R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro Off-Road

Reply
 
Thread Tools Search this Thread
Old 11-03-2008, 01:35 AM   #1
Tech Regular
 
mini696's Avatar
 
Join Date: Mar 2004
Location: AUSTRALIA
Posts: 304
Default Engine seems to run hot... Yet there is nice trails of smoke.

My engine has peaked at over 300deg (F) during a quali run at my last race. Yet there is a nice trail of smoke at full throttle, as well as when blipping the throttle and at low speeds. It even bogs down when taking off from a standing start after sitting for 10sec. I pinch the fuel line and the revs rise a bit then the engine dies.

So all that said... I am please I have the engine running well (a bit on the rich side). All except for the temperature thing.

Now I know in another thread I said I dont tune to temperature (which I dont) but 300deg concerns me a bit.

Ideas why it runs so hot?

Engine is an AXE Rossi Sport .21.
Ambient temps are high 20's (Celcius).

I thought there may be an air leak somewhere, but the tank is fine, and using soapy water I tested the engine (cold) and found nothing.
mini696 is offline   Reply With Quote
Old 11-03-2008, 02:54 AM   #2
Tech Regular
 
lowey79's Avatar
 
Join Date: Dec 2007
Posts: 356
Default

In a buggy or truggy? if it runs nice with good smoke and pinch tests ok, i would look at trying for better airflow around the head..... where are you reading the temp from?
lowey79 is offline   Reply With Quote
Old 11-03-2008, 03:09 AM   #3
Tech Regular
 
mini696's Avatar
 
Join Date: Mar 2004
Location: AUSTRALIA
Posts: 304
Default

Buggy.
This shows the cooling.


This shows the temp guage (red shrink wrap), its a Venom moniter.
mini696 is offline   Reply With Quote
Old 11-03-2008, 03:53 AM   #4
Tech Regular
 
lowey79's Avatar
 
Join Date: Dec 2007
Posts: 356
Default

Try temping it with an IR temp gun and see how it compares.... I've heard that those type of sensors can read a bit hotter than IR.... Generally though, if it makes good smoke doesn't lean bog off idle and sounds crisp it should be right.... Another thing you could try is increase head shimming... i read that it can make an engine run cooler
lowey79 is offline   Reply With Quote
Old 11-03-2008, 03:55 AM   #5
Tech Fanatic
 
itsshemp's Avatar
 
Join Date: Dec 2007
Location: Hemet Ca
Posts: 868
Trader Rating: 9 (100%+)
Default

You dont specify how long it takes for the engine to rev, then die, when doing the pinch test. To get me in the ballpark, i normally try to get about a count of 5-6 seconds from the time I pinch the line till the time it revs, then starts to die. If it wants to die instantly, then it is normally too lean on the LSN.

Some fuels seems to smoke more than others also. Its hard to say, but sounds like yours may be running too lean, or maybe the monitor is off?
__________________
Danny Flores
____________
Team Driver for:
Hot Bodies/HPI - Track Star Services - Triton R/C - Alpha Plus Engines - Radiopost - Hemet Competition Raceway (HCR) - Hemet R/C (R.I.P)
itsshemp is offline   Reply With Quote
Old 11-03-2008, 05:28 AM   #6
Tech Adept
 
Join Date: Jul 2008
Posts: 183
Default

I agree with ITSSHEMP.
joydude630 is offline   Reply With Quote
Old 11-03-2008, 07:41 AM   #7
Tech Master
 
Join Date: Jul 2006
Location: Sugar Land, TX
Posts: 1,169
Trader Rating: 9 (100%+)
Default

Richen the HSN until the engine bogs during high speed runs, then lean it a little at a time, run it, and get it just to the point where it doesn't bog at WOT. Then check the LSN like itsshemp said. If all that checks out, you know your tune is good and just outside of too rich. If the temps are still high, check it with an IR gun. The other thing could be that it's something completely unrelated to the tune. Bad bearing, gear mesh too tight, anything that puts drag on the car causes the engine to work harder than it should.
cjtamu is offline   Reply With Quote
Old 11-03-2008, 09:06 AM   #8
Tech Regular
 
LabRat99's Avatar
 
Join Date: Jan 2008
Posts: 406
Trader Rating: 1 (100%+)
Default

+1 to what cjtamu said....

