Runs better in open loop? - LS1TECH

Log In 


PCM Diagnostics & Tuning HP Tuners | AutoTap | Diablo | MAF Translator | HPP3 | FAST | Gen7 | Big Stuff 3
Sponsored by:
Sponsored by:

Runs better in open loop?

Reply
 
Thread Tools Search this Thread
Old 10-07-2009, 09:14 PM   #1
TECH Enthusiast
Thread Starter
iTrader: (7)
 
$750 L98's Avatar
 
Join Date: Jul 2005
Location: Round Rock, Texas
Posts: 725
Default Runs better in open loop?

I have a 1989 firebird with a LQ9 swap, with a cam, exhaust, and stall. The car seems to run well in open loop, without the O2 sensors. However as soon as it goes into closed loop, it seems like it isn't as easy to rev the motor, it also seems to bog on decel.

I did have 2 vacuum leaks (unplugged vacuum ports on the manifold), apparently the guy who installed the motor didn't plug those. There was also a large leak around the drivers side collector that i recently fixed.

Is it possible that my tune is now off and the car actually runs more efficient in open loop? Is there a way I could keep it in open loop to test the theory? I just don't understand why it feels so much more "snappy" in open loop, and turns into a slug in closed loop.

No codes are shown, Both O2 sensors are new, no more exhaust leaks, good gaskets, etc.
$750 L98 is offline   Reply With Quote
Old 10-08-2009, 12:22 AM   #2
TECH Fanatic
iTrader: (3)
 
Join Date: Feb 2009
Location: Highland, MI
Posts: 1,352
Default

One possibility is that your fueling is way off and once it goes into closed loop the computer is pulling or adding too much fuel. Get that thing tuned.
JDMC5 is offline   Reply With Quote
Old 10-08-2009, 10:48 AM   #3
Moderator
iTrader: (11)
 
jimmyblue's Avatar
 
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,556
Default

This could be sensor temperature related if you're
running long tubes (esp. uncoated), leading to a
false trimming. So could the exhaust air leaks, but
this should "settle in" over time.

If it runs well in open loop, at least your base tune
is not-insane. That's the good news. Trick is to get
closed loop to go along.

Got scan?
jimmyblue is offline   Reply With Quote
Old 10-08-2009, 02:07 PM   #4
TECH Enthusiast
Thread Starter
iTrader: (7)
 
$750 L98's Avatar
 
Join Date: Jul 2005
Location: Round Rock, Texas
Posts: 725
Default

I wish i had scan/tune software. Best I can do is make educated guesses at the moment and make sure everything works ok (scary I know). It runs awesome at WOT, and will spin the tires from a 60mph roll, but acts like a dog in most other situations. Drives me crazy!
$750 L98 is offline   Reply With Quote
Old 10-08-2009, 02:47 PM   #5
TECH Senior Member
iTrader: (10)
 
SIC LSX's Avatar
 
Join Date: May 2005
Location: Bossier city,LA barksdale AFB
Posts: 5,357
Default

speed density FTW screw 02's and screw a maff
SIC LSX is offline   Reply With Quote
Old 10-08-2009, 09:40 PM   #6
TECH Enthusiast
Thread Starter
iTrader: (7)
 
$750 L98's Avatar
 
Join Date: Jul 2005
Location: Round Rock, Texas
Posts: 725
Default

What is the cheapest option to get tuning myself? I really don't want this motor going down hill, if it pops, the car is getting sold off for parts, and it's my high school car. Should have kept the TPI honestly LOL

HPtuners and LS1edit seem to be about the same price, but are all programs really THAT expensive? It's either buy the program myself, or pay some one the same amount to tune it for me, but I don't get to keep the software....
$750 L98 is offline   Reply With Quote
Old 10-08-2009, 09:40 PM   #7
TECH Enthusiast
Thread Starter
iTrader: (7)
 
$750 L98's Avatar
 
Join Date: Jul 2005
Location: Round Rock, Texas
Posts: 725
Default

Well since it double posted, Is there anyway I could try to keep the car in open loop? Also I remember the tuner saying they couldn't get the KR down, I believe it was because of false knock. So max timing is only ever 20*, which seems very low, considering some seem to run mid 30-40s...

Could I unplug the Knock sensor and see what it does?
$750 L98 is offline   Reply With Quote
Old 10-08-2009, 10:58 PM   #8
TECH Fanatic
iTrader: (9)
 
Texas_WS6's Avatar
 
Join Date: Aug 2003
Location: Odessa, Texas
Posts: 1,783
Default

You sound like the kind of person that would be able to learn to tune with HP tuners or EFI Live pretty quickly. I personaly use HP Tuners and therefore I sugest it over others because I know it.

