[Supras] REG Lex AFM bypass screw

[berniek at technicaldevelop.com]

Dear Dan:

    Good luck with getting everything working.  With the cleaned up JDM 
engine (valves and rings) installed, I'm installing ND 550cc injectors 
and the Lex.  I did the screw extension myself in the small machine shop 
here. 

    From what I understand, the conversion is such that you will run 
lean without boost, but will be too rich on the top end.  I'd like to 
avoid the time of tuning electronic add-ons or ECU replacements if I 
could, so I'm considering "faking" the resistance signal from the AFM to 
the ECU under boost to lean the top end out to a degree.  The caveat is 
that the thermistor used is non-linear, so that will be a head scratcher 
for a while.  If viable it can be done with a boost pressure switch and 
fixed resistor in parallel with the AFM temperature sensor (since it is 
negative tempco).  There is also the possibility of running a sizable 
solenoid valve normally open during normal conditions, and let it close 
during boost, again to "fake" the airflow signal.  I have larger Asco 
and Skinner valves here for this.  I also have a 57 trim upgraded CT26, 
but from all I read, I need to get into the habit of changing cats and 
downpipes to use a 3" downpipe except at inspection time.  Hopefully, NJ 
will remove the chassis dynos in 18 months now that most cars are OBD2.

    Again, thanks for the response and take care. 

       BernieK



Dan Gyoba wrote:
> On 4 Sep 2007 at 20:00, berniek at technicaldevelop.com wrote:
>
>   
>>  From everything I've read, the objective reg had was to lengthen the
>> screw to lower the air bypass flow.
>>     
>
> This is exactly the objective.  The Lexus AFM isn't exactly right for the 550cc 
> injectors, it still depends on the ECU's mapping ability to some extent.
>
> With the stock Lexus screw in place, I occasionally get ECU code 31.  This generally 
> happens at idle, particularly after hard runs, though not always.  I suspect that 
> what is happening is that the air speed signal from the ECU is too low.  In this 
> case, a longer screw to tune the AFM with would be a good thing.
>
> Now, though I know that Reg did have the screw created specifically for this purpose, 
> I do think that $100 is a bit much for what it is, and there must be a more 
> economical way.
>
> I have some other issues that I need to clear up before this becomes a priority.  My 
> Lexus/550 swap so far isn't being used yet (I'm still running stock boost on the 
> stock turbo) but it's there.
>
> Dan Gyoba
> '89 NA 451,732 kms, Turbo swap COMPLETE
> http://www.abstractconsulting.com/~dan
>
>
>
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