Engine Temperature

[johnnysherco]

hey TrialsRfun

Regarding 2T v 4T running hotter.

The reason in my opinion is the fact that the 4T has the best induction and compression stroke and more compression giving a better burn of your fuel and hence more heat, due to a more efficent engine design.

Why waste fuel out the exhaust port when you can burn it and get more power in a 4T engine.

My Sherco 4T is running great and pulls like nothing else and is great to ride not to mention the extra grip a 4T gives you over the 2t.

In regards to the oil system in the Sherco 4T why complicate it more with an oil pump and as most people in this forum have forgotten if you have an oil pump which is a positive displacement pump you also need an oil pressure relief valve and as a after thought if you have oil pressure what happens if you spring a leak on the oil pressure side of the pump !!!!

As the man said keep it simple service man.

johnnysherco

[trialsrfun]

Did any one else read the article about Mick Grants bikes in the Trialsworld mag. Apparently the Cub is lubricated from the gearbox and there aint much in there, and the Ariel carries only half its oil capacity to save weight.

Both interesting bikes with titanium exhausts made from scrap expansion boxes from racers.

[chris]

To design new cases, and make the tooling needed to produce them would be very very costly............hence the somewhat dubious lack of a pressure feed oil system on these bikes.

Altho the cases are similer to look at they are different so new tooling would have been needed anyway.

[johnnysherco]

The main reason Sherco doesnt have an oil pump, is that it would be impossible to incorporate a pressure fed lubrication system, within crankcases originally designed for a 2 stroke engine.

To design new cases, and make the tooling needed to produce them would be very very costly............hence the somewhat dubious lack of a pressure feed oil system on these bikes.

Hey Honda RS

For a bike with a somewhat dubious lack of a pressure feed oil system, my 4T is running just great. Starts second kick every morning and first kick when hot. It does not use any oil and does not blow smoke like the 2 stroke bikes, and I will say it again it sounds fantastic. As far as servicing well I change my oil like the 2T people!!!!!!!

I noticed that Cabastany had no problems riding the bike or kick starting it

Cheers

johnnysherco

[atomant]

I noticed that Cabastany had no problems riding the bike or kick starting it

Gotta agree with yer there mate.

Caby rides that bike like he was born on it..

[scorpa3]

Another 'cooling' theory to consider.

An internal combustion engine is partly cooled by the incoming air/fuel mixture. 2t's receive fuel every stroke whereas, 4t's only receive the mixture every other stroke. Hence a greater cooling effect.

[the artist formerly known as ish]

So to try and answer this question we did a test at our club trial today.

Using an hand held non-contact laser thermometer, at section 5 of a three loop ten section trial.

The first loop was not recorded because riders took time to walk the sections and the bike often cooled down.

A point on the motor, half an inch below the cylinder head gasket was the point used to record the temp on all bikes, and the thermometer has an error range of + or - 2 deg either way.

I'm not going to post every single recording just the highest and lowest recording of each machine the average reading is inbetween , I was riding the event and the observer recorded the values when he punched the riders score card.

The Sherco and Scorpa 4t's only had one bike each to record the values, all the other models had more than one.

Ambient temp was 85 deg F app 30c all results are in Farenheit.

Scorpa 125. low 219 high 247 avg 233

GG TXT 321 low 161 high 167 avg 164

GG PRO low 162 high 168 avg 165

Mont 4rt low 145 high 160 avg 152.5

Sherco 4T low 152 high 160 avg 156

We also recorded the header pipe temp at the same time and found those with crome pipes gave a false reading due to the reflection, but the lowest good reading taken on none cromed pipes reading was 255 and the highest was 600

[trialsurfer]

Another "Theory" shot in the ar$e!!

[downunder]

If this was an election I'd demand a recount

Interesting results.......maybe same idea with a sound level meter would answer the "it's too loud" question too.

Nice job.

BJDownunder

[feetupfun]

A point on the motor, half an inch below the cylinder head gasket was the point used to record the temp on all bikes, and the thermometer has an error range of + or - 2 deg either way.

<{POST_SNAPBACK}>

Ishy what I see in your results is that:

The outside temperature of an air cooled (4 stroke) motor is generally hotter than the outside of many water cooled (2 and 4 stroke) motors

The water cooled motors had narrower operating temperature ranges than the air cooled motor (ie their thermostatic control systems were working)

Both are totally expected results

I would also expect that:

If you tested an air cooled 2 stroke motor under the same conditions you would get a result similar to the Scorpa 125.

