Is anyone running 100 octane gas in there car? I used to buy it for my 911 (71T with carbs, 3.2 Max Moritz short stroke) with 100 ran like a turbo. Very smooth.
Original Post
Replies sorted oldest to newest
For the compression ratios almost all of us are running (typically, well under 10:1) I see no advantage to running 100 octane gas, other than you'd probably be able to lug it down under 2 grand in 4'th and it won't knock. while the 2332 is big, it sits at around 150hp and is detuned a bit to be more driveable so 100 Octane probably won't make a difference.
Totally agree, Gordon. I have 10.2:1, and I run 93 octane with 10% ethanol.
There is absolutely no reason to run more octane than is needed to prevent pinging for the amount of advance you're running. It's simply a waste of high-performance fuel.
The only actual reason is because of that great smell when it burns!
If you want to have a nice smell from the exhaust, just add a little, very little (1/2 cup to 15 gallons or about 360:1), 2-stroke Blendzall Green Label. If you are allergic to peanuts, maybe do not use, I am not sure of possible reactions. I just really love the smell, and a little top end lube can't hurt anything. I run a little in the lawnmower as well, makes cutting the grass smell like the old days of race day at the MX track. 
I run ethonal free 88 octane in my Spyder and it runs just fine. No pinging even when going up a grade at 2500 rpm in third gear.
My 968, with its knock sensors OTOH, I felt a real difference when I ran 50/50 100/93 octane premium.
I would like to try ethonal free but hard to find around LA. We used to mix toluene with 91 to up the octane, mix charts online. Toluene available at paint stores
If I remember correctly, Toluene wouldn't increase octane numbers. Only retard a dual flame front from causing detonation ? Could be off on this but there was some weird thing that it would cause.......Bruce
I feel like I'm always swimming upstream on this topic, but I'll never understand why guys want to run fuel that is not readily available everywhere in the country (or at least in the part of the country you might drive). The last place I want to be is with an empty tank, sitting in front of a pump which only has a fuel I can't use.
E10 93 is available almost everywhere east of the Rockies. E-Free 93 is available lots of places, but certainly not everywhere. Jetting and setting up the car to run optimally on E-Free gas means that it won't run optimally on E10. If your car is set up for E10 93 at 500 ft altitude, it'll run fine on E10 91 at 5000 ft (I've proven this with a 10.5:1 2276).
Ethanol has a much lower BTU content than gasoline, but it also has some characteristics beneficial to engines set up to use it. It cools the intake charge, and has killer knock-resistance. Yes, it's hygroscopic. Yes, it's corrosive. But "in the know" drag guys often set up for E85 as a kind of poor-man's nitromethane. An E85 motor can run crazy compression. An E10 motor can run higher compression than a motor set up for E-free fuel. If you want to be able to run both, you'll be rich with the E-free and lean with the E10. You won't be able to run as much compression with E-free-- and if you set up for it, you'll leave power on the table when running E10.
I can get 100 octane race gas 10 miles from my front door (for about $10/gal), or E-Free 93 in one station about the same distance away. What I can't guarantee is that I can get it in the Smoky Mountains, or in Laramie, WY, or Huntsville, AL or anywhere else I might want to drive my car. If I set up with 12:1 CR figuring I'm going to run race gas, I've pretty much guaranteed that I'll never leave my own hometown (which sounds antithetical to the Speedster Dreams I've got inside my own head).
As they say, your mileage may vary.
Mine won't.
I have the app but nothing close enough to make it practical to gas the car on a regular basis.
@R Thorpe posted:I have the app but nothing close enough to make it practical to gas the car on a regular basis.
See post above.
@Stan Galat posted:As they say, your mileage may vary.
Mine won't.
You're right. It does. I get 2-3 mpg better mileage in my Smart, 968, and ML's running Ethonal free. And I don't have to worry about deteriorating the hoses and gaskets in my Spyder, Evinrude, and Ducati.
And it's readily available here and only mildly inconvenient while traveling using the Pure Gas app. And despite all the old wives tales to the contrary, the sun will still come up tomorrow if I run a tankful of E10 through any of them. 
@dlearl476 posted:You're right. It does. I get 2-3 mpg better mileage in my Smart, 968, and ML's running Ethonal free. And I don't have to worry about deteriorating the hoses and gaskets in my Spyder, Evinrude, and Ducati.
