[Diy_efi] problem with ecu and injector duty

Tue Nov 14 18:32:54 UTC 2006

Good point.  I made an ASSumption that the injectors were timed to the
crankshaft somehow.  That's the problem with ASSumptions...

I would also note that the original poster has not responded back to any of
the responses.  Must be busy.  I'm betting he could get some help if he did.

Later,

Dan Nicoson

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Carter Shore
Sent: Tuesday, November 14, 2006 1:02 PM
To: diy_efi at diy-efi.org
Subject: RE: [Diy_efi] problem with ecu and injector duty

Yes, that's exactly the point of my post;

Duty cycle is ratio of On-time to Off-time.
If the injectors are not triggered synchronously with
the crankshaft, and all you know is the On-time (17
mS) then either the pulse *frequency* or Off-Time must
be known in order to calculate the duty cycle.

Some batch-fire schemes are asynchronous with the
crankshaft, but it doesn't appear to me that this is
one of them, after examining the site.

Carter Shore

--- Daniel Nicoson <A6intruder at myo-p.com> wrote:

> At 550 RPM on a four cycle engine he has just
> slightly over 20ms available
> (6000 RPM a PW=20ms is 100% duty cycle).
>
> Dan Nicoson
>
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org
> [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of Carter Shore
> Sent: Tuesday, November 14, 2006 11:05 AM
> To: diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] problem with ecu and injector
> duty
>
> I have not looked at the link yet, but are you sure
> that the ECU is sequential, rather than batch?
> The injector pulsewidth/duty cycle only makes sense
> if
> you know what the underlying pulse frequency is, ie
> what's the dead time?
>
> --- Mark Riley <turbotuneusltd at triad.rr.com> wrote:
>
> > I would hook up a fuel pressure guage and see that
> > the fuel pressure does
> > indeed rise 1 for 1 with the boost level. I would
> > suspect that perhaps the
> > Pump is not keeping up at the upper pressure
> levels.
> > If the guage shows any
> > fluctuation at over 10 psi boost or does not make
> > the correct pressure rise
> > all the way to max boost, the pump is not capable.
> >
> > Mark Riley
> >
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On
> > Behalf Of Damian Long
> > Sent: Monday, November 13, 2006 8:44 PM
> > To: diy_efi at diy-efi.org
> > Subject: [Diy_efi] problem with ecu and injector
> > duty
> >
> > Hi,
> >
> >   I have a rather strange ecu. Most likely not
> many
> > people have used it
> > before. It is a Walbro Bike400. You can get some
> > information from here
> > www.walbro-tdd.com
> >
> >   Since installing and running this ecu I've tuned
> > the vehicle and found
> > I've needed some very stupid injector opening
> times.
> > At 2bar boost and
> > 5500rpm I need 17mS opening time!
> >   Vehicle is 1600cc 4cyl turbo.
> >   The injectors are Nippon denso 16ohm 550cc/min
> > @40psi. part no
> > 1955000-2020. The fuel pump is a Bosch motorsport
> > unit. 150lph @ 5bar. The
> > pump, regulator and rail pressure all check out ok
> > so I've discovered that
> > its an issue with the ecu or wiring to the
> > injectors. Basically the ecu need
> > to send a 17mS opening time in order to get the
> > injector to open long enough
> > to supply fuel. The injectors are well sized for
> the
> > application.
> >   Does anyone have any ideas where I should be
> > looking for a solution to the
> > problem? So far I have the following ideas but now
> > sure if any are relevant.
> >
> >   1. ecu is designed for peak and hold injectors
> and
> > this is why
> >   2. wiring to injectors wrong way round. ie. coil
> > polarity wrong
> >   3. injector voltage offset table set up wrong in
> > ecu
> >   4. ecu is lying or is just plain cr p and I
> should
> > burn it
> >
> >   I flow tested injectors. They are ok. Any ideas?
> >
> >   thanks
> >
> >
> >
> >  Send instant messages to your online friends
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