Stupid ECM idea
 

This may be a knucklehead thought, but I’ve seen the threads on problems tuning (some?) LT1s, and I’ve seen where some guys have LT1 intakes modded to bolt to SBC with an HEI. So maybe you guys with more experience than I at this (esp Mr HPT guy) could tell me if this is a stupid idea.

Could you adapt an LS1 ECM to any of these applications and tune it with the HPT (or similar) software? Or is there some crazy technical hurdle, like maybe the reluctor ring?

Just a lunchtime thought…

Edit: Yes, I know the harness issue would be a PITA.

LS1's use a crankshaft position sensor and a camshaft position sensor to control the timing, LT1's have a distributor.

Dude you can use the same computer stystem i'm using for my 3.4...Its called Megasquirt and you can tune it to what ever spec you want for any engine.

the harness shoudl be simple in theory. GM uses generic sensors and conectors, so all you would have to do is move a few wires around and you would be set. to wire in crank posisiton you can use an inexpessive flying magnet style pick up, similar to what MSD sells for use with their digital systems.
cam position would be a tough call because of location. on an older SBC it wouldn't be too tough since most of the flying magnet systems and fairly slim. on an LTx engine you have far less clearance even if you remove the opti.
i don't see how it would be necessary to use both cam and crank, since ignition lead is based on the timing of the piston before TDC and that is crank position related.

knucklehead!

Just kidding skippy! It just not simple. The LT1 / Opti is easy enougn to program out the signal that a conventional distributor can be used. But when they do that they still retain the opti for the cam signal.

The opti has two functions: The optical part is the cam position sensor (the low Res side) which tells the ECM which individual injector to fire ( except 93s that are batch fire - another issue ) and the other function is the spark distribution (High RES). The high Res is the root of the evil of the opti. How long does a conventonal cap and rotor last? Well that is how long a Opti cap and rotor is going to last! Could be 20,000 miles, could last 200,000 miles.

If you replace the distributor part of of the opti with a conventional distributor or remore/direct spark coil pack then the opti will most likely last allot longer. The sparking within the unit results in some heat (and later condences) and Ozone that eventually can corrode the optical portion. This is why later models are vented, it's a bandaid, not a cureall. The cure was to eliminate the opti completely.

To swap a LS1 ECM into a LT1 car would require some way to convert the cam signal such as how the Deltech or Electromotive system does. It is a bit more involved then just the harnness and ECM. The LS1 ECM will require data as to which cyclinder to spark.

As far as the tuning, both are basically the same other then the software used. The problem with LT1 tuning is that there are less people that do good work locally so they use mail order which is far less quality then having someone like Bill working real time on a LS1 car.

LS1/LT1 tuning isn't really a problem with the EMC. The big advantage of the LS1 ECM is that it can handle high RPMs. An LT1 computer simply locks up before 8,000RPMs. But if you've invested the money to spin that high your going to go with a Motech, Gen7 other other type unit that has far more flexabilty. Plus that high an RPM will kill an opti, there seems to be allot of folks that have had them self destruct when pushed near 7,000RPMs. Couple we found had a drive pin too long, but I think the stockers just weren't designed to handle much over 6,500.

here is what's on the inside of an Opti:

http://www.charm.net/~mchaney/optisprk/optisprk.htm


My solution was to use an aftermarket ECM, Coil packs, Crank pistion sensor, and a conventional type mount distributor that is just a sensor for cam postion. This will completely eliminate the opti. I purchased everything, just never got around to installing it and found the stock ECM can actually handle what i need ( for now! )
JB

Megasquirt is MUCH easier

How many times are you planning on posting that in the same thread?

- Justin

looks like as many times as someone else mentions something different :lol:

or untill he relises its more flexible than a stock ecm could ever be

megasquirt = overpriced adn under performing. it has fewer parameters and is a lower resolution system than the factory GM computers. the only reason it is so much easier to use is because it can't do as much.

the system i ordered contols everything AFR spark timing you name it its MS1 Vs3.0. you must be talking about version 1 or 2.2

there is a ton of info on thirdgen.org regarding ecm swaps, in particular, running the vortec engines with an LS1 ecm. The LT1 engine uses the same type of crankshaft position sensor, so if you were to rework the intake to use a vortec distributor or retrofit a regular dist for a cam position sensor, its somewhat straight forward. look for a thread entitled 'obdii tpi' or something like that. The LS1 pcm (I guess; its part number '411, the right pcm) was used in express chevy vans with the old style vortec SBC.

there are tons of options out there....it really depends on your skill level and how hard you want to make something different.

personally, I think its a crock what these software places charge for OBDii tuning software with 'credits' and 'vin locks' and all the other bullcrap so I would still use OBDi where possible and any freeware or 'reasonably priced' software.....