90 model civic dx injection operation from factory manual

I'm working on a project, adapting the dual point TB injection from a 90
civic DX to my 77 civic 1200. I'm going to use an aftermarket EFI computer
(megasquirt) but have a couple of questions someone with a factory manual
might be able to answer.

I know this system uses a primary and secondary injector, first I assume the
lower one is the primary? Second at what point in the RPM range does it
switch to the secondary and does it add the second one or switch to it?
Third do they specify what the flow rate of these injectors are? TIA for
any clues.

 

i'm not sure megasquirt does dual point - you may want to check the info
on that before proceeding any further. if you're going to the trouble
of retrofitting, either go 4-point and make life easy /or/ just use the
whole dpfi system from an 88-91 civic. if you need to re-map the dpfi
ecu for a different volumetric profile, there are some "2-ner" projects
out there that show you how to do it. google is your friend.

regarding specific questions, lower is primary and upper is
"enrichment". it will inject over the full rev range if conditions
warrant. it also injects as a function of tandem valve position because
the tandem valve is designed to increase air flow velocity [at the
expense of volume] and hence better fuel droplet evaporation.

 

They're called "main" and "auxiliary" at online parts sites and in Chilton
manuals.

The main injector is on top. The auxiliary is on the bottom.

For a drawing, click on "Throttle Body" 1.5 L, at
http://www.honda.co.uk/owner/ConcertoManual/index.html

This info is not in my Chilton's manual; nor at Autozone.com; nor at the UK
Honda manual site. There is very little detail at these sites re injection
rates, switching, etc.

 

+++++++++++++++++++++++++++++++++++++++++++++++++++
While trying to find a way to monitor the FI on time tobe able
to monitor fule use real time I had a dual channel oscillsocpe
connected to botht eh main adn aux FI.

There is no simple way to discribe the "firing" events.
The main cylcled pretty much the way I expected.
But the aux didn't behave in what I would consider to be
any logical manor. During cold starts the main and aux are
both one about the same times. As the engine warms up the
aux on cycles are reduced except for odd cyles that do not
relate to acceration or engine speed. For instgance,
while driving on a level stretch of highway, keeping speed
and throttle postion constant, the main chugss away more or
less like I expected. But at odd intervals the aux would cyle
on for no apparent reason.


In general any demand for increased engine RPM, ie opening
the throttle, will result in the aux opening for variable
periods. Deceleration using the engine had the aux cycling
more then the main. I finally found this link,
<http://www.ggimages.com/rx7/pwm.html>, and I use 2 of them
to monitor both main and aux. I had thought about trying to
combine the outputs so I only had to deal with one disply,
but after some practice I can now minmise my fuel consumption.

I was intrigued by the lowest intake manifold vacuum does
not translate to best fuel economy.

I am sure that a real micro computer whiz could read the data
from the ECM EPROMS and build a table that shows on ratio for
engine temp, MAP, O2, RPM and BAR but this is way beyond my
skill set.

Terry

 

It does. You can even build seperate fuel maps for each point.

The problem is manifold fabrication.

Cool thanx for the info.

 

If I'm reading what you're saying correctly, the engine mostly runs off the
upper "main" injector and just add the lower "aux" at odd intervals as
needed? I may try to make this fabricated setup to just run off the upper
only for now if that is the case given this engine is smaller and might be
able to be fueled from this one injectors flow rate..

 

hmm, the ms page has changed, but there used to be pics of people with
converted stock manifolds from ancient volvos iirc. where there's a
will, there's a way.

personally, i'd make one. at some point, a project on an old banger
like this is going to need some custom work.

 

Of course but I'm not looking for performance from this, just better fuel
control than the old hitachi carb. And converting a CIS injection manifold
to EFI would be a piece of cake compared to converting this to port
injection.

Much easier to fab up an adapter plate for a TBI unit than fabricating a new
manifold, the main bitch is the thermostat housing is on the intake and
would require fabing up water passages into it. I looked at just adding
injector bungs but there isn't anywhere to put them and get the right angle
at the ports so they'd just spray at the opposite port wall. TBI looked
like the way to go. I think for now I might just run the upper "main"
injector and see if I even need to aux one for this low HP application.
Given this engine has ~ 50HP, it's probably plenty.

And BTW I have done custom fab work when it was really worth doing for other
projects.

http://atlantaracing.tripod.com/turboz/Turbo_280Z.html

But really thanks again for your input.

 

++++++++++++++++++++++++++++++++++++
My 1991 Civic has been a test bed since last fall.
I have played around with lots of odd stuff trying
to understand the ECM better. You can fool the ECM
into thinking the secondary injector is present and
the car will start, if the enigine is "warm". I didn't
try too long but my car starts within 3 or 4 secs
worst case with both injectors. But with onlh the
primary I cranked a cold enigne for 15 sec. I don't
think the primary alone can get the mix rich enough
to start when cold.

However drivibility will be really, and I mean *REALLY*
bad. Jerky take offs with odd surges in acceration.

And during downshifting you will experience mild back
firing, more of a back burping.

I have not been able to understand why under steady load,
steady speed on a very level 5 mile stretch of road, the
primary just toggles like I expect, but the aux/secondary
opens at what certainly appear to be random events.

During downshifts it is clear. The primary shuts down and
the aux fires as determined by engine speed and presence of
breaking, ie the brake light also feeds the ECM. This is way
you are better off using the engine to slow down then to
shift into nuetral or hold the clutch in. At idle the primary
is just chugging away, during downshift only the aux is firing
and then only enough to, I think, keep the engine alive.

If you monitor the O2 sensor you will see the mix has become
rather lean.

Terry