PART 2: AV gas in a turbo 2 stroke:

[TheBreeze]

LOL. I found that same post in my "fuel research" I have been conducting. There is a lot of info out there. Sunoco 110 really stood out to me (not necessarily in a good way" do to evap numbers that are way out of line in the 90% and final evaporation numbers. I could not find another race fuel that was even close. Ill call Sunoco and find out if they think the numbers are innaccurate.

Do you know the typical MON of 93 non ethanol pump? Where are you getting your pump gas infromation from? I would love to check out the sites if for no other reason than to learn.

 

[mountainhorse]

Pump gas info from the local cardlock manager's tech sheets.

I called Sunoco a while back and got a talking head that assured me that the specs on the site were correct... Never got to an actual engineer that would have the straight answer.

I really do not see any way for the EP to be that high.

What is it that you are looking for or to do??

 

[TheBreeze]

I am just trying to learn more about fuels and their composition. I started to read a lot of threads and articles about what fuel to run, etc, and as is often the case, there is more opinion, and unsubstantiated arguments, IMO than there is true conclusions or imformation based on fact and experience. Other times it is hard to differrentiate between the two.

 

[mountainhorse]

Keep digging my friend.... you will find what you need.

In the end... with all the variables... the only way to tell is to try it on YOUR equipment...in YOUR terrain.... The way YOU like to ride.

Good luck in your quest!

 

[Boyko]

I can get it here in Alberta for 1.46 per litre, .

thats cool......... were I needed some tonight?

 

[Eli]

From my digging, it looks like minimum spec for 100ll MON is 100.5 atsm 2700, with some FBO's testing toward the 104MON range. So can we count on 104MON from 100LL?....not sure. I picked up two barrels of Sunoco 110 and after looking a little further into the distillation numbers, I am wondering.

This year, I am adding two degrees timing retard and 106MON instead of 104 or possible lower and hoping to get 2-4lbs more boost. Previously on straight 100ll at 5-6k feet, I was running 13lbs with absolutely no deto or intercooler. (fresh air intake). IMO, straight av is a pretty dang good performer.

 

[TheBreeze]

I spoke with an engineer at Sunoco Race Fuels regarding the distillation numbers if anyone is interested. The numbers posted above, and on their website are accurate. He agreed that the numbers are not typical compared to other race fuels.

He explained the main reason for this is due to "Refinery Alkylate" that is used as an ingredient in the Sunoco Standard 110 which accounts for the higher than normal 90% and E.P. evap. numbers.

The Sunoco Supreme 112, and Maximal 116 use a more refined version of refinery alkylate containing lighter hydrocarbons that brings the distillation curve more in line with the majority of other types and brands of race fuel.

I am not smart enough to determine if that is a good or bad thing, but I have chosen to use a 110 race fuel with a more typical distillation curve over the Sunoco Standard 110.

He also mentioned that the Sunoco Standard is blended in this fashion to create a distillation curve that is more similar to typical pump premium, than typical race fuel numbers.

 

[mountainhorse]

Thanks for that... Looks like the VP would have properties that lean towards better throttle response... but maybe a bit higher cyl temps.

Cooling Effect:
Cooling effect of the fuel is related to the heat of vaporization. The higher the heat of vaporization, the better its effect on cooling the intake mixture for a denser charge. This is of some benefit in 4-stroke engines, but can be a large source of gain in 2-stroke engines.

 

[Eli]

I am wondering if I need to man up and exchange the 2 barrels of Sunoco 110 for the 112. I would pick up 3 MON and have a better distillation curve. 3 extra dollars per gallon, though!

 

[TheBreeze]

After more reading, it sounds like 100ll is also a fuel that is rich in Refinery Alkylate, presumably causing the similar distillation curve to Sunoco 110. The high 90% evap and high end point is both a good and bad thing. The flatter curve of say Sunoco 112, or VP 110 or C12 MAY lend itself to better thorttle response, and more complete combustion than the Sunoco 110 and AV fuel, but from what I can tell, the higher 90% and E.P. would provide a valuable "cooling" affect when running on the ragged edge - which i think is what Mountainhorse is getting at the the above post.

 

[2XM3]

OK , all this data is based on 25 years of dyno testing in my shop (probably 1000+ engines) All 4 stroke from 1.5 ltr to 800 inch pro mods.

Anyhow av gas is a very good fuel, the "dryness" is the fact that it is a bit rough on hoses ect, we always added a touch of redline to it and problem gone.
It has lead, and thats a good thing.
In many back to back dyno pulls I have found that 100% av will take as much boost as VP C12 , the max we found is aprox 14 psi @ 3000 ft running 9-1 static compression. C12 (green)would take 15 psi before the det sensors(4 head and 2 block) picked up anything. So my gut feeling in a 2 stroke is at altitude you could run 14 pounds with 100% 100ll.
Now that being said in a normally asperated engine we saw detontation creep in around 12.4-1 with 100% ll, vp C12 started at aprox 13.5 -1 so the av works a tad closed to vp/torco/112 ect in a boosted application.
The Low rpm/high altitude ect ect ect rap on av gas is garbage IMHO.

