Jump to content
'76mintgrün'02

Winter Blend Gasoline and AFR

6 posts / 364 viewsLast Reply

Recommended Posts

I recently noticed that my AFR gauge is running a little leaner and figure that must be due to the switch to winter-blend gasoline at the pump.  

 

It is not a big difference, but cruising along, my car now seems to run more towards the upper end of 13 than the bottom.  

 

I think I am still "safe", but was doing some reading yesterday, and learned that the difference is compounded by the fact that the stoichiometric ratio of winter gasoline runs between 14.3-14.4:1, as opposed to 14.7 for normal gas.  

 

I just thought that was interesting, so I figured I share it.

 

This is where I found that information

http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html

 

Tom

  • Like 3

Share this post


Link to post
Share on other sites
I recently noticed that my AFR gauge is running a little leaner and figure that must be due to the switch to winter-blend gasoline at the pump.  

 

It is not a big difference, but cruising along, my car now seems to run more towards the upper end of 13 than the bottom.  

 

I think I am still "safe", but was doing some reading yesterday, and learned that the difference is compounded by the fact that the stoichiometric ratio of winter gasoline runs between 14.3-14.4:1, as opposed to 14.7 for normal gas.  

 

I just thought that was interesting, so I figured I share it.

 

This is where I found that information

http://zhome.com/ZCMnL/PICS/winterGas/winterGas.html

 

Tom

I think the article you referenced is dated. According to Wikipedia “Some U.S. states have enacted laws to ban MTBE in certain areas. California and New York, which together accounted for 40% of U.S. MTBE consumption, banned usage of the chemical in gasoline, effective 2002 and 2004, respectively.[5][6] As of 2007, 25 states had issued complete or partial bans on the use of MTBE.”

 

 

Sent from my iPad using Tapatalk

Share this post


Link to post
Share on other sites
Quote

The trick is to have the right fuel for the right time of year. In the summer, when the temperature is high, the presence of too many light components will cause the fuel to evaporate too readily. This can result in vapour lock, an over-rich mixture and excessive evaporative emissions. In the winter, too many heavy components keep the fuel from evaporating, causing hard starting, a lean mixture, heavy hydrocarbon emissions and poor converter light-off.

 

but the chemistry is still valid.  So if they don't use MTBE, they're still using (X)butanes, ethanol, and other things

to raise the vapor pressure to a point that's a good compromise for mean temperature AND humidity.

 

Carburetors can't compensate for octane and vapor pressure and flash point, etc etc like injection can.

So it's not surprising that you're running a bit leaner, Tom.  More oxygen from cooler air, less fuel value from

less- potent fuel, and that pushes you lean.  

 

t

 

 

 

Share this post


Link to post
Share on other sites

Throw a pint of diesel fuel or Marvel Mystery Oil in the tank (10 gal) and it will run better all the time.
In the summer it will also help prevent vapor lock.
This tip is from Great Race tech Randy Rundle.


Sent from my iPad using Tapatalk

Share this post


Link to post
Share on other sites

I experienced exactly this in my tii last year (mid/late November). Cruising AFRs went from 13-14ish to 15ish. Adjusted linkage / verboten screw accordingly...then set it back in April/May. 

 

YMMV.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.