In Peters latest video with the meat thermometer he has confused me even more.

He put a probe on the intercooler fins and on the air outlet of the intercooler.

He is getting temps well above his coolant temps. In other words the coolant in the intercooler is hotter than the coolant from the engine.

How is that possible? He makes a comment about how the intercooler temp should be somewhere between coolant and oil temp. WTF?

Makes me wonder how he has it plumped and where his engine coolant temp sensor is.

His engine coolant sensor should be on the output of the engine showing the max coolant temp. The coolant should not be any hotter anywhere in the system than when it comes out of the engine.


What am I missing?

Mike

Does that cooler have an oil cooler built into the "hot" side of it? Car radiators often have an oil-water heat exchanger built into the tank on the hot side. That's the transmission oil cooler (and sometimes heater). That would be unconventional engineering for an aviation powerplant. Usually you want to keep the oil and coolant circuits far apart even more than you do in an automotive engine...

Now that I think of it, I'm not sure which tank the oil cooler goes in in a car radiator. Regardless...

Older cars, 60's through 90's that I am familiar with had the automatic trans cooler/heater in the bottom shell/tank of the radiator. It helped warm the AT fluid at the beginning at start up and then helped keep the AT fluid at around 180-200 while driving.

But is that the inlet (hot) or the outlet (cold, or I guess not as hot) tank? And by the same token, I was picturing radiators with left and right tanks- which is just a different way to build things. I found what I was picturing, this one's got it on the "hot" side (which doesn't mean it's the only way to build them, there's pluses and minuses to build it into the "cold" side instead). That's the top hose inlet right above the oil line fitting, and the top hose connects the thermostat assembly... at least I thought that the hot water flows from the thermostat to the radiator and the other hose is the return hose. It always heated up first (by touch) before the other hose felt warm.



Either way, I don't think it's such a great idea for an airplane. Granted, turbine engines use fuel-oil heat exchangers (heats the fuel and cools the oil), but if a leak happens to allow the two to communicate, then at least oil and fuel are a lot less different than oil and water.



None of which explains what's going on with Raptor's temperature readings.

My recollection from the video where he discussed the design is that it does not. It's just a simple intercooler hooked into another loop in his coolant lines to bring temps down further.

Eric,

I think you are right. The IC was only connected to the heater loop. I don't think he has oil going up to the front.

So why did he say the IC temp should be between oil and coolant temp?

He either has his coolant temp sensor in the wrong place or its broke. To have higher coolant temps in the front of the aircraft than the engine output is not right. I think it was around 30-40f higher. But not sure thats even possible. that would put his engine coolant temps at over 280F which would not work unless he had a 30+ psi coolant system.

Something does not add up.

Mike

On the topic of technology transfer from automotive to aviation engineering, the long coolant lines on the rear engine/front radiator early-1980s Skoda cars were reputed to have substantial heat shedding properties... so there's that.


(I think I have my old textbook from fourth year heat transfer around here somewhere. Maybe I could run some numbers.)

Mike, many, many things do not add up :-)

I think his comment about the IC temp being between the coolant temp and the oil temp was just from another incorrect assumption about how engines and cooling systems work.

But is that the inlet (hot) or the outlet (cold, or I guess not as hot) tank? And by the same token, I was picturing radiators with left and right tanks- which is just a different way to build things. I found what I was picturing, this one's got it on the "hot" side (which doesn't mean it's the only way to build them, there's pluses and minuses to build it into the "cold" side instead). That's the top hose inlet right above the oil line fitting, and the top hose connects the thermostat assembly... at least I thought that the hot water flows from the thermostat to the radiator and the other hose is the return hose. It always heated up first (by touch) before the other hose felt warm.

Maybe he has the oil cooler being cooled by coolant. Not a great solution but that would explain what he is saying.

Or the oil cooler is in front of the radiator and dumping it’s heat into the coolant after it comes out of the engine. Again not a good solution.

Either way the fact that the oil is being cooled by coolant may be his big problem. Oil is hotter than coolant. Oil temps of 250 are no a big problem for liquid cooled engines with synthetic oil. He has plenty of air available to cool the oil. But coolant temps at 250 or higher is Extreme and not OK. Really should keep coolant below 225. That’s what cools the cylinders.

The sad part is he clearly has an issue with the engine set up. I just wish he would get help from experts. It’s a pretty common knowledge base with known Audi engines. I bet there are 100’s of guys that could help him.

The aircraft is a no go without fixing the cooling issue. And I don’t mean bandaids and little fixes. It needs major help.


Mike

This reminds me of the P210 Vitatoe conversion. Cessna used its own engineers and designers to develop the original P210 powerplant configuration, and it was just okay.

They produced and sold a bunch of P210s.

Then Larry Vitatoe offers another take on the P210 powerplant, and totally transforms the performance. The airframe became like new again.

Peter has taken an unproven airframe and coupled it with a disastrous powerplant configuration. Once he figured that out, he doubled down and continued working without expert assistance, and has fashioned a flying plumbing contraction that should be a case study for all first year engineering students.

Previously he had the aftercooler for the turbos mounted on top of the coolant radiator. Guys that have experience with staged turbos say that the way he has the turbos setup will cause discharge temps of several hundred degrees.

130 knots 75% power with the gear down.

groundbreaking

I was trying to figure out what he'd get out of it. The Austro diesels can be run at a higher continuous power setting that a typical aviation engine, and they are also based on a car engine. If he can run it at a high power setting and we give him some credit for the gear, that would make it a slow Velocity. With the larger cabin, it's not terrible.

Nothing remotely close to what he said of course, and he has very to go before this is a shipping kit.

Edit: this begs the question why doesn't Velocity just make a bigger cabin and accept the speed tradeoff, and I suspect the answer is their customers don't want it. Doesn't bode well for Peter.

Vr is 100. Meat instrumentation included standard. Steady as a rock, thanks to the rocks used for wingtip ballast.

There seems to be zero rigor in the flight test program. Third flight at sundown... is that common for a prototype flight test program?