That's because your Smart, 968, and MLs are all EFI and can optimize the ignition curve to squeeze the BTU content out of the E-Free fuel.
Your carbs and distributor can't do that.
@Stan Galat posted:That's because your Smart, 968, and MLs are all EFI and can optimize the ignition curve to squeeze the BTU content out of the E-Free fuel.
Your carbs and distributor can't do that.
My Spyder and Ducati are both tuned to run on E-Free.
@dlearl476 posted:My Spyder and Ducati are both tuned to run on E-Free.
But you can't get it everywhere. What works for you and your needs, Dave, is not necessarily applicable to the rest of Speedster/Spyder-dom.
I can get 91 octane ethanol-free 1/2 mile from my house. But I tune for what's available EVERYWHERE, which is 93 octane E10.
10.2:1, absolutely no detonation. And it RUNS.
@dlearl476 posted:My Spyder and Ducati are both tuned to run on E-Free.
@Stan Galat posted:I feel like I'm always swimming upstream on this topic, but I'll never understand why guys want to run fuel that is not readily available everywhere in the country (or at least in the part of the country you might drive). The last place I want to be is with an empty tank, sitting in front of a pump which only has a fuel I can't use.
I think we're approaching this from two different perspectives.
Let's assume you have an analog distributor and carbs, and everything is set up perfectly. Let's assume you built the engine to run right on the hairy edge (but still on the right side) of pre-ignition with E10 93. The engine can run an optimal ignition curve for the setup, but any more timing or compression and it'll knock. The engine may very well suffer pre-ignition running E-free 93 unless timing is pulled out of it, in which case the gains from the increased BTU content of the fuel is offset by the less than optimal state of tune.
Now, let's assume that the engine was built with a safety margin built in (as the vast majority of engines are). If the compression is a half-point less than optimal, using the E-free gas is the better option, because of the increased BTU content of the fuel.
I 've tended to push the limits with compression, because compression is free power. Most engines are not built this way, but modern EFI engines are-- and compensate with knock sensors and modified ignition curves for different fuels.
If you are running with this safety margin built in (less than 100% optimal static compression ratio), then running higher octane fuel won't make it run any better (which was the point of this thread before it became a holy war). Running a fuel with a higher BTU content will definitely make it run better. This is your perspective, and I respect it.
My perspective is that E10 91/93 fuel is available at pretty much every pump in the USA. I feel fine running that extra half-point of compression and not having to look around for special fuel. I understand I'll need to change my rubber bits more frequently, but there are additives I can use that help. If I ran an engine with less compression, I'd use the E-free fuel if I could find it, but I'm not always guaranteed I'll be able to.
It's all in the set-up.
When I spec'd my engine I had every intention of running available-anywhere 89 octane in it and didn't care much back then (later 1990's) whether the gas had ethanol in it.
Fast forward to today: I'm running 8.6:1 compression, a pair of 40mm Dells, a MagnaSpark set to 30º at 3,000 rpm (and the secret advance spring swap that Mitch Toll @Sacto Mitch recommended, since it was wicked easy to do).
I also use the @MusbJim approach: I buy pretty much whatever 89 octane I come across (except for el Cheapo or no-name gas.... You have to draw the line somewhere), I ALWAYS put the recommended amount of Startron stabilizer in it, screw on the gas cap, close the hood and never even think about it. Everything I see here in New England has ethanol in it so I really don't have a choice there. I have yet to see any crud from deteriorating fuel lines (which I swap out every 5 years and the mainline front to back is copper) or from the floats (which still look like new).
Once, I had a "senior moment" (I'm entitled to those these days) and pumped in a tankful of 87 octane. Oh, poop.... 
I didn't notice a damn thing different. I even tried lugging it a bit in 4'th gear just below 2,000 rpm and STILL didn't hear any knocking (even though "knocking" in these engines sounds more like cracking Walnuts, I still didn't hear anything).
If I was running over 10:1 comp. I might have other news to tell, but hey.... These are lawn mower engines, after all.
@Gordon Nichols posted:If I was running over 10:1 comp. I might have other news to tell, but hey.... These are lawn mower engines, after all.
Yeah, but they're FANCY lawn-mower engines, see?
