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  1. #1
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    Traxxas engine converted to gasoline

    With lots of research I believe I have found a way to convert a nitro engine over to gasoline through modifying the compression, running a very hot glow plug, changing the carb to a walboro, and modifying all fuel lines. The result should be an engine with 80% the original power, 6x cheaper to run, and 3 times the run time per tank. Most Traxxas engines could also be ported to make up for the lost power.

    I am considering converting my own car .
    Last edited by Double G; 08-05-2019 at 12:51 PM. Reason: soliciting

  2. #2
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    As an update I'm currently working on the conversion. Currently I have modified the fuel lines and am running an OS LC4 glow plug. I'm trying gasoline with a 20:1 oil mix (gasoline is a natural lubricant so it doesn't need as much oil) I'm not finished but I tried to run it anyway. It gets really close to an idle and will sputter a lot. It is hard to find the perfect tune but I'm starting to think it will actually work.

    btw the car I'm using is an original Revo 2.5r
    Last edited by Bob2.0; 08-14-2019 at 02:52 PM.

  3. #3
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    I got the engine to rev up once on gasoline and run for a few seconds. Like I expect the gasoline is hard to find the proper tune to start let alone stay running. I want to try mixing 20% methanol to the gas to make tuning and starting easier. Sadly before I can continue I need to re-pinch the cylinder sleeve to restore some compression to my 8+ year old trx2.5r.

    If anyone has comments or insights it would be appreciated.

  4. #4
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    You might try using a hotter glow plug LC3? That LC4 is a med. There's not much of a selection of long reach plugs. There have been engines converted to run on gas. Read it is a lot of trial and error. Best of luck with the mod .

    You might get some answers looking through model airplane forums. Those guys have done and tried lots of things.

  5. #5
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    I've been planning on using the OS lc3 but none of my local hobby shops have it in stock. I need to order it off eBay or something. I would go with a CDI ignition system but my engine will rev to about 55k rpm (it has been ported) and the fastest CDI system tops out at 35k rpm. If any of you know of a faster CDI system information would be appreciated.

    As the airplane forums go I have read all I can find, but my engine is 1/5 the size of their engines and my engines rpm is 4x higher.

  6. #6
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    It's been a little while since I worked on the gasoline conversion so here is a quick update. I replaced the 13+ year old trx 2.5 on my revo with a brand new trx 3.3. I recently finished breaking the engine in on nitro. My latest idea is to mix roughly 15% methanol into the gasoline oil mix. Results so far seem promising. I can get a rough idle and it revs up ok. The tuning is much easier than straight gasoline and the cost per gallon for this fuel is about $6-$7 including the methenol and oil. I believe with a higher compression and an lc3 glow plug I could get a good stable idle.

  7. #7
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    I don't understand what your trying to accomplish. Just having fun with experimenting with trial and error, enjoying playing mad scientist, not worrying about ruining an engine or to be making a reliable engine to use. I look at RC as a hobby for each to enjoy in how they want to. I hope you are having fun trying this endeavor! It's not an easy task. Don't try to reinvent the wheel. Methanol is the number one ingredient out of three in RC "nitro fuel". The other two are oil mix and Nitromethane. You could run an rc engine on straight methanol and an oil blend,(probably the cheapest route you could go). Adding Nitromethane(this is where its not so cheap) gives you the extra oxygen which gives methanol more power. It's the same principle as a gasoline engine with a boost of nitrous oxide. Gasoline burns at a much different rate than methanol in an engine (different points of ignition). Mixing the two just by trying different ratios probably isn't going to be very helpful.

    Hopefully some helpfull tips: You need to lower the compression ratio to run gas in a methanol motor. You can run a shorter glow plug and/or add head shims part/5292 both will lower compression. If your looking for more power per fuel amount, I would be looking into gasoline-spark ignition conversion. Twice the energy density of methanol. 1oz gasoline = 2oz methanol
    Most model RC engines never see there theoretical max rpm's. Traxxas makes the most power at around 30,000 rpms. Right where most rc nitromethane engines spends most of its time. Running gas you could regear for the lost speed and increased torque.

  8. #8
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    I believe he is just experimenting and trying to find a cheaper solution to nitro as it is more expensive then gas per gallon. JMHO.