Now for higher boost the VP C16 is the best fuel we ever found, 25+ psi with zero issues, and for normally asperated motors, VP C14 (yellow) is very hard to beat for responce and peak HP its a great fuel. C 16 (dark blue) works better as the boost pressure increases but does not work well in a n/a motor, just for the high boost. VP C25 also is quite good with N/a motors.

The old (green) av gas 110/130 was really great, and the 115/140(purple) even better.

In any engine the closer you can get to the detonation point the more HP you will make, ANY extra octane is hurting power, throttle responce ect. 2 strokes are very sensative to this point. We have done 2.5 mercury drag motors for marine use and for max hp run them right on the limit for the elevation we raced at.

So bottom line treat 100ll av gas as 100mon fuel, blend for your proper octane and it will in fact work GREAT. Just like any fuel cross the line and your engines toast.

Last year we as always tested the local pump gases (91 non eth) and found as usual they pretty much were all crap, some as low a specific gravity as 35-40 !!! Av tested at 64 c12 at 65-67 and c14 at 70 c 16 at 72+ on that day using our spec grav tester.

Well thats my story and i'm stickin to it......hope it helps somewhat.

Oh one last thing, for the money av gas can not be beat as a good higher octane fuel...yes race gas is somewhat better but its not 6 bucks a gallon better unless your racing for money..lol

 

[SSWIM]

OK , all this data is based on 25 years of dyno testing in my shop (probably 1000+ engines) All 4 stroke from 1.5 ltr to 800 inch pro mods.

Anyhow av gas is a very good fuel, the "dryness" is the fact that it is a bit rough on hoses ect, we always added a touch of redline to it and problem gone.
It has lead, and thats a good thing.
In many back to back dyno pulls I have found that 100% av will take as much boost as VP C12 , the max we found is aprox 14 psi @ 3000 ft running 9-1 static compression. C12 (green)would take 15 psi before the det sensors(4 head and 2 block) picked up anything. So my gut feeling in a 2 stroke is at altitude you could run 14 pounds with 100% 100ll.
Now that being said in a normally asperated engine we saw detontation creep in around 12.4-1 with 100% ll, vp C12 started at aprox 13.5 -1 so the av works a tad closed to vp/torco/112 ect in a boosted application.
The Low rpm/high altitude ect ect ect rap on av gas is garbage IMHO.

Now for higher boost the VP C16 is the best fuel we ever found, 25+ psi with zero issues, and for normally asperated motors, VP C14 (yellow) is very hard to beat for responce and peak HP its a great fuel. C 16 (dark blue) works better as the boost pressure increases but does not work well in a n/a motor, just for the high boost. VP C25 also is quite good with N/a motors.

The old (green) av gas 110/130 was really great, and the 115/140(purple) even better.

In any engine the closer you can get to the detonation point the more HP you will make, ANY extra octane is hurting power, throttle responce ect. 2 strokes are very sensative to this point. We have done 2.5 mercury drag motors for marine use and for max hp run them right on the limit for the elevation we raced at.

So bottom line treat 100ll av gas as 100mon fuel, blend for your proper octane and it will in fact work GREAT. Just like any fuel cross the line and your engines toast.

Last year we as always tested the local pump gases (91 non eth) and found as usual they pretty much were all crap, some as low a specific gravity as 35-40 !!! Av tested at 64 c12 at 65-67 and c14 at 70 c 16 at 72+ on that day using our spec grav tester.

Well thats my story and i'm stickin to it......hope it helps somewhat.

Oh one last thing, for the money av gas can not be beat as a good higher octane fuel...yes race gas is somewhat better but its not 6 bucks a gallon better unless your racing for money..lol

You know you are going to get the "this guy says this and that guy says that".

I fully agree with your post. I have been running AV gas in my turbos for years. Elevation 10k-13k. TAPEX, 18-22lbs. TM1200 Tial, 14-18lbs. TM8 Tial, 16-18lbs. Just a few #s. Have had great luck with the AV gas.

Sam

 

[2XM3]

interesting at the high elevation and ur boost level, the numbers do in fact support those levels of boost. at denver we ran upwards of 60 psi in the promod on alky,pomona maybe 45 ish at best.

Yeah i'm always the guy who said that and this lmfao

Best way to tune a race engine is lean on it till ya put the rods out about 50 feet before the finish line then back it down 1 tooth on the pulley so it lets go 50 feet after the finish.................hahahahhahahaha

 

[SSWIM]

Don't you just love the "guy" that puts C16 in their sled, that was set up for 87 Octane (ie. 09 M8s), and expects good results.

