Secondary relay module questions

[-=Jeff=-]

Originally Posted by 8upZR1

I guess I can bring myself to understand your point, however, when I think of the LT5 ECM the only thing in my brain is this:
The LT5 came out in 90, ergo the ECM was engineered in probably '84 maybe '85. In 84/85 I was playing Comodor 64, or 8 bit Nintendo. Now its 2008 and I have out grown a comodor 64, and 8 bit Nintendo, and LT5 ECM.

I remember reading somewhere in the registry on a tech page that the early ECM can only resolve RPMs in 250 rpm increments. Like 0-250-500-750-1000. The newer LT5's supposedly read 20 RPM increments. Thats quite an improvement over 250, but is complete shite compared to the resolution of a F.A.S.T. ACCEL, BIG STUFF, MOTEC, etc. The engineers at GM really aren't to blame as they were working with shite to begin with. Even if its original, you cannot possibly argue that LT5 ECM holds a candle to modern EFI controls with modern microprocessors. Why defile your LT5 engine with the original ECM? It barely works, it breaks all the time, parts are impossible to find, it needs all sorts of $$$ ancillary equipment (IGN module), and is totally outdated. Take your LT5 ECM and put it in the box next to your Nintendo. Maybe in 30 years you can whip em out and let the greatgrandchildren learn about how hard we had it in our youth.

If you EBAY your ECM, PROM, IGN module, spare IGN module #1, spare IGN module #2, plug wires, coils, mount, wiring harness, secondary relays, etc. you will have plenty of cash for a F.A.S.T. + money left over to buy drugs. It makes sense to me at least.

While I agree, the one of things keeping me from switching to a F.A.S.T.

Getting it to work with and Satisfy the CCM from complaining when it loses communication with the ECM.

Also which F.A.S.T system would run 16 injectors?

[XfireZ51]

Originally Posted by 8upZR1

I guess I can bring myself to understand your point, however, when I think of the LT5 ECM the only thing in my brain is this:
The LT5 came out in 90, ergo the ECM was engineered in probably '84 maybe '85. In 84/85 I was playing Comodor 64, or 8 bit Nintendo. Now its 2008 and I have out grown a comodor 64, and 8 bit Nintendo, and LT5 ECM.

I remember reading somewhere in the registry on a tech page that the early ECM can only resolve RPMs in 250 rpm increments. Like 0-250-500-750-1000. The newer LT5's supposedly read 20 RPM increments. Thats quite an improvement over 250, but is complete shite compared to the resolution of a F.A.S.T. ACCEL, BIG STUFF, MOTEC, etc. The engineers at GM really aren't to blame as they were working with shite to begin with. Even if its original, you cannot possibly argue that LT5 ECM holds a candle to modern EFI controls with modern microprocessors. Why defile your LT5 engine with the original ECM? It barely works, it breaks all the time, parts are impossible to find, it needs all sorts of $$$ ancillary equipment (IGN module), and is totally outdated. Take your LT5 ECM and put it in the box next to your Nintendo. Maybe in 30 years you can whip em out and let the greatgrandchildren learn about how hard we had it in our youth.

If you EBAY your ECM, PROM, IGN module, spare IGN module #1, spare IGN module #2, plug wires, coils, mount, wiring harness, secondary relays, etc. you will have plenty of cash for a F.A.S.T. + money left over to buy drugs. It makes sense to me at least.

Actually, the resolution on the LT-5 code is in 100rpm increments. Not sure where you read that its 250. Early C3 ECM like the 7747 had resolution in 400rpm increments. The higher rpm ranges, ie over 2000 rpm, go to 200rpm and then 400 up to 7000rpm. That's for the VE and SA tables. In most cases the aftermarket stuff resolution is considerably less granular than the OEM. That's because the AM stuff doesnt't deal with the same constraints the OEM needs to. In addition, there's much more
logic in the OEM cal dealing closed loop controls. Aftermarket stuff is usually more expensive but more rudimentary in its logic. As old as the
LT-5 stuff is, its still pretty good. Its not as much a question of the processor speed but more importantly the software running the motor.

[Pete]

I don't have tuning issues.
I just want to have a choice to either pay the big $$ for parts that are no longer available or for parts that i can buy from Jeg's or local parts store.

Pete

[8upZR1]

I thought I read the 250 on the registry site, however if you say its 200 or 100 thats probably right. I don't really know 100%, but I do know that 100 rpm still SUCKS. Even an SDS EM4 can resolve down to 2 rpms. When people swap to stand alone they always gain power and consistency. When you dyno a motor with OEM EFI there is always an issue with repeatability. I have seen motors vary by as much as 15HP from pull to pull just from the stock ECM's inconsistency. You will never get a proper engine calibration if your spark and fuel vary +/- 3%. Just wont happen. With a F.A.S.T. or Electromotive box you can rest easy at night knowing that your spark will occur at the correct moment every time. Also the newer boxes, like XFI, have closed loop operation for both WOT and light load. With a wide band & XFI you can just program a target A/F and the box will do the rest. It doesn't get much better than that. Many of the newer EFI systems can even run the 8 additional injectors. I think its the BIG STUFF that can handle up to 3 sets of 8. Also there are tons of companies that make controllers for additional injectors. The best ones I've used are from Japan: Greddy, Apexi, & HKS all make really killer stand alone injector controllers. Greddy even has a simulator module add on that makes setup an tuning easy.

