Bogging at cruise - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 05-06-2013, 01:10 PM   #1
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default Bogging at cruise

My '94 sarted bogging on me the other day. At first I thought it may have been a tuning issue, but it doesn't seem the case. The car has been runing fine on this tune for a long time now, and autocrossed just fine a few weeks ago.

The bog started at low load around 2-3000rpm in third or fourth gear driving around town. The engine 'misses' or 'bogs' momentarily, followed by a 11-12 AFR readout on the wideband. It sometimes continues to bog with the rich conditions, and other times it levels back to cruise AFRs (14-15). On the highway this morning, it seemed to be a little worse than the last few days.

I'm planning to change the plugs and wires before driving again. It probably will not hurt to recalibrate the widebands also. Anything else I should be worried about?
Enginerd is offline   Reply With Quote
Old 05-06-2013, 01:30 PM   #2
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

The only way to get a rich reading on a WBO2 is to be rich. Any other problem (misfire, etc.) results in a lean reading because there is excess O2. If you go rich beyond bog all the way to misfire, that will read lean too.

So, what's up with fuel pressure? What's your setup? Do you have a big fuel pump overpowering the FPR? Stock FPR? Bandaids?
hornetball is offline   Reply With Quote
Old 05-06-2013, 01:59 PM   #3
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

The car is naturally aspirated with MSPNP1, innovate LC1, walpro 190lph, stock fpr, ev14 550cc injectors. 145k miles or so on the engine and chassis.
Enginerd is offline   Reply With Quote
Old 05-06-2013, 03:07 PM   #4
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

If you have MS, you should be able to log the events. That would help.

Those are darn big injectors and a lot of fuel pump for a naturally aspirated car, BTW.
hornetball is offline   Reply With Quote
Old 05-06-2013, 03:38 PM   #5
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

Yeah. The car was boosted the past two years, and I wanted to step down to the non-boosted street class for autocross this year. I will try to log it later today. I agree, we should be able to see the anomoly on a log before the rich condition that I see on the local gauge, right?
Enginerd is offline   Reply With Quote
Old 05-06-2013, 04:22 PM   #6
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

I would think so. Ultimately, it's the MS that's deciding on the PW of the injectors. It would be nice to see what it is responding to. This assumes, of course, that the FPR isn't being overwhelmed or we aren't asking for such a small PW that the injectors can't really deliver. Given how much history you have with the setup, the above seems unlikely -- although it would be easier to control smaller injectors.
hornetball is offline   Reply With Quote
Old 05-07-2013, 11:51 PM   #7
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

Ok. I logged my drives today. Below is a snippet from where it occurs.

I see that Gego goes to 100% at every instance I get the rich spike and bog. I presume this would be linked to a failing wideband sensor?


Attached Thumbnails
Bogging at cruise-ms_log_07may2013.jpg   Bogging at cruise-ms_log_07may2013_2.jpg  
Enginerd is offline   Reply With Quote
Old 05-08-2013, 01:25 PM   #8
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

Would have helped to have posted the log file.

Gego of 100% just means that the MS has transitioned to open loop for some reason. 100% means that the exhaust gas feedback gain is 1 (i.e., no gain -- Gego is not making any adjustment to the injector pulse width). That doesn't necessarily mean that the VE table is being used directly, as there are other gains.

In general, when operating in closed loop, it looks like your Gego is trending towards 90%. This is probably the limit of the authority (10%) that you've granted it in the "Exhaust Gas Settings" dialogue.

Bottom line, your basic tune is too rich. If you've got a good VE table, you should see Gego trending above and below 100%, hopefully less than 5%. Time to go do some fuel tuning to get your VE tables squared away. I'd start with a free air calibration and then head out to either autotune or log and use VE Analyzer.
hornetball is offline   Reply With Quote
Old 05-08-2013, 01:55 PM   #9
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

I'll post some more tonight. The log is around 7mb, but I'll see if I can get it up.

With what you've said, I am already replacing plugs and wires since they are about at the point they could be replaced. I'll free air calibrate and see if I'm being overly agressive on any other gains. IIRC I last touched the tune before putting it away for the winter, and the clt/air-temp correction may need adjusting for hot weather.
Enginerd is offline   Reply With Quote
Old 05-08-2013, 03:10 PM   #10
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

Quote:
Originally Posted by Enginerd View Post
clt/air-temp correction may need adjusting for hot weather.
??? Not sure what you're referring to.
hornetball is offline   Reply With Quote
Old 05-17-2013, 06:03 PM   #11
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

Coolant Related Air Density is what I was referring to.

You were quite helpful. Thank you.

The solution was the combination of recalibrating the LC-1 wideband, removing 1 point in the Fuel VE Table at lower rpm, 2 points in the higher rpms, and reducing the correction on the hotter end of the coolant related air density table.

Looking back to the end of last year, I probably tweaked the tables a little bit when it was cold and the issue only showed up now that spring/summer is here.

I took the car out for a spin around town, and the ego correction stays within 3-5% now.
Enginerd is offline   Reply With Quote
Old 05-17-2013, 06:27 PM   #12
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,008
Total Cats: 583
Default

Quote:
Originally Posted by Enginerd View Post
removing 1 point in the Fuel VE Table at lower rpm, 2 points in the higher rpms
Are you actually manually changing your VE values?!?

You should be using Tunerstudio's Autotune or MegaLogViewer's VE Analyzer function. That will give you far better results. I'm an "old school" VE Analyzer type myself.
hornetball is offline   Reply With Quote
Old 05-17-2013, 07:01 PM   #13
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

Manually fixed what I needed to.
Enginerd is offline   Reply With Quote
Old 05-17-2013, 10:07 PM   #14
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 9,131
Total Cats: 598
Default

Quote:
Originally Posted by hornetball View Post
??? Not sure what you're referring to.
Quote:
Originally Posted by Enginerd View Post
Coolant Related Air Density is what I was referring to.
There is also air temp enrichment that depends on the temp the air temp sensor sees.
triple88a is offline   Reply With Quote
Old 06-07-2013, 09:19 PM   #15
Senior Member
Thread Starter
iTrader: (1)
 
Join Date: Oct 2009
Posts: 1,434
Total Cats: 58
Default

Thanks for your help. I bit the bullet and retuned the entire fuel table on my way to work this morning (~20mile highway drive). I turned off: overrun, accel, ego and clt related air density and also recalibrated my TPS open and closed limits.

For the ride home, I turned everything back on, one by one, and think I found the culprit. The AE Driven Fuel PCT goes nuts at partial throttle. I shut off Accel Enrichments and the car drives perfect. Time to troubleshoot the TPS sensor.

Attached Thumbnails
Bogging at cruise-screen-shot-2013-06-07-7.23.03-pm.jpg  
Enginerd is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
FS/FT: 03.5 Mazdaspeed Protege leatherface24 Cars for sale/trade 15 10-16-2015 12:35 PM
1991 special edition with hard top full part out JC, NJ russian Miata parts for sale/trade 6 10-08-2015 04:01 PM
Time to start learning and play with tuning The Gleas MEGAsquirt 3 10-01-2015 10:30 AM
Got bad Crank Angle Sensor and Random Misfire codes, but runs fine. Greasyman General Miata Chat 2 09-28-2015 11:44 AM
Missfires on idle and cruising (no load) emarkey DIY Turbo Discussion 2 09-05-2015 07:59 PM


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 Off
Refbacks are Off



All times are GMT -4. The time now is 07:27 AM.