LT1/0411 PCM/Opti Delete

[sandrock]

Well, they say that the simplest approach is sometimes the best.

Major brainstorm. The Vortec 454 uses a 24x reluctor on the crank snout, just like the Vortec 350 and its 4x reluctor. Same firing order too. There are only two issues...the first issue is the keyway on the 24x reluctor is off slightly from the 4x, and the second issue is the 454 crank is thicker. So the 24x won't fit as it is...

...unless you attach it to the crank timing cog.

So, lets machine a shaft with two thicknesses, one for the 350 crank, and one for the 454 crank, and use that as a fitment tool to ensure concentricity. Then we fit both the timing cog (350) and the reluctor (454) on that. After finding where the 24x wheel should be in relation to where the 4x wheel would have been, we drill 6 holes through both, tap the timing cog and countersink the reluctor wheel, and attach with screws.

Thoughts????

[EagleMark]

Well yeah if the reluctor is available through GM it's still got to be cheaper than making one. Tapping it to timing chain crank gear would be another easy cheap way. But have to make sure it clears chain and ends up it right position for crank sensor.

Looking at an Optispark distributor I have here apart the cam sensor can go right where the opti sensor is mounted up or down after a cam reluctor was made. Cam relutor could be mounted by tapping hole in existing hub. Would not necessarily have to have a distributor cap or blank cap made, would it? cam sensor can be open? Dave w and MSD use open/exposed sensors. It would use existing opti distributor just like the EFI connection piece. Although theirs is enclosed, cleaner looking aftermarket piece.

[sandrock]

Well yeah if the reluctor is available through GM it's still got to be cheaper than making one. Tapping it to timing chain crank gear would be another easy cheap way. But have to make sure it clears chain and ends up it right position for crank sensor

Hence making the alignment tool. The only part to figure out would be where to clock it. On the Vortec 454, the cam sensor looks like it is mounted on the very bottom, say the 6 o'clock position, where the LT1 has it at 7:30 or 8, so the clocking will have to change as well.

Looking at an Optispark distributor I have here apart the cam sensor can go right where the opti sensor is mounted up or down after a cam reluctor was made. Cam relutor could be mounted by tapping hole in existing hub. Would not necessarily have to have a distributor cap or blank cap made, would it? cam sensor can be open? Dave w and MSD use open/exposed sensors. It would use existing opti distributor just like the EFI connection piece. Although theirs is enclosed, cleaner looking aftermarket piece.

It needs to be covered, not due to the sensor, but due to the reluctor. Should something get in its way while it's running, it won't be pretty. Likewise should the reluctor come loose, something is there to contain it. At the very least an Opti cap could go on it.

Both the sensor and the reluctor can be had through GMPD for less than 100 bucks. Not sure if the sensor will fit the LT1 cover...might very well have to buy that from EFI Connection. Even then, that's still less than 150 bucks spent for that portion, instead of spending 270 JUST for their reluctor. Consider the cam sensor build, and this can conceivably be done for less than 300 bucks, minus the coils and PCM tuning.

[EagleMark]

I don't know what you guys are using for crank sensor or cam sensor but here's one that will do both.
http://www.diyautotune.com/catalog/h...sor-p-479.html

And a threaded version:
http://www.diyautotune.com/catalog/h...sor-p-489.html

[EagleMark]

Here's a picture of Opti sensor and trigger wheel. Wheel is very thin.

[dave w]

I found these pictures on the net. Seems someone has figured out an interface to use an '0411 PCM using the LT1 sensor. http://www.weswoodperformance.com/vi...II_411_PCM.wmv


dave w

[jameslleary]

just my $0.02, but i think Ford was on the ball with their EEC-4 dizzy....sequential injection, without a freakin crank sensor.

[EagleMark]

The 94 and 95 LT1 was sequential without a crank sensor because of the optispark ignition system.

[jameslleary]

yeah, but thats only for use on the LT1....Ford did it with a standard distributor. Us GM guys have to hack something together. I have often thought of doing something similar to the picture 2 posts up, and running a late LT1 ECM just so i could run sequential injection, with my TPI hardware.

