Dyno trouble shooting session of Z4M ESS VT - 525

[Gt4]

That sucks. Hope you are OK. Even low speed accident sometimes create back/neck problem.

One of my friend crashed his Lotus Seven a month ago and the next day a guy died at LCMT in a 997 GT3. This sport remains dangerous.

So the limp mode problem would be cause by the sensor on the brake booster? Wonder how hard it would be to disable it. I hope ESS will consider to disable it now for guys who track their car at least...

[GuidoK]

Originally Posted by gmd2003

Correct 7 . my mechanic has a BMW laptop , showed the specific brake booster fault code 2F65 , there is no generic OBD .
George

I think #7 is just a valve and not a sensor. I don't think it measures anything.

I don't know where 2F65 can originate. Maybe it's in the electrical connection to that valve? (so that the ecu measures its continuity or something like that)
The strange thing is that that valve is only present on the z4m. The e46 m3/m3csl dont have an electical valve there; just a normal passive non return valve I think.

2F65 is indeed a brand specific code: Brake booster, system check

[tikamak]

What is this brake booster responsible for ? anyone know?
Is it normal with a SC kit?

[GuidoK]

brake booster uses vacuum force to assist in force of braking.
The brake booster is the large round black pot mounted to the back of the engine bay

[tikamak]

Originally Posted by GuidoK

brake booster uses vacuum force to assist in force of braking.
The brake booster is the large round black pot mounted to the back of the engine bay

Then my accident could be due to a brake failure indeed, I felt my car just sliding with no braking potential

Could this be the case? check my Z4M crash thread.

[ZStig]

Damn George... damn...

[seank]

Originally Posted by GuidoK

I think #7 is just a valve and not a sensor. I don't think it measures anything.

I don't know where 2F65 can originate. Maybe it's in the electrical connection to that valve? (so that the ecu measures its continuity or something like that)
The strange thing is that that valve is only present on the z4m. The e46 m3/m3csl dont have an electical valve there; just a normal passive non return valve I think.

2F65 is indeed a brand specific code: Brake booster, system check

That is the code that I have and I thought I was the only one. So, what is the fix is the question????????????

[Steeler]

I had the orange brake light come on on my car on Saturday as well as the ABS orange warning light during a car cruise in Detroit.
The brakes seemed to work as normal but I was not driving at speed either.
Turning the ignition off and on cleared the light from the dash and all seemed normal after.
My car is boosted with a VF kit.

[GuidoK]

Originally Posted by seank

That is the code that I have and I thought I was the only one. So, what is the fix is the question????????????

If both you and gmd2003 have the same code it's related to ESS' ecu tune or the supplied hardware.
The chances of both having the same problem (expecially such a code, this is not a common problem!) after the install and unrelated to the instal are....probably 0%

It seems to me the fix has to come from ess....

Normally i'd say that that code is maybe related to the DSC/ABS. There are 2 pressure sensors on the master cilinder itself. Maybe they can measure if something's wrong with the vacuum.

But that has nothing to do with the sc install.
I think it's an ECU/tuning problem and not a hardware problem.

[ZStig]

I know the throttle position sensor can so get the car to act funny, but it will throw a very specific code

[StickMon]

I don't have FI, so I don't have any skin in this game, but I am a Rocket Scientist, so I can't help but make a basic observation.
If you're running positive manifold pressure, where do you get vacuum for the power brake booster?
Granted you don't have positive manifold pressure all the time, and the check valve should allow the brake booster to store vacuum, but if it leaks just a little, and if you brake while you have positive manifold pressure and use it up ...
low vac in the brake booster, warning light, "life saving" (lawyer thwarting) limp mode, and possible actual weak power braking.

If you're driving "aggressively", you're kinda playing the odds. Especially if you heel-toe.
Are you producing as much vacuum as you're consuming?

[tikamak]

Originally Posted by StickMon

I don't have FI, so I don't have any skin in this game, but I am a Rocket Scientist, so I can't help but make a basic observation.
If you're running positive manifold pressure, where do you get vacuum for the power brake booster?
Granted you don't have positive manifold pressure all the time, and the check valve should allow the brake booster to store vacuum, but if it leaks just a little, and if you brake while you have positive manifold pressure and use it up ...
low vac in the brake booster, warning light, "life saving" (lawyer thwarting) limp mode, and possible actual weak power braking.

If you're driving "aggressively", you're kinda playing the odds. Especially if you heel-toe.
Are you producing as much vacuum as you're consuming?

