The Correct AFR for your Lotus - LotusTalk - The Lotus Cars Community
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 10-15-2017, 01:15 PM Thread Starter
Plug Whisperer
 
turbophil's Avatar
 
Join Date: Dec 2005
Location: Kansas City/ Overland Park
Posts: 6,305
The Correct AFR for your Lotus

Ever wonder about AFRs for your Lotus? Here's a Lotus specific piece to help!

Toyota Powered Lotus Air-Fuel-Ratios

Cheers,

Phil


Phil: NASA 2012 and 2014 TT1 Central Champion, 2005 GG Elige, Rev400, 485+whp REV X

2011 Pearl White Evora, BOE Skunk Works 6 SPD 435WHP || 2014 Black Evora Skunk Works IPS 390WHP|| 2011 White Evora Skunk Works IPS 390WHP || 2006 CO Elise, Rev400, Steet Car

____________________________________________

www.boefab.com: We Build Champions | Products-Service-Advice


BOE ClamHinge | BOE TVS SuperCharging, The Most Powerful Track-Worthy Forced Induction | EFI Engine Management | BOE The Essential Fuel Starve Solution| BOE Lotus Tow Package| BOE New-Tech Lotus Race Engines | The Right Oil Filter for Your Lotus | Custom Lotus ECU Tuning


Pain makes man Think. Thinking makes man Wise. Wisdom makes tracking a Lotus Endurable
turbophil is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 10-16-2017, 02:57 AM
Registered User
 
cyow5's Avatar
 
Join Date: Mar 2013
Location: NoVa
Posts: 3,879
Especially with your access to the ECU, would it be possible to use a wideband O2 sensor with analog out to force the ECU into closed-loop at WOT and target a richer setpoint? Wideband gauges can have a programmable output, so it seems like one of those "how hard can it be" kinda things.

"Lots Of Trouble; Usually Serious"
cyow5 is offline  
post #3 of 12 (permalink) Old 10-16-2017, 03:29 AM
Nein Kinder
 
Glen's Avatar
 
Join Date: Feb 2011
Location: Golden, Colo.
Posts: 1,568
@turbophil - Great article!

After reading this and some past comments, Iím concerned my OEM setup is running perpetually lean. I have a 2011 Elise SC and most of my operations are at 6,000í - 10,000í MSL with occasional excursions to 4,000í and 12,000í MSL. Itís not very precise, but cruising at 4,000 RPM, I get 30 MPG at 9,000í and 35 MPG at 12,000í. That seems pretty lean to me.

I know the MP42 with no intercooler is a dead end for more power, but is the AFR something BOE could address on my vehicle?

Glen

2011 Lotus Elise SC
Glen is offline  
 
post #4 of 12 (permalink) Old 10-16-2017, 05:48 AM
Sold my Exige S
 
+TSRAGR's Avatar
 
Join Date: Aug 2011
Location: TX Coast
Posts: 930
^ That's normal and is not necessarily lean. Air density decreases aloft, so the fuel injectors are scaled back to maintain ideal AFRs (this is not lean since there's less air being compressed). You'll see similar MPG results driving in extreme cold versus extreme heat at the same elevation.

The only problem is you're making less power from reduced compression at higher altitudes. Just be glad you have forced induction to help out!
+TSRAGR is offline  
post #5 of 12 (permalink) Old 10-16-2017, 07:21 AM
Registered User
 
silicon's Avatar
 
Join Date: Dec 2006
Location: New Jersey
Posts: 323
Quote:
For general tune and running verification, youíre interested in a single operating condition, which is steady state WOT. Youíre not interested in AFR at idle, as the ECU is forcing the idle to be at stoich through its closed loop operation using the primary NB02. It is common for a WB02 to not have great idle AFR data and will often show a lean indication at idle. This is due to a variety of reasons. Do not be alarmed if you observe a lean idle on your WB02 as it likely erroneous. You can verify your idle AFR with a scan tool and monitor the factory NB02 and the corresponding fuel trims. The idle AFRs are not a common problem and generally not a tuning issue due to the closed loop operation.
At idle, my AEM Wideband creeps up and off the charts pretty quickly and goes to --, also the exhaust gets really loud (like I have a 67 Hemi GTO or a small top fuel dragster) and when I touch the gas the AFR pulls right in to normal ranges (goes green) and it sounds smooth as butter. Does this sound normal?


