Let's talk gas/oil mix...

[Steve White]

may seem like a stupid question, but where do you get av gas ?? do they sell it to anyone at like a local small airport?

You can also obtain it in the go kart racing community. I used to run Phillips 66 avgas in the racing karts.

 

[Rudy Formanek]

Just some information from my recent gokarting experience with my adult son. Racing gas is available at most go kart shops but expect to pay much more than what is charged by an airport for 100LL. I buy 100LL from the Lodi airport for about $4.50 a gallon, the local go kart track charges $105.00 for 5 gallons of Sunoco 110 and a liter of Elf 2T oil. Last year I was able to purchase mail order Motul Gran Prix liters for 9.99 with free shipping over$100.00, the same place charges 19.99 now. This last race they tested the gas after qualifying, our Sunoco that we bought that day mixed with Elf oil 1L/5 gallons registered +6, I retreived our practice gas from our pits and it tested -3. I was told it passed, passing was plus or minus 10. A driver who said he used 87 octane pump had registered +200, I was told it was because of the ethanol in pump gas. I have been running 100LL avgas in my boats for two seasons before the Covid and I am pleased. I have been using Motul 2T 8oz per gallon. I fortify the first gallon with 25% of the oil castor for new engines. YMMV.

 

[LohringMiller]

If you know how to increase the compression in Zenoahs or their clones under NAMBA rules, let me know. The whole point is with a standard engine, ignition, and pipe, fuel doesn't matter much. Head button engines are a very different issue. The Zenoah has around 2.4 cc head volume. We tested Quickdraws with 1.8 cc head volume. You can probably go lower with a toroidal combustion chamber. There's a reason VP's UT really helped in our Quickdraws, but not in Zenoahs or Chung Yang engines.

Lohring Miller

 

[Terry Keeley]

If you know how to increase the compression in Zenoahs or their clones under NAMBA rules, let me know. The whole point is with a standard engine, ignition, and pipe, fuel doesn't matter much. Head button engines are a very different issue. The Zenoah has around 2.4 cc head volume. We tested Quickdraws with 1.8 cc head volume. You can probably go lower with a toroidal combustion chamber. There's a reason VP's UT really helped in our Quickdraws, but not in Zenoahs or Chung Yang engines.

Lohring Miller

What sort of C/R would that 1.8cc head be?

 

[Rudy Formanek]

I dont run100LL for the octane, I run it cause it's cheaper than Coleman's and it has no ethanol. Tried washing unleaded pump gas seemed inconsistent.

 

[David Bryant]

I am going to be running the premix VP racing gas for 2 stroke motors that they make you can’t go wrong with their products

I received this response from VP Fuels, Technical Support, in regards to available product for small 2-stroke engines (quote):

"In unleaded we have the MS-100, MS-103 or MS-109, in leaded we offer the VPR, U-4.4 or the VP-110."

Tom Henriott Technical Support Warehouse Manager m: 812-878-2025 p: 812-466-1175 EXT 303 e: [email protected] VP Racing Fuels Midwest 4100 East Steelton Road Terre Haute, IN. 47805

 

[Todd]

VP also has the SEF (Small Engine Fuel) that works well. It just depends on which head button on our engine you are using depends if you can use it or not. It is like 94 octane.

Todd

Quickdraw

 

[LohringMiller]

Geometric compression ratio is around 15 to one with 1.8 cc and 11.6 to 1 with 2.4 cc head volume. I think you can run 1.2 cc with a toroidal head design. That would be around 22 to one geometric compression ratio. Exhaust port timing makes these ratios lower than in a four stroke engine since the port will be open for around half the piston travel. However, you need to remember that this isn't completely lost in a piped engine. The left over exhaust energy is used to scavenge and supercharge the engine.

Lohring Miller

PS CR calculator Engine Compression Ratio (CR) Calculator

 

[Wasted wages]

All things being equal, it would be great if Terry could run some baseline numbers using a set pump gas/oil mix ratio and then without adjusting anything other than the high speed needle, give comparison numbers for different fuels...

Who knows, maybe he already has plans for something like this... and probably has a long list of stuff to try out once his dyno is done.

Terry, as others has said before, Thank you!! for all you are doing to benefit us little guys out here understand how to extract top performance from these little powerhouses
and cut thru all the hype and claims!!!

 

[Steve White]

^^^ Do a little "Mythbusting". That would be most interesting, albeit time consuming.

