Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

[Duke W.]

I'm collaborating with a member of the Northern Califonia Chapter who is also a graduate of the U. of Wisconsin Engine Research Center and spent his career with Chevron on an article about modern gasoline for the Corvette Restorer. We want to sort out all the issues, separate the facts from the myths, and propose some action to help with problems members are experiencing.

In that regard I need some data. For those of you who have IR guns, I need carburetor/FI fuel meter temperature data.

With the car fully warmed up after a drive, remove the air cleaner and shoot the carburetor bowls. Also shoot other areas on the carb and report any differences over about 5 degrees. My hunch it that the whole carb will be at a fairly uniform temperature.

It will be easy on FI since nothing is in the way of a direct shot to the fuel meter.

Please identify the model year, engine option (by RPO ID or advertised HP), approximate ambient temperature, and whether the heat riser is operating properly, wired open, or the passage is blocked. If NOM or modified, specify the displacement, manifold material, and carburetor type.

Report your data in this thread. Thanks!

Duke

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Duke, Just drove about 35 miles in 82 degree ambient. Here are the temps, shot with a Craftsman IR gun. Car is 63 L84 (stock), no heat riser. Car is running 100% 110 racing fuel:

Fuel Pipe (as it leaves frame): 152 F
Fuel pump: 159
Fuel Filter: 146
Fuel pipe (between filter and meter inlet): 149
Fuel meter inlet: 125
Fuel bowl (side): 148
Spider: 138
Nozzle block (#8): 152

Hope this helps,

[Duke W.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Excellent data set. Thanks!

I want to add another test. After the initial measurements with the engine idling after a drive of at least 15 minutes, close the hood and shut down the engine. Wait about five minutes, then open the hood and take the same measurements. This will yield temperature changes after a "hot soak."

With peak summer temperatures approaching, now is the perfect time to gather this data.

Duke

[Clem Z.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

i think a lot of heat a FI sees is the hot oil splashed against the bottom of the adapter plate. if i owned a FI corvette and i had a heat related problem i would fabricate a oil splash shield like GM sells for the BBC part #12555320

[Jim L.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Fuel Pipe (as it leaves frame): 152 F
Fuel pump: 159
Fuel Filter: 146
Fuel pipe (between filter and meter inlet): 149
Fuel meter inlet: 125
Fuel bowl (side): 148
Spider: 138
Nozzle block (#8): 152

Hope this helps,

I have some data that suggests fuel meter temperature is a function of both ambient and engine temperatures. What was your engine temperature?
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For example, at an ambient temperature of 77F (not far from the ambient you saw), and an engine temperature of ~155F, I've seen a fuel meter temperature of 115F. It should be noted that this is with the vehicle in motion, so there is air circulating around the FI unit, which also affects fuel meter temperature.... admittedly not quite a fair comparison.

Jim

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Jim, the measurements were on an engine that had been stopped for a minute, with the hood up (while I got the meter). I didn't look at the instrument panel gage or shoot the engine anywhere except the fuel-oriented components, so I don't know for sure what the engine temp was, but, knowing my engine, I'm guessing 180 or so. Note that I did take one measurement on the top of the fuel meter, it was much cooler than the side, ~123 F, I think. The top is not in contact with the fuel, though, so I didn't think that one was really relevant.

I'll take a ride tomorrow and repeat those listed measurements, as well as the coolant, and leave the engine running for the measurements.

[Stuart F.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Duke;

Interesting thread. I have data from my 63 L-76 from several years ago when it was in completely stock configuration using 10% Ethanol premium gas, and with a need to address the fuel percolation problem (gas stink) in my attached garage. I will dig that out and do a current test (as you suggested) this weekend in our summer Florida ambient conditions. I will then respond with my findings in a couple days. I have made a number of minor changes to address the problem which have been quite successful, all of which are easily reversable for NCRS judging.

Stu Fox

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

New data @ 82 F ambient (again!) after 45 mile drive:

First number is idling, immediately after drive, second number is after five minute heat soak:

Engine: 171, 198 F
Fuel pipe leaving frame: 181, 156
Fuel Pump: 176, 167
Fuel Filter: 150, 154
Fuel line: 158, 167
Fuel bowl -side: 148, 152
Fuel bowl - top: 108, 93
Spider (#8): 141, 148
Nozzle Block: 152, 157

[Duke W.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Excellent! Now we need some data from a carbureted engine.

