E39 540i low compression

Mr540i....

In regard to the output of the centrifugal SCr my point was and is that its pressure output is not linear. Its exponential. That is due to the exhaust and intake air that 'leaks' around the edges of the turbine wheels. As the speed of the turbine wheels increases the relative air leakage decreases. The graphs that you posted are hp and torque curves and are not the compressor pressure output graphs of the SCrg.

The hp and torque curves you posted show the combination of the engine's normal aspirated power curve and the added power from the SCr.

What I was saying about a Centrifugal SCrs pressure curve and your posted power output graphs/curves are two very different things.

540alex, have you made any more progress on fixing the issues you still had when you last posted? I've been reading this thread in my spare time and now that I'm finally to the end of it it's sad hahaha

Originally Posted by blz456

540alex, have you made any more progress on fixing the issues you still had when you last posted? I've been reading this thread in my spare time and now that I'm finally to the end of it it's sad hahaha

I haven't done anything on the car probably almost since the last time I posted until about a week ago, which is several months . I had to get the mandated by the wife front yard project out of the way and had to travel for work several times.

The car runs 'fine' except for the missing boost part. I finally started working on it again, yesterday had a compression test done and was pleased to find that the original issue has been fixed:

#4 - 208 #8 - 208
#3 - 208 #7 - 206
#2 - 206 #6 - 205
#1 - 208 #5 - 206

Also tried testing the intake for leaks starting at the throttle body, filled the entire intake with smoke, but did not see it come out anywhere, and the boost gauge was showing what seemed to be correct pressure - about 6 psi. But I'm not so confident in the test itself, because I created a deliberate leak before the throttle body, could hear the air hissing, but no smoke... I'm guessing the smoke isn't dense enough to make it through the small hole? I'm going to to some modifications to the S/C side of the intake to eliminate some iffy parts and go from there.

Alex, I've never done a smoke test, but when you say the smoke wasn't "dense enough to make it through the hole," a possibility comes to mind. Increased density shouldn't affect the ability of smoke to escape through a hole. Assuming you're saying the hissing sound occurred during the smoke test, maybe the smoke made it through the hole but wasn't dense enough to be seen. If the hissing sound occurred while you were running the engine, the smoke test might not have produced enough pressure to force out a visible amount of smoke. Otherwise, it seems like a pretty mysterious result.

By the way, it was really smart of you to finish the yard project before you got back to the car. It will make your life a smoother ride, metaphorically speaking.

Hey Bob!

Yes, I meant during the smoke test. It's possible that I just did not see it, although in this case I knew exactly where to look for it.

Alex.

Can you control the density of the smoke? How about the visibility? For instance, is there some way to add a color to it?

Smoke is comprised of very small particles and should make it thru any hole. But like said above there maybe not be enough of the smoke coming thru the hole to actually see it.

Originally Posted by bobdmac

Can you control the density of the smoke? How about the visibility? For instance, is there some way to add a color to it?

Originally Posted by franka

Smoke is comprised of very small particles and should make it thru any hole. But like said above there maybe not be enough of the smoke coming thru the hole to actually see it.

Maybe I wasn't patient enough and maybe I should have done this indoors. I could make more smoke overtime, just needed to wait longer, maybe then I would see it, but I was short on time, needed to fix a couple of coolant leaks (the radiator nipple broke off ), replace belts (A/C belt disintegrated on me).

The blow off valve is my main suspect now for the lack of boost, the plan is to replace it with another type.

Originally Posted by 540alex

The blow off valve is my main suspect now for the lack of boost, the plan is to replace it with another type.

I agree that's a good candidate as a trouble spot on a used supercharger with God-knows-how-many-miles on it.

As most of you know, we try to pick an existing thread to make canonical, and then add references to new information to that one canonical thread (for reference efficiency), so I'm going to (relatively arbitrarily) list these two threads as the ones to go to for compression testing:

For the V8: > E39 (1997 - 2003) > E39 540i low compression
For the I6: > E39 (1997 - 2003) > compression test results I6 M54

In the bestlinks, I'll put this:
- How to test compression on a BMW E39 V8 engine (1) and on the I6 engine (1)

Originally Posted by champaign777

Results of my compression test, 2003 530i 95k miles :

#1-135
#2-132
#3-130
#4-132
#5-133
#6-130

Just so this thread is complete...

The low compression has been fixed by the valve job that I had done at Morgan's Machine & Speed in Walnut Creek. They've reseated the valves, adjusted the springs, resurfaced the heads and slightly ported them. Very happy with how they handled everything and the job they did.

The car is running great, but still has some issues. I learned to live with one of them, which is the car runs very poor for the first minute or so after it's been cold for a while. When the car is warm and is in the closed loop, the problem goes away. My guess is that Dinan did not spend much time tuning the open loop operation since it's only temporary.

The other issue is the car REALLY likes it when it's cold outside and runs the best at low temperatures. By low I mean around 55 and lower. Anything above that gets gradually worse, but only noticeable at high acceleration at high RPM. Dyno showed that the power suddenly drops after 4000 RPM and then comes back later at around 5500 RPM. The drop was almost gone when I dynoed with 100 octane fuel, it also goes away when it's cold out. The theory is that when it's warm enough outside, the air after the S/C under high load gets too hot and the fuel starts detonating, computer senses it and cuts the power.

Soooo.... the next project in the works - intercooler