Does the Octane rating influence cold starting?

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2015: Does the Octane rating influence cold starting?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Weeds on Thursday, August 27, 2015 - 07:34 pm:

While experimenting to get better hill power I noticed the following. I normally run 91 unleaded, (26 Speedster, standard everything, Holley NH). Brilliant starter when warm/hot but often takes a lot when really cold and the process has to be dead right. Three days ago there was 2 gallons left in the tank and I filled to the brim with 96 octane unleaded to compare power on my test hill.
What I have noticed is the last two morning since it starts pretty much straight up from cold? Bit soon to tell for sure plus the weather is slightly warmer the last few days but has anybody else found this? I wonder if an Octane booster or other additive would give the same result?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hap Tucker in Sumter SC on Thursday, August 27, 2015 - 08:56 pm:

Kevin,

I wonder if the 2 vs 10 gallons in the tank makes any difference? Does your 1926 speedster have the stock 1926 tank in the cowl or was it relocated to the rear of the car?

Clearly for a hill if the tank is in the rear it can impact how the car runs or even stalls. But does having the extra head pressure make any difference on a flat garage/driveway surface? And especially if you have a 1926-27 style tank in the cowl?

Also, you didn't mention if the car does or does not have an inline fuel filter or not.

Note a quick Google search had one opinion that the lower octane would start more easily in the cold than the higher octane. See: http://www.newsday.com/auto-doc-why-higher-octane-causes-hard-starting-1.756847 where Junior Damato an accredited master automobile technician, radio host and writer for Motor Matters who also runs his own 10-bay garage near Boston made that comment.

Note the few newer car manuals I remember reading said using the higher octane when the engine was designed for the lower octane would not make any significant advantage -- and would only cost more.

All my Ts and As have started better when it is warmer rather than colder -- but they still start OK when it is cold (ok -- cold for South Carolina -- that might be considered "HOT" in some other locations. So if it is below freezing (0 C or 32 F) -- that is colder than I normally deal with).

Respectfully submitted,

Hap l9l5 cut off


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Thursday, August 27, 2015 - 09:38 pm:

Octane over about 80 does not have any benefit to a stock Model T. Fresh gas is far better than stable gas..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Weeds on Friday, August 28, 2015 - 01:12 am:

Hap I have been experimenting with a 6v fuel pump. Car still has a cowl tank but there is two in line filters plus a pressure regulator so as far as getting the fuel to the carby its exactly the same running, on a hill or primed ready to start.
Temp difference, 2 deg compared to 6 deg C, not that much different.
Royce maybe it was just due to the fact 80% of the gas was fresh?
I'll keep testing each day and when it gets low I'll go back to fresh 91 to compare, could be the only way to prove for sure.
Ever since unleaded crap was introduced I've never used anything else but 91 Oct in all my cars, bikes, mowers etc no matter how old, 96 is just a waste of money. But it is so nice to hear her fire up after a few winds instead of 10 - 20 winds.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Friday, August 28, 2015 - 02:04 am:

To raise the octane rating of gas an additive to make it burn slower is added.
An additive to increase the resistance to burning.
How can that make an engine start quicker.
Everybody knows there is more energy in a pound of regular than in a pound of high test.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Friday, August 28, 2015 - 02:09 am:

Why do folks say, "92 unleaded, 96 unleaded, regular unleaded, supreme unleaded"?
Is there some place in the U.S. where you can still buy gas with lead in it? Isn't all gas unleaded?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Weeds on Friday, August 28, 2015 - 03:42 am:

We can still buy 120 octane Av gas (leaded) fill a can for use in race bikes, go karts etc at some airports. Its more expensive but I'll try that next if I can source it.
I am just asking the question to see if anybody else has noticed the same.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, August 28, 2015 - 04:10 am:

There isn't any difference in energy content in various octane gas, the difference lies in the tendency to self ignite from compression. At the low compression we have in our T's, there shouldn't be any problems with pre ignition or knocking as long as the timing is set about right.
Higher octanes like 100 and over would only be needed with compression higher than 10:1 or more than you can use in a flathead engine.

Higher compression means more of the energy from the fuel is turned into work instead of heat & since all gas has better octane rating than the kerosene mix they sold during the 20's.

The best you can do to get better power in your old Ford is to raise the compression as high as the splash oiled babbitt can take with reasonable reliability or about 6:1.

An original low head gives about 4:1, an original high head 3.98:1. A "Z" or Prus head off the shelf gives about 5:1 and an instant 30% power boost.
I've milled my Prus head 0,100" giving 5.8:1 and I'm really pleased with the hill climbing power in my primitive pickup. I don't care about hills much more than with my modern car, it's the sidewinds at 50 mph that takes both hands on the steering wheel ;)

And no, I haven't noticed any difference in the ease of starting with various fuels - I'm running 95 octane gas with maybe 5% ethanol and have tried a tank of E85 with the only issue that I ran out of it out in the boonies.. the ethanol didn't last as long as a tank of gas by far - as I should have expected (had a spare can, so no big issue)

(Message edited by Roger K on August 28, 2015)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn-Monroeville OH on Friday, August 28, 2015 - 08:44 am:

Aaron, and I love all the questions I get- "do you need to add lead to your gas"? I politely tell them there was no such thing as leaded gas until 1923...first sold in Dayton Ohio.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Friday, August 28, 2015 - 10:42 am:

Tim - I am happy to learn about lead in gas.


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration