[Supras] Dawes and boost richness

[joe at wilmcd.com]

Oh I hear ya. I have put off working on my car a lot for the past couple
of years now.

I went the laptop route with a MAP-ECU but decided it was a pain. I now
have the MAFT-Pro. No laptop necessary unless you want to log all the
time. The S-AFC has no laptop interface as far as I know (the new ones
might). But yes, you have gotten the most bang for the buck. Every
horsepower from here on out will cost you more than the first ones did :-)
Someday it won't feel fast anymore and you'll take the next step. But for
now... just enjoy it!

-Joe

> Joe and group:
>
> I still need to measure Af at the diagnostic connector, and purposely went
> the 550cc-Lex route to avoid complexity and the need for tuning with a
> laptop.  Right now I will have some time this coming weekend or next to
> trim up the fuel pressure and the Lex bypass, but everything now seems
> right, just like stock, but with about twice the push in the back above
> 3000 RPM (due to 57 turbo and bigger exhaust).  Maybe I'll have time next
> summer to get into laptop S-AFC tuning, but for now, I'll live with the
> same top-end richness as Toyota built into the engine in the first place.
> Getting the engine together from scratch, installing and commissioning it
> took quite a bit of free time durign the summer to the point where it had
> begun causing spouse problems.  We live about 75 minutes from the Jersey
> shore, and had gotten into the ocean 30 minutes this past summer.  So,
> next summer will offer a bit more time.  Working in defense engineering is
> all-consuming, not the "glamor" job it was 50 years ago.
>
> Bernie
>
>> By adding the Lexus AFM you've basically added a non-adjustable S-AFC.
>> Maybe a bit of a simplification, but it's essentially the same. They are
>> both lying to the ECU about the amount of air. You happen to be
>> offsetting
>> that because you have larger injectors. That makes it seem more "pure"
>> of
>> a mod but it's the same thing. In order to get the best (by that I mean
>> safest and most reliable) power from the car you need to be able to tune
>> it at different points. I hope that helps a bit... I don't know if you
>> have a choice but to get into the piggy-back or standalone world. :-\
>>
>> -Joe
>>
>>> Joe:
>>>
>>>     The Dawes is a relatively simple A/F ratio indicator that works
>>> from
>>> the last fractional volt of output from the stock O2 sensor.  I know
>>> others using them and they have been reliable.  Before installing it I
>>> did a "propane torch" test of the sensor, described elsewhere (I can
>>> get
>>> the link for you) and corroborated it with bench tests with a precision
>>> voltmeter.  I don't recall the exact numbers, but the Dawes does the
>>> following using a National Semiconductor analog voltage to LED driver
>>> chip:
>>>
>>> .95 to 1V:  Excessively rich, about 9:1.  Illuminates blue LED.
>>>
>>> .90 to .95V:  Just about right, about 11:1.  Illuminates green LED.
>>>
>>> .87 to .90V:  Illuminates amber LED, leaner than 11:1.
>>>
>>> Less than .85V:  Illuminates red LED, too lean for safe operation under
>>> boost.
>>>
>>>     Dawes is now known as 3 bar racing.  Although I work in defense
>>> electronics development, I have somewhat of an aversion to adding
>>> additional electronics to the car unless it is really needed.  Right
>>> now, the car behaves like stock from a fuel mixture and other
>>> operational standpoint, but with about twice the push in the back as
>>> compared with stock (above 3000 RPM).  About the only additional
>>> electronics I will add will be a 0-30 PSIG pressure sensor, with an
>>> attenuation resistor network to make the stock gauge read about 20 PSIG
>>> full scale (not interested in the meaningless vacuum reading of the
>>> stock gauge).  It is a Sensym item bought from Digi-Key for about $30.
>>> Needs a perfboard and box to replace the stock sensor (now with
>>> attenuated output to read up to about 14 PSI on the stock gauge before
>>> pinning it).  The stock sensor will saturate at about 14 PSI.
>>>
>>>     Right now the car feels as if it will beat almost anything on the
>>> road, at least up to the end of second gear (breaks the 275/40/17
>>> Bridgestones loose at about 4K-5K RPM in second).  Mods are as follows:
>>>
>>>
>>>
>>> 550cc Greddy (ND) injectors.
>>> Walbro pump.
>>> Lexus AFM, stock screw about 1/2 way in.
>>> Free flow dry AEM air filter.
>>> 3" exhaust overall and Lipp elbow, with one high flow Random Technology
>>> cat.
>>> 57 trim CT26 turbo.
>>> Radiused inlets on 3000 pipe and turbo discharge 45 degree elbow
>>> casting
>>> (hard pipes to come).
>>> Dawes A/F meter (reads very rich end of stock O2 sensor, and presently
>>> indicates about 9:1 AFR at full boost.
>>> Dawes boost controller set to 15 PSI, sometimes spikes to 17 PSI for
>>> less than one second.
>>> Valve bowls cleaned up with die grinder.
>>> Valve springs shimmed to about .025" less than stock height.
>>> Cometic 2.2 mm HG (block was decked twice due to rollover on floor).
>>> ARP studs torqued to 85 lb-ft (80% of yield).
>>> Modified stock FPR (works fine) set to about 38 PSI (measured with no
>>> vacuum on spring side).
>>> '89 hard captive urethane engine mounts.
>>> Moved oil pickup 3-1/2" further back in pan.
>>> Lightly cleaned up stock exhaust manifold, and Helicoiled head tappings
>>> for exhaust studs.
>>> I can feel that the stock cams make it run out of power at about 5700
>>> RPM.  But...  They will remain in place until NJ removes the inspection
>>> station dynos, now that most cars are OBD2.
>>>
>>>
>>>         Bernie.
>>>
>>>
>>>
>>>
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