Foxy

Hi!

I have prepared this FAQ due to the increased number of enquiries about gas cars from other sectors of the hobby. Lately we've had plane guys, boat guys, nitro guys, electric guys, heli guys, even some of those weird tank guys getting in on the gas powered car explosion going on right now!

So here is an FAQ on the most basic aspects of running a gas car. I hope it answers some of the more Frequently Asked Questions from those looking to get into some giant scale mayhem.

Here are the questions, each links to the post below which covers the topic, just click on a FAQ, or read them all in order!

If any of you l33t gas guys want to add something, either post in the thread or PM me, and I will be happy to add it. This should make a great resource for our newcomers.

1) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217522]What's so great about gas cars!?[/link]

2) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217532]Gas and 2-stroke oil? What's 2-stroke oil? How much do I need?[/link]

3) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217549]Starting? Break-in? Tuning? Temperatures? After run?[/link]

4) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217566]OK, how fast do they go?[/link]

5) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217577]Fine, how can I make them FASTER!?[/link]

6) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217582]These things are expensive. Is there a cheaper way? Clones?[/link]

7) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217585]Zenoah/CY engines? What's the difference?[/link]

8) [link=http://www.rcuniverse.com/forum/fb.asp?m=7217591]Radio, servo requirements? Failsafes?[/link]

9) More specific FAQS:[ul][*] [link=http://www.rcuniverse.com/forum/fb.asp?m=7217596]My FG shocks SUCK![/link][*] [link=http://www.rcuniverse.com/forum/fb.asp?m=7217601]My engine won't start![/link][*] [link=http://www.rcuniverse.com/forum/fb.asp?m=7217622]Engine Factory Needle Settings for Zen/CY[/link][*] [link=http://www.rcuniverse.com/forum/fb.asp?m=7217627]What gearsets are available for my HPI Baja?[/link]
[/ul]

Foxy

What's so great about Gassers/Large scale RC?

Well, where to start!? Firstly, it's the size. Who doesn't want bigger, heavier and meaner? Gas cars generally run in the 'large' scales. That's 1/6th and larger. Typically a 1/6th monster truck will be over half a meter in length, the HPI Baja (1/5th) is nearly a meter in length. These cars are very BIG.

Mostly though, it's convenience and low running costs. The main pros of running a gasser are the following...

Fuel is regular pump gas and 2-stroke oil, so it's very easy to obtain, and very cheap, compared to nitro fuel/li-po batteries etc.

Starting is easy, no pullstart blisters, no charging starter box batteries or rotostarts, the engines use a real spark plug like a 1:1 car, and start very easily once the correct simple procedure is followed.

Run time; you get over half an hour from one tank of gas, often over 40mins. That's a long time by any standards.

The engines do not need particular break in procedure, though many (including myself) recommend to take it easy just for the first tank while everything seats and settles.

They do not need tuning every time you go out either. After the first tank of 'break in', you will want to tune the engine for maximum performance. More detail on this later. The key thing here is that you tune them very easily, usually requiring only minimal adjustment, and you only do it once. They do not lose their tune like nitros, and the tune is much more abuse/temperature resistant. Usually you set and forget the needles.

There is no 'after-run' procedure to speak of either. You can either run the tank dry, or leave fuel in it, there's no problem leaving the fuel in there, just give it a good shake before you start it up the next time, to remix the gas and oil.

To sum it up, you just gas and go. It's very simple compared to most other fuel types. Just take the car out, throw it on the ground, turn everything on, and pull the starter. When you've finished, throw it back in the car. It really is that simple, and that's the beauty of large scale gas cars. No preparation, and no maintenance.

So, a quick mention of the cons? OK, expensive initial investment in the cars. They are not cheap. Mixing fuel isn't the most pleasant thing in the world, but thankfully you don't have to do it often. Hop up parts are expensive. Also worth mentioning, is that most large scale models have a weakness or two as supplied from the factory. This is simply because at the size they are, to include such high quality parts would push the price of the car outside the price bracket it is aimed at. Some cars have more weaknesses than others, more about that later. Most cars are more than acceptable, straight out of the box, especially the mid market and higher models. Lastly, they are also quite noisy.

Foxy

Gas and 2-stroke oil? What's 2-stroke oil? Where do I get it, and how much should I use?

Since these engines have no sump to hold oil for engine lubrication, like nitro, the oil comes from the fuel. You need to mix your pump gas with a specific amount of 2-stroke oil, in order to provide the engine with the lubrication (and cooling) that it needs.

What oil? Well, there are many topics about this, but the key here is to get a good performance 2-stroke oil. Klotz techniplate, Amsoil, Panolin are all popular ones, but if you can't find those, you should search on the forum, there have been multiple topics and suggestions. If you still can't find the help you need, try a motorcycle shop, and just ask for a high quality 2 stroke oil.

How much? Again, there is a certain amount of speculation about this. The general rule, and what you will most often see in the manuals for these gas engines, is 25:1, or 40ml in every liter. You should get a measuring cup or a giant syringe from the drug store in order to correctly measure your amounts. Incorrect mixing could shorten the life of your engine.

ALWAYS shake your fuel can before gassing up the car, to ensure the oil is well mixed with the gas.

Foxy

Starting? Break-in? Tuning? Temperatures? After run?

Starting is easy as 1,2,3. Usually these engines are supplied with the needles in positions which allow the engine to start and idle. If you have trouble on the first start, return the engine to it's [link=http://www.rcuniverse.com/forum/fb.asp?m=7217622]factory settings[/link], and try again.

To start the engine, first fill the fuel tank. Now close the lid tightly and go to the carburettor on the engine. You'll see a clear squishy 'bulb' on top. Press this until you see it fill up with fuel. Press it a couple more times just to be sure. Now find the choke lever on your engine. Found it? OK, put it DOWN, or if your engine is not upright in the car, move it in whichever direction necessary to CLOSE it. Now pull on the pull starter once, twice, three times. Chances are on the third pull, it either started and stopped, or at least tried to fire. That's good. Now put the choke back up, or reset it to it's default open position, and pull again. Within 2 pulls (more maybe if it's very cold) it should fire up and idle nicely. When the engine is warm, you can quickly start it just by pulling the cord, no need to mess with the choke, that's just for cold starts.

Break-in... As I mentioned at the top, no break in 'as such'. To me it's just sensible for the first run not to go crazy while all the screws seat, seals bed in, etc etc. Others say you can full throttle them after only a couple of mins of running. In any case, break in is not something worth frothing over with these cars. Whether you run a full tank or maybe only a half, you can be tuning for performance within about a half hour of the first start.

Tuning... These engines have needles similar to nitro engines. There are 3 main adjustments, high speed, low speed and the idle screw. If you have not already done so, reset the engine to [link=http://www.rcuniverse.com/forum/fb.asp?m=7217622]factory settings[/link], run it for a tank, then start tuning.

Tuning a gas engine is much easier than tuning a nitro engine. They are far more sensitive to needle changes. Start with the low speed, and with the car warmed up and idling, turn it 1/16th of a turn clockwise. You can hear the difference straight away, as the engine speed increases a touch and burbles (bogs) less. You can also hear it start to run lean and speed up a lot if you go too far, what you're aiming for is somewhere in the middle of these 2 sounds. A nice clean idle. You'll get a feel for it quickly. Test the setting by accelerating away from you hard. It should accelerate cleanly and not sound like it's bogging or straining for fuel.

Now repeat the process on the other (high speed) needle, but be aware that to test and understand the difference, you should go from a rolling start to full speed, and watch the performance/listen to the engine.

There is a very good way of telling how well you have tuned your engine, this is by checking the plug (spark plug). Remove the spark plug from the engine and inspect the tip where the spark is made. If it appears grey and burnt, you are running too lean. If it appears black and sooty, you are running too rich. It should be a nice chocolatey brown colour.

Temperatures... These engines have their own cooling fan blades on the flywheel, this pulls air through the pullstart assembly and the engine cowling directs it through the fins of the head, cooling the engine very effectively. There is little need to worry about temperatures with these engines, unless this airway has become blocked. Pullstart outer filters (a cover made of 'breathable' material, usually velcroed around the pullstart assembly), are a very good investment to prevent this airway from getting blocked with grass, leaves and mud.

After-run procedure... There is none, leave the fuel in the car as long as you want (within reason, it won't last years!), just remember to shake the tank before priming it for it's next run. The same goes for your fuel can, always give it a shake before fueling the car.

Foxy

OK, that all sounds good. So how fast do they go??

As with all RC cars, that depends on engine power and gearing. Stock RTR cars usually come with 23cc engines and quite low gearing, therefore do not have very high top speeds. Its important when selecting engines and looking at the output figures, to understand that the size advantage these engines have does not give them big horsepower gains, but it DOES give them HUGE torque gains over nitro. Horsepower of a powerful .28 nitro engine, and a regular unmodified 23cc gas engine is about the same. Torque however is many times more from the gas engine.

So, simple answer, RTRs out of the box should do around 35-45mph, with engine and gear changes, speeds up to 60mph are quite acheivable.

Trust me though, a 1m long 25-30lb car going 35-40mph is an awesome sight, 50 plus is getting frightening. Such speeds are not necessary to get full enjoyment from a large scale car, but are of course, eminently possible.

Refer to [link=http://www.rcuniverse.com/forum/fb.asp?m=7172298]this thread[/link] for an example of some of the gear ratios that are available for the Baja 5b, and expected top speeds. Of course for the high speed gear sets, a more powerful engine is advisable.

Lastly, worth mentioning, though I will go into more detail later, that just changing the exhaust pipe can make a huge difference to these engines, sometimes increasing power by as much as 30%

Foxy

So how do I make them faster!?

Three ways... Better exhaust pipe, better engine, changing gear ratios.

Pipes... One of the things you can do to the car/engine, that will make the biggest performance difference of all, is to change the exhaust pipe. Most RTR cars are supplied with the most basic apparatus pretending to be an exhaust pipe. usually these are referred to as 'stock cans', or 'heli cans', as they are used in helis. By changing from one of these basic pipes, to a decent race tuned exhaust system can give you gains in the region of 30%, and transform the performance of the car. It is usually the first upgrade anybody does on these cars, as the difference it makes is huge, and very satisfying.

Gearing... As with all RC cars, changing the gear on the output shaft of the engine (commonly referred to as the pinion or clutch bell) for one with more teeth, increases speed and decreases acceleration. Similarly a reduction in teeth, gives better acceleration, and less top speed. The exact opposite applies to the spur gear (the large gear that meshes with the pinion), more teeth equals less speed, more acceleration. Less teeth equals more speed, less acceleration.

Some info on HPI Baja 5b gearsets which are available can be found [link=http://www.rcuniverse.com/forum/fb.asp?m=7172298]here[/link].

Engines... If you gear up for higher top end, as we said, you lose some acceleration. This can be made up for, by using a more powerful engine. Aftermarket and modified gas engines are worthy of a topic all on their own. There are many ways to go. You can either buy a complete race ported high displacement engine and replace the stock one, or you can buy what are called 'headkits' for your existing engine. Headkits are a cheaper way of upgrading your engine, as they will use the majority of the large parts from your old engine. Usually a headkit consists of a different engine head (usually ported) and a different piston. There are other things you can do (stuffed cranks for example), and as I say this is a subject worthy of an entire thread. If any good ones on the subject ever turn up, I will link them here.

Bear in mind, that speed is deceptive in these things. 40mph looks like 30 because of their size, and a 30lb car doing 40mph is a dangerous weapon indeed. Exercise caution where you run that you don't hurt yourself or someone else.

Foxy

These things are EXPENSIVE!! What about the cheaper chinese 'clones'?

Check out [link=http://www.rcuniverse.com/forum/fb.asp?m=7069462]this thread[/link]. Short answer is that some are worth it and some are not. At the time of writing, there is still much debate regarding quality, parts availablility, legality of importing, and even morality of buying clones. Only time will tell on this one, but if you buy a cheap clone, always bear in mind that you GET WHAT YOU PAY FOR.

Foxy

Zenoah/CY engines? What's the difference?

CY is a chinese company that produces good quality engines, similar in design to the popular and slightly more expensive Zenoah engines. The more expensive cars are often supplied with Zenoah engines, which run a bit smoother, develop a bit more power CC for CC. A Zen 26 should outperform (though not by much) a CY26. Once you start adding headkits though, it makes little difference which engine you originally started with. Evidence has been posted in the forums that the Zenoahs are slightly more aggressively ported from the factory, and that the porting is of better quality. I've even seen one site claiming that CY engines are superior, though I don't believe this for one second. Bottom line is that both are adequate engines, and apart from some very small differences, take the same upgrades/headkits/carbs, etc. Go Zenoah if ever given the option.

Foxy

Radio, servo requirements? Failsafes?

Gassers don't get on well with the old 27mhz AM radios. The 27mhz band is very close to the frequency of electrical noise naturally generated by gas engines when running. Avoid 27mhz.

40mhz FM is considered minimum requirement, but in this age of DSM and FHSS (2.4ghz crystal free systems), there's no excuse really to spend $1000 on a car and skimp on a cheap radio.

Go for a Spektrum, Nomadio, Futaba FASST or Airtonics FHSS system, if you have the cash, it's well worth it especially with a big fast car, to know that you are not going to be interfering with anyone, or have any glitching issues. 3ch radios are normally required either sooner or later for gas cars, though that does not apply for an HPI Baja 5b which will not be raced (there's no slot for a third servo on the car, and since not racing, no transponder is needed), but most large scales come with a third or even a 4th servo slot, for dual servo steering, or for additional disc brake systems, so 3ch has become the norm.

Servos (especially for steering) are obviously much larger and stronger than their standard size counterparts. Most servos available in the 1/4 size servo market are adequate for the job of steering a stock gasser, and the differences are whether you want to get a faster servo, or a digital servo, or a heavy duty metal geared servo, etc. There is one steering servo that does it all for a reasonable price, it's a large scale digital servo, with 16kg@6v holding power and 0.10sec/40deg/6v transit speed. It's called the Multiplex Rhino Digi4. Great servo.

For the throttle, some models provide only a small servo slot for a standard size servo. Some others give you the option to use large scale servos for throttle/brake duties as well as steering, but for most purposes, one strong (200oz-in or more) standard servo is adequate to pull the brakes and operate the carburettor on one of these cars.

I guess it goes without saying that servos for these cars are an important item, due to the size and weight of the car, so don't skimp here. Good servos will last you, bad ones will fail on you, and failures in control can be very expensive

Most RTRs come with rubbish electronics, which should be upgraded immediately.

Failsafes are essential for gassers, more than any other scale. If you have a 30lb truck run away from you at 40mph, you are not gonna be able to catch it, and chances are it will either do serious property damage, or worse, put someone in hospital with multiple leg/foot fractures. I can't stress enough the importance of at least a basic failsafe, and ideally one that can cut the engine as well.

Foxy

My FG shocks SUCK!

Yeh, out of the box, the FG shocks, especially on monster models, seem to have some issues. The worst of these seems to be that the plastic shock pistons are not very well finished (flash plastic) and the oil in the shocks is far too heavy (2000 european weight silicone). Refer to [link=http://www.rcuniverse.com/forum/fb.asp?m=7080903]this thread[/link] for some info about the problem, which I had and solved myself.

Foxy

My Engine won't start.

These engines require only a few basic ingredients in order to start. If one is missing, they will not 'go'. These things are... Fuel, air, compression and spark.

It's important to identify that you have all of these things. Lets take them one at a time...

Fuel...when priming does the bulb fill? After several pulls of the pullstart, remove the plug. Is it wet? If the answer to both of those is yes, the problem is not that the fuel is not getting through. If it seems like not enough fuel is getting through, try returning the needles to [link=http://www.rcuniverse.com/forum/fb.asp?m=7217622]factory settings[/link].

Air...remove and check the air filter for excessive dirt/blockages, look into the carb, check it's clear. Everything ok? Moving on...

Spark...remove the spark plug. With the spark plug out, reattach the lead and ground the thread of the plug on a metal part of the engine. Pull the pull starter. You should see a clean strong blue spark. If not, then replace the plug, or check the coil.

Compression...is a little bit tougher to test for, but if you get no resistance to your pulls on the pull starter, then chances are there is little or no compression in the engine. If this is the case, check the seals, gaskets, piston, ring, etc to see where the pressure is escaping.

Foxy

Factory needle settings for popular engines. These numbers were supplied by FG and as far as I know are accurate. Refer to the attached image for settings.

First, gently screw in both needles until they can't be screwed in any more. Do this GENTLY, just til they stop. Now turn them BACK OUT, counterclockwise the shown amount for your engine.

Foxy

What gearsets are available for my HPI Baja 5b? How fast can I go?

See [link=http://www.rcuniverse.com/forum/fb.asp?m=7172298]this post[/link].

Foxy

All done, please feel free to post your comments, issue corrections, or add anything you think would be of value.

Foxy

All done, please feel free to post your comments, issue corrections, or add anything you think would be of value.

Dave ESPI

Good Stuff so far man

badz

My Feedback: (1)

Pretty good stuff you got there Foxy, maybe add a list of all the major brand gaser manufacturers, not a seller but the actual manufacturer...mcd,fg,hpi,smartech,duratrax...I'd say add about the air filter cleaning, thats always a huge question for new gaser owners and the downsides of paper or cotton filters when used in dirt and dusty areas also about the proper filter oil to use, those coming from nitros will tend to think that oil is suitable for gasers when it isn't....but great deal getting this stickied, we needed this for a long time coming.

sheograth

Great thread, something we need on this forum.

snoking16

GOOD STUFF!!! i just did all that research alone and it took me weeks before i bought by baja SS...great job foxy and thanks for doing all the work it takes to create a good FAQ thread like this one.

beer=food

Yea that was a good read, looking at servo's and failsafes for the beast now !

Foxy

Thanks for the positive comments guys, makes it all worth it. Badz, good call on the filters, I'll put something on about that over the weekend.

DIABLOTAC78

great work foxy you made this forum a lot easier.

Anomie

Nice job there, Foxy [sm=thumbs_up.gif]

I'm certain this will answer many a question, and help new enthusiasts and veterans alike.

Louie2994

damn you got some time on your hands

splcrazy

since when did foxy become an expert in the field of largescale ?