If the ambient conditions of the test were very cold or very hot instead of the 30 degrees C, the benefits of water cooling would be even more apparent ie the water cooled bikes would have the same operating temperature range as for 30 degrees but the air cooled bikes would be correspondingly hotter in hotter weather and colder in colder conditions and would continue to see a wide temperature range at any given ambient conditions.

BTW I'm assuming you did the testing in conditions considered hot in most of the trials riding world. In most of Australia the normal summertime day temperature is well above 30 degrees C. Where I live it is usually 33 in summer and 27 in winter. Further North and away from the coast summer days are normally around 43 degrees. This why I am an advocate of thermostatically controlled water cooled trials bikes be they 2 or 4 stroke.

[the artist formerly known as ish]

I agree with you all the results show is the head temp of the four stroke and the two stroke water cooled bikes are close to the same, the topic is why do 4s run hotter.

The one area that is hotter on the four stroke is the header pipe, I don't know if this is because the pipe is smaller in diamiter or what, but with temps getting up to 600 deg F, I would be looking at ceramic coatings to get better exhaust flow.

The Sherco 4T exhaust high temp was 360 deg, it has also a larger diameter than the Mont, but I don't know if it is single or double walled.

Someone is sending me a ceramic header pipe for a Mont so we can test that.

Also a mate of mine has his truck header pipes coated localy and claims they drop the temp of the pipe over 110 deg, we will see, if it works I will get my header pipe coated, if it only means saving melting my wellies

[downunder]

Ishy

Downunder we have a lot of cars that run on LPG or petrol (dual fuel) At one time I left the temp gauge sender (capillary type) sitting on one of the exhaust manifolds of my V8 pick up and drove it for weeks. I know this is not very scientific but..........when the motor was running on LPG the manifold temp was much lower than when on petrol (LPG also reduces power output by about 15%). I can't remember the difference but it was significant. The point is, the type of fuel, octane content or maybe even premix 2t fuel might have an impact on exhaust temps

But good luck it is interesting reading.

BJDownunder

[howard wallace]

Basically. The four stroke burns it fuel charge more efficiently, and thus a hotter exhaust gas entering the header pipe.

The two stroke is not as an efficient burner of its charge, but does it twice as often, and has a large amount of unburnt charge exit into the header pipe. This is where exhaust are crucial on two strokes. Expansion chambers are critical for pushing that charge back into the cylinder with positive and scavenging with negative pressure waves.

To the point where a customer 2T, had a leaking header pipe gasket, this was letting fresh air into the header, causing it to re-ignite the exhaust charge. It got that hot the header went blue and the plastic guard on the muffler melted.

The Sherco runs a very light gauge,single wall, stainless header.

The light gauge saves weight, but the stainless retains heat, can`t have it all. But best of all it doesn`t rust.

Ishy, measuring the header temp is the best way to tune, and diagnose an engine. A V8 with a temp sensor in each header ,on a dyno, will tell you the perfect mixture, and if any cylinders are lazy.I`ll stop there cause that`s another interest of mine.Comes with Pickups, big blocks, and blowers.

Well, left myself open for some comments now, though it has been peaceful round here lately.

Edited August 24, 2005 by Howard Wallace

[downunder]

Howard

When I used to build headers we used engine heat to dictate pipe length for tuning. When you run the engine at the desired rev range (what it was cammed and tuned to) the pipes get blue spots (mild steel exhaust tubing). Then we cut the pipes at that length and that was where the collectors went. It truely was "tuned headers". Trouble was if you changed cam it all went out the window. Slightly off topic but it does show how heat varies along the exhaust depending on engine tune and revs.

BJDownunder

[feetupfun]

Someone is sending me a ceramic header pipe for a Mont so we can test that.

Also a mate of mine has his truck header pipes coated localy and claims they drop the temp of the pipe over 110 deg, we will see, if it works I will get my header pipe coated, if it only means saving melting my wellies 

<{POST_SNAPBACK}>

Apart from reduced risk of melting ones wellies, can someone explain why reducing the temperature of the outside of the exhaust pipe on a 4 stroke is important?

I would have thought that cooling the exhaust gas as quickly as possible to reduce its volume (by dissipating heat through the wall of the exhaust pipe) would mean the exhaust system could be made smaller diameter than if the exhaust gases were kept hot by coating the header with an insulator.

Advocates of ceramic coated headers on trials bikes please share the reasons for doing it.

By the way I'm not asking about turbocharged diesel truck headers because they are coated to keep as much heat (energy) in the exhaust gas as possible between the head and the turbo.