Diablosport Forums

http://www.ls1gto.com/forums/showthread ... ost2520397

Hey Johan (I know Mike doesn't know; he graciously referred me to 'GM engineers' ), please take a look at post #13 on the above thread. Seems like a genuine GM document, and it's at complete odds with the % tables on the Predator. Only the Corvette seems to use that table since it does have a variable-speed fan (only one), but the GTO apparently has a 2-speed setup (as explained there), so my 2 questions are:

- How the heck do percentages relate to a 2-speed fan setup?? Does 1-49% means 'low', and 50-99 high?

- And more importantly, there seems to be a myriad of variables that affect fan operation, with ECT (coolant temp) being only one. Seems to me that even 'ramping up' the % would do squat to turn them on sooner, unless maybe jumping above 50%, no? Hope to get some educated answers. Thanks.
JC

That info is from GM's SI(service information) web site.
It appears that the stage two operation only applies if there are extreme engine temps or there is a fault in the cooling system, kind of like a safe guard.
I do not think the % adjustment reflects the stage 1 and stage 2 settings.
There are quite a few tables that dictate fan speed, but to be honest the one vs ECT is the most vital one as it is directly related to your ECT where as the others are vs. AC pressure, trans temp, engine oil temp etc etc.

johan wrote:I do not think the % adjustment reflects the stage 1 and stage 2 settings.

I'm all confused after carefully reading all the information on that thread. Let's talk specifics, but before that, anybody reading this should have read the linked thread above to fully understand how the fans work on our GTOs and SSRs (2 fans). The '%' tables on the U7191 Predator seem to apply only to the Vette, which is the only LS2 vehicle with a variable-speed fan.

Here are the specific temps on fan operation on LS2 GTOs, excluding A/C inputs:

STAGE 1 (6V) - Fans ON at 208ºF and OFF at 203ºF

STAGE 2 (12V) - ON at 226ºF and back to Stage 1 at 216ºF

FANS OFF above 65 mph (regardless of A/C inputs, by the way).

One other interesting (and relevant) piece of information: HPTuners have tables (like the Predator) for the Vette, BUT specific ON/OFF temperature inputs for stages 1 and 2 for GTOs and SSRs. Hmmmmm.


Now to the million dollar questions:

- How can % (% of full power) tables meant for the variable-speed fan on LS2 Vettes can translate to alter stages 1 and 2 fan operation on our GTOs??

- How is our ECU interpreting those (%) numbers when it just needs an ON/OFF temp for each stage? A specific example would be nice.

With the collective knowledge here, hopefully I can get some answers. Thanks to all.
JC