Blackwatch - Black Emblems, Penske SA|Radium - Catch Cans, Coolant Tank, Intercooler Couplers, Green Ti Lug Bolts, Fuel Hose, Fuel Pressure Gauge|RLS - Green Intercooler Tubes|Mororso Hard Ano Red Baffled Oil Pan|Shift-I|BOE ProAlloy, BOELinks, Diffuser Brace, Quarter Stick|S111 BBHook, Spal Fans, Floormats|Fast Toys Green Carpet Buttons
silicon is offline  
post #6 of 12 (permalink) Old 10-16-2017, 10:20 AM
Registered User
 
cyow5's Avatar
 
Join Date: Mar 2013
Location: NoVa
Posts: 3,879
Quote:
Originally Posted by silicon View Post
At idle, my AEM Wideband creeps up and off the charts pretty quickly and goes to --, also the exhaust gets really loud (like I have a 67 Hemi GTO or a small top fuel dragster) and when I touch the gas the AFR pulls right in to normal ranges (goes green) and it sounds smooth as butter. Does this sound normal?
It sounds like your sensor is too close to the exhaust tip which allows outside air to corrupt the signal when the exhaust pulses are spaced out. Sometimes you have to just run open loop at idle for this reason, especially if you have no cat between the sensor and outside air. This is why I always cringe when I see shops put a sensor in the exhaust tip to do dyno tuning. Odds are that reading is garbage at low-ish rpm. Or you could just have a calibration issue.

"Lots Of Trouble; Usually Serious"
cyow5 is offline  
post #7 of 12 (permalink) Old 10-16-2017, 05:35 PM
Registered User
 
silicon's Avatar
 
Join Date: Dec 2006
Location: New Jersey
Posts: 323
Running PPE headers (SC) with their decat. Sensors are in their bung holes. I may try it with the sport cat instead of the decat and see if it changes anything.


Blackwatch - Black Emblems, Penske SA|Radium - Catch Cans, Coolant Tank, Intercooler Couplers, Green Ti Lug Bolts, Fuel Hose, Fuel Pressure Gauge|RLS - Green Intercooler Tubes|Mororso Hard Ano Red Baffled Oil Pan|Shift-I|BOE ProAlloy, BOELinks, Diffuser Brace, Quarter Stick|S111 BBHook, Spal Fans, Floormats|Fast Toys Green Carpet Buttons
silicon is offline  
post #8 of 12 (permalink) Old 10-16-2017, 06:46 PM
Nein Kinder
 
Glen's Avatar
 
Join Date: Feb 2011
Location: Golden, Colo.
Posts: 1,568
Quote:
Originally Posted by +TSRAGR View Post
^ That's normal and is not necessarily lean.
I’m a pilot and quite familiar with leaning out the mixture as altitude increases. But Phil’s document indicates the (OEM?) system tends to produce leaner than desired mixtures as altitude increases. It’s probably not a problem for most drivers, but I’m routinely two miles above sea level and occasionally as high as 14,250’ MSL (bonus points for figuring out where - I’m 20 miles away).

Glen

2011 Lotus Elise SC
Glen is offline  
post #9 of 12 (permalink) Old 10-16-2017, 09:56 PM Thread Starter
Plug Whisperer
 
turbophil's Avatar
 
Join Date: Dec 2005
Location: Kansas City/ Overland Park
Posts: 6,305
Quote:
Originally Posted by Glen View Post
Iím a pilot and quite familiar with leaning out the mixture as altitude increases. But Philís document indicates the (OEM?) system tends to produce leaner than desired mixtures as altitude increases. Itís probably not a problem for most drivers, but Iím routinely two miles above sea level and occasionally as high as 14,250í MSL (bonus points for figuring out where - Iím 20 miles away).

Glen
Hi Glen,

I didn't mean for it to read that the AFRs are leaner than desired... It's more that the SC'd cars start exhibiting NA like AFRs and that's because they essentially become NA manifold pressures at altitude... and then at the heights you're talking about, they won't even have the same air density as an NA car at sea level.

So the ECU is doing the right thing by allow for a less rich condition as manifold pressure drops.

That said, the Lotus SC tune at sea level is a horrid bit of code and blows up the SC regularly on track, IME. At 4,000+ feet, I don't think you'll see a SC'd car pop however. Any SC (the M45 from Lotus with their tune) that sees track time should run 100 octane and do a dance for their preferred deity...

