160 thermostat vs, MPG
10-13-2012, 10:40 PM
#1
160 thermostat vs, MPG My tuner suggested a 160 degree stat when he did the tune....It seemed to work fine thru this hot summer. Fans come on at 175 and kept it close even in hot weather..l would get mileage anywhere from 14 to 20...Well, now the weather is alot cooler (60 ish) and the temps run now around the 160 mark. I recently took about 3 hr trip, run along about 65-70 mph very conservitive, and only got 12mpg....Will this cooler running of the car make it use MORE fuel? Would it be better off using the stock stat?
Car specs,
71 chevelle
lq4/4l80e
3200 yank stall
.600 lift/230-236duration cam
.355 gears
26" tires
Rick
Car specs,
71 chevelle
lq4/4l80e
3200 yank stall
.600 lift/230-236duration cam
.355 gears
26" tires
Rick
10-15-2012, 06:43 AM
#4
Flywheel,
If you're chasing down everylast mpg, try the factory tstat with a matching fan strategy. I put some thoughts below on the topic if your interested. However, I don't think it would be responsible for an 8 mpg drop on the highway, I would log your 02 readings while steady state on the highway-I use Torque Pro with my android and a 15$ OBDII bluetooth connector I got off ebay.
Feel free to ask any questions if I can help. Here are my thoughts based on my experience as a cooling sytem engineer.
The best thermal efficiency will be had at the highest engine operating temperatures. For 2017 emissions targets(no longer NOx, but CO2 restraints which means better gas mileage), industry is looking at raising coolant temps even further--not lowering them.
There are tow reasons why a hotter running engine have better thermal efficiency. The first is that coolant temp around the cylinder liners and cyl head is the driving force for heat transfer from the combustion gas. The hotter the coolant, the less heat transfer, which means more energy stays in the cylinder to produce power.
The second is, with the right fan strategy, the hotter coolant will allow higher heat transfer rates at the radiator, which will reduce the need for fan-on time. Colder coolant into the radiator requires more fan to drop it 15 degrees than hotter coolant.
there is also the fact that the engine oil will run hotter(within safe limits) which reduces cyl liner friction and the power required to pump it due to decreased viscosity. Oil temp is a large part in 2017 emission strategies, and should not be overlooked. Clearly you don't want to overtemp the oil when you are racing, as the cars on this site are meant to do, but if you're chasing down fuel mileage, it is a factor.
One thing to note is that my experience in the heavy duty diesel market. --we don't have to worry about detonation--. That being said, old SB chevy's and generally cars with cast iron or aluminum intakes used to have coolant run through them. Heat was easily transferred to the air as it passed through the runners, so it made sense that cold coolant would transfer less heat and have less risk of detonation. I don't think this applies to our engines much anymore since coolant doesn't circulate around the manifold, plus they're made of composite materials, so their running temps are much lower.
If you're chasing down everylast mpg, try the factory tstat with a matching fan strategy. I put some thoughts below on the topic if your interested. However, I don't think it would be responsible for an 8 mpg drop on the highway, I would log your 02 readings while steady state on the highway-I use Torque Pro with my android and a 15$ OBDII bluetooth connector I got off ebay.
Feel free to ask any questions if I can help. Here are my thoughts based on my experience as a cooling sytem engineer.
The best thermal efficiency will be had at the highest engine operating temperatures. For 2017 emissions targets(no longer NOx, but CO2 restraints which means better gas mileage), industry is looking at raising coolant temps even further--not lowering them.
There are tow reasons why a hotter running engine have better thermal efficiency. The first is that coolant temp around the cylinder liners and cyl head is the driving force for heat transfer from the combustion gas. The hotter the coolant, the less heat transfer, which means more energy stays in the cylinder to produce power.
The second is, with the right fan strategy, the hotter coolant will allow higher heat transfer rates at the radiator, which will reduce the need for fan-on time. Colder coolant into the radiator requires more fan to drop it 15 degrees than hotter coolant.
there is also the fact that the engine oil will run hotter(within safe limits) which reduces cyl liner friction and the power required to pump it due to decreased viscosity. Oil temp is a large part in 2017 emission strategies, and should not be overlooked. Clearly you don't want to overtemp the oil when you are racing, as the cars on this site are meant to do, but if you're chasing down fuel mileage, it is a factor.
One thing to note is that my experience in the heavy duty diesel market. --we don't have to worry about detonation--. That being said, old SB chevy's and generally cars with cast iron or aluminum intakes used to have coolant run through them. Heat was easily transferred to the air as it passed through the runners, so it made sense that cold coolant would transfer less heat and have less risk of detonation. I don't think this applies to our engines much anymore since coolant doesn't circulate around the manifold, plus they're made of composite materials, so their running temps are much lower.
10-15-2012, 08:55 AM
#5
I seem to remember a post where someone had an issue with a low thermostat setting caused their engine to go into the cold start mode. That would be equivalent to running with the choke on. That would most definitely affect your mileage.
I'm no FI guy so hopefully someone more knowledgeable will contribute.
A cold start issue seems like something your "tuner" could have programed out. Might want to check with him.
What do your plugs look like? Any other evidence of running too rich? Don't overlook other possiblities, like a stuck injector or fuel leak.
I'm no FI guy so hopefully someone more knowledgeable will contribute.
A cold start issue seems like something your "tuner" could have programed out. Might want to check with him.
What do your plugs look like? Any other evidence of running too rich? Don't overlook other possiblities, like a stuck injector or fuel leak.
