VANOS Question

I have the M50 motor with VANOS. What does VANOS do, and what hazppens if it
isn't doing it right?

My engine used to have a kick similar to the feeling when the secondaries
open in a 4bbl carb. I had the head replaced and have always felt that since
then that this kick just isn't there anymore. I have also suspected that my
low-end torque just isn't there.

I thought that VANOS was an adjustment to the valve timing that helped with
the low-end torque and high speed accelleration.

My car runs fine, except for the perceived flatness in the power curve. Is
this a symptom of the VANOS system not working right?

"Jeff Strickland" > wrote in message
...
>I have the M50 motor with VANOS. What does VANOS do, and what hazppens if
>it
> isn't doing it right?
>
> My engine used to have a kick similar to the feeling when the secondaries
> open in a 4bbl carb. I had the head replaced and have always felt that
> since
> then that this kick just isn't there anymore. I have also suspected that
> my
> low-end torque just isn't there.
>
> I thought that VANOS was an adjustment to the valve timing that helped
> with
> the low-end torque and high speed accelleration.
>
> My car runs fine, except for the perceived flatness in the power curve. Is
> this a symptom of the VANOS system not working right?
>
>

Jeff,

Yeah what you describe as being missing could be the VANOS not working.

The way VANOS works is there is an electric solenoid that moves a valve to
either route or block the oil pressure from reaching the mechanical VANOS
advance unit. As best I can recall, when the oil pressure is routed to the
actuator it pushes the camshaft sprocket on a spiral cut gear assembly which
makes it become more advanced. So it does tend to "kick-in" like you
describe at the rpm that the DME energizes the solenoid.

You don't say what year engine you have, but with single VANOS (like I have
on my '95) it is a pretty subtle difference. You can unplug the solenoid's
connector and see if there is any perceptible difference. Obviously there
should be.

Here is a little info on VANOS:

http://www.bmwworld.com/technology/vanos.htm

-Fred W

It's a '94.

Single vs Double??? Does one control both the intake and exhaust timing at
the same time - or maybe only one of them (presumably intake) - where the
other controls intake and exhaust timing independently?

I am certain I have the single VANOS in a '94, but I wonder what the
difference is in single and double ...


Since you have given me a sanity check on what VANOS ought to be doing, I am
going to check into it closely next weekend when I do my quartly service
work. Thanks.





"Fred W." <Fred.Wills@'remove this to reply to' myrealbox.com> wrote in
message ...
>
> "Jeff Strickland" > wrote in message
> ...
>>I have the M50 motor with VANOS. What does VANOS do, and what hazppens if
>>it
>> isn't doing it right?
>>
>> My engine used to have a kick similar to the feeling when the secondaries
>> open in a 4bbl carb. I had the head replaced and have always felt that
>> since
>> then that this kick just isn't there anymore. I have also suspected that
>> my
>> low-end torque just isn't there.
>>
>> I thought that VANOS was an adjustment to the valve timing that helped
>> with
>> the low-end torque and high speed accelleration.
>>
>> My car runs fine, except for the perceived flatness in the power curve.
>> Is
>> this a symptom of the VANOS system not working right?
>>
>>
>
> Jeff,
>
> Yeah what you describe as being missing could be the VANOS not working.
>
> The way VANOS works is there is an electric solenoid that moves a valve to
> either route or block the oil pressure from reaching the mechanical VANOS
> advance unit. As best I can recall, when the oil pressure is routed to
> the actuator it pushes the camshaft sprocket on a spiral cut gear assembly
> which makes it become more advanced. So it does tend to "kick-in" like
> you describe at the rpm that the DME energizes the solenoid.
>
> You don't say what year engine you have, but with single VANOS (like I
> have on my '95) it is a pretty subtle difference. You can unplug the
> solenoid's connector and see if there is any perceptible difference.
> Obviously there should be.
>
> Here is a little info on VANOS:
>
> http://www.bmwworld.com/technology/vanos.htm
>
> -Fred W
>

CRWLR wrote:
>
> It's a '94.
>
> Single vs Double??? Does one control both the intake and exhaust timing at
> the same time - or maybe only one of them (presumably intake) - where the
> other controls intake and exhaust timing independently?

Single VANOS is inlet cam only; double VANOS, both cams. '94 is single
cam.


> Since you have given me a sanity check on what VANOS ought to be
> doing, I am going to check into it closely next weekend when I do my
> quartly service work. Thanks.

The best way to see if it's working is when accelarating in 3rd gear
with a steady throttle. At 3500 rpm it should start accelarating faster
as the VANOS unit reverts to the normal cam timing.

--
Scott

Where are we going and why am I in this handbasket?

"Scott M" > wrote in message
...
> CRWLR wrote:
> >
> > It's a '94.
> >
> > Single vs Double??? Does one control both the intake and exhaust timing
at
> > the same time - or maybe only one of them (presumably intake) - where
the
> > other controls intake and exhaust timing independently?
>
> Single VANOS is inlet cam only; double VANOS, both cams. '94 is single
> cam.
>
>
> > Since you have given me a sanity check on what VANOS ought to be
> > doing, I am going to check into it closely next weekend when I do my
> > quartly service work. Thanks.
>
> The best way to see if it's working is when accelarating in 3rd gear
> with a steady throttle. At 3500 rpm it should start accelarating faster
> as the VANOS unit reverts to the normal cam timing.
>

That's the feeling of the 4bbl carb Secondaries Opening that I felt when I
bought the car, but that I think is now missing. The only analogy I can
think of is that of the secondaries on a 4bbl, I am certain the analogy is
pretty good, but not exact. Another analogy that is equally flawed is the
feeling of the turbo coming on line.

I do feel the accelleration under those conditions - 3rd gear at about 3000
RPM - get stronger, but the feeling is more like that of the power and
torque curves coming together, it is not a kick like occurs when the turbo
comes on line or the secondaries kick in on the old V8 muscle cars of yore.