Advice needed

[Reddog]

I blew the engine on my t-maxx. I tore it apart and found the connecting rod broke and the piston stuck in the sleeve. The part I am wondering is this. I have been running Cool Power 15% synthetic fuel with no problem. I just switched to O' brand 20% as the hobby shop is not going to carry cool power anymore. My engine blew about half way through the first tank of the new fuel. Did I do something t cause it to blow or is it the fuel?
To let you know I have an old T-Maxx that is a mix of several generations of the truck. It was running a TRX Pro .15. I will be putting a .25 in to replace the .15, little more power and I can get one fairly cheap(this is just a fun truck, no racing).
Thank You, Shaun

 

[mrbones]

Probably wasn't changing fuel that did it. Traxxas connecting rods do not have a brass bushing in the end that runs on the crank pin so it probably just finally failed. Running too lean will smoke the rod also. And now that you have switched to Odonnells (I assume) you have a blend of castor and synthetic oil which is what you need instead of just straight synthetic. I read a little about that cool power 15 and I think that is for helicopters. You need to run at least 20% in your .15 or .25.

 

[Sixtysixdeuce]

I read a little about that cool power 15 and I think that is for helicopters.

Yeah, appears to be an aircraft fuel. Low on nitro content, high on oil and, as stated, not formulated correctly for car engines.

Always buy car fuel for cars, boat fuel for boats, plane fuel for planes, etc.

 

[Reddog]

Well that is kinda what I figured. I know that I should run the right fuel for the vehicle but this is what I had and the old maxx ran good on it so I just went with it.

 

[Reddog]

Well I showed my engine to a nitro guru. He took a long look at it and told me that running the air fuel is what kept it alive as long as it did. The extra oil held it together a little longer. Also told me that it is repairable and to run the right fuel. He was impressed that it ran as good as it did on that fuel though.
When torn apart there was the remains of a brass bushing in there. I though it was from the rod but he said it was from the starter. Old Willie wont be down long, my daughter will not let me set it aside.
Thanks for the help, Shaun

 

[rbpwrd240]

I have a very similar truck. I choose to go to an O.S. .18mill 1.3hp and reliable as all get out and easy to tune. It will accept your current side exhouse header and muffler configuration where the 2.5 is a rear exhoust with a different manifold. to go 2.5 you will also need to get the carb linkage to operate the slide carb since your .15 has a rotary carb.

You may have known all of this as most of us do but what you may not have known is that the O.S. mill for 150 bucks and bolt in option should outrun the 2.5 and it should be easier to tune and more reliable.

Just my .02

 

[Reddog]

Thanks. I would have gone the os route except I already bought the 2.5. The carb being different completely slipped my mind so I will have to get a couple more parts.

 

[Reddog]

I got the 2.5 in the mail today. Mounted right up with no issues. I am building a linkage to get me by until the new one arives. It runs awesome. Had it running in the shop for several minutes before I relized I had forgot to turn on the vent, oops. Will post some pics later. Thank you all for your help. Shaun

 

[Reddog]

No pics yet. But if anyone is looking to upgrade there old 1.5 to a 2.5 there were a couple other glitches I had to deal with. Being as I left the ez start in place and will use it until I tire of carrying around all the extra weight in my pocket, the top screw closest to the fuel tank needs to be removed or it will pinch off the pressure line. Second the exhaust mount needs to be bent oddly to fit right and third the air cleaner mount has to be redone as the mount does not line up correctly. All of this is minor, but for anyone looking to just bolt on and go this was not as easy as I had thought it would be at first, but my maxx has several put into one so mine is an odd duck as it is. Shaun

 

[srusinek]

I might get flamed for this but here goes: I've got a Pro.15 out of my first gen tmaxx that I put into my rc10gt that has around 3 gallons ran through it, it was never broken in correctly(first ever nitro engine), has an aftermarket cooling head on it, has only seen fuel with oil content north of 12% and has always seen after run oil. I'm a firm believer in if you treat your mills correctly then they will last a long time. I went the OS .18 cvrx route because I was afraid that anything more would eat the drivetrain alive. I since have switched the entire driveline over to 2.5 spec, added some RPM arms, traxxas performance shocks, traxxas blue pipe and other goodies. As far as fuel goes I used to believe in high oil content fuel(byrons rtr 20% and traxxas top fuel) until I ran Byrons race gen 2000 which only has 12% lubrication. I'm quite sure the plane fuel didn't help but running O'donnell fuel with only 8% total lube(if you ran the race fuel) did you in especially if you didn't change the needles. O'donnell makes great fuel but 8% lube is just too thin for my taste.

 

[hulkmaxx]

I might get flamed for this but here goes: I've got a Pro.15 out of my first gen tmaxx that I put into my rc10gt that has around 3 gallons ran through it, it was never broken in correctly(first ever nitro engine), has an aftermarket cooling head on it, has only seen fuel with oil content north of 12% and has always seen after run oil. I'm a firm believer in if you treat your mills correctly then they will last a long time. I went the OS .18 cvrx route because I was afraid that anything more would eat the drivetrain alive. I since have switched the entire driveline over to 2.5 spec, added some RPM arms, traxxas performance shocks, traxxas blue pipe and other goodies. As far as fuel goes I used to believe in high oil content fuel(byrons rtr 20% and traxxas top fuel) until I ran Byrons race gen 2000 which only has 12% lubrication. I'm quite sure the plane fuel didn't help but running O'donnell fuel with only 8% total lube(if you ran the race fuel) did you in especially if you didn't change the needles. O'donnell makes great fuel but 8% lube is just too thin for my taste.

No flaming. 12% oil content is the lowest I would run. Also castor oil fuel is in my opinion might not mean much, is the best way to go if your a basher. Unfortunate for me I can longer get any brand local with the castor oil. Not that the synthetic is bad but it does have a much lower break down heat rating than castor oil's. I have since switched to Torco which is synthetic oil only at 14% oil content. I have broken in two engines and ran a total of 7 tank's through both engines so far. The Torco seems to be one of the smoothest running and coolest running fuels I have tried. Just thought I would toss the castor oil info out there.

 

[Reddog]

Nope the plane fuel aided nothing. I know this, but it is what the LHS had in stock and what I had left from my planes. The engine that came on my T Maxx was an OS 15. It had very little compression so I replaced it with an old traxxas 15 that a buddy had. It had many gallons of fuel through it and was about wore out. Now I am running Odonnels Speed blend, again as it is what the LHS stocks. Never had a lot of luck with Top Fuel. As of right now the only problem I am having is that I cannot for the life of me get my 2.5 to idle. I know it is something simple but no idea what. I have the idle screw all the way in and still it will not idle.
Thank You, Shaun

 

[Reddog]

Well I put the 2.5 in and got some nice results. Runs good and I am happy.

Short video, but the sound is out of wack due to being between two houses, both still have slate and aluminum siding. Shaun