Diz, you can run a distributor on an LS motor with the right timing cover. You can also buy or make, a Opti converted HEI distributor. SO you could run the LS whatever in an LT1 car using LS platform ECM, controllers and sensors, and additionally, run an LS dist timing cover and a Opti converted HEI distributor to keep the LT1 ECM in the loop. IDK how you'd interface timing retard for ASR, but that is not something that I would personally GAF about.



Actually, the Opti has two rows of resolution:
One tracks 360* of crank resolution with 720 inputs; 360 open and closed window positions, driven by the cam.
The other has 8 windows, so 8 points of reference per crank resolutions.

Each of the 8 slots is a different length, a length corresponds to each specific firing cylinder. The ECM counts how many 360 slots pass, during each of the different sized 8 slots, to determine which cylinder is where.


The LT1 is literally an angle based timing system, accurate to 1 degree. IDK how a 58x can be more precise than that. Doesn't make sense. Of course the LT1 1* of accuracy goes out the window with timing chain stretch, which we know that a crank based system is immune to.

I feel that philosophically, they're both way better than good enough triggers. The LT1 falters with slop between the crank and cam....and then of course, contamination of the housing, plug wires, cap and rotor, etc.


.

 

The difference is in the way the data is used, not measured. The high resolution wheel on the LT IS better than what is used on the LS, but the Gen 3 ECU handles the data completely differently.
The Gen 3 ECU doesn't need to be as accurate. The 24x reluctor wheel isn't just a 24 tooth wheel. The teeth are setup using different widths, spacing, etc to also provide cylinder data to the ECU, the same way the 8-window wheel on the LT does, and the camshaft tells the ECU which stroke each cylinder is on. Also, the wheel is a double stack wheel, meaning it technically has 48 alternating teeth, and has a dual track sensor to match.

The difference in ECUs is how they handle it. Sure, the 24x wheel technically only passes a tooth under the crank sensor every 15 degrees, but the ECU is fast enough to read the time between teeth down to one one-thousandth of a millisecond, which gives incredible timing accuracy.
The LT ECUs used 16-bit Motorola 6800 series processors that are 1-2 Mhz, depending on which ECU you have.
Gen 3 ECUs are 32-bit Motorola 68000 series processors 21 Mhz for the early ones, and 24 mhz for the later ones, with anywhere from 5-10x the flash memory.

You can adjust ignition dwell on a stock gen 3 PCM down to less than 0.01 milliseconds accuracy, with 0.1 (less in some places) degree accuracy on ignition timing.

 

what if you are running an lt4 extreme duty timing chain?

would that mean less slop? And a better system?



in a 1-2 yrs i have a major decision to make

whether to rebuild on with the lt1, putting it into a supercharged 383, etc

or take a plunge into the unknown with an alum ls3 , carbon fiber hood and take on c8’s, teslas and literbikes

both would be e85 setups

i am scared of option 2 because its gonna sit for longer as i try to figure it out, fabricate crap, etc

he11, i even do my own tuning on option 1.


but this ‘throwing away’ the asr /abs, gages and stuff to do an ls swap might stop me from doing that unless we can find a work around

 

Which of those will actually require the Optispark to function?
I'm sure a lot of those would work just if the ECU had power going to it as if the key had been turned on, without the engine running.
Would the Opti just be for RPM?

Edit: Where does the 92+ cluster get its Tach signal from, and is it on its own wire? I couldn't find a definitive answer.

 

I found this

92/93

https://www.chevytalk.org/fusionbb/s...hp?tid/199644/

 

Pinout for 92-93 ECM
https://www.lt1swap.com/1993_y_body_...schematics.htm

 

Looks like the 92-93 drives the tach from the coil using a filter/conditioner.
If you could figure out what kind of circuit the cluster is using, you could likely condition the LS ECM output signal, or possibly use the LT1 tach filter on the cylinder 1 coil for an LS engine to drive the tach (filter/coil signal is how my 2-step box works to get RPM signal from the cylinder 1 coil ground).

The 94-96 uses an ECM based tach signal.
For the 94-96, you could use the LS tach output to drive the tach on the dash.

Either of those would eliminate the need to use an Optispark with an LS engine.

 

No, it really doesn't.

