Winter gas (detonation question also lean/rich question)

[XH29N0G]

Question:  Is winter gas more prone to detonation?

Background:  I drove my car last weekend and noticed detonation that I had not noticed last time I ran my car during the first week of October.  The difference was that I filled my tank at the end of that day (Oct 9th); so, I think I might have gotten my first tank of Winter gas in between.  Also, I know my timing was set pretty close to the point where I could hear detonation (because that is what I was doing in Sept.).  The temp was lower. 55 degrees vs 70 degrees.    

What I know:  Winter gas mix comes in around Oct 1 and is more volatile and has less energy than Summer gas mix.

[Stegs]

winter gas is of course a different blend. Your car might not like it

as far as octane goes, if it says 91 on the pump, it has to be atleast 91 coming out the hose


Id be curious on this also.....my guess is your car doesnt like that fuel you got

[stripedelete]

Same thing here.  I thought I put in too much StaBil.   

[XH29N0G]

It makes sense that the different mixtures should have the same octane if that is what is advertises, but with different compounds.  I am just curious about whether it also ends up leading to different knock/detonation behavior. 

I guess my car doesn't like it.  Maybe it is like when I eat too many baked beans.

[Kern Dog]

I thought that the winter gas blend is supposed to evaporate slower. I'm not sure how this would affect detonation.

[1974dodgecharger]

I'm curious about his detonation....what's the temp gauge say?

Why do u think u have it?

[XH29N0G]

1974 dodgecharger, 

The temperature gauge is the stock one (so not necessarily accurate).  The temp is steady at something like 190-200 when it runs. 

I think it is gas quality.  Just before the gas change I was working with the car and found the sweet spot for detonation (I am 1 degree back total advance from where I could just detect detonation in the summer).  Stegs makes a point that it is supposed to be the same octane (and octane and knock are related) so the two mixes are designed to have similar anti knock characteristics.  It looks like the octane rating depends on several factors and that is why there is R, M, (R+M)/2, AKI, RdON, ... so if it was very close to detonating and the knock caharacteristics of summer and winter are different  at WOT near 3000-4500 RPM (which is outside the range of R and M calibrations) my thinking was that the engine which was right at the point of knock, tipped over into noticeable knock.  I am not sure whether this is valid reasoning and was hoping for was someone on the board who works with fuels and could give a more definite answer. 

Kern Dog, I believe you are right.  So there must be some difference.  The issue may be whether the octane rating is the same under load conditions different from those used to determine R+M ratings.   

[PlainfieldCharger]

I had the same problem last year. Went for a ride on a beautiful day after Thanksgiving and refueled about 30 miles away. Started pinging on the way home..
Here is a good article.


http://www.popularmechanics.com/cars/a3180/summer-blend-vs-winter-blend-gasoline-whats-the-difference-13747431/

[1974dodgecharger]

I guess I never heard detonation before in our cars....plus I don't think I ever would car so loud with 3inch exhaust and flow masters.  

Must be my car engine was built with such low compression...I don't have it. 


Kind of weird but wouldn't going for a ride in a car with detonation maybe it will happen with my blower....

[BSB67]

I thought that the winter gas blend is supposed to evaporate slower. I'm not sure how this would affect detonation.

I think you have that backwards

[Dmichels]

I really hate the crap gas these days the new cars with the computers run OK on it but our old cars really like the old gas. I can easily get 100ll avgas. The car loves it. I can tune it where it should be, without backing off the timing.  From what I read the "street" octane is about 96. It has a little "lead" in it for the valve seats. Costs me $4.29 gal. Well worth it. Smells good too!
Dave

[birdsandbees]

Just be careful, as that 100LL will dry your stock rubber hoses out. Trust me, I know.... I have 500 gallons of it in the yard at any one time!   It also has a LOT of lead in it compared to leaded premium of old, but it certainly does save the valve seats if you haven't had them hardened. I run a mix of about 5 gallons 100 LL to 15 gallons of Premum unleaded in my 383 Bee and 440 Bird.

[Dmichels]

I am using Gates brand rubber line. Is there different fuel hose for aircraft? Please tell me more
Thanks
Dave

[birdsandbees]

I had an '83 Southwind motor home. That old 454 sure loved it's octane and lead or it would knock. I made the mistake of running it when I could direct off the 100LL. It only took a year to dry out and rott my fuel lines and was certainly no fun dropping the tank to put new lines on.

Aircraft run some expensive MIL spec lines, all I  can tell you is to watch your hoses for them starting to get stiff and replace. Don't forget the tank lines at the back.

And yes it does have a REALLLY sweet smell !!

[Dmichels]

thanks

[birdsandbees]

As a teen (1979) I use to go out to the airport and fill the 'Bee with 100/130. You want to talk about a sweet smell! It also only had 1/10th the lead content as todays 100LL and why I add caution to running it full strength. Technically you can probably run it 2 gallons of 100LL to a tank fill of pump gas and you'll have the lead and octane you need.

My current plan when I get back to cruising my 'Bee is to carry a couple cans of 100LL and add 2 or 3 gallons before each fill up.

[XH29N0G]

Have another question/observation related to winter gas and thought I would put it in a thread to see if it was just me or more common.

I have been monitoring A/F and notice in winter the need for a different accelerator pump cam and jets, but thought that was due to colder air.  Yesterday was in the 70's and I had a chance to run it up through the gears and it read lean by about a point.  I see one place Wikipedia where it is mentioned that it is winter gas that forced the jet change.  Is this others's understanding?

[1974dodgecharger]

Have another question/observation related to winter gas and thought I would put it in a thread to see if it was just me or more common.

I have been monitoring A/F and notice in winter the need for a different accelerator pump cam and jets, but thought that was due to colder air.  Yesterday was in the 70's and I had a chance to run it up through the gears and it read lean by about a point.  I see one place Wikipedia where it is mentioned that it is winter gas that forced the jet change.  Is this others's understanding?

I personally change my squirters and nozzles to make it a richer initial....the gas is slower in the winter due to the dense cold air is my guess.  Though im so rich right now at 11 to 1 I need to back off the squirters on initial pump shot then at cruising im 13.5 to 1 average.