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Old 04-10-2010, 09:01 AM   #1
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Default Sirio .21 STI AAC

Hi all what are the temps required to run these motors? 230 F???

Thank you!
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Old 04-10-2010, 01:36 PM   #2
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The engine temp depends on many things, so I wouldn't shoot for a specific temp, but they typical run in the low 200's with 30-percent fuel and ambient temps around 60-80F. If it starts getting in the middle 200s, then you should probably take the time to re-tune the engine just to be sure you're not slightly lean on one of the settings. It's a great engine with smooth power and unmatched top speed. Just keep it in tune and you'll get a lot of good runs out of it.
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Old 04-10-2010, 02:06 PM   #3
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Thanks for that Steve, I am running at 200F so I will crank it up a bit, running on 25% though. Any idea of a good head clearence?

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Old 04-10-2010, 02:30 PM   #4
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I would set the head clearance between .020 (0.5mm) and .025-inch (0.64mm). Don't go below .020. If you're running fuel with high oil content, then cheat to the higher side. 200F is fine. Those engines run cool, so don't look for a certain temp. If the engine runs better by leaning it slightly, then that's where you should set it. You're in the right range and you should be down to VERY small adjustments at this point. Just use the temp gauge to be sure that you're not above a certain threshold, but let your throttle finger be your guide for everything else. If it runs better, then you're headed in the right direction - if it doesn't then you're not.
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Old 04-11-2010, 12:23 AM   #5
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Sounds good, putting it down today again. I am using 8% oil. My first is 6% synth and 2% castor but have a second mix with 8% pure synth. I was using 6% synth and 4% castor but find with the lower oil ratios motors are running cooler
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Old 04-11-2010, 12:49 AM   #6
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I don't like the idea of running an AAC motor with no castor in it. I have seen piston failures.
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Old 04-11-2010, 10:55 AM   #7
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What is the difference? I know the sleeve is aluminum, but it's still chrome plated? Is the piston made from something different then other manufacturers? What say you Steve P. I know you have a lot of experience tuning these engines.
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Old 04-11-2010, 11:37 AM   #8
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I am using Motul Micro T2 synth and its flash point is higher than castor. AAC run cooler than ABC so will see how it goes. Yes AAC, alu piston, alu outer sleeve and chrome inner sleeve. They make good HP at lower temps I find. Hey wingracer how you finding the German Shepherd AKA the Dog!!! Have mixed emotions, think it could land up in a kennel some days
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Old 04-11-2010, 11:56 AM   #9
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Yesterday we were testing a new version of our engine, it has an integral AAC cilinder and were running a low cooling capacity head and on full speed we were running 80 degrees celcius, that is about 175F. With a better cooling head we were running about 95 degrees celcius (200F) so there was heat from friction between piston and sleeve.

Some castor oil is not only good for AAC, it is good for any engine. It does give a better lubrication (it does not burn compleetly with the combustion), it gives a better cooling and because it thickness it will better the compression as a hydro piston ring.

I think that last one is important with AAC. An aluminium sleeve will flow the heat more directly to the cooling head so running a track there is more heating up and cooling down in the sleeve wich gives a more fluctuation in the expansion. A thicker oil which does not burn away will fill up the space between piston and sleeve.
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Old 04-11-2010, 12:04 PM   #10
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I am using Motul Micro T2 synth and its flash point is higher than castor. AAC run cooler than ABC so will see how it goes. Yes AAC, alu piston, alu outer sleeve and chrome inner sleeve. They make good HP at lower temps I find. Hey wingracer how you finding the German Shepherd AKA the Dog!!! Have mixed emotions, think it could land up in a kennel some days
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Old 04-11-2010, 10:20 PM   #11
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Quote:
Originally Posted by wwoodruff View Post
What is the difference? I know the sleeve is aluminum, but it's still chrome plated? Is the piston made from something different then other manufacturers? What say you Steve P. I know you have a lot of experience tuning these engines.
Yes, of course the sleeve is chrome plated. I've rarely damaged a piston, and when I did it was with lots of of caster, so I'm not sure there is a connection. Sean is an experienced racer so I have no doubt that he's witnessed or experienced this, it's just that my experience has been different. 8 to 9-percent lubricant is plenty. I've run as low as 4-percent, but that's pushing the limits. "Organic" content such as castor oil tends to create carbon deposits on the top of the piston and in the sleeve. It can actually make the fit between the piston and sleeve tighter if you get too much carbon build-up. For me, the jury is out on any requirement for castor oil. I've used complex synthetic oils that can be run in much lower concentrations and had good results. I've run pure castor blends and also had good results. I believe that, if you run or blend fuel with high quality ingredients with oil content that's in a safe range, there's not much you can do to hurt these engines.
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