Ethanol Laced Modern Gasoline -Carburetor and FI fuel meter temperatures

[Clem Z.]

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

how about using a air to fluid cooler in the output from the fuel pump like a power steering cooler mounted outside on the core support ?? that should drop the fuel temp.

[Duke W.]

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

That's a fairly complicated solution, and it wouldn't provide much help at idle and in low speed driving where the problem is most acute.

I'm thinking along the lines of a lose fit insulation sleeve on the fuel pipe - like what you see on plug wires passing close to header pipes - and a simple radiant heat shield to protect the pipe from direct radiant heat transfer from the exhaust manifold - something that can be secured with the bolt that holds the fuel pipe clip in that area - a solution that is easy-on and easy-off for Flight judging.

I have to spend some more time looking at the layout on the SWC. I know there are a lot of creative minds out there. Let's hear some brain storming.

Duke

[Michael G.]

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

Here are some pics, the work is just temporary and looks it:

DSC00855.jpgDSC00856.jpgDSC00857.jpgDSC00858.jpg

[Michael G.]

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

Duke the insulating cloth I used is tubular, if this really works, I am going to disassemble the fuel lines and slip it over them, then tape the ends. Here's another pic:

DSC00859.jpg

I had been considering attaching the Peltier device shown below to the side of the fuel bowl (with a fan, heat sink, and temp switch), but it really would have to continue operating for a while after shut-off to be effective. I don't think the battery would last long with such a draw, so that's out.


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[Stuart F.]

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

Duke;
I'm not out of the game yet. We have company down from up north trying to cool off so I haven't had an opportunity to test mine today. But, in reading what Mike has done I wanted to comment that I believe the insulation from the pump to the filter and carburetor is the most crucial for heat soak, specially for us with the L-76 engines. As you know, the fuel pump acts as a check valve and traps the fuel in that line after shut down, so when it expands it can only go one way and that is to overcome the float controlled needle and seat in the carburetor.

In my setup, you might say I have accepted that as a given and have addressed it by trying to accommodate the fuel expansion. I have lowered my float levels and use Tomco inlet valves in place of the needle/seats which seem to control the fuel flow better. Also, I have isolated my AFB from heat better by using an L-75 phenolic 3/8" spacer sandwiched between two L-76 base gaskets. I use an electric choke to eliminate the steel heat tube and hot air source, and a fuel hose from the filter to the carburetor in place of the steel fuel line (also needed due to the elevated carb).

I will try to get you the temp readings as soon as I get an opportunity, but as I recall, the changes lowered my carb temp by some 25 to 30 degrees. I gor to locate my "before mods" notes and do another test under the conditions you noted.

Some other quirks I discovered in my quest to get my 3461S sorted out include: 1) the 3461S and 3721SB have taller anti-percolation tubes (some 3/32") on their primary clusters than other models (3720SA),
2) 3461S's have vapor vent holes above all four butterflies which I plugged with rivet nail heads, which are cut to length and tapped into the holes. They have a few splines just below the heads so they hold in very well, but can be easily tapped out with a pick from the inside.

More later;

Stu Fox

[Russ S.]

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

Duke, Here are the results of my 66 327-300HP auto. Ambient temp was 78. Engine temp 197

fuel pipe at frame 133/130
fuel pump150/145
fuel pipe at carb 165/165
bowl at inlet 134/137
side of bowl 150/146
top of bowl 116/108
engine temp after 5min.210
second number is after 5 minutes shut off.

[Michael J.]

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

Duke, I will take my '67 L71 out tomorrow, now that it has stopped raining, and get the info for you. I also mentioned this to our chapter which has several FI C2s, hopefully they will chime in as well. I guess you don't care about the temps in the secondary carbs, right? Just the primary center one?

[Duke W.]

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

I'd like to see the temps of all three bowls. Also, let me know if you still have the OE ported vacuum advance or have changed to full time. Ported vacuum advance will make the exhaust manifolds hotter and radiate more heat to the frame fuel pipe.

Thanks for the data, Russ.

Duke

[Clem Z.]

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

this is why we drilled a .015 hole in the valve plate on take take apart fuel pumps and GM went to the 3 port return line fuel pumps. "the fuel pump acts as a check valve and traps the fuel in that line after shut down, so when it expands it can only go one way and that is to overcome the float controlled needle and seat in the carburetor".

[Michael J.]

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

OK Duke, here are the temps after my morning run, some at some pretty good speeds clearing out those cobwebs on the near empty roads around here.

Stock '67 L71 internals, B26 VAC hooked to full time vacuum. First temp is after the drive idling for 15 minutes, the second is after shutdown and waiting 5 minutes.

Temp Gauge on instrument panel: 200/210

Water Pump: 220/225

Thermostat Housing: 198/194

Fuel Pump: 154/143

Inlet fuel line at first fuel block: 169/171

Second fuel block: 170/165

Front Carb bowl: 145/142

Center Carb bowl: 120/122

Back Carb bowl: 133/136

Ambient Temp. 84 degrees F.

[Duke W.]

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

The front and rear carb bowls probably run hotter because they are passing little fuel, which acts somewhat as a cooling medium. Also, the steel fuel lines have low thermal resistance and readily transfer heat. They look better than rubber hoses, but probably increase fuel temperature between the pump and the carb inlets.

I'd like to see data from '62-'65 300 HP engines with the phenolic spacer under the AFB and compare the data with the '62-'67 SHP engines with the aluminum manifold and no thermal spacer.

Duke

[Michael J.]

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

I forgot to mention my heat riser is in place and operating as stock.

[Stuart F.]

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

Before I undertake my temp readings with my IFR gun, I'd like to hear some advice on how best to use it so as to get the most accurate readings. Mine has a MAX/MIN button to display same when held for one (1) second. The reason I ask is that I have noticed it will hunt a lot if I let it (trigger in), specially on manifold spots - both intake Water Manifold, and Exhaust Crossover, as well as Exhaust Manifolds. My Laser dot is some 8 degrees off actual measuring spot which one has to allow for as well. I bought mine at a "Sun and Fun" flyin in Lakeland, FL a number of years back and have replaced the battery at least once - so it may not be the latest tech.

Stu Fox

[Robert S.]

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

Has anyone considered ceramic coating the inside of the exhaust manifold and exhaust pipe?

[Duke W.]

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

Request we restrict this thread to gathering data. Once data for several engine configurations is stated another "solutions" thread can be started.

Let's keep the horse in front of the cart for now.

Duke