Yep, right to the point of rattle and then she is ready to rock & roll.

Sam

 

[mountainhorse]

2xm3.

Sincere questions... with much respect for your background.

How much dyno time on 2 stroke turbos?

What criteria did you use to evaluate the throttle response "character" of different fuels?

 

[2XM3]

On 2 stroke mercury race engines 5 motors, 4 stroke...lol...maybe 1000+ at least... My good friends shop builds nothing but 2 strokes,n/a and turbo..hes done maybe 300 motors. You find after years of testing that all motors tend to perform very similar with respect to fuel, air temp, ect ect. We even did a couple of turbo mazda rotary motors (strange beasts) I did a huge amount of dyno time on blown gas deals, we had the fuel octane dialed in pretty good after 20 years. You can actually figure out the aproximate required octane needed if you know the true running compression on a engine, Quick and dirty formula for this is:
Final Compression Ratio (FCR) = [ (Boost÷14.7) + 1 ] x CR for sea level Note: the (+1) is dropped when boost and atm pressure are >1

Where cr is true static compression,14.7 is atmosphereic pressure at sea level. (final compression numbers have NO corelation to static compression numbers ie 12-1 FCR noes not = 12 -1 static !




Now Air pressure above sea level can be calculated as (just use a chart..lol)


p = 101325 (1 - 2.25577 10-5 h)5.25588

where

p = air pressure (Pa)

h = altitude above sea level (m)


final compression can be determined and octane needed can be picked. Now its important to remember that the number you get for final compression does NOT in any way compare to the "normal" number you see for static compression, ie 12-1 does not = fcr 12-1. This is only used as a ballpark # to see where you are at. Many things play into effect here, ignition,intercooler,port timing.exhaust flow, ect ect ect but as a starting point a FCR of 12-1 is good for 91octane, somewhere around 16 to1 for 100ll or C12, above that C16 or C25 till about 25-1+ where things get touchy...lol..

So for our motor at sea level running 12 pounds of boost and 12-1 true static(polaris dragon 800) whats are running compression? well:

[ {12.0 / 14.7} +1] x 12= 21.7 to 1 running compression under load

now same engine at 10000 feet

[{12.0/ 10.245}] x 12 = 14.00 running compression (10.245 is atm at 10,000 ft)

So we see that 12 pounds SHOULD be safe at 10,000 feet on 100ll blend and at sea level better have some C16 in it.

Is it safe? well we now look at what guys are running, ummm , many running 12 pounds boost on 100ll with no issues so we conclude by our formula and real world data that is should be OK.

Remember THIS IS A STARTING POINT ONLY. THERE IS NOTHING AS ACCURATE AS YOUR OWN PLUG READING,EGT'S,PISTON WASH,BURN PATTERN,AFR ECT ECT TO DETERMINE OCTANE REQUIREMENTS. Different chamber and about 1000 more things...Every motor has its own requirements and you learn what to do by years of experience and testing. NEVER put a motor near the "edge" unless you are totally willing to accept the FACT that it can melt to the wrist pins in a split second no matter what/who is tuning it thats just a fact when pushing the limits. Thats why I don't get to upset if I blow the rods out the bottom of the block...$hit happens or as they say "thats racin bub" lol.

Other guys figure all this different ways, first thing you learn in engine building is that nothing is the same..lol...and only trust your own data..are others correct?? Maybe, are there methods better? Maybe, the only thing I ever cared about is who's kissin the trophy girl at the end......................................







The "snappyness" of a motor you can tell pretty easy on the dyno fron the rate of acceleration over a given load, ie, the computer on the dyno is programmed to apply a fixed load over a time interval, then you can see how long the test engine takes to accelerate this load to the spectified rpm.
Or the dyno can be set up to give you a reading of how fast it has to open the water break in order to hold the motor, then apply this data to a acceleration curve you can look at.
Before we had all this computer stuff to control the break (way back when) you operated the brake with a wheel, primative as it sounds it was pretty easy to feel how fast the motor gained rpm by how fast I would have to apply the load...lol...and let me tell ya you crank that baby pretty dang quick on a blown alcohol deal..hahaha.

 

[2XM3]

On a side note I'm wondering in a turbo 2 stroke how small I can make the volume of the expantion chamber in order to speed up the spool of the turbo and help lag? anybody messed with this at all? On a turbo 2 stroke what would it run like if you used a 5 inch long straight pipe from head to turbo? wondering if it still would run or not?? Just a crazy idea...ummmm time to bend some pipe I think...hahahah


Mountain : your makin me think to much, and people wonder why I had trouble sleeping when I owned my race shop....arghhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh !!!!!!!!!!!!!

