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Discussion Starter #1 (Edited)
I discovered on my M5 that it’s s38b36‘s ignition timing is slow.
What would cause this?:1zhelp:
The reason i began my search is that the car has a hesitation starting from 5500 – 6800 rpm @ WOT.
What i checked/replaced with no success was:
1. I took the car to be checked on a diagnostic machine. They found nothing wrong.
2. Changed the plugs
3. Changed the HT leads
4. Changed the distributor cap/rotor
5. Changed the coil
6. Swopped the ECU with another car that was running correctly
7. Swopped the TPS with another car that was running correctly
8. Serviced/checked injectors
9. Replaced the fuel pressure regulator
10. Previous owner replaced the MAF 2 months before i purchased the car in 2009/feb.
11. Drove around with a fuel pressure gauge and found the pressure to be @ 3.5bar @WOT all the time
12. True TDC with a degree wheel and a dial gauge and found that the marks on the damper were spot on.
13. Then i removed the damper and the flange to check the keyway which i discussed in this tread. http://www.m5board.com/vbulletin/e34-m5-discussion/168408-b36-timing-chain-luck.html . Nothing was wrong.

After much, i discovered that the ignition timing is on 0 degrees when idling. Without authentication someone mentioned it must be 10 deg.
As an experiment i slotted the 8 holes on the damper + the 1small one on the dell pin by 6 deg (which equates to 1 tooth on the damper).
Before i slotted the damper’s holes the car idled on 0 deg and now obliviously it is on 6 deg.
I can report that the car pulls much stronger and it doesn’t hesitate anymore, nor does it detonate, but i don’t like this and would still like to know what causes it. Would it cause any damage if i keep on driving it like this(with the “false 6 deg” timing):1zhelp:.
Any ideas?
BTW – everything on the car’s fuel management is std. incl. the exhaust.
Thanks in advance.
Regards, Chris
 

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Idle @ 0deg is fine for this type of engine. See attachment. It might deviate from listed due to other factors (idle regulation in DME adjust ignition and ICV according to circumstances).
If your Reference mark sensor comes over to the mark on the timing cover and the piston is in TDC (remove spark plug and use a long screwdriver or whatever you prefer.

I had an engine in with some similair "adjustments". The timing damper in front was set differently due to a non S38B36 crankshaft. It had a longer stroke than original and defenately was not a B38 with 4 torq screw. instead of a screw it had a nut on front which according to ETK is not used in S38B36 engines. Pics here http://www.m5board.com/vbulletin/e34-m5-discussion/145193-winding-noise-rebuilt-engine.html


Your fuel pressure should be 3.0bar (for B36), B38 is 3.5 bar. Did you measure AFR with a wideband controller during WOT?

 

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Discussion Starter #5 (Edited)
Idle @ 0deg is fine for this type of engine. See attachment. It might deviate from listed due to other factors (idle regulation in DME adjust ignition and ICV according to circumstances).
If your Reference mark sensor comes over to the mark on the timing cover and the piston is in TDC (remove spark plug and use a long screwdriver or whatever you prefer.

I had an engine in with some similair "adjustments". The timing damper in front was set differently due to a non S38B36 crankshaft. It had a longer stroke than original and defenately was not a B38 with 4 torq screw. instead of a screw it had a nut on front which according to ETK is not used in S38B36 engines. Pics here http://www.m5board.com/vbulletin/e34-m5-discussion/145193-winding-noise-rebuilt-engine.html


Your fuel pressure should be 3.0bar (for B36), B38 is 3.5 bar. Did you measure AFR with a wideband controller during WOT?

As i stated in my first post, i did verify that the marker on the damper is a true TDC with a degreewheel and a rod on the piston + dial gauge. The mark on the damper is on the one on the cover @ idle.
I dont know if this will make any difference, but Pretoria is 1300m above sea level.
The fuel pressure is on 3bar when idleing and very small throttle, but 3.5bar at WOT.
The AFR @ WOT on the dyno measured in the regeon of 13:1 through the whole RPM range and almost 15:1 @ part throttle. I dont know what type it was, but the dyno facility had a lambda sensor in the back of the exhaust. Remember that the SA spec cars didnt have cats nor lambda sensors and the airpump was disconnected.
Still the question remains? why did the car hesitiate and now that it has 6 deg extra ignition timing through the whole range it doesnt hesitate anymore.
I have a very good "feel" for this type of thing, since no one ever felt what i feel when i want to show them. you can see on the dyno graph that the power dips slightly at 5500 rpm, so my "feeling" was not without substance.
Can the MAF influence timing?
 

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As i stated in my first post, i did verify that the marker on the damper is a true TDC with a degreewheel and a rod on the piston + dial gauge. The mark on the damper is on the one on the cover @ idle.
I dont know if this will make any difference, but Pretoria is 1300m above sea level.
You have a MAF based ecu. When air density is lower MAF will measure it and will adjust ignition timing and fueling.

+
The fuel pressure is on 3bar when idleing and very small throttle, but 3.5bar at WOT.
The AFR @ WOT on the dyno measured in the regeon of 13:1 through the whole RPM range and almost 15:1 @ part throttle. I dont know what type it was, but the dyno facility had a lambda sensor in the back of the exhaust. Remember that the SA spec cars didnt have cats nor lambda sensors and the airpump was disconnected.
Still the question remains? why did the car hesitiate and now that it has 6 deg extra ignition timing through the whole range it doesnt hesitate anymore.
Even for SA spec car your fuel pressure it to high. ETK states a 3.0bar fuel pressure sensor. Is your engine ECU modified/chipped?