As for the complexity of the code, I can state from experience that microprocessors run a lot better with short, simple, efficient coding. When I was a grad student I took CFD courses with a bunch of Indian and Chinese guys. Late at night I would steal their source code to see how they ran their various schemes. The shorter codes gave the same reslts as the longer ones, just a lot faster. This probably doesn't mean much for the LT5 ECM but when the # of calculations reachs into the millions then speed becomes directly related to the number of lines in the code. The constraints that GM engineers had to work with in the 80's are insignificant today.

I think that NCCCCRS guys should be the only people running the OEM ECM. Think about how far computers have come in the last 20 years. When you buy an LT5 ECM or Ignition module you are shelling out mega $$$ for technology that is just old. I dont see the point. I always want my motors to run as good as is humanly possible, and LT5 controls just dont do it. I love the automotive aftermarket and the products that it produces. More aftermarket support for the ZR1 would be the most wonderful thing in the world. But since that wont happen the only solution is to adapt stuff built for newer cars. For the $$$ I spent on LT5 stuff I could have had a F.A.S.T. + twin turbos + a spare SBC. Instead I have electronics from 1985. It just doesn't make sense to me.

[XfireZ51]

Originally Posted by Pete

I don't have tuning issues.
I just want to have a choice to either pay the big $$ for parts that are no longer available or for parts that i can buy from Jeg's or local parts store.

Pete

Pete,

The LSx stuff would give you the extra 10-15hp you're looking for.

8up,

"I thought I read the 250 on the registry site, however if you say its 200 or 100 thats probably right. I don't really know 100%, but I do know that 100 rpm still SUCKS. Even an SDS EM4 can resolve down to 2 rpms. When people swap to stand alone they always gain power and consistency. When you dyno a motor with OEM EFI there is always an issue with repeatability. I have seen motors vary by as much as 15HP from pull to pull just from the stock ECM's inconsistency."

I don't even know how you would tune using a resolution of 2 rpm. The VE and SA tables for that would be HUGE! I'd sure like to see it. When I put my car on the dyno recently, hp varied no more than 1-3hp between pulls. Completely acceptable variance when considering heat soak etc.
What was it about the stock ECM that was inconsistent?

[Pete]

Originally Posted by XfireZ51

Pete,

The LSx stuff would give you the extra 10-15hp you're looking for.

Now your talking my language HP.

If i can make .500 lift cams work in a LT5 i can figure out some ignition stuff. Operation Winter HorsePower.

So maybe 485rwhp from a stock 350ci
Pete

[8upZR1]

The inconsistent pulls were all done back to back without cooling time. This probably had something to do with it cause we all thought too much timing was being pulled, even with desensitized Haibek chip. 3% HP variation on a 500 HP motor = 15 HP. You might be able to finagle more consistent dyno pulls but that isnt what you would get if you were running a Mustang Cobra from stop light to stop light. You may be faster on the 1st light, dead even on the second, but by the 3rd you are toast.

I know that isn't very scientific, but I don't believe in test #s generated in closed environment. If your car runs 9's in the 1/4 @ the track with no air filter, ICEE in the intercooler reservoir, cold intake, no interior, bumped timing, etc then it isn't a real 9 second street car. On the street with interior, full tire pressure, your girl friend and her fat a$$ friend, D2O w/o ice in reservoir, normal timing, that 9 sec car is a low 11, high 10 player. If you sub a b*tch*ng wife for that G-friend then itll only go 12's. What do you call a 9 sec car that runs 11's in street trim? SLOW, POS, that gets eaten by a bonafide 10 sec Honda. (yes, they are rare, but they do exist) + Honda guys have small asian girls that dont add a lot of excess weight. Something to think about.

In Miami @ a place called T-Bone's I witnessed a 1999 Porsche GTS put down amazingly consistent dyno pulls. Like 677, 676, 679, 680, 677, 678, all one after another. The dyno operator didn't even slow down between pulls. The motor was cycled up and down, up and down, up and down. The car ran a MOTEC and was being tuned for track day @ Sebring. When you consider the power that 6 was making, that it was Twin Turbo, and in a small room with only 5 6' fans blowing, you can really appreciate what the MOTEC does for engine controls.

There isn't really anything wrong with the factory ECM, it definetely will run the motor just fine, its just old and outdated and crazy $$. For roughly the same $$ you can have a modern system that works faster and more accurately. If originality isn't an issue I would always reccomend the modern aftermarket solution over the old original. Its just a better buy. I dont make my living selling stand alone system BTW.