briangp

So I have an ASP red-head 1.08. From everything I'm reading, I need less than 5% nitro fuel. The local shops aren't carrying anything less than 10% I'm not into mixing my own, not to say that I wouldn't be down the road... but I would like to be able to run this motor up this weekend.

My question is can I dilute pre-mixed fuel do bring it down to &lt;5% nitro? If I get a heavier oil mix can I just add some methanol to it (some math would be involved) and dilute? I already have a gallon of 15%, and I can go buy 10%, not nothing less.<br type="_moz" />

ThumbSkull

My Feedback: (57)

Add a head shim.

briangp

Read about that too, while I understand this is an easy solution, where in the hell am I going to find a shim for this motor that is discontinued, and what are the detriments to performance?<br type="_moz" />

spaceworm

Yes, but watch to make sure to keep up the oil percentage. You can add castor oil to up the oil after diluting. I actually run straight methanol mixed to 20 percent oil with Klotz Techniplate which is synthetic and castor. I use this with no nitro in my ASP 90. My Evolution did not run that well with no nitro so I mixed 2 parts of my no-nitro mix 20 percent fuel with 1 part 15 percent nitro/20 percent oil fuel and got 5 percent nitro for the Evolution with the 20 percent oil. You could mix two parts menthanol with 20 percent oil to one part 20 percent nitro and 20 percent oil to get about 7 percent nitro and 20 percent oil. Mix a small amount and let sit awhile to make sure the oils do not separate out. Castor and Klotz and what ever oil mix wildcat helicopter fuel has in it works fine for me. I get my methanol at a speed shop and my Klotz from tower. Get castor from Sig or the drug store. Good luck.

Regards,

Richard

ThumbSkull

My Feedback: (57)

A head shim slightly lowers the compression allowing you to use higher nitro without pre-detonation which robs power.
I would head to a well stocked hobby shop with the dimensions of yours and take a caliper and find another that's the same size.

spaceworm

MAN reviewed the ASP engines when they were first released and found that it took 2 head shims to allow even 5% nitro to be used without detonation. I did not believe them and tried it on 5 percent with no shims.The engine would not run right, it overheated and it blew out glow plugs on every attempt to run it. Just engines is/was the distributer for ASP and I tried to get shims from them, but they did not have any for that old of an engine. So, FAI, no nitro fuel is it for my ASP and it runs great for me!!

Regards,

Richard

briangp

Good to know! I've been reading that people running 5% nitro are using colder plugs to prevent detonation. Might help you, who knows.

Thanks guys.
<br type="_moz" />

jeffie8696

If you mix up a gallon of methanol with 20% castor (or Klotz ) you could then mix it half and half with the hobby store 10%and get two gallons of 5% fuel.
Easy peezy.
Or 2 gallons of the methanol fuel and get 3 gallons of 3.33% nitro.
Ifind it hard to believe it will not run well with a colder plug and 10% nitro.

carrellh

For $5.49 plus shipping you can try the head shims for an OS 1.08
http://www3.towerhobbies.com/cgi-bin...6176&search=Go
If it fits, get several and adjust the compression as much as necessary.

If you get the compression ratio adjusted so the engine runs correctly on the fuel you like to run in your other engines, the performance should be fine.

It is possible to make head shims by cutting up an aluminum soft drink can. I'm not sure that I could make them but I have heard guys at the field talk about doing it in the past.

Mr Cox

You can make a gasket out of a can or any sheet metal, like aluminum, copper or brass. At a thickness of about 0.10mm it is very easy to cut and trim with a pair of scissors, there is nothing to it. Size is not that critical as long as the surface is smooth and the material soft enough go give a good seal. I think you would be better of to use a fuel that you can easily get (more consistent fuel in the long run) and just trim the compression to suit.

briangp

Pop cans... nice... I can feel the slices in my fingers already! LoL Might be worth a shot. I might even be able to come up with shims at my work, who knows....

So the shim just needs to be the same size as the top of the cylinder wall and slap the top on? What would be my tolerance for 'overhang' if I wasn't able to trim it as close as I wanted to? Thinking an exacto knife might actually cut pretty well against a piece of pine in this case. I'm running 15% in my other motor (K&amp;B .61), but I think I'll switch to 10% and call it a happy medium, I know the motor is reccomended for less than I am running. Still awaiting to find out if the last LHS has FAI fuel. I also discovered I have a source of methanol in large quantities at a substantial discount As for an oil I could use Klotz if I find it locally, or I have MobilJet 254, which I hear will mix and runs at about 15%.

carrellh

Some motorcycle and go-kart shops sell oils that will blend with methanol, or it can be mail ordered in various flavors:
http://www.sigmfg.com/IndexText/SIGKZ001.html
http://www.sigmfg.com/IndexText/SIGCO001.html
http://www3.towerhobbies.com/cgi-bin...SM&C=PFE&V=KSF
http://searchrc.horizonhobby.com/ind...500&N=5034+565

briangp

How much shimming would I need to do to bring myself upto a compression that will allow 10%? I heard in another thread that a guy did 1 shim for every 5%...however I don't know what size the standard shim is.

