Quote:
Originally Posted by parsonsj
I'm glad I started reading this thread! Very very interesting, and far superior to what I did on my last project which was to use a relay to override and run the fans with pressure monitoring via a trinary switch.
Just to clarify (for me, anyway  ) : the E67 in the LSA crate motor offering from GM (pn 19259293) can monitor the A/C line pressure and turn on the fans? Does it do that with PWM support (just running the fan enough to keep the high side pressure to certain number)? Or does it do that by running the fans full speed until the high side pressure drops below a threshold?
And all the while, it's keeping track of the coolant temp and running the fans appropriately for that too?
Sweet! |
We are still trying to figure out how to handle integrating the Vintage A/C system cooling fan requirements into our overall cooling strategy. This is like that Whack-a-Mole game. Every time you think you have a handle on how to make everything place nice together something else pops up.
Oh well, that's what makes it fun right????
First let me remind you that today I am just a newbie trying to figure this all out for the first time. Dave, who thankfully has chimed in on this thread, has numerous successful installs under his belt including Stielow's latest cars so he is MUCH more credible than me. Bottom line, don't follow my lead until you see the final results. I will keep you posted as we learn.
Kevin and Trevor of V8TV are keeping me honest and out of trouble too.
Getting back to your questions about how the ECM requests cooling fan speeds and how we hope to integrate the Vintage Air system into our cooling fan strategy:
Here is what I have been able to find regarding how GM sets up the cooling strategy in the ECM for PWM control of cooling fans:
Engine coolant temp. strategy:
Cooling fan starts at approx. 204 Deg. F (at 10% duty cycle) and steadily increases with temp up to a max of 90% duty cycle (which they consider full on or high speed) at 235 Deg. F and higher.
A/C Pressure strategy:
Cooling fan starts when A/C pressure is approx. 160 psi and reaches high speed at 360 psi.
Engine Oil temp strategy:
Oil temps above approx. 302 Deg. F will trigger high speed fan on.
Transmission Oil temp strategy:
Trans oil temps above 270 Deg. F will trigger high speed fan on.
Vehicle shut off strategy:
If engine coolant temp at key off is greater than 235 Deg. F or the A/C pressure is greater than 249 psi, the cooling fan duty cycle is set to 50%. If the coolant temp drops below 230 Deg. F, and the A/C pressure drops below 241 psi, the fan will shut off. Otherwise, the fan will automatically shut off after 2 minutes regardless of temperatures.
When multiple cooling fan requests are received the ECM uses the highest cooling fan speed of all requests.
Now, according to Vintage Air,
We need to find out if the fan algorithms can be tuned to request full speed fans at 260 PSI instead of the GM setting of 360 PSI because if pressure in the Vintage Air system is allowed to go much higher than 275 psi, the ability of the system to absorb heat is greatly reduced.
Absent of that, they would be concerned that we will not have efficient cooling because the GM A/C strategy is designed for a fixed orifice tube expansion with a variable displacement compressor, as opposed to the thermostatic expansion valve system Vintage Air employs.
The Vintage air system does have an on/off cooling fan control. It calls for fans on at 254 psi and has a safety shutoff for the system at 406 psi in case there is a fan failure or a blockage develops in the system.
This means we need to check into a few things as follows:
1. We need to make sure that we can turn off the ECM algorithms for any temperature sensors we might not use without causing the ECM to get confused or angry with us. For instance, we do not presently plan to sense the trans. temp or the oil temp through the ECM even if those algorithms reside in our version of the E67 ECM. We only want to "turn on" the coolant and the A/C pressure algorithms that we believe/hope to be resident in the LSA crate motor E67 controller but "turned off".
2. We need to make sure we can reset or tune the A/C pressure settings to emulate the way the Vintage A/C system controls cooling fans.
3. We need to verify that we install the GM A/C pressure sensor in the correct location within the refrigeration circuit.
4. We need to think the whole strategy through again to see what we might be missing.
Of course, we may still need to fall back to a more conventional cooling fan strategy if this all proves undoable for some reason. It's always good to have a Plan B.