ECM Issues - No Start

[ram_g]

Reading this thread with absolute fascination. Congratulations Macro and keep it coming!!

The only question I have is with regards to the following (reducing # of cranks for startup). I was under the impression that this was a deliberate move so that the engine could build up sufficient oil pressure before starting? I know that my 2016 C7 does the exact same thing as my 1991 ZR-1 and it has been explained as such.

Originally Posted by Macroblock

UPDATE:

I didn't like the original factory start-up procedure because it took too many cranks before it started.

The firmware now monitors the coolant temperature sensor and engine RPM and when appropriate, hi-jacks the start-up process.

For the first time ever, my ZR1 now starts with the first spark in cold, warm or hot conditions.

Also - got a website up to link photos to ongoing developments. Came with a free email: peter@zr1ecm.com

[Ccmano]

Originally Posted by ram_g

Reading this thread with absolute fascination. Congratulations Macro and keep it coming!!

The only question I have is with regards to the following (reducing # of cranks for startup). I was under the impression that this was a deliberate move so that the engine could build up sufficient oil pressure before starting? I know that my 2016 C7 does the exact same thing as my 1991 ZR-1 and it has been explained as such.

That has always been my understanding. As a matter of fact its one of the factors that caused engine failures early on when plant personnel revved the engines to high rpm in cold weather conditions during the Transporter loading process. As a result the time to fire the engine was lengthened and the revs were limited in cold conditions. Its written up in the book Heart of the Beast. It caused quite a stir and weeks of shipment delays. Personally Im fine with the longer startup.
H

[Macroblock]

The stock ECM provides an injection delay of 1 or 2 seconds, which is not nearly enough time to prime oil into the LT5 engine. My inclination is that it would take closer to 30 seconds to prime and pressurize all the oil passages with a typical start-up crank of less than 400 RPM.

As I reverse thru the functions of the Engine Control Module (ECM) and the Direct Ignition Module (DIS), here are my observations.

The original starting process involves a fuel injection delay merely to allow the Ignition Module to synchronize with the crankshaft and to allow fuel pressure to build up.

When the engine is turned over, and the DIS is satisfied with the signal it's getting from the crankshaft sensor, it generates successive signals to the ignition coils and provides a stable 0/5 VDC square wave to the ECM on the Crank Reference line (D18). This square wave signal will change states 8 times per crankshaft revolution - this equates to 4 complete pulses per revolution.

Once the ECM sees an appropriate number of Crank-Ref pulses per second, it energizes the fuel injectors and in due course the engine starts.

This means the engine normally doesn't receive fuel for the first second or two after cranking begins.

To improve starting, my firmware injects fuel, when appropriate, before the DIS energizes the coils, which means the engine will come to life sooner.

[Macroblock]

Originally Posted by Ccmano

That has always been my understanding. As a matter of fact its one of the factors that caused engine failures early on when plant personnel revved the engines to high rpm in cold weather conditions during the Transporter loading process. As a result the time to fire the engine was lengthened and the revs were limited in cold conditions. Its written up in the book Heart of the Beast. Cause quite a stir and weeks of shipment delays. Personally I?m fine with the longer startup.
H

In actual fact, the ECM does not have an input for oil pressure. I guess it wasn't a consideration for software control back then.

I find the the LT5 pressurizes its oil very quickly when cold because the oil cooler feed line is disengaged by a thermostatically controlled valve.

A potential problem occurs with oil pressure when the engine is in a warm state and the oil cooler is engaged. On a warm start-up, oil flow tends to fill the cooler network before traveling to the to top of the engine, including the timing chain area.

The workaround for the warm start scenario relies on the elevated placement of the oil filter. The LT5 oil filter has a check valve in it which stores oil and releases it after the engine starts. This provides oil to the top of the engine when the thermostatically controlled oil cooler valve is diverting oil away from the engine.

It is a very good idea to restrict engine RPM during warm up. The stock ECM for the LT5 does do this by refusing Full Power Mode (even when selected) until the engine is warm.

Notwithstanding, the original ECM firmware should have had "idiot-proof-code" in it to prevent abusive behavior like that of the car-jockeys. It is my understanding the newer Corvettes do have this feature.

[-=Jeff=-]

Very cool.. using same Arduino? Or another added to the ECM?

[Macroblock]

At this point the single Arduino I installed directly to the Gates of the 8 Power Transistors can perform most of the ECM operations related to fuel management and ignition timing.

Ironically, the largest drain on computational resources is the Sequential Injection Function, which provides very little advantage (if any) to fuel economy, emissions and overall drive-ability.

My sense is it would be possible to take an L98, LT1 or an LT5 engine-control-module and make it work with 1, 2, 3 or 4 Arduinos. In addition, it would be possible to gut an L98 or LT1 computer and re-engineer it for LT5 use.

[-=Jeff=-]

Originally Posted by Macroblock

At this point the single Arduino I installed directly to the Gates of the 8 Power Transistors can perform most of the ECM operations related to fuel management and ignition timing.

Ironically, the largest drain on computational resources is the Sequential Injection Function, which provides very little advantage (if any) to fuel economy, emissions and overall drive-ability.

My sense is it would be possible to take an L98, LT1 or an LT5 engine-control-module and make it work with 1, 2, 3 or 4 Arduinos. In addition, it would be possible to gut an L98 or LT1 computer and re-engineer it for LT5 use.

If you are interested in playing with that. I have a couple under hood L98 ECMs

[Macroblock]

OK - Great. Likely over the winter.

[Macroblock]

Just an update to provide this link on troubleshooting the C4-ZR1-ECM:

http://zr1ecm.com/youfix.html

[-=Jeff=-]

Nice. Will you be going into more detail on the internals of the ECM? I have one I need to fix, I should probably pull it apart and look at the solder joints first.

Lastly these are conformal coated aren't they, what is the best way to remove the coating to get to the pins?