Dyno-Less tuning?

Thor Johnson thormj at earthlink.net
Tue May 19 05:50:09 GMT 1998


Brief recap... this is a 68hc11 EFI (fuel only) for a Honda
CBR600 motor.  All homemade stuff.
Calculates base PW based on MAP, all other sensors totally
ignored (incl RPM)... batch fired at #1 intake stroke.  How
important is RPM (considering I'm injecting 1/rev anyway)?

Ok... now that I've gotten my ECM to ignore noise on the Cam
sensor line, I *think* I'm ready to start tuning the thing.... I
am not having as much success as I thought I would though, so I
have a few questions:

  1. Can I effectively tune in neutral?  My data comes outta a
serial
      port & my host pc is AC-only. (Is there a way to hook a
cellphone to
      an external 9600 baud serial port/modem?  My ECM don't do
PCMCIA!
      I can choose from PowerTel PCS or bellsouth mobility D/A
phones.)

     I am trying to tune in neutral...  It doesn't seem to
reflect
     "loaded" conditions very well.  I'm currently ramping
*slowly* to
     try to get the "static response" tuned up.

  2. What should be my goal?  Should I attempt to maintain a
consistent
      O2 sensor voltage across the RPM range?

     I'm trying to keep the incr in throttle from making the oxy
go lean
     and the engine sputter & die (this is accompanied by a
steady rev of
     the engine at the constant throttle posn).

  3. How do I handle transient effects?  I am toying with the
idea of an
     "electronic accelerator pump" that has "addtl fuel" vs.
"delta throttle".
     Should I make the length of the effect (decay curve?)
adjustable or will
     a "single shot of gas" do it?

     Right now my maps look like a small slope in the 0-10PSIA,
and about 10x
     that in the 10PSIA+ entries.  This gives ok starting from
idle, but
     flooring it while 6-8K will still cause it to stumble
(badly!).

  4. Do Ego's have memories?  At times, the RPM will increase
before the throttle
     opens, the oxy goes lean & the engine quits.  The only thing
I can think of is
     that the mixture was already lean (but the sensor was still
reading rich), so
     the R's went up.  The oxy falls .2-.6 secs after the rpm
starts its "death rev."
     These are 1yr old sensors, 3" from exhaust port, running
M85.  They have been
     sooted to death before (as have the plugs....). [PSST. CSH
trick:  To clean the
      plugs, we lean the A/F mix by switching off the fuel pump
before shutdown!]

  5. I am getting some wild variations at certain R's among the 4
Ego's.  It only happens
     at certain R's (& best sound is a Rich-Lean-Lean-Rich
pattern [1234])... does this
     indicate an airflow problem in the intake system (composed
of PVC, 18mm restrictor)?
     How bad does this hurt us/the engine?

  6. I'm taking MAP readings about 6" from the cylinder inlet.
The intake is 1" sch40 PVC
     molded in an attempt to maintain an 8 degrees exit angle to
the head from the 18mm
     restrictor (a la fluids).  Is this a bad place to do this?
I tried at the test ports
     of the cyl intake, but the vacuum fluctuated wildly
there....

---

I have some nice long data logs that look like (like hondo?):
  CamDT, Throt, PSI, Tp1, Tp2, Tp3, Tp4, Ox1, Ox2, Ox3, Ox4

I've loaded these into excel to assist me... does anyone have a
"tuning your ecm with excel" faq?
I have lots of points, but I have no idea whats going on....
they make pretty lines...

Currently, I'm leaning the whole map out until the engine hardly
runs, finding that MAP value, twiddling with it (slowly) until I
get Ego's in the range I want (which changes the RPM!), doing the
same to the new RPM... I can't quite get it to converge.  To get
the upper PSI points, I have just *completely made up numbers*
that attempt to elimanate idle->WOT stumble.
It doesn't help 1/2throt->WOT very much.

I'm also thinking about making the ECM output binary... I can't
get anywhere near 1 row/CamR with this excel/ascii format (9600
baud), but I'm wondering how much that extra data would help me,
vs the trade-off in convenience/readability....

As you can see, I'm confused when we try to get these things to
work in reality instead of theory...

TIA,
Thor Johnson




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