Lol... Maybe you shouldn’t be so literal about a tongue and cheek title!
If I was seeking encouragement, moped army would be the last place I would look for it haha.
Clearly not everything is gonna work for everyone... this spark plug works for me and alotta other people.
Now let’s get some more moped related posts on this thread!
I tried a similar plug from Brisk, didn't work for shit. Bike hardly ran. This was on a nice strong CDI that had no problems at 13k+.
At the end of the day, if your spark plug makes your bike run better, you have some other root problem you should address (until at least you are making outrageous power, like 20hp from 50cc). For instance: I assumed that because my dumb self used a 1/2" reach plug in a head that needed 3/4" (e.g. B8HS vs B8ES), that was the cause of my lack of performance. I put the right plug in and performance improved a bit, but it's also clear I I still have other issues to sort out that are causing the bike to not achieve it's full potential - and this thread is about the difference in electrode setup, not about your plug being recessed way too far in a hole in the head.
So, good that you are excited about having made your moped better, fantasic, enjoy the feeling! But it's mopeds, not MotoGP, spark plug details are like the least important aspect of your engine's performance. In other words that plug ain't responsible for decreasing the heat that's going into your head - either it is causing less total effective advance, or it's causing you to lose power. But most likely it's just causing the temp reading to change without changing the actual heat that's going into your head... Most instrumentation merelt gives you a very non-direct, inferential estimation of the information you actually want to know, not a direct measurement of it.
My motor runs hot because I’m running full advance on my timing, it runs cooler when I retard it. Lots of steep hills where I live. This plug lets me run at Full advance while maintaining temps around 350-60 up steep hills, I’ve proved this many times over that the Heat rating of the spark plug does effect the head temps of the engine. I take it into account when tuning. NGK has different heat ratings by changing the center electrode length, B9hs vs B5hs.. the difference is definitely noticeable.
https://www.treatland.tv/NGK-spark-plug-BU8H-non-resistor-p/ngk-spark-plug-bu8h.htm
helpful reviews^crazy wayne approved, there is no arm on the plug end to get as hot compared to the standard design.
The bike runs great with a standard B6HS, just runs cooler with bu8h when running full advance.
Update: I installed the new compatible NGK boot with this BU8H plug and much cooler head temps, better throttle response and I get to my top speed at only 1/8 to 1/4 throttle. This plug rocks!
> Dan (high idle) Conway Wrote:
> -------------------------------------------------------
> My motor runs hot because I’m running full advance on my timing, it runs
> cooler when I retard it. Lots of steep hills where I live. This plug
> lets me run at Full advance while maintaining temps around 350-60 up
> steep hills, I’ve proved this many times over that the Heat rating of
> the spark plug does effect the head temps of the engine. I take it into
> account when tuning. NGK has different heat ratings by changing the
> center electrode length, B9hs vs B5hs.. the difference is definitely
> noticeable.
Spark plug temp =/= head temp.
Of course a more insulated plug doesn't get as hot. It doesn't mean your head is seeing less heat. The heat comes from the combustion, not the plug.
heat does get pulled out of the cc via the plug:
Another important task of the spark plug is transferring heat from the combustion chamber. Sparks plugs do not create heat, but they operate as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber and dissipating it to the engine cooling system.
https://cecas.clemson.edu/cvel/auto/actuators/spark-plugs.html
In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber.
https://www.wakularacing.net/index.php/tech-info/15-the-truth-about-spark-plugs
a more important question is whether or not we WANT to pull heat into the head or not...
> ken gilbert Wrote:
> -------------------------------------------------------
> heat does get pulled out of the cc via the plug:
>
> Another important task of the spark plug is transferring heat from the
> combustion chamber. Sparks plugs do not create heat, but they operate as
> a heat exchanger by pulling unwanted thermal energy away from the
> combustion chamber and dissipating it to the engine cooling system.
>
> https://cecas.clemson.edu/cvel/auto/actuators/spark-plugs.html
>
> In identical spark plug types, the difference from one heat range to the
> next is the ability to remove approximately 70°C to 100°C from the
> combustion chamber.
>
> https://www.wakularacing.net/index.php/tech-info/15-the-truth-about-spark-plugs
>
> a more important question is whether or not we WANT to pull heat into
> the head or not...
Yep^^, thats part of what they are designed to do. NGK has a whole article about this on their website.
Nice! ive been meaning to learn more about the Spark plug effecting running temps.
I tune with the coldest plug that will not cause low rev fouling, basically below 1/2 throttle tooling around for a hour then pull the plug and see the temperature as witnessed by the side electrode and accumulated soot (if any)
The cold plug will not transfer as much heat to the head, which makes a more robust and earlier hot medium in the expansion chamber. A robust and consistent expansion chamber heat will give you a better power band and pull at the top end of the rpm scale. Better to have the heat in the pipe working to over stuff the combustion chamber than to run a hotter plug and have detonation issues when it gets a glow on.
