richrd

Hi guys our club racers had to change from the discontinued TT pro 25 to GP-28 so I got to get it broken in. Since it took two years to get the pro to loosen up I was curious is their a way to break in an engine faster? You know the first one to loosen up may win the first few races…[&:] Go with small prop and let it rip a little hot? What ways do you guys use to break in a race engine ?
Thanks Rich

happypappy

My Feedback: (10)

I use the manual for break-in plus a little extra oil in the fuel. Broke mine in on a stand and just let it run and run. As far as stock class racing goes you know darn well the smoothest and most consistant flyer will win when all things are equal ! I fly the Club 40 planes in stock pylon racing and its way close...screw up on a single pylon and you're done.

ChrisAttebery

My Feedback: (15)

Take whichever prop you plan to fly it with, clip 1" off the total diameter. Fire it up and lean it down to where it is running clean but slightly rich. Make sure the motor is getting warm. You don't want to run it cold. Run 1/2 gallon or so like this and it will run like a top.

richrd

Great idea cause we get a new prop every race so got lots to take down 9*7 to 8*7 try it out to night.
Yea all i got is 1/2 gal left so that my be it before bolt on plane. To nite is the night i start.
BTW nice looked new design all parts spin off with one tool
Thanks Rich

richrd

Update, Great engine, clean build it fired right up an spun up to 11,400 on cut down prop as said above. After 1 quart all same pinch wow it's going to take forever to loosen up......
BTW changed from unknown old plug to OS#8 last couple tanks an increased to 12,100 and less smoke no change to needle got set as lean as i dare tryen to take some pinch out. So tight after one quart an still can stop the starter.... wow an for app. 70 bucks
Rich

DarZeelon

Rich,


Why is it that you think the 'pinch' should be taken out???
A tapered-bore engine has its sleeve tapered on purpose. With the engine cold it must be tight as the piston approaches TDC.

It is a feature - not a bug...

Most knowledgeable engine people regard any such engine that has no pinch, as one that has already "gone south".


How did you do the break-in?

ChrisAttebery

My Feedback: (15)

Hey Rich,

Try a hotter plug like the A3. It will help it burn the fuel more efficiently and make more power. Try to run the hottest plug that you can. They should be a light tan color when you've got the right mixture and plug temp. The wire should be shiney to a little frosted.

Dar's correct, you want the pinch, but you don't want it so tight that it overheats when run at a reasonable mixture.


Chris

daven

My Feedback: (1)

What prop did you cut down, those rpm sound low for breakin of a racing motor??

Sport_Pilot

Some of my best runners have no pinch when it is hot out. Very slight pinch when cold.

Sport_Pilot

No the right plug is best, it may be the hotter one or not. It has noting to do with burning the fuel. A hot plug advances the timing, like rotating a distributor on a car. To much, lost power, too little also results in lost power. Test plugs by the highest revs AFTER readusting the needle. When you change a plug you should always reneedle the mixture.

richrd

Dar just kiddin about the pinch thing being totally gone. Trying to break in the fastest way to a prefect pinch if their is such a thing. The prop daven.. is home made 9*7 cut to a 8*7 we race only 9*7 s which i think really loads it down, the pro-25 avg. 9800 if you got it over ten then you have one of the better running engines on race day. The real question i started this post was how to wear it in without over doing it thoughts of compound's in piston was out of the question so maybe cruel power an big prop for heavy load ?? so curious what some of you guys have tried. Iam right now going smaller prop an higher revs than Iam going to get on race day. Still this morning it felt like new so wow not getting to loose yet. Iam going to go just 100 off peak for another qt and see. Then put race 9*7 prop on an try different plugs the KB L1 was the fliers favorite I had luck with a glow bee ? sp.? go figure. Also the fox miracle was good to. Having fun with this TT GP-28 any way.
Rich

Sport_Pilot

If that plug was the favorite they your rules apparently allow some nitro. Though it varies with the engines compression I think that was the best plug for 20% nitro on a TT .46. That is it's not a real hot plug, slightly cooler than an OS #8. If you are using a lot of nitro you might want to check out the Fox #8 plug, its also cooler than the OS #8.

daven

My Feedback: (1)

The K&B 1L is a good plug for what your doing.

I would suggest a little more breakin with an 8x6 prop at higher rpm.

A couple other good plugs I have used for sport racing are the K&B HP, and the McCoy #9.

bob27s

My Feedback: (19)

Some good advice here..... follow it.

the 8x6 is what Id be using for break-in. Maybe a bit less prop to start with.

Just for reference, my TT40 pro engine break-in proceedure (for 424 q-500 racing)
- I use a 9x6 clipped down to 7.75" diameter. Engine goes on the test stand running at 17,000 rpm, clean 2c while slightly rich (but not cold runs at temp and rpm at the same time). Goal after 10-20 minutes running like that is an engine that then turns 16,500+ peak ground rpm with the full 9x6 prop, and can be launched just over 16,000 with no concerns.

Are you saying you race the 25/28 engines with a 9x7 prop ?? Thats quite a bit heavy. Those little engines really should turn up over 14,000 to produce any reasonable power. If you are loading them to achive quiet... thats another story.

Loading the engines like that and only 10,000 rpm is just hurting the engines - they are struggling, and you folks are probably running them very rich to compensate. My quick thought on the situation is THAT is why it took 2 years for any reasonable performance stability/break-in to occur on your existing engine.

Bob

richrd

Yea thank all

Bob yes we all pick one out of a box each race day "once a month" and all use same fuel can SIG 10% champion. An plane is custom designed by a member we all buy the kit from them our LHS is all our field provider. So yea I only ran the pro in the plane so took forever and did not want to beat the racer up on breaken it in. So now we all got new GP-28 Iam using the most common suggestions here an chip down the prop. Last night on start of third qt it started to change it’s pitch an move up over 12000. Still hard to start but last night on third qt I could flip start for first time. This time I want the engine to be as close to peak break in as I can with out going over the top. "Peaking the pinch ?" Only thing we can adjust is needle, glow plug and flying skills..an BTW my son does the flying Iam just pit crew. .So we all try to get lean as we can but half way thu race you can see the tail tail slow down an no smoke if lean to much, I finially went to a 3 line setup with pressure line on bottom of tank "sorry senior moment forget what it's called" but it gave me more needle adjust room an less effect at end of race so it seemed to hold that lean set longer but still only faster than 1/3 of the guys but most have 5 or more years on their engines.
Rich

ChrisAttebery

My Feedback: (15)

Man, I'd be suggesting a new prop for that motor in a hurry. We run 9x6.5 on our 46AX powered T-34 racers out here. That poor motor is lugged down for sure.

Keep putting fuel through it. It will help keep it from overheating and leaning out during the heats. You really don't want to lug down a motor that is barely broken in.