Hot LS Motors Really Run Better?
05-11-2019, 05:24 PM
#1
Hot LS Motors Really Run Better? Years ago, I was on a dyno and the dyno operator made a comment that for some reason, LS1's seem to put down better numbers hot...not sure why...
I've got an LS6 swapped '98 Z28 and I wanted to throw this out there for some opinions. I've got a 180 degree thermostat installed and when I had it dynotuned by a VERY reputable shop, they programmed the fans to come on earlier with the 180 thermostat. I've also got an SLP fan switch installed with lights added to let me know when the fans come on (Did that LONG before the LS6 swap w/180 thermostat). Since I've got a '98, my temp gauge is also accurate.
My low speed fan seems to come on VERY regularly, like once the gauge hits the 1/8 temp marking and then then the 2nd fan kicks on right before the 1/4 temp marking (155?) and the car never gets above the 1/4 temp gauge marking.
Obviously, when at the track and racing, you turn everything off for the run. However, since the dynotune, at least one fan is always on when I'm at the track and there's no way to cut it off since that's how it was set. So my question is, is it wash that the car is cooler on the runs, but the fan is on while I'm going down the track vs. the fan not being on at all, but the motor is a little hotter? Am I really giving up any HP with the fans coming on so frequently? Should I have the fans programmed a little higher and switch them on manually while staging, but off for the run?
OR, does the alternator always have the same resistance with the belt/pulley and it makes no difference if I'm using more electrical power on a run. I realize the AC system has a clutch and needs to be off for a run, but is the alternator similar to the compressor clutch in that respect too?
Hope it's not a dumb question...but I am curious...
I've got an LS6 swapped '98 Z28 and I wanted to throw this out there for some opinions. I've got a 180 degree thermostat installed and when I had it dynotuned by a VERY reputable shop, they programmed the fans to come on earlier with the 180 thermostat. I've also got an SLP fan switch installed with lights added to let me know when the fans come on (Did that LONG before the LS6 swap w/180 thermostat). Since I've got a '98, my temp gauge is also accurate.
My low speed fan seems to come on VERY regularly, like once the gauge hits the 1/8 temp marking and then then the 2nd fan kicks on right before the 1/4 temp marking (155?) and the car never gets above the 1/4 temp gauge marking.
Obviously, when at the track and racing, you turn everything off for the run. However, since the dynotune, at least one fan is always on when I'm at the track and there's no way to cut it off since that's how it was set. So my question is, is it wash that the car is cooler on the runs, but the fan is on while I'm going down the track vs. the fan not being on at all, but the motor is a little hotter? Am I really giving up any HP with the fans coming on so frequently? Should I have the fans programmed a little higher and switch them on manually while staging, but off for the run?
OR, does the alternator always have the same resistance with the belt/pulley and it makes no difference if I'm using more electrical power on a run. I realize the AC system has a clutch and needs to be off for a run, but is the alternator similar to the compressor clutch in that respect too?
Hope it's not a dumb question...but I am curious...
05-11-2019, 08:27 PM
#2
ModSquad
iTrader: (6)
My experience with this subject is while my Chevelle was on the dyno at Vengeance, just before our last pull, Mike shut the car down and put a plastic blower fan actually up on the engine bay to blow cool air directly on the engine itself, as well as his huge pusher fans blowing massive air through my grille. He said to give it 15-20 minutes because cooler cars always dyno higher. Didn’t give it long enough to cool the oil down any, just coolant. I run a 160 thermostat btw.
There is a fine line here. Heat in the combustion chamber and around the chamber in the coolant is required for max efficiency. In my own experience with doing a lot of R&D as well as race stuff for cup shops back in the day, I know that if you build two identical engines, one with iron heads, and the other being aluminum heads, the iron headed engine will make more power because it keeps heat in the chambers longer. I know that for a fact. Saw it with my own disbelieving eyes.
There is a fine line here. Heat in the combustion chamber and around the chamber in the coolant is required for max efficiency. In my own experience with doing a lot of R&D as well as race stuff for cup shops back in the day, I know that if you build two identical engines, one with iron heads, and the other being aluminum heads, the iron headed engine will make more power because it keeps heat in the chambers longer. I know that for a fact. Saw it with my own disbelieving eyes.
05-13-2019, 02:30 AM
#3
LS1Tech Administrator
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I agree with Che70velle, the ideal combination is a hot combustion chamber and a cold intake air charge. The general reasoning behind colder t-stats is two-fold; to prevent intake heat soak by reducing engine bay temps thus promoting a cooler air intake charge, and/or to reduce the risk of detonation - especially with aggressive timing and a power adder. For these reasons temp reduction is good to a point, but the unintended consequence is that a colder combustion chamber is less efficient, so finding the right balance for a given application is key.
The LS1 is not prone to intake heat soak to the degree that some other engines are, so in an NA application where timing and A/F aren't at the ragged edge they tend to make better power/run better times at relatively higher engine temps. All of my LS1s have run their best times with coolant temps in the ~200-210°F range, all else being as equal as possible (I've heard others mention that as high as 215°F seems to be the sweet spot in their experience). Of course, there are some other factors involved in maximizing this balance, such as outside air induction.
As for your question regarding electrical load of the fans, I'm not sure how much impact that one accessory would have on power output via alternator load, but this would also depend on whether it's running at high or low speed.
The LS1 is not prone to intake heat soak to the degree that some other engines are, so in an NA application where timing and A/F aren't at the ragged edge they tend to make better power/run better times at relatively higher engine temps. All of my LS1s have run their best times with coolant temps in the ~200-210°F range, all else being as equal as possible (I've heard others mention that as high as 215°F seems to be the sweet spot in their experience). Of course, there are some other factors involved in maximizing this balance, such as outside air induction.
As for your question regarding electrical load of the fans, I'm not sure how much impact that one accessory would have on power output via alternator load, but this would also depend on whether it's running at high or low speed.
05-16-2019, 05:48 AM
#4
What they said.
Back in the 1950's & 1960's GM's did a lot of testing and iron engines made 10-20 more hp generally than aluminum due to being able to keep heat in the combustion chambers and better ring seal. The ring seal issue is solved with today's iron liner aluminum blocks vs an all aluminum block but the hot chamber factor remains.
Key from what I read...
Cold air, Cool coolant, warm oil & hot chambers
Back in the 1950's & 1960's GM's did a lot of testing and iron engines made 10-20 more hp generally than aluminum due to being able to keep heat in the combustion chambers and better ring seal. The ring seal issue is solved with today's iron liner aluminum blocks vs an all aluminum block but the hot chamber factor remains.
Key from what I read...
Cold air, Cool coolant, warm oil & hot chambers