D_o_S

Hi,

I have a LST2 with a Mach 427 engine. It is now 10 C (50 F) outside, and I would like to go and run my truck. I will run 25% nitro.

I have a Novarossi 8 plug in it now. I went to a hobby store, and I bought some plugs... however, I got the "S" version, which is like "Super" or something... I have both C6S and C7S... and I don't know which one I should run...

Any help greatly appreciated

cdelong

iTrader: (12)

If you are just bashing around I would run the #7.

A #6 is a hotter plug and unless you are sure your engine is shimmed properly you may cause damage with a #6... unlikely but possible.

With a properly shimmed engine a #6 would be fine @ 50F. I believe it's recommended to run a #6 in temps less than 60F although I've never had issues with a #7 running in temps as low as 50F on cold mornings at the races.

The #7 is a safe bet

Dredd

From novarossi Website

C4S - "Special" hot glow plug
engines from 3.5 to 10 cc

C5S - "Special" medium glow plug
engines from 3.5 to 10 cc

C6S - "Special" cold glow plug
engines from 3.5 to 10 cc 25% nitro

C7S - "Special" cold glow plug
engines from 3.5 to 15 cc over 25% nitro

C8S - "Special" extra cold glow plug
For engines 3.5 to 15cc running on more than 25% nitro

so basically higher number = colder plug which is acceptable for more nitro. I'd try the 6 first since you're running 25% and it's what I run in my engine with 20% See how that works. The tune may need to be adjusted slightly. I had a #6 in there and then swapped to a C6S and it idles much higher and stronger (hotter plug I think).

D_o_S

Thanks for the replies,

Ok,

I was outside just now, and decided to start my LST2 for the first time after its long winter break...

For winter, I literally flooded the engine with ARO... so it logically took a while for me to flood it all out... Then, I thought I had problems with fuel getting to the engine... I don't use the primer, but I plug the exhaust, and use the roto to crank the engine... I did that a few times, and no go. I however began to smell the scent of burnt nitro . Convinced that I've got problems with fuel delivery, I fetched a can of compressed air, and blew it down the exhaust pipe (I know, I could have blown, but one never knows what they put in today's fuels, and I don't want to go blind/die). I blew 2 short bursts, and inserted the roto wand... and it snapped out of my hand. From previous experience, I knew that this meant the engine was flooded... so I took out the glow plug, spun the engine over, put in the plug, and primed the engine. It flooded again. Again same procedure, again I managed to flood it. Now, I was sure that fuel was getting to the engine, so I just primed it via the exhaust. I also changed all the plugs I have around (from the original A3, to the Novarossi 6 (it was a 6 that I had, not an 8-oops ), then to the C6 "Super", and also I tried the C 7 Super)). Anyhow, I inserted the roto, glow ignitor, and "pop" it went, but only ran for like 1 second. I fiddled around with the needles, and also opened up the idle gap... got it running Gee, I was so happy Ran it for like half a tank, and since we have a new lawn (or something, my dad put some special soil on it or something, and I didn't want to destroy all that) I plugged the exhaust, returned the piston to BDC, and decided to call it a day.

I however do have a question... it was ~14 C outside, and the engine got up to 90 C... does that sound ok?

Thanks.

Dredd

90c is very very very cold for a nitro motor

So yes I would say that is ok if the engine was performing well and didn't feel like it was bogging or in any way struggling. I lean my motor out to around 120c (about 250F). I don't tune based on temps, but what I do is lean it out on the high end 1 hour at a time until I notice no performance increase or the engine wants to stall at WOT (wide open throttle). Then I richen from there about 1-1.5 hours. From that point I run a few high speed passes at WOT or on the track a few laps and bring it in and check temps. I just try to keep it from running any more than 280F which is about 137c. I never touch the low end needle if the engine starts and does not seem to have trouble at idle and does not bog when the throttle is opened less than 1/2.

Once I have the engine initially tuned I almost never really touch it. I only lean it out 1hour on days colder than the ititial day I tuned it. Or on a day hotter than the day I initially tuned I would richen it up 1hour. Then check temps after a few passes/laps and make sure it's getting good temps. Then I will tune for the next day of running based on that day's conditions. This makes it easier than having to totally retune each time (for me). Some guys like to take it back up to break in settings to get started then slowly lean down until they get to a comfortable performance and temp level for the day.

Also some guys will lean out a motor to 300F (148c) and think nothing of it. Personally I like to be on the safer side of things and stay under 280F (137c or so). This prevents me from going overlean on the engine and burning it up faster. I do not have the money to spend on new engines alot so I'm pretty careful.

cdelong

iTrader: (12)

A common tuning mis-conception by a lot of people.

On hotter days you need to lean your engine because there is less oxygen molecules per cubic ft. of air. Many people think you need to richen the engine on hotter days to cool it more.... if you do, it will run like crap. You just have to balance your comfort level with temperatures as to how far you lean it on a hotter day. Maybe you'd also run a #8 on a hotter day or shim the head 0.1mm. If you richen a .21 on a hotter day I almost guarantee you hit second gear way late or not at all because the engine is way too fat and not making enough power to engage the two speed.

Colder days are just the opposite.... more oxygen molecules per cubic ft. of air, hence you'd need to richen the engine and possibly run a #6 plug (if you were running a #7).

You give the engine what it wants when the weather changes and kinda just live with the temperatures

Dredd

my engine never runs like crap...

because of my method mentioned above. Use the settings from previous day for a base to start at. Then I go from there

cdelong

iTrader: (12)

my point is that you can't just say..... richen the engine when it's hotter out.

that does not work except if you are just tuning for temperature and not performance. An aspirated engine- be it two or four stroke is designed to run at a narrow range of air fuel mixture for optimal performance. Tell me how richening your engine when it's hot accomplishes this? It doesn't

For example: a normally aspirated engine (which we have here) needs around 12 or 14:1 air(oxygen)/fuel mixture. If there is less air (oxygen) when it's hot, the engine needs less fuel to run optimally (performance wise). I'm not saying it won't run.... it just won't run optimally.

On an average race day you run rich in the morning when it's cold and leaner in the afternoon when it's hotter. By the time the mains roll around it's time to richen them up again as the sun is setting.

If you don't understand that I can't help you any farther.... it's simple physics

Dredd

you make it too damn hard...it's simple my way and works. Use a good baseline and go from there. It's alot easier to have some base settings to start from, leaning out from there until the desired performance is reached.

It's not rocket science at all, as much as people like to make it seem. It's quite simple and doesn't require a complicated formula to figure it out.

What you'll have if you simply tell ppl to run leaner when it's hot is people closing off their carb then complaining about pitiful performance or an overheating engine. It is ALWAYS safer to go more toward the rich side rather than the lean. When in doubt go a bit richer and work from there. The only reason I lean a bit on cold days is because I find my engine to run poorly when not up to temp so I induce higher temps with a slightly leaner mixture. 1hour is very very small adjustments, almost hardle turning the needle. I'm not telling people to do full turns.

If you don't like the way I or anyone does it, don't use it. He was asking for temp info and I was still correct, 90c is pretty cold but if performance was good it's ok as each engine is different and temps are a pretty hard way to tune a small engine.

kyosho 444

here are some plugs on the chart