GM 3800 Series 2

[forum8715]

I am trying to set up a megasquirt on a 3800 S2 out of a 2000 Camaro on a run stand.

I am trying to see if anyone has set up this system already, or what I need to get it running with the stand alone

Thanks

[Matt Cramer]

You'll need the DIS module from an OBD-I version of this engine unless you want to get fancy. It uses different pick-ups from the GM DIS in this article, but it wires up to the MS-II in the same way.

[forum8715]

Thanks for the reply.

I now am wondering if the original CKP can be used since it is a hall effect or do I need to change to a VR for an AC signal.

And are there any other sensor inputs that need to be modified or changed?

Thanks

[Matt Cramer]

You don't need to change the sensors, just use the OBD-I DIS module. The 3.8 used a different kind of DIS module but the same module-to-ECU signals.

[3800se]

Here are a few pictures from a 3800 Series II reluctor and CKP. (One of the reluctor teeth bent out in shipping and sheared off the CKP.)





It appears to be a dual sensor setup. (4 wire, dual reluctors)

There appears to be 18 equally spaced teeth (20 degrees apart) on the outer ring, and three not equally spaced teeth on the inside ring. I'll get some real measurements ASAP.

[3800se]

I measured the teeth on the harmonic balancer and this is what I found:

Crank.GIF

The three inner teeth are offset 5 degrees, which I believe is used to trigger TDC.

[3800se]

I partially hooked up MegaSquirt to my 3800 Series II today. I tapped into the purple/white wire (3X TACH) going to the Ignition Control Module (ICM).

Here's a video:

http://filebox.vt.edu/users/sparkman/run6.avi (2.3 meg, Microsoft MPEG4 V3)

Here are two waveform captures; one of the purple/white wire and one of the simulated MegaSquirt injector pulses. The car was at idle, ~750 to 800 rpm.

3X Tach


Injectors


At the moment this is enough to get MegaSquirt controlling my injectors. The PCM will control spark until I can get MS to read the knock sensors.

[fury fan]

Hey 3800se:
This is a little off-topic but wanted to see if you had checked to see if that engine was one of the ones with the 'vulnerable' intake manifold and gaskets (relates to the Dexcool class-action lawsuit). I was thinking all the 3.8s from around 1995-2003 were affected but I don't know if a RWD Camaro has maybe a different intake manifold?

[3800se]

The lower intake manifold gaskets should be the same on the 3800 Series II regardless of which car it goes into. I've replaced the manifold gaskets at least twice now during head, cam and supercharger swaps. Replacing the gaskets takes from 3-5 hours depending on your skill level. I can do it in under an hour

[fury fan]

I presume you also know about the EGR port that runs into the upper plenum? They are known to corrode in that area and cause another leak entry point.

When my 98 Monte did it recently it had a bad lower gasket but also the upper problem. My buddy, who repaired the car, replaced the lower gasket but didn't follow my advice about the upper intake, so he got the joy of going back in to repair it completely.

Not wanting to sound like a know-it-all, just wanted to pass along what I learned.

[3800se]

I in fact had a leak in the EGR tube last year. Here's a picture:



The leak sounded like a loose rocker arm or bad pushrod. It took me a few days to figure out the source.

Bronze braze took care of that issue.

[LNorton]

You don't need to change the sensors, just use the OBD-I DIS module. The 3.8 used a different kind of DIS module but the same module-to-ECU signals.

What year and model can I find a ODB-I module? I would like to look into this a little further. I have seen some promise, and would like to do this with my race car this winter.

[Matt Cramer]

'95 and earlier models with the 3.8 and no distributor. I'm not sure what year they started, although it seems the earliest one was on the Buick Grand National.

[LNorton]

Why is it that we have to use an ODB-I unit and not an ODB-II? From what I can tell they take the same inputs and output the same signals to the PCM.

[Matt Cramer]

Did the 3800 keep a separate external module when they went OBD-II? If they did and the signals are the same, it shouldn't be a problem. I may have been thinking of the 3400 (which went to an internal module) when I wrote that...