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2002 chevy trailblazer_lt
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Is the flexalite 292 a direct bolt on for the I-6?
It's a direct bolt on, as flex-alite sells a bracket kit with instructions for many gm truck also, when pruchasing from them they ask you what truck you have, but the price from teh flex-alite site is a ripoff you can find those fans for just under 300$ if you look hard enough
 

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2002 chevy trailblazer_lt
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Hmmmm. My problem was not with the PCMforless controller. It was with the airflow from the fan kit I bought off Ebay that they recommended. But given the demonstrated overheating I got, with good engineering data, the conclusion was obvious.

The factory EV fan, at 2000 or so fan RPM, using the factory shroud that covered the entire radiator, was pulling adequate cooling air and the LS1 fans with their smaller shroud wasn't. I was going to do more work to try sealing the edges of the LS1 shroud to prevent that sneak path for bypass air, but I concluded it wouldn't make enough of a difference to matter. The LS1 fans already pulled enough air through the radiator to suck paper very tightly to the front of the rad, but their CFM just wasn't up to it.

SO it's critical to match the fans and shroud to our exact radiator. If the flexalite 292 is that kit, then that's what I'd try next. Except I'm between jobs now, and living on savings, so the $500 price of the flexalite 292 is not an investment I'm able to make right now.

To duplicate my conditions of desert offroading, it should be easy if a tester has access to a heavy trailer (4000-5000 pounds) and some steep mountains with 5-6% grades. What was overheating me was 10-15 minutes of 80-100% throttle, 4LO range, 3-6 MPH ground speed (so there was little forced airflow - all the fan), in 85-90 degree ambient.

I need to sell the LS1 fan kit I bought for the PCMforless experiment, but I'm sorry I'm not in a position to invest in the flexalite 292 if I'm going to be stuck with it later. The biggest advantage for offroaders isn't the HP gain from efans, but the ability to turn the fan off for deep water crossings (>20"). Since those water crossings also mean you need to extend your vent tubes, and you're likely to take water in through your door sills, there are only a half dozen of us crazy enough to be in that market for pure functionality.

There are indeed offroaders who would invest in efans for the "gadget value" of them, and I used to be one of those folks. But not right now, and not for the foreseeable future.

If anybody could show good experimental data of the factory fan CFM versus flexalite 292, it would go a long way to convince me it would work. I didn't do that research for the LS1 kit, or insist that somebody else provide the data. I just trusted the vendor that the LS1 fans were "overkill" for the application, which turned out to be a claim made without data. As an old boss once said: "In God we trust ... all others bring data." :yes:

I do have the time and inclination to test the kit, but given that I got burned (literally) with the PCMforless evaluation because of their inadequate testing, I'm just not able to do it if it costs me $500, even if the controller was no-charge. But PCMforless solicited for testers on the basis of who replied fastest, I think. Of course people are going to volunteer for free stuff - but the testing wasn't very rigorous, wasn't done using EFILive data capture, and wasn't done in stressful conditions - all of which contributed to the project's downfall. I'm experienced in new product launches, but efans depend so much on the combination of fan kit plus the controller that it's a real challenge to succeed. The vendor has to control both parts of the system, not just one side. I don't have a solution to that.

What other fan kits are being considered besides the flexalite 292?
On my part i have done testing with numerous other shrouds, my favorite so fas is the dodge stratus one, it's bigger in size to the ls1/lt1 one, both fans are equally placed, but they are expensive, and are dual speed, but mecanicaly wise they are better than the ls1, just the way the blades are placed tells a lot, i had good results doing some "stupid" test in my hallway at home, I was entertaining my friends kid and i placed teh fan at one end and would put paper balls to se which one would push it faster and farther, the stratus fans were obviously more powerfull, but they draw a lot of juice, anyhow IMHO someone like you Roadie, would probablty benefit more from the 292 than an LS1./LT1 shroud, as for the average joe i really beleive the ls1/lt1 shroud is more than enough,
 