I have a very good "feel" for this type of thing, since no one ever felt what i feel when i want to show them. you can see on the dyno graph that the power dips slightly at 5500 rpm, so my "feeling" was not without substance.
Can the MAF influence timing?
Can you post your dyno results? Do you have AFR logged with it? In which gear?
Primairy timing and fueling is calculated by rpm and load from MAF. So yes your MAF has a very big influence on timing/fueling.

The reason your engine reponds better with a 6 degree more timing in a 5500-6800rpm area might be due to bad fuel mixture. "A good ignition system is a tuners best friend".
Reasonance flap does not work in that rpm area while the engine operates best in that region (good efficiency). Also to much fuel will cause misfires, not only to lean...

In my opinion you are adjusting things while you have not found the root cause. Your engine should work fine with standard spec. Have you done any modifications?

I would start to check the fuel pressure regulator and look for false air leaks.

Good luck!
 

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Discussion Starter #7
You have a MAF based ecu. When air density is lower MAF will measure it and will adjust ignition timing and fueling.



Even for SA spec car your fuel pressure it to high. ETK states a 3.0bar fuel pressure sensor. Is your engine ECU modified/chipped?



Can you post your dyno results? Do you have AFR logged with it? In which gear?
Primairy timing and fueling is calculated by rpm and load from MAF. So yes your MAF has a very big influence on timing/fueling.

The reason your engine reponds better with a 6 degree more timing in a 5500-6800rpm area might be due to bad fuel mixture. "A good ignition system is a tuners best friend".
Reasonance flap does not work in that rpm area while the engine operates best in that region (good efficiency). Also to much fuel will cause misfires, not only to lean...

In my opinion you are adjusting things while you have not found the root cause. Your engine should work fine with standard spec. Have you done any modifications?

I would start to check the fuel pressure regulator and look for false air leaks.

Good luck!
1st - i checked all vacuum pipes and replaced almost all of them.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
2nd - The FPR is also a brand new one from the agents. The FPR is supposed to work like that. With the vacuum connected, it is 3 bar and 3.5 without.<o:p></o:p>
3rd - my engine and the ecu is standard (no chip) except for bigger valves that was fitted and the compression is slightly higher due to a necessary head skim.<o:p></o:p>
I don’t have the dyno graph anymore.<o:p></o:p>
I don’t understand what you are trying to say i.t.o the resonance flap, but while the car was on the dyno, i had the opportunity to see that it closes @ WOT below 4000RPM and again above 6700RPM.<o:p></o:p>
I know that it is supposed to run fine on std spec, but as you correctly pointed out, i cant get to the root cause.<o:p></o:p>
Thanks so far!!
 

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Well as standard, the car will run 14.7:1 (Stoich) fuelling pretty much everywhere when not at WOT (as triggered by the TPS sensor).

At WOT AFR should be 13.4ish at 1500rpm going richer with RPMs, typically as low as 10.5 - 11:1 from 5500rpm upwards.

If your logged AFR is leaner than this at WOT (And your WOT TPS switching is actually working)it would suggest an issue elsewhere.

If the MAF is reading lower loads than reality you would end up with leaner AFR and more spark advance.........
 

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Discussion Starter #10
Chris,

If you do not have any vacuum leaks than I wud bet on the fuel pump!;)
I have driven around for a whole day with a fuel pressure gauge 'T'ed into the fuel line and the pressure stays constant @ WOT from 1500rpm - redline.
Sub8 - Is the AFR of 13:1 @ WOT too low then?

When adjusting the allen screw in the MAF, does one alter the whole RPM baseline AFR, or is that ONLY for idling?
 

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13:1 is maybe a little on the lean side for a 3.6ltr at high RPM. They do not have sodium filled valves and as such have a lower maximum temp limit, the other concern would be catalyst durability but I see you don`t have any!

AFR for best torque would be around 12.5 - 13.2:1.

I was more making the comments to suggest that something is differernt from standard if your seeing that kind of AFR.
 

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Discussion Starter #13
As i stated 3 times now, the fuel pressure doesn't drop!! How else do you suggest i check the fuel pump?
Sub8 - I see that you have a Focus RS - Drove one for a whole month and loved it. The ///M is faster from 3rd gear upwards however. hehe
 

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I don`t own an RS, I was involved with the product development, lead for engine calibration.

If I owned one I would not have a drivers license left!

Relative performance of the m and the RS has been discussed elsewhere on here...........

How much bigger are your intake valves? This and the compression might be enough to throw the AFR out, even though the MAF would read higher airflow it may not calculate a correct cylinder charge.
 

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I think it is a good topic to ask.
I am starting to tune S38b36 in alpha-n setup. I have found on previous page a interesting information about timing, but it ends after 4000rpm...
Maybe someone can help with providing such data to start with? How it looks like at WOT through rev range?
I've read on this great forum, that big gains are mainly from proper timing, so i'am sure it is worth to spend more time on it...

Thanks in advance for any informations.
 
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