If you bought HP or EFI you can correct all your issues, learn how to tune, and be able to tune the car for future mods. Either realy is a great investment if you plan to play with your car. Both are more then worth the asking price. Thats were you should go before you start unpluging things.
Texas_WS6 is offline   Reply With Quote
Old 10-09-2009, 12:24 AM   #9
TECH Fanatic
iTrader: (3)
 
Join Date: Feb 2009
Location: Highland, MI
Posts: 1,352
Default

Quote:
Originally Posted by Texas_WS6 View Post
You sound like the kind of person that would be able to learn to tune with HP tuners or EFI Live pretty quickly. I personaly use HP Tuners and therefore I sugest it over others because I know it.

If you bought HP or EFI you can correct all your issues, learn how to tune, and be able to tune the car for future mods. Either realy is a great investment if you plan to play with your car. Both are more then worth the asking price. Thats were you should go before you start unpluging things.
agreed......


you shouldn't unplug you knock sensors, no. I had a case of false KR on my car and I tuned the sensors. I would say buy the hptuners software also, it will take time to become a good tuner but its worth it.
JDMC5 is offline   Reply With Quote
Old 10-09-2009, 06:07 PM   #10
10 Second Club
iTrader: (3)
 
randall 32's Avatar
 
Join Date: Feb 2009
Location: tn.
Posts: 180
Default

I might be wrong but i was thinking it stays in open loop until the o2 sensors reach operating temp. If that's the case it would stay in open loop if you unplug o2 sensors, but that wouldn't be the way too fix the problem.
randall 32 is offline   Reply With Quote
Old 10-09-2009, 11:48 PM   #11
TECH Fanatic
iTrader: (3)
 
Join Date: Feb 2009
Location: Highland, MI
Posts: 1,352
Default

Quote:
Originally Posted by randall 32 View Post
I might be wrong but i was thinking it stays in open loop until the o2 sensors reach operating temp. If that's the case it would stay in open loop if you unplug o2 sensors, but that wouldn't be the way too fix the problem.
correct, but that's a hack way of dealing with the problem
JDMC5 is offline   Reply With Quote
Old 10-10-2009, 11:25 AM   #12
11 Second Club
iTrader: (5)
 
KRAZY K 2000 TA's Avatar
 
Join Date: Mar 2003
Location: Stockton, NY
Posts: 805
Default

false it does not go into closed loop that way, it goes by enginge temp closed loop enable setting in your parameters.
Quote:
Originally Posted by randall 32 View Post
I might be wrong but i was thinking it stays in open loop until the o2 sensors reach operating temp. If that's the case it would stay in open loop if you unplug o2 sensors, but that wouldn't be the way too fix the problem.
KRAZY K 2000 TA is offline   Reply With Quote
Old 10-10-2009, 11:44 AM   #13
10 Second Club
iTrader: (3)
 
randall 32's Avatar
 
Join Date: Feb 2009
Location: tn.
Posts: 180
Default

Thanks for the correction, like i said i might be wrong.
randall 32 is offline   Reply With Quote
Old 10-10-2009, 01:57 PM   #14
TECH Fanatic
iTrader: (3)
 
Join Date: Feb 2009
Location: Highland, MI
Posts: 1,352
Default

Just to clarify I wasn't agreeing that closed loop is dependent on O2 temperature, I was agreeing that disconnecting them will force the system into open loop.

and yes, closed loop is based on coolant temperature.
JDMC5 is offline   Reply With Quote
Old 10-10-2009, 02:54 PM   #15
TECH Fanatic
iTrader: (9)
 
Texas_WS6's Avatar
 
Join Date: Aug 2003
Location: Odessa, Texas
Posts: 1,783
Default

part of the reason the engine runs better in Open loop is because while the coolant temp is still lower and the pcm is operating in OL the PCM is targetting a richer AFR then it does in Closed loop. Once it goes to CL it will be targetting Stoich (14.68). Depending on the size of the cam that might be too lean to make the engine idle right. It will make the engine choppier due to it being so much leaner. I personal have been running my setup in Open Loop Speed Density 3 bar and I target and tune my Open loop tables with a wide band to 13:1 AFR. At that richer setting the car sounds almost stock, very little lope. Once I let it go to Closed loop and the WB are reporting 14.6 as comanded it idles very ruff and the drivability goes to $h!t as compaired to Open Loop.

What i am saying is there comes a point depending on setup that closed loop operation becomes a hassle.

Pros to Open loop operation at all times is you can run wilder cams and mods and the engine will operate as desired.
Con to Open Loop operation; fuel economy is sacrificed. But I am not a green guy and could care less about economy.