All your numbers are in the ballpark I was expecting except the frame fuel pipe exit. I didn't expect it to be so high. It must be picking up a lot of radiant heat from the exhaust manifolds. So the fuel heating is starting before it even gets to the pump.

Duke

[Clem Z.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Excellent! Now we need some data from a carbureted engine.

All your numbers are in the ballpark I was expecting except the frame fuel pipe exit. I didn't expect it to be so high. It must be picking up a lot of radiate heat from the exhaust manifolds. So the fuel heating is starting before it even gets to the pump.

Duke

is the fuel line inside or outside the frame on these cars. if it is inside it is picking up heat from the exhaust system. i have seen this back in the day when we added dual exhaust to cars that had the fuel line inside the frame we would have vapor lock till we moved the fuel line. this was eons before ethanol in the fuel.

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Clem, the fuel line is mostly inside the frame's side rail, it exits near the battery. The line seems to be hot immediately upon exiting the frame, but that area is only inches from the exhaust manifold, so I'd agree with Duke that the manifold is radiating significant heat on the line as it exits the frame. The exhaust is not really close to the frame's side rail rearward of that, but it would be interesting to measure the frame temp in that area to see if that might be adding to the problem.

Jerry Bramlett's says that insulating the fuel line from pump to FI unit makes percolation worse, which makes sense if the fuel is already very hot before it gets to the pump.

I wouldn't have expected the pipe to be quite so hot, then cool so fast after shut-off, so I'm thinking one of my readings may be faulty. I may put a sensor on the pipe and try again, as its difficult to get the gun close enough to be sure I'm reading the pipe.

[Clem Z.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Clem, the fuel line is mostly inside the frame's side rail, it exits near the battery. The line seems to be hot immediately upon exiting the frame, but that area is only inches from the exhaust manifold, so I'd agree with Duke that the manifold is radiating significant heat on the line as it exits the frame. The exhaust is not really close to the frame's side rail rearward of that, but it would be interesting to measure the frame temp in that area to see if that might be adding to the problem.

Jerry Bramlett's says that insulating the fuel line from pump to FI unit makes percolation worse, which makes sense if the fuel is already very hot before it gets to the pump.

I wouldn't have expected the pipe to be quite so hot, then cool so fast after shut-off, so I'm thinking one of my readings may be faulty. I may put a sensor on the pipe and try again, as its difficult to get the gun close enough to be sure I'm reading the pipe.

the closeness of the fuel line may not have been a problem on the corvettes back in the days of pure gasoline but with gasoline reformulated to meet the new emissions and who knows what a just a few degrees of heat can do. a good test would be to run a temp rubber fuel line outside the frame away from the exhaust and engine heat and see what happens. this was the only way i could stop vapor lock on my 74 pickup when i installed a 500 HP BBC engine with duel exhaust and headers

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Actually, I was wrong about the fuel line exiting the frame in the battery area, it just goes under the battery tray and enters the frame farther to the rear. I should have known this, I installed there.

In any case, I'm going to wrap the line with insulation and go for a ride, then measure temps.

[Michael G.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

I put insulating tape on the fuel line, as it emerges from under the battery tray, all the way to the fuel pump, then to the fuel filter. I put insulating cloth between the filter and its bracket, then insulating tape on the line to the fuel bowl inlet.

New test; Ambient 76 F

Engine: 172 F, 195
Fuel pump: 152, 154
Fuel Filter: 138, 152
Fuel bowl (side): 141, 144
Spider: 137, 143
Nozzle block (#8): 141, 149

These numbers are better, especially the fuel filter, but the most interesting thing is that the idle was smooth after the ride and the engine started on first crank after ten minutes heat soak! I'll have to repeat the test when the ambient is 82 again.

[Duke W.]

Re: Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

Great work, Michael! Can you snap a photo of your insulation job?

It looks like insulating that few inches of fuel pipe between the battery tray and outlet nipple can make a noticeable difference. Maybe it should be carried farther forward to cover the hose into the fuel pump inlet. It appears that a lot of the heat is being picked up there, which I wouldn't have suspected before you posted your data. This would apply to both FI and carbureted engines since they (small blocks) use the same pipe along the frame rail. Big blocks probably have a similar problem.

There's very little pressure in the spider at idle, so percolation is probably happening, which is causing idle roughness, and even a few degrees reduction helps.

The issue is the 50 percent boiling point of E10 gasoline, which is less than straight gasoline, so we have to figure out a way to keep the fuel cooler going into the fuel pump and cooling down the fuel bowls.

Now, we need some input from the carb guys.

Duke