ProBroJoe

Hello again,

I'm interested to hear what others have done with their SureStarts / reedies. (i.e: hop-ups, mods, conversions, etc...) How about it Tim - care to share how you do your disk rotor conversions? Anyone baseline one of these engines and have "before and after" numbers? Just how far can you take a reed valve .049?

-Joe

combatpigg

My Feedback: (3)

I think a good baseline with a 5 x 3 prop is about 18000. After you shorten the piston and thin the skirt, the RPM might go up to 20,000. Now, if you mess with opening up the intake passage, you are commiting to a high revving, small prop engine that won't suck fuel as well with a big prop. I think you can drill the intake to .180" and still have enough plastic left over to hold the NV body when you press it back in. I think rigging up an upper NV support and seal is critical to competition level consistency. Polish the crank, set the rod with zero slop, and get the NELSON plug and you will be ready to run at 24,000+++ with some 50% fuel and an APC 4.2 x 4 prop.

Remby

My Feedback: (3)

The fastest way to increase the H.P. is to sub-induct a newer, slit type cylinder. This will only produce equal power like the older, open exhaust models from the 70's/80's, but the mod can be done & is fairly easy, too. More than one way to do this, piston mod or cylinder cut.

Remby

t_kwink

I have a reed valve engine spinning an APC 5.7-3 prop at 20,100 RPM, or a 5.5-4 MAS prop at 18,400 RPM. I don't belive I've heard better numbers for these props with an .049 yet.
The biggest gain in RPM came from minimizing the crankcase volume, and a better glow plug. I am running a Norvel glow plug, witch seemed to gain 100-200 RPM over a high compression cox. Others are running the Nelson plug, and it is probably worth a little more.

Wink

t_kwink

I stand corrected. I found an old post on here with someone running 21,000 with an APC 5.7-3 on a Fora .049. Oh well, guess I gotta keep working on it...

Wink

flyinrog

My Feedback: (1)

Hey t long time no see,,you gonna make it to the 6-18 flyin up here?...Rog

t_kwink

Same place? I would like too. I have a titanium connecting rod for my reedie done, and I'm just finishing the alluminum piston. Maybe I'll bring it and a test stand, and we can make it fail together!

Wink

ptulmer

My Feedback: (5)

Wink, that may be sooner than you might think! Titanium will corrode in the presence of methanol. There's more to it than that, but you will definitely want to look into it. Sorry for the bad news. I had thought about making an entire engine out of titanium... 'til I read up on it. I think it was organic solvents in particular, not sure if white gas fit into that too.

t_kwink

crap. I know people use titanium valves on alcohol race motors, I thought it would be O.K. I know it doesn't like Brake Clean at all. I can't imagine it coroding that bad in such an oil rich environment (castor) would it? Is it just a corosion or is it a chemical/acid reaction?

Wink

flyinrog

My Feedback: (1)

were you at the funfly? I know ther were several visitors...ummm no its at the other field about 15 miles away...I'll put directions up closer to the event...Rog

t_kwink

I hope it's 15 miles closer. just kidding... the drive's not that bad.

Wink

ptulmer

My Feedback: (5)

Complaining about the drive!!!?[sm=lol.gif] Try 7hrs!

I don't remember at the moment what the problem was "exactly". I'll look around again, the info was not easy to find, but in the meantime.... maybe one of our resident experts can pipe up. (please!)

t_kwink

Yeah, I've been thinking about it, and I can't see a problem with titanium in our fuel. I know it's O.K. with gasoline, motor oil, ethanol, mineral spirits, and laquer thinner. The only thing I've ever heard that is bad for it is "Brake Clean". Of course, I don't have a can to see what the ingridients are... I did read that titanium is not a good bearing surface, but what the heck, you have to try.

Wink

ptulmer

My Feedback: (5)

http://www.azom.com/details.asp?Arti...l_Environments

Imagine....adding water to your fuel for corrosion protection! Nitromethane is not really bothered by water in the fuel. Adding 4% should not affect performance. I might even rethink the whole engine thing.

t_kwink

Thanks Pt, that is very interesting. Your were right about the methanol, but I'm not going to worry about it much. Maybe I'll throw a piece of the titanium I'm using in some fuel for a week, and take a look at it after.

