Jump to content
  • When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Winter Blend Gasoline and AFR


'76mintgrün'02

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

     DISCLAIMER -- I now disagree with much of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book as timing maps for our engines.  I've also switched from using ported-vacuum to manifold, with better results.  I apologize for spreading misinformation. 

(3-28-2024)  

 

Link to comment
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

Link to comment
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

 

 

 

  • Like 1

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

Link to comment
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

  • Like 2

Frank,  SaharaX2
'75 2002 Sahara (Janice)
'74 2002 Sahara (Camilla) dearly departed
'76 2002 Anthrazit (Gonzo) now daughters car

Link to comment
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.

  • Like 1

Paul Wegweiser

Wegweiser Classic BMW Services

Nationwide vehicle transport available

NEW WEBSITE! www.zenwrench.com

Link to comment
Share on other sites

I've never noticed this. Rather interesting! Though I personally like to cruise closer to 15 for the mileage factor.

-Nathan
'76 2002 in Malaga (110k Original, 2nd Owner, sat for 20 years and now a toy)
'86 Chevy K20 (6.2 Turbo Diesel build) & '46 Chevy 2 Ton Dump Truck
'74 Suzuki TS185, '68 BSA A65 Lightning (garage find), '74 BMW R90S US Spec #2

Link to comment
Share on other sites

  • 4 months later...
On 11/14/2019 at 9:12 PM, roadhog0 said:

I've never noticed this.

 

Obviously, you need to pay closer attention, Nathan!  :D 

 

 

I recently noticed that my idle has been a little richer, down at 12 and just below that at times, so today I spun the AFR gauge around so I could see it while standing over by the distributor and turned the idle mixture screw in almost third of a turn, which brought the idle AFR back up to 12.5.  I am thinking we might be done with the winter blend for the year.  

 

Has anyone else noticed a change yet?

 

I wonder just how sharp the cut off is between them.  I'll bet they just start adding the current fuel to whatever's still in the big tanks; in which case, the change might be somewhat gradual.  (?)


Tom

  • Haha 1

     DISCLAIMER -- I now disagree with much of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book as timing maps for our engines.  I've also switched from using ported-vacuum to manifold, with better results.  I apologize for spreading misinformation. 

(3-28-2024)  

 

Link to comment
Share on other sites

gradual....depending on how busy the gas station is.  really busy they will refill tanks more often and the noticeable change could occcur in between one 2002 fillup.   if it is a "Corner Gas" type place, transition could take months..

 

of course, you don't drain your car's tank either, so there will be mixing for a bit there too.

 

speaking of Corner Gas...that comedy show is a great isolation binge watch...:-)

Edited by mlytle

2xM3

Link to comment
Share on other sites

Okay, I will cut Nathan some slack for not noticing the transition(s).  :) 

 

I have a stock air cleaner installed on my 32-36 and it makes it hard to see and adjust the idle mixture screw and especially hard to get at the idle speed screw (water choke version).  I've considered adding a little light under there, but have been too lazy to actually do it.  It'd be fun to have a little dome light on the underside of the filter housing, with a pull-chain switch to turn it on.  I love those little dangly beady chains.

 

011.thumb.JPG.1cfdb32e2e722ef3a62858887edeae58.JPG

 

I have this head on the bench up in the shop, which is kind of handy for mocking things up.  Here's one solution for reaching that hidden idle mix screw

 

IMG_2966.thumb.JPG.9f59dde6e0fc4b01ea09ef17749c8ce6.JPG

 

(that piece of tubing keeps the screw driver head locked on the mixture screw)

 

IMG_2965.thumb.JPG.8e8cc012b9b1b561919756d07241bf08.JPG

 

I realize it isn't often that we need to adjust the mixture, once we've settled into the happy fuel/spark combination, but it would be fun to see that little handle bouncing around as the engine vibrates.  My kind of fun anyway.  Maybe I should install it today....

 

Imagine how cool it would be to run a flex shaft into the cockpit, with a little knob in the console, for adjusting the idle mix!!

 

Then, add a knob next to that for adjusting the dwell (non vacuum distributors only, of course) and another knob to adjust the timing on-the-fly.

 

There's so much fun stuff to do that it is hard to choose sometimes.  It is fun to dream about it anyway.

 

Tom

  • Like 1
  • Thanks 1

     DISCLAIMER -- I now disagree with much of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book as timing maps for our engines.  I've also switched from using ported-vacuum to manifold, with better results.  I apologize for spreading misinformation. 

(3-28-2024)  

 

Link to comment
Share on other sites

FWIW - this year, for the obvious reason, the gas companies were given allowance to not meet the required switchover date from winter gas to summer gas. So we may be running winter gas longer into the spring/summer... I’ll let Tom tell us when that happens. ?

 

Tom-too

  • Like 1

Where we goin’? … I’ll drive…
There are some who call me... Tom too         v i s i o n a u t i k s.com   

Link to comment
Share on other sites

Hi Tom-02 :) 

 

Do you think the change over date varies based on climate?  Meaning, some areas are colder, so they change later/earlier?

 

Tom

     DISCLAIMER -- I now disagree with much of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book as timing maps for our engines.  I've also switched from using ported-vacuum to manifold, with better results.  I apologize for spreading misinformation. 

(3-28-2024)  

 

Link to comment
Share on other sites

Tom - I have no idea.  The article I read about the waiver for this year implied it would normally be a nationwide required date.  Who knows, with the waiver - some may even try to introduce their summer gas earlier!

 

It looks to be a nationwide date  - May 1 from this article I just looked up. Read it all - lots of geek info there.

https://www.eia.gov/todayinenergy/detail.php?id=11031

Edited by visionaut
link added
  • Thanks 1

Where we goin’? … I’ll drive…
There are some who call me... Tom too         v i s i o n a u t i k s.com   

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • BMW Neue Klasse - a birth of a Sports Sedan

    BMW Neue Klasse - a birth of a Sports Sedan

    Unveiling of the Neue Klasse Unveiled in 1961, BMW 1500 sedan was a revolutionary concept at the outset of the '60s. No tail fins or chrome fountains. Instead, what you got was understated and elegant, in a modern sense, exciting to drive as nearly any sports car, and yet still comfortable for four.   The elegant little sedan was an instant sensation. In the 1500, BMW not only found the long-term solution to its dire business straits but, more importantly, created an entirely new
    History of the BMW 2002 and the 02 Series

    History of the BMW 2002 and the 02 Series

    In 1966, BMW was practically unknown in the US unless you were a touring motorcycle enthusiast or had seen an Isetta given away on a quiz show.  BMW’s sales in the US that year were just 1253 cars.  Then BMW 1600-2 came to America’s shores, tripling US sales to 4564 the following year, boosted by favorable articles in the Buff Books. Car and Driver called it “the best $2500 sedan anywhere.”  Road & Track’s road test was equally enthusiastic.  Then, BMW took a cue from American manufacturers,
    The BMW 2002 Production Run

    The BMW 2002 Production Run

    BMW 02 series are like the original Volkswagen Beetles in one way (besides both being German classic cars)—throughout their long production, they all essentially look alike—at least to the uninitiated:  small, boxy, rear-wheel drive, two-door sedan.  Aficionados know better.   Not only were there three other body styles—none, unfortunately, exported to the US—but there were some significant visual and mechanical changes over their eleven-year production run.   I’ve extracted t
  • Upcoming Events

  • Supporting Vendors

×
×
  • Create New...