> ken gilbert Wrote:
> -------------------------------------------------------
> heat does get pulled out of the cc via the plug:
>
> Another important task of the spark plug is transferring heat from the
> combustion chamber. Sparks plugs do not create heat, but they operate as
> a heat exchanger by pulling unwanted thermal energy away from the
> combustion chamber and dissipating it to the engine cooling system.
>
> https://cecas.clemson.edu/cvel/auto/actuators/spark-plugs.html
>
> In identical spark plug types, the difference from one heat range to the
> next is the ability to remove approximately 70°C to 100°C from the
> combustion chamber.
>
> https://www.wakularacing.net/index.php/tech-info/15-the-truth-about-spark-plugs
>
> a more important question is whether or not we WANT to pull heat into
> the head or not...
> ken gilbert Wrote:
> -------------------------------------------------------
> heat does get pulled out of the cc via the plug:
>
> Another important task of the spark plug is transferring heat from the
> combustion chamber. Sparks plugs do not create heat, but they operate as
> a heat exchanger by pulling unwanted thermal energy away from the
> combustion chamber and dissipating it to the engine cooling system.
>
> https://cecas.clemson.edu/cvel/auto/actuators/spark-plugs.html
>
> In identical spark plug types, the difference from one heat range to the
> next is the ability to remove approximately 70°C to 100°C from the
> combustion chamber.
>
> https://www.wakularacing.net/index.php/tech-info/15-the-truth-about-spark-plugs
>
> a more important question is whether or not we WANT to pull heat into
> the head or not...
Per your links, spark plug heat ranges are about pulling heat out of the plug tip (heat that came from combustion) to avoid preignition. That bit about one step in heat range changing temp by 70-100deg is referring to plug nose/tip temp - not cylinder head temp.
Spark plugs are relatively small, have lower conductivity than aluminum, and are hotter than the surrounding cylinder head, so although they absorb heat from combustion, they don't pull heat out of the head. In fact, it's the head that pulls heat out of the plug... as shown in the picture in the second link:
So, if you're measuring with a ring under the plug, sure, a colder plug should give a lower temperature reading - but that doesn't necessarily mean less heat is going into the head. It gives that lower reading because the colder plug conducts the combustion heat into the head more effectively (and absorbs less heat from combustion due to its smaller exposed surface area). Yes, the plug ends up cooler, so you're safer from detonation, but that heat went right into the head.
So if you're timed too aggressively, a colder plug will help avoid deto, but it won't prevent overheating the head or piston, and it might hide the fact that you're doing that when you read head temp at the spark plug.
In any case, for OP: if you're going to claim this BU8H plug is superior for your application than conventional plugs, you have gotta do back-to-back testing. Put a B8HS in there (or whatever is the identical conventional plug) without changing anything else and see what happens. (edited)
Exhaust gas temp gauge is best
But 1/2 of a head temp gauge sensor does make contact to the head,
A cooler plug does help a little bit on air cooled two cycle engine on keeping temps and seizures down, sometime its only a few degrees less that keeps you from seizing so every little bit helps,
I run as hot as a plug as I can on kitted bikes some have 7 ngk some have 8,
Now Bosch spark plug numbers are backwards from NGK so #5 = #7, #4 = 8 in ngk, #6 on ngk does = #6 on Bosch though, orientating the plug electrode with shims could cool a few degrees also,
Bosch super plug was oem plug on many puchs and Italian bikes and is the best plug for stock/stock cylinder setups on most 1 and 2 speed Mopeds,
On stock cylinder magnum bikes I run #6 o r 7 Bosch plug and given the same heat range plug on ngk #6-#5 the Bosch plug goes 1-2 mi faster then ngk and can idle for an hour without fouling
The hot U Denso plug added one or two mph on a stock bike and don’t foul also,
And with a teeny tiny dremel bit I sometimes a mod the electrode on Bosch plug to match the U shape to match the Denso U shape electrode,
Shame the Bosch plugs are not available anymore unless you wanna buy a NOS one on fleece bay for like 10$,
Some people Side gap plugs but for me didn’t notice any gains, had poor performance and fouling,
It’s Fun to experiment with plugs you be surprised the gains you could get :)
Indeed if you are using a 'head temperature' gauge with the sensor at the union between the head and plug you are just reading that one location. If it is digital then there is always a sampling delay and you have to actually read the display.
Old school you would use a Exhause Temperature Gauge with the tip of the probe mounted so it is mid stream of the exhause near to where the divergent (diffuser) cone attaches to the header. Running the setup like that you can get the temperature of the medium inside the exhause expansion chamber. You want to tune to have this at around 1150-1250°F at wide open throttle and on the pipe. So you do not have to read the gauge you rotate it so that 1200°F is pointed straight up (actually all analog gauges should be rotated so optimum is straight up so you dont have to read them all)
You can get good self powered EGT gauges from ultralight folk or even eBay knock offs for 60$.
> Mikey Antonakakis Wrote:
> Per your links, spark plug heat ranges are about pulling heat out of the
> plug tip (heat that came from combustion) to avoid preignition. That bit
> about one step in heat range changing temp by 70-100deg is referring to
> plug nose/tip temp - not cylinder head temp.