The twin-plug motor was running 10.6:1, and had the cam advanced 3*. It ran phenomenally, but tailoring the ignition curve was very, very important. When I redo the engine, the cam will be straight up, and it'll have some sort of crank pickup trigger.
That motor needed E10 93/91. I had a "bad gas" program saved for the black-box, if I ever needed it.
I have the same, Stan. Flip a switch and retard the timing a few degrees with a second map.
.
Aw geez, I like the way the Ford Model A did it.
Just slide the lever and set the advance wherever you want:
.
Attachments
I treat ethanol gas the way I treat the milk in my fridge..use it up before it goes bad.
Here in Southern Indiana birth place of motor racing many local gas stations sell VP107 full lead race fuel. To run in off road vehicles and Chain saws only wink wink. The down side is price $7.00/gal. which I don't see as a problem if I have needed it for a hobby car. I have also blended this with 93 no lead to make 100 octane low lead which reduced the cost. We have it good here when it comes to available fuels. 93 octane is at every pump.
One of the stations where I buy E-Free is owned by a guy who's raced power boats since I was a little kid. (We used to have a huge race on our local lake on the 4th of July. Miss Bardahl and all those unlimited hydros and all).
I went in to grab some Techron the other day (E-Free has no additives) and noticed they sell VP 100 octane in 5 gal cans. $49.00. I think it's unleaded, though.
Hey Dan!'
Attachments
@MikelB posted:I treat ethanol gas the way I treat the milk in my fridge..use it up before it goes bad.
I can't remember if I posted this here or on one if my MC forums. If I'm repeating myself, I apologize.
One of the best attributes of E-Free is its stability. In years past, getting my Ducati out of hibernation used to be an all day affair. I'd drain the tank and put the gas in one of my cars, go get a 5 gal can of fresh gas, crank until the battery was dead, charge and repeat until it finally fired. Twice in my 15 years of ownership, it required replacing my float bowl ORings which had deteriorated to the point of gushing fuel and unsticking my needle valves.
Since I started using E-Free in it, I install the battery, which I keep indoors and charged in the winter, set the bike in the sun for 15-20 minutes, open the petcock, twist the throttle twice, and hit the starter. It usually starts on the second or third try.
I don't use any fuel stabilizer in it, although I do add Marvel to both the Spyder and the Duc fuel, when I remember. I've heard people say that acts as a stabilizer, but I have no proof it does.
I always stabilize the gas in my motorcycle, lawnmower, chain saw etc. Ethanol gas or not, it's fires right up in the Spring.
To square this circle, @dlearl476-- I absolutely drive wherever I have to for E-free gas to run in the eleventy-billion small engines around my place (mower, chain saw, tiller, edger, weed whip(s), post hole digger, compactor, leaf blower(s). I add fuel stabilizer to all of it-- even to the gas that's running through the mower, edger, whip, and blower when we're mowing every 4 or 5 days in May.
I've even purchased and burned the high-dollar pre-mix gas one can buy at outdoor power equipment centers. I'm a big advocate of running the best gas possible in those engines. I'm done buying a handful of Stihl carburetors every spring.
Are those babies 2T? I thought 2 stroke oil was a fuel stabilizer?
@dlearl476 posted:Are those babies 2T? I thought 2 stroke oil was a fuel stabilizer?
It's not. I add Stabil to my 2-stroke mix whether I have E10 or E-free.
Any comments about Stabil vs Startron?
Yes
Use one.
Or the other.
I like the Marine Stabil---as I remember it takes a lot less to get the same result. This Helpful on a long trip because it is good to add to ethanol fuel and takes up less space in the trunk.
Me too, Jack!
I like Marine Stabil too. I wonder why there are multiple versions.
I use Stabil for my mowers and StarTron in the Speedster. I can't give a good reason why. I switched to StarTron for the Speedster when some people here touted it a while back.
Probably me. I use both. Sta-Bil in the yard equipment and generator and StarTron in the Speedster, only because "Dave the NAPA guy" told me it sold better than Sta-Bil.
All of my power tools start right up at the beginning of their respective seasons and I have never had fuel problems in the speedster.
I also give everything a triple-dose of Sea Foam in a quarter-tank of gas once in a while just for good measure. It's cheap insurance.
Yep, I believe it was you, Gordon. It would be nice to know more about the differences between the two.