Hope that helps,

Phil


Phil: NASA 2012 and 2014 TT1 Central Champion, 2005 GG Elige, Rev400, 485+whp REV X

2011 Pearl White Evora, BOE Skunk Works 6 SPD 435WHP || 2014 Black Evora Skunk Works IPS 390WHP|| 2011 White Evora Skunk Works IPS 390WHP || 2006 CO Elise, Rev400, Steet Car

____________________________________________

www.boefab.com: We Build Champions | Products-Service-Advice


BOE ClamHinge | BOE TVS SuperCharging, The Most Powerful Track-Worthy Forced Induction | EFI Engine Management | BOE The Essential Fuel Starve Solution| BOE Lotus Tow Package| BOE New-Tech Lotus Race Engines | The Right Oil Filter for Your Lotus | Custom Lotus ECU Tuning


Pain makes man Think. Thinking makes man Wise. Wisdom makes tracking a Lotus Endurable
turbophil is offline  
post #10 of 12 (permalink) Old 10-16-2017, 10:03 PM Thread Starter
Plug Whisperer
 
turbophil's Avatar
 
Join Date: Dec 2005
Location: Kansas City/ Overland Park
Posts: 6,305
Quote:
Originally Posted by +TSRAGR View Post
^ That's normal and is not necessarily lean. Air density decreases aloft, so the fuel injectors are scaled back to maintain ideal AFRs (this is not lean since there's less air being compressed). You'll see similar MPG results driving in extreme cold versus extreme heat at the same elevation.

The only problem is you're making less power from reduced compression at higher altitudes. Just be glad you have forced induction to help out!
That's right... At altitude, the first few PSI of boost just deal with the parasitic drag of the blower... Once you're to 6,000 feet or so, with most of these blower cars, they run like an NA car at sea level.

Quote:
Originally Posted by silicon View Post
At idle, my AEM Wideband creeps up and off the charts pretty quickly and goes to --, also the exhaust gets really loud (like I have a 67 Hemi GTO or a small top fuel dragster) and when I touch the gas the AFR pulls right in to normal ranges (goes green) and it sounds smooth as butter. Does this sound normal?
May have an air leak... The PPEs and 2bulars have thin flanges and often leak at the head. Each exhaust pulse carries a vacuum behind it and will draw in fresh air if it can. At low throttle opening, it doesn't take much air to throw off the readings... At idle, not a big concern... At higher RPM, there's enough exhaust gas available that small air leaks are essentially unmetered.

Quote:
Originally Posted by cyow5 View Post
Especially with your access to the ECU, would it be possible to use a wideband O2 sensor with analog out to force the ECU into closed-loop at WOT and target a richer setpoint? Wideband gauges can have a programmable output, so it seems like one of those "how hard can it be" kinda things.
That would be a fantastic amount of work... to that end, a good MAF based closed loop system is hard to beat. No finicky 02 sensors to fight you!

-Phil


Phil: NASA 2012 and 2014 TT1 Central Champion, 2005 GG Elige, Rev400, 485+whp REV X

2011 Pearl White Evora, BOE Skunk Works 6 SPD 435WHP || 2014 Black Evora Skunk Works IPS 390WHP|| 2011 White Evora Skunk Works IPS 390WHP || 2006 CO Elise, Rev400, Steet Car

____________________________________________

www.boefab.com: We Build Champions | Products-Service-Advice


BOE ClamHinge | BOE TVS SuperCharging, The Most Powerful Track-Worthy Forced Induction | EFI Engine Management | BOE The Essential Fuel Starve Solution| BOE Lotus Tow Package| BOE New-Tech Lotus Race Engines | The Right Oil Filter for Your Lotus | Custom Lotus ECU Tuning


Pain makes man Think. Thinking makes man Wise. Wisdom makes tracking a Lotus Endurable
turbophil is offline  
post #11 of 12 (permalink) Old 10-17-2017, 02:03 PM
Registered User
 
doug_porsche's Avatar
 
Join Date: Jun 2008
Location: 38th state
Posts: 2,249
Thanks. Good datapoint.

Apexes are a lot like relationships. So tough to get right, so easy to see where they went wrong.

The secret to a long life is ------- not dying.
doug_porsche is offline  
post #12 of 12 (permalink) Old 10-20-2017, 07:17 PM
Registered User
 
Join Date: May 2016
Posts: 14
'I have a 05 Elise with a BOE REV300 and operate a 4700' in elevation. If I install a smaller blower pulley to get my boost up to the same psi as a sea level car will my AFR read the same as a sea level car? Currently it runs just under 13:1 under boost all the way up to redline, witch scares me.
rwbakk is offline  
Sponsored Links
Advertisement
 
Reply

  LotusTalk - The Lotus Cars Community > Vendor Member Section > BOE Fabrication

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the LotusTalk - The Lotus Cars Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome