2003 Suburban 5.3l close to overheating when towing
August 12th, 2020, 12:06 PM
#11
Just asking the question, as I have no experience with E-fans....
I know the alleged "benefit" of e-fans is their infinitely variable speed and potential for mileage savings, but I also understand that their ability to move maximum air is their one weakness. In other words, if you do a lot of heavy towing, you don't want e-fans. I also have a little experience with this through my day job, as one of my larger customers makes fan clutches for cars and light trucks, and while the big three flirted with e-fans for a while, most have gone back to belt-driven on their HD trucks.
Could it simply be a matter of not enough air being moved? The engineering geek in me questions the efficiency of converting mechanical energy (engine cranshaft) to electrical energy (alternator) and back to mechanical energy (e-fan). Seems a bit silly, and rife with parasitic losses. I'd be willing to wager a mechanical fan attached to a crankshaft spinning 4200 RPM is going to be able to move a lot more air than an electric fan.
I know the alleged "benefit" of e-fans is their infinitely variable speed and potential for mileage savings, but I also understand that their ability to move maximum air is their one weakness. In other words, if you do a lot of heavy towing, you don't want e-fans. I also have a little experience with this through my day job, as one of my larger customers makes fan clutches for cars and light trucks, and while the big three flirted with e-fans for a while, most have gone back to belt-driven on their HD trucks.
Could it simply be a matter of not enough air being moved? The engineering geek in me questions the efficiency of converting mechanical energy (engine cranshaft) to electrical energy (alternator) and back to mechanical energy (e-fan). Seems a bit silly, and rife with parasitic losses. I'd be willing to wager a mechanical fan attached to a crankshaft spinning 4200 RPM is going to be able to move a lot more air than an electric fan.
August 12th, 2020, 1:31 PM
#12
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Just asking the question, as I have no experience with E-fans....
I know the alleged "benefit" of e-fans is their infinitely variable speed and potential for mileage savings, but I also understand that their ability to move maximum air is their one weakness. In other words, if you do a lot of heavy towing, you don't want e-fans. I also have a little experience with this through my day job, as one of my larger customers makes fan clutches for cars and light trucks, and while the big three flirted with e-fans for a while, most have gone back to belt-driven on their HD trucks.
Could it simply be a matter of not enough air being moved? The engineering geek in me questions the efficiency of converting mechanical energy (engine cranshaft) to electrical energy (alternator) and back to mechanical energy (e-fan). Seems a bit silly, and rife with parasitic losses. I'd be willing to wager a mechanical fan attached to a crankshaft spinning 4200 RPM is going to be able to move a lot more air than an electric fan.
I know the alleged "benefit" of e-fans is their infinitely variable speed and potential for mileage savings, but I also understand that their ability to move maximum air is their one weakness. In other words, if you do a lot of heavy towing, you don't want e-fans. I also have a little experience with this through my day job, as one of my larger customers makes fan clutches for cars and light trucks, and while the big three flirted with e-fans for a while, most have gone back to belt-driven on their HD trucks.
Could it simply be a matter of not enough air being moved? The engineering geek in me questions the efficiency of converting mechanical energy (engine cranshaft) to electrical energy (alternator) and back to mechanical energy (e-fan). Seems a bit silly, and rife with parasitic losses. I'd be willing to wager a mechanical fan attached to a crankshaft spinning 4200 RPM is going to be able to move a lot more air than an electric fan.
They are set to turn off no matter what the coolant temp is at a certain speed. Some set it up at around 45mph. My guy just tuned the car yesterday and he set it at 70mph which I think is too high actually. A 45mph wind through the motor is more than those fans can send through if they were on. Its the same with a clutch fan as well. It slows down as the car gains speed so whether E-Fan or clutch fan, they arent moving air when the car is going over a certain speed so the E-Fan is preferred for mileage purposes as you state as well as the customization you can give it with a tune.
I got my car re-tuned because I was worried that the first tune I received, a mail in tune from BlackBear Performance was not right and was overheating the car while towing. Low and behold this is most likely the issue. The mail in tune I received was more for a hot rod car with a super big CAM and not my lumbering Suburban with larger tires that is trying to tow 5000+ lbs. BlackBear Performance had the advance set at something like 28Deg! My local tuner when he put the car on the Dyno yesterday brought it all the way down to 18Deg. He said I was super lucky I did not blow a head gasket or worse while towing up over Donner Summit as the advance was making it ping like crazy. It went to 250deg and I had to pull over. I am glad I did...
Anyways, a big NO VOTE for any mail in tune for your car. Shame on BlackBear Performance for sending me what was likely just a canned tune from the 100's of LS motors they have tuned. You should always put it on a Dyno! Could have blown my motor easily.
Last edited by Levahj; August 12th, 2020 at 1:33 PM.
August 13th, 2020, 7:28 AM
#14
The Chevy E-Fan system in the 2005-2006 trucks (and probably the next model years as well but not 100% sure) is a double fan setup and has two grounded inputs from the ECU that engage them. One of the grounds engages the slower speed where the fans are wired in series, therefore halving the 12 volts from the battery and halving the speed of each. And when both grounds are initiated by the ECU, they both receive full voltage from the battery ( through a set of relays) and both go into full speed mode. Its a lot of air in full speed mode. The ECU turns them on (and off) based upon a number of variables the biggest being coolant temp, of course. Also AC pressure as you want to the fans to run if the AC is on.
They are set to turn off no matter what the coolant temp is at a certain speed. Some set it up at around 45mph. My guy just tuned the car yesterday and he set it at 70mph which I think is too high actually. A 45mph wind through the motor is more than those fans can send through if they were on. Its the same with a clutch fan as well. It slows down as the car gains speed so whether E-Fan or clutch fan, they arent moving air when the car is going over a certain speed so the E-Fan is preferred for mileage purposes as you state as well as the customization you can give it with a tune.