Wink

ptulmer

My Feedback: (5)

I'd REALLY appreciate hearing your results! But seriously, that little bit of water wouldn't hurt performance. There was an article where a guy purposefully put water in his fuel to test it and he ended up putting ALOT of water in there before he could see a difference.

ProBroJoe

Thanks for the replies guys, but I'm afraid it just brings up more questions!

How much do ya'll trim off of the base of the piston? .010-.015"? More?

How in the devil do you thin the skirt with the rod in the way? By how much?

-Joe

combatpigg

My Feedback: (3)

HI PBJ. I take the piston up to TDC and score the skirt right at the lower edge of the exhaust port. Take out the piston/rod and chuck it up in a lathe. I will cut the piston skirt about .010 beyond the score mark. Now I just take an XACTO freehand and use it as my shaving tool, you can get those walls pretty thin, and it doesn't take long. The piston will be noticeably lighter when you are through.

Tim Wiltse-RCU

Joe,

The catch 22 with the Sure Start engines is that they have very good bypass porting in fact it's the same as the Venom and Killer Bee(Those engines are the "power houses" of the factory reedies). The bad part is they don't have any Sub Piston Induction. But hey they didn't need it as they were meant to just pull around the Cox control line planes and never meant to be "Racing engines". I think the real key is just trimming the skirt for SPI and then adding a Galbreath Head/Nelson Plug Combo. In shortening the skirt you will also be lightening the piston too! Classic two birds with one stone deal. I try and keep the SPI to around .012/.015. My current engine is running .019 SPI and seems to run just fine. Just check it with a feeler gage. If your wanting to thin the piston you can hold the rod off to the side with a piece of wire.

LAter,
Tim

boberos

Tim,
Only slightly off topic.
I thought SPI was bad for throttling. So if these Sure start anniversary specials don't have it, would they not be better suited for throttle rings? My preference is for throttlability rather than all out power.
Bob G

Tim Wiltse-RCU

Oh shoot did I miss something? Joe, did you want to throttle this?

Later,
Tim

combatpigg

My Feedback: (3)

With SPI in a COX engine, you usually have a liner with the big bypasses and large intake track. This is where the poor throttleability comes from. The connection/ blame gets passed onto the SPI, but I have a couple of high performance .40s that have a skirt short enough to see into the crankcase, but these engines throttle perfectly, and they do so with pretty large intakes. I think SPI is a fancy term, but I don't think much intake breathing activity can take place here. It is mainly done to lighten the piston and uncover the transfer ports sooner at BDC. SPI should really be called SUP for See Under Piston. I have SUP'd a couple of BIG MIGS and they still throttle very well. At the stage of the intake cycle when the piston has swept mixture into the engine and it is at TDC, half of the so called SPI time period has occured, but the other half hasn't happened yet, and this is when the descending piston still has that SPI window open and it would be pushing anything that was taken in right back out. Of course, I'm talking about a moderate amount of SPI, it could be taken to the extreme where it actually interfered with the intake cycle or even when transfer is supposed to occur.

ProBroJoe

Cool! This is just the kind of info I was looking for...

Now, I wonder if it would be of any benefit to open up the exhaust ports to the full width? You'd think it would help the engine breathe a little better... but then again, the Killer Bees were the 4 slit exhaust, huh? (but the bottom slits were wider?) What's up with that? The piston doesn't even fully uncover the bottom slits at BDC on the SureStarts...

BTW Tim, you didn't miss anything - a throttle won't be needed on this one. Heck, the truth of the matter is that I don't even have an airframe in mind. I just figured that since the SureStarts were so cheap they'd be great candidates for experimentation and to do some learnin' on...


Thanks bunches guys,

-Joe

combatpigg

My Feedback: (3)

These SURESTART engines can absolutely scream with no additional [risky] liner work done what so ever. I haven't put a SURESTART P/L set on a TD crankcase yet to evaluate the exhaust port design, that would be a worthwhile thing to do.

Tim Wiltse-RCU

Joe,

The bottom slit on the Killer Bee is wider because it has SPI. And by moving the slit down is what gives that cylinder the SPI.

Later,
Tim