Hi all, please be kind :-) I’ve read a lot and tried a few things… I come from running OS Nitro Heli Engines and they are so simple. Run in is as per manual then set needles and forget, perhaps a couple of clicks one way or another from depths of winter to highs of summer.

Ive had a few cars and even a bike, and while I’ve had some success running and tuning I feel like it’s always a coin toss as to wether the car will start.

I always thought - due to my helis - that more nitro % simply meant richer settings. The minimum % I run in helis is 20 and max is 30%.

One of my most successful nitros was a Losi RTR 8ight buggy that ran well with 25% nitro and the stock plug which I believe was a medium plug I think that was a .21. However when running the ubiquitous Thunder Tiger .15pro or their .12bk or the HPI .15 NITRO star I find I need lower nitro % - 16% - and a hot glow plug. But I also find myself tweaking needles each day and it’s not to get 100% out of the engine it’s just to run it, indeed I prefer to run on the rich side.

So I guess the $1mill is …. Is there a clear guide for engine size, nitro % and which glow plug to use? If you run a Heli with an engine, I’ve got you covered, but what’s the answer for cars?

It is all about the ignition timing
R/C Tech Forums - View Single Post - How do you adjust engine timing on nitro engines?

With this knowledge there is no universal list of what size engine using what headplay and what amount of headshims

Basically all RTR engines use a plug in the same range, all ,12 racing engines use a plug in a same range, all .21 offroad competition engines use a plug in a same range and all onroad .21 competition engines use a plug in a same range.

And yes, basically this counts for any glowplug engine. How lower the compression the warmer glowplug you have to use but as a side effect, the wider range of nitro percentage you can use. With higher compression engines using cold plugs that range is more tight and critical

Thank you for the link and the details. I’ve not heard of the link between compression and glow plug heat/nitro % before so thank you for the insight.

These engines run on a self ignition and the ignition timing is set by plug heat, nitrocontent, compression and in a small way the weather

Been thinking about this a bit, would I be correct that for an older engine with lower compression a hotter plug would keep it running assuming same Nitro %?

Low compression and warm plug will give about a same ignition timing as a high compression and a cold plug so yes. Keep in mind the torque is better with a high compression. But why do you want to lower the compression to use hotter plugs?

I was thinking more for an older engine so you can get as much running out of a worn piston / liner as possible.

A worn piston gives a compression leak, you can compensate that with a higher compression (if i is possible with removing 0.1mm headshim. Or you can use a warmer plug w/o changing compression. But basically if the engine runs fine with the original configuration then there is no need to make changes