[newaza]

Hello fellows. Any chance to get an ethanol percentage hold feature on flex fuel when at high loads? Say lock in the last low load reading when throttle goes over a certain percentage, maybe half or 3/4 throttle? A feature such as this is a thing on some other platforms and can really be considered a safety feature. On very high boost drag racing setups the engine can be destroyed very quickly if for some reason the ethanol reading drops from 80-90 percent down to 0-10 percent while on a pass at the track at boost levels that can be well over 30 psi. This can happen due to sensor being on return line and marginal supply volume, noise in wiring or sensor failure. Of course moving sensor to supply side or more supply volume and trying to eliminate any noise can help first two potential issues but the sensor can also suddenly fail during a pass as well. This simple added feature could save someone an engine in that event.

Thanks!

[PSIG]

Interesting idea. At first glance, I would simply insert a default value for sensor failure (out of expected range), as we can't ensure the low-load reading just before high-load was accurate either. This can be a tune setting for minimum % or use safe rich %. However, it could instead be a Lambda limit to cover this and other potential lean-outs, again defaulting to a limp or rich setting. Do we have any statistics for how often this is an issue, and which ones primarily? Internet stories are not a basis for problem context, and other solutions may not be best approach for this system.

[newaza]

Not really just an internet story as I have practical experience of it happening to me. My setup the ethanol content sensor is on the return line. At very high boost and high rpm I have had the ethanol reading drop to a very low number. I assume this was due to flow through the sensor being reduced and maybe aerated as the engine was using most of the supplied fuel under those conditions with little being left to flow through the return line and sensor. My setup uses a walbro 525 pump, an aeromotive boost referenced return regulator, and 1500cc injectors. this is used on a much modified mazda 1.8 engine that sees over 35psi on a regular basis and is used for mostly 1/8th mile drag racing but also occasional street diving. Never had it dynoed but it has trapped just under 110mph in the 1/8th so far so going by hp to weight vs trap speed calculators its likely somewhere in the middle 500hp range. The car is full time e85. I added the ethanol sensor as i wanted to really use the fuel temp component to make some minor tune adjustments factoring in fuel temperature. I was also considering to mix in pump fuel for street diving but hadnt done that yet. Fortunately when it happened to me I was just out testing and had all the ethanol content scaling at 100% with no timing adjustments so no harm was done. I can move the sensor to the supply side which should fix the ethanol percentage drop off reading but I like having it after the fuel rail to measure the fuel temp after the rail.

[PSIG]

That's all fine, and I do not know the cause of the sensor failures to read or report accurately; but your build and use are not the point. Not disregarding yours, but anything from a golf cart to a land-speed racer would be equally deserving of protection if the sensors are shown to be unreliable with proper installation and integration.

So, the two points are 1) what are the real-world statistics of the failures (why) and rate (common or rare)? And 2) what is the best approach to either improving the failure rate -or- providing an effective safety mechanism?

If we cannot establish reliable data for #1, then I'm suggesting we consider a broader approach of Lambda limits to answer #2, if this or other lean-out causes are prevalent for any other reason. My opinion is subject to change with additional data or perspective.