Holley ProJection stuff

[Bill the arcstarter]

OK, I'm sending this to the diy_efi list and to the 2-3 people who have 
e-mailed me about the ProJection system.  I'm not sure if this should be 
discussed on the diy_efi list.  Can anyone comment?  I'd think this stuff 
should be public but I don't want to dump on the list if nobody wants to 
hear it, etc...

At any rate I think us ProJection users should at least be aware of each 
other, etc...

I just acquired a very lightly used (99% brand new) 900cfm 4Di about 2 
months ago.  I had a slight problem with that unit, as some old gas had 
dried up and clogged one of the injectors.  Nothing a good soaking in the 
ultrasonic tank at work wouldn't fix! :)

I think the only difference between the 700 and 900 cfm unit is the size of 
the injectors, ie, throttle bore size is the same I think.  Can anyone 
verify this?

Primary inputs into the fuel map are engine RPM, and MAP Manifold Abs 
Pressure.  The value extracted from this table is modified by a choke curve, 
accel pump function, and oxygen sensor trending (integrator).  There is also 
an intake air temp sensor.  I would expect this to enter into the equation 
at some point.  The fuel map is 16 x 16 with 8-bit resolution of injector 
width (0-255).

Holley gets a D- grade for not providing a theory of operations section of 
the manual.  The manual is written just for an installer IMO.  Very little 
description of cause and effect - just "do this, do that...".  Certain wires 
were not even identified!  Outrageous.

There appear to be several "regions" of oxygen sensor integrator, as each 
one will take over depending on if you are at idle, light, or heavy 
throttle.  This is not documented.

Apparently the software does NOT have a one-parameter for lbs/hr of the 
injectors, etc.  This means the basic maps provided have to be heavily 
tweaked depending on the injector size, etc.  At least this is how I see it.

Summit has new 85lb/hr injectors for the 4Di injection head for $69 or 
something like that.

Anyway I've installed this unit on my somewhat whipped 350 chevy in my 
beater '84 Suburban (doubling it's value in the process).  But I figured I 
needed a "mule" to test it out.  Plus it was the biggest V8 I have in the 
driveway.

The hardest part of the installation was the fuel system.  I ended up 
mounting the electric pump in the front, inside the frame rail, more or less 
under the radiator.  I used the stock fuel supply line, but plumbed a new 
return line (3/8 copper tubing).  I hope nobody knows anything BAD about 
using copper tubing in a fuel system... :?  Took me about three days to plan 
and install (to my satisfaction) the fuel system.

I 'T'-ed into the "tank too full" fill tube (the hose which sprays gas on 
the filling nozzle when you refuel at the pumps) back near the fuel door for 
the return line.   Couldn't use the stock fuel return line - too much back 
pressure (measured it).  But this "T" works great!

Had to use a $15 manifold adaptor to convert from spread to square bore.  
Not sure what effect this would have on overall performance.

The other annoying thing was the O2 sensor.  I decided to remove the 
driver's side manifold, and drill/tap for the O2 sensor.  18mmx1.50  :) Not 
too hard and made for a neat installation - as the O2 sensor sticks out of 
the side of the manifold.  Sure beats trying to mig on a O2 bung while lying 
on my back under the truck...

I'm not using the spark advance or knock sense since I don't have the proper 
components.  Yet.

Anyway - I'm still fine-honing the fuel map for the recommended -10 to  -20% 
on the oxy comp.  Usually I do this via Hondo logging sessions, driving at 
different rates, foot on the brake, up/down hills etc.  I'd say the Hondo 
program is Mandatory for getting a nice final map - not sure how it'd be 
done w/o either hondo or a dyno! :)

The minimum injection duration (1700 us supposedly) is too long for a clean 
burn at no-load speeds>1500 rpm.  This includes revving in the driveway, or 
rolling downhill, etc.  Excessive hydrocarbons are produced (I can smell 
them).  I haven't fooled with the fuel pressure yet - that might fix this 
but would require more map modifications too.

The logic used for the O2 compensation voltages is rather odd and kludgy 
IMO.  There is an undefined "operation mode" variable, from 0 to 4 or 
something... I'd be happier if the system contained an array of integrators 
parallel with the main fuel map, like the GM ECU's do...

The cold start "choke" system works just fine.

I've seen a few odd things with this system.  On three occasions, the O2 was 
reading rich, but the O2 compensator was INCREASING, adding injector 
duration, until the motor actually died from excessive fuel.  On all three 
occasions it was at idle when this happened.

This throttle body will flow a LOT of air!  At 4000 rpm I get 99% of full 
atmospheric pressure on the MAP at under 30 % of full throttle opening.  
This makes for a very sensitive accelerator.  I need to re-linkage this to 
make it less sensitive.

Once for whatever reason it wasn't reading the MAP.  That made for some 
interesting malfunctions...  Power down/up and all was well.

So far I've been impressed with how well it works.  I get MUCH more power 
than my old Roch. Quadrajunk unit (no offense but I hate that old thing).  
'Course some of that is perception - due to the fast-acting throttle action, 
etc.

I haven't been driving it in a sane way to see if gas mileage has increased. 
  I would suspect it has.

My idle is rather rough with this unit.  Not sure if that is because the 
host engine is sort of tired, or since this injection head is rated 900 cfm 
(ie - too big) or ?? something else...  The idle is very smooth if I turn 
off the oxygen sensor and just run raw uncompensated fuel map at about 10% 
rich...  Not sure how to interpret that.  Plugs, wires, coil, cap etc are 
new.

Next on the agenda will be cam, intake, exh, and head refreshening.  Then 
we'll really be rolling!  Wonder if the transmission will take it? (700R4)

Comments encouraged.
-Bill


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