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Re: more boost
>I am speaking specifically about the UrQ's MAC-02 ECU, the only one I
>have studied, and from what you post above, I am willing to bet I (and
>by extension the "network" of those of us who have spent considerable
>time and effort in understanding the whole system) know a hell of a lot
>more about it than you do.
>
> -RDH
Of course you do!!!! I just wonder why you tore me to pieces instead of
answering the original question. I wonder if you even read the original
'Cuz I read (and quite possibly miscontrued) your mail as a very Godly
Truth that your krock (Zener) is infinitely superior to the other krock
(resistor/voltage-divider) because yours fooled the timing in a dif-
ferent manner. And that there was no other alternative except for YOUR
solution -- that all else was just crap by people who don't know any
better. This annoyed me. If I read far too much between non-lines, my
apologies. I certainly didn't mean to "tear you to pieces" . . .
question which asked how to do the resistor or zener mod and still maintain
the fuel pump safety circuits.
I certainly thought I read and understood your question, and thought I
quite clearly answered it, albeit in general terms. To wit, with the
zener, you cannot maintain reliable overboost protection. (Well, you
could add an external circuit to sense overboost and bypass the zener
with a +5 to trigger the ECU to "realize" it had overboost, or not
even bother with the ECU, just cut the fuel pump yourself...Yuck)
Since I guess you wanted some more details:
With a voltage scaler, you have to "recalibrate" the ECU to the new
absolute pressure<=>voltage<=>0..0xFF mapping. Then (with specific
reference to the MAC-02 "F" model (same theory, but some of the maps
changed location from the earlier "B" model) you need to scale the
Boost => Timing Table Map and the Overboost Map accordingly from
their stock values [excerpted from my MAC-02 disassembly listing]:
; The Manifold Absolute Pressure => Index-16 map (into TimingTable,
; OverBoostTable, etc.)
;
; values A/D converted, from max boost to max vacuum (high numbers
; decending to low numbers):
;
; 0xFE = ~16.0 PSI
; 0xF0 = 14.75 PSI
; 0xE0 = 13.25 PSI
; 0xD0 = 11.75 PSI
; 0xC0 = 10.00 PSI
; 0xB0 = 8.75 PSI
; 0xA0 = 7.00 PSI
; 0x90 = 5.25 PSI
; 0x80 = 4.00 PSI
; 0x70 = 2.75 PSI
; 0x60 = ~1.00 PSI
; 0x50 = 0 - 1 InHg
; 0x48 = 1-1.5 InHg
; 0x40 = 4 InHg
; 0x30 = 7 InHg
ManPressureMap16:
F120: D2=210 C3=195 B3=179 9C=156 87=135 7C=124 71=113 68=104
5D=093 52=082 49=073 3E=062 34=052 2A=042 20=032 15=021
=== and ===
; The Over-Boost Engine-shutdown table, indexed by RPMMap16 index.
;
; values A/D converted, as in BoostMapIndex16 above.
OverBoostTable:
F160: 7D=125 8D=141 9C=156 B3=179 CA=202 D7=215 DA=218 DA=218
DA=218 DA=218 DA=218 DA=218 DA=218 DA=218 DA=218 DA=218
So, for example, the stock overboost is set to 12ish PSI, and the first
entry (column) in the timing map controls the timing for boost levels
roughly between roughly 10 and 12 PSI.
If you scale the manifold pressure sensor output by (for ease of example)
1:2 (50% or half), then to maintain the first timing column in the 10 to
12 PSI range, you'd change the first two ManPressureMap16 entries to be
0x69 (105 decimal) and 0x62 (98 decimal) respectively. Ditto for scaling
the OverBoostTable entries, divide 'em all by two.
To extend the operating range of the timing table into higher boost
regimes, you must compress the 16-pressure-ranges (x 16 RPM ranges)
table into, say, 14 pressure ranges (by, say, throwing out the second
and fourth [one-based] columns, sliding down columns one and three to
become the new three and four respectively, then creating new columns
one and two to, again for example, represent boost levels of 20 and
16 PSI respectively (and of course changing the mapping of the
ManPressureMap16 table accordingly [actually, I "think of it" in the
reverse fashion -- ManPressureMap16 determines the meaning of the
16x16 timing table columns, so I would change it first to define
the new mapping, then change the timing columns to match; I assume
you get the idea, whichever way you choose to think about it]).
I gave the answer, which is more than anyone else did, so get off your
soapbox, unknot your knickers and calm down before you have an apoplectic fit.
If I get off the soapbox, I can't answer you, which do you want? [by
the by, that's a rhetorical question...]
Well thats enough excitement for this week, back to lurking until another
question which I can answer comes up. BTW all those people who mailed me
directly thanking me for the answer, please excuse me for not answering
directly, there were a lot of you and you are all most welcome.
Peter Wales pjwales@magicnet.net
President Superchips Inc
Chairman Superchips Ltd "Timing is everything"
Superchips home page with all the answers http://www.superchips.com
By the way, I realize in the above I have been rather carefree in my
use of PSI, and Boost, and pressure. I really do know the difference
between "boost" (the amount of positive pressure relative to current
ambient [or whatever standard]), vacuum (the amount of negative
pressure relative to current ambient [or whatever standard]), absolute
pressure (the amount of pressure relative to zero pressure or an
absolute vacuum), and so on.
The ECU measures [manifold] absolute pressure, while the wastegate
regulates boost relative to atmosperic pressure, thus 12PSI of boost
in Boston is a hell of a lot more manifold absolute pressure than
12PSI of boost atop Pike's Peak [one of the reasons why I use a Boost
Graphic to dynamically control my UrQ's "boost level"]. Nominally, I
use "boost" and "vacuum" as atmosperic-relative to sealevel/14.7PSI
absolute readings, but do rather freely intermix the terms when
talking about the ECU reading "12PSI of boost" and the turbo
generating "12PSI of boost". I probably could be more explicit in my
use of the language. But I don't want to make it *too* easy on y'all
. . .
Enuf said. Time to get off my soapbox and wash my knickers.
-RDH