  9. #9
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    Quote Originally Posted by grizzly03 View Post
    Hopefully some helpfull tips: You need to lower the compression ratio to run gas in a methanol motor. You can run a shorter glow plug and/or add head shims part/5292 both will lower compression. If your looking for more power per fuel amount, I would be looking into gasoline-spark ignition conversion. Twice the energy density of methanol. 1oz gasoline = 2oz methanol
    Most model RC engines never see there theoretical max rpm's. Traxxas makes the most power at around 30,000 rpms. Right where most rc nitromethane engines spends most of its time. Running gas you could regear for the lost speed and increased torque.
    Thanks for the advice... But I believe I actually need to increase the compression. I'm running mostly gasoline(75%+) gasoline won't detonate until it reaches a compression ratio of about 14:1 and doesn't properly ignite with a glow plug until the compression ratio is about 12:1. Pure methanol is similar(15%+ of my fuel) it wants roughly a 10:1 in a glow engine (old engines that run pure methanol and oil have higher compression ratios). Because the nitro ignites at a lower compression most glow engines have roughly a 9:1 compression. So I think the compression will needs to be higher if run with glow ignition.

    If you question my reasoning look up the NV gx40bb. It is a .40 gasoline glow ignition engine with a 13:1 compression. You can also look up the OS ggt15 but less info is available on this engine.
    Last edited by Bob2.0; 08-27-2019 at 08:34 AM.

  10. #10
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    One I get this running well I intend to replace the original carb with a diaphragm carb so I can run straight gasoline with a 5% oil mix. The methanol additive just let's me use the original carb because it is less sensitive to the fuel mixture.
    Last edited by Bob2.0; 08-27-2019 at 08:44 AM.

  11. #11
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    I only meant you might need to find a way to introduce more air(oxygen) to your gas. Good gas efficiently needs 14.7lbs of air to 1lbs of gas. Methanol needs around 5 to 6 lbs of air to 1lbs methanol for good efficiently. You could also try leaning the gas mixture out more, or figure out how to add more oxygen to the gas. Adding more head volume allows more room for a better mixture.
    Stock needle settings allow more fuel ratio in than air in. Because oxygen is part of the fuel mixture.
    Example: stock settings say are 5:1 with methanol and if you adjust the needles(close) them in half it would be like 10:1 with gas (it allows for more oxygen on intake.)

  12. #12
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    I'm currently getting the best results with the high speed needle 1 3/4 turns out. Stock settings for 20% nitro is 4 turns out. I also turn the low speed needle about 1/4 turn in. So it is running about 2x more lean now
    Last edited by Bob2.0; 08-27-2019 at 01:21 PM.

  13. #13
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    Glad to hear your having better results

  14. #14
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    I just finished porting my engine to help make up the power loss of gasoline. after running my engine on nitro to test the porting it seems to me that it has about the same power in the low rpms but a LOT more power in the power band. In high speed runs the rpm of the engine just keeps climbing... It added at least an extra 5mph to my revos top speed. I'm planning on later giving it a tuned pipe optimized for low rpms and result should be about 10% more power in the low rpms and ~15% more power in the high rpms with the gasoline conversion.
    Last edited by Bob2.0; 08-27-2019 at 09:14 PM.

  15. #15
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    Have you tried running it under load yet? I would love to see a video of that engine. I've got my own plans of building a tiny IC engine(4 cylinder) and running it in place of a trx engine.

  16. #16
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    Sort of... I have only run it on my revo. It will run up to about 30 seconds before it dies and until it dies I can putt around a bit. It will die pretty quick if I don't give it throttle

    I have a pull start on it right now so if I leave the ez start in to keep the glow plug glowing it will runs much better. Because of this I believe I need a hotter glow plug and higher compression. I'll update you all when I get that done. When I get the engine running well I think I'll make a video.

  17. #17
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    I'll keep an eye out for any info I find to help you out more.

  18. #18
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    I recently modified the compression, swapped from the stock glow plug to an lc4, and now I am running straight gasoline and 2-stroke oil. All the changes made a big difference.

    I first switched to gasoline without the added methanol. Without the methanol I can get the engine to idle pretty reliably(With methanol in the gasoline it won't idle at all!). The downside is without methenol it is super sensitive to the tuning and it would die when any throttle was applied with or without a glow driver.

