3.5 external crank question.

[ga2001532]

I have been thinking why can't you just tune let's say a grand ams pcm with a 3.4 to be able to run the 3.5 with out adding the external crank trigger. Is it just not possible.

[Jonpro03]

It's just not possible. The 3400 uses GMDIS. A 7x crank signal is sent to the ICM which outputs a 3x signal to the PCM. The 3400 also has another sensor in the balancer that has a higher resolution for finer idle control and I think it's used for SFI.

The 3500 uses a simplified Coil Near Plug ignition system in which the ECM directly controls the coils. To do this, the ECM gets a coded 24x signal from the crank position sensor and a 1x signal from the cam position sensor.

[ga2001532]

How does the 3.9 compare to the 3.5 for the sensors. Would you have to do the same with a 3.9 once you locked the vvt out.

[Jonpro03]

I don't know what kind of trigger the 3900 uses stock. Joseph Upson would be the man to answer that question. If you are using a 3400 computer to run a 3900, then you need an ECT and lock the phaser. If you are using the 3900 computer, well you won't have to change anything!

[ga2001532]

So is it just not possible to flash the 3.4 computer with the 3.9 file. Are the computers that different or is it more the wiring. I would use the 3.4 computer since I wouldn't want to wire in a 3.9 computer.

[bszopi]

PCMs are completely different, so no, you can't just flash a 3900 BIN into a 3400 PCM.

[Jonpro03]

AFAIK, you can't even mod a 3900 PCM yet. So even if you did swap it in, you wouldn't be able to tune it. That and I think the PCM has to have the BCM wired in with it. Not to mention it's got an electronic throttle so you'll be swapping that in.

That's why we have an external trigger.

[ga2001532]

Sounds good this is what I thought. my buddy really wants to swap the 3.9 in and I will do it also most likely once the mounts are made or figured out. I just wanted to make sure its basically the same as swapping a 3.5.

[CNCguy]

The LZ engines use a 60-2 trigger setup.

[pocket-rocket]

AFAIK, you can't even mod a 3900 PCM yet. So even if you did swap it in, you wouldn't be able to tune it. That and I think the PCM has to have the BCM wired in with it. Not to mention it's got an electronic throttle so you'll be swapping that in.

That's why we have an external trigger.

Ben has done some tuning on his dads G6 GT convertible with a 3900 with HP Tuners.

[Jonpro03]

I stand corrected!

[ga2001532]

So any of you guys know if it is possible to put the 3.9 in a grand am. I know you will need new engine mounts, a ect and lock the vvt out. What would I have to do about the alternator, water pump,powersteering and ac compressor. can I just swap those over from the 3.4?