The Mule rides again (sort of) - pics.

[The Dark Side of Will]

BMW mounts their DME (digital motor electronics) underhood, but the boxes are mostly sealed and actually ventilated by cabin air via a duct through the firewall... I was wondering about going to moderate lengths to implement something like that in The Mule.

Basically, I just need to figure out the PCM's permanent home before I do my upcoming round of engine-out mods (late summer?) so that I can build a pimpin' wiring harness when it is out.

[Sinister Fiero]

In most cars, GM mounts the PCM in the airbox. It sees some limited air flow from the normal engine breathing process, but it's not normally in direct air flow. But in most trucks, it isn't mounted in the airbox at all and just hangs out there where hot radiator air can blow on it.

I just had to ship a replacement 0411 PCM to a customer because whoever previously did the swap, pulled unused wires out of the connectors when they did the wiring and didn't seal off the open terminal holes nor did they pack the connectors with grease. I know his PCM was mounted in the engine compartment (this was a Fiero) but I don't know where or how. Evidently, moisture found its way into the connector and completely corroded one of the terminals off of the PCM itself. I think it was a 5v reference circuit terminal.

[The Dark Side of Will]

I'm well aware of what corrosion can do if inadequate preventative measures are taken.

Keeping the PCM inside the car will be an option I'll consider for its final home.

By "most cars" do you mean most 3800 cars? I'd like to snag such an airbox and take a look at it.

[ericjon262]

I'm well aware of what corrosion can do if inadequate preventative measures are taken.

Keeping the PCM inside the car will be an option I'll consider for its final home.

By "most cars" do you mean most 3800 cars? I'd like to snag such an airbox and take a look at it.

almost all of the V6 cars have them mounted in the airbox. 60* or 90*

[Sinister Fiero]

*Most FWD cars and minivans. But I wouldn't mount it there. If it isn't too much of an issue, I would mount it inside the passenger cabin. This location just has less risk of the PCM being exposed to moisture.

And I had assumed you knew the potential problems corrosion could cause. I did not mean to make it sound like you were ignorant of that fact.

[The Dark Side of Will]

I didn't mean to sound snappy with that statement... just that I am aware.

I had always assumed that's why GM mounted the stock V6 computer with the connectors down, even though the wiring was longer... in order to cause any condensation or moisture to move away from the electrical contact point.

I've also worked in aerospace, where weird types of corrosion are a big deal and one-off electronic components may sit on the shelf for years before being used, giving incompatible materials plenty of time to chemically ruin each other.

[The Dark Side of Will]

*FINALLY* have the valve cover leak fixed. I replaced the front valve cover seal over the weekend. *NOT* an easy job with the engine in the car.

The old one had a couple of big gashes in it. I blame the installer.
Brief history:
Used new seals to button the engine up - no problems
Forgot that seals are one-time-use and removed covers to retorque head studs; reused old seals because I had to get the car buttoned back up - both leaked
Replaced both seals - rear sealed up, front was damaged by improper installation
Replace front seal *again* - seems to have taken this time

I bought the new seal from GM instead of CarQuest. One cover seal and 4 plug well o-rings from GM were almost as expensive as the entire kit for both covers including bolt grommets from CarQuest.

However, the GM seal stayed in the groove better than the CarQuest seal did. I took my sweet sweeet time making sure it was stuck in the groove, and then lifted up each corner after I'd started all the bolts to be sure it was still retained in place.

The old seal was red. The new one is blue. I worried that my car would be slower with less red on it, but the old plug well o-rings were black, while the new ones are red. I'm not sure if the car will be faster because it has more red parts, or slower because the total amount of red material is less. The timing lights will have to tell that story.

Two conditions for return to dyno have been met (knock sensor and valve cover leak). Now on to the intake tube.

Also getting some of what sounds like accessory belt flutter above 6500 RPM. I'll have to rework that soon, I guess.

[The Dark Side of Will]

I have crappier tires on it now than I used to, but the car's scrambling for traction in 1st gear in warm weather now. It used to hook up in first on warm pavement.

It doesn't just break loose and spin, but I can feel momentary wheel slip all the way up the tach when I roll into it in first.

[Sinister Fiero]

I didn't mean to sound snappy with that statement... just that I am aware.

No worries, and I wasn't trying to come off as though you didn't know any better because I know you do.

I had always assumed that's why GM mounted the stock V6 computer with the connectors down

They usually don't. The only cases on V6 and 4cyl FWD applications where I've seen them mount the PCM with the connectors down was on Grand Ams and like bodied cars where the PCM is mounted INSIDE the car up under the dash next to the steering column. When they mount them in them outside in the airbox, they usually lay them flat.

