Programmable ECU's (Was GM TPI tips for a newbie)

[Raymond C Drouillard]

A couple of points:

Holley makes some analog systems, but at least two (4D and 4Di) are
digital.  Both have O2 sensors and run in closed-loop mode quite well. 
In fact, they work without even being programmed in closed-loop mode at
cruise, though they get really stupid when you step on or release the
throttle.  A little programming and they run beautifully.

Some of the older kits have a closed-loop kit, which is an O2 sensor and
an extra box.  I have seen a picture of it, but know nothing about it
beyond that.

The Holley Pro-Jection 4Di box gives you unparelleled programming
ability, and the ability to record every sensor, play it back, graph it,
export it to Excel, or whatever you want to do for tuning purposes.

The 4Di unit will also control your spark advance.

What you said about a "wet" manifold is all true.  I have found that it
doesn't cause me any trouble, however.  Part of this might be because all
of the runners in my Edelbrock Performer manifold are the same size and
shape (except perhaps mirror imaged), with the exception that the lower
plane has a bit more vertical travel right under the throttle body.

Hey, it worked well with carburaters, and works even better with fuel
injection.

Ray Drouillard
'89 Jeep Grand Wagoneer
Pro-Jection 4Di (and other stuff)


On Fri, 15 Jan 1999 02:57:28 +0000 Frederic Breitwieser
<frederic.breitwieser at xephic.dynip.com> writes:
> > Which system(s) is/are considered the best?
>
>Well Charles, they are all good, and they all suck.  <grin>
>
>The Holley Projection system is more of an analog system,
>like a carbeurator, with enough sophistication to make for a
>reliable, stable air/fuel system.  Advantages are that its
>replaces your carb, so your regular everyday existing intake
>manifold would be just dandy, thus reducing the overall cost
>of converting to EFI.  Another advantage, is you can change
>the settings very easily, using either a "black box" or a
>laptop, depending on which model you buy, and update your
>settings if you decide to toss say, your stock cam, and
>through in a "thumper" cam.  Its flexible, adaptable, and
>works out of the box.  There are two major drawbacks that I
>see - first, it uses your intake manifold, which means your
>rough idle due to fuel "sheeting" on the walls of your
>intake manifold still exist, and it doesn't utilize an O2
>sensor (that I know of), therefore its not a feedback
>system.  If you are concerned about emissions, this
>obviously can become a problem.  Throttle Body EFI, where
>you have few injectors (one to many) servicing many
>cylinders, all experience this sheeting problem in a worse
>case scenario.  Sheeting is when the fuel collects along the
>intake runners, then as the miniscus of the fuel is
>exceeded, it slothes off into your cylinders.  Another
>example of a miniscus is when you overfill a glass of water,
>and have the water higher than the glass, in a sort of
>bubble - this is the miniscus - or the natural attraction of
>molecules that is stronger than the force of gravity against
>its own weight.  Sorry for the horrible explaination, its
>been ages since I've opened a science book.  The other draw
>back of a wet-style manifold is that certain cylinders
>typically get more fuel than others, since the carb unit or
>throttle body is located in the center - takes fuel longer
>to travel longer distances.
>
>Now, this means my opinion is that multi-port EFI offers a
>lot of advantages.  First, is the sheeting problem
>disappears entirely.  Because air is much more movable than
>fuel, your manifold design is not as mission critical as in
>a wet design, therefore you can get away with a lot more so
>to speak in manifold use/design/construction.  Also, most,
>if not all, multi-port injection systems (like Electromotive
>& Haltech, two name two of many) can control each injector
>independantly, based on feedback from an o2 sensor.  This
>means that your computer, based on RPM, load, temperature,
>manifold pressure of vaccuum, can determine the "right"
>amount of fuel necessary to match the airflow, which you as
>a driver determine with your gas pedal.  This higher level
>of control obviously is more desirable, especially in a high
>performance/low emissions application, but it really costs
>more.  You have more sensors, fabrication if you are not
>using and OEM EFI system on a similarly styled
>same-manufacturer engine (as in, late model camaro EFI on a
>1969 Caprice, for example).
>
>I've never had the opportunity to play with the DFI system,
>however I have played with both the mid 80's OEM GM systems,
>as well as the Haltech ECMs and the Electromotive ECMs.  For
>flexibility and control, I prefer the Haltech.  I managed
>with a little electronic add-ons to drive three injectors
>per cylinder mixing different fuels into a twin-turbo V6. 
>With the Electromotive unit, I struggled and struggled to
>get it right, which I never did.  Don't get me wrong, the
>Electromotive is a good, reliable unit, and their tech
>support is really good.  I asked them a lot of stupid
>questions and they were patient and gave me a lot of good
>answers.  When they didn't know, which was rare, they stated
>such.  I also found that the electromotive units were easier
>to start off - the "Maps" for generic engines were
>reasonable and close to what I needed, therefore instead of
>spending a day entering data, which are guesses at best, I
>could use an existing map or profile, and "tweek" from
>there.  In contrast, the Haltech unit was significantly more
>flexible, but at the cost of being able to attach, turn on,
>and at least start the motor and tweak from there.  The
>included maps didn't fit my application at all.  THough, I'm
>sure Haltech doesn't have lots of call for twin turbo 3 inj
>per cyl V6 applications, to be entirely fair.
>
>One of my many slow moving projects is to convert a Chrysler
>383 stroker (431 cid) to run under the OEM GM system I have
>leached from a junkyard, including all sensors, MAP, O2,
>water temp, crank, etc.  The intake on the 383 has already
>been milled to support an injector per cylinder, however I
>have not welded in the bosses yet.  I still have the engine
>apart trying to figure out the insides.  Anyway, long story
>short, the only issue I see is fabricating the crank sensor
>mounting bracket, and making it adjustable incase my bracket
>is off.
>
>There is a book by Jeff Hartmann, called "Fuel INjection
>something", I don't recall the exact title, but it does
>cover installation and tuning of the Holley system, the
>Haltech system as well as the Electromotive system, and
>basic theory, math formulas, in case you want to fabricate
>your own system either from scratch, or from oem parts and
>ECMs.
>
>While this is not the answer you want to hear, I can't say
>for sure that any one system is better than the other.  They
>all have advantages and disadvantages over each other, and
>different price ranges to boot.  I'd highly recommend Jeff
>Hartman's book - for 20 bucks it gives you a good overview,
>and some actual installations on specific units, and from
>there, you can make a better choice.  Sorry I don't have the
>exact title, but it has a black cover and you can't miss it
>:)
>
>
>-- 
>Frederic Breitwieser
>Bridgeport, CT 06606
>
>http://www.xephic.dynip.com
>1993 Superchaged Lincoln Continental
>1989 500cid Turbocharged HWMMV
>1975 Dodge D200 Club Cab
>2000 Buick GTP (twin turbo V6)
>

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