bikeordie092

this may be a dumb question, but what mixture of gas do most people use for 1/8th scale cars? i have a .26 ofna force motor and the fuel i have right now is 20% nitro and i believe 14% oil.. is that too much oil? there is alot of oil that comes out of the exhaust... my philosophy with motors (mainly my boat motor and weed-whacker motors) is that too much oil has never hurt an engine.

i guess my real question is would i get better performance with less oil? as i said before there is ALOT of oil that comes out of my exhaust, like after i let it run for a while it will make a good sized puddle under the exhaust and after i cut it off i can tilt the car and get a decent stream out of the pipe that i guess just accumulates inside the pipe while running...

john josey

You will get more performance with less oil, but you run the risk of damaging the engine with a lean run.

A while back i was looking for an excuse to buy myself a new engine for my Hyper 7, but there was nothing wrong with the engine i had, so i decided to mix fuel to see what it would take to kill it.

I had half a gallon of nitro left over from something else, so i decided to add 10% turbine oil and the other 40% was methanol. The fuel went jet black in colour and distorted my plastic fueling bottle slightly, but that engine is still going strong as ever ! i only have enough of that fuel left for a few tanks worth now and dont know what to do when it is used up.

My dilema is this....do i spend the money and do the same again, if i do and the engine let's go within the first few tanks i wouldnt be happy putting it through a brand new engine. Or do i just use an off the shelf fuel.

The buggy goes like stink though

bikeordie092

Well, I don't want to hurt this motor as its new and I just got it broke in. I probably won't fool with mixing my own fuel... I was just wondering what the "optimum" mixture for this motor would be. I want good performance and longevity as well.

john josey

When i started in this hobby, the one piece of advice that stuck in my head was "go with the oily mix, your engine will love you for it"

bikeordie092

Yeah, I may go to some 12% when I'm out of what I have... what I have is supposed to be really good.... its the black open protekk 20% nitro... would I get more performance if I went up on the nitro and stayed the same with the oil?

john josey

In practice, i have never found any difference in perfomance between 20 and 30%

Think of nitro as a chemical supercharger, it will allow you to burn more fuel for a given amount of air. The more air/fuel mix you can burn at the optimum setting the more power the engine will produce, using more nitro means the needle valve will have to be opened to a richer setting, so the downside is you will get less run time per tank.

I think running 20% nitro is a good compromise between cost, run time and performance.

Argess

I've always used 20% nitro. Oil ratio is another thing. I once used 16% oil and my engines always ran hot. Dropped it to 12% and my engines tuned easier, ran better, and ran cooler.

Here's a link about fuel. I'm not saying everything they mentiotn is right, but the part about 8 to 12 % oil seems to match my own experience when it comes to using too high an oil content:

http://www.storacingproducts.com/und...itro-fuel.html

supertib

I run 30% nitro , 7% oil........run super cool, tunes very easy and makes excellent power........I am not a fan of high oil content fuels, as they tend to burn hot and have a very narrow sweet spot in the tuning, the high oil disrupts combustion and forces you to run a overly lean mixture to get a crispy throttle response...which more then defeats the the entire purpose of running high oil........... under race conditions, with a race tune my engines live much longer on 7% oil then they would on 12% oil........with 7% oil content I can run a richer mixture which results in more overall lubrication and cooler operating temps.... Its amazing how much easier and more predictable the the tuning window is on a lower oil fuel as compared to a higher oil fuel..................Keep in mind I run modified race engines that see RPM's well in excess of 40 000, where running a lean mixture will result in very rapid engine damage..... And because I have pushed these engines to limits for so long I have developed some knowledge on what it takes to make a high out put modified engine hold together....Low oil fuels do much better then high oil fuels....However, the quality of oil used becomes very critical when your reduce the quantity like we do...But I will tell you, tuning a 7% oil back to back with a 12% oil would blow your mind.....the low oil fuel almost tunes itself, the throttle response will be crazy crispy at an extremely rich mixture......On the same mixture the high oil fuel will be spitting and sputtering and sounding more like a Briggs and Stratton then a high RPM nitro race engine, the low oil fuel will sound like a F1 car....... anyways I hope this helps some.......

bikeordie092

That helps a lot actually. Now it makes sense to my as to why I had to tune on my motor for almost 2 days! I have fuel that is 14% oil!

supertib

14% oil would be a horrendous fuel to try to tune............it baffles me why anyone would mix a fuel with such high oil......

In the end get rid of that fuel....get yourself some high quality Race fuel like Werks or Byron's. you will find your tune much easier to find.....

Argess

You probably won’t want to hear this, but the Force 26 was the worst engine I ever owned.. I always found it very touchy engine to tune without it getting way too hot. And by that I mean well over 300degF for decent performance, but detonation starts about 325degF with the Force 26. You can hear at idle after it comes in after a few WOT runs. Idle is higher than normal, and it makes sort of a sizzling sound. To be fair, I do a lot of WOT runs, and over grass, which contributes to making an engine run hot.

So I experimented.

