Thanks, this is logical.ijames wrote: ↑Mon Aug 23, 2021 10:52 am Trying to approach this from a different direction, this may not be useful. Either the engines are actually making 10% different power, or the power is being made but is being lost in one of them. Start with #1. You say the AFR is the same so the fueling is the same, but do you have any way to measure actual engine airflow or fuel flow? Can you log the ecu data and compare the engines that way? If somehow the airflow is restricted on the weak chassis you would see the same afr on the lambda meter if the ecu tune is good but different maf or map or ve (or whatever your ecu reports) readings. As for #2, these are making about 70 hp (I think you said), so 10% is 7 hp. If you are making the power but it isn't getting to the wheels it must be getting lost due to friction and should show up as heat. I would think that 7 hp (= 5225 watts) worth of heat should show up with an IR thermometer somewhere after a bit of time under load. Make a run on the dyno or a lap or whatever, then take readings on the engine, chain, sprockets, cv joints, rear end, all the brakes, everything you can. One of those cheap ir cameras would be great, or try to video the display on a simple ir thermometer while also showing where the laser dot is aimed and just slowly scan it over everything as soon as you shut down the motor, then do the other car the same way. Good hunting.
I believe that the same amount of air and same amount of fuel is going into the engine in both chassis. '
To make sure that it's not an airflow restriction, the air boxes and ducting were swapped also in one experiment.
The injector pulse width wasn't logged into a file, but since this is being run in open loop Alpha-N mode and we're swapping the control boxes, it's unlikely that fuel was different either. That said, we'll look at the injector pulse width explicitly, too. I'm not sure off the top of my head whether there's already a fuel pressure sensor there, so I guess to be completely sure about the fuel flow one would need to compute/log the injector pulse width net of the offset times the square root of the fuel pressure.
I agree that five kilo Watts should show up over time on a thermometer. I have a flir thermal camera for the phone and infrared thermometer. We have to hold the load on the dyno for a minute or so. A 7hp or 5.2kW power loss for a minute will heat 37 kg of steel by 20C, if I did the math right!