I'd check the clutch bearings first, then diffs, then wheels.
LabRat99 is offline   Reply With Quote
Old 11-03-2008, 10:45 AM   #9
Tech Master
 
RBMike's Avatar
 
Join Date: Jan 2007
Location: Santa Clara CA
Posts: 1,264
Default

Also check to see that your drive train rolls freely. A bad bearing or other drag on the drive train can cause a properly tunned motor to run hot.
__________________
-EMBX6,T8 1400, RX8, 5S Lipo ,Elite-RC, RCM tray
-EMBX6,T8 1350, RX8, 5S Lipo ,Elite-RC, RCM tray
-B44 (Novak)
-ROAR 4 cell rule Blows
RBMike is offline   Reply With Quote
Old 11-03-2008, 01:44 PM   #10
Tech Regular
 
mini696's Avatar
 
Join Date: Mar 2004
Location: AUSTRALIA
Posts: 304
Default

Thanks guys heaps of things there for me to try.

I will check the bearings and drivetrain.

The gear mesh is good (I use the paper test and it comes out bumpy without cutting into the paper).

Doing the pinch test the engine raises revs a bit (maybe a bit too much) for about a 6 count (maybe more). Wouldn't the length of time depend on how far away from the carb you pinch too?

My thinking is that these engines just run hotter, and the guage is reading high. I remember having it on my .12 and that engine ran for a few gallons even though it seemed to have a high running temp.

Thanks once again guys you have given me heaps of things to go on with.

Last edited by mini696; 11-03-2008 at 01:54 PM.
mini696 is offline   Reply With Quote
Old 11-03-2008, 02:09 PM   #11
Tech Elite
 
jamminnay's Avatar
 
Join Date: Apr 2008
Location: IL
Posts: 2,012
Trader Rating: 10 (100%+)
Send a message via AIM to jamminnay Send a message via MSN to jamminnay
Default

how many gallons does the motor have on it?
jamminnay is offline   Reply With Quote
Old 11-03-2008, 02:14 PM   #12
Tech Adept
 
Join Date: Jun 2006
Posts: 125
Default

i used to use a temp gun for ever but found the temps to be to all over the place. just tune by feel.. if you are really concerned put a little spit on the head with your finger.. we all know that water boils a 230f.. if it is gone in an flash than you know its to hot if it stays there you know its under 230
Garrison is offline   Reply With Quote
Old 11-03-2008, 02:14 PM   #13
Tech Addict
 
Join Date: Apr 2007
Location: MEAKIN PARK,QLD,AUS
Posts: 741
Trader Rating: 24 (100%+)
Default

CHECK YOUR CLUTCH
meakinracer is offline   Reply With Quote
Old 11-03-2008, 02:18 PM   #14
Tech Elite
 
ezveedub's Avatar
 
Join Date: Aug 2004
Location: Fort Lauderdale, FL
Posts: 2,411
Trader Rating: 14 (100%+)
Send a message via AIM to ezveedub Send a message via Yahoo to ezveedub
Default

I find the Axe motors will run hot when the pinch is still tight. If it still locks up close to TDC, then it will run hot. I noticed this with my Mamba. It likes to run hot when new, but has since come down quite a bit on the temps. Any richer mixture, and it a pig. Temps will start to come down when the metal pinch goes away. On average, its about 2 gallons to get these motors to loosen up. At that point, change the rod and maybe throw a ceramic TKO rear bearing in. The rod takes a serious beating and I beleive thats why some state the rods snap after 2 gallons. Once you try to lay some RPM under them once broken-in, the rods give.
__________________
Kyosho, Mugen Seiki, Maxy's Fuel, KO Propo
O.S., Ninja JX, Novarossi, RMV
ezveedub is offline   Reply With Quote
Old 11-03-2008, 02:22 PM   #15
Tech Elite
 
jamminnay's Avatar
 
Join Date: Apr 2008
Location: IL
Posts: 2,012
Trader Rating: 10 (100%+)
Send a message via AIM to jamminnay Send a message via MSN to jamminnay
Default

Quote:
Originally Posted by ezveedub View Post
I find the Axe motors will run hot when the pinch is still tight. If it still locks up close to TDC, then it will run hot. I noticed this with my Mamba. It likes to run hot when new, but has since come down quite a bit on the temps. Any richer mixture, and it a pig. Temps will start to come down when the metal pinch goes away. On average, its about 2 gallons to get these motors to loosen up. At that point, change the rod and maybe throw a ceramic TKO rear bearing in. The rod takes a serious beating and I beleive thats why some state the rods snap after 2 gallons. Once you try to lay some RPM under them once broken-in, the rods give.

that is exactly what i was hinting at when i asked how many gallons it had on it..... ill bet it is pretty new
jamminnay is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 03:16 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net