First thing was the fuel. Dropping to 12% oil made a significant difference in ease of tuning, engine performance and reduction in head temperature. I didn’t go lower as this was the best I could do with what my LHS had available. Just the brand can make a difference too. For example, I find Blue Thunder runs cooler than Morgan’s Sidewinder. Whatever you do, don’t use Backyard Basher. Way too much oil (16%), and causes all kinds of problems.



I also have a Force 28 which has always run great. Completely different than the Force 26. The Force 26 heatsink has always appeared to me to be insufficient for it's task.

I did a comparison of the Force 26 with the Force 28. Rough approximations, but close enough to get the picture:

1/ Force 28 has 7.7% larger displacement than the Force 26

2/ Force 28 has 12.5% more power than the Force 26

3/ The Force 28 head has "approximately" 32.3% more surface area than the Force 26.

4/ I have had no troubles with overheating from the Force 28.

More research revealed the OFNA head was cast which dissipates heat more poorly than a machined billet head. Regardless, a larger aftermarket head solved my troubles with this engine, but not my curiosity. Basically, I wanted to reduce the heat at it’s source, not band-aid things up by merely dissipating all this extra heat by using a larger cooling head.



After a little more experimenting, I found an additional improvement in running cooler by using an OS A5 plug. This is a short plug and helps reduce the compression ratio a bit. Similar idea as adding a head shim.

So eventually I tried adding an extra head shim to mine and the temp drop was incredible, plus the engine ran great! Unfortunately I didn't allow for a bit more break-in at the new cooler temp and kept pushing the engine to get more heat. The crank pin finally broke. Mind you, the engine had many, many gallons on it, plus I experimented a lot with this engine, so it was sort of “abused�.

I'd like to say add another head shim, plus go back to a MC8 plug is the answer for the Force 26, but as mine did self-destruct when I did it, I'd be careful doing that.



I remember having a tough time breaking the Force 26 in as well. I got a lot of blisters from mine for quite a while. I eventually converted to Roto-Start, which worked great.

During Break-In, I also had a lot of fuel dripping out the pipe. Can’t remember for sure why that was, but one thing I have found for Break-In is to do a rough adjustment on the LSN for best idle. Just tune it so the engine will idle for at least 15 seconds or more. Just listen to it. If it slowly speeds up, then you need to richen the LSN a bit. If it slowly bogs down, then lean the LSN a little bit. This isn’t necessarily the best tune for performance in the vehicle, but it helps keep the Break-In going smoothly. Nothing more frustrating during Break-In than an engine that always stalls.

In contrast, don’t forget to keep the HSN rich for Break-In, leaning it little by little as you go through tanks of fuel. But too rich isn’t good either as the engine can bog to the point it stalls causing more frustration. I find the HSN has to be set a little bit leaner than the Factory recommended settings for Break-In.

However, back to the Roto-Start thing. I sort of did it all backwards. Should have installed Roto-Start for Break-In, and then went back to Pull-Start after that. I like Roto-Start, but it’s a big heavy thing to stick in your pocket when you have to go make a re-start “some-where-out-there�..

So....go with the OS A5 plugs, convert to Roto-start if you can, break them in individually for the first 2 to 3 tanks and keep them rich enough they don't exceed 300degF.

The OFNA buggy guys told me the Force 26 runs much cooler with 30% nitro and this makes tuning easier. I’m not sure if this correlates with me adding a head shim because I use 20% or not. Anyway, I havn't tried it, but you might want to consider it.

In a nutshell, here’s things that can help with your Force 26:

1/ Use fuel with a lower oil content. I’m happy with 12%, but no doubt you can go lower.

2/ Use an OS A5 plug (I think the part number has been changed to OS #10)

http://www.osengines.com/accys/glowplugs.html

3/ The, the Force 26 should start with the LSN "flush" and the HSN about 1.5 to 2 turns in from flush. The LSN is probably never adjusted more than 1 turn in from flush, and the HSN can be almost anywhere, but typically 2.5 turns in from flush once broken in. The LSN is often about 1/2 turn in from flush once tuned, and I think is safe for Break-In.

4/ Once Break-In is over, and you start tuning for performance, a common mistake is thinking the engine is tuned well, but it seems way too hot after doing some WOT runs. Typically this is due to the HSN being too lean and the LSN too rich. As the engine revs up, it seems OK, but actually runs lean once the excess fuel from the rich LSN burns off. Tune your LSN to avoid this.

5/ You can try 30% fuel and see how you like it. No doubt you will have to re-tune things a bit.

6/ Install a Roto-Start. You can go back to a Pull-Start after Break-In if you like.

7/ I wouldn’t recommend trying an extra head shim (plus offsetting that type of serious change a bit by going back to a long plug, like the MC8) just yet. It’s a new engine, and since that type of experimenting can go terribly wrong, it would be a shame to see it self-destruct.

Ps: My Force 26 was purchased new back around 2006 or so. It’s possible yours is different, so some things I mentioned may not apply, such as “turns in�, etc

Zrock

I actually think the traxxas fuel has the highest oil content thought i read some ware it was up around 16%? correct me if im wrong.. Find it a real bear to keep it tned nicely. Just got some sidewinder today so gonna burn off the last of the traxxas and switch over So its eather 10 or 12% depending on what jug i got..