If you're obstinate about doing the swap without getting rid of the OEM PCM (which is silly; Torqhead already shows you can use a '411 PCM on our cars with the right 'sauce'), just do as I suggested above and interpolate the low res and high res signals. You have the same trigger available on the LSx--so make a box that 'fakes' the optispark data. In your claimed scenario the stock PCM is only there to make things happy; it's not actually controlling the engine at all. The LSx PCM is doing that. So what's the downside to just faking the data?

The ABS does not require it, but because it's tied into the same system as the ASR, that causes a problem. ASR requires PCM connection in order to command timing retard. The rest of its inputs are external to the PCM and thus the opti; it uses the tach filter circuit to read engine speed independently.

The dash is driven by the CCM, which reads inputs from the stock PCM in order to calculate things like fuel economy and range, as well as get inputs for oil/coolant temp, etc. Because these items require PCM connection, the PCM must be happy, which requires the opti signal.

Orrrrrrrrrrrr requires a PCM that knows how to talk to the EBTCM (ABS/ASR) and CCM, such as the Torqhead solution.

 

Quote:

Originally Posted by JoeNova

He has an LT1 C4, so in reality, an Opti could be used to retain OEM functionality on the electronics, which is a very valid reason for wanting to use one.
I'd NEVER let it control the ignition.

Really???
Do you think he is serious when even in this very thread, post 5 he wrote..
. (Not to thread hijack, but has anyone (who has done ls swaps) swapped out the coils for an optispark

so they can use the tried and true easy to tune stock lt1 pcm with the ls motor?

/or worry about coilpack failure with the many new coilpacks added (from an ls swap)

also can add an msd box to the optispark where you cant to the coilpacks)

Or in the C7 section, he ask if anyone has removed their new engine and installed an opti-spark LT1-4 engine? https://www.corvetteforum.com/forums...e-lt1-4-a.html

Or, one of my favorites. Asking about C8's being only automatics.... and HE can shift faster then an automatic!! https://www.corvetteforum.com/forums...than-that.html
All at the same time claiming he has 510rwhp and 500tq, but runs in the 12's at 120mph!!!

Yeah, I dont take him serious, and all its doing is causing fights between members....

 

aFter years of being helpful, you are taking some blows at me for some reason

you arent gonna make friends here by bullying me

i have had responses liked 230 times.

those same newer cars i suspect you bow down and accept defeat, i look to defeat with my c4.

It seems like i sometimes am the only person that wants to see a c4 to WIN against these newer cars

sure, im a crappy dragstrip driver. They are all crowded, i go there for 5 hrs and get 1-2 runs in. I dont drive like an a$Z on the street so its tough to practice there.

i recently discovered my tune was incredibly lean in the 1000-2500 rpm range - making it incredibly easy to bog at launch which is what usually happens with my lousy 2.3-2.4 60 ft times

ive posted dyno charts (on my old p600b blower, on a well known pcmforless dyno). It showed 509 rwhp and torque at 5600 rpm and CLIMBING. The next customer was there and i wasnt able to do another pass and rev higher. I dont see wasting $300 to do another pass just for bragging rights. Why people dog me for this, i have no idea. Dumb would be runnjng an unproven combo/tune to 7000 rpm on the first pull. I started off with dyno runs to 4500, 5000, and then 5600 rpm - meticulously checking my wideband and logs for knock retard, i cant be faulted for quitting at 5600 rpm bc i was cautious /ran out of time

ive brought up a valid concern about losing ASR functionality with ANY kind of ls / lsx pcm swap without an optispark

I share some passion i do for the c4 platform - dont dog me for caring and wanting to make this platform still viable against tesla/literbikes/ and c6/7/8’s

 

I don't think he was "******* you" or bullying you. He stated some facts. He backed 'em up with some links. He makes some good points. If you don't like his points....maybe you should "adjust" your thread topics, some?

 

Look at the purpose built cars like the '87 CB Ramey won the optima street car challeng with. That guy had a goal and built his car to achieve it.

If you're goal is to have that level of performance and retain stock interior and functionality then plan to spend as much as he did, plus some.

I personally think you should go for the ls swap, race dash, and aftermarket abs controller or piggyback

 

92 and 93 kits aren't available because in those years the fuel injection is "batch" fired while later years are "sequential."
My understanding is that it wasn't cost effective to make kits for 92 and 93.