The EECIV, the MAP, and supercharge...

[brokencase]

Just a little brainstorming...

The MAP sensor outputs a square wave signal to the EECIV. This signal changes frequency with absolute manifold pressure.
It goes from a low of about 80hz at very low vacuum up to around 159hz at 14.7 psi absolute (WOT). The EECIV measures the period of this square wave to determine the pressure.

Now, if I drive my Scorpio up into the Rocky Mountains to around 12000 ft. pressure drops to around 9.3 psi absolute.
It's a big pressure change, but the Scorpio still runs fine. It just has a concordant loss in power because the air is now thinner.

I doubt the EECIV/MAP can manage large positive manifold pressure at sea level. I suspect the EECIV will consider any substantial positive manifold pressure as a "MAP sensor out of range" and it will issue a code. It has to handle some small positive pressure above 14.7 absolute because the car must run in those rare places that go below sea level or if there are substantial pressure changes on account of the weather. But it is not much, maybe 1-2 psi above 14.7 absolute.

So lets go back to sea level and install 22lb injectors in the Scorpio (versus the standard 14lb injectors).
As some intrepid members of this forum have discovered you can't do this (I think Brad tried to install 17lb injectors).
This does not work. The engine will run too rich.

Now, with the 22lb injectors installed, lets put an Arduino between the MAP and the EECIV and have it scale the frequency of the MAP down by 30%.
Actually lets be smart about it. Lets hook up a small potentiometer to the arduino so we can tune the scaling.

Presto! the EECIV now thinks we are at 12000 ft and it shortens the pulse width to the 22lb injectors accordingly and the engine now runs fine at sea level.

More importantly, since we have now reduced the MAP frequency by 30%, we can now apply positive manifold boost and still stay under the 159hz limit and the EECIV won't detect an out of range error.

Now I am making a few assumptions with this line of reasoning...
1) Will the MAP sensor keep increasing it's frequency as we go above 14.7 psi absolute?
2) Does the EECIV have some sort of "minimum" pulse width check to the injectors?

Item 1 I could overcome by building my own MAP sensor.
Item 2 would be a deal breaker. With 22lb injectors installed, there would be conditions where we would need a pulse width to the injectors that would be smaller than what it would have had with the 14lb injectors, like around idle.

"That's all it takes, really, pressure and time." The Shawshank Redemption.

[brokencase]

I'm thinking...
Remove upper manifold. Build adaptor plate for Eaton M90. install pulley to achieve 6 psi boost.
Move throttle body to rear of Eaton supercharger.

Install MAP Arduino circuit.

With 6 psi we should now have 200 bhp.

The neat part is before all the above... just install 22lb injectors and the Arduino circuit and see how well it runs.
If that works, then I am assured that the supercharger will work.

I should be able to "tune" overall mixture with the potentiometer on the Arduino.

Your thoughts?

[my8950]

If you're really going that far, you might be better off to just use a microsquirt.
I can't comment on the BAP sensor going about 1bar, my guess is, it would not, because there really isn't any reason to.
You could try it though by rigging one up on the bench and put a scope on the output pin, then use a mityvac hand pump to put pressure on the port.

[Fresh Air Inspector]

Hello Brokencase,

Interesting brainstorming.

Just wondering, what does the EECIV do when the MAP sensor fails? I can't imagine the engineers allowing the vehicle to die so some sort of limp home mode would happen. Would be interesting to see the waveform output as it would be some form of broad spectrum to allow drivability under most conditions?

In a pervious life I was technical support / trainer for medical equipment and one of my tasks involved regular testing of hospital blood pressure monitor accuracy. This involved the use of a very accurate piece of test equipment incorporating an extremely accurate pressure transducer. It used a standard 4 - 20mA current output (9 - 36V input voltage). The pressure / vacuum transducers are not very expensive and may offer a more flexible MAP sensor for your potential application.

Hope it helps.

[brokencase]

FreshAirInspector - I believe what the EECIV does in the case of MAP failure is it falls back to a calculation for pulse width based only on RPM and the engine's displacement.

my8950 - Think of all the trouble of installing a megasquirt versus installing this simple translator on the MAP.

[Ed Lijewski]

MAP sensor (Scorpio) is the same as BAP sensor (XR).

Scorpio uses MAP for absolute intake manifold pressure.

XR uses BAP only for barometric air pressure reading .

