Miatapower List Archive

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Mail From: (email redacted)


So this may sound kinda stupid, but is the BOV equally necessary for Aerodyne
turbo applications as it is for the Garrett systems? I'm planning on playing
with removing my BOV and temporarily capping the pipes off to see what the
differences are.

It is my understanding that the early aerodyne kits for the miata did not
include BOVs. Can anyone confirm this? If so, any comments on how the car
drives w/o the BOV?

Just curious. I'll probably try it out this Saturday when I have time.

Thanks,
Lee

This read-only message was archived from a public mail list.
Mail From: "Ralph Alder" <(email redacted)>



-----Original Message-----
From: (email redacted) <(email redacted)>
Subject: BOV for Aerodyne turbo systems


>
>So this may sound kinda stupid, but is the BOV equally necessary for
Aerodyne
>turbo applications as it is for the Garrett systems? I'm planning on
playing
>with removing my BOV and temporarily capping the pipes off to see what the
>differences are.
>
>It is my understanding that the early aerodyne kits for the miata did not
>include BOVs. Can anyone confirm this? If so, any comments on how the car
>drives w/o the BOV?



Interesting question, Lee. My early Aerodyne did not have a BOV. A year
ago there was a lot of discussion about BOVs and I decided to add one. Did
it make a difference? If it did, it is small. I consider pulling the
signal line to see what difference it makes, every once and a while but
haven't done it. Unless you are running a lot more boost than my 8 psi, I
think that the BOV should resist the boost presure OK and remain closed...or
Tee the signal line into the upstream of the throttle valve so it sees only
boost presure.

I certainly didn't see any great decrease in turbine spool-up time when
shifting. It may have decreased it but it's pretty short anyway and it
might not be very noticible.


>
>Just curious. I'll probably try it out this Saturday when I have time.
>
>Thanks,
>Lee
>

This read-only message was archived from a public mail list.
Mail From: Ray Ayala <(email redacted)>


This matches my experience. I believe that the reason is
because the Aerodyne spools down during shifts anyway (even
with a BOV) when the actuator sees a vacuum on the demand
line (the one closest to the turbo body). This could be
prevented by connecting the demand line to the IC side of
the throttle, but you might not want to do it because of the
risk of redlining when the turbo tries to hold the boost up
with the BOV open. - Ray

Ralph Alder wrote:
>
> -----Original Message-----
> From: (email redacted) <(email redacted)>
> Subject: BOV for Aerodyne turbo systems
>
> >
> >So this may sound kinda stupid, but is the BOV equally necessary for
> Aerodyne
> >turbo applications as it is for the Garrett systems? I'm planning on
> playing
> >with removing my BOV and temporarily capping the pipes off to see what the
> >differences are.
> >
> >It is my understanding that the early aerodyne kits for the miata did not
> >include BOVs. Can anyone confirm this? If so, any comments on how the car
> >drives w/o the BOV?
>
> Interesting question, Lee. My early Aerodyne did not have a BOV. A year
> ago there was a lot of discussion about BOVs and I decided to add one. Did
> it make a difference? If it did, it is small. I consider pulling the
> signal line to see what difference it makes, every once and a while but
> haven't done it. Unless you are running a lot more boost than my 8 psi, I
> think that the BOV should resist the boost presure OK and remain closed...or
> Tee the signal line into the upstream of the throttle valve so it sees only
> boost presure.
>
> I certainly didn't see any great decrease in turbine spool-up time when
> shifting. It may have decreased it but it's pretty short anyway and it
> might not be very noticible.
>
> >
> >Just curious. I'll probably try it out this Saturday when I have time.
> >
> >Thanks,
> >Lee
> >

This read-only message was archived from a public mail list.
Mail From: (email redacted)


In a message dated 99-07-14 17:10:20 EDT, (email redacted) writes:

<<
So this may sound kinda stupid, but is the BOV equally necessary for
Aerodyne
turbo applications as it is for the Garrett systems? I'm planning on
playing
with removing my BOV and temporarily capping the pipes off to see what the
differences are.

