Q for the pump gas users:

F

Fark

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Aug 12, 2002

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• Dec 4, 2002

• #1

Here in PA they use a different type of fuel starting in NOV and use a different type in the summer months. Lo and behold I've started to foul plugs religously since around then, despite the colder air which should make the bike leaner.

I am wondering how the winter fuel would affect combustion.

 

gwcrim

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Oct 3, 2002

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• Dec 4, 2002

• #2

I live in Ohio and I can tell the difference in my truck. It pings much more on the winter gas. I'm sure it would affect the way a bike runs.

 

C

crmx91

Member

Dec 4, 2002

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• Dec 4, 2002

• #3

i noticed that too in my bike .. and im in east texas!

 

J

jmics19067

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Jan 22, 2002

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• Dec 5, 2002

• #4

here is a wild guess and hopefully Rich Rohrich will take a look at my reply and straigten me out if needed.

I am assuming that in winter vapor lock is not an issue so they raise the percentage of low end boiling points of the fuel, hopefully to help cold starts plus whatever they think will help emisions.
With the lighter make up of the fuel it will flow thru the jets of your carb easier making it richer, and with less high end boiling point additives less large droplets of fuel are hitting hot spots in your engine.
The large droplets hitting the hot spots have a cooling effect as they evaporate helping prevent detonation.

And that would be my guess as why it could run rich in one engine and then ping in another,especially considering the differences of intake design between a bike and a car.

 

F

Fark

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Aug 12, 2002

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• Dec 5, 2002

• Thread starter
• #5

I just read on one of EG's articles that if the specific gravity to the fuel changes, the effective jetting can also change.

Carbs meter fuel off of the volume of air drawn into the motor. IF you change the specific gravity a different amount of fuel will be drawn.
I need someone to break it down for me. It doesn't go into much detail.

 

slickpuss

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Jan 19, 2002

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• Dec 8, 2002

• #6

Ive noticed my bike running way to rich since Nov. I didnt have any idea what was causing it, but Ive had to rejet. This is an interesting theory. I work at a refinery, and tomorrow I am going to see exactly what they do different. I will get back to you all.

 

F

Fark

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Aug 12, 2002

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• Dec 12, 2002

• Thread starter
• #7

Excellent slick! I've been meaning to ask my freind's dad who works at Sun Oil but haven't had the chance. Let me know man!

 

slickpuss

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Jan 19, 2002

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• Dec 12, 2002

• #8

Im still waiting for my answer, but I will post it soon when I get it.

 

slickpuss

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Jan 19, 2002

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• Dec 21, 2002

• #9

Well this is the answer they gave me....

The biggest difference in winter gasoline compared to summer gasoline is that the vapor pressure is higher during the winter time period. This is done to ensure adequate vehicle cold-start and warm-up driveability during the cooler winter period.

The primary means to increase vapor pressure is to blend more low-boiling material (butanes & pentanes) into the gasoline.



And also I found very interesting info at this link that they gave me....
http://www.chevron.com/prodserv/fuels/bulletin/oxy-nona/

 

Rich Rohrich

Moderator / BioHazard

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Jul 27, 1999

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• Dec 21, 2002

• #10

So essentially for the same volume of fuel passing through the jet a greater percentage of the fuel will vaporize and be available to the combustion process to partner up with available oxygen molecules effectively making the mixture richer. Less liquid fuel passing untouched through the system will also tend to reduce spooge a bit.

An important point to keep in mind is the fact that octane is NOT evenly distributed throughout the temperature range of the fuel. By that I mean some of the high temp components may be higher octane than the low temp components or vice versa. So if you are near the knock limit of your fuel normally, when the weather gets colder and the fuel changes it's worth your while to be VERY CONSERVATIVE in your WOT main jet tuning until you get comfortable with the changes in the fuel (it's a moving target each season) or you risk running into knock fairly quickly. The reduction in liquid fuel passing through the chamber with winter spec fuel will tend to mean higher piston crown temperatures as well, because less liquid fuel will be available to leech heat from the crown. So watch the timing adavance and main jet sizing.

 

Last edited: Dec 21, 2002

J

jmics19067

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Jan 22, 2002

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• Dec 21, 2002

• #11

Originally posted by jmics19067

With the lighter make up of the fuel it will flow thru the jets of your carb easier making it richer,

Click to expand...

oooops!!!!!

Originally posted by Rich Rohrich
So essentially for the same volume of fuel passing through the jet a greater percentage of the fuel will vaporize and be available to the combustion process to partner up with available oxygen molecules effectively making the mixture richer. Less liquid fuel passing untouched through the system will also tend to reduce spooge a bit.

An important point to keep in mind is the fact that octane is NOT evenly distributed throughout the temperature range of the fuel. By that I mean some of the high temp components may be higher octane than the low temp components or vice versa.

Click to expand...

thanks for clearing me up!!!!!

 

F

Fark

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Aug 12, 2002

438

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• Dec 23, 2002

• Thread starter
• #12

Rich... thanks for breaking it down for me. I really look up to you for taking the time explain things. I too have a thirst for knowlege but unless it's written in laymen's I lose interest. Again, thanks and Happy holidays.

 

S

sharp

Member

Sep 30, 2001

233

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• Dec 29, 2002

• #13

I am glad this finally came out. Last winter I started fouling plugs profusely and had to jet leaner during the colder months which screwed with my mind more than anything--- I didn't know what the heck was wrong. Since then I have been using 50/50 race/pump gas mix and now have to fatten it (jetting) up a bit like I should for the colder weather. The race gas appears to reduce the effect the pump gas causes with its varying vapor pressure relative to the season---duh. But whats really screwy is that ambient temperature does not stand still either. One day could be 35 deg. and the next 75 deg. and you get the same higher vapor pressure fuel out of the pump on the warmer day. So I try an reduce the effect that the variable fuel (pump gas) has on jetting by mixng with race gas. I know I tried to sound smart here but I am not. I am just thanking you guys for shedding light on this. Heck, last year during the plug fouling fiasco I was ready to be put on Prozac. I had made a BAD ASSUMPTION - that that crap comming out of the pump was CONSISTANT (constant).