    Next I replaced the glow plug with an lc4 that I had sitting around. Suddenly without any other changes it became far less sensitive to how it was tuned. Also with the glow driver in I could rev it up, it has great throttle response, and it acted mostly like a normal nitro engine... But it wouldn't idle with the lc4 glow plug.

    Finally I modified the compression. To do this I removed the gasket entirely and sprayed a product where the gasket goes. The product is basically a copper filled adhesive that you apply to a gasket up help thermal heat transfer. So far the spray has provided an excellent seal where the gasket should be. The result is my engine will idle with the lc4 glow plug and no glow driver, it starts easy, revs to the moon(with the help of a glow driver), and with the help of the glow driver it acts just like a normal nitro engine (besides not liking the transition from idle to higher rpms).

    I still need to get my hands on an lc3 so I don't need to use the glow driver to do anything but idle and I am trying to find a cheap and small enough gasoline carb for my 3.3 engine.(Let me know if you know where to get one)

    Finally I'm trying to find what gasoline I should run. I feel really stupid saying this but don't know what octane I am currently using. My current thoughts are I could run a 91 octane fuel to help with the occasional detonation when starting(it only dotonates when starting. It has down this with every glow plug, compression ratio, and fuel aditives), I could run standard 87 octane in hopes that the faster ignition would help get more power in the higher rpm range and get a better idle, Or I could use ethanol free to help the engine run cooler and eliminate the need for after run oil(ethanol is an alcohol and alcohols attracts water which makes your engine rust... No alcohol= no after run oil). So if any of you have any thoughts let me know.
    Last edited by Bob2.0; 09-03-2019 at 05:48 PM.

  19. #19
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    Admittedly, I know nothing of gas/nitro engines. I have seen both gas and nitro engines advertised on RC sites so my question is why go through all of this hassle if a gas engine is available.

  20. #20
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    There isn't many nitro sized model engines running on gas w/spark plug and I think only O.S. has a model engine that runs on gas with glow plug. The other gas engines you read about are probably zenoah based engines, different size motor altogether.
    "why go through all this hassle..." because it's a hobby to enjoy.

  21. #21
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    Bob, I would try getting a hotter glow plug and stick with one plug before you keep trying different things. Would be easier to keep track of changes. If you need to keep glow heater attached, it's definitely not hot enough or timing is off. LC3 plug is like Traxxas standard plug(hot), LC4 is like Traxxas super-duty plug(medium). Also what fuel your trying to run will affect temperature during combustion, also richer=cooler and leaner=hotter.

  22. #22
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    I have been trying things one at a time. I just update a bunch of new info all at once. I do prefer the lc4 over the stock plug even if it is cooler because it is less sensitive to the tune. I honestly don't know why but with the lc4 everything runs better but the idle and it is less sensitive to how it is tuned.

    Grizzly03 mentioned that I should tune the engine more lean to get it hotter and to get the engine to idle with any plug does takes lots of tuning. But if it is to lean it won't properly ignite the fuel, if it is to rich it won't be hot enough... It is so sensitive if I turn the low speed needle 1/8 turn either way it won't idle.

    Grizzly03 is right, it's not hot enough. The engine does need a hotter plug and if possible an even higher compression. I'm just hoping an lc3 will be hot enough so that I don't need to find a lathe to modify the compression more.

    I do believe lc3, g5 and p3 are the best plugs for gasoline glow ignition engines. From what I have read they all have the same filament but in different bodies. I have never seen anything but but OS p3 and g5 run gasoline successfully. So I'm going to run the lc3 which has the same filament and it fits my engine.
    Last edited by Bob2.0; 09-03-2019 at 10:11 PM.

