[Supras] boost pulling timing

Thu Dec 20 12:48:33 CST 2007

I hate phone induced spelling errors.  :)

Got brakes?
======
25hrs or one season with one pad set is possible.  Save money and pit  
time, compromise nothing.  Ask how.
TXT or Tone: 8414546712 at txt.att.net
http://www.speedtoys.com

On Dec 20, 2007, at 10:44 AM, Jim Jobe <jjobe2 at supratech.org> wrote:

>
> Correct, these devices scale the "load" input ("PSI" in my
> chart) to the ECU.
>
> Moving the exh cam changes the relationship between the
> crank and the cps.
>
> On Thu, Dec 20, 2007 at 10:33:34AM -0800, Speedtoys wrote:
>> Its worthy to note that an safc of other fuel mapper will shift how
>> the ecu measures load and will likely artificially  keepbtimif
>> slightly more advanced then it should be.
>>
>> Lind of like people chagog exhaust cam timing and not realizing the
>> huge advaves in timing from the shift in the
>> Cps readings.
>>
>> Got brakes?
>> ======
>> 25hrs or one season with one pad set is possible.  Save money and pit
>> time, compromise nothing.  Ask how.
>> TXT or Tone: 8414546712 at txt.att.net
>> http://www.speedtoys.com
>>
>>
>> On Dec 20, 2007, at 6:55 AM, Jim Jobe <jjobe2 at supratech.org> wrote:
>>
>>>
>>> Boost (MAP, Speed Density), AFM, are ways to measure air volume,
>>> commonly referred to as "load".  In the case of the 7MGTE ECU,
>>> air volume is calculated using the AFM and IAT sensors as inputs.
>>>
>>> Yes, any ECU should retard and advance ign timing vs load either
>>> via a function or a pre-programmed table.  RPM, coolant and intake
>>> air temp, as well as of any number of variables inputs are used
>>> when calculating ign timing.  Ign timing is usually retarded
>>> as temps pass the normal operating range in an attempt to
>>> control cylinder temperatures.
>>>
>>> Something like this: (numbers are arbitrary for example)
>>>
>>> Ign Timing table.  Note the dip at higher boost.
>>>
>>> 10| 17 16 14 13 14 15 16 17
>>> 9 | 18 17 15 13 14 15 16 17
>>> 8 | 19 17 14 14 15 16 17 18
>>> P 7 | 20 19 17 15 16 17 19 22
>>> S 6 | 20 21 19 16 17 19 21 24
>>> I 5 | 22 21 20 19 19 20 22 24
>>> 4 | 22 23 22 21 22 23 24 25
>>> 3 | 24 24 24 24 25 26 27 28
>>> 2 | 26 26 26 26 27 28 29 30
>>> 1 | 26 26 27 28 29 30 31 32
>>>  -------------------------
>>>    3  3  4  4  5  5  6  6
>>>    0  5  0  5  0  5  0  5
>>>    0  0  0  0  0  0  0  0
>>>    0  0  0  0  0  0  0  0
>>>            RPM
>>>
>>> Ign Timing vs temp
>>>
>>> +2.0 +1.5 +1.0 +.5 0  -.5 -1.0 -1.5 -2.0
>>> ------------------------------------
>>> 1    1    1    1   1  2   2    2    2
>>> 5    6    7    8   9  0   1    2    3
>>> 0    0    0    0   0  0   0    0    4
>>>            Coolant Temp (F)
>>>
>>> The "knock sensor" code is triggered when the ECU
>>> does not receive any signal at all from the knock
>>> sensors.  The knock sensors are essentially microphones
>>> with a bandpass filter applied.  Any time the engine
>>> is running there will be some noise.  The CE code is
>>> to tell you that the knock sensor circuit is malfunctioning
>>> because no signal has been received, not because it is
>>> reading above the threshold suggesting there is knocking.
>>>
>>> On Thu, Dec 20, 2007 at 09:07:32AM -0500, Walker, Brian (Rich. Dist)
>>> wrote:
>>>> I'm not aware of a feature that would cause boost to pull timing, I
>>>> believe that circuit is open loop as I don't recall the ecu
>>>> receiving a
>>>> pressure signal from the sensor. Perhaps it's related to an airflow
>>>> signal that pulls timing? (from my understanding the ecu should
>>>> retard
>>>> timing at higher boost for safety and power reasons, I'm imaging
>>>> that's
>>>> a function of airflow in the maps?)
>>>>
>>>> I wonder if anyone out there has datalogs showing timing vs. boost?
>>>> The
>>>> MAFT is supposed to show this info, but I haven't had a chance to
>>>> mess
>>>> with mine since install. FWIW, I've never had a code for knock,  
>>>> even
>>>> when one sensor crumbled apart as I went to remove it.
>>>> Brian W
>>>>
>>>> -----Original Message-----
>>>> From: berniek at technicaldevelop.com [mailto:berniek at technicaldevelop.com
>>>> ]
>>>>
>>>> Sent: Thursday, December 20, 2007 12:58 AM
>>>> To: Walker, Brian (Rich. Dist); cthommes at adelphia.net; Jim Jobe;
>>>> Supras at supras.com; Jeff Mohler; Jeff Corbat
>>>> Subject: Re: boost pulling timing
>>>>
>>>> I've wrestled with this issue too, running a Lex and 550cc
>>>> injectors, 57
>>>> trim CT26, 3" turbo back exhaust, 15-17 PSI boost, IC upgrade to
>>>> come,
>>>> some hardpipes, all with the stock ECU, trimming fuel pressure and
>>>> the
>>>> Lex bypass.  In a word, the pressure transducer at least in '90 and
>>>> '91
>>>> applications only operates the dash gauge, nothing more (it will
>>>> operate
>>>> up to almost 15 PSI at about 14.9V output if you rescale the gauge
>>>> circuitry to match it).  That leaves the knock sensors to retard
>>>> timing
>>>> if and when needed under higher boost.  I believe Jeff Corbat is
>>>> running
>>>> a setup like this with a stock turbo and has had no problems.  I've
>>>> had
>>>> no codes set ever (in all of 500 miles, lol, but some of it before
>>>> the
>>>> snow under really punishing conditions.
>>>>
>>>>
>>>>  Bernie
>>>>
>>>>
>>>> PS:  I believe I might have an earlier ECU which might explain  
>>>> slight
>>>> mixture dependence upon temperature and faster idle with the lights
>>>> on.
>>>>
>>>> Once when I did not catch second gear upshifting in time, it spun  
>>>> to
>>>> 6500 RPM, which '91's with fully counterweighted crankshafts are  
>>>> not
>>>> supposed to do.  My '90 stuttered at 6200.