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The flow isn't as constant/steady on the return as most think. The second you don't have constant flow over the sensor the ethanol content drops and the fueling is automatically adjusted. It's also a tiny 3/8 opening (actually a bit smaller). So its also a restriction on the supply and return in most cases.
An ethanol sensor uses permittivity ratio of gasoline to ethanol to calculate the % of ethanol content. If the pump is properly sized there will always be at least a small amount of fuel passing through return. And any change in content as fuel is drawn from the tank will be gradual, except when new fuel of drastically different content is added to the tank. So other than a few seconds of latency effect, it should be okay to have it in the return close to the fuel rail outlet.
It'd be interesting to see a data log with a sensor in each location as confirmation.
The flow isn't as constant/steady on the return as most think. The second you don't have constant flow over the sensor the ethanol content drops and the fueling is automatically adjusted. It's also a tiny 3/8 opening (actually a bit smaller). So its also a restriction on the supply and return in most cases.
Every setup I have ever done has been in the return line and has never had a issue. My personal truck has been on Holley since 2014.
Every setup I have ever done has been in the return line and has never had a issue. My personal truck has been on Holley since 2014.
I'd guess you had a fuel system that had a steady return flow 100% of the time... That or Holley doesn't sample the content as quickly/often as the megasquirt software does. Defiantly has caused issues with every MS car I've tuned with a flex sensor when plumbed in the return. Can't speak for Holley... If you read around there are many articles written by well known tuners stating the most consistent location is on the feed line.
This may just be common sense, but there will be a delay no matter what you do. So ideally I’d think you want to read the fuel on the way to the rail as close to the pump as possible. Not the fuel exiting the rail.
I'd guess you had a fuel system that had a steady return flow 100% of the time... That or Holley doesn't sample the content as quickly/often as the megasquirt software does. Defiantly has caused issues with every MS car I've tuned with a flex sensor when plumbed in the return. Can't speak for Holley... If you read around there are many articles written by well known tuners stating the most consistent location is on the feed line.
This may just be common sense, but there will be a delay no matter what you do. So ideally I’d think you want to read the fuel on the way to the rail as close to the pump as possible. Not the fuel exiting the rail.
I can't say anything for MS as I've never used it or had a customer that has used it. As far as common sense I would think that the fuel before the rail and after the regulator would measure the same ethanol content.
Every setup I have ever done has been in the return line and has never had a issue. My personal truck has been on Holley since 2014.
I've seen it happen on many vehicles over the years. Most good aftermarket computers with true flex fuel support (hint, not Holley) have a latch function for the ethanol content reading to prevent it from getting bad readings if it's placed in the return line since flow drops under load and it can uncover the sensor inside.
General rule of thumb is to put it in between the regulator and fuel rail exit in a typical front mounted regulator setup, that way it's not a restriction feeding the injectors and is under constant pressure/supply still being in the pressure side and not the return side. When placed in the return line it CAN uncover the sensor and cause problems depending on where it's placed in the return, how much flow is returning, etc. If the sensor is placed in a big long straight length of return hose underneath the car it's most susceptible, if it's up top in the engine bay by the regulator it seems to be less susceptible. Another option is that Motion Raceworks makes a nice high flow passthrough mount for flex fuel sensors so that you can put it in the pressure side before the injectors/rails and it won't impede flow.
As for that video, not watching and wasting my time.
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