with high cylinder pressure since the plug electrode is more exposed.

Offline gox

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Re: Strange problem from nowhere
« Reply #2 on: August 01, 2011, 11:05:39 pm »
With tried 5 different generators and it always shows the same voltage.Strange thing is that car worked fine for over a year with these settings.We prepared the bosch motorsport dis modul,it will be installed when i catch up some time this week.
We use BPR7ES plugs gaped to 0.6mm.
Still looks like problem is somewhere around the engine,since ecu works just fine and dont report any kind of errors...?
What kind of generator do you suggest to use,since i have similar problem with my car,but i don't have voltage drop below 13.3V...
Will config  from 1.1.88 work with 1.1.95?
E30 2.7 - VEMS,KKK K27.2,Schrick,1bar

Offline mattias

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Re: Strange problem from nowhere
« Reply #3 on: August 01, 2011, 11:31:14 pm »
Config from 1.1.88  requires only small changes to 1.1.95. After the upgrade, upload the config and get some peer review when you're at that stage.
Ignition plugs sound ok for what you're doing, but the BR7ES are more ideal.

What kind of generator should you use? I don't know, one that is a large enough? :)
Like I said, take a look at all the major supply wires leading to the starter and generator. Also the ground straps, there should be more than one and look to be in good condition.

From where do you supply the ECU with power ?

Offline gox

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Re: Strange problem from nowhere
« Reply #4 on: August 01, 2011, 11:39:20 pm »
Its supplied from the stock wiring,from the stock round connector that feeds main relay (with ignition on) witch feeds the ecu.Just like it was done with stock motronic wiring,only difference is that it is fused.The car is daily drive and has all the stock wiring.
Ok,will switch to BR7ES.
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Offline gox

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Re: Strange problem from nowhere
« Reply #5 on: August 02, 2011, 11:45:16 pm »
Still no success. :(
I have a new log from today.Checked fuel delivery,fuel pressure,new generator with ground to the chassis,changed trigger wheel....always the same,problems shows up in higher gears...
In this log i noticed that on VE 111,lambda is 0.91 and after that VE goes to 112 but lambda goes to 0.90 is this a result of EGO correction or what?

I forgot to say that even with batter calibration value of 200 vems shows 0.2V less then what DVM measures at battery?

http://www.vems.hu/files/MembersPage/MilanaPerisic/v3.3_n002834-2011.08.02-13.17.04.vemslog

Check the log at 0:25:xxx you can see that TPS is 100% and engine is not revving up...
« Last Edit: August 02, 2011, 11:52:13 pm by BMW 325i »
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Offline mattias

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Re: Strange problem from nowhere
« Reply #6 on: August 04, 2011, 01:06:27 am »
Quote from: BMW 325i
In this log i noticed that on VE 111,lambda is 0.91 and after that VE goes to 112 but lambda goes to 0.90 is this a result of EGO correction or what?
You don't even have EGO correction enabled at that point. Somethings is seriously wrong here, lambda will not read correctly.

Quote from: BMW 325i
I forgot to say that even with batter calibration value of 200 vems shows 0.2V less then what DVM measures at battery?
You're just telling me that you have a 0.2 Volt drop from the battery to the ECU. You should measure between ECU ground and fuse to get a good idea of the calibration.

I still think you should look over the generator, either the regulator is not doing it's job or you're simply overpowering the wires connecting the battery, starter and generator - and the ECU is connected somewhere in between.

Your datalog was a bit disturbing..  I must HIGHLY recommend to stop wasting time with 1.1.70 and upgrade to 1.1.95 right now, get feedback on the configuration settings once you've upgraded and then work from there.
Adding a wasted spark coilpack is not a bad idea either, but upgrade the software first and analyze the situation again.

Offline gox

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Re: Strange problem from nowhere - not solved yet
« Reply #7 on: August 04, 2011, 07:06:30 am »
Ok,good thing is that we found a problem ;)
Ignition system could not hold up 0.9bar of boost which is result of missfiring in higher revs when engine builds up over 0.7-0.8bar.
This problem never came up before because clutch was slipping all the time (not noticeably) now with clutch from M5 E34 we see all the power that engine produces...
This can also be noticed at the log too,if you pay attention on when it starts to missfire you can see it is only above 0.6bar of boost...

Now its time to check the wires and upgrade to some decent firmware.Strange thing with generator is that it is using stock wires,maybe we can try with new wires,also all of these generators were working fine (we try 5 different generators).We have bosch 3x2 coil ready i just need to catch some time to wire it up.

tnx mattias ;)
E30 2.7 - VEMS,KKK K27.2,Schrick,1bar