[Diy_efi] RE: Throttling intake air

[Adam Wade]

--- Bill Washington <bill.washington at nec.com.au>
wrote:

> 1. An intake air throttle before the compressor will
> reduce intake air pressure to the compressor, thus
> reducing the load/work it is doing at 
> any part throttle position, therefore at any given
> exhaust airflow it will be spinning faster - does
> this sound logical?

It will have a lower pressure before the turbine, and
therefore will require more energy from the exhaust to
overcome that low pressure.  What might be worth
looking at is the pressure DIFFERENTIAL between the
throttle side and the engine side, vs. the pre-turbine
side and the pre-throttle side if the throttle was
moved between the turbine and the engine.

Slowing the turbine side, by whatever means, will
increase exhaust backpressure, and therefore will
"eat" some of the power produced via increased
pressure at TDC, as well as cutting down scavenging.

> 2. Does opening the wastegate cause the turbo to
> spool down quickly?

I wouldn't think so.  Opening the waste gate and
having a high post-compressor pressure should, though.

> 3. Has anyone considered a variable flow restrictor
> in the exhaust immediately after the turbine instead
> of a wastegate?

Seems like that would be a worse solution than a
wastegate, in the sense that it would decrease
efficiency.  It could slow the turbine more than a
wastegate, but I doubt it would function very well as
an engine brake.



On an unrelated note, we've had a spate recently of
people posting short replies and quoting 6 or 7 nested
messages BELOW, and not removing extraneous material. 
In one case, there was a 500-line message that was to
give a one-line "me, too!" reply.

I can't speak for anyone else, but I know I can't read
posts that are not structured reasonably well, because
it requires more effort than I am willing to donate;
in addition, there's a HUGE waste fo bandwidth and
mailbox space quoting unnecessary stuff over and over
again.  So I would like to ask people to please trim
their replies, and ideally, post replies immediately
below the relevant quoted material so it is readable
and makes sense.

Thanks.  ;)

=====
| 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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