Timing being pulled back? With links to the graphs

Mihnea Cotet mik at info.fundp.ac.be
Thu Dec 5 22:15:51 EST 2002


See comments inserted below.

>>From: "Claus Vegener" <vegener at post7.tele.dk>
>>To: "audifan20v" <200q20v at audifans.com>, "Mihnea Cotet"
>><mik at info.fundp.ac.be>
>>Subject: Re: Timing being pulled back?  With links to the graphs
>>Date: Thu, 5 Dec 2002 01:13:36 +0100
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>>Well Mihnea - long story
>>I could be wrong.
>>I have checked all my mails with Ned without finding the
>>exact statement - so misunderstandings from phone calls may exist
>>but I have had this opinion for a quite long time and some other things
>>seems to convince me in that opinion
>>When the engine is accelerating you have to accept, that the ECU use
>>look-up tables with different input other than closed loop -
>>and feed back - from the Lambda.
>>There is a lot of talking about old type Lambda and wide band sensors
>>(not used for Motronic year 90) usable at any load.
>>So my guess is, that closed loop (feed-back) is not possible at
>>a lot of running conditions.
>>Charles O. Probst in Bosch Fuel Injection & Engine Management mentions on
>>page 36 Pulsed Injection - Full Load Acceleration
>>that the WOT switch disables the air-flow signal and base the fuel
>>enrichment solely on rpm.
>>To my opinion he should have written "on rpm and boost" too !!
>>I am sure temperature and boost are input to tables too.

Well, the temperature is for sure an input but it is used for correction
maps, i.e. air temps correction for timing and fuel maps, but it isn't an
input in the main running tables (16x16 values) which only use MAF and RPM.
As for boost, it's possible that it is also used in a correction map but
again, not as a main input parameter. Boost is also used in the fuel pump
cut-off on stock chips but only as a lookup parameter.

>>My own experience is,
>>a) that when cruising at constant speed
>>the Lambda changes lean-normal-fat some times a second - all the time. If
>>you start pulling up-hill or accelerating
>>  the mixture is enriched showing the use of tables and not closed loop ?

Well, depending on the throttle position, it can be closed or open loop.
After about 80% throttle opening it goes into open loop but before not.
Also, the enrichment provided for the highest air flow values is quite
consequent, i.e. about Lambda 0.88 @ maxRPM/maxMAF in my MTM chips.

>>b) at very hard acceleration - if the fuel pressure is too high -
>>the engine hesitates close to 4800 rpm and wont go to 7000.
>>Lowering pressure fix this problem. The Lambda is not able to
>>adjust. Just show fat mixture. But coasting and idling is still fine.
>>To be honest - the only doubt I have is whether I was told 4200 or 4400
>>rpm :-).
>>But I have to admit, that measured air escaping due to un-tightness also
>>give problems at acceleration.
>>MAPsensor upgrade?
>>If the boost can't be measured - the fuel can't be calculated -
>>to my opinion and a over-boost condition would arise.
>>A 2.0 Bar sensor delivers 5.0 V from 2.0 Bar and up to damage. The boost
>>chip run out of tables?

Well, I still need to investigate the boost chips, until now I've mainly
focused on the fuel/timing chip but I also still have many things to learn
about these things. Maybe you're right about the WOT enrichment factors
that only use the MAF up to 4200/4400 RPM, I'll find this out soon anyway.

>>WG spring: I bought it from a Danish manufacture of springs.
>>I choose a length of 48 mm close to 2 "; a diameter 46 mm
>>as the original and coresize is 5  mm. And made the perch adjustable. You
>>can only compress a few mm with your hands.
>>Test-drive carefully watching boost in a high gear.
>>The real reason for playing with WG springs were the break down of my
>>Garrett turbo. I had to re-install my k24 and I didn't had
>>a standard MAF, only my RS2 MAF. So in order to save the live
>>of the k24 with the IA V set-up at 2.7 Bar I want to run at max 2.4 Bar -
>>and that works real great with the 3 Bar chipset, RS2 injectors and MAF.
>>I am interested in the truth about chips and ECU so please inform an
>>correct me.

Okay, this is what I'm trying and will be trying to do as soon as I know
more and more things. Learning these things isn't easy because there is no
way to find a document somewhere on the internet telling you what does what
and how an ECU works exactly.

>>I have decided, that next time I want to enhance my car, it should be
>>based on user programmable
>>systems in order to get rid of the restrictive Motronic.
>>Like a 034 from Javad perhaps for my Urq WR engine.
>>But 5 coil ignition is not released yet - ...

Well, the Motronic isn't so restrictive but the point is that it is all but
user programmable. This is what I'm trying to do now, learn everything so I
can reprogram my ECU myself but hell it ain't easy and I'm still far from
burning my first completely home-brew chip.

034 is a great idea, I even hesitate wether to go for it or not but I guess
that I'll go for it when the Motronic has shown its limits... but they are
still far away, Tom Schmalz made a 540 HP 90q in Germany with self
programmed chips, well he's a tuner himself :)


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