Do I have an airleak?

[nitromad]

Hi there -

My mill consistantly runs pretty hot so I will try and give you as much info as I can so that you can tell me whether I most likely have an airleak, or that I'm just being paranoid...

Outside temp approx 52 Deg F
An STS .28 engine with factory shims
15% Nitro Fuel
Running on a dirt RC track which is quite tight and small (so I'm hardly WOT at all except on the small straight).
My running temp maxes out around 268 deg F
Lots of smoke under throttle.
Gear ratio - 16t clutchbell, ,44tooth spur gear.
Car: Kyosho Inferno mp7.5 buggy

I've done my best to seal the backplate with high temp RTV and also the carb, and have new fuel hosing. My tank passed the underwater 'bubble' test with no leaks.

I have it running very rich - lots of smoke and it even gurgles quite a bit off the line. It seems to get quite a lot cooler (230-40) when it moves and gets airflow, but idling the temp gets hot again. However if I richen the LSN, it stalls under throttle.

I'm thinking about taking it to a hobby store and seeing if they can do a better job of finding a leak than I have unless you guys think I do not need to bother??

Thanks

Chris

 

[jon2]

15% nitro? Think you may want use the standard 20% for cars/trucks.

 

[FastEddy]

You may have a leak but I think Jon2 may be on the right track. Try 20% and see if you get any better results. If you do, you may even want to try 30%. You SHOULD get the same performance running rich and bring the temps down.

You may want to try a different plug as well.

 

[jon2]

Just curious as to why you use a 16 tooth Clutchbell?

 

[nitromad]

Thanks for the replies...

Will running a higher nitro fuel actually bring DOWN running temps? I always thought that more nitro meant more more power and higher temps. If so, I will try 20% next time. I've been told that .28s are shimmed for 20-30% so maybe thats a possible problem?

What OS plug would you recommend?

I'm running a 16th bell for a couple of reasons - one is that if I get any more low down power, it will become almost impossible to keep in a straight line on the track and also because I just love top end speed on longer straights (although I don't go longer than 4-5 secs WOT in larger areas). Would coming down to a 13 or 14 t with a 46t spur make a difference to temps?

Thanks again

Chris

 

[HeartBreak]

Going two 2-3 teeth on the clutchbell will help out a bit with your temps, but like the others have said, try 20% nitro. You will have to "re" break it in when you switch percentages, if I'm not mistaken. Just a couple tanks slightly rich and on the easy side of the trigger.

 

[jetmechG550]

You'll just have to re-tune with the percentage switch. The higher nitro content will bring your temps down for sure.

 

[FastEddy]

You will have to "re" break it in when you switch percentages, if I'm not mistaken. Just a couple tanks slightly rich and on the easy side of the trigger.

Not entirely true. Like mentioned above you will need to possibly re-tune but a break-in procedure is not required. You can if you want but IMO its not required.

I would run for a bit at your current settings and take a look at the temps and power before fine tuning. Doing this will be a tell-tale if the % was your issue. 30% will need a closer eye to start off with.

Let us know what you find so we can add it to our pea-brains for the next person that has this issue.

 

[redhatman]

Another vote for higher fuel percentage. I run 20% in my STS .28 and it runs great. The more %, the higher the power and lower temps because its not striving for that extra lubrication it needs. However, I have heard rumors that fuel like 30% will cause shorter engine life. But then again, so will something like 15% from the always being lean.

 

[nitromad]

Thanks guys! Sold on the percentage. I'm heading to the track on Thursday and will run 20%, keep settings the same and hopefully will see an improvement. Will let you know,

Cheers

Chris

 

[nitro_freak_123]

as the other guys said higher nitro means more power and keep the temps done just do what has been suggested and when u do get the 20% nitro just do 3 tanks at base setting tha should do then u can tune then


good luck

 

[Monkey Wrench]

As for plugs, I suggest McCoy MC-59's. If you do decide to go with 30%, you MAY (and I stress MAY) want to consider going with a slightly colder plug (like MC-9). I run 30% with MC-59's in my Hyper .21 and haven't had any problems (unless a snapped servo arm in turn 1 of the first heat isn't considered a problem!)

 

[nitromad]

Thanks for the advice, I may have a problem getting McCoy plugs here as I haven't seen em at my nearby hobby stores. Which OS plug would you recommend? I currently run an A5. Cheers.

 

[nitro_freak_123]

UMM i wouldnt thought a5 will be fine for 30 % i think