| Slant Six Forum https://slantsix.org/forum/ |
|
| Very lean and running rough/missing https://slantsix.org/forum/viewtopic.php?t=55750 |
Page 3 of 3 |
| Author: | Chief915 [ Wed Jul 23, 2014 8:27 am ] |
| Post subject: | |
First tank of gas after the repairs netted 18.1 MPG. That was about 50% city type driving and 50% around on various country roads between 50-60 mph. I was hoping for a little better, but I guess that's not too bad anyway. The truck is a short bed D100 with 3.21 gears according to the sticker under the hood. Thoughts? |
|
| Author: | Chief915 [ Mon Aug 04, 2014 7:09 am ] |
| Post subject: | |
Over 915 miles since the head work and carb rebuild, I've averaged 17.6 MPG. That 915 miles is a very good average of how and where I drive on a normal basis, in other words it didn't include anything out of the ordinary. That was with the factory lean burn ignition setup. Last night I upgraded to the HEI style ignition, with an older vacuum/mechanical advance distributor and a 4 pin GM module. I filled the tank again this morning, so we'll see if/how much the ignition upgrade helps fuel mileage. |
|
| Author: | nm9stheham [ Sat Aug 09, 2014 9:48 am ] |
| Post subject: | |
I'd like to hear what you get as an improvement with the HEI. BTW, you are moving a cinder-block shape through the air so mileage will not be much better, IMO. I can recall a Ford F250 with a 300 straight six that could get around that. Same gearing on a car with a 225 would be around the 22-23 range at 65-70 mph. |
|
| Author: | nm9stheham [ Sat Aug 09, 2014 10:06 am ] |
| Post subject: | |
Quote: Very good Ed. Quite a sleuthing job there. I still say though that good valves will not burn if run lean. One of my good friends Wayne takes care of the planes for a rich dude here in Maryland, and he says the temp maxes out as you make it leaner, and then it hits a point where it is so lean it gets cooler again. You can run an aviation engine 50 degrees off of that max EGT for best fuel economy. That is what pilots do all the time. They dial out the fuel until the EGT maxes and then go either 50 degrees cooler on the lean side or on the richer side. He says richer sounds and feels better, but leaner actually gets a little better mileage. In flying instruction, I was always taught to adjust the mixture to the rich side of max EGT, not to the lean side ever. Running right on the max EGT can be rough and anything on the lean side is quite rough. I've never yet run into a pilot who ran an engine on the lean side of peak EGT, becasue with a single EGT sensor for the whole engine, the cylinder mixture variations would mean that one cylinder is likely going to be waaaay too far lean if you run the whole exhaust on the lean side of peak EGT. Losing a valve/cylinder in an airplane is bad juju when that 3rd dimension is in play! That rich dude likely has all 4 or 6 cylinders monitored with seprate EGT sensors, and probably has a fuel injection engine with the injectors balanced to deliver equal mixtures at cruise. With that setup, you can safely run closer to peak EGT. Also, 'aviation low lead' has more lead in it that automobile gasoline ever had. So plane engines get a ton more lead that any auto engine ever did to help valve face and seat life, especially versus auto low/no-lead gas today. So that means a direct comparison between the 2 is not quite valid. (Add in air cooled versus water cooled, and there is another difference.) |
|
| Page 3 of 3 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|