  23. #23
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    Quote Originally Posted by USMC1984 View Post
    Admittedly, I know nothing of gas/nitro engines. I have seen both gas and nitro engines advertised on RC sites so my question is why go through all of this hassle if a gas engine is available.
    I want a glow ignition gasoline engine for my rc car. The only glow ignition gasoline engines on the market are the OS ggt15 and the NV gx-40 rc bb revlite. Booth are for rc planes and would be more of a hassle to mount on my car than just converting the engine. The one other option is the gasoline dynamite .31... This one would be a pain to mount to my car, it costs $350+, it has a heavy cdi unit, a piston rod that often breaks, and parts are hard to find. I have only invested $5 into my conversion so far and I don't intend on spending more than $40 total. Next it gives me something to do in my free time. Finaly as long as I use high quality oil and don't over heat it I can't damage anything as shown by the airplane guys. For me it's a no brainer.
    Last edited by Bob2.0; 09-03-2019 at 10:14 PM.

  24. #24
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    Boy that OS g5 plug is pricey $15. Never seen that plug before, has good reviews on running the ggt15. Maybe try that plug,which is made for gas and at a mix of 50:1 in the ggt. Also I hope you know that the more oil in gas lower ratio(20:1)=leaner mix and less oil in mix higher ratio(50:1)=richer mix. "Oil mix ratio" can affect timing, more so in non spark ignition. Need to look at it this way as the more oil added to a mix the less room for gas which in turn actually makes the fuel ratio leaner. Oil itself doesn't burn very well.
    I would try oil mix at 50:1 or higher using(good synthetic/castor) to get it to run and adjust from there. Some 2 stroke oil is rated at 100:1 mix (ex. amsoil saber). I think I would try the g5 before the lc3 plug.
    I like how your trying something and not giving up. If you have trouble mounting the g5 plug, I might be able to help.
    PS. If they made a lc4 with an idle bar, maybe the answer.
    Last edited by grizzly03; 09-04-2019 at 08:50 AM.

  25. #25
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    if you read the actual Manuel to the ggt15 it says to run a 25:1. I don't know why most places say 50:1... But they do.

    I don't want to run the oil lower than a 20:1. All of the small sub 15cc gasoline engines recommend somewhere between 25:1(os ggt15) and 14:1(dynamite .31) for the airplane guys that do these mods they recommend a 20:1 oil mix.

    I'll try the lc3 first because it's 1/3 the cost of the G5 and if that doesn't work I'll try a G5. Next I read somewhere that you want the glow plug farther in the combustion chamber on a gasoline glow ignition engine which explaines the unique design of the g5 plug. So I think I will try removing the glow plug ring and spray the gasket stuff I mentioned previously where the ring went to extend the plug farther in the combustion chamber. If anything else I could try removing material from the top side of where you screw in the glow plug.
    Last edited by Bob2.0; 09-04-2019 at 10:50 AM.

  26. #26
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    I lowered the glow plug by removing the plug gasket. I didn't notice any difference with how the engine runs so I will keep the glow plug gasket because it's easier to get a good seal.

  27. #27
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    I got the lc3 glow plug. The engine idles well and will rev up just fine without the assistance of the glow driver(with lc4 it would idle but not rev up). There is still a noticeable difference in idle rpm with and without a glow driver so I may need to find a lathe to modify the cylinder head for an increased compression.

    I have a diaphragm carburetor coming for the engine today and that should make the engine a lot less finicky and I should be able to use the mid throttle range without the engine dying. I do need to make an adapter for the carb so it may take a while for me to get the engine running on the new carburetor.

    Finally I have 2 stroke caster oil coming soon that should be better for the engine. Also I have some evidence that caster oil will make the gasoline combust better but I can't be sure until I try it out.

  28. #28
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    Like I hoped caster oil has helped the engine run a little bit better than with synthetic fuel. My engine really only has 2 problems now. The first is it will overheat within minutes of starting. Second the carb doesn't keep a precise enough fuel mixture. The stock carb problems are leading to some of the over heating problems and limiting my throttle range.

    Because the engine is still glow ignition it needs a very precise fuel mixture to the point that I can tune my engine to work at low throttle, mid throttle, or high throttle. Once tuning the high speed needle I can then tune the low speed needle so it idles. To help I recently got the smallest diaphragm carburetor that I can and I'm hoping it will be small enough. I still need to make an adapter out of metal or 3d printed nylon.

    To help with the over heating I need a high power fan but I haven't devised anything yet. If anyone has suggestions it would be appreciated.

  29. #29
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    I don’t have any helpful suggestions , but skimming this whole thread it is fascinating and I am enthralled with the progress. Good luck and keep the experiment up.

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