I think that the blow off valve is responsible to restore the vacuum state after removing your foot from the throttle.

But i understand what you're saying.

[dre99gsx]

With a turbo charger, as soon as your off the gas, you are in vacuum, even more so when decelerating. Since your blow off valve goes off relieving the intake tract pressure, as well as your exhaust energy dwindling, reducing turbo charger rotation, thus eliminating any chances of boost.

With a supercharger, she is always in boost, even when you let off the gas. The bypass valve will bleed off all of this extra air to atmosphere in a long deceleration. There should also be a one way valve into the booster. If either the bypass valve or one way valve malfunction, and you get pressure (or loss of vacuum) into the booster, you are essentially running "booster-less".

Still, you should be able to apply enough manual braking force to slow down a vehicle in that situation.

I would recommend installing a secondary one-way valve into the booster as a precaution. Us Supra guys come with a large one way valve right at your disposal going into the booster itself.

Also, I don't believe the Z4M has an accumulator? There are vehicles with vacuum storage canisters for an extra supply of vacuum. If you don't supply additional vacuum to a brake booster, you have limited amount of braking "presses" before it stiffens up.

As an aside, the M3 crowd has been Supercharging/ESS'ing for quite some time. Any input on their regarding brake booster modifications (since they have similar engines)?

[GuidoK]

Originally Posted by StickMon

I don't have FI, so I don't have any skin in this game, but I am a Rocket Scientist, so I can't help but make a basic observation.
If you're running positive manifold pressure, where do you get vacuum for the power brake booster?

Originally Posted by tikamak

I think that the blow off valve is responsible to restore the vacuum state after removing your foot from the throttle.

The creation of vacuum is the same as with a NA car. The moment the TB's close, the cilinders behind it draw vacuum. That's where your vacuum comes from (both NA and FI; both cars have a TB and cilinders )

Further more a bmw has a 'jet suction pump' which is a device that can draw extra vacuum by means of the venturi effect. (in theory the jet suction pump could draw vacuum when the tb's are open, but I don't know if that also effectively happens irl.)
The jet suction pump uses a small bypass around the tb to create a small airflow to the cilinders.
The strange thing is: the z4m has an electrically controlled valve between that, so the ecu can stop that flow and so stop the jet suction pump from functioning. Why is that. No other bmw has that, even not the the e46 m3 or m3csl (which presumably has exactly the same engine).

[Beedub]

Think ESS could do with chiming in here tbh..... it really needs their input....

[seank]

Originally Posted by Beedub

Think ESS could do with chiming in here tbh..... it really needs their input....

Agreed. It is an issue that needs to be resolved.

[tikamak]

Originally Posted by seank

Agreed. It is an issue that needs to be resolved.

+1

We're wandering off with theories while ESS can simply come and tell us the full story just like that.

[gmd2003]

Originally Posted by seank

Agreed. It is an issue that needs to be resolved.

I'm still waiting to hear from AJ . I will let everyone know what we come up with . I know others have had the yellow brake light limp on track . The frustrating thing is it seems like it can occur from temp as well as possibly other sources. One thing I know for sure my brake booster was 100% great pedal feel no fade as usual with my PFC brakes . This time my oil temps were in the 240 range with water temps in the high 210's so temp doesn't make sense either . The real issue is the nature if the limp . A complete cut of the throttle . In my case it caused a wreck , and if I can't be sure it's 100% taken care of I am going to have to get rid of a car I've put a Ridiculous amount of money into setting up for the track .

[Gt4]

Same thing here, I will most probably go back NA with my car in a near future and if the problem still happen, I might sell the car to get an E46 M3 and swap all my goodies on it.

Or maybe consider a Motec/AIM Pectel T2/KMS ...

[gmd2003]

Originally Posted by Gtfour

Same thing here, I will most probably go back NA with my car in a near future and if the problem still happen, I might sell the car to get an E46 M3 and swap all my goodies on it.

Or maybe consider a Motec/AIM Pectel T2/KMS ...

Please tell ESS you have had the same issue , they keep telling me I'm the only car they have ever heard of this happening which is not the case .

[tikamak]

Originally Posted by gmd2003

Please tell ESS you have had the same issue , they keep telling me I'm the only car they have ever heard of this happening which is not the case .

I sent a Mail to AJ.
I hope he replies to this thread with his feedback.

[Gt4]

Originally Posted by gmd2003

Please tell ESS you have had the same issue , they keep telling me I'm the only car they have ever heard of this happening which is not the case .

Give me an email address and I will contact them.