due to ratio, i dont think truck power steering works as hard as you think.
you throw manual rack or just tie the lines together on a truck and it's alright, but on a lot of cars you can barely steer the damn thing.
even so, my f-body has TONS of load on the power steering pump, and it wont even bounce the tach when i crank the wheel with a flat tire or whatever, so i dont get it either.
steveo has a good point I never thought of... but Trucks usually have enough motor that it does not matter.
Cars on the other hand have less motor and the PS cramp is noticed, turn wheel while sitting still and motor load increases and RPM may decrease with just IAC Idle logic. Anything noticed is worked on so customers buying cars have no bad feedback from car. It's all about sales.
The logic behind tuning PS cramp, AC on, or even fans on is to keep idle same. Not to increase and do not let decrease idle RPM when system, like PS is put under load.
Years ago I played with the AC RPM on my Suburban and realized first hand why when AC comes on you just want idle stable, not an increase.... I was at a traffic light and stopped, AC came on and truck started to creep away into car in front of me! I had to apply more brake to compensate.
Now on my newer PCM truck, 98 with 0411 swap I have idle tables for In Drive and Park/Neutral. So while in P/N I do raise RPM when AC comes on. Keeps alternator charging better, oil pressure higher, coolant flowing better and most importantly AC stays colder!
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
it all seems unnecessary to me, but that's nothing.
my last 80s mazda 4 banger (and this thing had as much torque as a 305 chevy, it was a really stout little 2.2l motor) was a hybrid fi system, it was port fuel injected, it had a full on long runner high pressure multiport fuel system with a bigass monoblade throttle body. but it had a vac advance distributor......
anyway this thing had a bank of a half dozen vacuum solenoids and sensors mounted on the firewall, with all these crazy vacuum lines going everywhere, with tees, check valves, hard lines, totally nuts. probably 20 feet of vac line.
this crazy squid-looking device was linked to every damn system either electrically or pneumatically.. steering, hvac, distributor, egr, a/c, headlights, whatever. there were at least 6 vac lines running just to the throttle body for both pre and post throttle plate air control.
anyway i only found out when i started having issues with it, that the entire point of this system was to stabilize idle by allowing extra bypass air when an accessory of any kind, either electrical or parasitic on the rotating assembly, was turned on.
each solenoid even had a knob on it to adjust the amount of air that was added for each accessory bank. you could tune this thing so it would respond to the defroster being turned on by raising idle 1000 rpm, or not at all.
the funniest part is it had computer controlled IAC too, so all this stuff was totally unnecessary, if they just would have put some damn contact switches in place.
crazy stuff....
One of the reasons I dug into the XDF for the 7060 is the "Initial IAC counts added when A/C turned on", the factory had it set at 15, which was enough to make the RPM surge higher when the A/C kicked on. I changed it to 10, kept the max/min counts added the same and now it cycles with zero effect.
94 Blazer, Turbo'd 350 TBI - DD
1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
2012 Porsche Panamera Turbo - Date night car :)
1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac
Thanks for the info guys. I just tried stalling it moving it out and back into my garage and it didn't die. And i doubt i'll be in a situation where i'll be braking hard while turning. I'll have to test again once i add a/c.
Now I have to relocate my coolant temp sensor, because i just realized it's making me run rich until the thermostat opens since i got lazy and stuck it in the therostat housing along with my temp sensor which i also need to relocate...
seeing as my 1992 Camaro has one I can say it does do something. I have tried it with and with out. very little but it does do something. would actually like to have something compensate for my electric fan coming on more.
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