BMW M5 Forum and M6 Forums banner

41 - 56 of 56 Posts

·
Moderator
Joined
·
2,179 Posts
I'm pretty sure pressure targets are the same for both US and euro smg tunes. Target pressures are temp-dependent tho. Did you take fluid temperature into account when doing your tests?
 

·
Registered
Joined
·
499 Posts
Discussion Starter #42
I was watching the temp, rise of course. As I went through each setting I would allow it to cycle a few times to confirm the pressures. When I got home in the driveway with hot oil the pressures were the same as when I started for a given setting.

If you have a map of settings to look at that would be interesting to compare with my observations. If the pressure sensor were bias that would effect the system. When I did a bleed down it did drop to 1.5bar which is pretty close considering the range.
 

·
Moderator
Joined
·
2,179 Posts
Have you seen this?

 

·
Registered
Joined
·
499 Posts
Discussion Starter #44
I have not seen that. It's way above my level of programming. It seems like they were just doing it to do it no real reason that I could see?

I took a closer look at the cooling and there are already two ports in the under-body to feed air to both sides of the transmission. Some of the heat shielding for the exhaust was bent and obstructed the air flow, I corrected that.

I went for another drive yesterday, INPA running in the passenger seat. More bars more pressure, S6 cycling is frequent. It was a causal drive and cool with some rain. Temp was up to 83c at the end of the drive and the cycle time in S4 was 15sec. Has anyone else watched there pressures and temperatures on the SMG?
 

·
Registered
Joined
·
499 Posts
Discussion Starter #49
So I made it to the track today. The short story is the transmission faulted again. S3 the whole time.
Now the long story,
I arrived at 1100 but did not go on the track until 1220 so the car had time to cool off. I have had no faults on the street since going back to the US SMG tune. I went out for about 20 minutes with no problems. I came in to check an set the tire pressures with the car running. As soon as I got 1/2 lap back on the track the trans faulted.
I drove off the track at about 1pm and let the car cool off until 2:20. Went out with the temp at 80c and ran 20 minutes just fine(temp at 104c). Let the car cool off for about 20 minutes and headed back out for the final run. Got about 15 minutes in and got another trans fault.
I was pretty happy with my time on the track and called it a day. The next order of business is going to be the accumulator and clutch solenoid.
 

·
Registered
Joined
·
499 Posts
Discussion Starter #50
This will wrap up this thread for me.

I got inspired to dig into the HPU before going to the track today. I ordered o-rings for the clutch solenoid and pump, rebuilt accumulator, pressure and temp sensors and of course fresh oil. I did all the work with the trans and exhaust in place, I would not recommended it. Inspecting the o-rings on the clutch solenoid they had small frayed edges, this was observed under a powerful magnifying glass. The accumulator, pump o-rings and sensors were done just because I was there I do not believe they were necessary. Here is a video of the inside of the pump, nothing special just keep it in order if you rebuild it. I had no trouble bleeding and testing after the work.


So the pump cycling is significantly less, 5 minutes at 24c in neutral. The big change was after the test drive, 2 minutes at 87c. Before the times were 2 minutes at 17c and 15 seconds at 80c. I think the solenoid o-rings made the difference. When I did the motor I should have done the solenoid o-rings at the same time. As our SMG's age this will be and ongoing issue. I think step one is the motor, pump, clutch solenoid, accumulator and sensors. Step two is the valve body and wiring which will come this winter. As for the oil based on my research stay with factory oil. There are other options but none with a viscosity index anywhere near factory. In other words to get a higher hot viscosity you would have to use a very high cold viscosity. I left the skid plate off to see if the SMG stays cooler, based on the test drive I doubt it.

As for the Euro SMG tune and the shift settings. The tune will stay out, it definitely caused more problems. The shift settings will stay at S3. This lowers the pressures, if you want quick shifts the engine torque calculations will make the SMG shift hard. Back to the track thread after today.
 

·
Registered
Joined
·
316 Posts
Basically you are thinking the hydraulic fluid is getting too hot, correct?

In my SMG doldrums I have wondered about running a cooler in the return line to the reservoir....its the rubber line from top hydraulic block to reservoir. Have you considered that?
 

·
Registered
Joined
·
748 Posts
As long as it is still a fluid, it will still transmit pressure and operate the valves. What could happen with very hot fluid is that it bypasses/leaks more because the orings become more malleable and it they are torn more fluid bypasses. I've seen my orings torn on the outer edges when I replaced them, seems to be the same as what Alan and others have mentioned, it doesn't really show up in a photo. I'm in the process of refurbing mine, but making little progress as it's too hot and humid to be doing much wrenching. Not looking forward to getting the trans mounted back in the car.

Viscosity of the oil effects the pumpability, but that doesn't seem to be the issue you are dealing with.
 

·
Moderator
Joined
·
2,179 Posts
@Alan Arnesen obviously there was a bit of leakage through orings and what not given the pump cycle time. But since you had a code at the track again I'm wondering if you filed the pump brushes or not?
 

·
Registered
Joined
·
499 Posts
Discussion Starter #54
I will look into the cooling option when the trans comes out, it would not hurt but does not solve the worn o-rings.

I did not file the brushes but in my defense I did have INPA running and the pressure and pump cycling was okay. That's why I ran the adaptations again. With new o-rings in the clutch solenoid it would respond differently to the SMG controller input. I doubt the saga will ever end without a new unit. For now with the US tune it has been working fine. I may go back to the Euro tune during the winter just to see if it makes more trouble again.
 

·
Registered
Joined
·
499 Posts
Discussion Starter #56
Around town 80+, at the track 105+. I just took a long drive to and from the PCA/PNW CCC and did some autocross while I was there and had no problems.
 
41 - 56 of 56 Posts
Top