It is my understanding that the early aerodyne kits for the miata did not
include BOVs. Can anyone confirm this? >>

Correct, we left them out with the lower boost systems for the Aerodyne.
Interestingly, the Aerodyne has a much better compressor for making boost at
low flow rates than virtually any other turbo. Obviously it had too, to take
advantage of the VATN feature. This characteristic, in large part, determines
the need of a surge valve. With the surge agravation of big intercoolers
and higher boost, even the Aerodyne couldn't avoid surge on lift-off.
CB

This read-only message was archived from a public mail list.
Mail From: Martin Eby <(email redacted)>


A couple of questions from somebody new to BOVs:

1) Why is it desirable to put the BOV close to the turbo rather than after
the IC? It seems to me that you'd want it as far downstream as possible so
that 1) it stays cooler, 2) the pressure it sees on the intake side is
somewhat modulated by the volume of air between the turbo and the BOV, and
3) there is a smaller volume of air following the BOV which should give
quicker and more direct throttle response. Clearly, I'm missing some key
bit of understanding or experience here, but what?

2) How is the Aerodyne different from conventional turbos? Is there a
website I could visit that would explain it?

3) What VATN feature?

Thanks in advance,

Martin


At 09:04 AM 7/15/99 EDT, (email redacted) wrote:
>
>In a message dated 99-07-14 17:10:20 EDT, (email redacted) writes:
>
><<
> So this may sound kinda stupid, but is the BOV equally necessary for
>Aerodyne
> turbo applications as it is for the Garrett systems? I'm planning on
>playing
> with removing my BOV and temporarily capping the pipes off to see what the
> differences are.
>
> It is my understanding that the early aerodyne kits for the miata did not
> include BOVs. Can anyone confirm this? >>
>
>Correct, we left them out with the lower boost systems for the Aerodyne.
>Interestingly, the Aerodyne has a much better compressor for making boost at
>low flow rates than virtually any other turbo. Obviously it had too, to take
>advantage of the VATN feature. This characteristic, in large part,
determines
>the need of a surge valve. With the surge agravation of big intercoolers
>and higher boost, even the Aerodyne couldn't avoid surge on lift-off.
>CB
>
>

This read-only message was archived from a public mail list.
Mail From: "Steve McGrane" <(email redacted)>


For the BOV question, you will have to wait, but the
aerodyne questions are quite simple to answer.

1. performancebuyers.com/engine/aerodyne.htm

2. VATN is Variable Area Turbine Nozzle, and what that means
is that the turbine blades change pitch so that with less
exhaust gasses at lower RPMs, it produces a relatively high
amount of boost, and then as RPMs increase, the pitch
changes to maintain a steady amount of boost.

Turbo's are turned by exhaust gasses and at low RPMs, there
isn't much exhaust, that is why there is turbo lag, as
exhaust gasses build, the turbo spins faster. In a Miata,
there isn't much below 3k, the VATN capitalizes on this
fact, for details check out the CDMDDIII pages for some dyno
charts and you will see the difference:

rampages.onramp.net/~bookworm/dynosum.html

an Aerodyne at 2.5k has ~73hp, an FMII has ~60hp, stock has
about 45hp and a supercharger has ~75hp (these are all
1.8's). after 2.5k, it is really up to your surrounding
components where your hp goes (Intercooler, ECU, etc...)

Did that help?

-----Original Message-----
From: (email redacted)
[mailto:(email redacted)]On Behalf Of Martin
Eby
Sent: Thursday, July 15, 1999 10:10 AM
To: (email redacted)
Subject: Re: BOV for Aerodyne turbo systems



A couple of questions from somebody new to BOVs:

1) Why is it desirable to put the BOV close to the turbo
rather than after
the IC? It seems to me that you'd want it as far downstream
as possible so
that 1) it stays cooler, 2) the pressure it sees on the
intake side is
somewhat modulated by the volume of air between the turbo
and the BOV, and
3) there is a smaller volume of air following the BOV which
should give
quicker and more direct throttle response. Clearly, I'm
missing some key
bit of understanding or experience here, but what?

2) How is the Aerodyne different from conventional turbos?
Is there a
website I could visit that would explain it?

3) What VATN feature?

Thanks in advance,

Martin


At 09:04 AM 7/15/99 EDT, (email redacted) wrote:
>
>In a message dated 99-07-14 17:10:20 EDT,
(email redacted) writes:
>
><<
> So this may sound kinda stupid, but is the BOV equally
necessary for
>Aerodyne
> turbo applications as it is for the Garrett systems? I'm
planning on
>playing
> with removing my BOV and temporarily capping the pipes off
to see what the
> differences are.
>
> It is my understanding that the early aerodyne kits for
the miata did not
> include BOVs. Can anyone confirm this? >>
>
>Correct, we left them out with the lower boost systems for
the Aerodyne.
>Interestingly, the Aerodyne has a much better compressor
for making boost at
>low flow rates than virtually any other turbo. Obviously it
had too, to take
>advantage of the VATN feature. This characteristic, in
large part,
determines
>the need of a surge valve. With the surge agravation of
big intercoolers
>and higher boost, even the Aerodyne couldn't avoid surge
on lift-off.
>CB
>
>

This read-only message was archived from a public mail list.
Mail From: "Ralph Alder" <(email redacted)>



-----Original Message-----
From: Martin Eby <(email redacted)>
Subject: Re: BOV for Aerodyne turbo systems


>
>A couple of questions from somebody new to BOVs:
>
>1) Why is it desirable to put the BOV close to the turbo rather than after
>the IC? It seems to me that you'd want it as far downstream as possible so
>that 1) it stays cooler, 2) the pressure it sees on the intake side is
>somewhat modulated by the volume of air between the turbo and the BOV, and
>3) there is a smaller volume of air following the BOV which should give
>quicker and more direct throttle response. Clearly, I'm missing some key
>bit of understanding or experience here, but what?

Possibily the most significant reason is the ease of re-directing the excess
pressure back to the turbo inlet...required for those with stock ECUs. I'll
let other more knowledgeable types comment on the other aspects.

>
>2) How is the Aerodyne different from conventional turbos? Is there a
>website I could visit that would explain it?
>
>3) What VATN feature?

Steve's post was a good basic description of the VATN. For the best source
of info you need to get Corky Bell's book "Maximum Boost". If you are at
all interested in things Turbo, this book is a necessity. It also has the
best photos and description (complete with cutaway photos and cross-section
drawings) of the Aerodyne that I've found. Even has a complete description,
with photos, of an installation on a Miata or, if you want to get really
esoteric, a twin-Aerodyne installation on a NSX.

Disclaimer: I have no fiduciary ties with BEGI, Mr. Bell, or Aerodyne,
other than as a turbo owner and "fan". ;-)

Ralph Alder
Tustin, CA
'90 Classic Red w/Yellow Stripes
Team Aerodyne

This read-only message was archived from a public mail list.
Mail From: (email redacted)


>So this may sound kinda stupid, but is the BOV equally necessary for Aerodyne
>turbo applications as it is for the Garrett systems? I'm planning on playing
>with removing my BOV and temporarily capping the pipes off to see what the
>differences are.
>
>It is my understanding that the early aerodyne kits for the miata did not
>include BOVs. Can anyone confirm this? If so, any comments on how the car
>drives w/o the BOV?
>
>Just curious. I'll probably try it out this Saturday when I have time.
>
>Thanks,
>Lee

Interestingly, my Aerodyne didn't need a BOV until I added the intercooler
and extra piping. Then it started hammering...

-Joseph