 

[2XM3]

heres a good chart

http://www.smithtex.com/racing/fuelcomp.html

 

[mountainhorse]

On a side note I'm wondering in a turbo 2 stroke how small I can make the volume of the expantion chamber in order to speed up the spool of the turbo and help lag? anybody messed with this at all? On a turbo 2 stroke what would it run like if you used a 5 inch long straight pipe from head to turbo? wondering if it still would run or not?? Just a crazy idea...ummmm time to bend some pipe I think..

2XM3... Your background sounds pretty extensive and I appreciate that you take the time to make your presentation here.

As far as the "tube" thing... that has been tried... with less than even poor performance. This scenario could be possible if the intake was always under positive pressure.. but this is not the case in our sled turbos.

Read last years thread on 2 stroke turbo pipes for a good discussion on this topic.

Two stroke turbo dynamics throw it all out the window... especially when you consider it is a reed valve induction system. The scavenging effects of the pipe still play a major role.

Also, this is something that many forget about... turbos are not a tool for merely compressing air.. they are to provide more oxygen so that you can burn more fuel to increase the output of the engine. Pressure calcs are useful but when you are considering altitude variations.. you also need to include the diminished oxygen content per given volume of air available...ie,10 psig of say, 1 cubic meter of air at sea level will have less oxygen content available than 1 cubic meter of air at 10psig at 5,000 ft altitude. The same engine at sea level will make more power at a given boost level than that engine at higher altitudes at the same boost.

"Tickling deto" in an engine is surely a way to win races/trophies... but running on that edge is hard on the engine in terms of durability and flexibility in the hands of the average consumer that might purchase a turbo for their two stroke turbo (the purpose of this thread).

Deto is not the only thing to consider.

There are a lot of people that ride or read here that more power is better.. but how that power is made, how it "comes on" in the sled, etc is good. If you are not an elite level rider and are pushing for 12 plus pounds on a sled... well you may just have more than you bargained for (not trying to hurt any egos with this one).

There was a reason why Curt at FasTrax prefers the 700cfi in a turbo sled...It was "character" of the

Snappiness on a dyno and true throttle response through the drive-train to track when constantly cycling through negative intake pressure (vacuum) to positive up through the scavenging harmonics that happen in the pipe. A true "throttle-jockey" in the trees, operation at a high % of load will notice things riding the sled that you would never be able to notice in a dyno cell.

I have personally felt very noticeable differences in throttle response between brands of gas or even different formulations from the same mfg...in the same machine on the same day in the same area.

The evap and RVP stats on most race gas favors race/pump mix in terms of throttle response... Is it that noticeable with av gas... well, the ONLY way to tell is to ride it and see what you think using diff fuels on the same day.

The numbers on the Sunoco 110 should make it a bit more resistant to deto than VP... the VP should show a bit better than the Sunoco for those that really need the throttle response in super technical boondocking.

If you are drag racing up a hill, or pulling a long chute.. you really can use all the "max power" mind set.. but, If you are honest with yourself and your needs, you will find than very few riders out there fall into this category.

One of the biggest challenges that I see is for those that want to run more boost than true "pump premium" can tolerate. That on top of the fact that the ethanol in our gas (I've personally tested north of 20% in what was supposed to be limited to 10%).. and the overall quality of the gas and the possibility of water in the gas.... can cause lots of frustration. There are more areas that DON'T have ethanol free gas than DO.

In the mountains (for the most part)...
For those in the 8+ lb boost levels, there is a dilemma... mixing good quality, clean race/AV gas with crap E10 (or worse) is an issue for sure.

As said in posts above (1st page), running too much octane will not give you good running character in your sled... at 10 lbs, you will be over-octane if you run straight race fuel or AV gas... If you mix it, you bring ethanol into the equation. At that point you need to turn up your boost to minimize this effect.. but will still magnify the over-octane "blues" when manifold pressure is negative or low for low speed maneuvering.. this creates a powerband that is peaky & cumbersome at best

For most (including me) the running character of a turbo 2-stroke that is not "fussy" or quirky, giving good low speed response tapering smoothly into the boost range without a big spike in power AND being reliable and tolerant of altitude changes and fuel inconsistencies... is more important than having a sled that has the most power. (there are some that max pow IS the goal though, I will admit)

Finding the "balance", as with anything in life, is the challenge here.

For the mostpart... for most turbo 2 stroke owners... AV gas represents a very good value, IMO, with only small draw backs.

 

[2XM3]

There are a lot of people that ride or read here that more power is better.. but how that power is made, how it "comes on" in the sled, etc is good. If you are not an elite level rider and are pushing for 12 plus pounds on a sled... well you may just have more than you bargained for (not trying to hurt any egos with this one).


A truer statement has never been said....well put !!

I would agree totally that 100ll is by far the best value for the money in higher octane fuel.

If you can't decide what fuel to run after reading this thread, well just leave it stock...lol