PMD
Well-Known Member
Those who have stumbled upon my posts and rambling replies know that I no longer like SI and gasoline fueled engines. Reality is: every once in a while I have to drive one, and this week has been one occasion. A competitor to my "day job" customer got into trouble with a project and had to hire them to come in, so I was called out (contractor) to run one crew using the competitor's equipment and I had to take one of their fleet 1500 GM 4x4 CCs with a 5.3 (I believe LS1).
A day later, with 255 kms showing as range left in the tank, I set out for a 140km round trip to job site from hotel, and about when I arrived, I was caught by surprise by a fuel warning light.. Jobsite was 100% diesel, so another contractor had a truck going into town and agreed to pick up a 5 gal can of gasoline so we could be sure to make it back to the hotel. One of my crew poured the jug into the tank, and gave it back to our benefactor. When were getting into the truck, I asked him if he checked the contents of the can before he poured it in, but he replied by asking "why would I do that?" Well, when I started the engine, he immediately understood why it might have been a good idea to sniff test the jug - it barely ran at all.
Now, this is where my old job a being an auto mechanic kicked in. I guessed it was diesel in the can, and that would result in a horrible octane value for the 50/50 mix of E10 and D2 but I hoped the knock sensors would simply back the timing off, hopefully enough to keep running. Since we were on a very tight schedule, and in pretty much middle of nowhere, I thought it worth trying to see try moving to hear if it went into pre-combustion apoplexy and see if it was potentially drivable. I could manage about 30 kph once I found a throttle setting that was "just right". I kept on trying throttle and RPM variations to try to get a bit more out of it, but as I did, it came to me that this thing probably has an adaptive ECU programme, and it was busy trying to learn what I was trying to do with whatever was in it's fuel tank (not sure how it looks for E85 nor what that would look like with what was there). Over the following hour and a bit, it decided what it could pull of and allowed me to get the speed up to 90kph and able to climb the small grades of the route with only small loss in speed.
I topped it off with E10 and it immediately began to run significantly better, an over the next couple hundred klicks, it once again learned how to drive with the resultant inputs. It started with an idle miss and often backfires of rapid throttle input and ended up pretty much as it began.
It was in no uncertain terms incredible demonstration of the skill and expertise of the people who designed the engine and those who wrote the operating software. I could NEVER have done this with a carb and distributor (or more to the point carb or injected magneto engine) nor would I have tried. The takeaway is that given sufficient resources, one can indeed make a modern SI engine exceedingly capable.
Now, before everyone runs out of throws a GM crate LSx and automobile ECU into their airplane: remember that this was a truck, where an engine failure was an inconvenience, we need to fast forward to the next day. I pulled off of the highway to drive down the last mile of gravel to site, and the engine started running rough (same tank of fuel). Stopped to log in, returned to truck and it would not start. Would not even crank. A little orange lock appeared around a little orange truck icon. The ECU for some reason decided it no longer LIKED me and my fuel so it simply shut me out. A cold reboot (disconnect battery) and it returned to exactly where it was an hour before - running just fine.
There are a dozen or so takeaways from this experience, so I will throw the floor open for those to surface.
A day later, with 255 kms showing as range left in the tank, I set out for a 140km round trip to job site from hotel, and about when I arrived, I was caught by surprise by a fuel warning light.. Jobsite was 100% diesel, so another contractor had a truck going into town and agreed to pick up a 5 gal can of gasoline so we could be sure to make it back to the hotel. One of my crew poured the jug into the tank, and gave it back to our benefactor. When were getting into the truck, I asked him if he checked the contents of the can before he poured it in, but he replied by asking "why would I do that?" Well, when I started the engine, he immediately understood why it might have been a good idea to sniff test the jug - it barely ran at all.
Now, this is where my old job a being an auto mechanic kicked in. I guessed it was diesel in the can, and that would result in a horrible octane value for the 50/50 mix of E10 and D2 but I hoped the knock sensors would simply back the timing off, hopefully enough to keep running. Since we were on a very tight schedule, and in pretty much middle of nowhere, I thought it worth trying to see try moving to hear if it went into pre-combustion apoplexy and see if it was potentially drivable. I could manage about 30 kph once I found a throttle setting that was "just right". I kept on trying throttle and RPM variations to try to get a bit more out of it, but as I did, it came to me that this thing probably has an adaptive ECU programme, and it was busy trying to learn what I was trying to do with whatever was in it's fuel tank (not sure how it looks for E85 nor what that would look like with what was there). Over the following hour and a bit, it decided what it could pull of and allowed me to get the speed up to 90kph and able to climb the small grades of the route with only small loss in speed.
I topped it off with E10 and it immediately began to run significantly better, an over the next couple hundred klicks, it once again learned how to drive with the resultant inputs. It started with an idle miss and often backfires of rapid throttle input and ended up pretty much as it began.
It was in no uncertain terms incredible demonstration of the skill and expertise of the people who designed the engine and those who wrote the operating software. I could NEVER have done this with a carb and distributor (or more to the point carb or injected magneto engine) nor would I have tried. The takeaway is that given sufficient resources, one can indeed make a modern SI engine exceedingly capable.
Now, before everyone runs out of throws a GM crate LSx and automobile ECU into their airplane: remember that this was a truck, where an engine failure was an inconvenience, we need to fast forward to the next day. I pulled off of the highway to drive down the last mile of gravel to site, and the engine started running rough (same tank of fuel). Stopped to log in, returned to truck and it would not start. Would not even crank. A little orange lock appeared around a little orange truck icon. The ECU for some reason decided it no longer LIKED me and my fuel so it simply shut me out. A cold reboot (disconnect battery) and it returned to exactly where it was an hour before - running just fine.
There are a dozen or so takeaways from this experience, so I will throw the floor open for those to surface.
