LCGB Forums

Direct cooling with big square head v standard head -- fins on the flywheel and cowlings on a tuned ts , what's your thoughts,

Tootling along at 60+ on the motorways large head and no cowling will probably run cooler than with the cowlings on.........go through a town, get stuck in traffic and stop/start and the cowlings will be cooler.

the cowlings are tried and tested.......takes yur chance without them

With an Avanti head and cowlings you've probably got the perfect combination

MickYork wrote:Tootling along at 60+ on the motorways large head and no cowling will probably run cooler than with the cowlings on.........go through a town, get stuck in traffic and stop/start and the cowlings will be cooler.

the cowlings are tried and tested.......takes yur chance without them

With an Avanti head and cowlings you've probably got the perfect combination

+1

I remember only too well taking a newly built engine for a test spin with no cowlings. I should have known better. Got about 5 miles from home, turned round and got stuck in traffic and revs started to build and then the whole thing went ballistic as it overheated and revved itself senseless.
As above: stay with the cowlings.

There is a major difference between what speeds you can maintain on the road versus the track, thus maintaining air flow over the engine. Remember, things like toolboxes, even fuel filler flaps along with the choice of seat all contribute to enable heat to get out, as much as cooling air get in!

Plus one other massive factor.

Despite it not releasing as much power, Avgas makes an air cooled engine run nowhere near as hot as when using super unleaded.

Just as a matter of interest, has anyone done any research into the pros and cons of running an engine with or without cowlings? Just thinking that no cowlings means you can loose the fan and thus save on rotating mass (inertia) as well as saving the power lost due to the wind resistance of the fan...BUT, is that greater or less than the wind resistance caused by a feckin big scoop hanging down in the slipstream? One for the racers

I recon The drag on the fly wheel fan is fOOKIN massive.
Ever used a cycle Turbo trainer, a set of rollers with a little fan.
Don't sprinters remove the cooling fins from front and rear hubs for that reason.

A fly wheel with a fan that's engaged by a simple clutch would give big gains.

As far as I am aware, there has been no research.

However, even with a relatively small scoop, the air volume available is massive. Remember, it's just being 'redirected' & in terms of significance when you consider the aerodynamic properties of a full frame Lambretta comparing favourably with a house brick, probably no worse than a stand plate, say.

I wasted my time producing an electric fan driven cowling to augment a scoop but I wouldn't say it was of benefit for racing. Likely more useable by a stop/start type bike.

Research to be effective has to be thorough & unbiased. For example, there has been none, to my knowledge, on the subject of front brakes, internal disc versus external. Charlie Edmonds was still using the former when he raced & Guy Topper would outbrake him. But look @ the dynamics of a very tall CE on a full frame Group Four versus a tall, skinny GT on a tiny Group Six & you might consider all the factors that come into play.

Agree regards research,
But in the absense of research we are left with the laws of physics.
And proven development in other areas of automotive industry.
It's not for nothing that the cars now days no longer use a power sapping belt driven rad fan.

It's not for nothing that the cars now days no longer use a power sapping belt driven rad fan.

No, they tend not to. Power steering pumps, air con pumps in addition to coolant pumps may have made up for any gains!

The technology is available for engines with no coolant (VW Ceramic) & to make two strokes more efficient, as they are in ships, the most efficient, commercially, in the world (two stroke supercharged diesel). How far can Joe Public push the boundaries?

Good Luck with your research. Just remember comparisons are not as they often appear, factoring in the Avgas versus pump fuel.

Just to let you know I spoke to charlie regarding his inboard disc. There was a lot more to it than meets the eye. I started racing this year with a inboard disc thinking if charlie can do it with an inboard then so can I. 2nd race with sintered pads drilled and grooved disc I cooked it. The 1st thing I did after the meeting was get in touch with charlie to see how he managed with his inboard. Let's just say I was quoted a hell of a lot of money to replicate it. He even suggested to go outboard unless I really cared that much about how my race bike looked in terms of originality.

