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View Full Version : closed loop....please explain

streetrod93
07-15-2005, 10:48 PM
i've heard this term a few times during the past couple weeks and am not for sure what it means... can someone please explain
Fastbird
07-15-2005, 10:53 PM
Open Loop = when the car just starts up, the oxygen sensors are not warm enough to give proper feedback, so the computer relies basically on the VE tables alone for fueling.

Closed Loop = Engine is up to operating temperature and the computer is using inputs and feedback from the various sensors to make fueling calculations.
streetrod93
07-15-2005, 11:31 PM
on the dyno, the guy doing my tuning said that the car never would go closed loop.... i was thinking, with long tube headers, do you think going to the 94+ 4 wire heated o2s would make a difference?
Fastbird
07-15-2005, 11:49 PM
on the dyno, the guy doing my tuning said that the car never would go closed loop.... i was thinking, with long tube headers, do you think going to the 94+ 4 wire heated o2s would make a difference?

On one word....HELLYES!!!

I was having trouble at idle situations of my ASM equipped car bouncing into open loop for no reason. A Swap to the 94+ 4 wire O2's and all is good.
streetrod93
07-16-2005, 07:11 PM
what can not going to closed loop affect. during my tuning on the dyno, he said that the car never went to closed loop. the car didn't dyno what i thought it should either. do you think that this might have had something to do with it?
Fastbird
07-16-2005, 08:33 PM
what can not going to closed loop affect. during my tuning on the dyno, he said that the car never went to closed loop. the car didn't dyno what i thought it should either. do you think that this might have had something to do with it?

It can definitely affect power depending on how far off the base tune is. Basically in open loop the computer uses whatever value the VE tables have for that certain Cell land RPM/Map point. With closed loop, the computer makes and remembers changes to those points which needed fueling changes. If it's unable to make these changes, your power will suffer.
streetrod93
07-16-2005, 09:16 PM
that make sence.... i had the car on the dyno about 3 weeks befor i got tuned to get an idea of what the car made. when i went to get tuned, on the same dyno, the car's base dyno was 25hp less than what it made only 3 weeks befor. so from the beggining i knew something was off... hopefully, if i get the conversion done, i can get it all straightened out. i know the car should make more power than what it did after the tuning.