I would be particularly interested in the Ethanol arena. Cuz in the NHRA at the drag strip, alcohol goes faster than race gas and they test to make sure you ain't got none in the tank as it's considered cheating. If it was slower, why would they care?

Don't need a firestorm here - just sayin'. I want to see the test results in a valid comparison both with and without compression ratio & timing changes on a model boat gas engine.

 

[Terry Keeley]

Geometric compression ratio is around 15 to one with 1.8 cc and 11.6 to 1 with 2.4 cc head volume. I think you can run 1.2 cc with a toroidal head design. That would be around 22 to one geometric compression ratio. Exhaust port timing makes these ratios lower than in a four stroke engine since the port will be open for around half the piston travel. However, you need to remember that this isn't completely lost in a piped engine. The left over exhaust energy is used to scavenge and supercharge the engine.

Lohring Miller

PS CR calculator Engine Compression Ratio (CR) Calculator

Wow, that sure sounds low compared to what we run on the nitro side. Any idea what the trapped C/R is with 1.8cc? 1.2cc?

Ya, I got a list building of things I want to test, first tho is to get very consistent results with a stock unit and also to be able to find the best needle setting for each setup without burning up stuff...

 

[Steve White]

All things being equal, it would be great if Terry could run some baseline numbers using a set pump gas/oil mix ratio and then without adjusting anything other than the high speed needle, give comparison numbers for different fuels...

Who knows, maybe he already has plans for something like this... and probably has a long list of stuff to try out once his dyno is done.

Terry, as others has said before, Thank you!! for all you are doing to benefit us little guys out here understand how to extract top performance from these little powerhouses
and cut thru all the hype and claims!!!

Ya got me thinking now. Watching various motorsports and dyno testing for both engine dyno's and chassis dyno's. It's generally about max performance to varying degrees, all the way to the portable chassis dyno's that travel around and guy's pull their "dyno queens" onto for bragging rights. I have no issue with any of that - do what you want. A dyno is a tool that has many applications and uses for both manufacturer and end user.

Dyno testing can be far more useful than just engine tuning - as you alluded to, making testing comparisons as well.

Another one I would love to see are some dyno results on engine vibration isolation and types of engine mounts to include overall mass. Notice I didn't refer to them as "vibration dampers" because they really are not that in engine mounting in a race vehicle. It doesn't seem like they would dampen anything - they decouple vibration. Some racing vehicles use them, some don't. Drag boats, drag cars hard mount to the chassis, as do sprint cars, karts, many motorcycles.

Decoupling engine vibration in model boating was recommended to me years ago by Don Pinkert for a Thundergator twin I was building. Don explained in a twin there is harmonic interaction vibration from the two engines - which made perfect sense to me.

But, why on a single engine setup? Decoupling decreases hull vibration and likely increases engine vibration in the process. Hardness and stiffness of mounting also is a factor. I've seen discussions about high engine vibration and broken glow coils and such from softer rubber isolation pads. That would be most interesting to see some dyno results of varying engine mounting and decoupling versus solid mounting.

It may be that decoupling in a single engine condition simply increases engine wear and decreases performance. Not sure, would love to see some dyno testing and monitoring such as strain gauge stuff.

The model engine dyno's I've seen are all rigid mount types. Perhaps someone has already done this and published the results? Common knowledge in the model boating community and I'm just behind the times?

 

[Steve White]

Wow, that sure sounds low compared to what we run on the nitro side. Any idea what the trapped C/R is with 1.8cc? 1.2cc?

Ya, I got a list building of things I want to test, first tho is to get very consistent results with a stock unit and also to be able to find the best needle setting for each setup without burning up stuff...

You don't wan't a melt down pile of scrap Terry, and spend $10 grand getting there?

I hydraulic'd an OPS 40 wide open once when the hydro took a sudden nose dive. So bad all that was left was collet, flywheel, coupler, intake and water jacket - I didn't even trust the head to reuse it.

 

[Don Ferrette]

Right up front let me be CRYSTAL CLEAR on the guys who take the time and make the effort to do the dynos, kudos my friends as it is definitely a valuable learning tool. With that being said personally I feel there is one big difference between the dyno and the pond- the load placed on the engine. Seen plenty of dyno kings that were pigs on the water as vice versa. The most consistent thing about the water is it's inconsistency so for me my dyno is the pond and the desire for repeatable top performance in ever changing conditions. Big numbers on a dyno are cool I'll give ya that but in the end it all boils down to how fast you can cut a lap.

