Fuel Recommendation

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randy331
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Re: Fuel Recommendation

Post by randy331 »

KnightEngines wrote: Thu Apr 26, 2018 2:09 am Avgas fits the bill for quite a few purposes despite not being an 'ideal' race fuel.
Exactly, and the engine this thread is about is one of those engines. It'd run fine on 100LL avgas and be much less than barrels of fuel from vp.

I've ran it before against vp110 on engines in this comp range and found no difference on the dyno.

Funny thing is, that pump fuel that gets bashed on these threads is certified to be run in a lot of airplane engines. Imagine this, we were flying a Cessna out in CO. last summer, and we made it over the continental divide burning,.... Gasp,... pump gas. Wow what a risk we were taking, flying along at 14000' burning gas made for low altitudes. And then to imagine I ran 6.00s at 330' elevation burning 100ll.

I know, it wasn't optimal for either. LOL

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Re: Fuel Recommendation

Post by cjperformance »

randy331 wrote: Thu Apr 26, 2018 10:16 pm
KnightEngines wrote: Thu Apr 26, 2018 2:09 am Avgas fits the bill for quite a few purposes despite not being an 'ideal' race fuel.
Exactly, and the engine this thread is about is one of those engines. It'd run fine on 100LL avgas and be much less than barrels of fuel from vp.

I've ran it before against vp110 on engines in this comp range and found no difference on the dyno.

Funny thing is, that pump fuel that gets bashed on these threads is certified to be run in a lot of airplane engines. Imagine this, we were flying a Cessna out in CO. last summer, and we made it over the continental divide burning,.... Gasp,... pump gas. Wow what a risk we were taking, flying along at 14000' burning gas made for low altitudes. And then to imagine I ran 6.00s at 330' elevation burning 100ll.

I know, it wasn't optimal for either. LOL

Randy
Pffrt .. just pure luck that the magic pixies were off gaurd that day !
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Re: Fuel Recommendation

Post by randy331 »

cjperformance wrote: Thu Apr 26, 2018 10:27 pm Pffrt .. just pure luck that the magic pixies were off gaurd that day !
Probably be better if we would put pump gas in one wing for takeoff and avgas in the other wing for "high altitude" flying, and switch tanks when the altimeter started showing we were at "high altitude" , but with all that big difference from pump fuel to avgas we didn't figure we'd have time to get it all re-tuned for the other fuel,... before we hit the ground ! :)

But we were taking off from Salida CO. so maybe were already at "high altitude" ??

Where exactly does "high altitude" start , and low altitude end ?

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Re: Fuel Recommendation

Post by GARY C »

randy331 wrote: Thu Apr 26, 2018 10:46 pm
cjperformance wrote: Thu Apr 26, 2018 10:27 pm Pffrt .. just pure luck that the magic pixies were off gaurd that day !
Probably be better if we would put pump gas in one wing for takeoff and avgas in the other wing for "high altitude" flying, and switch tanks when the altimeter started showing we were at "high altitude" , but with all that big difference from pump fuel to avgas we didn't figure we'd have time to get it all re-tuned for the other fuel,... before we hit the ground ! :)

But we were taking off from Salida CO. so maybe were already at "high altitude" ??

Where exactly does "high altitude" start , and low altitude end ?

Randy
Would you have to switch tanks on a mid altitude high bank turn if said wing dips below altitude? :)
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Re: Fuel Recommendation

Post by cjperformance »

randy331 wrote: Thu Apr 26, 2018 10:46 pm
cjperformance wrote: Thu Apr 26, 2018 10:27 pm Pffrt .. just pure luck that the magic pixies were off gaurd that day !
Probably be better if we would put pump gas in one wing for takeoff and avgas in the other wing for "high altitude" flying, and switch tanks when the altimeter started showing we were at "high altitude" , but with all that big difference from pump fuel to avgas we didn't figure we'd have time to get it all re-tuned for the other fuel,... before we hit the ground ! :)

But we were taking off from Salida CO. so maybe were already at "high altitude" ??