[The Dark Side of Will]

The interior E/PCM's do not have weather-tight connectors, while the under-hood PCM's do. Mounting the interior ones with the connectors down would be necessary, while the under-hood ones could be mounted flat with no long-term effects.

[Sinister Fiero]

The interior E/PCM's do not have weather-tight connectors, while the under-hood PCM's do. Mounting the interior ones with the connectors down would be necessary, while the under-hood ones could be mounted flat with no long-term effects.

1996-newer Grand Ams and like bodied vehicles use the exact same PCMs as other FWD GM V6 cars. The only difference is I've found is the Grand Ams and like bodied cars that had these PCMs mounted inside under the dash got all-plastic PCM connectors that do not have a silicone seal in them like the under-hood metal connectors do. But aside from that, the connectors look virtually the same aside from the color.

The PCMs themselves are NO different.

[The Dark Side of Will]

It's a graph. It has numbers. It scanned crooked because it was printed crooked.

I'm not sure what was done between the 306 ftlbs run and the 301 ftlbs runs. I hope that will be straighten-outable on my return to the dyno. I'd also like to get him to do some work between 1000 and 2500 RPM, as that's where I do most of my driving, and it's still a bit lumpy in that range.

Also need to be sure the tuner looks at peak injector duty cycle, so I know how much horsepower head room I have before I have to start looking for injectors.

[Sinister Fiero]

Tailpipe Wideband o2 or one installed in the exhaust close to the engine?

[The Dark Side of Will]

I brain farted this time and forgot to have him install the sensor in the bung I added to the X-pipe specifically for that purpose until after he had strapped it down to the dyno.

When I go back for the touchup tune I'll have it in the X-pipe for better readings.

[The Dark Side of Will]

The quarter panel volume below the pass-through for the fuel filler and intake tube is approximately 6" front to back, 11" side to side and 12" vertically from the bottom of the pass-through opening (just above the top of the frame rail) to about the same level as the coolant pipe.

[The Dark Side of Will]

Check out p/n: RU-3130 for the universal cone filter.

http://www.knfilters.com/search/univcone.aspx

Also checked out RF-1045 and RC-4760, but went with the 3130.
The K&N website wants $50 for one, but Summit and Amazon both get $31 for one.
Ordered.

[Sinister Fiero]

If this is an inside a building dyno cell, I recommend having them tune the WOT AFR to 12.5 - 12.8:1. I know the "magic" AFR for N/A engines is 13.0:1. But with your car sitting on a stationary dyno inside a room, it isn't getting the same volume of clean air it will see driving down the road. Every car I've dyno tuned ran leaner on the street vs. what it did on a dyno moments before. Of course, the only way to really know what the AFR is doing on the street is if you are running a wideband O2 and display gauge in the car.

[The Dark Side of Will]

If this is an inside a building dyno cell, I recommend having them tune the WOT AFR to 12.5 - 12.8:1. I know the "magic" AFR for N/A engines is 13.0:1. But with your car sitting on a stationary dyno inside a room, it isn't getting the same volume of clean air it will see driving down the road. Every car I've dyno tuned ran leaner on the street vs. what it did on a dyno moments before. Of course, the only way to really know what the AFR is doing on the street is if you are running a wideband O2 and display gauge in the car.

On the OBDI hardware, people connect the 0-5V output of the wideband controller to the EGT pintle position feedback wire in order to have a value which can be translated to measured AFR present in the datalogs. There are even patches for some code masks which change the interpretation formula within the ECM so that the value it reports in the datastream is AFR rather than EGR position.

[Sinister Fiero]

On the OBDI hardware, people connect the 0-5V output of the wideband controller to the EGT pintle position feedback wire in order to have a value which can be translated to measured AFR present in the datalogs. There are even patches for some code masks which change the interpretation formula within the ECM so that the value it reports in the datastream is AFR rather than EGR position.

You could use the same input on the OBD2 PCM, but as far as reconfiguring the OS to spit out an actual AFR number in the scan data; good luck finding someone to give you the code disassembly for the particular PCM and OS you are working with so you could do that.

[Series8217]

Yeah I added it to the $DF code (OBD I....) which required moving in a whole missing subroutine from some Corvette code, but adding it to OBD II would blow, there's a LOT more code there. Then again, maybe there's some better-documented disassembly than what I had dealt with.