 

[Steve White]

Right up front let me be CRYSTAL CLEAR on the guys who take the time and make the effort to do the dynos, kudos my friends as it is definitely a valuable learning tool. With that being said personally I feel there is one big difference between the dyno and the pond- the load placed on the engine. Seen plenty of dyno kings that were pigs on the water as vice versa. The most consistent thing about the water is it's inconsistency so for me my dyno is the pond and the desire for repeatable top performance in ever changing conditions. Big numbers on a dyno are cool I'll give ya that but in the end it all boils down to how fast you can cut a lap.

Absolutely. It's about management of the torque curve, and the dynamics of the model. Any experienced crew chief knows the one that runs best on the dyno doesn't always run best on race day.

When running frequently in the past, I got completely away from bench testing for any of it. Did all testing and tuning in the boat on the pond.

The dyno definitely has it's place - but it's not the end all, be all, do all. One needs to know how to use the tool and apply what's learned on the tool to real world application.

Consistency generally means leaning more towards the conservative side of tuning options.

 

[Wasted wages]

Dyno's are just that....a tool.

But what happens is exactly what Steve said, people using them for bragging rights. To me those numbers are useless, as dyno's can be manipulated to give false information.

You can see it when they get some outrageous hp numbers on a racing engine, that may be way out of the useable rpm range for the car it's going in. A flash reading..if you will.

Current turbo engine videos are notorious for this, 3500-4000 hp numbers at 50+ psi of boost
for a split second.

Getting a baseline number on an engine, making a change and rerunning the engine and comparing the data is where it's at.

 

[Terry Keeley]

Agreed guys.

I started this thing as a break-in stand because I was tired of driving an hour to the pond and running around in endless circles. To properly break in a (67-90) motor it can take four gallons or more so that means two days at the pond.

Then I thought about all the questions I had about what I was seeing in my SAW testing with the Eagle Tree and started researching the dyno part and decided to make the thing dual purpose.

I talked to several that have "binder dundat" (Jim Allen, Dave Marles, Marty, Lohring) to see if they "found" stuff on the dyno that translated to the water. They all said yes. I also talked to Brian Spitzer in Celina (he has experience with dyno tuning Pro Stock cars) and asked what he thought. His answer?

Horsepower is horsepower, lol.

I'm sure not going through all this effort just to make pretty graphs...

 

[Steve White]

^^^ One could do all kinds of testing. We use flow meters to replicate what works, not establish the baseline - that comes from the model's actual performance. Flow meter will make the baseline mixture tuning repeatable - it doesn't needle the engine.

One could tune an engine in a model - and I don't mean just needle it, I mean timing, head, intake, pipe - the whole shebang. Then use the dyno much like we use the flow meter. Look at the torque curve and HP numbers and experiment with tuning, not just for peak HP, but for low end torque, broad power band, etc. Create what works and use the dyno to better understand and refine it.

Terry, there is no doubt in my mind that you will use that tool effectively and it will translate to results at the pond.

Dyno is just like every other tuning tool - it's not about the dyno, it's about the operator and/or tuner. That Clausing you have doesn't run itself.

 

[LohringMiller]

We dynoed engines for over 14 years. Mike started his dyno experience with setting up the test program for an offshore power boat racing team. He has dynoed everything from BMW race engines to kart engines on water brake and inertial dynos. We even tested our electric hydro motor on a brake dyno. In addition, we worked with Quickdraw's dyno program to develop their 26 cc engine. This resulted in a gas SAW record that stood 14 years and a gas sport hydro record that still stands.

We tested lots of fuel combinations as well as oil ratios and types on everything from Zenoahs and Chung Yangs to the 35 cc CMB. We tested engines for Tower Hobbies and convinced them to change to Zenoahs over the inexpensive engines they were looking at. We did carb development programs, pipe development programs, and muffler development programs. You couldn't accomplishment a tiny fraction of this without systematic dyno testing.

I've done my best over the years to write articles on this as well as producing concrete summaries of our tests to answer questions on these forums. I encourage others to build dynos and do the same. I get especially irritated when people who have no dyno testing experience discount the value of this testing.

Lohring Miller

 

[Don Ferrette]

Relax Lohring, all that is being said is the dynos are a TOOL and not an end all. You know as well as anyone there are those out there who boast about their "engine work" soley on dyno numbers.........