• Don't miss out on all the fun! Register on our forums to post and have added features! Membership levels include a FREE membership tier.

110 fuel or 100LL

880summitxrs

Active member
Lifetime Membership
Aug 1, 2009
199
31
28
I can get either fuel close to home but was wondering wich one would be better to run. I'm running 7lbs on a Silber kit. Thanks
 

rmk all the way

Well-known member
Lifetime Membership
Nov 29, 2007
642
158
43
Dayton Wa
I always ran 100ll in my xm turbo, my 850 turbo I’ve been meaning to mix with pump gas but at 4.50 a gallon it’s just as easy to top off sled and head up. 100ll is way more constant and better regulated the race gas


Sent from my iPhone using Tapatalk
 
F
Nov 27, 2007
2,495
712
113
medicine hat
Been running 100 av gas for years now, very consistent like other said and I been running up to 10 lbs boost with out problems.. I buy it at the airport and have storage in the trailer for it.. Works well for me
 
J

JJ_0909

ACCOUNT CLOSED
Nov 16, 2009
1,023
1,033
113
Most of our testing is done with an AV gas mix. For most applications, its the best bet, especially south of 10psi.

Its consistent, its super stable for long periods of time, its relatively cheap, burns cool - its good fuel.
 

mountainhorse

Well-known member
Lifetime Membership
Premium Member
Dec 12, 2005
18,606
11,814
113
West Coast
www.laketahoeconcours.com
OCTANE IN A MIX... AND AV GAS/PUMP 91/RACE GAS.

Some info on AV and Race relative octane levels.


AV-GAS... 100LL is rated "100" on a special Aviation octane rating... and the 100 relates to a "lean mixture rating"
NOT AT ALL similar to motor fuel (road) ratings.

The "LL" relating to Low-Lead (low tetraethyl lead content, not to exceed .56grams/liter.... much lower than typical 110 race fuel):face-icon-small-coo

100LL has a MOTOR OCTANE NUMBER (MON) of approximately 103. This will give a more accurate comparison for an "apples to apple" snapshot of this fuel compared to other motor fuels.

By comparison.

Sunoco 110 has a MON of approx 105. With a lead content of approx 4.0grams/Liter.


There are many different characteristics of the fuel, eg Reid Vapor pressure, specific gravity, evap temps etc.... Octane IS important, but only a small snapshot of the whole picture....But for this conversation in this thread... not really necessary since we have all had great reports of all of these fuels for use in our sleds over the years.... no need for an argument of these points for this discussion IMO.

Although I hate to use etanol pump fuel for mixing (for my own reasons), in my area... and many others, it is the only option... (and, yes, there are some that are blessed with non-eth in certain areas :face-icon-small-ton)

Using 100 as the octane number of AV-GAS, 110 for typical race fuel and 91 as your octane number of Premium pump fuel will NOT give you an accurate idea of the octane rating of mixture.

To Calculate fuel octane in a mix of two different fuels... you must first make sure that you are using the SAME OCTANE rating.... MON is a good place to start.


100LL MON = 103 MON (approx)
91 'Premium' Pump fuel with 10% ethanol = 88 MON (approx)
110 Race fuel typical = 105 MON (approx)


Those would be much better numbers to use with the following formula to determine your mixed octane number relative to the BASELINE of typical 91 pump fuel. Note that Non-Ethanol "Pump-91" fuel will have a slightly lower MON of approx 87 MON due to the increased octane of the added Ethanol.


( [ % Fuel A ] x [ Octane of Fuel A ] ) + ( [ % Fuel B ] x [ Octane of Fuel B ] ) = Octane of Mixture

For example... a 50/50 mix of typical 100LL to 91(10% eth) 'pump'.... would give you approximately 95 MON in your end mix.
[Lower than the 103 MON of the AV-GAS and higher than the 88MON of the 'premium' pump fuel.]


( [ .50 ] x [ 103MON ] ) + ( [ .50] x [ 87MON ] ) = 95MON


Also, as a side note... the word "PREMIUM" fuel has ZERO to do with the QUALITY of the fuel within a brand.... It is just a industry name that refers mostly to the Octane number of the fuel.

It is easy to LOSE performance...both in overall max power & throttle response ('torquieness' and throttle 'character') by using too HIGH of an octane.

Pump gas will, for our intents and purposes in mountain sledding, have better throttle character for our uses than 100LL... and that is not simply related to Octane ratings.
This is the reason I'm an advocate of MIXING pump fuel to 100LL to get the right blend for your uses....

Since MOST turbos sold today are lower boost (sub 8 lbs psig, on sleds used above, say... 5K feet ).... you are losing performance using straight 100LL in a given sled... and mixing 100LL with Pump fuel will optimize your smile factor and get the most out of what you paid dearly for (sled and kit... and time off work !!)

You need to do your research...a little trial and error...or talk to people with the SAME sled/kit as you have... and, find the mix for you for the elevation and boost levels you are riding... To enjoy what you have !


Hope this helps.

My 2¢






















.
 
Last edited:
J

JJ_0909

ACCOUNT CLOSED
Nov 16, 2009
1,023
1,033
113
Some info on AV and Race relative octane levels.


AV-GAS... 100LL is rated "100" on a special Aviation octane rating... and the 100 relates to a "lean mixture rating"
NOT AT ALL similar to motor fuel (road) ratings.

...everything here is right











.


MH nails it on this one.

At Silber we really suggest everyone "over octane" for reliability, and because pump gas isn't as consistent location to location as we'd all like to believe.

That said, if you don't mind a little playing around, you will find better throttle response and more power if you can run the lowest octane possible for your application.

Keep in mind, octane requirements, especially in a non-intercooled turbo application, will change as the environment changes (temperature). Turbos get hot. Charge temps get hot. Sometimes a bit extra octane, especially in the form of 100LL, can be the magic bullet to keeping your motor happy. It burns a bit 'colder' than a lot of the fuel out there.

Anyway. There ya go.
 

WyoUltra

Well-known member
Lifetime Membership
Nov 26, 2007
566
58
28
Casper, WY
I was under the impression, or at least read that, when using 100ll it is best to mix with 91. The main reason being is that because the 100ll burns colder and different when compared to your typical 91, it can give a sluggish or less snappy throttle response. Mixing with 91 helps prevent that because it does burn hotter, and you end up with a safer fuel for your turbo sled that you don't have to worry about detonation so much. Can anybody confirm this??
 

mountainhorse

Well-known member
Lifetime Membership
Premium Member
Dec 12, 2005
18,606
11,814
113
West Coast
www.laketahoeconcours.com
Wyo,

Read this thread, start-finish, for more technical info...https://www.snowest.com/forum/showthread.php?t=220800

In short, 100LL WILL run a bit cooler combustion temps.

My experience with turbos and 100LL is that the mix gives better/snappier throttle response compared to straight 100LL (103MON).

And, IMO, straight 100LL is really "over octane" for most turbo applications (running 8 psig or less, above 5k feet)






.
 
S

sledsrock

Well-known member
Nov 26, 2007
1,826
510
113
Grand Junction, Co.
Aromatics

Lazy throttle response can often times be attributed to a fuel that is high in Aromatics, which 100LL does have. In some motors it’s more noticeable.
 
Premium Features