[Diy_efi] Re: Question about speed density, etc.

[Eric D Byrd]

I think it's six of one, half a dozen of the other... control boost with
MAP, and your wastegate will just open more to compensate if you give it
more throttle, making your turbo work a little less hard.  The problem
with this scheme is, you don't really want full boost to be available at
partial throttle, do you?  The reason turbos are more efficient than
higher displacement, is that they don't boost until you ask them to,
i.e., don't build full boost until, ideally, you want more than your
engine will provide NA.  That's why the intake tract is the best place
for a controller pick up, before the TB.  Then you tune the wastegate to
provide the maximum boost that is safe for your engine, with the fuel you
are using.  Then, at partial throttle, your car is operating with the
fuel efficiency of NA, more or less, but when you want the boost, full
throttle will give it to you.  If you have full boost at partial
throttle, it seems to me your turbo is too small.

On Tue, 29 Oct 2002 11:40:31 -0800 (PST) Adam Wade
<espresso_doppio at yahoo.com> writes:
> --- Nick Starai <true at ItsYourDomain.com> wrote:
> 
> > I've also wondered the same thing. I've got my MAP
> > source for my boost controller on the Surge tank
> > (after throttle plate). I can build full boost at
> > partial throttle...and wondered if 100% at this
> > point will do anything at all. Isn't the compressed
> > air basically sitting in the intake manifold waiting
> > for the valves to open at this point anyways? Will
> > a 100% open throttle plate even allow more air in?
> 
> If you are electronically limiting the intake pressure
> based on your MAP sensor and an
> electronically-controlled waste gate, no; once you
> reach maximum MAP, changing the throttle won't matter;
> max MAP is max MAP if your system has a hard limit on
> it.  CLOSING the throttle should reduce the MAP, but
> opening it more will simply cause the ECU to "turn
> down" the boost by opening the wastegate more.
> 
> =====
> | Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
> |   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
> | "It was like an emergency ward after a great catastrophe; it  |
> |   didn't matter what race or class the victims belonged to.   |
> |  They were all given the same miracle drug, which was coffee. |
> |   The catastrophe in this case, of course, was that the sun   |
> |     had come up again."                    -Kurt Vonnegut     |
> 
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