Duckhunter63

Well I have a force 26 engine with a McCoy #8 glow plug, I have been running Traxxas Top fuel through the engine since break in, a gallon total. Today I burned up the rest of what I had and switched to Wildcat 20% nitro 18% oil. My buggy ran great with the Traxxas I put the Wildcat in and the car ran twice as strong however my problem is that it sounds really different and is reving really high at a stand still. The idle (once I get it to come down) sounds good and when I mash the throttle it sounds great, when I let go of the throttle it makes a high pitch high reving sound. It almost sounds like it isn't even coming up for the full stroke. Is this what preignition sounds like? I richend it up a bit and it still did it. Any help would be greatly appreciated..
Thanks,
Duck

nitroman88

My Feedback: (5)

my buggy does the same thing and i cant figure out why, when i let off the throttle it goes too a higher idle and then after about 30 seconds it will lower down to its normal. anyone have a clue why this is happening? I know that my low speed is set right because if i let it sit for about 40 seconds it loads up. is it set too rich?

Obsidian

my ears are open too.. my mach .26 does this in my storm. I cant figure out why. it gets to a higher rev but seems like it doesnt want to rev that high... almost like a high pitched gurgle

Duckhunter63

That is exactly what mine sounds like?? Hopefully help is on the way..
Duck

fourboltmain

OK,

I have seen a fix for this and believe it involves being just a little (just a little) fat at idle. Try leaning your LSN just a hair and see if you can get it to stay idling high and then re-set your idle screw. These engines are relatively unique in that fuel from the carb doesn't go right to the top of the piston, it goes to the crankcase. The crankcase has a relatively large volume, and as the leaner mixture (from running off the HSN) is used up in the crankcase, the richer mixture from the LSN starts to take over and makes it load up at idle. Because the crankcase is relatively large, it takes a little bit of time for this to happen. Make sense??

MassiveMods

your car will rev higher for a bit then settle because its burned all the built up fuel. it then revs at its set idle adgustment till it loads up again. what this means is your engine is acting like a dam . you let the water through by opening the throttle. you then let it fill up again. what this could mean and sounds to me is that your lsn is a little rich. try leaning your lsn 1/8th at a time. each time taking your car for a few laps to get the car used to the new setting. you may find when its tune right it will idle higher for longer. you will need to lower your idle in that case.

Preignition sounds like bacon cooking on a pan. your engine ideally should sound smothe and consistant. a great plug to use is the OS8 . it seems to be the one for many drivers.

all the difference betwen the lsn and hsn is that the hsn governs how much fuel goes into your carb and the lsn governt the amount that goes into the engine...

fourboltmain

Wow, we both just skinned the same cat !!

Duckhunter63

That is some good info and I will try it all, I am just puzzled that it had never done it before including about 2 mins before I switched fuel brands. That is the first time it has ever done it. I'll mess with it some more I guess and see what happens..
Thanks
Duck

nitroman88

My Feedback: (5)

its probably because you are using a fuel with more oil now.

Duckhunter63

The Traxxas Top Fuel was 18% oil as well.. I just don't know

raptorantill

My Feedback: (2)

Ok the Fuels issue goes that no mater what brand you put in look at the msds sheet it will have a flash point and f that changes then you vehicle will run diffrent. as long as the flash point in the fuel is the same it doesnt matter if you switch from avgas mistures with 2 cycle oil added to wildacat. The flash point on those two brands of fuel are diffrent. I personally run a jp-5 mixture with 2 cycle synthetic oil and sometimes it is omega it depends on what i can get here on midway. as long as the flash point is the same they run the same. they have to give the msds sheet when you purchase something or just on request.

fourboltmain

You run JP-5 in a 3.5 cc engine ??

RCaeroguy

My Feedback: (4)

Check your engine temperatures. My Force .26 did that until I made the body holes bigger.

fhm101

I think you have it kind of messed up here. The HSN regulates the total volume of fuel while the LSN regulates what gets in at idle only. Once the low speed taper is pulled out out of the spraybar, the LSN is no longer a part of the equation and the flow becomes regulated by the HSN.

Duckhunter63

I got the idle thing handled and taken care of, now I am running very high temps. I am set 5 turns from full seat and have never run this thing that rich. It still runs strong but it is hitting temps anywhere from 270-314, not good. I am going to check for airleaks along the backplate. I am using a duratrax flashpoint temp gauge with the emmisivity set on 77 (not quite sure if this is where it needs to be) I still use a little spit to confirm what the temp gauge says and it just jumps off the head like bacon frying..
Thanks for all the info guys,
Duck