AMB

Briangp Why not order a couple from Just engine in the UK they can mail in a plain airmail envelope martin

carrellh

I do not know if there is a "standard" thickness. There will be a bit of trial and error. I'd probably make 2 and run it. If it still overheats, or has other problems, add another.

As far as overhang tolerance, you want to avoid overhang inside the ccombustion chamber as much as possible. The whole "sliced fingers" thing is a bit scary, which is the reason I'm not sure if I could make them. I would be very tempted to spend the $$ on the OS part and hope it fits. If it does I'd get three or four total and start experimenting.

carrellh

According to post 6, they do not have them.

NM2K

My Feedback: (14)

It doesn't work that way. Your operating atmospheric pressure, humidity and temperature factor into the equation, as does the prop size and the heat range of the glow plug that you are using. Even your high speed needle setting can make a big difference. But, the only way to learn and keep it in your noggin' is to do it.

Engines that are over compressed for the amount of nitromethane or prop load being used, not to mention a too hot glow plug, will tempt you to tune the high speed needle very rich. This does retard the timing and it helps the engine tolerate the conditions that are existing, however, it will leave you with a very rich midrange mixture, which can lead to dead sticking and raggy acceleration from idle to full throttle. What to do?

Drop the prop size if you don't have any way to reduce the nitro or the compression. Or, change to a colder glow plug than you are presently using.


Ed Cregger


Oh, one more thing. There is no such term as predetonation. pre-ignition and detonation are two completely different terms, which mean two completely different things.

MetallicaJunkie

im pretty sure the os would fit

briangp

Thanks for the input guys..... I still have one last resort to find the right fuel but they don't open up for another couple hours....


Anyone have experience or a take on using 254 for an oil? I figure its gonna be trial and error, but it would be awesome if it works since I have a pretty unlimited supply of methanol and 254.<br type="_moz" />

spaceworm

There were at least three series of the ASP, The first version is the one I have thet just Engines/UK does not have parts for any longer. They may have the other series parts. Worth an email to them to find out. The early (at least) ASP were clones of the OS FSR (I think), so maybe the head shims for the OS engine would fit? Soda or beer can aluminum is very thin and easilly cut, but also pretty high temper and may not be soft enough for a head shim. Thin annealed copper would work, as well as some of the dead soft aluminum that is used as tape for air conditioinig duct work. Printers alluminum offset press plates are thin and easilly cut, but are alo high temper. Couold the can stock or printers plates be annealed to a soft temper by heating? Comments?

Regards,

Richard

briangp

The 'last resort' hobby shop finally opened up tonight and they had Sig 5% in stock, so I went ahead and bought a gallon, dirt cheap at that %.... Forgot to buy a plug, but I have a spare #6 that will probably work. If I have to, they have Klotz castor in stock and I could home brew some FAI. We will see what happens... with 5%, a pop can shim would probably do the trick should I need it.... Bought a 16x6 zinger prop for it. Gonna try and run it tommorow night provided I have time.


Will keep posted.<br type="_moz" />

spaceworm

FWIW, here is the article on the ASP .91 from MAN regarding compression ration, nitro content, and head shims.

Regards,

Richard

briangp

Great article! I'll take this into alot of consideration. It will probably be exactly what I had planned on doing since all I could find OTC is 5%. Its interesting to read that he said they ran really hot. I'd be curious to know how long he ran those fuels at a time. Reason being, when I broke in my K&amp;B .61, it also recommends a fairly low nitro fuel, 10% if I remember correctly. I bought 15%, remembering this is what it ran on for the short period of time it flew many years ago. Anyways, the 15% ran hot as hell and would shut down after about a minute at WOT. I opened up the high end to super rich, to the point it would barely run and kept it at about half to low throttle for awhile. Ran a couple tanks through it this way. Needless to say, after about an hour of this, I adjusted the low end one click or so, leaned it out and she ran perfect, amazing throttle response. Still mildly warm, but not uncomfortably hot like it was before. Never had a dead stick once. Now it starts on the first flip, never used a starter on it, warms up in about 10 seconds and purrrrrrs at a really low idle. I'm wondering if I'll have the same experience with this 1.08.

briangp

Just a follow up for everyones information....

Finally ran the 1.08 today with the stock 5% SIG fuel (20% oil)... took a little bit to start it, it was so stiff from sitting around, we blew it out by pulling the plug and running it with the starter.... UGLY brown **** comign out.... lol Put the plug back in and it fired right up! Adjusted the high speed needle to a little under 2 turns out and its running extremely smooth, idles super low, and transitions to high throttle like a chain saw! I broke it in on a pole with a 15x8 prop on it... I don't think it even knows theres a prop there! I'm running no shims, and 5% and purring like a kitten! Its not getting hot at all, we ran about 5 ounces of fuel through it with a couple seconds of WOT, and about 10 minutes of idling. Its not loading up at an idle... I couldn't be happier with it right now....<br type="_moz" />

jeffie8696

Sweet, glad it worked out without a bunch of hassle.