HerrSavage

I'm skeptical of sub-%10 oil. In my experience it doesn't help power, and narrows the tuning window. That was my experince with Tornado Competition %25 anyway, which has %8.7 oil iirc.

supertib

The issues you seen must have been more to do with the brand of fuel then the lower oil content...........we have run as low as 4 % oil and the tuning window was excellent...generally speaking the higher the oil content the narrower the tuning window........... This is of course assuming we are using quality products in the blend....a low quantity of cheap oil wont work too well, just like a high quantity of good oil wont work too well........

JohnP2

Interesting topic. Let's play Mythbusters here.....

Will you harm your engine if you use 30% and switch to 20% (or vise-versa? I understand its tune and glow power will need to be compensated, but once everything HAS been compensated when making a switch....does it affect the engine?

downunder

Seeing I'm called the Mythbuster in the engines forum , no, it won't harm the engine at all. Regardless of temperature, the piston rides on a film of oil which is what keeps it seperated from the liner. So long as that oil film is continuous there's no contact so no wear and it's the oil film that holds the seal against compression, not the "pinch".

As a contribution to the oil content side of fuels, my son (on my recommendation) uses 20% all castor and zero nitro. It's dead easy to tune and runs perfectly.

bikeordie092

well, seems i started a good thread here lol.. the general consensus seems to be that i need to run less oil. will do that as soon as i get my roto-start in lol (ordered it today)... i have blisters and my cord keeps screwing up... and my temp doesnt seem to be going too crazy... i bought an infrared thermometer from work (autozone) and i think the highest it went was like 257.. that was after a couple times up and down the street, never took it WOT tho. it has a #8 glow plug in it now and seems to be doing ok.

i should have all my parts in by wednesday, so she should be 100% in the next few days. im loving the hobby so far. and all of you on here are awesome! very helpful.

on another note, what are some "good and affordable" high-torque servos to use? it seems like these are just a little sluggish, especially the steering servo...

Argess

Consensus sometimes isn't so good. Downunder probably knows more about fuel than all the rest of us put together. However, what he says isn't matching up with what I've noticed about oil content and tuning. I'm no fuel chemist, but perhaps his 20% oil, zero % nitro acts the same as 10% oil, 20% nitro when it comes to tuning? Perhaps castor oil in his home brew doesn't act the same as modern fuels containing synthetic lubricants? I don't know the answer, but I do know that sometimes the majority is wrong and a single voice is right.

However, as you're presumeably not mixing your own fuel, maybe go ahead and try some with lower oil content. Then you can find out for yourself.

On servos, it depends on what type of radio system you have. For my old analog radios, I generally upgraded my buggy steering servos to the Futaba S3010.

http://www3.towerhobbies.com/cgi-bin...&I=LXDTB3&P=ML

bikeordie092

lol idk what system i have to be honest.. i know it takes crystals if that tells you anything... i may sound dumb here, but i was thinking servos were "universal"? but i am new in the hobby lol. i thought it would only matter what receiver and transmitter i had and that any servo would work lol...

Zrock

From my short run today with my savage and sidewinder fuel I have way more punch than I ever did with the traxxas fuel. Still did not get to tune it but even out of tune I can tell u I will never go back to a high oil rate.

bikeordie092

im going to buy some different fuel as soon as i can, but i cant start my car with the pull start broken lol i have my roto-start on the way tho. ill probably be using a drill to start it, but i got the rear cover part.

oh yeah argess, i did just look at my car and it has a futaba s3003 on it now, but it doesnt even have enough torque to turn the wheels unless the car is moving.

Zrock

Just remember to have your drill going the right way. Look at your local hardware store for cord the same size.  I'm actually going the other way. I'm going to switch both my rigs to pull start after today I have had it with roto and easy starts. Trying to tune the savage I always had to walk back and get the starter when I stalled it. And for some reason the easy start would not turn over the engine today. Tore it down and greased it all and seems to be working fine as long as it does not stop at tdc.

supertib

20% oil in a car or plane ?

1QwkSport2.5r

His son has a car.

I break my engines in on 16-20% oil and always run 20% nitro. Once broken in I drop down to 10% oil that's 50/50 castor/synthetic.

A car engine runs just fine on high oil fuel, high castor content included. The only real difference I've noticed with high oil fuel is you lose some rpm. However, Downunder has the ability to modify or make a new head button to raise compression enough to run as well on FAI fuel as it did on normal high nitro fuel.

Feed as much oil to an engine as it will take, and it will run well for a long time. Not to say it won't run for a long time on low oil fuel, but to the novice or even intermediate tuner, one lean run and its all over or darn close. That's why so much premixed shelf fuel has so much oil - cover the 'rookies' tails.

Just IMHO. I don't mind not getting every last rpm from my engines; so 10-12% isn't "high" to me, and I always use a 50/50 castor synthetic blend now.

HerrSavage

My engines seemed to rev higher with the oilier Sidewinder.. And cooler. Just subjective impression though..