I got my car re-tuned because I was worried that the first tune I received, a mail in tune from BlackBear Performance was not right and was overheating the car while towing. Low and behold this is most likely the issue. The mail in tune I received was more for a hot rod car with a super big CAM and not my lumbering Suburban with larger tires that is trying to tow 5000+ lbs. BlackBear Performance had the advance set at something like 28Deg! My local tuner when he put the car on the Dyno yesterday brought it all the way down to 18Deg. He said I was super lucky I did not blow a head gasket or worse while towing up over Donner Summit as the advance was making it ping like crazy. It went to 250deg and I had to pull over. I am glad I did...
Anyways, a big NO VOTE for any mail in tune for your car. Shame on BlackBear Performance for sending me what was likely just a canned tune from the 100's of LS motors they have tuned. You should always put it on a Dyno! Could have blown my motor easily.
They are set to turn off no matter what the coolant temp is at a certain speed. Some set it up at around 45mph. My guy just tuned the car yesterday and he set it at 70mph which I think is too high actually. A 45mph wind through the motor is more than those fans can send through if they were on. Its the same with a clutch fan as well. It slows down as the car gains speed so whether E-Fan or clutch fan, they arent moving air when the car is going over a certain speed so the E-Fan is preferred for mileage purposes as you state as well as the customization you can give it with a tune.
I got my car re-tuned because I was worried that the first tune I received, a mail in tune from BlackBear Performance was not right and was overheating the car while towing. Low and behold this is most likely the issue. The mail in tune I received was more for a hot rod car with a super big CAM and not my lumbering Suburban with larger tires that is trying to tow 5000+ lbs. BlackBear Performance had the advance set at something like 28Deg! My local tuner when he put the car on the Dyno yesterday brought it all the way down to 18Deg. He said I was super lucky I did not blow a head gasket or worse while towing up over Donner Summit as the advance was making it ping like crazy. It went to 250deg and I had to pull over. I am glad I did...
Anyways, a big NO VOTE for any mail in tune for your car. Shame on BlackBear Performance for sending me what was likely just a canned tune from the 100's of LS motors they have tuned. You should always put it on a Dyno! Could have blown my motor easily.
I also tow very heavy, with an 8600-lb trailer, into the Rockies on multiple occasions including the Eisenhower Tunnel (11,110') and Powder River Pass (9666').
Did you not test the first tune before you towed? Did you have different mapping set up for when you use Tow/Haul? I would think you'd have heard knock/ping in even just mildly spirited driving, much less towing.
This is the worst I've ever done - eastbound Eisenhower Tunnel approach on I-70. Probably the most difficult 8-mile stretch to tow in the country. The "Ike Gauntlet," if you ever watch TFL towing videos. I had the gas pedal floored for about 80% of that stretch. My weight was 16,200 lbs. Engine temp is only slightly elevated from normal:
Last edited by intheburbs; August 13th, 2020 at 7:31 AM.
August 13th, 2020, 8:32 AM
#15
The radiator looks brand spanking new out of that '03 at the junkyard. They must have just replaced it before the car was totaled and they want $50 so I am going to pull it out tomorrow and just replace mine for piece of mind. Especially since I just purchased this Suburban 6 months ago. Its in great shape but who knows why it is heating up when my other Suburban never did.
August 13th, 2020, 11:31 AM
#16
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Well, as you can see in my sig, I have a Blackbear EFI live tune in my Suburban 2500. Have had the truck for 7 years, and got it tuned pretty much right when I bought it. Seriously woke up my truck, and I'm completely satisfied with it.
I also tow very heavy, with an 8600-lb trailer, into the Rockies on multiple occasions including the Eisenhower Tunnel (11,110') and Powder River Pass (9666').
Did you not test the first tune before you towed? Did you have different mapping set up for when you use Tow/Haul? I would think you'd have heard knock/ping in even just mildly spirited driving, much less towing.
This is the worst I've ever done - eastbound Eisenhower Tunnel approach on I-70. Probably the most difficult 8-mile stretch to tow in the country. The "Ike Gauntlet," if you ever watch TFL towing videos. I had the gas pedal floored for about 80% of that stretch. My weight was 16,200 lbs. Engine temp is only slightly elevated from normal:
I also tow very heavy, with an 8600-lb trailer, into the Rockies on multiple occasions including the Eisenhower Tunnel (11,110') and Powder River Pass (9666').
Did you not test the first tune before you towed? Did you have different mapping set up for when you use Tow/Haul? I would think you'd have heard knock/ping in even just mildly spirited driving, much less towing.
This is the worst I've ever done - eastbound Eisenhower Tunnel approach on I-70. Probably the most difficult 8-mile stretch to tow in the country. The "Ike Gauntlet," if you ever watch TFL towing videos. I had the gas pedal floored for about 80% of that stretch. My weight was 16,200 lbs. Engine temp is only slightly elevated from normal:
I think I mentioned I had a stock 2002 suburban for 16 years before I got this 2003 Z71 so essentially the exact same truck. I cant remember the needle even hardly moving past 12 o"clock, even with towing in the mountains so I know the stock setup from Chevy is very solid heat dissipation wise. Was hoping with the cam, e-fan upgrade and cold air intake that I could squeeze out another 30HP or so. Nick at Newtech's thought is that I probably have but with the truck pinging so bad in the mountains the ECU probably pulled way back on the advance at some point, most likely pulling my power way below stock and making the truck feel worse than my stock 2002 setup.
That is the theory anyways... Wont know till I tow again up a good grade. Boat is in Tahoe now for the rest of the summer so we will have to wait and see...
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