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-   -   Revo 2.5R Compression, Cooling, & EZStart (http://www.rcuniverse.com/forum/traxxas-monster-truck-forum-251/8769185-revo-2-5r-compression-cooling-ezstart.html)

darkfall13 05-14-2009 04:33 PM

Revo 2.5R Compression, Cooling, & EZStart
 
Sorry gonna clump a lot of things in this.

The engine was sealed tighter than Cheyenne Mountain and I finally got my tune right, had a nice lightly colored plug and combustion chamber. Temps were running at 262F just good all around, the catch was the body was off! As soon as I would do a WOT pass with the body on the temps would rocket to 320F. So clearly I need to cut some holes in the thing, or get a roll cage for the full air effect (but man I think they're so fugly). But whatever prompted me I noticed the flywheel or whatever on the underside of the frame for bump starters and turned it with a single finger, I thought I recalled that the piston should reach TDC and you shouldn't be able to turn it any further due to compression, well I could, there was a good deal of resistance but it didn't take any forcing. So is that normal? I've only been through 2.5 quarts, so can't be due to wear right?

Also I was wondering what is a good EZStart battery and charger? I got some 1800mah cheap thing and only after 5 starts it couldn't keep the glow plug lit.

DaveG55 05-14-2009 05:56 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
Sorry guy, I think that you're a bit on the lean side. If you insist on tuning to temps then Traxxas reccomends 240-245 for the 3.3 as optimum, not 260+.

Yes, your engine compression seems to be ok, maybe a bit low but not overly so from your description.

darkfall13 05-15-2009 12:15 AM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
The link you posted to the other thread does not state that 240-245 is the optimum temperature (and this is the 2.5R not 3.3) and that video merely states it's an "acceptable" temperature. But it does say: "Maximum temp for any condition should generally not exceed 270 F, but some conditions or high revving race operation may require warmer operating temperatures." Furthermore a thread on this very topic: http://www.rcuniverse.com/forum/m_23...tm.htm#2342914 from this engine's hayday seems to confirm my constant running hot.

DaveG55 05-15-2009 04:54 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
Hey guy, you asked for experienced help. I've been in the hobby since the 1960's and have had more rc's and nitro engines than I can remember. I currently have three Traxxas engines, two of which are 2.5's, out of about 13 total. I'm telling you that I believe you're running that engine too lean.
If you choose to diregard what I posted then that's fine with me, it's not my engine. And I'm 100% positive that you can search and fine something to reinforce what you already believe. But bottom line, you came asking us for help, I've given you the info you need to correct your heating problems, now all I can do is wish you luck.

controlliner 05-15-2009 05:07 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
R/C cars in the 1960's.... Those were the days. I still have my Veco .19 with the Dick McCoy crank , dykes ring piston in the chromed liner ( this set actually turned the .19 into a 21) I think. It sure was a simpler time, engines were much easier to tune.:D

darkfall13 05-16-2009 04:01 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
Hey guy,

Yeah see you're probably the same kind of person that looks down on all the "n00bs" for not using the search function. I had already done that before making my post, hence ever finding that thread; not a disregarding of your post, as you're so inclined to believe.

But I was merely stating the 240-245 seems quite unreasonable for 3 reasons: at stock needle settings after 1 wot pass of 3 seconds with the body on the engine hits 301F, yes quite terrifyingly high, with the body off, still stock settings it reaches 252F. Also if I tune to keep it that low of a temp with the body on, I have nearly as much raw fuel spewing from the exhaust as I have smoke, with it soon flooding from the excessive fuel. And lastly, on that page, and in that video, they were running without the body.


DaveG55 05-16-2009 10:31 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 


Whatever, you're the one with the problems, my engines run fine. The rest of your trash talk is not even worth a response</p>

Good luck </p>

absolutemayhem 05-16-2009 10:44 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
if you could turn over the motor with just one finger with out using lots of force, it most likley woreout....runing it to lean...( cut holes in your body) i have 5 gallon old motors that require me to dig my nail in to the flywheel grooves to turn it over...richen the hsn 1/16 of a turn and yo should be good....unless your motors wore out...overheating is a sign of a wore out motor..

darkfall13 05-16-2009 11:30 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
Ah yes the rest of my trash talk, thank you Dave. Though I could have sworn you started that, I was merely pointing out things I have found contradicting your claim and would like a proper civil answer in discussing this quandary, as I'm new and want things properly laid out. Not you shoving your experience in my face. But it looks like I'm good to go, shop says my needles were good for our weather lately, merely need to put some holes in body. So I'll have to think twice before posting next time, don't want the wrath to come down.

And mayhem, thank you, apprently just worrying myself for nothing. The thing Ihad read made it sound like it should be impossible to turn, but clearly that's not always the case.


mikel05 05-17-2009 03:37 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
daves rite 260 is way to hot to begin with, in my experience 230 is a little hot for that engine, you r to lean

darkfall13 05-17-2009 04:59 PM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
He very well may be, but the problem is he would not allow for things I found contradictory where I want answers. He may have 40 years of experience and perfect engines galore, but I just want my one to be a strong runner. But now I'm too rich, as my head is shiny and looks new again. So time to get back outside.

Rawlpower 05-18-2009 07:07 AM

RE: Revo 2.5R Compression, Cooling, & EZStart
 
darkfall 13

I can add 2 comments which may or may not help

1. turning over the engine by hand when the engine is hot - should be sticky at the top but not impossible, the taper on the sleeve widens as the engine heats up so it will be relatively easy to turn over. However, turning over the engine by hand when the engine is cold should be quite difficult.

2. my engine is rich on the hsn and the lsn, so rich smoke pours out the back, if I lean it any more it won't change into second, and I find my temps on the high side (270 - 280) so I have resorted to cutting the whole windscreen out of the body in order to help cool the engine.

The best is to tune for smoke and performance, and use the temp as a backup consideration.

If you are running way too lean, then the enginecould cut out whilst accelerating at thigh speeds, you will burn glow plugs, also under extreme conditions you will see pitting in the piston head, but by then its too late and the engine is probably damaged.

I hope this helps


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