I think you can tune to be in open loop more at slow speed and to go into closed loop once you get up to cruise speeds. I personaly have yet to get to that point. Maybe someone here can shed som light on this.
Texas_WS6 is offline   Reply With Quote
Old 10-10-2009, 03:21 PM   #16
TECH Fanatic
iTrader: (3)
 
Join Date: Feb 2009
Location: Highland, MI
Posts: 1,352
Default

Quote:
Originally Posted by Texas_WS6 View Post
part of the reason the engine runs better in Open loop is because while the coolant temp is still lower and the pcm is operating in OL the PCM is targetting a richer AFR then it does in Closed loop. Once it goes to CL it will be targetting Stoich (14.68). Depending on the size of the cam that might be too lean to make the engine idle right. It will make the engine choppier due to it being so much leaner. I personal have been running my setup in Open Loop Speed Density 3 bar and I target and tune my Open loop tables with a wide band to 13:1 AFR. At that richer setting the car sounds almost stock, very little lope. Once I let it go to Closed loop and the WB are reporting 14.6 as comanded it idles very ruff and the drivability goes to $h!t as compaired to Open Loop.

What i am saying is there comes a point depending on setup that closed loop operation becomes a hassle.

Pros to Open loop operation at all times is you can run wilder cams and mods and the engine will operate as desired.
Con to Open Loop operation; fuel economy is sacrificed. But I am not a green guy and could care less about economy.

I think you can tune to be in open loop more at slow speed and to go into closed loop once you get up to cruise speeds. I personaly have yet to get to that point. Maybe someone here can shed som light on this.
It's true you can run, what I call, a "hybrid" tune where it idles in open loop but goes to closed loop above idle. Open loop doesn't cause less gas mileage, the fact that you are commanding 13.0:1 causes worse mileage. Its for a good reason though, drive-ability over mileage.
JDMC5 is offline   Reply With Quote
Old 10-10-2009, 06:29 PM   #17
TECH Fanatic
iTrader: (9)
 
Texas_WS6's Avatar
 
Join Date: Aug 2003
Location: Odessa, Texas
Posts: 1,783
Default

I need to get some pointers from you and how to make the tune "hybrid". I prefer the way my car idles and drives around town under 40 mph in OL but I would like to have it go into CL when I get out on the hyway, were it runs just fine at the leaner 14.6 comanded AFR.

Any direction on doing this would be very helpful.
Texas_WS6 is offline   Reply With Quote
Old 10-12-2009, 10:29 AM   #18
TECH Enthusiast
Thread Starter
iTrader: (7)
 
$750 L98's Avatar
 
Join Date: Jul 2005
Location: Round Rock, Texas
Posts: 725
Default

Awesome info guys, I appreciate it!
$750 L98 is offline   Reply With Quote
Old 10-12-2009, 12:52 PM   #19
TECH Enthusiast
iTrader: (1)
 
WeathermanShawn's Avatar
 
Join Date: Dec 2005
Location: Denver International Airport, Colorado USA
Posts: 549
Default

I think 'Texas' was on to something.

Granted my cam is not wild, but I chose to stay closed-loop. I did all the usual tuning of the VE Table and MAF. For what it is worth I simply changed the O2 Switch-points to 550mv instead of the usually lower stock values.

Took almost all the air out of the Throttle Cracker below 2200 Rpm's. Whether changing the Narrow-band O2's 'really' work.while I can not specifically prove it..at least my wideband reads what I command and the Trims keep highway AFR at ~14.7.

If you can get closed-loop to work..it is really not a bad thing. It may just get to challenging as you start getting into the more wild cam profiles and larger injectors.

Good luck.

..WeathermanShawn..
WeathermanShawn is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Closed Loop Misfire/Stumble TheHeadFL LT1-LT4 Modifications 5 08-14-2013 08:32 PM
Open loop or Closed loop? NewOrleansLT1 LT1-LT4 Modifications 7 03-04-2013 06:34 PM
Car stuck in open loop when idling brad8266 PCM Diagnostics & Tuning 10 03-13-2007 12:38 PM
'98 Camaro, runs in open loop, not closed loop Justin @ EAD Performance PCM Diagnostics & Tuning 3 05-13-2006 12:03 PM
Open Loop vs Closed Loop SS125 PCM Diagnostics & Tuning 30 08-30-2005 09:06 AM


Tags
car, closed, coolant, corvette, engine, hptuners, idle, loop, ls2, o2, open, running, sensor, temperature, unplugging

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off



All times are GMT -5. The time now is 12:12 AM.