XR (turbocharged) uses Vane Air Meter for speed density calculation of intake pressure.

Cosworth Scorpios (NA) use dual VAMs, one for each intake side (speed density calculations).

One assumes that Cosworth Scorpio EECIV tables are expansive beyond Merkur Scorpio tables enabling higher performance.

On the Merkur Scorpio, determine if simple Scorpio Cosworth EECIVs can be swapped in with wiring modifications for a BAP and dual VAMs and larger injectors.

YMMV

[brokencase]

Bigger problem is fitting a roots style supercharger.

I thought I could just build an adaptor for the Eaton M90 to mount to the Scorpio lower manifold until I realized the injectors and distributor are in the way.

Oh well.. All is not lost as this approach does allow for the fitting of larger injectors if performance is increased by other means. Like stroking with the 4.0L crank.

[brokencase]

Ed, I am pretty sure VAM is not speed density.

The US Scorpio is a speed density system.

[brokencase]

This might be a way to do it....
Jeep Cherokee roots blower.
https://www.ebay.com/itm/403070495873

Maybe mount it over on the A/C side.

Make an adapter to mount the Scorpio throttle body and ICS to the inlet side of the supercharger.
Outlet gets plumbed into the Scorpio intake with another adapter.

[john keefe]

If you mention circuitry and Arduino, I'm already at the back of the class, but I like the concepts proposed, and if you can "trick" the PCM by a simple alteration of a signal, that's a great solution. But, in my recollection of all the testing and experiments back when the 5.0L and 2.3L were being tweaked by everybody and every magazine, weren't the most effective solutions (albeit initially most expensive) changing the actual PCM tables via a chip without altering the sensor signals? Or, for an even higher price-tag, going to a stand-alone system but which also required extensive dyno tuning? At least with a chip, once you have the tables correct, its just a matter of reproducing the chip on a large scale for the "masses" (e.g., "Superchips," Edge, etc.).

I haven't thought that much about the 2.9L (if it ain't broke, etc., and you've got something else to play with for power), but, it seems the root issue is an inherent weaknesses in the 2.9L as an air pump, rather than the EEC-IV? I don't know what that issue is, but I do know that (until Cosworth redesigned the head and exhaust), FMS-UK predicted the most HP they'd ever get out of a NA 2.9L was under 280HP, and that's with major upgrades of internal components. Which is why the first iterations of the Sierra weren't very good in WRC until the RS's came along.

Is that Eaton M90 the blower from a TBird SC? Or, for space savings relative to the upper, maybe a centrifugal SC. You've got room ahead of the block, but maybe not an easy task with stock pulleys.

[brokencase]

John -The goal is to find and easy and inexpensive way to get more power out of the 2.9L.

In my opinion the MAP adjustment along with larger injectors will work. Manifold pressure is the dominate parameter that determines the final injector pulse width. By hijacking the MAP signal we are essentially making our own performance ECM solution.
By running the tach signal into the Arduino we could even create our own adjustable fuel map if required. But I am quite confident the simple scaling of the MAP and installing larger injectors would work fine.

As I indicated the Eaton would not easily adapt. But the other roots supercharger I mentioned above would be a viable option. Belt driven and mounted off to the driver's side.

Toughest part of this project would be re-routing the cable/linkage to the relocated throttle body.

I'd like to do this in such a way that everything could be returned to stock configuration if desired.

[brokencase]

It looks like that supercharger I mentioned was originally mounted on the Toyota Previa.
Built by Aisin.

From Wikipedia...
"Starting with the 1994 model year, Toyota attempted to rectify engine performance by fitting a Roots-type supercharger with air-to-air intercooler, providing six psi of boost (these models were called the "S/C"), bringing the engine power up to a competitive 158 hp (118 kW) and increasing fuel mileage from 17 to 23 mpg‑US (14 to 10 L/100 km). Initially, the S/C engine was only available as an option on the LE for the 1994 model year and all models for 1995."

This engine was a 2.4 Liter I4 with a normally aspirated rating of 130hp and a compression ratio of 9.3 to 1.

[andyofcolumbusmerkur]

In my opinion the MAP adjustment along with larger injectors will work. Manifold pressure is the dominate parameter that determines the final injector pulse width. By hijacking the MAP signal we are essentially making our own performance ECM solution.
By running the tach signal into the Arduino we could even create our own adjustable fuel map if required. But I am quite confident the simple scaling of the MAP and installing larger injectors would work fine.