>
> Spark plugs are relatively small, have lower conductivity than aluminum,
> and are hotter than the surrounding cylinder head, so although they
> absorb heat from combustion, they don't pull heat out of the head. In
> fact, it's the head that pulls heat out of the plug... as shown in the
> picture in the second link:
>
> https://www.wakularacing.net/images/TechData/chartheatratingflowpath.gif
>
> So, if you're measuring with a ring under the plug, sure, a colder plug
> should give a lower temperature reading - but that doesn't necessarily
> mean less heat is going into the head. It gives that lower reading
> because the colder plug conducts the combustion heat into the head more
> effectively (and absorbs less heat from combustion due to its smaller
> exposed surface area). Yes, the plug ends up cooler, so you're safer
> from detonation, but that heat went right into the head.
>
> So if you're timed too aggressively, a colder plug will help avoid deto,
> but it won't prevent overheating the head or piston, and it might hide
> the fact that you're doing that when you read head temp at the spark
> plug.
>
> In any case, for OP: if you're going to claim this BU8H plug is superior
> for your application than conventional plugs, you have gotta do
> back-to-back testing. Put a B8HS in there (or whatever is the identical
> conventional plug) without changing anything else and see what happens.
Yup RebelMoby, got EGT on the General build :)
> Rebel Moby Wrote:
> -------------------------------------------------------
> Indeed if you are using a 'head temperature' gauge with the sensor at
> the union between the head and plug you are just reading that one
> location. If it is digital then there is always a sampling delay and
> you have to actually read the display.
>
> Old school you would use a Exhause Temperature Gauge with the tip of the
> probe mounted so it is mid stream of the exhause near to where the
> divergent (diffuser) cone attaches to the header. Running the setup
> like that you can get the temperature of the medium inside the exhause
> expansion chamber. You want to tune to have this at around 1150-1250°F
> at wide open throttle and on the pipe. So you do not have to read the
> gauge you rotate it so that 1200°F is pointed straight up (actually all
> analog gauges should be rotated so optimum is straight up so you dont
> have to read them all)
>
Old-school everything was better, pistons better, gasoline had lead in it which made a great upper Cylinder lubricant (they still use leaded fuel for small airplanes to minimize seizures)
With these cheap pistons they put in these cheap kits nowadays it’s Best to tune to the lower 1,150 F temp on that ETG scale, (you can scratch cheap pistons with your fingernail), Aluminum melts at 1,221 and before melting temperature the piston expands and you seize!
Back in the day you could get a wiseco forged piston for your small bore, dirt bike, enduro bike and double and triple cylinder 2t street bikes (some you still can) so you could tune for more power because the forged pistons with leaded gas could take the heat better,
Which is why you want to retard the timing, so you can get the push from the expanding charge and get it the heck out of the combustion chamber before it starts to heat soak the chamber.
Still love bean oil for premixing, I prefer it to full synthetic just because of its heat transfer qualities and the loving slippery varnish it creates as it reaches its thermal limit.
> Overpriced Parts Wrote:
> -------------------------------------------------------
> Old-school everything was better, pistons better, gasoline had lead in
> n it which made a great upper Cylinder lubricant (they still use leaded
> fuel for small airplanes to minimize seizures)
>
> With these cheap pistons they put in these cheap kits nowadays it’s
> s Best to tune to the lower 1,150 F temp on that ETG scale, (you can
> scratch cheap pistons with your fingernail), Aluminum melts at 1,221 and
> before melting temperature the piston expands and you seize!
>
>
>
> Back in the day you could get a wiseco forged piston for your small
> bore, dirt bike, enduro bike and double and triple cylinder 2t street
> bikes (some you still can) so you could tune for more power because the
> forged pistons with leaded gas could take the heat better,
Turned out to be a good thread!
Just some more info:
I did back to back the BU8H with the B8HS yesterday. I went on my usual route, which includes a long incline over 2 miles with some good hills. At the top of the incline on a warmer night it hit 340 with the BU8H and 377 with B8HS. I know to check in the same spot when I come to a certain stop sign lol.
I’d say that’s a pretty fair difference with running 37 degrees hotter on the standard plug. Before it gets too cold out i’ll try to do a 10 mile run and swap plugs halfway.
>That bit
> about one step in heat range changing temp by 70-100deg is referring to
> plug nose/tip temp - not cylinder head temp.
actually I think it refers to cc temps.
> Spark plugs are relatively small, have lower conductivity than aluminum,
> and are hotter than the surrounding cylinder head, so although they
> absorb heat from combustion, they don't pull heat out of the head. In
> fact, it's the head that pulls heat out of the plug... as shown in the
> picture in the second link:
absolutely agreed. a colder plug will pull MORE btus into the head.
if the ground strap design isn't altered (as is the case here) then the increased conductivity of the 1 step colder plug will result in the 70-100* cc temp drop.
altering the plug shape/ design will throw those numbers off of course since the ability of the plug to absorb cc heat in the first place has changed.
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