This may be more trouble than it's worth, but I'm just curious if anyone else has thought of this.

Instead of us MAF guys upgrading to SD, why not upgrade to a '94 or '95 LT1 computer? This PCM uses the majority of the same sensors as ours did. The three main areas that would cause problems (that I can think of) are:
1. Different MAF - easily solveable by buying one from a junkyard, or the aftermarket.
2. MAP sensor - This isn't any different than upgrading to SD anyway, personally I'd see if I could get a used SD plenum so I could have it mount on there and look factory.
3. Opti-spark - This is the one problem I'm not sure how to remedy. Does it output, use the same kind of data that our computer controlled distributors do? Can anyone think of a way to make them interface properly?

Overall, if it wasn't for the Opti issue I think it would be an easy swap. And if it could be done we'd have the added benefits of sequential fuel injection, plus the part throttle driveability of a MAF car (with the benefits of the newer 512 g/s type) and the WOT capabilities of a SD car. And I think there is much more flexibility when it comes to tuning the LT1 PCM too.

Anyway, this is just an idea I've been juggling around in my twisted little mind for a while. Thoughts anyone?

------------------
Black 88 GTA L98
261 RWHP, 345 RWTQ
13.406 @ 103.72 MPH
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back, Stock PROM
E.T.F.A Member #11

 

My first thought is sequential injection is not necessarily a benefit.

Actually I can't believe that someone hasn't mounted a project to build an entirely new ECM with a 16 bit cpu (or even 32 bit...386 chips are cheap these days). The hardware should be the easy part, the hard part would be converting the stock 8 bit microcode into 16 or 32 bit.

If you did it right you could put a flash chip in the ECM and have a programmer port so all you had to do was hook up your laptop and re-flash the chip with new code.

The vast majority of the aftermarket fuel injection systems (ECMs if you will) are SD. As a matter of fact I don't know if anyone is building a MAF ECM.

Anyone?

 

Sorry but that's already been looked at. The Optispark queers the whole deal. Also, takes out the SEFI when you take that out, unless you reengineer some sensors.

 

How does taking out the Opti take out the SFI? I know that the Opti uses an encoder wheel to get RPM and crank angle, is this the main setback? If so couldn't we just figure out a way to adapt the encoder wheel into out distributor maybe?

 

I suspect what Bruce is saying is that the machine code subroutine that controls the Opti spark also controls the SFI and is an integral part of the code. So it isn't a simple cut and remove change, and requires a thorough knowledge of Assembly Language Programming along with developing Source Code for the PCM. This is way beyond the average DIY'er - though I am now starting to get into Assembly Langauge Programming for the 7730 ecm.

 

There was an optispark eliminator from Electromotive. I think it uses a crank trigger wheel and some black boxes.

 

Their unit was on the market then off the market then on the market, I'm not sure if it's even available now, but was $$$.

Also, Bailey eng., makes a LS1 CNP ignition set up for the optispark, FWIW.

I quess I should have qualified the earlier statement with, you can do anything, just takes time and money. I still don't see any real practical affordable DIYer way of doing it.

While so many folks get tied up in this on the fly stuff, you never do enough note taking, and OTF just makes all the easier to miss what the engine is telling ya

 

Bruce, that's a good point about On The Fly. Frankly, a person should NOT be staring at their scan tool (brief glance is okay) while they are driving. And heaven forbid if they should want to make the change while they are driving.

I like to review all my data once I return to the comfort of my home and see all my data. Noting the time of certain "events" is useful for isolating things. I've done this a few times to find "quirks". But again, I did this once I returned home and reviewed all the data around the time the "event" occurred.

 

The on the fly tuning was not what I was after at all. I was just contemplating having the advantages of the more complex later programming of the LT1 computers. Plus, we could go the next step and put 4L60-E's in our cars and then be able to reprogram shift points and rear gear changes nice and easily.

 

If you really want to use a 4L60-E, GM sells a stand alone control unit for it(I think TCI has one also). It will work with both the 4L60-E and the 4L80-E.

Found some more information on it.
#12497316. 4L60E/4L80E Trans. Control Modular Assembly. $895.00 .....ummmm, kinda pricey.

[This message has been edited by 93ND500 (edited April 29, 2001).]

 

I have been thinking about this for about a month now, but with a different twist. Forget about the optispark stuff. The Vortec truck engine used a distributor with a cam sensor in it and a crank sensor in the front cover triggered by a wheel in front of the timing sprocket. These are the sensors needed for sequential. So I was going to put the sensors in the TPI engines with the new style front cover and crank sensor. Who knows about the rest of the conversion for an TPI Fbody?

 

When you start running large injectors it's a huge advantage. On my little 231 I'm running about 1.8 msec idle PWs, with 55#/hr injectors. Trying to get them to run at .9 msec would be a headache since they get erratic at 1.2.... Without hardly much effort guys are running 72s on the 231s.
(ie., 231 GN that is)

 

The optispark has a high and a low resolition part to it, the low resolution part tells which cylinder is next to fire. Unlike the old SEFI that might take 2 revolutions to synch the SEFI the optispark does it in 1/4 of a crank revolution.

It has 360 slots in it. It's an amazing little disc. Also, spaced out in it is 8 other slots corresponding to 1-8 of the other slots so that the ecm can count both at once to figure out the next cylinder to fire.

 

Hmmm, Blown85/TA do you know what year truck engines these sensors were used in? I'd like to try and get my hands on one and see if they're similar to the Opti. If they are maybe we could just substitute these in place of the Opti .......

Nevermind, thinking on the fly here. It's probably very complicated to make the spark advance interface with our old distributor too isn't it?

 

Scott Yeah they are in the 96 up Vortec until the new SB2 came out. I am looking for a crashed donor to rob every little thing out of so I can compare, no luck yet. I think the way to go is with this setup, but I am not sure if the timing cover will work. They made two different cam retainer's, so I need to check the front cover's for starter's. I would also like some input on the speedo problems that might be encountered? Then I think you use an older ECM(before OBDII) to run it. I know of one fuel injection place that already uses these for TPI swap to Sequential. So lets get some wheels turning and figure this out.

 

Why not just use the 96 and later vortec computor? It has the same capabilities as the LT1 ecm including the 4L60E trans.

Steve

 

Scott I believe it has something to do with the older(95-93) computer being more friendly to being programmed? Someone know the answer here?

 

OBD1 vs OBD2
Could this be the reason?

Steve