Closed Loop......Why?

[GMPX]

Finally had a bit of a chance to actually use EFILive on my car for the first time in months (yes, that is pretty sad!).

I have been running semi-closed loop since the last tune went in and everything has been fine. Now, I just switched back to full open loop mode to test something. There has been countless hours of logging to get my VE table spot on at idle - mid throttle, and sure enough it is all hovering just around 14.7:1 as expected, in fact, sometimes I wonder if the PLX is working it is so steady!.
So, this made me think, why should we even enable the O2 sensor STFT if the VE table is dialed in so accurate?

Cheers,
Ross

[Chris81]

Good question! lol

Are you still run a MAF?

[Redline Motorsports]

How about when the motor over time starts wearing out. Its the closed loop that seems like it would provided the "loop" that would show that more compensation is required to keep the AFR at 14.7. If you tune in SD and the motor turns 100K and needs more help maint. 14.7, what will happen?

Its not going to make me change my mind that open loop is the way to go, especially since most of us never put enough miles on our cars to care!

[GMPX]

No MAF.

Howard, I suspect that the whole concept is it will keep an engine in a fit state for smog tests over most states of normal wear and tear. So, I guess it begs the question, should an enthusiast bother with it as they will generally do regular maintenance and have a WBO2 running all the time anyway. of course, keep in mind, it is probably totally illegal in all US states.

Cheers,
Ross

[bink]

No MAF.

Howard, I suspect that the whole concept is it will keep an engine in a fit state for smog tests over most states of normal wear and tear. So, I guess it begs the question, should an enthusiast bother with it as they will generally do regular maintenance and have a WBO2 running all the time anyway. of course, keep in mind, it is probably totally illegal in all US states.

Cheers,
Ross

Ross, I think you've hit the nail on the head.

I've only put about 10,000 miles on my car over the past few years - and hopefully I'll put a new engine in next year. I'd never run it without a wideband. I doubt most of us will ever will get near 100,000 miles on our modded cars - I should say 100,000 miles on a single setup.

Closed loop is another challenge ... and I think we all like challenges.
Just my $.02.

joel

[Black02SS]

I have been MAFless and Open Loop since I owned LS1Edit.. That should tell you guys how long ago that was. I haven't even looked back. The reason I like open loop so well is I have noticed that with different types of headers, the O2's don't get hot enough and will not switch properly. This has caused me grief in the past with the dreaded Insufficient Switching Codes. Since the day I decided to go open loop, I haven't had a narrowband o2 in my car and won't. The car feels better to me in open loop as I know for a fact what my AFR is at all times. Even without a wideband, I feel that after it is tuned with one, there is no need to keep it in the car.

[GMPX]

I guess that brings up another concern for a shop, they might be able to tune a combo for someone that runs perfect today, but one year down the track, 10,000 miles on the car how will it be?, It might in fact be perfect still, but if you have no way of monitoring this it might be a slight risk for a tuning shop, not that a NB02 is going to fix a WOT lean issue like monitoring a WBO2 would.

I think where I am heading with all this is we are starting to see ethanol blended fuels in some shops, I am a little reluctant to use it because 3 years ago the petrol companies were telling us how bad it was!!, I don't know what it does to the readings of a NBO2?. I am happy to pull them out and stuck some bungs in the exhaust if it is going to destroy $150 worth of O2 sensors.
With E85 you guys would know more about that than I would.

Cheers,
Ross

[Delco]

No MAF.

Howard, I suspect that the whole concept is it will keep an engine in a fit state for smog tests over most states of normal wear and tear. So, I guess it begs the question, should an enthusiast bother with it as they will generally do regular maintenance and have a WBO2 running all the time anyway. of course, keep in mind, it is probably totally illegal in all US states.

Cheers,
Ross

The other down side is you can actually use more fuel running closed loop than open loop set at the same AFR of 14.63.

I find this commonly with slighly bigger injectors the O2 closed loop feedback overcompensates ( it does on the std inj too ) so you constantly have a rich/lean condition to create the switch point.

With a good open loop tune - even the Alpha N tune I am currently playing with I am able to achieve a near perfect AFR everywhere.

Last trip I did I averaged 10.8l/100 km with a average speed of 120 kph , around town I average approx 12.8l/100 with a average of 40 kph.
not bad considering the 383 combo I am currently running with a 228 cam and very much oversize 62lb injectors ( remember it used to be blown - I have just removed the blower and are still running the custom 2 bar tune with Alpha N below 100 kpa - so everywhere now without the blower on).

Every now and then I switch it back to closed loop but economy and drivability are not as good.

[Black02SS]

Thanks for the info Delco. I noticed the same thing with a few of the cars I have done in closed loop complain of poor gas consumption. They end up just wanting me to leave it in open loop. What are your thoughts on tuning other cars in open loop only? What about a closed loop tune with ltft disabled?

[joecar]

I suppose closed loop shows us where we messed up, those of us that mess up all the time (me).