That is basically what quality turbo kit makers do. You have your cheapy ebay turbo kits for a car like a 1999 Acura Integra GSR, which only rely on the rising rate fuel pressure regulator. Then you have a kit like the one Greddy makes. Which has a little box you splice into the ECU's wiring. I'm not real familiar with the APEX-I type air fuel controllers but that could be a possible solution.

[john keefe]

John -The goal is to find and easy and inexpensive way to get more power out of the 2.9L.

In my opinion the MAP adjustment along with larger injectors will work. Manifold pressure is the dominate parameter that determines the final injector pulse width. By hijacking the MAP signal we are essentially making our own performance ECM solution.
By running the tach signal into the Arduino we could even create our own adjustable fuel map if required. But I am quite confident the simple scaling of the MAP and installing larger injectors would work fine.

I'm all for that. A single/simple tweak for improved performance is always nice, even if just a minor bump. Begs a question for me, though, and again I'm not all that up on the capabilities/limitations of the 2.9L... doesn't that assume there is a lot left on the "stock" architecture/component table that's sitting there "waiting to be unlocked?" How much of a bump in performance might you expect from fuel/timing alone?

Not being negative in the slightest, but I only have the 5.0L to compare at this point. Typically improved fuel flow, even when coordinated with ignition timing scaling yields only a minor bump unless accompanied by, or following mechanical improvements (improve air flow, different cam, head porting, better exhaust, stroker kits, improved/resized intake manifold/TB/MAS, etc. ).

Then again, there's a lot of potential performance if the engine has been so de-tuned or choked for the street/smog, like the V8's during the 70's fuel crisis. All you needed was a better carb and manifold, and headers, bypass some hoses, and you were basically back to near muscle-car power. So, are you thinking this is a "all it needs is X" to wake up, or more a Stage 1 thing, and hence the SC? What do you think would be the next component to accompany this tweak to really wake it up? Exhaust? Porting?

[brokencase]

I'm not looking to get a ton of boost here. "They say" if you stay below 5 psi you don't need an intercooler.

4-5psi would be fine. I'm confident the 2.9L could manage it (running premium, of course).
The Previa ran at 6psi and had a small intercooler. I am not against routing the pipes for an intercooler. That is actually easy work.
The rice rocket boys have made intercoolers and associated plumbing cheap and plentiful.

I think with 5psi it would make around 185-195hp.

Popped the hood today and looked things over.
Need to re-route the A/C line. Suspect I could do some TIG aluminum tubing work to manage this.
Need to relocate the EGR - Not too bad. They make corrugated/flexible stainless tubing and that's what I would use for this.
I would probably fabricate a bracket that bolts the EGR valve further back to the heat shield over the drivers side exhaust...which is probably better than the original arrangement anyhow.

Moving the throttle linkage it tricky. That complicated bracket bolted on the intake is mainly for merging the cruise control function.
However. I am willing to sacrifice cruise control to simplify this installation.

So here is "the vision"..

The supercharger mounts over the A/C compressor area and shares the drive belt with the A/C. A new, longer belt is utilized.
Bracket engineering required to mount and tension the supercharger. Probably will have to machine my own custom pulley to get the right boost.
A/C line is re-located by welding a longer aluminum tube section.
The PFE sensor and EGR are relocated.
Throttle body and ICS relocate to the the inlet side of the supercharger....along with all vacuum lines.
A special adapter between throttle body and supercharger is welded up to manage all this.
The air cleaner remains where it is, but new, shorter rubber pipes now feed to the throttle body, which is now closer to the air cleaner.
The outlet of the supercharger now goes to an divergent adapter to the intake. The original ICS mounting location is blocked off with a plate.
All vacuum lines are now moved over with the throttle body adapter
20lb injectors are installed. ( I was wrong about 22lb earlier)
MAP sensor translation circuit is installed.
I think static timing should be retarded by about 3 degrees.
The hose from the intake to the absolute pressure sensor and fuel pressure regulator probably now need hose clamps so they don't "blow off".

Optionally...
Supercharger blow off valve.
Route through an Intercooler.

Most importantly. Everything is done such that it can be reverted back to stock in needed. For example, I don't hack the original pipes and fittings to the EGR. I make all new stuff.

First step would be to install 20 lb injectors and the MAP translation Arduino and see how it behaves.