ESE's works engine tuner

[TZ350]

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Looking at aero engines, Kobas BMW radial engine above and the cooling cowls on air cooled engines.

Gives me ideas for making a close finned head and ducting to improve the head and barrel cooling to get more sustained power from the GP125.

I have also seen a lot of ideas amoungst the aero engines that the FXR boys could use.

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[speedpro]

One of the ideas I would like to see (from a distance) you try is putting a really big propeller on the end of the crankshaft.

[TZ350]

One of the ideas I would like to see (from a distance) you try is putting a really big propeller on the end of the crankshaft.

Ok! I'v got it done. Don't say you didn't ask! and yes they are F4 complient and when I catch you the propeller is going to chew your arse! ...

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[TZ350]

A page scrape that talks about stopping detonation.

Note the bit where it says that the latest Yamaha road racer uses a copper head insert.
Was Thomas right or was Thomas right! whats more he thought of it first. Who's your daddy now.

Or at least we thought of it and implemented it before reading about Yamaha doing it. You can bet they used a dyno and explored all the options. There is some satisfaction in taking a thought out approach that goes against conventional wisdom and finding your were right.

Now we know! ceramic coating the combustion chamber is defiantly "not" the go! and as we came to suspect, only a sales gimmick like the "Port and Polish" for 4-strokes became. If you want high flow in a 4-stroke port, shape it and then sand blast the port walls. There is a reason why golf balls have a dimpled surface.

Coating the piston and exhaust port still has possibilities though.

The rest of the article can be read here:- http://www.factorypipe.com/t_deto.php


"Therefore the following will work; (to combat detonation)

(1) Lower intake temperature

(2) Lower throttle position, lower volumetric efficiency, or reduced turbo boost the less mixture that enters the cylinder, the less it is heated by compression.

(3) Lower intake pipe, crankcase, and/or cylinder, piston, or head temperatures. This year's Yamaha 250cc road race engine, for instance, has a copper cylinder head insert to conduct combustion heat away faster, resulting in a lower combustion chamber surface temperature.

(the operative words are "lower combustion chamber surface temperature" which is the thing you don't get with a ceramic coating)

(4) Lower compression ratio. The less you squeeze it, the less it is heated.

(5) A more breakdown resistant fuel, such as toluene or isooctane. If straight chain molecules are not present, the fuel will not be broken down so rapidly by preflame reactions.

(6) A negative catalyst something that will either pin down active radicals or convert them into something harmless. Tetraethyl lead, MMT, or other antiknock compounds are the medicine.

(7) Retarded timing shortens the time during which proknock reactions can take place.

(8) Incylinder turbulence or anything else that will speed up combustion (faster burning fuel such as benzene). This works by completing combustion before the time bomb of preflame reactions cooks long enough to cause autoignition.

(9) Higher engine rpm This simply shortens the time during which the mixture is held at high temp. In Honda experiments in the 1960's, they found that an engine's octane requirements began to decrease steadily over 12,000 rpm, and were under 60 octane up near 20,000. In a more accessible example, note that engines knock when they are "lugged" run at low rpm, wide open throttle and stop knocking promptly when you shift down a gear and let the engine rev up more. This stops deto by not allowing enough time for the reactions that cause it.

(10) Redesigning troublesome exhaust pipes. Some pipes give great numbers on the dyno, but can't be used because they cause seizures. They either simply overcharge the engine in some narrow rpm band (pushing it into detonation just as too much turbo boost would do), or back pump mixture from the header pipe that has picked up too much heat (this is why nobody heat wraps header pipes anymore).

(11) Avoiding excessive backpressure. Exhaust pipes always create back pressure, but the more there is, the higher the fraction of hot exhaust gas that will be unable to leave the cylinder during exhaust. Its heat, added to the fresh charge that next enters the cylinder, may push the engine over the line into detonation. Sometimes a one or two millimeter reduction in tailpipe ID will get you a couple of extra horsepower, but it may also push enough extra heat into the charge to make the engine detonate after a few seconds.

The number of ways of playing footsie with detonation is endless, but nothing works every time. This guarantees that we will never be bored, and will never run out of seized pistons."

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[Buckets4Me]

Those of us who began racing before water cooling arrived tend to think that engines get hotter the more we jet them down. With air cooling, this seems to be true, but isn't. The engine runs cool when it's rich because the extra fuel reduces peak flame temperature, and as we jet down towards chemically correct mixture, the engine runs hotter and hotter.

you run you engine leaner than mine just a thought

[TZ350]

Those of us who began racing before water cooling arrived tend to think that engines get hotter the more we jet them down. With air cooling, this seems to be true, but isn't. The engine runs cool when it's rich because the extra fuel reduces peak flame temperature, and as we jet down towards chemically correct mixture, the engine runs hotter and hotter.

you run you engine leaner than mine just a thought

More from the same article

Now we know, from our experiences with water-cooled engines, that power, engine temperature, and exhaust gas temperature all rise as we jet down until we go beyond chemically correct mixture. When we do, power, engine temperature, and exhaust gas temperature all begin to fall again. We couldn't see this before, with air-cooling, because the power we were making was overwhelming the engine's cooling ability. But it makes perfect sense because heat release in combustion depends upon finding enough oxygen so that each and every hydrogen and carbon in the fuel is completely reacted to form water and carbon dioxide. Any fuel left over is potential chemical energy unreleased which is why running lean makes less power. On a well cooled engine that is not detonating, you can jet down until it starts to slow down.

http://www.factorypipe.com/t_deto.php

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[Rick 52]

Great work fellas you must be pleased to hear that Yamaha used the copper gaskets it shows you are on the same thinking scale .

[Buckets4Me]

Great work fellas you must be pleased to hear that Yamaha used the copper gaskets it shows you are on the same thinking scale .

Yamaha TZ350 where did it all start I wonder
i remember a t250 suzuki with yahama barrels on it lol
and the biggest drilled disks a 5 yearold had ever seen

[bucketracer]

So you and F5 Dave were right, Ceramic Coating the combustion chamber is counter productive.

Interesting to see that a 2-stroke can be tuned up with porting etc and then need to be de-tuned with a rich mixture so that the waste heat from the extra power does not overwhelm the cooling system.

Not much point in porting/chamber for extra power in an air cooled engine, better to go for wider power band.

[F5 Dave]

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

[F5 Dave]

. . .

Not much point in porting/chamber for extra power in an air cooled engine, better to go for wider power band.

not messy celery.
You can still drastically improve the BMEP of a roadbike/farmbike engine Buckets are generally made from, but yes there is a tradeoff that; high revs, high compression, peaky power, are all counter productive after a point of compromise. But that is why the rules allow an extra 25% capacity which is quite generous. Hence the carb size i guess.

[bucketracer]

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

Not sure they are talking about detonation ring which is usualy made from brase, it specificaly talks about the copper chamber inserts job is to reduce combustion chamber surface temperature.

[F5 Dave]

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

[bucketracer]

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

These are brass detonation rings. Brass has a low thermal conductivity compared to copper or alloy but has a high wear resistance to the erosive effect of detonation. I am not sure the copper insert that TZ's artical talks about is a brass detonation ring but something more to do with improved combustion chamber surface cooling using a copper insert for the combustion chamber itself.

All the detonation rings I have seen were made of brass not copper, never seen a copper one.

As F5 says, a pic would be good.

[Kickaha]

Detontation rings I have seen fitted to TZs were machined in the top of the barrel like pic 1 but that wasn't a factory Yamaha thing, the later unleaded TZ the whole chamber seemed to be done like that one in the picture