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2003 gmc envoy_slt_xl
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A couple of years back, there was a vendor that sold an all aluminum radiator with a big fan on it. Does anybody remember that? I think a guy with a white TBSS had it on his. He may have had a 427ci LS2 in it. That radiator and fan setup seems like the most durable cooling setup.:undecided:m2:
 

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2002 chevy trailblazer_lt
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A couple of years back, there was a vendor that sold an all aluminum radiator with a big fan on it. Does anybody remember that? I think a guy with a white TBSS had it on his. He may have had a 427ci LS2 in it. That radiator and fan setup seems like the most durable cooling setup.:undecided:m2:
That was for the trailblazer SS,it uses a C-6 Z06 fan, i have not used that one, but i wonder if that one could also be used with good results
 

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Discussion Starter · #26 ·
I've been exchanging PM's with another member that is looking at running the C6 fan. I'd like to see how much air that fan can move, as it sounds like an excellent way to go...
 

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I've been exchanging PM's with another member that is looking at running the C6 fan. I'd like to see how much air that fan can move, as it sounds like an excellent way to go...
Just keep in mind, if you do use the fan with the flex-alite controller, the wiring must be made so that the fan is always at "high" speed,

If not you can use that fan with a different setup, PM me for the schematics
 

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2007 chevy trailblazer_ls
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I've been exchanging PM's with another member that is looking at running the C6 fan. I'd like to see how much air that fan can move, as it sounds like an excellent way to go...
That would be me. The C6 fan is a pwm (pulse width modulated) fan. Its' speed varies from 0-100% based on what signal the ecm sends. The fan is about 16.5 inches in diameter- pretty close to the TB's ev fan. Unfortuneatley, I haven't figured out how to get the I6 pcm to communicate with the fan module to make the fan work. I have a few engineering contacts at GM, but as we all know the TB is no longer made, those engineers have been re-assigned to other platforms. I'm trying to track them down.

I'm sure it's possible that the C6 fan could be used without the pwm module and regulated by the Flex-a-lite controller, but I'm trying to get the C6 fan to work as designed with the I6 pcm. This may not be doable due too how the I6 pcm controls the stock ev fan.

Mark
 

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2004 gmc
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I would guess that the fundamental frequency of the EV fan's PWM would be different (probably lower due to the response bandwidth being lower) from a fully electric fan. But I loaned out my scope to my son-in-law and can't check it right now. I can imagine a controller that just integrated the I6 PCM's control, turned it into an analog level, then converted it back to a PWM at the C6 fan's rep rate. The trailvoy EV fan has a Hall Effect RPM feedback as well to keep the PCM happy. Does the C6 also have feedback?
 

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2007 chevy trailblazer_ls
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Here is the shop manual description for each vehicle.

Trailblazer:

Cooling Fan Description and Operation
Cooling Fan Control
The purpose of the electro-viscous (EV) fan clutch is to maintain powertrain cooling requirements. The control module monitors the following sensors to regulate the fan speed:

• Engine coolant temperature sensor

• A/C refrigerant pressure sensor

• Vehicle speed sensor

• Intake air temperature sensor

• Transmission fluid temperature sensor

• Ambient air temperature sensor

The control module controls the electro-viscous fan clutch engagement. The control module regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.

The fan has the ability to create a feedback signal, so the control module has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch. The control module supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.

The control module commands the cooling fan to 100 percent under the following conditions:

• Engine coolant temperature exceeds approximately 129°C (264°F).

• The transmission oil temperature exceeds approximately 151°C (304°F).

• A/C refrigerant pressure exceeds 1655 kPa (240 psi).

• When certain DTCs set--These include P0116, P0117, P0118, P0125, P1481, P1482, and P1484.

The scan tool can engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100 percent command with the engine at 2,000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine at 2000 RPM. The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.

Under certain conditions the cooling fan may be engaged at engine restart. They are as follows:

• The cooling fan was engaged at the time the engine was turned OFF.

• The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan.

Although the fan is commanded OFF at this time due to a cold start condition, this is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.


Corvette:

Cooling System Description and Operation
Cooling Fan Control - Variable Speed Single Fan System
The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the cooling fan motor in relation to the pulse width modulated signal.

