Open loop - ZR-1 Net Registry Forums

Jim Nolan · 03-18-2009

What would be the the up and the down side to running a modified LT5 continous open loop over closed loop? The car will be street driven and rarely raced. The primary mods will be full porting and headers.

Pete · 03-18-2009

There's really no big deal if it's tuned right.

Our Z's go into open loop anytime you wide open throttle it.

Closed loop is for cruising speeds.

Basicly if tuned right you don't even need closed loop.

Pete

Demps · 03-18-2009

Pete is right on...IF IT IS TUNED RIGHT.

I have one in a modified top-end car. The throttle response is instantaneous. The gas mileage in town is <12mpg and no better than ~20mpg on the road. NOT tuned right.

Ted

XfireZ51 · 03-18-2009

Quote:

Originally Posted by Jim Nolan

What would be the the up and the down side to running a modified LT5 continous open loop over closed loop? The car will be street driven and rarely raced. The primary mods will be full porting and headers.

Jim,

No reason to use O/L. C/L brings additional parameters into play that are used for idle quality and part throttle cruise. Typically people will use O/L when they've installed more radical cams because C/L idle becomes more difficult to tune. Actually a way to deal with that but its not readily available.
If you're using the vehicle for cruise its preferable to use C/L.

Locobob · 03-20-2009

The big problem I see with running open loop full time is that you'll have to tune rich to be on the safe side since you are disabling your motors feedback system. Not exactly ideal for fuel economy, emissions, and motor cleanliness. I'm not aware of any advantages to open loop only, maybe one of the chip gurus can enlighten us?

03-18-2009	#1
Jim Nolan Join Date: Jan 2007 Location: Florida Posts: 241	Open loop What would be the the up and the down side to running a modified LT5 continous open loop over closed loop? The car will be street driven and rarely raced. The primary mods will be full porting and headers.

03-18-2009	#2
Pete Join Date: Dec 2003 Location: Chicagoland,IL Posts: 2,679	Re: Open loop There's really no big deal if it's tuned right. Our Z's go into open loop anytime you wide open throttle it. Closed loop is for cruising speeds. Basicly if tuned right you don't even need closed loop. Pete __________________ '91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage

03-18-2009	#3
Demps Join Date: Jan 2006 Location: Niceville Posts: 998	Re: Open loop Pete is right on...IF IT IS TUNED RIGHT. I have one in a modified top-end car. The throttle response is instantaneous. The gas mileage in town is <12mpg and no better than ~20mpg on the road. NOT tuned right. Ted

03-20-2009	#5
Locobob Join Date: Jan 2004 Location: Portland, OR Posts: 1,057	Re: Open loop The big problem I see with running open loop full time is that you'll have to tune rich to be on the safe side since you are disabling your motors feedback system. Not exactly ideal for fuel economy, emissions, and motor cleanliness. I'm not aware of any advantages to open loop only, maybe one of the chip gurus can enlighten us? __________________ Robert ZR-1 Net Registry Oregon State Director 91 ZR-1 #431 Black/Black LPE 368