914-SHO: X2J or MegaSquirt?

[3d914]

Is there any detailed data on the X2J PCM that would be useable to customize the input signals I won't be using in the 914?

After talking to a SHO tuner it seems like the Ford PCM is not very "user-friendly." I'm considering just going with MegaSquirt II if adjusting the PCM is that much of a pain.

Here's the pinout list for the X2J I was planning to use on the 3.2. If it's better to stay with the ATX PCM, I'm willing to go that route.

Basically, it comes down to figuring out how to handle the input for the following:

• #3 - Vehicle speed sensor (+)
• #5 - Brake on/off
• #6 - Vehicle speed sensor (-)
• #30 - Clutch pedal position switch
• #31 - Canister purge solenoid

There's gotta be a simple and reliable way to do this. Any first-hand experience would be helpful.

TIA

 

[boat]

Phoenix converted a 2002 Taurus, putting in the 94 MTX 3.2 SHO powertrain into it. If I remember correctly he had quite the wiring to figure out to get it all working correctly. Granted, Taurus to Taurus, not Taurus to Porsche 914, but still relevant. And it worked. I was looking for a specific thread of his that talked about the engine/dash wiring. Can't find it though.

 

[Shovert]

I plan on use the SHO computer but I did come across this thread long time ago. Talks of using the Mustang 3.8 computer [Adding a 36 tooth ring on crank I found a site that does them, I think someone here does it also] Seems there is more support for the Mustang stuff. Can use a computer before the PATS system. Rev limit would have to be modded. Unsure how intake runner control would be. Here is thread if want to read. Maurice
http://www.shoforum.com/showthread.php?t=108238&highlight=mustang&page=2

 

[Off Road SHO]

Gerard,

So what is the reason for not using the stock computer? If the PCM sees everything it needs to run the engine, that's all you care about, right? I don't see the problem yet.

Tom

 

[Shovert]

I agree, I have mounted the EGR solinoid and not running not lines to it since I removed that off the intake. The Mustang has the cannister purge so using this, you could just mount cannister solinoid and just hook no lines to it. Power steering switch could me wired in and not used. There is a switch mounted on the trans [mlps I think] needs a 400 ohm resistor to fake it [since don't have the SHO atx]. Mount a brake switch. Sounds like easiest way to do it. Maurice

 

[3d914]

Good input guys - thanks. Let me digest it & I'll reply more.

To answer Tom's question - the tuner wants to install a new chip ($$) and perform $$$ dyno tuning - mostly to cover liability (which I understand). I just don't see why it's so complicated - unless Ford makes it so. If I can't effectively & reliably hack the stock PCM, then I'll just build a MegaSquirt to get the job done.

 

[Off Road SHO]

That's what I'm having trouble understanding. The stock PCM will get the job done just fine. What is it that you think it wont do?

Tom

 

[rubydist]

Basically, it comes down to figuring out how to handle the input for the following:

• #3 - Vehicle speed sensor (+)
• #5 - Brake on/off
• #6 - Vehicle speed sensor (-)
• #30 - Clutch pedal position switch
• #31 - Canister purge solenoid

There's gotta be a simple and reliable way to do this. Any first-hand experience would be helpful.

TIA

I think you can ignore the vss, boo, and purge solenoid inputs. the only one you need (iirc) from your list is the clutch position switch - at least it needs to think the clutch is pressed in to allow start.

I agree w/ Tom - unless you are going boosted, the stock pcm program will work just fine. if you are going boosted, then a tune on a chip will be much less work than an aftermarket controller, imho.

 

[3d914]

I like what I'm hearing so far, but let me do some clarifying. (REF: Going normally aspirated, stock intake & sensors)

First - Can I expect the X2J (3.0 PCM) to run the 3.2 correctly from a fuel mapping/displacement position?

And if so, how does one go about verifying - is there Fuel mapping data available for the two engines (3.0 vs. 3.2)? Or does the PCM even care about the displacement difference?

 

[Phoenix]

As far as engine fonctionality , I dont think it would made any differances to run a 3.0 with a 3.2 harness and vice versa. The 3.0 has 24lbs injectors anf the 3.2 has 24.4 lbs. I dont know if the fuel maps are differant though , but it will work. The 3.2 swap is something real common in the sho world for years.