Cooling fan speed is effected by many different conditions and can be adjusted from 10% to 90% duty cycle (PWM), 90% is considered high speed fan. When multiple cooling fan speed requests are received the ECM uses the highest cooling fan speed of all the requests. The ECM commands the cooling fan ON under the following conditions:

• Cooling fan duty cycle starts when engine coolant temperature reaches approximately 95°C (204°F) and reaches high speed at temperatures above 113°C (235°F).

• Cooling fan duty cycle starts when A/C pressure reaches approximately 1100 kPa (160 psi) and reaches high speed at A/C pressures above 2480 kPa (360 psi).

• At engine oil temperatures above approximately 150°C (302°F) the cooling fan duty cycle will be commanded to high speed.

• At transmission oil temperatures above approximately 132°C (270°F) the cooling fan duty cycle will be commanded to high speed.

• After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 113°C (235°F) or the A/C pressure is greater than 1720 kPa (249 psi) the cooling fan duty cycle is set to 50%, low speed. If the coolant temperature drops below 110°C (230°F) and the A/C pressure drops below 1660 kPa (241 psi) the fan will shut OFF. The fans will automatically shut OFF after 2 min. regardless of coolant temperature


Looking at the schematics, the Corvette ecm toggles the ground to the fan control module allowing the fan to rotate (I assume) at a speed based on the amount of time the module is grounded based on sensor inputs. The Trailblazer pulses 12 volts to the fan relay to allow fan rotation (again I'm assuming) based on sensor inputs and a fan speed signal sent back to the pcm. There is not a hall effect switch shown for the C6 fan schematic. It does show one for the TB fan.
What's confusing to me is looking at the Trailblazer schematic and comparing to the cooling fan operation description, it looks like they are different. The schematic shows the ecm grounding the fan relay, but the description says it supplies a pwm 12 volts to the relay. The schematic shows no source for 12 volts to energize the relay, so I think GM used a ground symbol instead of using 12 volt symbol at that point. The schematic also doesn't differentiate between the 4.2l, 5.3l, or 6.0l engines other than the pin number for the ecm /pcm connector. I know the V8 ecm is different from the I6 pcm which is why the TBSS C5 and C6 fans won't work in an I6 application, but the shop manual does not show a difference in how the ev fan is wired for the differnet engines.

I can't post the schematics here, but if anyone would like them, I'll send them to you. PM me with your email address.
 

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2002 chevy trailblazer_lt
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Here is the shop manual description for each vehicle.

Trailblazer:

Cooling Fan Description and Operation
Cooling Fan Control
The purpose of the electro-viscous (EV) fan clutch is to maintain powertrain cooling requirements. The control module monitors the following sensors to regulate the fan speed:

• Engine coolant temperature sensor

• A/C refrigerant pressure sensor

• Vehicle speed sensor

• Intake air temperature sensor

• Transmission fluid temperature sensor

• Ambient air temperature sensor

The control module controls the electro-viscous fan clutch engagement. The control module regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.

The fan has the ability to create a feedback signal, so the control module has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch. The control module supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.

The control module commands the cooling fan to 100 percent under the following conditions:

• Engine coolant temperature exceeds approximately 129°C (264°F).

• The transmission oil temperature exceeds approximately 151°C (304°F).

• A/C refrigerant pressure exceeds 1655 kPa (240 psi).

• When certain DTCs set--These include P0116, P0117, P0118, P0125, P1481, P1482, and P1484.

The scan tool can engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100 percent command with the engine at 2,000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine at 2000 RPM. The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.

Under certain conditions the cooling fan may be engaged at engine restart. They are as follows:

• The cooling fan was engaged at the time the engine was turned OFF.

• The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan.

Although the fan is commanded OFF at this time due to a cold start condition, this is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.


Corvette:

Cooling System Description and Operation
Cooling Fan Control - Variable Speed Single Fan System
The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the cooling fan motor in relation to the pulse width modulated signal.

