new ecm/sensors on old engine? possible?

so bored at work and thinking about car things. an idea pops into my head. so here's the hypothetical situation (based on complete ASSumptions):

lets say you have a factory ecm that is easy to tune, a lot of people are able to tune stock ls ecm's so i assume all of GM's ecms are easy to tune though (ASSuming), so lets stay you have a cobalt ecm,harness,sensors, and injectors. now lets say you also have an old carb'd 4 cylinder, lets say a air cooled vw 23xx cc engine.

could you take all your sensors and injectors from the cobalt and apply them to the vw engine then tune it enough to make it work smoothly?

you would probably need a custom trigger wheel of some kind for ignition, use the stock throttle body or drive by wire thottle body if thats what the cobalt uses, have the coolant temp sensor read oil temp and base your fueling accordingly, use the cobalt o2 and maf/iat and other sensors you can apply. then it would mostly be just getting your tune dialed in i would think.

would doing something like this be cheaper then piecing together your own sensors/injectors and making a wiring harness for a megasquirt setup? all of the cobalt parts could easily be scavenged at any junkyard for a reasonable price.

sorry if this is just rambling, my mind tends to wander when left to its own devices

A factory ECU would need to be VERY easy to tune, with access to a lot of different tables, if you wanted to do something that drastic. Going from a liquid cooled to an air cooled engine can require a lot of different calibrations.

MadScientistMatt wrote: A factory ECU would need to be VERY easy to tune, with access to a lot of different tables, if you wanted to do something that drastic. Going from a liquid cooled to an air cooled engine can require a lot of different calibrations.

this is where GM stuff wins. it's infinitely tunable. i have hptuners on my laptop and the amount of tunability in a modern gm ecu is insane.

MadScientistMatt wrote: A factory ECU would need to be VERY easy to tune, with access to a lot of different tables, if you wanted to do something that drastic. Going from a liquid cooled to an air cooled engine can require a lot of different calibrations.

i guess using a air cooled engine as an example was a bad idea haha thats just what was on the mind at the time. i was just trying see if any old 4/6/8 cylinder that only came with a carb factory could be used with a newer GM ecm and if it were a cheaper route then megasquirt

It can be done. Doubtful it'll be much, if any, cheaper than Megasquirt.

You could look into running an OBD1 Honda ECU and Crome/NepTune as well. Or a DSM ECU and DSMLink.

Sooooo, if I came up with a cheap LY7 V6 ,complete with wiring harness ,could I get it running in an older car by using whatever GM 6 cylinder ECM I can find at the pick-n-pull?

When you make it sound that easy, you're going to have a bad time.

Bear in mind you need to generate signals to the ECU that the ECU expects and understands.

There are aftermarket ECUs popping up (AEM Infinity for one) that can run pretty much anything you can throw at them. Figure $1300 - $2400 depending on cylinder count. I'm using one on my 2004 Honda K24 engine.

Some were trying to talk me into doing just that for a challenge car.

But I come from different angle on this issue than most.

As was said above, scaling sensors and getting digital tooth sensors working the right edges is an enormous part of getting it working.

Swank Force One wrote: When you make it sound that easy, you're going to have a bad time. Bear in mind you need to generate signals to the ECU that the ECU expects and understands.

if you have all the matching sensors that the ecu knows then it doesnt seem to hard. the hard part would just be getting those sensors integrated onto the non-gm engine

i went to my local junkyards website to get prices. an ecm is 35, harness is 35, injectors are 6 bucks a piece, throttle is 30, most other sensors are around 10. so lets say you get all this at the junkyard it only comes to (guess-timating around 8 of the $10 sensors)around $200. obviously you may get a bad sensor here or there that need replaced so call it $250 for all the hardware, but that doesnt account for what is needed to get it on the old engine, also need to add the cost of tuning, hp tuners is $500 new. that all together though is sub-$1000. how does that compare to the equivalent megasquirt setup?

The ignition is the hard part. I think $1000 would be pretty optimistic.

Hard to compare it to Megasquirt, two totally different beasts. Megasquirt is more flexible and will be easier without a doubt. Instead of having to conform to your ECU, your ECU can conform to your setup to a large degree.

So in terms of "equivalent," i don't know. But DIYAutotune sells assembled units for quite cheap, kits even cheaper.

There's not much that this won't run: http://www.diyautotune.com/catalog/megasquirtii-ems-system-smd-pcb357-assembled-ecu-p-171.html

And here's a harness to go with it. Leaves you a lot of wiggle room to work out the rest. http://www.diyautotune.com/catalog/1039-megasquirt-wiring-harness-ms1-ms2-ms3-ready-p-477.html

I will just leave this here as it seems relevant.

http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/diy-ecu-build-thread/79518/page1/

The trickiest part would be getting the right crank and cam reference signals. Older stuff, like late 80's early 90's is generally pretty stupid, and gets away with very few pulses per revolution. Newer stuff has many more teeth, with different spacing or missing teeth to give much more accurate representation of where the crank is at any given millisecond. And, the reluctor wheel is generally a permanent part of the crankshaft.

Air flow, temperature and all that other stuff is cake. They are just a number.

Can you change the firing order in hptuners? I dont see why it wouldn't work if the ecu sees all the sensors it needs correctly

You can't change the firing order IIRC - that is something that is "baked in" to the operating system (GM-speak for firmware).

However, GM PCM connectors are silly-easy to depin/repin so you can just change the firing order in hardware.

I had been planning on getting a 2.2 Cavalier PCM/wiring harness to bung onto my GTI. But then I realized, for all the effort of making a crankwheel that the GM computer would like (it's perfectly happy without a cam sensor, it will just not go into sequential injection mode) and the $200-300 it'd cost for the computer/harness AND the $100 for the HPTuners license (already have access to a GM unit) I could just say screw it, let's put a pair of Webers or Dell'Ortos on this puppy, it will sound a lot meaner and I like the old school vibe.

the T5 injection that Saab used on the GM900 and 9-3 was very tunable too

There's also a freeware ROM hack for certain Subaru computers. One of my rallycross friends has it on his WRX.

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