The 3.2 harness will have more connectors for the ATX/EGR. You cannot put a 3.0 ecm with a 3.2 harness (and vice versa), you also MUST mmatch the ccrm with its harness. Plus you cannot mismach the 3.0 dash harness with a 3.2 underhood harness, It wont plug together and the wire colors are differant.

If you want less hassle , begin to strip down a 3.0 harness , it will be less work for you. Make sure you have the Ford elecrical book of the year of the harness you have in hand. These books costs about 10 bucks on ebay.

 

[3d914]

Phoenix, I agree with your approach on the harnesses, but you realize my main concern is with the PCM and not the wiring harness? I just want to be sure I can run the 3.2 motor using the X2J (3.0) PCM.

Maurice, agreed that the switches could be easily replicated or wired; Brake On/Off and Clutch pedal.

The one input that I'm really unsure about is the VSS, and also the Canister Purge output. It appears from the schematics that the VSS is only used for Cruise control, but I'd like to verify that. Don't like guessing.

Can the Canister purge output affect air/fuel ratio or manifold pressure? Can't seem to find much about it in the engine book I have. I'm not opposed to re-adding the solenoid and valve - I'll just locate them off the surge tank.

 

[rubydist]

you can run the 3.2 with the 3.0 pcm without issue. many guys have done the 3.2 swap and always continue to use the 3.0 pcm.

the vss is used for at least 2 functions on the mtx pcm - one is the cruise as you have identified, and the second is the high idle, which is maintained until the car is below about 10 mph at which time the pcm drops the idle to the stationary idle speed.

purge canister output is only used to turn on/off the charcoal canister purge solenoid. some of the atx pcm's have a problem with the driver for that, and I had my red 94 wired to purge the canister all the time because of it, and had no issues with that whatsoever. so it is safe to ignore that completely.

 

[Phoenix]

Like he said , just make sure that the PCM follows its harness. 3.0 pcm with 3.0 harness. Doesnt matter if its a 3.2

 

[3d914]

Excellent guys, thanks for puttin me back on track. Glad I listened to my gut (and your input) and not just some "expert" tuner.

 

[3d914]

I think you can ignore the vss, boo, and purge solenoid inputs. the only one you need (iirc) from your list is the clutch position switch - at least it needs to think the clutch is pressed in to allow start.

One more thing to clarify with the clutch position switch. Once the engine is running does the PCM care whether this switch stays closed - or will it look to see that its open at any time (clutch engaged)?

This thread implies there are two CPPs. If so, how do I distinguish them in the wiring?

 

[Phoenix]

One more thing to clarify with the clutch position switch. Once the engine is running does the PCM care whether this switch stays closed - or will it look to see that its open at any time (clutch engaged)?

This thread implies there are two CPPs. If so, how do I distinguish them in the wiring?

In my 2002 the switch is gone and its thinking its pressed all the time. No worries everything works fine , it does nothing except preventing you start it while in gear.

Now I can start it in gear witch is something you need to think everytime you start it. Clutch in , start.

 

[3d914]

This thread implies there are two CPPs. If so, how do I distinguish them in the wiring?

What about there being two CPPs?

 

[Off Road SHO]

What is a CPP? Never heard of it.

As far as the Clutch safety interlock switch goes, its only purpose is to prevent the starter from being engaged unless the clutch pedal is depressed. That switch interrupts the 12 volts on the way from the ignition switch on the steering column to the starter relay. The starter relay could be on the starter's Bendix housing if it's a Gen 2 or on the driver's side fender well if it's a Gen 1.

Tom

 

[3d914]

Tom, CPP is the reference used by Pavlin PCM diagram for Clutch Pedal Position switch. My main question was whether the PCM cares, once the engine is running, if the switch remains closed?

 

[Off Road SHO]

I don't think it cares either way. The PCM doesn't even know when you send power to the starter solenoid via the clutch interrupt switch. Once you turn the ignition switch to start and push in the clutch, only then does 12 volts get sent to the starter solenoid and the DIS module.

Tom