Cooling fan speed is effected by many different conditions and can be adjusted from 10% to 90% duty cycle (PWM), 90% is considered high speed fan. When multiple cooling fan speed requests are received the ECM uses the highest cooling fan speed of all the requests. The ECM commands the cooling fan ON under the following conditions:

• Cooling fan duty cycle starts when engine coolant temperature reaches approximately 95°C (204°F) and reaches high speed at temperatures above 113°C (235°F).

• Cooling fan duty cycle starts when A/C pressure reaches approximately 1100 kPa (160 psi) and reaches high speed at A/C pressures above 2480 kPa (360 psi).

• At engine oil temperatures above approximately 150°C (302°F) the cooling fan duty cycle will be commanded to high speed.

• At transmission oil temperatures above approximately 132°C (270°F) the cooling fan duty cycle will be commanded to high speed.

• After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 113°C (235°F) or the A/C pressure is greater than 1720 kPa (249 psi) the cooling fan duty cycle is set to 50%, low speed. If the coolant temperature drops below 110°C (230°F) and the A/C pressure drops below 1660 kPa (241 psi) the fan will shut OFF. The fans will automatically shut OFF after 2 min. regardless of coolant temperature


Looking at the schematics, the Corvette ecm toggles the ground to the fan control module allowing the fan to rotate (I assume) at a speed based on the amount of time the module is grounded based on sensor inputs. The Trailblazer pulses 12 volts to the fan relay to allow fan rotation (again I'm assuming) based on sensor inputs and a fan speed signal sent back to the pcm. There is not a hall effect switch shown for the C6 fan schematic. It does show one for the TB fan.
What's confusing to me is looking at the Trailblazer schematic and comparing to the cooling fan operation description, it looks like they are different. The schematic shows the ecm grounding the fan relay, but the description says it supplies a pwm 12 volts to the relay. The schematic shows no source for 12 volts to energize the relay, so I think GM used a ground symbol instead of using 12 volt symbol at that point. The schematic also doesn't differentiate between the 4.2l, 5.3l, or 6.0l engines other than the pin number for the ecm /pcm connector. I know the V8 ecm is different from the I6 pcm which is why the TBSS C5 and C6 fans won't work in an I6 application, but the shop manual does not show a difference in how the ev fan is wired for the differnet engines.

I can't post the schematics here, but if anyone would like them, I'll send them to you. PM me with your email address.


I would like those, please, but that's odd, why do i have the c06 fan under dual speed fan ? there are some people in other forums using that fan as we speak with a regular t-stat that's attached to an on/off relay

could it be that there's two fans ?
 

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2007 chevy trailblazer_ls
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I would like those, please, but that's odd, why do i have the c06 fan under dual speed fan ? there are some people in other forums using that fan as we speak with a regular t-stat that's attached to an on/off relay

could it be that there's two fans ?
I'm sure the C6 fan could be used without the pwm module. It's just a two wire fan motor. I'm trying to maintain the variable speed feature as opposed to just being on or off that a relay would do or the 60-100% speed the Flexalite module allows. I need your email address to send it to you.
 

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2002 chevy trailblazer_lt
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899 Posts
I'm sure the C6 fan could be used without the pwm module. It's just a two wire fan motor. I'm trying to maintain the variable speed feature as opposed to just being on or off that a relay would do or the 60-100% speed the Flexalite module allows. I need your email address to send it to you.
[email protected]

It's weird because teh schematics i've found of teh c6 fan is a 3 connector fan with (12v low gnd and 12v high)

i'll take a look
 

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2007 chevy trailblazer_ls
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[email protected]

It's weird because teh schematics i've found of teh c6 fan is a 3 connector fan with (12v low gnd and 12v high)

i'll take a look
Correct, three wires. Battery positive voltage, ground, and cooling fan speed control. This is the 12 volts that is pwm to the fan control module from the ecm.

email sent
 

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2004 chevy trailblazer_lt
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143 Posts
Glad to see someone working on electric fans for the I6. I definately am up for getting rid of that EV fan. Thanks guys :woot:
 

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2004 chevy trailblazer_lt
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143 Posts
hey guys just curious which fan you may go with...plus wanted to keep the thread alive :thx
 
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