Where exactly does "high altitude" start , and low altitude end ?

Randy
High altitude starts at the top of the hill, low altitude ends once your feet get wet ! :lol:
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Re: Fuel Recommendation

Post by randy331 »

GARY C wrote: Thu Apr 26, 2018 10:53 pm
Would you have to switch tanks on a mid altitude high bank turn if said wing dips below altitude? :)
You'd certainly want to turn in a direction that kept the wing with high alitude fuel the highest.

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Re: Fuel Recommendation

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cjperformance wrote: Thu Apr 26, 2018 10:55 pm High altitude starts at the top of the hill, low altitude ends once your feet get wet ! :lol:
LOl

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Re: Fuel Recommendation

Post by groberts101 »

randy331 wrote: Thu Apr 26, 2018 11:16 pm
GARY C wrote: Thu Apr 26, 2018 10:53 pm
Would you have to switch tanks on a mid altitude high bank turn if said wing dips below altitude? :)
You'd certainly want to turn in a direction that kept the wing with high alitude fuel the highest.

Randy
Wouldn't you just eventually end up right back where you started from, have to refuel and then end up doing it all over again?

Or better yet.. maybe just alternate which wing gets what fuel at various airports along the way till you eventially zig zag your way back home?
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Re: Fuel Recommendation

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groberts101 wrote: Thu Apr 26, 2018 11:23 pm
Wouldn't you just eventually end up right back where you started from, have to refuel and then end up doing it all over again?
No, to make a 90* left hand turn, you make a 270* right hand turn.

It's all right there in the FAA approved " how to fly when transitioning between high and low altitudes " manual. :D

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Re: Fuel Recommendation

Post by tresi »

Where does low altitude end? Been a long time but doesn't pump gas STC's end at 10,000ft?
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Re: Fuel Recommendation

Post by David Redszus »

One major problem faced by those of us who were in the fuel blending/design business is the racing community's
persistent use of fuel octane numbers to select fuel blends. This is unfortunate since it is quite misleading and
provides only limited information.

Suppose we take an unleaded blend with a MON OF 100, run it on the dyno, and note the torque curve.
Then we add 2 g/gal of TEL to the fuel to raise the MON value to 113, and repeat the dyno test.

What will the difference in performance be? Will we need to change jetting? Ignition timing?
The distillation temperature curve will remain unchanged as will mean boiling point, auto ignition
temperature, vapor pressure, specific gravity, stoich value, and heat of combustion.

Nothing changes except fuel octane and that includes the torque curve.
To get more performance we have to raise compression or turn up the boost.

On the other hand, we could select two fuels with identical octane numbers but all the other values
mentioned above being different. Now everything changes including the torque curve.

Remember that AvGas is often run excessively rich for take-off which can raise MON from 100 to 130.
The same can be accomplished with pump gas or any race gas. But the pilot quickly goes back to a
normal A/F mixture to save the engine from carbon build-up, oil sump dilution, and burnished cylinder walls.

The single most important rule in fuel selection is: GIVE THE ENGINE WHAT IT WANTS.
Pay no attention to pit lane folk lore, marketing claims, or engine builder poo poo.

Any fuel selected must be optimized for mixture and timing under the conditions of actual operation.
The problem facing amateur racers is that they do not know what fuel they actually have. Only lab
testing can verify which fuel was actually delivered. I can't tell you how many times a drum was mislabeled
or the wrong dye color was used; not to mention drum contamination and incorrect mixing.

Playing with fuels is not for the faint of heart or weak of wallet.
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Re: Fuel Recommendation

Post by GARY C »

randy331 wrote: Thu Apr 26, 2018 11:43 pm
groberts101 wrote: Thu Apr 26, 2018 11:23 pm
Wouldn't you just eventually end up right back where you started from, have to refuel and then end up doing it all over again?
No, to make a 90* left hand turn, you make a 270* right hand turn.

It's all right there in the FAA approved " how to fly when transitioning between high and low altitudes " manual. :D

Randy
That explains why flights are so long and stop overs seem to be out of the way.
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