3900 versions and configurations for swap use

[Will'sFiero]

That may be an option...
EFI Connection ( www.eficonnection.com ) sells 24x wheels... There are probably other sources in the aftermarket as well. If I can buy the part cheaply, I don't see a need to make it.

Also, the 24x wheel is really two wheels that are the "inverse" of each other (one wheel's high is the other's low) put together.

with this being said, I would say you need the LS4 trigger wheel.

I don't know if the LS4, LNJ and LZ8 use the same diameter journal where the wheel installs to the crank.

[ericjon262]

That may be an option...
EFI Connection ( www.eficonnection.com ) sells 24x wheels... There are probably other sources in the aftermarket as well. If I can buy the part cheaply, I don't see a need to make it.

Also, the 24x wheel is really two wheels that are the "inverse" of each other (one wheel's high is the other's low) put together.



I don't know if the LS4, LNJ and LZ8 use the same diameter journal where the wheel installs to the crank.

assuming all of the 24x wheels are the exact same... hence why I said use the LS4 wheel if you plan to change the cylinder count in the LS4 programming. that way the computer is getting what it expects.

[Will'sFiero]

assuming all of the 24x wheels are the exact same... hence why I said use the LS4 wheel if you plan to change the cylinder count in the LS4 programming. that why the computer is getting what it expects.

Just don't know if the wheels are the same diameter. The LS crankcase can hold a 4" stroke, so that wheel is big enough to make it around those throws and trigger a sensor in the wall of the crankcase. The V6 wheel may not be that large.

Also, it occurs to me that the E40 may have a "crank trigger resolution" flag like the V6 PCM's you've been investigating... It won't be necessary to swap the wheels if the E40 can understand the 58x trigger already in the 3900 and still do DBW, DOD/AFM and cruise control.

EDIT: The E40 will need some info from the G6 GTP manual transmission calibration (or a different manual trans LS calibration?) in order to run the engine with a manual transmission. It may need a clutch anticipate switch like I had to install in The Mule for the Shelby computer.

[ericjon262]

Just don't know if the wheels are the same diameter. The LS crankcase can hold a 4" stroke, so that wheel is big enough to make it around those throws and trigger a sensor in the wall of the crankcase. The V6 wheel may not be that large.

Also, it occurs to me that the E40 may have a "crank trigger resolution" flag like the V6 PCM's you've been investigating... It won't be necessary to swap the wheels if the E40 can understand the 58x trigger already in the 3900 and still do DBW, DOD/AFM and cruise control.

EDIT: The E40 will need some info from the G6 GTP manual transmission calibration (or a different manual trans LS calibration?) in order to run the engine with a manual transmission. It may need a clutch anticipate switch like I had to install in The Mule for the Shelby computer.

IIRC, the newer PCMs use a clutch position sensor instead of a switch, but I could be wrong.

[farmerz24]

It would be nice to add 90 RWHP, 1.1 liters and pop gas mileage over 30 mpg with a $600 engine (although my 2.8 already gives 28 mpg at 80ish mph).

I wish I could get that mileage in my 3900 swapped Subaru legacy

[caffeine]

The bigger the injectors the harder it is to tune for great fuel economy

[niceguy]

I wish I could get that mileage in my 3900 swapped Subaru legacy

What are you averaging currently? I've gotten up to 26-27 in my Uplander Cargo 3.9 stock on consistently flat highway in the summer which is pretty good for a 3.9 with a 4spd auto in a 4400lb carcass. However, 24-25hwy was about average. Of course since the engine and tranny PCM tunes, I'm only getting about 22-23 highway...the tranny just loves to downshift now, a little too much in fact.

[farmerz24]

I'm running stock 3900 injectors.
Getting 200miles to 55 liters at around 0F.
2500 rpm cruise
About 10-12 cold start ups per tank, but it will run 14.7-15.5 afr when cold.
I've tried cruise timing from 30-45 degrees with no change. I was told run the cam fully advanced for fuel economy. But seemed to not help. Also tried running at about 30 degrees retarded from fully advanced. Going to try running the cam fully retarded during cruise and see what they does. Cam makes lots of tq down low when fully advanced.

[Will'sFiero]

I'm running stock 3900 injectors.
Getting 200miles to 55 liters at around 0F.
2500 rpm cruise
About 10-12 cold start ups per tank, but it will run 14.7-15.5 afr when cold.
I've tried cruise timing from 30-45 degrees with no change. I was told run the cam fully advanced for fuel economy. But seemed to not help. Also tried running at about 30 degrees retarded from fully advanced. Going to try running the cam fully retarded during cruise and see what they does. Cam makes lots of tq down low when fully advanced.

What RPM are you turning at what speed? I'm guessing that the Legacy is gearing pretty short because it was originally a 4 cylinder car.

Lightly loaded at 3000 RPM will get much worse mileage than more heavily loaded at 2000 RPM, as long as the heavy load scenario doesn't get into power enrichment (PE) mode.

That's how C7 Corvettes can get damn near 40 MPG in real world driving.

[caffeine]

Agreed the gearing is probably killing MPGs

Sent from my Nexus 5 using Tapatalk

[farmerz24]

2500 at 60 mph.
Another guy did a 80's Buick 3.8 into an automatic legacy and can get 600 Kmh per tank. Same 2500 at 60 mph. I'm struggling to get 400 per tank

[robertisaar]

Mars is running a 3 speed and I think a pretty high ratio, and he's still knocking down decent MPG numbers, even with an ~11 second f-body(memory, FWIW).

[Will'sFiero]

2500 at 60 mph.
Another guy did a 80's Buick 3.8 into an automatic legacy and can get 600 Kmh per tank. Same 2500 at 60 mph. I'm struggling to get 400 per tank

For reference, cars with the 282 five speed turn ~2000 RPM at 55.

How big is the tank?

Getting 200miles to 55 liters at around 0F.
2500 rpm cruise

Is 55 liters your whole tank?

Do you think the "other guy" is A) Truthful and B) sufficiently concerned with details to *ACCURATELY* measure fuel consumption?

[Will'sFiero]

Dam, has it been 2015 since I posted in this thread?

Does anyone have a corresponding photo of a 3900 or LZ4 3500 block?



This is the 2.hate from a 1988 Fiero. The '88 Fiero uses a different mount bracket than the '84-'87 cars. I've read that the '84-'87 bracket bolts up to the 3900. The '88's is more like a saddle. It uses the same bolts on the rear/right side of the block as the '84-'87 bracket, but also uses some bolts on the front/left side of the block. Are those bolt holes still present on a 3900?

[Guest]

That area of the 3900 is very different, in fact starting with the 3100 and up it's different. However the one bolt that is used there is in the same location on the 3100 and 3400. The 3500 and newer do not have those lower holes in the block above the pan rail. Also the bolt through the front of the block is in a different location on the 3500 and newer.