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

[Adam Wade]

--- Startled Jackrabbit <bluefire211 at yahoo.com> wrote:

> My problem is not that the sensor would be past its
> limits.  What I am worried about is once my intake
> reaches the maximum pressure allowed by the
> wastegate (which is currently set at 12 psi, no
> spikes, rock solid, nearly independent of weather)
> and I am not at full throttle and then I go to WOT.
> If more air flows into the engine, I am still at 12
> psi, so the computer doesn't know about it.  If it
> increased to 15 psi, the computer would be able to
> read that, but the fact is it cannot go over 12.

Well, any car without an MAF cannot directly measure
the actual mass of air entering the engine with a
single sensor.  If you have a MAP sensor, then the ECU
figures mass by mapping VE, and then factoring that
map against MAP and engine rpm.  It accurately
computes the increased mass entering the engine even
if the MAP remains the same.  I guess I'm confused as
to why you think that the ECU couldn't handle an
identical MAP at different rpms.  ECUs do that ever
day, even in non-turbo cars.  There isn't one MAP per
rpm in all conditions...

> However, I don't think this is a concern, as was
> stated in a prior post, MAP is MAP.  So going to
> full throttle when I'm already at full boost
> shouldn't matter.

Hm.  Well, the wastegate is on the EXHAUST.  So if you
are at full boost, you should still get different MAP
readings with different throttle positions.

Now, some wastegates are electronically controlled to
limit intake pressure.  In that case, if you had
reached maximum MAP, and the ECU decided to open the
wastegate more, no, increasing the throttle opening
would have no effect on the acceleration of the
vehicle, nor would the fueling needs change except
based on rpm and VE.

=====
| 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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