[Diy_efi] Making a fake O2

[Marc Reviel]

>--- Marc Reviel <marc at powerlogix.com> wrote:
>
>>  FYI, I am just finishing a prototype of a twin turbo
>>  upgrade for the Porsche Boxster.  The test mule is a
>>  1999 model, 2.5L, 11:1, no variable cam timing,
>>  and last year before they went to e-throttle.  I
>>  designed it for low-boost/earliest spool up -
>>  2000rpm = 2.5psi, 2400 = 5psi. During part-
>>  throttle/mild acceleration, it is almost always
>>  running positive boost, and does remain in closed-
>>  loop.
>
>It's commanding lambda 1 under boost without problems?
>  Is it radically retarding ignition timing to
>accomodate that AFR?

Yes, it does pull timing a bit, but that's mainly due to the charge 
temp rising with boost. The target boost pressure is modest - only 
5psi. But, to verify headroom, I have run 7-8psi to attempt to 
introduce knock (to no avail on 93 octane).  Timing drops to 18-19 
degrees under these conditions, where it normally is 21-22 degrees.


>
>>  I have about 1200 miles heavy testing on it.
>>  So far, no issues at all (not even a CEL). No
>>  piggyback stuff, stock ECU programming.
>
>I guess it doesn't surprise me *too* terribly much
>that the stock sensors can handle a bit of boost.  I
>gather there is an airbox-mounted intake pressure
>sensor, or a MAF sensor (or possibly both)?


The "T-Mass" is a Bosch mass-flow sensor with a temperature sensor. 
Audi's use them, as well as others.  (No MAP sensor.) Basically, to 
the ECU in terms of air-mass, it just looks like the engine is 
suddenly about 40% larger in displacement and running in a hot 
climate...fortunately all the existing components can handle it, 
including the timing/fuel maps.  No, they're not perfect, but good 
enough for much testing.  Will definitely have to enrichen >4K rpm.

-Marc

>
>| 82 Honda CX500 Turbo (Cassandra)  90 Kwak Zephyr 550 (Daphne) |
>| "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   |
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>
>
>
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-- 
Marc Reviel

PowerLogix
http://www.powerlogix.com