I hope this is not to far off topic (sorry).

I run a direct air cooled large MB head and a finless flywheel.

My CHT runs considerably cooler now than the previous cowled set up.
No problems related to heat over the past 2 years which have included 1000's of miles inc motorway, town riding,blast round the race track at Cobblesoul and queing in the traffic at the Dartford crossing on a hot day going to Mersea island.

Its proved to be quick and reliable and I know of 5 others that have the same head fitted or ready to fit. im happy with it.

Just to let you know I spoke to charlie regarding his inboard disc. There was a lot more to it than meets the eye. I started racing this year with a inboard disc thinking if charlie can do it with an inboard then so can I. 2nd race with sintered pads drilled and grooved disc I cooked it. The 1st thing I did after the meeting was get in touch with charlie to see how he managed with his inboard. Let's just say I was quoted a hell of a lot of money to replicate it. He even suggested to go outboard unless I really cared that much about how my race bike looked in terms of originality.

I am aware that his disc brake set up was well documented in Scootering magazine many years ago.

I am not advocating that internal should be used & is better than external. I was using the example as so often people state that external brakes are better than internal as a matter of fact, without taking everything into account. Do you understand that? That's why I selected that particular example to show any reader that the comparison is not 'like for like'

With your own attempt, did you use the best brake fluid available, such as Castrol SRF, expensive @ about £50 per litre? What slave cylinder did you have, or whose manufacture? What is your master cylinder diameter? They are all factors that have to be considered through bitter experience.

I can vouch for this though. I have witnessed many people struggling to get their external disc to operate correctly.

I run a direct air cooled large MB head and a finless flywheel.

My CHT runs considerably cooler now than the previous cowled set up.
No problems related to heat over the past 2 years which have included 1000's of miles inc motorway, town riding,blast round the race track at Cobblesoul and queing in the traffic at the Dartford crossing on a hot day going to Mersea island.

Its proved to be quick and reliable and I know of 5 others that have the same head fitted or ready to fit. im happy with it.

Funny thing is, so do I.....on the track.

I might consider ditching fan cooling for a road bike if it wasn't to be used on a Rapido/GT/Cast Iron barrel but even then, not with a stand plate, nor some kind of proof it would be of benefit. If you are running a bike with a cast iron barrel of any kind with a reasonable bore clearance, a bleed on your exhaust of less than Ø1", a full standplate, toolbox in place (or extra large tank), fully panelled & floorboarded, heavilly laden with two average size rally going scooterists & luggage, then that is remarkable!



This Forum exists for healthy debate & has a varying cross section of readers with different particular interests ascociated with the finest scooter in the World. Personaly, I love innovation, but I am also the kind of person that has f*cked up many times pioneering. So, if I sound a note of caution, please don't take it as p#ss#ing on your chips!

What s your cht and egt readings loz

My sensor is 100mm from exhaust stub and reads 650 - 700 c on a sky line gauge , cht is under plug and reads 200 c also a sky line gauge ,

My sensor is 100mm from exhaust stub and reads 650 - 700 c on a sky line gauge , cht is under plug and reads 200 c also a sky line gauge ,

200 is high!

...as is 700°C EGT even in racing.

What temperature would you be looking to run at as a safe guide .?

550C is safe, I wouldn't want to see much above 600C if I was using an EGT.

Thanks very much for sensible answers , I know what I'm looking for now, bike has been booked in today to have head re profiled after wooly, cheers ,

My cht guage is under the plug, I don't run an egt. The scoot was built 15 years ago before such things were thought about..a VW under plug cht gauge was cutting edge
Under load with cowlings it would hit 250...it peaked at 150 using the big head.

Im not convinced that the readings are at all accurate temperature wise, BUT, the same gauge , same scoot, same mounting point the needle moves hardly at all now the big head is used.