[EagleMark]

1project2many just posted about sequential versus batch fire in another thread. It made me remember a conversation with a Detroit Fuel Injection engeneer who has been working on developing EFI from it's inception for GM then Ford. SFI was developed to meet EPA standards for idle and off idle. The way he described it was once an engine reaches like 1200 RPM it does not matter, injectors are firing so fast it does not make a hill of beans. More RPM and they hardly flinch at turning off, high RPM and they are just about wide open constantly. So why is SFI such a big deal?

Look at the 94-95 LT1, in 1994 it was already set to pass EPA standards for OBDII in 1997. Why they added a crank sensor in 1996? I don't know but it must have been to meet an EPA regulation because it was already sequential and met EPA emmisions without it?

[jameslleary]

I was under the impression that i would get a smoother idle and better mileage with SFI...doesnt hurt to be a little cleaner while at it too.

[gregs78cam]

The Crank sensor was probably added to augment the OBDII requirements for malfunction detection. Maybe? Well, along with establishing engine rpm without a distributor.

[EagleMark]

I was under the impression that i would get a smoother idle and better mileage with SFI...doesnt hurt to be a little cleaner while at it too.

Cleaner air is always a good thing. Who knows how far behind EFI would be if it were not forced upon vehicle manufactures to clean up emissions. SFI is a better system, but is it worth the time, effort and money to have one on an engine that never came with it? If it did get better fuel mileage would it ever return the investment?

I'm not sure idle would get smoother just because it is Sequential but here is an example of how you could tune idle. This is a stock 1995 Impala SS. The Caprice is the same, the 9C1 Cop car is the same but the same engine in a Cadillac is different? I have run them all on my Buick LT1 and can't tell the difference and data shows no difference. So why is there a difference?

I've been told the way this was tuned for cleaner emissions was by exhaust temperatures. That is why each cylinder is different, at idle there is not as much water flow and certain cylinders would get hotter. After Idle and Off Idle all cylinders run same amount of fuel. Back to why vehicle manufactures had to develop SFI was to clean up idle emissions.

[sandrock]

Been a while since I posted back to anything....life has a funny way of getting in the way of things...

Anyways, nobody local to me will touch the intake manifold as far as modding it for a distributor. The local parts maching shops will not make some prototype tonewheels for me either, as they cannot make anything for any automotive application. Sooo....back to the thinktank for me.

As far as the LT1 build is going....just found out that the engine Hawks 3rd Gen sent me ISN'T aluminum headed. They swear up and down it came from a Trans Am, and maybe it did, but that TA probably didn't come from the factory that way. But since I have it, I might as well use it. Found some 'vette centerbolt valve covers for 10 bucks on CL, so I bought those, stripped, etched, and painted them in wrinkle black. Turned out shweeeet!

[pather]

[QUOTE=dave w;2469]I found these pictures on the net. Seems someone has figured out an interface to use an '0411 PCM using the LT1 sensor. http://www.weswoodperformance.com/vi...II_411_PCM.wmv

I've a 94 LT1 and new to this forum, and was wondering if the interface for getting a signal to the 411 PCM was ever achieved from an LT1 Opti and trigger? This is my 1st LT1 and I'm pretty happy with its performance but have read a lot about (and have done) the Opti replacement before finding out about the 411 PCM upgrade.

Am pretty green to this, but from the research I've done, the EFI Connection 24X conversion is the way to go, but the price of their kit is the major stumbling block, so I found my way onto this site in my search for for innovative DIY (less $) success stories as to what others have (or can be) done without spending a lot of hard earned $.

If I understand things correctly, the biggest issue is getting a crank and cam signal from the Lt1 setup to the 411 PCM, and the Opti sensor signal cannot give the proper signal, at least not without some interface, etc. Is this correct?

Does the Opti sensor and trigger wheel give crank and cam positioning signals, but the signal is just not compatible for an LS 411 PCM?

Given the last post on this thread was 4 years ago, does anyone know if the DIY solution was ever achieved? The rest of the conversion parts (outside of the 96-97 timing cover) seems to be readily available at decent salvage prices, and once the signal issue is addressed, the harness can also be converted relatively cheaply if you're open to take the time to change connectors, and even go as far as changing the PCM connectors on a LT1 harness (from LT1 to LS connectors), and adding the few new sensor connectors etc.

Any updates or feedback would be greatly appreciated.